Exam 3 Study Guide Questions
What roles do activated cytotoxic T cells play, and what types of cells do they target? What roles do perforins, granzymes, and apoptosis play in cytotoxic T-cell activities?
- Perforins (damage target cell membrane) and granzymes (attack target cell proteins) are secreted, and apoptosis (programmed cell death) is induced in the target cell
What antibiotic is typically given if meningococcal meningitis is suspected?
-Meningococcal conjugate vaccines (Menactra®, MenHibrix® and Menveo®) -Meningococcal polysaccharide vaccine (Menomune®) -Serogroup B meningococcal vaccines (Bexsero® and Trumenba®)
What are four major genera that are components of the normal skin microbiota? For each of these covered in class: are they Gram positive or negative, to which phylum do they belong, what is their relationship to oxygen, and what is an example of each that is pathogenic?
-Streptococcus (Phylum Firmicutes; Gram +) Aerotolerant anaerobe ("lactic acid bacteria") Homofermentative - lactic acid as sole product Genus includes the pathogens S. pneumoniae, S. pyogenes -Propionibacterium (Phylum Actinobacteria; Gram +) Facultative or aerotolerant anaerobes Live in follicles, pores; ferment sebum, acids, carbs P. acnes is implicated in acne -Staphylococcus (Phylum Firmicutes; Gram +) Facultative anaerobe (fermentation) Commensals (S. epidermidis) and pathogens (S. aureus) -Corynebacterium (Actinobacteria; Gram +) Obligately aerobic or facultatively anaerobic Includes the pathogen C. diphtheriae, cause of diptheria
What are the four principle stages of immunological development and interaction?
1)T and B lymphocyte development and differentiation 2)Presentation of antigens 3)Challenge of B- and T-cells by antigens 4)Lymphocyte responses: a. T-cell response: cell-mediated immunity i. Help activate B cells ii. Destroy infected and irregular host cells iii. Help regulate immune response b. B-cell response: production and activities of antibodies (humoral immunity) i. Secrete antibodies
What are the four stages of development of the malaria parasite? Which stages occur in the human host, and which occur in the mosquito vector? Which of these stages is responsible for the "cyclic" symptoms of the disease?
1.Infection: Female Anopheles mosquito injects Plasmodium sporozoites into the blood of a human host 2.Pre-erythrocytic phase in the liver. a. Sporozoites travel through the blood to the liver and infect liver cells. b. Sporozoites undergo asexual division (schizogony). c. Infected liver cells erupt, releasing merozoites. 3.Erythrocytic phase in red blood cells (produces symptoms in host) d. Merozoites infect red blood cells in the circulatory system. e. Development into a trophzoite, feeds on hemoglobin and other nutrients f. After feeding and replication (schizogony), the pathogen ruptures the host RBC and the progeny pathogens infect additional RBCs g. Some of the pathogens develop into male and female gametocytes (microgametocytes and macrogametocytes) 4.Sexual phase (sporogony) in mosquito vector h. Gametocytes are ingested by another mosquito during a bloodmeal i. Sexual reproduction occurs, sporozoites are formed that repeat the cycle
What are five steps in antigen presentation and activation of T cells (Table 13.3, 5 steps summarized in the slides)? What are the three general types of cells generated by CD4 T cell activation (helper, memory, regulatory) and what are their roles (MHC II)?
5 steps in antigen presentation and T-cell activation - 1. Phagocytosis of microbes by phagocytes such as macrophages or dendritic cells (or binding of antigen to immunoglobulin on a B-cell) - 2. Processing and binding of the antigen to the MHC-II receptor on the phagocyte (or B-cell) - 3. Display of the MHC-II/antigen complex on the cell surface - 4. Recognition of MHC-II/antigen complex by a T-cell by BOTH the T-cell receptor (recognizing "non-self") AND the CD4 coreceptor (recognizing "self") - 5. Secretion of interleukins and activation of the T-cell - T memory cells: Remain for years, ready to mount immediate response upon activation - T helper cells: - Produce growth factors that stimulate B cells (T helper 2 cells) - Produce cytokines that stimulate macrophages (T helper 1 cells) - Produce cytokines that stimulate inflammation (T helper 17 cells) - T regulatory cells: Regulates inflammation, immune response; prevents autoimmunity
What are HIV and AIDS? What type of virus is HIV, and how does this type of virus "violate" the classical central dogma (DNA -> RNA -> protein)?
Acquired immune deficiency syndrome (AIDS) Caused by the human immunodeficiency virus (HIV) HIV is a retrovirus (with an RNA genome that is reverse transcribed into DNA)
What are the four major steps in infection of individual host cells by HIV? Which type of cells does HIV primarily infect?
Adsorption, endocytosis and uncoating a. Recognition of specific host cell receptors by viral spike proteins Reverse transcription and integration into the host cell chromosome b. Reverse transcriptase from the infecting virus converts RNA genome to DNA c. DNA is transported to the host cell nucleus d. Integrase inserts the viral DNA into the host cell chromosomal DNA, resulting in a provirus e. This latency can persist for years Activation of provirus genes, signaled by stimuli from the host immune system Production of viruses and exit from cell f. Viral proteins are expressed g. The viral protease cleaves some products to their active form h. Spike proteins embed in host membrane Virus buds from the host cell; lysis
What are some basic steps in the agglutination test?
Agglutination test: Example of a visual, quantitative test for the amount (or titer) of antibody in a serum sample (similar to tube dilution test for antibiotic sensitivity) ¥ Same amount of antigen is added to each tube or well. ¥ Dilutions of the sample containing antibody (e.g. serum from blood) are made ¥ Agglutination (clumping) occurs in tubes/wells containing sufficient antibody ¥ Lowest dilution that results in agglutination is used to determine titer
What are alloantigens, superantigens, and allogens?
Alloantigens a. Cell surface markers and molecules that occur in some members of the same species, but not in others b. The basis for an individual's blood group and major histocompatibility profile c. Responsible for incompatibilities that can occur in blood transfusion or organ grafting Superantigens d. Bacterial toxins that are potent stimuli for T-cells e. Activate T-cells at a rate 100 times greater than ordinary signals f. The result can be an overwhelming release of cytokines and cell death g. Toxic shock syndrome and certain autoimmune diseases are associated with superantigens Allergens: antigens that evoke allergic reactions
What are two different types of flu vaccine, and why do they typically have to be updated every year (antigenic drift)?
Answered in the previous question.
What is meant by antigenic drift and antigenic shift, and what are the consequences of these processes? How do the multiple segments of the influenza genome facilitate antigenic shift?
Antigenic drift: "Small" changes in individual genes by point mutation ¥ Mutations in genes encoding N and H during replication result in small differences in N and H structure ¥ Antibodies developed by exposure to previous (unmutated) versions recognize the new, mutated versions less effectively (or not at all) ¥ Antigenic drift produces yearly variation in most influenza strains ¥ This is the reason why flu vaccines are revised yearly Antigenic shift: "Large" changes due to recombination of genome segments ¥ Exchange ("reshuffling") of one or more strands of RNA genome between different viruses: This is facilitated because the genome has 8 separate strands ¥ Occurs during co-infection by two different viruses of a single host cell ¥ Requires a host that both viruses are able to infect. Antigenic shift resulting in recombination between a human flu virus and a bird flu virus often occurs in swine, which both viruses can infect ¥ Can result in large alterations in host range and/or virulence, because entire gene sequences are changed ¥ More likely to produce highly altered, pandemic strains that spread more quickly and are more virulent
Which of these (active or passive, natural or artificial immunity) does vaccination fall under? Be able to briefly explain how vaccination can protect the host against exposure to a pathogen.
Artificial active immunity falls under this. A vaccine will activate both antibody and cell-mediated immune responses to the pathogen, but cause minimum damage/reaction to host; also produce memory so as to be long-lasting; stable, inexpensive
Why is viral meningitis referred to as "aseptic meningitis"? How does viral meningitis compare to other forms of this disease in terms of severity?
Aseptic meningitis: No bacteria or fungi are found in the CSF o Usually these are cases of viral meningitis Generally milder than bacterial or fungal meningitis o Usually resolved within 2 weeks o Mortality rate less than 1%
Where in the body do T and B cells mature, and in what regions of the body are they typically found?
B-cells mature in specialized bone marrow sites and T-cells mature in the thymus. Both cell types migrate to separate areas of lymphoid organs (lymph node and spleen).
What is a major benefit of the "memory" of the specific immune system, in terms of antibody production upon a second exposure to a pathogen/antigen?
Benefits of immune memory: faster response to subsequent infection. Antibody production after second exposure to the pathogen is much faster due to T and B memory cell.
What role do Lactobacillus spp. play in preventing colonization of the vagina by other organisms?
By converting glycogen and sugars to acid which doesn't allow many microorganisms to grow.
What are cytotoxic T cells, and what sort of CD receptor do they contain? How are they activated by presentation of antigens via MHC Class I markers?
CD8 receptors: found on cytotoxic T-cells and binds to MHC-I ("self") molecules. - Abnormal cells (cancer cells, cells infected by viruses) will present antigens along with their MHC-I receptors - T-cells with CD8 receptors bind to the antigen and recognize the MHC-I, and thus recognize the "self" cell as a cell to be destroyed - CD8 T-cell is activated into a cytotoxic T cell and targets presenting cell for destruction
What does the term "immunologically privileged" mean? Is there a normal microbiota in the central nervous system?
CNS is "immunologically privileged" o Only able to mount a partial or different immune response when exposed to an immunological challenge o CNS functions are so vital that even temporary damage that could result from normal immune responses could be detrimental o Macrophages are present but not as active as in other body parts No normal biota in the nervous system.
What is the main sign of impetigo, and what are the main two causative agents of this disease? Which of these causative agents is important in initiating the disease, and which of them typically causes the disease in newborns?
Can cause lesions that look like peeling skin, crusty and flaky scabs,etc. Can be caused by either Staphylococcus aureus or Streptococcus pyogenes, (both Gram + cocci) or may be caused by a mixture of the two o S. pyogenes begins all cases of the disease, but later S. aureus takes over and produces a bacteriocin that destroys S. pyogenes o S. pyogenes is more often the cause of impetigo in newborns; S. aureus is more often the cause of impetigo in older children
What are some characteristics of Candida albicans, the most common causative agent of vaginitis? Is this fungus normally associated with humans? Under what conditions does it act as an opportunistic pathogen?
Characteristics o Dimorphic fungus (hyphae and yeast cell forms) o Normal biota in 50 - 100% of humans o Live in low numbers on mucosal surfaces of the mouth, gastrointestinal tract, vagina, etc. o In healthy people, the fungus is not invasive o Can become an opportunistic pathogen if normal microbiota is disturbed, or in immunocompromised hosts o AIDS patients are at risk of developing systemic Candida infections
What are some characteristics of Vibrio cholerae, the causative agent of cholera? What are important symptoms and a key treatment/therapy for this disease?
Cholera has been a devastating disease for centuries o Has shaped a good deal of human history in Asia and Latin America where it has been endemic Conditions where outbreaks of cholera occur o After natural disasters, war, refugee camps o E.g. after the earthquake in Haiti in 2010 o Poor sanitation, contaminated drinking water Causative Agent ¥ Vibrio cholerae are curved rods, motile with a single polar flagellum ¥ Phylum Proteobacteria; Gram negative, facultative anaerobes Signs and Symptoms ¥ Incubation period of a few hours to a few days ¥ Abrupt symptoms of vomiting followed by copious, watery feces called secretory diarrhea or "rice-water stools"; massive fluid loss ¥ In severe cases, untreated patients can lose up to 50% of body weight ¥ Cholera diarrhea causes ¥ Loss of blood volume ¥ Acidosis from bicarbonate loss ¥ Potassium depletion causing cramps, thirst, flaccid skin ¥ Hypotension and shock ¥ If cholera is left untreated, death can occur in less than 48 hours ¥ Mortality rate >50% ¥ Key to cholera therapy is prompt replacement of water and electrolytes ¥ Loss accounts for severe morbidity and mortality Treatment can also be accomplished with antibiotics
Who was responsible for the first vaccine, when was it used, and what viruses (both the human version and the bovine version) were involved?
Edward Jenner developed the first vaccine (1796) o Exposing a host to cowpox virus (related to smallpox) o This exposure made the host immune to smallpox when later exposed
What is meant by clonal deletion, clonal selection, and clonal expansion? How does each of these function in specific immunity?
Clonal deletion a. Removes any T- or B-cell that can potentially react to self before any potential damage can occur b. This is the basis of immune tolerance, or tolerance to self c. Autoimmunity: loss of immune tolerance to self through the survival of "forbidden clones" that escape clonal deletion Clonal selection d. The mechanism by which the exactly correct B- or T-cell is activated by any incoming antigen e. Lymphocyte specificity is preprogrammed, existing in the genetic makeup of each B- and T-cell before an antigen has ever entered the tissues f. Each genetically distinct lymphocyte expresses only a single specificity and can react to only one type of antigen Clonal expansion: the rapid multiplication of B- or T-cell clones after activation by an antigen
What are two tests that can be used to differentiate Staphylococcus aureus from Streptococcus pyogenes in impetigo?
Coagulase test and Catalase test
What is an example of a fungus that cause meningitis (this example, gone over in class, is endemic or native to the southwest US)? Where does the primary infection for this fungus occur?
Coccidioides species Causative Agent and epidemiology ¥ Fungi native (endemic) to southwestern US ¥ Septate hyphae that fragment into thick-walled, block-like arthrospores ¥ Athrospore germinates into a small, parasitic cell called a spherule ¥ C. immitis is responsible for disease in California's San Joaquin valley, SW US ¥ Outbreak after Northridge earthquake (1994) due to dispersal of airborne spores
What is a common method that is used for diagnosis of both measles and rubella?
Common method of diagnosis is acute/convalescent IgG.
What are two genera of fungi that cause meningitis? Which one is endemic to southern California and other regions in the southwest US?
Cryptococcus neoformans (Fungi) Coccidioides species Fungi native (endemic) to southwestern US
What are some of the defenses of the female genital tract? Which regions have a normal microbiota?
Defenses in the vagina o Mucus and antibody secretions o After puberty and before menopause: Secretion of glycogen, which is fermented by normal microbiota resulting in decrease in pH Female genital tract o Only the vagina is colonized, no known microbiota beyond the cervix o After the onset of puberty, estrogen leads to glycogen release in the vagina, resulting in an acidic pH o Lactobacillus species thrive in the acidic environment and contribute to it by converting glycogen and sugars to acid o The predominance of Lactobacillus, combined with the acidic environment, discourages the growth of many microorganisms o The estrogen-glycogen effect continues with minor disruptions through childbearing years until menopause o The fungus Candida albicans is also present at low levels When normal vaginal microbiota is altered, overgrowth of Candida albicans can result in a yeast infection
What are the natural defenses of the gastrointestinal tract? How does the abundance and diversity of the normal GI microbiota compare with microbiota in other regions of the body, and which part of the GI tract contains the greatest number of microbes?
Defenses of the GI tract o All intestinal surfaces are coated with a layer of mucus o Immune system cells in GALT (gut-associated lymphoid tissue) o Secreted antibodies can be found on most GI tract surfaces o Muscular walls of the GI tract keep food and microorganisms moving through peristalsis o Saliva contains lysozyme and lactoferrin o Stomach fluid is antimicrobial due to its high acidity (pH ~2) o Bile (produced by the liver) is also antimicrobial o Commensal microbiota provide the protection of microbial antagonism Small, large intestines have the highest concentrations (up to 100 billion cells/mL), with 1000 or more different species
What are some of the defenses of the urinary tract and some examples of the normal microbiota?
Defenses of the urinary tract o Flushing action of urine flowing out of the system o Desquamation (shedding) of epithelial cells lining the urinary tract o Normal biota are the most common microbial threat to the urinary tract ♣ Cells lining the urinary tract have different chemicals on their surface than those lining the GI tract ♣ Bacteria that are adapted to adhere to the GI tract cannot easily attach to the urinary epithelium o Defenses in the urine ♣ Acidic pH ♣ Lysozyme: enzyme that breaks down peptidoglycan ♣ Lactoferrin: iron-binding protein that inhibits bacterial growth ♣ Secretory antibodies: specific for previously encountered microorganisms In both genders, the outer region of the urethra harbors some normal biota o Kidneys, ureters, bladder, and upper urethra are presumably kept sterile by urine flow and regular bladder emptying Principal known residents of the urethra o Streptococci, Staphylococci, Corynebacteria, Lactobacilli
What is herd immunity? How can it help protect people that may not have effective immunity? What types of people might not have effective immunity and/or not be able to get vaccinated?
Development of herd immunity when nearly all members of a population are vaccinated o Phenomenon in which a certain percentage of the population is vaccinated, making it impossible for the microbe to circulate o This can prevent large outbreaks, and give effective immunity to those who do not have immunity ♣ Elderly that have weakened immune systems ♣ Infants that have not yet been vaccinated ♣ People with weakened immune systems • E.g. AIDS patients ♣ People with certain illnesses or immune disorders/allergies
What is a fecal transplant, and how can this be used in treatment of C. difficile infection?
Fecal transplants (oral or enema) from a healthy person with normal microbiota have been very effective; more tests are being done It can be used as a treatment by getting a stool donor to get a new microbiota to get the normal microbiota again.
What are some of the defenses of the upper and lower respiratory tracts? How does the normal microbiota differ between the upper and lower respiratory tract, and how does it compare to that of the skin?
First line defenses a. Nasal hairs, mucus b. Cilia, coughing, sneezing to expel cells/particles Second line defenses c. Macrophages (lower tract) Third line defenses Pathogen-specific secretory antibodies, most importantly IgA antibodies It is similar to skin but have some that can cause disease.
What is fluorescent in situ hybridization (FISH)? How is this different from the hybridization method used on DNA extracted from a microbe or sample? What is typically the target molecule of FISH?
Fluorescent in situ hybridization (FISH) o Rapidly identifies 16S RNA sequences without first culturing the organism, using microscopy Uses fluorescently-labeled gene probes that will bind to a specific sequence in the 16S rRNA
What are some characteristics of Clostridium difficile and its pathogenesis/virulence factors associated with acute diarrhea? Why is it known as "antibiotic-associated diarrhea"?
Gram-positive, endospore forming rod Phylum Firmicutes Member of normal intestinal biota Pathogenesis and Virulence Factors ¥ Able to superinfect the large intestine when antibiotic treatment has disrupted the normal biota ¥ Spore formation allows it to resist subsequent treatments with antimicrobial drugs ¥ Produces A and B enterotoxins ¥ Cause areas of necrosis in the large intestine ¥ C. difficile is found as normal biota in the intestine, either as a constant resident or regularly introduced by ingesting C. difficile spores ¥ Was once considered completely harmless ¥ Now known to cause antibiotic-associated colitis Caused by therapy with broad-spectrum antibiotics, disturbing normal intestinal microbiome and resulting C. difficile superinfection
How is HIV transmitted, and how are both HIV infection and AIDS diagnosed?
HIV is mainly transmitted through a. Sexual intercourse (semen, vaginal secretions) b. Blood or blood products (free virus or infected leukocytes) c. Spinal fluid, amniotic fluid d. Babies can be infected before or during birth, or through breastfeeding You check for antibodies when diagnosing HIV. In the U.S, diagnosis with AIDS requires e. Testing positive for the HIV virus and... f. Meeting at least one of the following criteria i. CD4 cells below 200 cells/microliter of blood ii. CD4 cells account for fewer than 14% of lymphocytes Experience one or more AIDS-defining illness
Does Vibrio cholerae have a low or high infectious dose, and what does this imply about its virulence? What role does the cholera toxin play in pathogenesis, and where are genes for this toxin encoded?
High infectious dose and it means it's very effective in infecting bacteriophages? Virulence of V. cholerae due entirely to the cholera toxin (CT) ¥ Toxin causes intestinal cells shed large amounts of electrolytes into the intestine accompanied by profuse water loss ¥ Cholera toxin genes are encoded by a temperate bacteriophage ¥ Virulent strains of V. cholerae contain this prophage ¥ Virulence can be transferred to non-virulent strains by infection with this bacteriophage
What types of cells does Plasmodium primarily infect in humans?
Human blood cells
How can hybridization methods be used to identify the presence of a specific DNA (or RNA) sequence in a DNA sample? What is a probe, and why is the probe labeled?
Hybridization o Used to identify bacterial species by analyzing DNA sequences o Probes: small fragments of single-stranded DNA or RNA complementary to the specific DNA sequence of a particular microbe ♣ Probes are labeled in some way: e.g. fluorescence or radioactivity o Unknown test DNA is extracted from cells and bound to blotter paper o Probes are added to the blotter paper, hybridization is allowed to occur, excess probe is washed away, and probe bound to the unknown DNA sample is detected based on the probe label.
What do the following terms refer to: Antigen/immunogen, immunocompetence, epitope, immunoglobulin, antibody, interleukins?
Immunocompetence: The ability of the body to react with many different foreign substances Antigens or immunogens: Foreign (pathogen-associated) molecules that stimulate an immune response by B and T cells ¥ epitope: The specific structure on an antigen that is recognized ¥ Immunoglobulins: B-cell receptors that recognize specific epitopes ¥ Antibodies: Secreted (rather than membrane-bound) immunoglobulins ¥ Leukocytes "talk to each other" by secretion/detection of interleukins
What are some types of molecules act as immunogens (antigens)? Are they typically macromolecules or small molecules? What are haptens, and how can they be more easily recognized by the immune system?
Immunogen: synonymous with antigen a. Substances that can elicit an immune response b. Must meet certain requirements in foreignness, shape, size, and accessibility c. Must not be a normal constituent of the body Examples include: whole microbes or their parts, cells, or substances that arise from other humans, animals, plants, and various molecules Many different types of molecules can be antigens: Macromolecules (~100 kilodaltons) are typically highly immunogenic and small molecules (sugars, amino acids, short peptides) typically are not recognized unless these "haptens" are bound to a larger structure
Why are immunologic methods are both specific and sensitive?
Immunological tests have a high degree of specificity and sensitivity ¥ Specificity: property of a test to focus only on a certain antibody or antigen, and not react with an unrelated or distantly related antigen Sensitivity: detection of even minute quantities of antibodies or antigens in a specimen; reflects the degree to which a test will detect every positive person
What are the important structural components of HIV, and what role do the following play during infection: Antireceptor "spike" protein, reverse transcriptase, protease, integrase?
Important structural components of HIV virus to know... - Envelope, with embedded GP-120 antireceptor "spikes" - Protein capsid containing RNA genome and the following enzymes... - Reverse transcriptase: Conversion of RNA genome to DNA - Integrase: Integrates viral DNA into host cell chromosome - Protease: Processes/cleaves viral proteins into their active form Many of these components make good targets for selectively toxic anti-HIV drugs
What is meant by antigen processing and presentation? What are two important types of antigen presenting cells, or APCs? What type of cell to APCs present antigen to? What role does antigen presentation play in specific immunity?
In most immune reactions, the antigen must be further acted upon and formally presented to lymphocytes by antigen presenting cells (APCs) Examples of APCs a. Phagocytic cells such as macrophages and dendritic cells b. B cells After processing is complete, the antigen will be bound to the MHC receptor and moved to the surface of the APC so it will be readily accessible to T lymphocytes The activated T cell is central to all of T-cell immunity and most of B-cell immunity
What role does Streptococcus mutans play in tooth decay (associated with its virulence factors)? How does the presence of sucrose play a role?
In the presence of sucrose, S. mutans produces sticky polymers called fructans and glucans o These adhesives help bind them to the smooth enamel surfaces o Contribute to the sticky bulk of the plaque biofilm If plaque is not removed, it can result in a carious lesion o Streptococci and other bacteria produce acid as they ferment carbohydrates o At pH <5, tooth enamel begins to dissolve S. mutans is a facultative anaerobe, so fermentation is enhanced by anaerobic conditions produced in deeper layers of the plaque biofilm
How does Neisseria (and many other microbes that cause meningitis) typically get from its initial site of infection to the CSF? How is this organism cultivated, and what are some examples of tests that can be used to identify it?
Initial Neisseria infection in mouth Contact with highly vascularized roof of nasal cavity Transfer to blood o Meningococcemia From blood, they can get into the cerebrospinal fluid ¥ Cerebrospinal fluid, blood, and nasopharyngeal samples are taken ¥ Stained and observed for characteristic Gram negative diplococci ¥ Cultivation may be necessary to differentiate from other species ¥ "Chocolate" agar medium (lysed blood cells) is used ¥ Provides a variety of complex nutrients required for Neisseria ¥ Specific rapid tests are available for detecting capsular polysaccharide or cells directly from specimens without culturing ¥ Presumptive identification of the genus obtained through ¥ Gram stain (Gram negative diplococci) ¥ Oxidase testing
How many antigen binding sites are present on a given antibody? How does this, and the fact that antibodies also contain a site for recognition by host cells (e.g. macrophages), assist in their activities?
It has two antigen binding sites. Because the antibody contains regions that bind the antigen AND are recognized by host cells, this effectively "tags" the bound antigen for destruction
What are the important structural components of influenza virus, the causative agent of flu? Know that most fatalities of this disease are due to complications, mainly development of pneumonia.
Lipoprotein envelope Glycoprotein spikes a. Hemagglutinin (H) b. Neuraminidase (N) c. Different flu strains are named by these different antigens, e.g. H1N1, H2N3 ssRNA genome d. 10 genes on 8 RNA strands
What are the target microbes/diseases of the MMR vaccine, and what type of vaccine is this?
MMR (mumps, measles, rubella) vaccine contains live, attenuated measles virus that confers protection for up to 20 years. It is a live virus type of vaccine.
What is meningitis, what are some important signs/symptoms (general to most cases of meningitis), and how do microbes cause this disease? Know that, similar to pneumonia, there can be many different causative agents for this disease.
Meningitis is caused by inflammation of the meninges o Anatomical syndrome: many different microorganisms (bacteria, fungi, viruses) can cause an infection of the meninges and all cause the same constellation of symptoms Signs and Symptoms (Typical symptoms, regardless of causative agent) ¥ Headache, painful or stiff neck ¥ Fever, nausea and vomiting; skin rash in some cases ¥ Photophobia (sensitivity to light) ¥ Increased number of lymphocytes in the CSF ¥ In general, most pathogens causing meningitis enter the bloodstream from an initial infection site, and then migrate from the blood to the cerebrospinal fluid
What do immunologic (or serological) methods for identifying the presence of microbes or antigens make use of? How might they be used to test for the presence of an antigen in a sample, or to test for the presence of an antibody in a sample?
Methods for testing phenotypic characteristics that make use of antibodies Testing for the presence of specific antibodies or antigens o E.g. in samples collected from a patient's blood serum Often easier than testing for the microbe itself o patients are tested for antibodies to HIV in standard laboratory test kits Can be used to either o Test a sample for a specific unknown antibody using a known antigen o Test a sample for a specific unknown antigen using a known antibody Can be either qualitative or quantitative ¥ Characteristics of antibodies and/or antigens such as their quantity or specificity can reveal the history of a patient's contact with microorganisms or other antigens ¥ Serology: in vitro testing of based on antibodies in blood serum ¥ Immunological testing can also be used to test for antigens in a given sample based on known antibodies
What are three different methods for identifying bacteria in patient specimens or natural samples, and what are the basic attributes of each of these methods?
Methods to identify bacteria in patient specimens or natural samples o Phenotypic: Considers macroscopic and microscopic morphology, physiology, and biochemistry o Immunologic: Serological analysis, either by detection of antibodies in a sample or by using antibodies to detect specific antigens in a sample o Genotypic: Detection and/or analysis of DNA or RNA specific to a given microbe or group of microbes.
In which regions of the world is malaria most prevalent today?
Mosquito control in temperate areas has restricted it to equatorial regions
What are some methods of prevention and treatment of malaria? Is a vaccine available?
Mosquito control; use of bed nets; no vaccine yet available; prophylactic antiprotozoal agents
What are some of the defenses of the circulatory and lymphatic systems? Do they have a normal microbiota in healthy individuals?
Multiple defenses against infection a. 5,000 - 10,000 leukocytes per microliter of blood b. Lymphocytes: Specific immunity c. Phagocytes: Innate and specific immune response d. Few microbes can survive in the blood with so many defensive elements e. Some microbes have evolved mechanisms to avoid these defenses No normal microbiota
What are important differences between natural immunity and artificial immunity, and between active immunity and passive immunity? Which of these involves B and T cell activation in the host, and which involves transfer of antibodies to the host from another source?
Natural immunity: Any immunity that is acquired through the normal biological experiences of an individual Artificial immunity: Protection from infection obtained through medical procedures such as vaccines and immune serum ¥ Active immunity ¥ Occurs when an individual receives immune stimulus that activates B and T cells to produce immune substances such as antibodies ¥ Creates memory that renders the person ready for quick action upon re-exposure to the same antigen ¥ Requires several days to develop ¥ Lasts for a relatively long time ¥ Can be stimulated by natural or artificial means ¥ Passive immunity ¥ Occurs when an individual receives antibodies from another human or animal ¥ Recipient is protected for a short period of time, even though they have not had prior exposure to the antigen ¥ Lack of memory for the original antigen, lack of antibody production by the patient ¥ Immediate onset of protection ¥ Can be natural (e.g. breastfeeding) or artificial (injection) in origin Useful when there is no effective treatment available or to treat immune deficiencies
What is the name and some attributes of the causative agent of the most serious form of acute meningitis? What are some important virulence factors?
Neisseria meningitidis (Phylum Proteobacteria) ¥ Gram-negative diplococcic (pairs) ¥ Commonly known as the meningococcus ¥ Often associated with epidemic forms of meningitis ¥ Causes the most serious form of acute meningitis Pathogenesis and Virulence Factors ¥ Bacteria entering the blood vessels rapidly penetrate the meninges and produce symptoms ¥ Pathogen releases endotoxin into the generalized circulation which stimulates white blood cells ¥ Bacterium produces IgA protease and a capsule that counter the body's defenses
Is it always necessary to cultivate a microbe in order to identify it, or to identify a potential causative agent for a disease?
No, it's not always necessary to cultivate a microbe in order to identify it.
What are some of the important virulence factors of Staphylococcus aureus in impetigo, and how do they function?
Pathogenesis and Virulence Factors ¥ Exfoliative toxins A and B ¥ Coded for by a phage that infects some strains of S. aureus ¥ Attack a protein important in cell-to-cell binding in the epithelium ¥ Leads to characteristic blistering ¥ Breakdown of skin architecture facilitates spread of the bacterium ¥ Coagulase ¥ Coagulates plasma ¥ Helps pathogen evade immune system ¥ 97% of all human isolates produce this enzyme; considered diagnostic of the species ¥ Hyaluronidase ¥ Digests the intracellular "glue" (hyaluronic acid) that binds connective tissue in host tissues ¥ Staphylokinase ¥ Digests blood clots ¥ DNase, a nuclease that digests DNA ¥ Lipase, an enzyme that helps the bacteria colonize oily surfaces
What is periodontal disease? What is the name of one of the microorganisms associated with this polymicrobial disease?
Periodontal disease is so common that 97 - 100% of the population has some manifestation by age 45 Most kinds of periodontal diseases are due to bacterial colonization and varying degrees of inflammation that occur in response to gingival damage ¥ Porphryomonas gingivalis is one of the major constituents Causative agents tend to be strict anaerobes, so anaerobic conditions in biofilms contribute to the disease (just as in dental caries)
What are some examples of phenotypic methods for identifying an unknown microbe? What is typically the first test/observation that is used to identify an unknown microbe after isolation (hint: it involves staining and microscopy)?
Phenotypic Methods: ¥ Morphological characteristics ¥ Light microscopy with or without staining procedures for observation of... ¥ Cell shape, size, and arrangement ¥ Gram stain reaction, acid-fast reaction ¥ Endospores, granules, and capsules ¥ Electron microscopy can pinpoint additional structural features ¥ E.g. cell wall, flagella, pili, fimbriae ¥ Colony morphology, color ¥ Physiological/biochemical properties ¥ Traditional mainstay of bacterial identification ¥ Enzyme production and other biochemical properties ¥ Sensitivity to antibiotics or bacteriophage infection ¥ Tests for bulk composition of cell wall, membrane, other structures ¥ MALDI-TOF mass spectrometry to generate "fingerprint" for identification
What is the causative agent of malaria, and what type of organism is this?
Plasmodium species are protozoans in the sporozoan group Four species: P. malariae, P. vivax, P. falciparum, and P. ovale
What are some of the risk factors and methods of prevention and treatment of Clostridium difficile? What is probiotic treatment?
Prevention and Treatment ¥ Uncomplicated cases respond to withdrawal of antibiotics and replacement therapy for lost fluids and electrolytes ¥ More severe infections are treated with certain antibiotics for several weeks until the intestinal biota returns to normal ¥ Vancomycin is often used, but C. difficile spores are not affected ¥ Treatment techniques being developed ¥ Treatment with a prophylactic drug that specifically inhibits C. difficile along with initial antibiotic treatment ¥ Restoration of normal biota by ingestion of a mixed culture of lactobacilli and yeasts (i.e. probiotic treatment: administering "healthy" microbes to compete with pathogenic microbes) Fecal transplants (oral or enema) from a healthy person with normal microbiota have been very effective; more tests are being done
What are some of the major targets of anti-HIV drugs? What are some of the obstacles to development of an HIV vaccine?
Several key components of HIV can be targeted by selectively toxic drugs 1. Fusion inhibitors that prevent interaction of spike proteins w/ CD4 receptors. Fuzeon is an example of a drug that prevents fusion. 2. Reverse transcriptase inhibitors that prevent conversion of the RNA genome to DNA. These include nucleotide analogs such as AZT (azidothymidine) that are used by the reverse transcriptase but do not affect the host. ¥ https://www.youtube.com/watch?v=1so7D5twHSE 3. 3. Integrase inhibitors that prevent integration of viral DNA into host chromosome 4. 4. Protease inhibitors that prevent the HIV protease from cleaving HIV polyproteins to their active forms, resulting in non-infective viruses
What sorts of hosts are most susceptible to meningitis caused by Listeria monocytogenes? What is the normal reservoir of this pathogen, how is it typically introduced to human hosts, and how can transfer/infection be prevented?
Signs and Symptoms ¥ Mild or subclinical infection in healthy adults ¥ Nonspecific symptoms of fever, diarrhea, and sore throat ¥ Elderly, immunocompromised, fetuses, and neonates ¥ Affects the brain and meninges and causes septicemia ¥ Death rate is 20% ¥ Pregnant women are especially susceptible ¥ Microbe crosses the placenta or postnatally through the birth canal ¥ Intrauterine infections may result in premature abortion and death Pathogenesis and Virulence Factors ¥ Resistant to cold, heat, salt, pH extremes ¥ Grows inside host human cells and can move directly from an infected host cell to an adjacent healthy cell, helping it to evade the immune system Prevention and Treatment ¥ Antibiotic therapy should be started as soon as listeriosis is suspected ¥ Prevention can be improved by adequate pasteurization temperatures ¥ Proper washing, refrigeration, and cooking of foods ¥ Infectious dose is 10-100 million...just need to prevent exposure to large amounts, i.e. prevent growth in food products ¥ Low virulence, high infective dose! Pregnant women cautioned not to eat soft, unpasteurized cheeses where Litsteria might be present in high numbers
What are the signs, symptoms, and causative agent of the macropapular disease measles? Know that many fatalities are due to secondary infections, such as pneumonia.
Signs and Symptoms ¥ Sore throat, dry cough, headache, fever, conjunctivitis (inflammation of the conjunctiva, or outer layer of eye), lymphadenitis (enlargement of lymph nodes) ¥ Red, maculopapular exanthem (widespread rash) that erupts on the head and progresses to the trunk and extremities Sequelae and Complications ¥ Pneumonia, secondary bacterial infections such as ear and sinus infections, additional complications; see http://www.cdc.gov/measles/about/complications.html ¥ Death in many cases is due to secondary infections, e.g. pneumonia Causative Agent: Measles virus ¥ Genus Morbillivirus, family Paramyxovirus ¥ Enveloped, single-stranded RNA virus
In what ways is the direct fluorescence antigen test similar to and different from FISH?
Similar to FISH, but it detects an antigen with a fluorescently-labeled antibody Sample is collected from patient and is incubated with labeled antibody Excess antibody is washed away, and the sample is observed by fluorescence microscopy
What are some functions of the normal microbiota of the gastrointestinal tract? Are most microbes in the GI tract aerobes or anaerobes? Why is the GI tract predominantly an anaerobic environment?
Some functions of the normal biota o Help with digestion ♣ Allow for degradation of some foods, e.g. dietary fiber, that human digestive enzymes alone do not act on o Provide nutrients that we can't provide ourselves such as vitamins; e.g. E. coli synthesizes vitamin K o Presence of normal biota is important for proper functioning of epithelial cell structure o Plays an important role in "teaching" the immune system to react to microbial antigens Most members of GI tract microbiome are strict or facultative anaerobes o Lots of nutrients o Low O2 exposure Microbes create and maintain anaerobic environment
How does specific (or acquired) immunity differ from innate immunity? Which specific types of leukocytes are involved? What are two characteristics of specific immunity?
Specific or adaptive immunity is acquired only after an immunizing event such as an infection B and T lymphocytes undergo a selective process that prepares them for reacting only to one specific antigen or immunogen a. Helps fight the specific infection in the short term b. Allows for faster response to repeated infections in the longer term Specific immunity is critical in vaccination
What is the causative agent of smallpox? What are two different viruses that have been used as vaccines for smallpox, and which of these is also useful in making recombinant vaccines? How prevalent is smallpox in the world today, and why?
Variola virus, an orthopoxvirus (Enveloped DNA virus) Need more info from this
What are the four stages in HIV infection, and what symptoms are associated with which stages? What are ADIs, and which stage do these occur in?
Stage I: ~2 weeks after infection a. Initial symptoms a few weeks after infection are essentially flu-like b. Fever, fatigue, aches, swollen glands c. High levels of virus in the blood, antibodies not yet abundant Stage II: 1-2 months d. Virus numbers in blood drop, antibodies to virus increase Stage III: ~2-15 years e. Mostly asymptomatic; virus is mainly present inside cells; T-cells slowly decrease Stage IV: AIDS, after T-cells drop below a threshold level f. AIDS-defining illnesses (ADI) develop, such as opportunistic infections, cancers Severe weight loss, poor nutrient absorption, memory loss, dementia
What are some characteristics regarding Staphylococcus aureus's resistance to heat, desiccation, salt concentrations, and antimicrobial drugs?
Staphylococcus is among the sturdiest of all non-spore-forming pathogens o Withstands high salt (7 - 10%), o Tolerates high temperatures (survives 60 °C for 1 hour) o Remains viable after months of air drying o Resists the effects of some disinfectants and antibiotics (e.g. MRSA)
What are six steps in activation of B cells, and how are T helper cells involved? What three cell types result, and which of these is responsible for antibody production (Table 13.6)?
Steps in B-cell activation 1. Binding of antigen to the specific immunoglobulin on the B-cell surface 2. Processing and presentation of the antigen on an MHC-II receptor 3. Interaction of the MHC-II/antigen complex with a T helper cell that has been activated by exposure to the same antigen. Cells secrete interleukins, T-cell secretes B-cell growth factors 4. B-cell activation results from the interaction with the T helper cell 5. Differentiation of the activated B-cell into three cell types 6. Clonal expansion of all three cell types Cell types that result from this are: ¥ Regulatory B-cells that secrete cytokines, regulate T-cell response ¥ Memory cells that persist for extended periods of time Plasma cells that secrete antibodies specific to the activating antigen
What are three causative agents of pneumonia discussed in class? How are Streptococcus and Legionella able to evade phagocytosis in the lungs?
Streptococcus pneumoniae, "pneumococcus" Most common cause of bacterial pneumonia Capsule is main virulence factor (prevents phagocytosis) Vaccines are available (subunit, based on capsid...see earlier this lecture) ¥ Legionella pneumophila ("lung-loving") ¥ Gram negative (phylum Proteobacteria) ¥ Causes a form of pneumonia called Legionnaires' disease ¥ Amoebas in water/soil serve as reservoirs ¥ Intracellular parasite of phagocytes ¥ Is able to survive inside phagocytes after phagocytosis, instead of being destroyed! ¥ Mycoplasma pneumoniae (bacterium related to Gram+, but lacks a cell wall) ¥ Lack of acute illness gives rise to the name "walking pneumonia" ¥ Small size and tight attachment to host cells can help this bacterium evade immune system
Which microbe is the cause of most of the majority of urinary tract infections (UTIs)? Where does it come from, and what are some of its virulence factors?
Uropathogenic Escherichia coli (UPEC) accounts for 80% of UTIs ¥ UPEC are normal GI tract biota, and are not strains of E. coli that cause diarrhea and other digestive tract diseases ¥ UPEC virulence factors ¥ Fimbriae that allow tight attachment during urine flow ¥ Flagella allow for further colonization in absence of flow
What is phage typing, and how is this technique performed to identify different bacteriophage that a microbe is susceptible to? (think of it as a combination of a Kirby Bauer test and a plaque assay)
Testing an isolated bacterium for its sensitivity to different types of phage with a known host range. ¥ Use spread plate technique to inoculate a plate with the microbe to be tested. ¥ Introduce different strains of known bacteriophage on different labeled regions of the plate. ¥ Incubate the plate. ¥ Large clearings (plaques) indicate bacteriophage that the microbe is sensitive to (can be infected by).
What is the major histocompatibility complex? What are the functions of MHC Class I and MHC Class II markers in immunity? Which ones function in endogenous vs. exogenous pathways?
The Major Histocompatibility Complex (MHC) ¥ One set of genes that codes for human cell markers or receptors found on all cells except red blood cells ¥ These markers play a vital role in recognition of self by the immune system and in rejection of foreign tissue a. MHC Class I genes (both exogenous and endogenous): b. MHC Class II genes (exogenous only): c. MHC Class III genes: Encode proteins involved with the complement system
What are some differences between measles and rubella? What is a teratogen?
They have different causative agents (rubella is with a rubella virus). Rubella happens in fetus (teratogen) and is not harmful in adults. For culture/diagnosis, rubella uses acute IGm instead of ELISA. Rubella has no treatment. Rubella is a milder rash and only lasts 3 days.
What is the difference between whole-cell/whole-virus vaccines and subunit vaccines? What are some advantages and disadvantages of live, attenuated pathogen vaccines vs. killed/inactivated pathogen vaccines?
Whole cell or virus vaccines o Live, attenuated cells or viruses (most effective, least safe) ♣ Attenuated: weakened, so as not to cause "full-blown" disease o Killed cells or inactivated viruses (safer, not always as effective) Subunit vaccines o Antigenic molecules derived from bacterial cells or viruses (subunits) ♣ Safer still than whole-cell vaccines, but often not as effective Advantages of live, attenuated cells or viruses as vaccines 1. Pathogen can multiply and produce infection (but not disease) ¥ Allows for a stronger immune response, increased memory 2. Confers longer lasting protection 3. Requires fewer doses/boosters 4. Most effective at inducing cell-mediated immunity Disadvantages of live, attenuated cells or viruses as vaccines 1. Attenuated pathogen could mutate to a disease-causing form 2. Attenuated pathogen can replicate and be passed on to others 3. Live, attenuated vaccines may require special storage conditions/facilities to remain active (shorter shelf life)
What are five different examples of the activity that antibodies have on pathogens (Table 13.7)?
a. Antibody binding to epitope on the surface of a pathogen can interfere with growth and reproduction b. Binding of the antibody to epitopes on two separate cells can cause agglutination (clumping) and aid in phagocytosis of the pathogen c. Binding allows better recognition by phagocytes: opsonization d. Pathogens bound by antibody are targeted for lysis by complement (from chapter 12) e. Binding can inhibit the function of specific proteins i. Prevent pathogens from binding to surfaces ii. Prevent activity of exotoxins (antitoxin activity) Inhibit interaction between virus receptors and host cells, thus preventing adsorption and viral infection
What type of lymphocyte cells contain CD4 co-receptors, and how do they aid in immunity? Which type of cells contain immunoglobulins and what role do they play?
a. CD4 receptors: Receptor proteins that binds to MHC II molecules Immunoglobulin (Ig) b. Large glycoprotein molecules that serve as the antigen receptors of B cells c. Made of pairs of heavy and light chains with variable and conserved regions When secreted, immunoglobulins are called antibodies
Which types of cells typically contain MHC Class I and MHC Class II markers?
a. MHC Class I genes: i. Code for markers that appear on all nucleated cells ii. Display unique characteristics of self iii. Allow for recognition of immune reactions b. MHC Class II genes: i. Also code for immune regulatory markers found on macrophages, dendritic cells, and B cells ii. Are involved in presentation of antigens to T cells
What do the terms bacteremia, viremia, fungemia, and septicemia refer to?
a. Viremia: presence of viruses in the blood b. Fungemia: presence of fungi in the blood c. Bacteremia: presence of bacteria in the blood d. Bacteria are frequently introduced into the bloodstream through the course of daily living
What are some important differences between T and B cells (Table 13.1)?
go to word document for this (under lecture 12)
What are three examples of immunologic methods for identifying antigens/antibodies?
o Agglutination test o Direct Fluorescence Antigen Test ♣ Fluorescently-labeled antibody used to detect antigen by microscopy o Enzyme-Linked Immunosorbent Assay (ELISA) Can be either direct (detecting antigen) or indirect (detecting antibody)
What are some important considerations in sample collection from a patient for identification of a microbial pathogen?
o Aseptic technique is imperative o Sterile sample containers and other tools prevent contamination from the environment Care should be taken with samples that contain resident microbiota o Only the infected site should be sampled, and not the surrounding areas
What role do microbial biofilms play in tooth decay and periodontal disease? How are anaerobic conditions established and maintained in these biofilms (similar to GI tract question above)?
o If left undisturbed, the biofilm structure eventually contains anaerobic bacteria that can damage the soft tissue and bones o Also, the introduction of carbohydrates to the oral cavity can result in the breakdown of hard tooth structure due to the production of acid ?
What are five examples of genotypic methods for identifying an unknown microbe? Recognize that, in contrast to many phenotypic methods, most genotypic methods do not rely on cultivation and/or isolation of the microbe(s) in a sample.
o Restriction enzyme digestion of genomic DNA ♣ RFLP: Restriction fragment length polymorphism ♣ Different genome content will result in different RFLP patterns o Hybridization ♣ Uses a labeled probe (made of DNA) that will hybridize to and identify the presence of a specific sequence of DNA o Amplification of specific regions of the genome by PCR ♣ Presence/absence of a specific gene ♣ Combined with sequencing, can be used to identify different microbes in a population ♣ 16S rRNA gene is a common target for this approach o Fluorescence in situ hybridization (FISH) ♣ Fluorescent probes targeting 16S rRNA to identify a specific microbe using fluorescence microscopy o Whole genome sequencing ♣ Decreases in price are making this more common Yields much more information than RFLP or PCR, and can identify many potential phenotypes e.g. (drug resistance)
What are some examples of subunit vaccines? What is meant by DNA vaccines and conjugated vaccines?
o Subunits may be... ♣ Derived from natural cultures of cells or viruses ♣ Synthesized to mimic natural molecules ♣ Manufactured via genetic engineering o "DNA vaccines" that involve gene therapy, or introduction of DNA coding for antigens into the human host, where they are expressed and produce an immune response o Conjugated vaccines: subunits conjugated with proteins to make them more immunogenic
What does ELISA stand for? What are some basic steps in the indirect and direct ELISA methods? Which method is used for detection of antibodies, and which method is used for detection of antigens? How are secondary antibodies used in the ELISA?
o Uses an enzyme-linked indicator antibody to visualize Ag-Ab reactions o Relies on a solid support such as a microtiter plate that can adsorb the reactions Indirect ELISA o Detects antibodies in patient sera based on binding to a known antigen o Known antigen is adsorbed to the surface of a well and mixed with unknown antibody o If an Ag-Ab complex forms, an added indicator antibody will bind and produce a color change o Common test used for antibody screening for HIV o Because false positives can occur, a verification test with other methods may be necessary Direct ELISA o Detects antigens based on binding to a known antibody o Known antibody is adsorbed to the bottom of a well and incubated with an unknown antigen o If an Ag-Ab complex forms, it will attract the indicator antibody and color will develop in these wells
How common is streptococcal meningitis, and what are some virulence factors for Streptococcus pneumoniae? What is used in vaccines for Streptococcus pneumoniae?
¥ Most frequent cause of community-acquired meningitis ¥ 25% of patients with pneumococcal meningitis will also have pneumococcal pneumonia ¥ Most likely to occur in patients with underlying susceptibility Pathogenesis and Virulence Factors ¥ Has a polysaccharide capsule that protects it against phagocytosis ¥ Produces an alpha-hemolysin and hydrogen peroxide that produce damage in the CNS ¥ Capable of inducing brain cell apoptosis ¥ Can penetrate the respiratory mucosa, gain access to the bloodstream, and enter the meninges vaccines ¥ Prevnar: A seven-valent vaccine now recommended as a part of childhood immunizations ¥ Contains capsular polysaccharide components of seven different serovars of Streptococcus pneumoniae Pneumovax 23: 23-valent polysaccharide vaccine for adults
