Virology - Exam 3
What is an incubation period? How is it different for different viruses?
- initial period before symptoms of disease are obvious - viral genomes are replicating - host is responding -virus may or may not be transmitted (A short incubation time means the virus doesn't need to travel to cause symptoms - doesn't need to travel far to its site where it is able to produce symptoms)
What are the characteristics of acute infections?
- rapid onset of viral reproduction - short but possibly severe course of disease - production of large numbers of virus particles - immune clearance Ex.) Rhinovirus, Rotavirus, Influenza virus
How do viruses spread through nerves? capillaries?
. Neural spread. Virus reproduction usually occurs first in a no neuronal cells (because they divide until neural cells) then they spread through afferent (sensory) or efferent (motor) nerve fibers. Ex) Polio enters nerves through muscles and herpes virus enters via epithelium to sensory neurons. Virus spread through nerves through retrograde (viral uptake at the end of the neural cells, moves along the axon using motor protein: dyne, replicate in the cell body and shed). Viruses also spread through Anterograde which is the uptake and replication in the neuron cell body, spread and release at the end of the neural cell, motor protein; kinesis. Capillaries: basement membrane and pericyte
What components are needed to grow cells in culture?
1. A balanced salt solution 2. A buffering system for correct pH and osmolality 3. An energy source 4. Essential Amino Acids 5. Vitamins 6. Antibiotics 7. FBS 8. Serum
What are the main strategies of making vaccines?
1. Attenuation (replication competent natural virus vaccine) 2. Inactivation (inactivated virus vaccine) 3. Fractionation (nonrecombinant, purified subunit vaccine 4. Cloning -> cloning like replication competentvirus vector vaccine, mRNA vaccine (SARS CoV-2), DNA vaccine); expression (protein, virus-like particle).
What two factors influence herd immunity?
1. Depends on the type of the virus (its R0) - the threshold is virus 2. Population specific
What are the common symptoms of COVID19?
1. Dry cough 2. Tiredness 3. High fever 4. Difficulty breathing
What are the two main components of viral disease?
1. Effects of viral replication on the host 2. Effects of host response on virus and host
What are three requirements for a successful infection?
1. Enough Virus - proper concentration, environment that maintain vision stability (water, air). Mosquito transmitted virus highly concentrated, protected from environment 2. Cells accessible, susceptible (receptors for entry), permissive (contain intracellular gene products needed for viral reproduction 3. Local antiviral defense absent or overcome
What are the characteristics of cells that undergo transformation?
1. Immortal: Grow indefinitely (HeLa) 2. Loss of anchorage dependence 3.Loss of contact inhibition 4. Colony formation in semi-solid media 5. Decreased requirements for growth factors (serum)
What are the requirements of an effective vaccine?
1. Induction of an appropraite immune response (Th1 vs Th2 response - helper T cells). 2. Vaccinated individual must be protected against disease caused by a virulent form of a specific pathogen (just getting 'a response' is not enough (e.g. producing antibodies). APC - antigen presenting cell Requirments: 1. Safety: no disease, minimal side effects 2. Induce protective immunity in the population 3. Protection must be long-lasting 4. Low cost: genetic stability; storage considerations; delivery (oral vs. needle)
How do persistent infections are established (4 mechanisms)?
1. Modulation of immune response (CTLs): infected cell displays processed viral product via major histocompatibility complex I (MHC Class I); Antigen presentation by MHC proteins is essential for adaptive immunity. Cytotoxic T lymphocyte recognizes the infected cell and starts neutralizing it. Main intervention route during persistent infections is the modulation of the cytotoxic T lymphocyte response 2. CTL escape mutants ex.) herpes simplex virus, hepatitis C virus. It is a mutated viral peptide no longer "fits" on MHCI complex or prevents association of MHC I with CTL. Changes may also affect proteasomal processing. 3. Unexpected turn of events: CTL dies! On a surface of CTLs there are variety of receptors, i.e., Tnf, Fas, Apo2D. Activated CTLs have membrane receptors Fas that normally bind FasL (ligand) on infected cells. Viruses induce overexpression of FasL by infected cells (too much ligand). FasL binds in great amounts to CTLs which triggers CTLs apoptosis (system overload). This is a normal cellular pathways that exists to limit the overproduction of T cells. Another example of viral defense. 4. Some organs have limited immune surveillance. Immune-privileged niches: CNS, vitreous humor of eye, areas of lymphoid drainage devoid of initiators and effectors of immune response (eye, high FasL); could be damaged by fluid accumulation, swelling, and ionic imbalances of inflammation; persistent infections of these tissues are common.
What are the two examples of natural passive vaccine?
1. Natural passive vaccine is passed on from mother to child during birth. Natural passive vaccine is included in mother's milk. (Ex. colostrum)
What are the two basic systems for growing cells in culture?
1. Suspension cells: generally from the blood/lymph system; immortalized lines may come from leukemia or lymphoma; small and round to move easily throughout the vein/capillary/arterial and lymph systems. 2. Adherent cells: generally from sold tissue (kidney, brain, lungs); categorized as endothelial, fibroblasts or epithelial cells but sometimes origin is unknown; immortalized with SV40 large T antigen or cancer cells; primary cells can be isolated and kept in culture for several weeks.
Why virologists use cell culture?
1. study the infectious cycle 2. cultivation of virus for vaccine production
What is Prodrome?
A period of symptoms before those characteristic of disease. Incubation period of influenza (1-2 days), HIV (8-21 days), Papilloma (warts) (50-150 days)
What two viruses cause liver damage through persistent infection? What is the molecular difference (genome) between them?
ATL and CTL's from chronic HBV. Hepatitis C (HCV) is when during acute infection you have increase in ALT, then you get gaundis. Then it moves too persistent. via multiple immune modulation mechanisms. Molecular difference is HBV is DNA and HCV is RNA virus.
What is tissue tropism? How can you explain that phenomenon on the example of influenza?
Ability of virus to infect a given tissue. Why the virus can enter the given tissue and replicate there. (susceptible and permissive) The spectrum of tissues infected by a virus ranges from limited to pan tropic (affecting various tissues without showing special affinity for one of them). The basis for tropism: cellular receptors; transcription factors (some enhance elements only work for specific cell transcriptional factors (HBV in liver, Papiloma 11 in keratinocytes); Cellular proteases (presence of cellular protease necessary to cleave viral proteins to mature viruses e.g. influenza HA and tryptase Clara. Most influenza virus enter respiratory track and stay there replacing in club cells which secrete tryptase Clara (protease), cleaves the HAD, thereby rending virus infectious. Only club cells release that tryptase. Cleavage of HA determines the tropism of influenza virus. Avian influenza (H5N1) infect many organs: has multiple basic amino acids close to the fusion peptide, which allows it to be cleave by furins - which are present in all cells. SARs CoV-2 spike is also cleave by furins.
What are active and passive vaccines, know examples
Active - instilling into the recipient a modified form of the pathogen or material derived from it that induces immunity to disease (long term protection) attenuated. Passive - instilling the products of theimmune response (antibodies or immune cells) into the recipient (short term protection, short half life of products. Ex. rabies post exposure vaccine includes human immunoglobulin, injected at the bite site and that prevents spread of virus). Example of passive vaccine: Zmapp.
What is the difference between acute and persistant infections?
Acute infection - rapid and self-limiting; Persistent infection - long term, life of host; stable characteristic of each virus; most persistent infections probably begin as acute infection. Some persistent infections cause no symptoms, i.e. herpesvirus (acute and persistent)
What is acyclovir? Symmetrel?
Acyclovir is a highly effective, anti-herpes simplex virus drug. It is a nuceloside analog. (guanosine). Incorporated into a growing chain of replicating genome, stops DNA polymerase. It does not have the available 3' OH group to continue the synthesis. Symmetrel (Amantadine) interacts with influenza viral M2 protein (ion channel). Blocks entry of protons into virion, prevents uncoating
How is SARS- Covid 2 related to earlier MERS and SARS outbreaks?
All of those viruses impact the respiratory system
Which of the following do acute infections and incubation periods have in common? A. The virus is not replicating B. No symptoms are visible C. Immune defenses are engaged D. The immune system does not respond E. All of the above
C. Immune defenses are engaged
In general, secondary viremia is a consequence of which of the following events? A. Viral replication in the bloodstream B. Viral replication at the original site of entry C. Viral replication in organs distal to the site of entry D. Viral replication in lymph nodes E. All of the above
C. Viral replication in organs distal to the site of entry
What is cascade regulation of gene expression? Recall the role of VP16 protein
Cascade regulation is when a product initiation a reaction down the line and that product does the same and it facilitates transcription. VP16 activate immediate early promotors and HSV
What are CTL? What is MHC 1 system?
Cytotoxic T lymphocyte which recognizes the infected cell and starts neutralizing it. The MHC I (major histocompatibility complex 1) is necessary for adaptive immunity. When a cell is infected your sent their DNA to MHC 1 to signal that they are infected. MHC 1 is an antigen presenting protein that presents a piece of pathogenic product so it is recognized by immune cells. From here, a viral peptide will attach and a CTL will start killing the infected cell.
Which are shared features of persistent infections with polyomavirus, HBV, and HCV? A. Genomes are present but not expressed B. Liver damage C. Kidney damage D. Virus particles are produced E. All of the above
D. Virus particles are produced
The outer layer of which of the following is dead but can still serve as a portal of virus entry? A. respiratory tract B. alimentary tract C. eye D. skin E. urogenital tract
D. skin
What are the main types of transmission?
Direct: person to person, Ex.) STD; droplet spread, coughing, sneezing. Indirect: airborne transmission ex. measles, influenza virus, contaminated objects, animal to person contact (zoonosis), animal reservoirs, ex. WNV; environmental reservoirs
Which of the following are features of persistent infections? A. They last the lifetime of the host B. Viral immune modulation is involved C. Immune cells may be infected D. They may occur in areas of reduced immune surveillance E. All of the above
E. All of the above
Which of the following is a good reason to get the measles vaccine? A. There is a 1/000 chance of acute post-infection encephalitis B. There is 1-2/1000 chance of death from measles C. Each infected person spreads measles virus to 15 others D. Immunosuppression can lead to secondary infections E. All of the above
E. All of the above
What are some requirements for an effective vaccine? A. low cost B. East of administration C. provides long lasting immunity D. minimal side effects E. all of the above
E. all of the above
What herpesviruses attach their episomes to human chromosomes?
EBV, VZV,
What is the purpose of using Trypsin/EDTA in cell culture?
EDTA chelates Calcium which is required by attachment factors. Trypsin is a serine protease that cleaves attachment factors (cell adhesion molecules (selections, interns, adherins) on cells that bind charged polystyrene or coating (fibronectin, vitronectin). When passaging cells it is critical to inspect the flask to ensure that all cells are detached. Failure to move all cells will result in population selection
True or False: Ebola virus consists of single stranded, positive sense RNA
False: Ebola is single stranded, negative sense RNA
How does geography and season shape viral infections? And how can viruses overcome these limitations?
Geography may restrict presence of virus because there is a requirement for specific vector or animal reservoir. However, they can have mutations in their amino acids that can change their tropism for the vector. Seasonality is where you seen outbreaks during certain times of the year because of changes in seasons. Seasonality creates viral stability and host mucosal surfaces are thinner during winter. It is seen that viral infections go down as temperature goes up and moisture is less
What herpesviruses integrate their genome to human chromsomes?
HHV-6
What HIV enzyme are effectively targeted with antivirals?
HIV protease: it recognizes and cleaves small synthetic peptides.
What types of HSV exist and what organs do they infect?
HSV-1, HSV-2 (type 1: oral (skin - lips), type 2: genital)
What are the main types of spread of infection?
Hematogenous (spread of infection through the bloodstream) and Neural spread (spread from the primary site of infection by entering local nerve endings)
What immunoglobulins are produce first in response to viral infection? Which immunoglobulins are produced in response to persistent infection later?
IgM first; IgG later
What are inactivated vaccines?
Inactivated virus vaccine. This means that its infectivity (ability to cause the disease) is eliminated, but its antigenicity (ability to induce and maintain immune response) is not compromised. This can be produced through chemical procedures
Know the symptoms, sites of entry, viral replication, complications, and prevention influenza virus
Influenza: enters the respiratory tract, replicates in upper respiratory tract (nasopharynx, epithelial cells), spreads all down in the respiratory tract, trachea, bronchi, aveola (viral bronchitis), for the most part does not spread systemically (rarely). Its incubation period is 1-5 days, depending on dose, immune status of host, abrupt onset: headache, chills, dry cough; High fever, myalgias, malaise, anorexia, fevers peaks within 24hr, 38-40 degrees celsius, fever declines day 2-3, respiratory signs intensify, cough changes from dry to productive, cough, weakness can persist 1-2 weeks. You diagnosis influenza if you have an influenza-like illness, ILI; fever at least 100 degrees Faherenheit, cough or sore throat. Your symptoms are delayed by 1-3 days, virus replication goes down before your antibody response kicks in (they are not helping much, besides making you feel miserable). Some complications of influenza are primary viral pneumonia, secondary bacterial pneumonia, myositis - generalized muscle pain, cardiac involvement, Reye syndrome (encephalopathy, liver damage). Some interventions for influenza are non-pharmaceutical drugs, antiviral drugs like Tamiflu (oselatamivir), Relenza (zanamavir), Flumadine (rimantadine), Baloxavir, and Vaccines. Symptoms: dry to productive cough, weakness, fever, chills, headache; Site of entry: enters respiratory tract Viral replication: upper respiratory tract; complications: primary viral pneumonia, secondary bacterial pneumonia, myositis; Prevention: tamiflu, vaccines, baloxavir
What is BSL-4 lab, and what risk drops when we work in such laboratory set up? (know examples)
It is a laboratory that provides the top level of security. It allows science to handle pathogens of the highest risk group 4: when you work with a pathogen that usually causes serious human or animal disease and that can be readily transmitted from one individual to another, directly or indirectly. Effective treatment and preventative measures are not usually available. BSL-4 is designed to diagnose and investigate these types of pathogen without endangering the staff or the population at large. Across the globe there are several dozen BSL-4 laboratories. From examples of BSL-4 viruses are ebola and smallpox
What do you know about the genomic characterization and classification of the virus?
It is positive sense single strand RNA virus. It has S, HE, M, E, N glycoproteins. It has spike proteins that are variable and responsible for attachment and present for different strains
Know the symptoms, sites of entry, viral replication, complications, and prevention measures related to the norovirus.
It's scientific name is Caliciviridae, (+) strand RNA virus, cause 50% of all food-borne outbreaks of gastroenteritis (23 million/yr US); it is fecal-oral spread; retain infectivity passing through stomach; blunting of villi in proximal jejunum; basis for vomiting, diarrhea not known; Virus binds to carbohydrates that are present in bacterial cell wall. Bacteria get trans-cytosed across M cells that sample the content of gut lumen. Virus ends up in B cells where it replicates. R0 = 18. Transmission is fecal-oral; aerosol-vomitus; contact with fomites; food, water, or environmental contamination; foods can be contaminated at the source (oysters, raspberries) or during preparation by food handler. Incubation period 10-51 hr. Symptoms: sudden onset of vomiting (more common in children), diarrhea (more common in adults), stomach pain; Duration of illness: 28-60 hr; longer in immunocompromised or with underlying illness; 30% asymptomatic infections. Viral shedding peaks 1-3 days after illness onset, may persist for 56 days; immunity: short term homologous only; reinfection with other strains may occur or later in life; Reservoir: humans, but evidence for animal reservoir; affects all ages; year round, peaks in cold weather; outbreaks often occur in semi-closed environments (nursing homes, hospitals cruise ships), military schools, recreational activities (sports events, camping trips, travel) that favor person to person spread). Symptoms: vomiting, diarrhea; Site of entry: mouth: Replication: B cells in gut lumen; Complications: fatigue, dehydration; Prevention: wash hands, avoid contaminated food, wash fruits and veggies before eating.
Know the symptoms, sites of entry, viral replication, complications, and prevention measures related to the measles virus.
Measles virus is also known as Paramyxoviridae, It is one of the most contagious human viruses (R0 = 15). If you get it, you can get it again. Transmitted by inhalation of respiratory secretions, period of maximum contagiousness 2-3 days before rash, nearly all infected individuals show signs of disease. It enters the body when it is inhaled by upper respiratory tract. The apical surface of the respiratory epithelium doesn't have proper viral receptors, so the virus enters through macrophages that are patrolling respiratory epithelium. The virus spreads to multiple organs including skin (rash), and brain (rare). Virus is shed through basolateral surface of epithelium (receptors are present). Basolateral surface of epithelium site of replication? When you have measles you generally have a fever (38.3 degrees Celsius or above), respiratory symptoms: coryza, cough; conjunctivitis, koplik spots, and rash from face to extremilites. Some complications of measles are acute postinfectious encephalitis (1/1,000), bronchitis, pneumonia, ear infection; fatality (1-2/1000) (28% poor nutrition), subacute sclerosing panencephalitis (SSPE), immunosuppression leading to secondary infections (main cause of death in Third World children). In the US: 3-4 million/year, 400-500 deaths, 48,000 hospitalizations, 1,000 chronic disability from encephalitis; endemic transmission stopped 2000 by vaccine, MMR: measles, mumps rubella vaccine; Wakefield 19998 report lead to decreased MMR immunization, outbreaks in UK, Ireland; US outbreaks, imported. In a 24 hour period...about 200,000,000 people have gastroenteritis. The amount of diarrheal water passed equals the volume of water passing over Victoria Falls in 1 minute. Symptoms: cough, rash; Site of entry: inhaled by upper respiratory tract, enters through macrophages; Site of replication: organs (skin)/(brain - rare); Complications: acute post infectious encephalitis, bronchitis, pneumonia; Prevention: vaccines - MMR; Released through basolateral surfae of epithelium; R0 = 15
Are all neuroinvasive viruses also neurovirulent?
Neuroinvasive means a virus can enter the CNS after infection of a peripheral site. Neurovirulent mean the virus can cause disease of nervous tissue. Not all neuroinvasive viruses can cause disease in the CNS. Ex.) HSV: low neuroinvasiveness, high neurovirulence; Mumps: high neuroinvasivenss, low neurovirulence; Rabies: high neuroinvasiveness, high neurovirulence
Can ebola virus be spread through airborne droplets?
No
Are all inapparaent infections also acute?
No because being acute means you have the virus for a short bit and then it goes away. An example of when a virus is persistant, but you don't show symptoms is Herpes or the beginning stages of HIV. Some characteristics of inapparent but acute infections are: - successful infections, no symptoms or disease - sufficient virus particiles produced to spread in the population - >90% of poliovirus infections inapparent
Are all inapparent infections are persistent?
No because some are inapparent and acute; Ex. Herpesvirus
Are polyomaviruses dangerous?
Not really, they cause persistent, but frequent inapparent infections. This virus can cause disease, but mainly in immunocompromised patients.
Know the symptoms, sites of entry, viral replication, complications, and prevention measures polio virus.
Polio virus is ingested with fecally-contaiminated material. It goes to digestive track, passes through stomach, intestines, replicates in intestinal cells (muscosal surfaces); site of entry: mouth; can spread into a spinal cord and brain (rare event, 1%, CNS is a dead-end for most viruses). Humans are the only know reservoir, It is spread by fecal-oral transmission, it peaks during warm months in temperate climates, complication: post-polio syndrome (30-40 year interval; 25-40%, not an infectious process). The virus was most present between 1950's and 1960's. By the start of the 1960's a live oral vaccine was created. Symptoms: fever, back pain or stiffness, fatigue; Site of entry: mouth; Replication: intestinal cells (muscosal surfaces); Complications: paralysis, respiratory failure: Prevention: Vaccine
What types of cells are important for EBV latency?
Primary site of infection is in mucosal epithelial cells. Then through transmission to B cells, the virus enters the blood. Viral DNA is self-replicating episome, associates with nucleosomes in B cells. They produce limited repertoire of viral genes. B cells home to bone marrow and lymphoid organs. They are not killed by CTLs or antibody unless reactivation occurs (modulation of MHC)
What technologies are used for antiviral discovery?
Recombinant DNA technology & sophisticated chemistry make targeted discovery possible. Essential viral genes cloned, expressed in genetically tractable organisms, purified, analyzed in atomic detail; life cycles of most viruses known, targets for intervention can be generalized, modern technology allows inhibitors to be found even for viruses that cannot be propagated in cell culture; blind screening procedures are dead
What are the characteristics of main sites of entry for viruses, i.e., skin, mucosal surface, alimentary track, eye, urogenital track, mother-fetus entry?
Skin: the strongest barrier to infection, the outer layer (stratum corneum) is dead, so nothing can replicate in it, the barrier is compromised by cuts, scrapes Respiratory Tract - Mucosal surface: number one site of entry, lined by living cells, covered in mucus, moist, combined surface of human lung is 30-50 m^2 the size of a studio apartment) and you bring in 6 liters of new air (potentially containing infectious agents) every minute. Some mechanical barriers are: ciliated cells, mucus-secreting goblet cells, subepithelial muscus-secreting glands. Bronchopneumonia can cause SARS and MERS. Alimentary (intestinal) tract: Main symptom: diarrhea Physical barriers: saliva (lysozyme destabilizes viral particles, IgA antibodies), stomach pH, intestine alkaline environment; proteases, mucus lines the entire tract, M cells (thin cells camping antigen content of intestines, virus can enter through them), intestines covered with symbiotic bacteria that impose a formidable barrier for virus particles Urogenital tract: protected by mucus, low pH, co-infection because they compromise barriers; sexual activity can virus to enter ex.) HPV, HSV. Eye: sensitive part - epithelia that covers the exposed part of the sclera and forms the sclera and forms the inner surface of the eyelids. Protective barriers: eyelashes and eyebrows, tears contain lysozyme and antibodies. ex.) bleed by adenovirus; other viruses that enter SARS CoV-2; Mother-fetus: Two main routes: transplacental or perinatal infection. Pathogens that infect fetus are called TORCH pathogens: Toxoplasma, rubella, cytomegalovirus, HIV, other (Zika virus)
Know examples of viruses that cause persistent infections. Which of them infect immune cells?
Some Persistent asymptomatic viruses are lymphocytic chorlomeningitis virus and JC virus; some persistent: pathogenic viruses are human immunodeficiency virus; human T-lymphotrophic virus, and measles virus SSPE. Persistent infection: Adenovirus; EBV, *HBV; HCV; * = affects immune cells
What is special about measles virus sites of entry and release when it comes to epithelial cells?
The apical surface of the respiratory epithelium doesn't have proper viral receptors, so the virus enters through macrophages that are patrolling respiratory epithelium and then it enters and go through lymph nodes and then migrates into the blood where it spread to organs. When measles leave (is shred), it is released through basolateral surface of epithelium since there are receptors there (not macrophages)
What is cell confluence?
The number of adherent cells in a culture flask, referring to the proportion of the surface which is covered by cells. For instance, 50% confluence means roughly half of the surface is covered and there is still room for cells to grow. 100 percent confluence means the surface is completely covered by the cells, and no more room is left for the cells to grow as a monolayer.
What are inapparent infections? Know example
They are asymptomatic infections (no symptoms). You can only diagnosis these when you find antibodies against the virus. They take the blood sample and analyze it. Their Infections that have no consequence, because the immune system fights them off. Example) West Nile Virus -> flavivirus, ss(+) RNA virus. It came to U.S. from a person that was traveling from Israel on plane
What is primary cell culture?
They are cells when surgically or enzymatically removed from an organism and placed in suitable culture environment will attach and grow. It has a finite life span (they divide so many times and then they die).
Is there a true treatment for individuals who have been infected with Ebola virus?
They created a preventative vaccine in 2019, but it is only for the Zaire ebolavirus species, but there is not a true treatment.
What are antivirals? Why are there so few of them?
They fight disease when you already have it. They can stop infection once it has started. Most antivirals are developed against viruses that cause persistent infections. Acute infections are difficult to target (short duration of infection, problems with diagnostics)Antiviral drugs are compounds interfering with virus growth can adversely affect the host cell. Some medically important viruses can't be propagated, have no animal model, or are dangerous. A compound must block virus replication completely. Must be potent and selective!
What is continuous cell cultures?
They grow forever. These are cells that undergo transformation. They occur spontaneously or induced virally (large T antigen) or chemically transformed (genotoxic chemicals). Characteristics: smaller, more rounded, less adherent wit a higher nucleus/cytoplasm ratio. Fast growth and have aneuploid chromosome number - ability to grow up to higher cell density; different in phenotypes from donor tissue; stop expressing tissue specific genes
What are immune-privileged organs?
They have immune-privileged niches. Some organs that are apart of it are CNS (brain), Testis, Blood-testis barrier, eyes (vitreous humor of eye; areas of lymphoid drainage devoid of initiators and effectors of immune response (eye, high FasL). To prevent swelling, and fluid accumulation, and ionic imbalances of inflammation, these areas have less immune surveillance. As a result, persistent infections of these tissues are common.
What is passive, primary, and secondary viremia? Know the difference
Viremia is the presence of infectious virus particles in the blood. Passive viremia is when particles are introduced into the blood without viral reproduction at the site of entry (needles, inoculum, mosquito). Primary viremia is when progeny virus particles release into the blood after initial reproduction at the site of entry (first time virus particles in blood) Secondary viremia is when the virus particle gets to the blood another time after replicating in another distant organ. This process shows the course of infection overtime
What is systemic infection?
When a virus targets many organs. Ex. SARS Cov-2 it uses ACE2 receptor present in respiratory tract cell lines the guts and blood vessels.
Do you think that current SARS CoV-2 causes viremia and how can you justify your answer?
Yes, because there are reports of GI symptoms and it doesn't make sense for those to not enter the bloodstream and cause damage there. You can see the damage in blood and in distant organs. When symptoms are severe you see septics (infection of entire system) and can see organ failure.
How is ABSL-4 different from BSL-4?
You work with animals. It is more isolated than BSL-4. It is located within BSL-4 for another layer of protection.
How is HSV reactivated?
a small number of neurons in ganglion reactivate; virions appear in mucosal tissue innervated by latently infected ganglia, blisters ensure (not always); this is how infection is transmitted (intimate contact); immune response is too slow (viral antagonism) to prevent shedding. Some reactivate every 2-3 weeks, others never. This reactivation can be triggered by sunburn (UV), physical or emotional stress, nerve damage, hormonal imbalance, steroids. They stimulate production of viral proteins needed to activate viral transcription program. VP6 protein is what causes reactivation.
What is biological safety cabinet, and what is it used for?
an area where you can use aseptically.
What is R0?
an average number of other people you can infect when you carry a virus
adjuvants
are when things are added to vaccine to stimulate inflammation and pain they mimic inflammatory effects and (add to this)
Does measles cause acute or persistent infections?
both
What is transformation?
changes in ability of cells to grow and divide indefinitely. They do not have contact inhibition. Transformation does not equal oncogenesis.
How is ebola virus spread?
direct contact: blood or bodily fluids (urine, saliva, sweat, feces, vomit, breast milk, semen) of person who is sick with Ebola or a person who has recently died from it. You can also become infect through objects like needles and syringes contaminated with the virus or even handling primates or fruit bats who are infected.
What is the reason for the air pressure to be negative in BSL-4, but positive in hazmat suit?
everything is sucked into the lab to prevent things that are spilled from being spread. The positivity is what supplies your air.
What type of protein is crucial for the virus, allowing it to fuse viral and host membranes?
host proteases recognize glycoprotein on virus
What is iatrogenic and nosocomial transmission?
iatrogenic transmission is activity of health care worker leads to infection of patient. Nosocomial transmission is when an individual is infected while in hospital or health care facility
Zmapp
is a passive vaccine. It is raised in mice immunized with virus-like particles. Chimerized into human IgG1 scaffold. Produced in tobacco plants (VLP - virus like particles) Used during 2014-2016 Ebola outbreak. lowers risk of death by about 40%
Know the symptoms, sites of entry, viral replication, complications, and prevention measures related to the West Nile infection
it is a Flaviviridae, isolated 1937, West Nile district of Uganda; absent from Western Hemisphere until 1999, New York isolate identical to virus from Israeli goose; Virus infects hundreds of birds, 37 kinds of mosquitoes, 18 other vertebrates; primary host are birds and mosquitos; accidental hosts are animals and people; WNV are transmitted to humans by Culex mosquito bite, its incubation period is 3-14 days, 20-30% develop flu-like illness called WNV fever; 80%: no symptoms; 1/150 individuals develop neuroinvasive disease; headache, ocular manifestations, muscle weakness, cognitive impairment, polio-like flaccid paralysis, 10% mortality, >50% long term neurological sequelae, It replicates in the cytoplasm of the infected cells. Symptoms: fever, headache, neuroinvasive disease, muscle weakness; Site of entry: skin - mosquito bite; Replication: cytoplasm of infected cells; Complications: neuroinvasive disease, polio like flaccid paralysis, death; Prevention: insect repellant; long sleeves, pain medicine
Why FBS is important for cell culture?
it is used as a growth media. When you start an experiment, you have to choose which FBS is best for your experiment
How large T antigen induces cellular transformation?
perturbation of the retinoblastoma Rb and p53tumor suppressor proteins. This causes the cells to leave G1 phase and enter Ito S phase, which promotes DNA replication. It is capable of inducing the DNA damage response to facilitate replication of viral DNA
What does it mean that Ebola virus is zoonotic?
the first patient becomes infected through contact with an infected animal (fruit bat or primate) and then transmit it to other humans: this type of transmission is called a spillover event
What is pathogenesis?
the process of producing a disease
What is virus shedding?
the release of the virus particles from an infected host to another. It is necessary for maintenance of infection in population. But there are other ways of spreading the infection, mosquito bite, animal bite, needle use. Shedding through coughing and sneezing is not efficient route because those droplets are huge and they fall down, must efficient spreading is talking and breathing because they are small and can spread further
What is herd immunity?
the resistance to the spread of a contagious disease within a population that results if a sufficiently high proportion of individuals are immune to the disease, especially through vaccination. Herd immunity is the maintenance of a critical level of immunity. For this to work not everyone is vaccinated only the majority because not everyone can be vaccinated.
What are hazmat suits, how are they prepared before BSL-4 lab entry?
they are suits you wear in BSL-4 that provide full-body protection ) with positive pressure that comes with own air supply. They are highly specialized, totally encapsulating, industrial protection garments worn only within special biocontainment or maximum containment laboratory facilities. It is air higher and designed for positive pressure to prevent contamination to the wearer even if the suit becomes damaged. When you prepare your suit you blow it up and check for holes and leaks.
What are dunk tanks?
they enable contained transfer of laboratory products through submersion in a decontaminant solution (microchip). Dunk tanks can be fitted with interlocked doors to ensure that containment is maintained even when the dunk tank is empty. A range of fumigation chambers are also available for high-level material decontamination
Why do we have to keep passage number low?
to prevent cells from undergoing genetic drift and other variations.
What is latency?
viral gene products that promote productive replication are not made or found in low concentrations. Cells harboring the latent viral genome are poorly recognized by the immune system. Viral genome persists intact so that productive infection can be initiated to spread infection to new hosts.
What are the main approaches the scientists are taking to develop influenza vaccine?
virus grown in enbryonated chicken eggs, formalin-inactivated or detergent or chemically disrupted virions. Protection correlates with serum antibodies to HA, NA. Vaccine produced in cell culture avoid egg allergies (Flucelvax). Envelope proteins change each year; new strains must be selected in the first few months for manufacture. Use reassortants with most RNA segments from high-yielding strain, HA, NA from selected strain. Although the antigenicity of the HA head varies between HA subtypes, that of the HA stem is highly conserved. Antigens at the stalk of HA vary less. HA is immunosubdominant, most response is to the HA head. M2 - transmembrane protein, proton-selective ion channel. Antibodies against M2 do not interfere with virus entry but prevent virus release and activate effector cells. Since M2 is poorly immunogenic, various strategies such as multimerization, display on virus-like particles or phages, and fusion with a carrier protein or a protein with adjuvant activity are being test to improve the host immune response. Animals vaccinated with M2 were shown to be protected from homologous and heterologous challenge infection.
What does it mean that the virus is neurotropic?
virus that can infect neural cells; infection may occur by neural or hematogenous spread from a peripheral site. They have a tropism toward neural cells
How do we use hemocytomer?
we commonly use them to estimate cell number and determine cell viability. It is a thick glass slide with two counting chambers, one one each side. Each counting chamber has a mirrored surface w/ a 3 x 3 mm grid of 9 counting squares. The chambers have raised slides that will hold a coverslip exactly 0.1 mm above the chamber floor. Each of the 9 counting squares holds a volume of 0.0001 mL. To stain and distinguish between dead and viable cells, the sample is mixed in 1:1 ratio with Trypan blue. When using a hemocytomers. You count a total of 100 cells in 5 different squares. You only count the cells if they overlap with the top or right side of the square. Once you have obtained the Total cell count, you can calculate the cell concentration using Total cell/ml = total cells counted x dilution factor/number of squares x 10,000 cells/mL.
What is localized infection?
when the virus replicates at the site of entry. Ex.) rhinovirus (it spreads within the epithelium and is contained by tissue structure and immune system)
What is dissemination of infection?
when the virus spreads beyond the primary site. So it enters and then spreads to another place and replicates there.
What are subunit vaccines? Know examples. What are their advantages and disadvantages?
when you break a virulent parental virus into parts or you clone a piece of viral gene that express the proteins (subunits) and they can be assembled in virus like particles or studied for a vaccine. How this works is you break virus into components, immunize with purified components or clone viral gene, express in bacteria, yeast, insect cells, cell culture, and purify protein. The antigen is usually a capsid or membrane protein. Example: Shingrix (95% effective vaccine. they use envelope proteins (glycoproteins) on the surface of the envelope); the vaccines for HBC and HPV use glycoproteins for their subunit vaccines and add adjuvants (substances that stimulate immune response - inflammation, pain) Advantages of a modern subunit vaccine: 1. Recombinant DNA technology: fast 2. No viral genomes or infectious virus Disadvantages: 1. Expensive 2. Injected 3. Poor antigenicity (they don't cause much inflammation)
What are attenuated vaccines?
when you have a virulent parentail virus that replicates at a lower level. Viral replication occurs, stimulates immune response. Infection induces mild or inapparent disease, infectious, replication competent vaccine Ex. Flumist
Can viral RNA be targeted with drugs?
yes
What are the rules for cell passaging?
you need to inspect the flask to ensure that all cells are detached. Failure to move all cells will result in population selection. passaging itself is the process of diluting cell number in order to keep cells actively growing.