Micro Ch 13

Acute infection stage

-1-4 weeks after infection. Severe flu-like symptoms develop, including fever, sore throat, and rash. Symptoms are the body's initial immune response to the virus replicating in the host -At the end of the acute stage, the immune system won and the virus is no longer causing symptoms of disease; but the virus is still present

-Approximately how many people around the world were living with HIV in 2013? -Which continent is most affected?

-35 million -Subsaharan Africa

-Bacteriophages are capable of infecting all types of bacteria. An enormous variety of different phages exist, but we will only talk about lytic phages. -What is a lytic phage? -What is the model virus for this type of phage? -What does that virus target and how long does the infection process take?

-A lytic phage is a virus that exits a host bacterial cell by lysing (destroying) the infected cell -T4 phage is the most studied lytic phage -Targets Escherichia coli -Infection process takes ~30 minutes

-The relationship between viruses and their animal hosts can be divided into two major categories of infections: -acute and persistent. -Including viral examples, distinguish between acute and persistent viral infections. -What is Chickenpox an example of?

-Acute infections are characterized by a sudden onset of symptoms but symptoms last for a short period of time -Examples include cold and the flu -Persistent infections can continue with or without symptoms for years, or even over the entire life of the host -Examples include hepatitis (liver) and herpes -acute virus (shingles is Persistent)

Is it possible to prevent HIV following an exposure? What is the name of the med? How quickly must it be taken?

-After exposure, it is possible to prevent an HIV infection by taking post-exposure prophylaxis (PEP) medication -PEP also consists of Truvada -Needs to be taken within 72 hours of potential exposure to HIV -PEP medication is similar to HAART and is very effective at preventing infection if taken early enough

-We talked about 3 cold facts. Explain those facts. -What other human pathogen can mimic symptoms of a cold?

-Antibiotics are ineffective against the common cold -Being cold does not mean you will develop a cold -The virus not only has to present, but enough of the virus has to be present to cause disease; It takes more than one virus to cause disease -The color of your snot does not tell you if it is a bacterial or viral sinus infection -Clear snot does not mean a viral infection. Just like thick, yellow-green snot doesn't mean a bacterial infection -Mucus gets thick and changes color during an infection because white blood cells in the mucus are dying; making the snot thick and look yellow-green as a result

-Most viruses are extremely small. -About how much smaller than the cells they infect? -What is the size range of viruses? -Be sure to include examples of viruses on each end.

-Approximately 100-1,000 times smaller than the cells they infect -About 100x smaller than the bacteria they infect -About 1000x smaller than the animal cells they infect -Smallest viruses are about 10 nm; Rhinovirus, which is the most common cause of the cold, are about this size -Largest viruses can get up to 800 nm; Mimivirus is a giant virus that infects protozoans

-Viruses must have protein structures for host attachment. -Why are they necessary? -How do phage and animal viruses attach to a cell? -Be able to visualize the differences in structure.

-Attachment is essential for the virus to invade a cell and initiate infection -Animal viruses have spikes for attachment -Phages have tail fibers -Tail is used for transmission

-During release, lytic phages burst out of the infected cell. -What is the burst size of the T4 phage? -After bursting, how does the T4 phage find other bacteria to infect?

-Burst size of T4 is about 200 new viruses -Random collision

-How is the cold typically transmitted? -The common cold is more common during the winter months. -What are some reasons that may help explain this?

-Can be transmitted through sneezing, but mostly commonly through direct contact with nasal secretions that have contaminated a surface (doorknob, computer mouse) -People are more likely to be indoors and in close contact with one another -Cold, dry air keeps the virus suspended in air longer -Low vitamin D levels suppresses your immune system

-Chickenpox and shingles are caused by the same virus, varicella zoster virus (VZV). -What are the general skin symptoms of each disease? -Where does VZV hide after causing chickenpox? -How does that impact where shingles symptoms develop?

-Chickenpox is the initial, acute infection and shows up all over the body as pimple-like rashes -Shingles is the later, latent manifestation of the virus that shows up on distinct regions of the body -Rare. Most people never get shingles, and the virus stays hidden forever

-Persistent infections can further be broken down into chronic or latent infections. -Including viral examples, how are latent viral infections different from chronic infections?

-Chronic infections are characterized by the continuous production of low levels of virus -Hepatitis -In latent infections the virus remains silent within a host cell, but can reactivate later to cause an infection' for example, if the host becomes immunocompromised -It's why they say Herpes is forever, because the virus lays dormant in your nervous system -The chickenpox virus also hides in the nervous system and can later manifest itself as shingles

-After initial infection, when do cold symptoms arise? -What are the symptoms associated with the cold? -When do symptoms typically resolve?

-Cold symptoms begin 1 to 2 days after infection -Symptoms usually start with a sore throat, and progresses to involve coughing, runny nose, and sneezing -Symptoms typically goes away in 7-14 days

Distinguish between how an enveloped virus and naked virus exits a host animal cell.

-Enveloped viruses are released via budding -Enveloped viruses don't kill the cell, allowing for continuous production of virus by host cell -Non-enveloped viruses are typically released when the host cell ruptures

-Don't forget, AIDS is a stage of an HIV infection. There is no such thing as the AIDS virus! The HIV virus doesn't kill you. The immune system becomes so weak that other microbes (viral, fungal, bacterial) kill you. -The immune system becomes so weak that other microbes (viral, Know general information with regards to HIV transmission. -HIV cannot survive for long when outside of a host. Why not? -What are some ways of HIV transmission? -What are ways that HIV cannot be transmitted?

-HIV is completely destroyed within hours -It's not a living thing; it doesn't form cysts or endospores to protect itself -Sexual contact -Mother to fetus -Blood-contaminated needles -Blood transfusion

-HIV must attach to cells in order to infect them. -How does HIV attach and what does it attach to? -Once HIV has invaded, it releases three enzymes that are essential for infection to occur. -Know the role of those three enzymes. -How does HIV exit an infected cell?

-HIV uses its spikes to attach to CD4 receptors located on our immune cells -Once HIV has invaded an immune cell, it releases three enzymes that are essential for infection to occur: -HIV has an RNA genome that is converted into DNA via reverse transcriptase -The viral DNA is incorporated into the host chromosomes via integrase -Uses a protease to fully assemble virus prior to its release via budding -Envelope budding

-Some animal viruses have the ability to permanently integrate their DNA into our chromosomes. -What are two familiar examples of viral pathogens that are able to do this? -What does HIV use to permanently integrate its DNA into our chromosomes?

-HIV, Herpes -uses its integrase enzyme to permanently embed its DNA

-With proper HAART treatment, HIV-positive individuals never develop AIDS and have barely detectable levels of HIV in the blood. -They can lead just as normal a life as an HIV-negative person. -What does HAART stand for and how does it attack the virus?

-Highly Active AntiRetroviral Therapy -Is an anti-HIV combination therapy that attacks HIV in multiple ways -HAART contains drugs that stops attachment, conversion of RNA to DNA, integration of the viral DNA genome, and protease activity

clinical latency stage

-If HIV is untreated, the virus is slowly growing and also killing CD4 immune cells in the process. However, the host is usually asymptomatic at this stage -Latency starts after symptoms from acute stage go away and can last though the lifespan of the host

Lytic phage Synthesis of viral proteins and replication of the genome

-Phage DNA is transcribed and translated into viral proteins by the host cell -Phage DNA is copied and replicated by the host cell

-It is possible to prevent an HIV infection if caught early enough. -What is the name of the medication that can prevent infection? -When do you need to take it by? -What does the medication consist of?

-Pre-exposure prophylaxis (PrEP) is an anti-HIV medication that prevents a person from becoming infected with HIV -Federal guidelines recommend that PrEP be considered for people who are HIV-negative and in an ongoing sexual relationship with an HIV-positive partner -Truvada is the major PrEP drug prescribed Truvada is also used with HAART medication Daily PrEP reduces the risk of getting HIV from sex by more than 90%

-The common cold is the most common viral infectious disease in humans. -Where does the virus primarily cause disease? -The common cold is caused by a collection of over 200 viral species. -Which virus is most likely to cause your cold? -The average adult contracts 2-3 colds per year. -Does that mean every adult gets 2-3 colds per year?

-Primarily a disease of the upper respiratory tract -Rhinoviruses are enveloped viruses that are the most common cause of the cold -Some people almost never catch a cold, others catch it more frequently

-All viruses consist of a nucleic surrounded by a protein coat. What is that protein coat called? -What is its function? -What types of nucleic acid can a virus contain? -Why is the nucleic acid important? -Distinguish between an enveloped and non-enveloped virus.

-Protein coat is called the capsid (or head) and its purpose is to protect the genetic information from the environment -The nucleic acid can be either DNA or RNA, and contains essential genetic information of the virus -enveloped viruses that have a lipid bilayer envelope that surrounds the capsid; Typically found in animal viruses -Non-enveloped viruses lack an envelope and are said to be naked

-Rhinovirus attaches to a highly specific receptor on host cells, which is why it doesn't attack all cells in our body. -What is that receptor and where can it be found? -Your immune system's inflammatory response to the virus is what causes symptoms of disease. -Why do you get cold symptoms? -Why is it evolutionary advantageous for the Rhinovirus to cause a runny nose?

-Rhinovirus binds to the ICAM-1 receptor present on your upper respiratory cells -Rhinovirus binding and subsequent invasion activates your inflammatory response -Cold symptoms are a result of your body's immunity trying to expel the virus -Makes it easier to spread the virus around

-Ancient viruses are buried in your DNA. -Approximately what percentage of your genome is actually viral DNA?

-Scientists estimate that 8% of our DNA (genome) is actually viral DNA

-Animal viruses have a similar replication cycle to bacteriophages. -What is the primary difference between the two? -Why is it important to know the animal virus life cycle?

-The major difference is how they exit an infected cell -Allows us to treat them

-Know general statistics with regards to HIV in the United States. -Approximately 1.2 million people living in the US are HIV-positive. -How does that compare to the US population? -Per year, how many people in the US die from AIDS-related complications? -Has the death rate improved over the past decades?

-US population in 2017 was 324 million. (0.4% HIV-positive) -Approximately 20,000 people die from AIDS-related complications every year -Death rate has declined since the 90's due to better treatment

Acquired Immunodeficiency Syndrome (AIDS) stage

-Untreated, advanced stage of an HIV infection. Can take many years to develop. AIDS is diagnosed when the CD4 cells in the blood drop to a dangerously low level -The immune system is badly damaged because HIV is killing so many immune cells. The body is now more vulnerable to pathogens and susceptible to developing cancers

-What is a virus? Can viruses make more viruses? -What types of life are viruses capable of infecting?

-a small, infectious agent that only replicates inside living cells -Viruses are not classified as living things, therefore they are dependent on a living cell in order to make more copies of the virus -Viruses can infect all life on this planet -Animal viruses infect animals -Plant viruses infect plants -Bacteriophages (phages) specifically infect bacteria

-What is the purpose of a "pox party"? -It is not recommended! There are chickenpox vaccines available.

-deliberately infect other children with chickenpox for kids to "get it over with

-Have a general understanding of the Human Immunodeficiency Virus (HIV). -What type of virus is it, what does it target, and which animal is the primary carrier? -Approximately when do scientists believe HIV originated in humans? Where? How? -How does HIV kill? HIV is now classified as a pandemic, what does pandemic mean?

-enveloped RNA virus that primarily attacks our immune system -Humans are the main carrier of HIV; there are no other animal hosts -It crossed the species barrier from chimpanzees to humans (from Simian Immunodeficiency Virus (SIV) to HIV) in sub-Saharan Africa between 1884 and 1924 -Transmission is most likely through handling infected chimpanzee meat (food) -HIV is an example of a pandemic -Every continent and country

-While the risk is certainly very real, the odds of contracting HIV (with one exception) are incredibly low. -What are the odds of contracting HIV because of having unprotected sex with a hetero/homosexual partner? -Which risk factor results in the greatest risk of contracting HIV? Why?

-except via infected blood transfusion -there is a 0.05%-0.5% chance of contracting HIV when having hetero/homosexual sex one time with an infected partner -blood transfusion; its direct and large quantity of the virus

-The smallest viruses are about 10 nanometers (nm) in size. -What is 10 nm in micrometers (μm)? In millimeters (mm)?

.000001mm .01um

Lytic phage infection is a 5 step process Have a general understanding of what's happening in each step:

1. Attachment 2. Genome entry 3. Synthesis of viral proteins and replication of the genome 4. Assembly 5. Release

Animal virus infection is a 5-step process. Have a general understanding of what's happening in each step:

1. Attachment of virus to host cell 2. Penetration of virus into host cell 3. Synthesis of viral proteins and replication of the genome 4. New copies of the virus are assembled (put together) 5. Release

-Why might infected animal cells grow more slowly than uninfected animal cells?

ATP is being diverted to produce more viruses and not cell growth

-Be able to describe what is happening in each stage of an HIV infection. -Which stage does death typically result? Why? -How do people die of AIDS? -What is the most common cause of death for people with AIDS? -What is happening to our immune cells as well as the HIV over the course of an untreated HIV infection?

Acquired Immunodeficiency Syndrome (AIDS) stage -The HIV virus doesn't kill a person. With AIDS, the immune system becomes so weak that another pathogen (bacterial, viral, fungal) kills -Bacterial pneumonia is the most likely cause of death for AIDS patients -Mycobacterium tuberculosis -Nasal carriage is a risk factor for Staphylococcus aureus pneumonia in HIV-infected patients

Lytic phage Release

Host cell lyses, releasing many phage into the environment

-Enveloped viruses exit your cell via budding. -While budding, what do enveloped viruses steal from your cell?

Part of the plasma membrane which keeps the virus from being recognized by the immune system.

Lytic phage Attachment

Phage uses tail fibers to attach to specific receptors on bacterial cell wall

Lytic phage Genome entry

Tail of virus contracts and injects its genetic information into the host cell

-Approximately how many bacteriophages reside in our gut? -Why aren't they harmful to us?

The human gut contains about 1015 bacteriophages (that's 1 with 15 zeros after it, or 1 quadrillion!)

Why do we care about how HIV attaches and infects us?

The more we know about it, the better we can treat it

-Bacteriophages only infect bacteria. -Why can't they attach to us to cause infection?

They attach to the cell wall of the bacteria

Lytic phage Assembly

Viral DNA and proteins are put together to make more copies of the phage