Microbiology Chapter 13 + 19: Viruses, HIV

What is the significance of smallpox?

the only disease to ever be completely eradicated (last known case in 1977).

How were we able to eradicate smallpox?

humans are the only natural host; smallpox is not transmitted by insects or animals

How is smallpox prevented?

the only prevention is vaccination, which uses the Vaccinia virus (a related virus).

Causative agent of COVID-19

caused by SARS CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2).

What kind of virus is HIV?

retrovirus

What does it mean for a virus to be a retrovirus?

the virus utilizes Reverse Transcriptase (RT), an enzyme that uses RNA as a template for DNA

How do retroviruses contradict the central dogma of molecular biology?

the central dogma states that DNA is used as a template to be transcribed into RNA which translates into proteins. by using RNA as the template to be transcribed into DNA goes against this.

Describe the structure of a HIV molecule

contains 2 identical strands of RNA, an envelope, and two types of glycoprotein (GP) spikes

What are the two types of glycoprotein spikes found on HIV?

gp120, gp41

What is the primary target cell for HIV?

CD4+ T helper cells, which are infected and destroyed

What is the function of the glycoprotein spikes in HIV?

the spikes bind to receptors on the CD4+ T helper cells and the coreceptors CCR5 and CXCR4

What is the function of reverse transcriptase (RT) during HIV pathogenesis?

during synthesis, RT utilizes the ssRNA template to create dsDNA

Why is reverse transcriptase so harmful?

the process is error-prone and lacks proofreading, resulting in PERMANENT mutations which allow the virus to constantly change

What is the function of integrase during HIV pathogenesis?

integrates the dsDNA into the host cell DNA.

Definition of provirus

the integrated viral DNA that remains hidden and protected (latent) within the host cell DNA. it replicates whenever the cell replicates, making the virus part of the host's DNA for life.

What is the function of protease during HIV pathogenesis?

required during assembly/maturation to cleave polypeptides, releasing the capsid and RT

Why is protease important in HIV pathogenesis?

this enzyme is required for the final activation of the mature virion

How is HIV released?

mature virus leaves by budding and acquires an envelope and attachment spikes. this doesn't immediately kill the host cell, allowing the cell to keep producing viruses

What does the acronym AIDS stand for?

Acquired Immunodeficiency Syndrome

What is the clinical definition of AIDS?

clinically defined as having 200 CD4+ T cells/µL blood

What are the suspected causes of AIDS development?

direct viral destruction by HIV and the T cells becoming so overworked thart the lifespan is shortened

What are the primary transmission routes of HIV?

sexual intercourse, blood, and mother-to-child (during pregnancy, delivery, or breastmilk)

What are not considered routes of HIV transmission? Why?

saliva, tears, sweat, and urine are not considered sources of infection because the virus exists in low quantities

How is HIV diagnosed?

viral testing is based on detecting antibodies (Abs). testing too early can lead to false negatives

Can HIV be cured?

no, only managed

How can HIV be managed?

reverse transcriptase inhibitors, cell entry inhibitors, integrase inhibitors, and protease inhibitors

What is HAART?

Highly Active Anti-Retroviral Therapy; involves a cocktail of multiple drugs to slow progression

Function of reverse transcriptase inhibitors

synthetic nucleoside analogs that function as "chain terminators" to terminate viral replication

Name two examples of RT inhibitors

Azidothymidine (AZT), Epivir (3TC)

Function of cell entry inhibitors

targets gp41 or CCR5

Function of integrase inhibitors

inhibits the integration of ds viral DNA into the host DNA

Function of protease inhibitors

prevents the action of HIV protease, which is required for viral assembly and maturation

PrEP (Pre-exposure prophylaxis)

a once daily pill for HIV negative individuals that contains 2 RT inhibitors. it can reduce the risk of HIV from sex by 99%

PEP (Post-exposure prophylaxis)

antiretrovirals taken after a potential exposure to HIV; must be taken within 72 hours