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NATS 1670 Study Guide - Final Guide: Retrovirus, Adaptive Immune System, Reverse Transcriptase

Natural Science
Course Code
NATS 1670
Motti Anafi
Study Guide

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Why is it so difficult to develop a vaccine against HIV? (reasons are bolded)
Most vaccines work to increase the amount of antibodies in our systems;
antibodies response against HIV is not sufficient in eliminating the virus from
the body
Antibodies seem to be counter-productive; as the amount of antibodies increase,
the amount of helper T cells decrease—having more problems than benefits
Why is there an opposite correlation between higher levels of antibodies against HIV and
the amount of T helper (CD4+) cells in AIDS patients?
Opsonization by Antibodies (Ab)
Can enhance the abilities of neutrophils and macrophages by binding to the
pathogens with their Fc receptors
This is not a very good idea—recall that macrophages can be infected and
transmit the disease throughout the body
Infection of macrophages by HIV may be enhanced by antibodies against the
-HIV survives in macrophages
-Antibodies response against the virus is counter-productive; the virus is
opsonized by anti-gp120 antibodies that bind to macrophage Fc receptors
This appears to be the problem with the development of HIV vaccines
High mutations rate of RNA Viruses
HIV is a retrovirus
Retroviruses use their reverse transcriptase to replicate their genome (using RNA
to make DNA)
Reverse transcriptase does not have proof-reading material—therefore, it does not
care about making an exact duplicate or checking for accuracy
-High error rate
-1 error in every 5,000 nucleotides
HIV genome has approximately 10,000 nucleotides
Therefore every new virus has (on average) two mutations
The HIV that infects patients is very different from the HIV that is seen by the
time AIDS appears
Acquired immunity and vaccine problem
Infection specific immunity (no disease) AIDS disease
Likewise, vaccination specific immunity (no disease) AIDS disease
Therefore, vaccinations are unavailable.
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