Lecture 27 Flashcards
What is HIV, how does it operate and what is a good target for treatment?
HIV is a retrovirus, this means the infection particle is RNA, but this will be converted into double stranded DNA inside the host cell (CD4 T cells) by reverse transcriptase, once this occurs the viral genome will beomce integrated into the host chromosome via integrase, this can then be transcribed into a gag protein, rarely the transcription will not stop at the stop codon at the end of this and will result in a longer protein due to a -1 phase shift (bounces off the stop codon and resumes from one behind), this leads to transcribing of the pol protein. This makes HIV difficult to treat as it will remain dormant until it has a good opportunity to strike. Reverse transcriptase is a good target as normal cells will not use this.
What is the likely origin of HIV?
HIV has not been a human virus for very long, this can be seen as many animals have forms of the IV viruses, but these will not lead to problems unless a species gets the IV virus of another species. The parent strain is most likely to have arisen from africa, with the most likely cause being hunting of chimps as the IV viruses are 300 times more likely to have arisen from blood than from sex. The most likely time period was roughly 1950s in the kongo as the industrial setting, during this period injectable drugs and prostitution might have allowed for the disease to spread in an area which had high potential arisal in the Kongo.
Why could the HIV virus not be caused by the polio vaccine or be man made?
The HIV virus arose before the time of the polio vaccine and is unlikely to be a human construction as the technology was not there at the time.
When did HIV come to notice and why?
HIV came to notice in the early 1960s because of two diseases popping up quite commonly in the USA compared to at the baseline rate. This was because the immune system of the patients was weaker, leading to more opportunistic diseases becoming prevalent, was particularly common in homosexual males.
Why does HIV change its sequence very rapidly?
Reverse transcriptase is an inherently not very careful enzyme as it does not proofread its work. This means retroviruses like HIV will change their DNA sequences very rapidly, with typically several sequences within one individual.
Why is HIV believed to be from chimps and what is the main method of studying HIV?
HIV is believed to be from chimps because their CIV virus is the most common to ours and has very similar components. We can study where it came from and how it has changed by examining the sequence of the HIV genome.
What are the HIV primary groups and what are the major subtypes in the continents?
The HIV virus splits into two groups: HIV-2 (not a large problem, only really found in West Africa, has two subtypes, type B and A) and HIV-1 (The major worldwide problem, main problem group is group M, but there are also the group N and O strains, two chimp strains fall into the HIV-1 type). Of the group M HIV-1 strains subtype B dominates the west, subtype C dominates Africa and Asia, and A dominates central Europe and Russia. As Africa has the most diversity it is likely HIV came from there.
What are the steps of the HIV movement believed to be?
The steps of HIV movement are believed to be:
1. Humans butcher chimpanzees infected with SIV in Cameroon.
2. The virus is carried by people travelling along the river.
3. The virus is carried to Kinshasa where the epidemeic began (Leopoldville).
This is believed to have happened many times, however the affected villages would be unlikely to spread the disease further, with colonialism and industrialisation though, this would have allowed HIV to spread.
