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martin2 - Evolutionary origin on HIV z The closest...

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Unformatted text preview: Evolutionary origin on HIV z The closest relatives of HIV-1 and HIV-2 are simian immunodeficiency viruses (SIV). z There is evidence for multiple transmissions from SIV into humans. z HIV-1 is very closely related to SIV from chimpanzees. Evolution of virulence z All SIVs appear to be apathogenic in their natural hosts. z SIV can be transferred to other species, where it induces AIDS. z Short-sighted evolution of virulence. HIV is a quasispecies z Viral replication is error prone. z HIV reverse transcriptase and RNA polymerase have error rates of about 1E-4. z The virus population in any one patient is extremely heterogeneous. z HIV can escape from drug treatment. z HIV can escape from immune responses. Evolution toward disease z Escape from immune responses z Increasing viral diversity z Faster replicating strains Diversity threshold Time Virus load Antigenic variation n i ,..., 1 = virus mutant i immune response against mutant i Each mutant goes to equilibrium: i i i i i i i bx cv x v px rv v- =- = & & p r x cp br v i i = = Add new mutants over time. Antigenic variation Total virus load is proportional to antigenic diversity....
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martin2 - Evolutionary origin on HIV z The closest...

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