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BIOL 2299 (100)
Roth Aaron (17)
Lecture 18

BIOL 2299 Lecture 18: Origins of HIV and the Evolution of Resistance to AIDS

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BIOL 2299
Roth Aaron

Origins of HIV and the Evolution of Resistance to AIDS • Hiv adapts not only by positive selection through mutation but also by recombination of segments of its genome in individuals who become multiply infected. • Naturally infected nonhuman primates are relatively resistant to AIDS like disease • HIV-1 evolved from a strain of simian immunodeficiency virus (SIV cpz) within a particular subspecies of the chimpanzee • HIV-2 originated in SIVsm of sooty mangabeys • SIV strains haven’t been able to establish themselves to adapt to humans • Specific properties required for successful cross species transmission and subsequent adaptation necessary for efficient spread within the new host population • One successful: HIV-1 group M with subtypes A to K Origins and Missing Links • HIV Came from chimpanzees (subspecies) • HIV-1 came from SIV cpz, and SIV cpz is a recombinant virus derived from lentiviruses of the red capped mangabey and one or more of the greater spot-nosed monkey lineage or a closely related species Diversity • A complex series of events (for instance adaptations and acquisition of viral regulatory genes) was required for these SIVs to infect humans and sustain infection to transmit it • Different types of HIV groups and subgroup have differences in variants and genetic groups and rates of transmission in different populations • Within the 8 HIV-2 groups, A and B are endemic while others represent single infected persons clustering closely to SIVsm strains – means that important adaptations have been necessary for the virus to acquire the ability to be efficiently transmitted • Recombinant forms- CRFs which have segments of the genome derived from more than one subtype • Subtype C and A are the most worldwide, subtype B was the first to appear in Americas Host-Pathogen Evolution • Modes of transmission: parenteral transmission from bites and wounds, sexual, nonsterile injecting equipment • Subtype C most present in vaginas of infected women • Can be transmission from an asymptomatic infected species • Distinct genetic host factors, linked to relative susceptibility or resistance to aids, influences disease progression • Recently identified genes block or restrict retroviral infections in primates • One of the most important antiviral innate and adaptive immune response of the host post infection are those regulated by specific molecules of the major histocompatibility complex (MHC) • Without vaccines we could evolve and probably adapt to HIV Host Resistance Factors Influencing HIV infection and Progression to AIDS • There is a growing list of 10+
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