Voelcker Academy

Research Symposium 2011


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Sarina Obeid

The Epigenetic Regulation of CCR5 Expression in Nonhuman Primates

Sarina Obeid

Mentor(s): Dr. Sunil Ahuja

Between humans, chimpanzees, rhesus macaques, and a sooty mangabeys, there are two groups for comparison. The first group is made up of Human and chimpanzees. The second group is made up of rhesus macaques and sooty mangabey.


Chimpanzees and sooty mangabys are considered to be natural host of SIV infection, the simian homolog to HIV. On the other hand, Humans and rhesus macaques are non-natural hosts of HIV/SIV. This means that Humans and rhesus macaques are susceptible to the progression of HIV/SIV infection to Acquired immune deficiency syndrome (AIDS) or its simian equivalent SAIDS, whereas the natural hosts are not.


Natural hosts will acquire the viral infection, but their Peripheral blood (PB) CD4+ T-cell count will remain high and stable compared to non-natural host primate species. Also, they control (keep it low) their viral load or the amount of viral particles in their blood better than non-natural hosts. The mucosa associated lymphoid tissue (MALT) CD4+ that line the gut rapidly decline in both natural and non-natural hosts. This may be associated with the timing (when it happens) and magnitude (how strong) of immune activation. The natural hosts (point at graph of immune activation) show higher magnitude of and greater general activation of the immune system. The non-natural hosts show a lower peak of activation and baseline at nearly null immune activation (means no activation). Some undetermined mechanism that accounts for this difference may provide a reason for why there some primate specie progress to AIDS/SAIDS and others do not.


One possible explanation is that it is some regulatory mechanism of CCR5, which one of the two co-receptors for HIV infection. This receptor has already been shown to be extremely important in HIV resistance and slower progression to AIDS. Naturally, mechanisms that regulate the expression of this receptor are important factors to consider when evaluating the reason why there is variable HIV resistance and progression between primate species.

Collaborators: Sarina Obeid, Hana Kapasi, Shah Khan MD, Sunil Ahuja, PhD