490 The Intrinsic Difference in Susceptibility to AIDS-like Disease Induced by Simian Immunodeficiency Virus: Infection of Rhesus Macaques Is Associated with the Ability of Primary CD4+ Lymphocytes to Differentially Control Viral Reverse Transcription A. Hartman*, P. Rajakumar, M. Murphey-Corb Univ of Pittsburgh Sch of Med, PA
Background: Rhesus macaques infected with Simian Immunodeficiency Virus (SIV) die of AIDS within an average of 2 yrs; however, survival can vary anywhere from 2 months (mos) to greater than 5 yrs. We have previously shown that PBMC from uninfected animals vary in the ability to produce virus after in vitro infection in a viral growth kinetics assay, prompting their classification as high producers, intermediate producers, or low producers of virus. This in vitro classification of animals persists even when purified CD4+ T-cell populations are used, indicating that the CD4+ T-cell itself is responsible for the differences in virus production observed. Importantly, using a cohort of 59 animals, we have shown that animals classified in vitro as high producers progressed to disease significantly more rapidly than animals classified as either low (p = 0.002) or intermediate (p = 0.013) producers. We hypothesize that differences in in vitro virus production, and hence in vivo disease progression, are due to an impairment in the virus replication cycle in low producer CD4+ cells.
Methods: Viral entry was measured by quantitating the amount of internalized p27 after a 2 hr adsorption period. Viral DNA and RNA transcripts were measured using real-time PCR. Virus infected cells were measured by anti-p27 intracellular flow cytometry.
Results: The minimal infectious dose required to infect low producer CD4+ cells was 10-fold higher than for high producers cells (p = 0.0058). No significant difference in viral entry was observed between the 2 groups. Quantitative analysis of strong stop and full-length cDNA by real time PCR demonstrated that reverse transcription products accumulated more slowly (1.5- to 2-fold lower) within 4 and 8 hrs post-infection, respectively, in low producer cells. Further, significantly less (3-fold) viral RNA was also detected in low producer cells.
Conclusions: Our results show that virus infection of low producer animal CD4+ cells is inhibited 2-fold at a point after viral entry, but before or at initiation of reverse transcription. This inhibition is enough to result in fewer viral RNA transcripts and 5-fold less virus production overall, a finding we have shown to correlate significantly with slower disease progression in vivo.