109 THE ROLE OF CD4 POLYMORPHISM ON HIV-1 INFECTION J Oyugi1, J Alimonti1, F Vouriot1, S Wayne1, F Plummer1, J Barry2, KR Fowke1 Objectives: We have previously shown that a novel single nucleotide polymorphism (SNP) 868T found on CD4 gene is highly prevalent (30%) among Africans, is associated with risk of acquisition of HIV-1 and accelerates disease progression. However, the molecular mechanisms for this association are poorly understood. The aims of this study were to determine; 1) if CD4 SNP has direct effect on the ability of HIV to infect cells expressing the altered CD4 isoform; and 2) whether the effect is at the level of CD4 signal transduction.
1University of Manitoba; 2National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba
Methods: A2.01 T cells that lack CD4 expression were transfected with plasmids carrying either wild type or polymorphic CD4 genes. Separate cell lines expressing equivalent levels of either CD4 isoforms were selected and infected with CD4-dependent and CD4-independent laboratory adapted HIV-1 viruses and primary Kenyan viruses. Supernatant or cells were harvested at different time points and p24 was measured by ELISA and flow cytometry assays. To determine if signal transduction was altered in the polymorphic CD4 isoform, cells expressing either CD4 isoform were cross-linked with anti-CD4 and phosphorylated p56lck measured using western blot, Luminex and flow cytometry.
Results: Significantly higher amounts of p24 (IIIB virus, p<0.0001, ml 235 p<0.001, ml 1956, p<0.002) and phosphorylated p56lck (p<0.000001) were detected from cells expressing polymorphic CD4 compared to wild type CD4. However, infection with the CD4-independent virus on the two CD4 isoforms did not yield any significant differences in the amount of p24 (p=0.7103) detected.
Conclusions: These results suggest that the altered CD4 is readily activated and facilitates more HIV replication on infection with T-Tropic and Kenyan viruses. While further work is necessary to define the mechanisms in greater detail, the long-term goal is that a better understanding of how this SNP influences HIV infection may have implications in the design of better anti-retroviral therapy.