Background: Recent studies on HIV-1 genetic diversity in Cameroon focused on HIV-1 patients living in urban and semi-urban areas revealed the predominance of the CRF02_AG strains. Information on genetic and biologic properties of HIV-1 strains infecting persons in rural villages is lacking. We have genetically analyzed the HIV-1 subtypes and determined the co-receptors used by viruses infecting persons living in rural villages in the equatorial rain forests of Cameroon.

Methods: Both env (V1 to V5) and gag (a portion of p24 to p7) HIV-1 group-M subtypes infecting 15 persons living in rural villages in the equatorial rain forests of Cameroon were analyzed by the heteroduplex mobility assay (HMA), sequencing and phylogenetic analysis. Co-receptor usage of the viruses was determined using GHOST cells expressing different co-receptors including CCR1, CCR2, CCR3, CCR5, CXCR4, BOB, and BONZO.

Results:  Analysis of both env and gag genes revealed a high HIV-1 diversity in the rural villages of Cameroon. Using either env or gag genes, 5 subtypes were identified, including subtype A, D, G, H, and CRF02_AG. Parallel env/gag subtyping revealed 5 infections that were subtype A/CRF02_AG, 1 CRF02_AG/CRF02_AG, 1 A/A, 3 D/D, 1 G/G, and 1 H/G. Subtype determination was possible only in gag for 3 samples and were subtyped as A (n=2) and G (n=1). These results suggest the presence of intersubtype recombinant as well as circulating recombinant forms in rural villages in Cameroon. The viruses from all 15 patients were able to infect GHOST cells expressing CCR5. In addition, 2 viruses that were subtype D replicated in GHOST cells expressing CXCR4 and CCR3. None of the 15 viruses tested replicated in the GHOST cells expressing CCR1, CCR2, BOB and BONZO.

Conclusions:  These results reveal a vast HIV-1 genetic diversity but a more restricted co-receptor usage of these viruses infecting persons in the equatorial rain forests of Cameroon. These results illuminate the evolutionary properties of HIV-1 strains in regions of high HIV diversity.