Differential transmission of HIV-1 and HIV-2

Abstract

We report two cases of seroconversion occurring within 6 months in two women sexual partners after exposure to an HIV-1-infected and HIV-2-infected man. Serological data from 3 years follow-up indicated that one of the women became infected with both HIV-1 and HIV-2 (partner one), whereas the other became infected with HIV-2 only (partner two). Partner one had several exposures whereas partner two had a single exposure only. Samples from all three patients were analysed by direct sequencing of the V3 region of HIV1 and HIV-2. Samples from the two female partners were also analysed by virus isolation and PCR. Isolation of HIV from peripheral mononuclear blood cells (PBMC) was attempted by co-cultivation of purified CD4 lymphocytes from the two female partners and HIV-1 negative donors. HIV-1 was cultured from partner one, while no infectious HIV could be cultured from partner two. DNA extracted from PBMC from the two partners were analysed in HIV-1 and HIV-2 PCR with Amplicor HIV-1 test (Roche), in-house gag p17 HIV-1 PCR and in-house HIV-2 gag p17 PCR. Samples from partner two were positive to HIV-2 gag p17 PCR, while partner one was positive in both Amplicor HIV-1 test, HIV-1 gag p17, and HIV-2 gag p17 PCR. Direct sequencing of the V3 region was done on proviral DNA extracted from PBMC (samples from the two partners) and from RNA extracted from serum (sample from index case). Phylogenetic analyses of the V3 sequences confirmed that the index case and partner one were both double-infected with HIV-1 (subtype A) and with HIV-2 (subtype B), whereas female partner two was infected with HIV-2 (subtype B) only (figure). The phylogenetic trees show that both the HIV-1 and the HIV-2 strains found in the index case and in the two partners were closely related. The monophyletic clustering of the sequences from the index case and the two partners were retained in additional analyses which included database sequences as well as many unpublsihed HIV-1 and HIV-2 sequences from our laboratory. These results strongly indicate that the viruses found in the two female partners were transmitted from the index cases. Genotyping of the secondary receptors of HIV-1 and HIV-2 CCR-5 showed that both female partners were homozygous for the wild-type CCR-5 allele. Our results confirm that the double-infected index case had transmitted both HIV-1 and HIV-2 to partner one, and that partner two was infected with HIV-2 only, after probable exposure to both HIV-1 and HIV-2.