SEROLOGICAL AND VIROLOGICAL CHARACTERIZATION OF HIV-1 GROUP-O INFECTION IN CAMEROON

Objectives: To study the presence of HIV-1 group O infection among HIV -infected people in Cameroon and to further characterize the HIV-1 gro up O infections.Design and methods: During a 2-year survey (1994-1995) , all samples tested positive in screening methods in the National Ref erence and Public Health Laboratory, Centre Pasteur, Yaounde, Cameroon were identified as HIV-1 group M, HIV-1 group O or HIV-2 by using a s erological algorithm. HIV-1 group M and HIV-1 group O were distinguish ed on the basis of competitive enzyme-linked immunosorbent assay (ELIS A) reactivity against gp41 group M recombinant protein. HIV-1 group O infections were confirmed by using group O-specific V3 synthetic pepti des. HIV-1 group O strains were isolated by lymphocyte cocultures, pro viral DNA was amplified with specific primers, and sequencing was perf ormed on the C2V3 and gag regions. Results: Of the 8331 screened sampl es, 3193 were HIV-reactive, 2376 (74%) of which were considered to bel ong to group M. The 817 (26%) that had reacted poorly or not at all ag ainst group M gp41 were further characterized: 10 were confirmed as HI V-2 and 82 as HIV-1 group O, the others being indeterminate (n=285) or negative (n=440). The frequency of group O relative to group M ranged from 1% in Far North province to 6.3% in the capital. There was no di fference in sex, age or frequency of clinical manifestations between g roup M and group O infections. Group O infection was confirmed in a su bset of cases by polymerase chain reaction (n=14), with perfect concor dance. Sequencing and phylogenetic analyses confirmed the high variabi lity inside group O. Conclusions: Group O and group M epidemiological patterns are known to be similar so the reason for the lower prevalenc e of group O remains to be found. The wide distribution of group O inf ection in all Cameroonian provinces underlines the importance of furth er characterizing the epidemic spread and diffusion of this group.