: Male sex workers who sell sex to men in Mombasa are in acute need of targeted prevention information on anal HIV and STI transmission, consistent condom use, and correct lubrication use with latex condoms. HIV programs in Africa need to consider and develop specific prevention strategies to reach this vulnerable population.

In eight of the 12 countries tested, antibodies to group O viruses were identified. Numbers of HIV-1 group O viruses are low. Their presence is not restricted to Cameroon and neighbouring countries but can also be found in west and south-east Africa.

The purpose of this study was to generate data on the relative prevalences of the HIV-1 subtypes circulating in Nigeria. A total of 252 HIV-1-positive samples collected during an epidemiologic survey conducted in April 1996 were genetically characterized by HMA (heteroduplex mobility assay) and/or sequencing. Samples were collected in Lagos, Calabar, Kano, and Maiduguri. Overall, the predominant env subtypes were A (61.3%) and G (37.5%). Subtype A is more prevalent in the south (p < 0.001), about 70% in Lagos and Calabar, whereas a quarter of the samples was classified as subtype G in these states. In contrast, subtype G is predominant in the north ( < 0.001), representing 58% of the samples in Kano. In the northeastern region, Maiduguri, almost similar proportions of subtype A and G were seen, 49 and 47.4%, respectively. A total of 37 samples was also sequenced in the p24 region from the gag gene; 13 (35%) had discordant subtype designations between env and gag. The majority of the gag (12 of 17) and env (14 of 22) subtype A sequences clustered with the A/G-IBNG strain. Within subtype G, three different subclusters were seen among the envelope sequences. These different subclusters are observed among samples obtained from asymptomatic individuals and AIDS patients from the four Nigerian states studied. In conclusion, we observed a limited number of HIV-1 subtypes circulating in Nigeria, with subtypes A and G being the major env subtypes responsible for the HIV-1 epidemic. Nevertheless, the high rate of recombinant viruses (A/G) and the different A/G recombinant structures indicate a complex pattern of HIV-1 viruses circulating in this country.

To determine current data on HIV infection and to further confirm the presence of HIV-1 group O infection in Nigeria, 2300 samples from five states were tested for the presence of HIV antibody. A convenience sampling was obtained from pregnant women, tuberculosis (TB) patients, commercial sex workers (CSWs), blood donors, patients with sexually transmitted diseases (STDs), patients with skin diseases, male clients of CSWs, outpatients suspected to have AIDS, truck drivers, and community dwellers. With the exception of pregnant women, the HIV prevalences in all these groups were high: 60.6% in CSWs, 16.2% in TB patients, 7.7% in blood donors in some states, and 16% in the rural area of Kano State. Male clients of CSWs, truck drivers, and STD patients had prevalences of 7.8%, 8.6%, and 21.2%, respectively. Regional differences in relation to HIV prevalences were observed; HIV-2 and most of the HIV-1/2 infections were found in the southern states of Nigeria. Higher HIV prevalences were observed in the north-northeast in pregnant women, TB patients, and CSWs, but for blood donors, higher rates were seen in the southeast-southwest. One asymptomatic 50-year-old woman, a community dweller in Kano, was identified to be HIV-1 group O-positive. Compared with data from national surveillance studies in 1991/1992 and 1993/1994, a substantial increase in HIV infection was observed. Our results show a growing incidence of HIV infection in Nigeria and suggest the presence of a rural HIV epidemic. The identification of HIV-1 group O in Kano shows that this virus strain is geographically widespread in Nigeria.

Most efforts to characterize sequence variation of HIV isolates has been directed toward the structural envelope gene. Few studies have evaluated the sequence variability of auxiliary genes such as nef. In this study 41 new HIV-1 strains, representing the majority of the described envelope subtypes of HIV-1 (A to H), were genetically characterized in the nef region. Phylogenetic analysis showed that 34 strains could be classified in the same subtype in nef and env, and 7 (19%) of the 41 new viruses were recombinants. For two of the seven strains, recombination occurred upstream of the nef gene, whereas for five of the seven strains recombination occurred within the nef gene with a crossover close to the 5' end of the LTR (long terminal repeat). The low intersubtype distance between subtype B and D in the nef gene confirms previous observations in the pol, env, and gag genes, which suggest a common ancestor for these subtypes. The majority of all the previously described functional domains in the nef gene were relatively conserved among the different subtypes, with only minor differences being observed. The myristoylation signal among the different subtypes, with only minor differences being observed. The myristoylation signal was less conserved for subtype C, with one or more amino acid changes being observed at positions 3, 4, and 5. The highly conserved acidic region (positions 62 to 65), critical for the enhancement of viral synthesis with an increased virus growth rate, was less conserved among the subtype G strains from our study. At least three epitopic regions of the nef gene have been defined and each can be recognized by CTLs under a variety of HLA restrictions; all were also relatively well conserved between the different genetic subtypes. Despite the relatively important genetic variation in nef sequences obtained among the different genetic subtypes, functional domains and CTL epitopes were relatively well conserved. In vitro and/or in vivo studies are necessary to study the relevance of the observed differences.