HLA class I diversity among rural rainforest inhabitants in Cameroon: identification of A*2612-B*4407 haplotype.

The population distribution of alleles of the classical HLA class I loci in Cameroon has not been well studied but is of particular interest given the AIDS and malarial epidemics afflicting this population. We investigated the genetic diversity of HLA-A, HLA-B and HLA-C alleles in remote populations of Cameroon. Subjects from seven small, isolated, indigenous populations (N = 274) in the rainforest of southern Cameroon were typed for HLA-A, HLA-B and HLA-C alleles using a polymerase chain reaction/sequence-specific oligonucleotide probe assay and sequence analysis. Multiple alleles of the HLA-A (N = 28), HLA-B (N = 41) and HLA-C (N = 21) loci were identified, of which A*2301[allele frequency (AF) = 12.8%], B*5802 (AF = 10.9%) and Cw*0401 (AF = 16.6%) were the most frequent individual alleles and A*02 (AF = 19.0%), B*58 (AF = 15.9%) and Cw*07 (AF = 22.4%) the most common serologically defined groups of alleles. Twenty-six (28.9%) alleles with a frequency of less than 1% (AF < 1%), 39 (43%) with a frequency of 2.0-15.0% (AF = 2.0-15.0%), three globally uncommon alleles [A*2612 (AF = 2.0%), B*4016 (AF = 0.7%) and B*4407 (AF = 1.4%)], and the A*2612-Cw*0701/06/18-B*4407 haplotype (haplotype frequency = 1.3%) were also identified. Heterozygosity values of 0.89, 0.92 and 0.89 were determined for HLA-A, HLA-B and HLA-C, respectively. The extensive allelic and haplotypic diversity observed in this population may have resulted from varied natural selective pressures on the population, as well as intermingling of peoples from multiple origins. Thus, from an anthropologic perspective, these data highlight the challenges in T-cell-based vaccine development, the identification of allogeneic transplant donors and the understanding of infectious disease patterns in different populations.

Exposure to nonhuman primates in rural Cameroon.

Exposure to nonhuman primates has led to the emergence of important diseases, including Ebola hemorrhagic fever, AIDS, and adult T-cell leukemia. To determine the extent of exposure to nonhuman primates, persons were examined in 17 remote villages in Cameroon that represented three habitats (savanna, gallery forest, and lowland forest). Questionnaire data were collected to assess whether persons kept wild animal pets; hunted and butchered wild game; had experienced bites, scratches, or injuries from live animals; or had been injured during hunting or butchering. While all villages had substantial exposure to nonhuman primates, higher rates of exposure were seen in lowland forest sites. The study demonstrates that exposure is not limited to small groups of hunters. A high percentage of rural villagers report exposure to nonhuman primate blood and body fluids and risk acquiring infectious diseases.

The AG recombinant IbNG and novel strains of group M HIV-1 are common in Cameroon.

The genetic diversity of group M HIV-1 is highest in west central Africa. Blood samples from four locations in Cameroon were collected to determine the molecular epidemiology of HIV-1. The C2-V5 region of envelope was sequenced from 39 of the 40 samples collected, and 7 samples were sequenced across the genome. All strains belonged to group M of HIV-1. The circulating recombinant form CRF02 AG (IbNG) was the most common strain (22/39, 56%). Two of these were confirmed by full genome analysis. Four samples (4/39, 10%) clustered with the sub-subtype F2 and one of these was confirmed by full genome sequencing. Recombinant forms, each different but containing subtype A, accounted for the next most common form (7/39, 18%). Among these recombinants, those combining subtypes A and G were the most common (4/7, 57%). Also found were 3 subtype A, 2 subtype G, and 1 subtype B strain. Many recombination break points were shared between IbNG and the other AG recombinants, though none of these other AG recombinants included IbNG as a parent. This suggests that there was an ancestral AG recombinant that gave rise to CRF02 AG (IbNG), the successful circulating recombinant form, and to others that were less successful and are now rare.

Presence of diverse human immunodeficiency virus type 1 viral variants in Cameroon.

Phylogenetic analysis of the gp41 region of 123 HIV-1-seropositive specimens from Cameroon showed that 89 were subtype A (71% of these sequences were IbNg-like), 12 (10%) were subtype D, 11 (9%) were subtype G, 5 (4%; closely related to subtype F2) were subtype F, 1 was subtype H, 2 (1.6%) remained unclassifiable, while 3 were group O. Further analysis of the two unclassifiable specimens in gag(p24), pol(prot), and env (C2V3 or gp41) showed that one (98CM19) was a complex mosaic between subtype A in p24 and subtype J prot, and unclassifiable in env (C2V3 or gp41). The second, 98CM63, clustered distinctly from all known subtypes in p24, prot, C2V3, or gp41. 98CM63 clustered with a specimen from Cyprus and these two geographically and epidemiologically unlinked specimens, with their distinct clustering pattern, may represent a new subcluster of subtype A. In conclusion, these findings confirm the high HIV-1 genetic variability and further suggest the continuous appearance of new viral strains in this population.

Update on the HIV epidemic in Cameroon

The study aimed at estimating the extent of AIDS epidemic in Cameroon upon which a guideline for activities of the National AIDS programme could be based. It comprises a total of 2377 individuals who attended the antenatal clinic (n=1091); subjects attending sexually transmitted diseases (STD) clinics (n=382) and blood donors (n=212). In Kumba a random recruited individuals attending the hospital casual consultation (n=160) was done; and compared their HIV seroprevalence results with those of frozen samples (n=391) collected from a malaria community survey in 1989; and 141 randomly selected pygmies aged between 18-45 years in the eastern province of Cameroon was screened. HIV-1/2 infection was detected with one or the other of a combined screening assay. The results obtained were as follows: in Kumba; one of the 391 was positive (0.3 percent; CL; 0-0.8) compared with one of the 160 casual consultants sera in 1992 (0.6 percent; CL; 0-1.4). In the rural areas; 13 individuals (3.5 percent; 95 percent CL; 1.7-5.3) were HIV-1 positive; one was HIV-2 positives and one of the 141 pygmies (0.7 percent; 95 percent CL; 0-2) was HIV-1 positive. The seroprevalence results in Bamenda and Bafoussam ranged from 4.2 percent and 1.2 percent. Thus rate varied from 4.3 percent in Kumba to 8.8 percent in Ngaoundere and those reported in Yaounde between 189-90 were 3.3. High HIV seroprevalence was found in blood donors in Bamenda and Limbe (3.1 to 5.7 percent). The authors concluded that since HIV will inevitably reach the remote areas in Africa; HIV control activities must be inititated in all populations in Cameroon irrespective of their location