HLA class II polymorphism in Aka Pygmies and Bantu Congolese and a reassessment of HLA-DRB1 African diversity.

HLA-DRB1, -DQB1 and -DPB1 polymorphisms were investigated in two African populations, the Basse Lobaye Aka Pygmies of the Central African Republic, and a Bantu-speaking group from the Democratic Republic of Congo Kinshasa. Allelic and haplotypic frequency distributions reveal marked differences between the two populations in spite of their geographical proximity: the Aka exhibit high frequencies for several alleles, especially at the DPB1 locus (0.695 for DPB1*0402), probably due to rapid genetic drift, while the Bantu distributions are more even. Genetic distances computed from DRB1 allelic frequencies among 21 populations from North and sub-Saharan Africa were applied to a multidimensional scaling analysis. African populations genetic structure is significantly shaped by linguistic differentiation, as confirmed by an analysis of molecular variance. However, selective neutrality tests indicate that many African populations exhibit an excess of heterozygotes for DRB1, which is likely to explain the genetic similarity observed between some North African and Bantu populations. Overall, this study shows that natural selection must be taken into account when interpreting the patterns of HLA diversity, but that this effect is probably minor in relation to the stochastic events of human population differentiations.

Detection and quantification of HIV-1 in semen: identification of a subpopulation of men at high potential risk of viral sexual transmission.

BACKGROUND: To assess HIV burden in both acellular and cellular fractions of semen in men with different levels of blood plasma HIV RNA by a cross-sectional study. PATIENTS: Fifty-two HIV-1-seropositive men (21 receiving antiretroviral therapy) with CD4 cell counts ranging from 1 to 1170 x 10(6)/l. METHODS: Semen was separated into seminal plasma and fractions enriched in motile spermatozoa or non-spermatozoal cells. HIV RNA was quantified by the HIV-Monitor technique (Roche) in blood plasma, seminal plasma and spermatozoa fractions. HIV DNA or infectious virions in cellular fractions were detected by either PCR or qualitative viral culture. RESULTS: HIV RNA was detected in 86.5% of seminal plasma specimens and in 14.6% of spermatozoa fractions; HIV DNA was detected in 57.1% of non-spermatozoal cell fractions. HIV RNA levels in blood plasma and seminal plasma were correlated (r5 = 0.56, P < 0.0001, Spearman's rank test). A majority of men had lower levels in seminal plasma than in blood plasma: one-third had HIV-positive seminal cell fractions. However, 20 men (38.5%) with HIV RNA levels in seminal plasma (median: 4.65 log10 copies/ml) comparable to or higher than those in blood plasma had all HIV-positive non-spermatozoal cells or spermatozoa fractions with a high frequency of positive cultures. CONCLUSION: A high frequency of men had detectable HIV in semen. We identified a subpopulation demonstrating high levels of HIV RNA in seminal plasma, comparable to or higher than those in blood plasma, frequently associated with a substantial viral shedding in seminal cells, raising the possibility of viral production within the genital tract and suggesting heterogeneity in the potential of HIV sexual transmission among infected men.

Detection of HIV-1 in seminal plasma and seminal cells of HIV-1 seropositive men.

It is of critical importance to precisely understand the modalities of HIV presence in semen, especially with regard to procreation. In this study, paired blood and semen samples from 31 human immunodeficiency virus type 1 (HIV-1)-positive men were assessed for cell-free HIV-RNA load in blood plasma (BP) and seminal plasma (SP), and for detection of HIV by culture, PCR and RT-PCR in semen cellular fractions separated by centrifugation on Percoll gradient. HIV-RNA was detected in 94% of BP and 84% of SP samples. For 11 men (35%), HIV-RNA load in SP was equal or superior to that observed in blood. HIV-DNA presence was demonstrated (either by PCR or culture positivity) in 39% of the non-spermatozoal cells (NSC)-enriched fractions, and in one Percoll-selected sperm pellet. HIV-RNA was detected in 17% (4/23) of the sperm pellets. This positivity was associated with an HIV-RNA load in SP equal or superior to the HIV-RNA load in blood, a high rate of HIV-DNA detection in the NSC fraction, and a low CD4+ cell count. In such conditions, a significant viral production inside the genital tract is more likely to be present, and a close association between HIV and gametes might occur. Assisted procreation with selected spermatozoa should be preceded by accurate assessments of viral presence in blood, SP and semen cellular fractions.