Differences in perinatal transmission among human immunodeficiency virus type 1 genotypes

Objective: To determine whether genotypes from human immunodeficiency virus type 1 (HIV-1) subtypes A, C, or D or intersubtype recombinants have the s ame probability of be ing transmitted from mother to child. Methods: We determined the HIV-1 genetic subtype and maternal risk factors of 51 matched transmitting and nontransmitting mothers from Tanzania. The H IV-1 gag (p24-p7) and env (C2-C5) nucleotide sequences were used for genoty pe classification, and matched logistic regression analysis was used to ass ess differences among genotypes. Results: Mothers infected with HIV-1 subtype A (odds ratio 3.8; 95% CI, 0.8 -24.7%), HIV-1 subtype C (odds ratio, 5.1; 95% CI, 1.3-30.8%). or HIV-1 int ersubtype recombinant viruses (odds ratio, 5.3; 95% CI, 1.2-33.4%) were mor e likely to transmit HIV-1 to their infants than mothers infected with HIV- 1 subtype D. Lower CD4 cell counts at enrollment were associated with trans mission, but CD4 cell counts within each genotype pe did not explain differ ences in transmission among HIV-1 genotypes. Conclusion: We have shown that HIV-1 genotypes might be associated with dif ferential risk for vertical transmission. These findings provide the first evidence that HIV-1 genetic subtypes may play a role in rates of vertical t ransmission in an African setting.