Vertical transmission of human immunodeficiency virus type 1: autologous neutralizing antibody, virus load, and virus phenotype.

Abstract

To evaluate immunologic and virologic correlates of vertical transmission of human immunodeficiency virus type 1 (HIV-1). Case-control study. Women who were prospectively enrolled in a natural history study of HIV-1 infection in women and infants. Sixteen HIV-1-infected women whose infants became infected were matched by CD4+ cell percentage and use of zidovudine during pregnancy with women whose infants did not become infected. Maternal autologous neutralizing antibody, virus load determined by RNA-polymerase chain reaction (RNA-PCR), and virus phenotype. Most women in both groups had low titers of autologous neutralizing antibody, and no difference in neutralizing titers was observed (range, < 4 to 181 in both groups). The HIV-1 copy number in maternal plasma was not significantly different in the two groups but was inversely correlated with maternal CD4+ cell percentage (p < 0.005). Five women in the transmitting group and four in the non-transmitting group had syncytium-inducing (SI) phenotype virus. Two infected infants had SI phenotype virus. The SI phenotype virus was associated with a greater HIV-1 copy number in maternal plasma (p < 0.05) and an increase in the mortality rate for the infants (p < 0.01). In women matched for CD4+ cell percentage, low titers of autologous neutralizing antibody, high virus load, and SI phenotype virus were not associated with an increased risk of transmission of HIV-1 to their infants.