Vertical HIV-1 transmission: Importance of neutralizing antibody titer andspecificity

Neutralization analyses were carried out with plasma from 132 volunteer hum an immunodeficiency virus (HIV)-1 infected women (76% pregnant, 24% with in fants suspected for HIV-1 infection) collected between 1994 and 1998, again st autologous and heterologous primary- and the reference HIV-1 MN isolates . A significantly lower percentage of HIV-1 transmissions was observed afte r 1996, parallel to a more intense antiretroviral treatment of infected pre gnant women. HIV-1 isolation was significantly more frequent from periphera l blood mononuclear cells of mothers of infected children than mothers of u ninfected children (P = 0.0065). Neutralization of autologous HIV-1 isolate s was comparable for HIV-1 transmitters and nontransmitters' plasma, wherea s neutralization of the reference isolate HIV-1 MN was more frequent at hig h titers for pregnant women who did not transmit HIV to their offspring com pared to pregnant women who did. Although neutralization of heterologous pr imary HIV-1 isolates from HIV transmitters and non transmitters by transmit ter plasma occurred with similar frequency, neutralization of isolates from transmitters was much more frequent when heterologous plasma from nontrans mitters were used. Macrophage-tropic heterologous HIV-1 isolates were neutr alized more frequently at higher titers by plasma from nontransmitters than from transmitters. The results obtained indicate that antiretroviral treat ment, lack of success of HIV-1 isolation and high titers of antibodies able to neutralize macrophage-tropic viruses appear to be of importance for pro tection against HIV-1 vertical transmission for the group of patients studi ed.