16th International AIDS Conference Toronto, Canada - August 13 - 18, 2006

MATERNAL NEUTRALIZING ANTIBODIES TO A CRF01_AE PRIMARY ISOLATE ARE ASSOCIATED WITH LOW INTRA-PARTUM TRANSMISSION OF HIV-1 IN THAILAND

Int Conf AIDS. 2006 Aug 13-18;16 Abstract No. MoAa0205

Samleerat T.¹, Jourdain G.², Braibant M.³, Ngo-Giang-Huong N.², Lallement M.², Leechanachai P.⁴, Sirithadthamrong S.⁵, Surasaerneewongse V.⁶, Warachit B.⁷, Hotrawarikarn S.⁸, Barin F.^3
1Université F Rabelais, Tours, France; Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand, ²Harvard University, IRD 054; Institut de Recherche pour le Développement, UMI 174, Chiang Mai, Thailand, ³Université F Rabelais, Tours, France, ⁴Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand, ⁵Banglamung Hospital, Chonburi, Thailand, ⁶Bhumibol Adulyadej Hospital, Bangkok, Thailand, ⁷Hat Yai Hospital, Songkla, Thailand, ⁸Klaeng Hospital, Rayong, Thailand

BACKGROUND: Mother-to-child transmission of HIV-1 (MTCT) may provide a model to study the role of passively-acquired antibodies in preventing HIV infection. We previously found an association between high levels of neutralizing antibodies (NAb) toward a CRF01_AE primary isolate (MBA) and a lower rate of intra-partum transmission of HIV-1 in Thai women (Barin et al., J Infect Dis. 2006 Jun 1;193(11):1504-11). The present study was conducted in order to confirm this observation.

METHODS: We used sera collected in a clinical trial assessing various zidovudine durations for the prevention MTCT in Thailand (no breastfeeding). We matched 45 transmitting (cases) to 45 non-transmitting mothers (controls) on baseline maternal viral load and duration of maternal zidovudine prophylaxis, the two main independent factors associated with MTCT. Neutralization titers towards 6 primary isolates of clades B (FRO, BIG, CHA) and CRF01_AE (MBA, LEA, C1712) were determined by a neutralization assay using CD4+CXCR4+CCR5+ HeLa cells.

RESULTS: MTCT was only associated with undetectable or low NAb titers against MBA (p=0.009). When restricting the analysis to intra-partum or in utero transmitters and their controls, the only association that remained significant was between low level of Nab to MBA and risk of intra-partum transmission (p=0.046).

CONCLUSIONS: Our analysis confirmed our previous observation that high levels of NAb to MBA were associated with low risk of MTCT, and this was mainly due to a lower risk of intra-partum transmission. Such data support the hypothesis that passive immunization could be efficient in preventing MTCT. Further studies are needed to understand why levels of Nab to MBA are more relevant to MTCT than other Nab.

2006-08-13
MoAa0205

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