Background:  HIV-1 group O is rare and mainly found in the West of Central Africa or countries or people having closed contacts with this area. As for HIV-1 group M, mother-to-child transmission occurs and has been previously reported. Prophylaxis using nevirapine is not adapted to group O-infected mothers due to the natural resistance of these variants to this drug. New-borns from group O-infected mothers still remain difficult to monitor. Plasma quantification is limited to specialized laboratories due to the lack of commercial assay, only one (LCx HIV RNA QT, Abbott) being available for the detection of group O RNA.

Methods: Plasma RNA quantification by real time RT-PCR procedure was based on LightCycler technology (Roche). Primers were selected in the highly conserved LTR region and amplified both HIV-1 group M and group O strains. A HIV-1 group O-specific probe is used allowing identification and quantification. These primers and probe were adapted to a DNA assay in order to amplify provirus in PBMC from new-borns of group O-infected mothers. These techniques were used for diagnosis and follow-up of three new-borns of group O-infected mothers living in France. The children were strictly bottle-feed.

Results:  The mother of the first child was diagnosed as group O-infected before pregnancy and was under HAART. Maternal viral load was repeatedly undetectable (<200 copies/mL, 2.3 Log) but the presence of proviral DNA in her PBMC was confirmed by the real-time PCR. A second mother was recognized group O-infected at the early stage of pregnancy and treated by zidovudine during 6 weeks. Maternal viral load was detectable (>3 Log) after treatment interruption post-delivery. In these two cases, the children were not infected, serial RNA and DNA testing being negative confirmed by loss of the anti-HIV maternal antibodies. In the third case, without any follow-up during pregnancy, maternal group O infection was diagnosed at the delivery with high plasma viral load (4.6 Log) and low CD4 (78/mm³). The contamination of the child was confirmed by both proviral DNA in PBMC and a high level of plasma RNA viral load (>5 Log).

Conclusions:  Specific PCR based on real-time technology allow the diagnosis and follow-up of children of HIV-1 group O-infected mothers. Our results underline the importance of identification HIV variant to adapt pregnancy monitoring and offspring follow-up.

Keywords: HIV-1 group O; mother-to-child transmission; monitoring