Diversity of HIV-1 genetic subtypes in France, in the context of mother-to-child transmission

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HIV-1 displays a high genetic variability that is rapidly evolving. Phylogenetic analyses have resulted in the classification of HIV-1 isolates in two groups, group M (major) and group O (outlier) [1] Group M viruses (subdivided into 10 subtypes: A–J) are widespread; in contrast group O viruses are mainly found in patients from central Africa or in patients originating from that region. In western Europe, the AIDS epidemic is mainly caused by the B subtype, although a co-circulation of non-B subtypes has recently been reported in Belgium, Sweden, the United Kingdom and the Netherlands [2–5] In France, non-B subtypes have been isolated in individuals originating from Africa and in caucasian patients [6] Moreover, the prevalence of non-B strains in French blood donors increased between 1985 (4%) and 1995 (20%) [7] The aim of this study was to describe HIV-1 subtype repartition in the context of mother-to-child transmission, within a group of individuals living in France and originating from Africa. In the French National Cohort Study, a progressive evolution of the percentage of African mothers infected with HIV-1 has been observed; it was approximately 10% in 1990 and 40% in 1997 [8] Three mothers infected with HIV-1 group O viruses have also been identified and one case of transmission to the child has been described [9] In the present study, all available samples collected in the period 1986–1996 from patients originating from Africa were selected, and thus 163 HIV-1 strains were analysed from 70 infected infants and from a further 93 mothers who gave birth to non-infected children. Genotyping was performed by the heteroduplex mobility assay as described by Delwart et al. [10] DNA was extracted from peripheral blood mononuclear cells, and the polymerase chain reaction was performed using ED3–ED12 as outer primers and ES7–ES8 as inner primers. The repartition of HIV-1 variants, identified in the 18 corresponding countries, is presented on the map in Fig. 1. For seven African patients, the country of origin was unknown; the repartition of subtypes was six A and one D. In west Africa, subtype A viruses were predominant (41/54, 76%). A more complex subtype distribution was observed in central Africa. Among the 101 infected patients, all the main HIV-1 subtypes were identified (56 A, 13 B, 4 C, 10 D, 2 E, 6 F, 7 G, 3 H). This study, performed on a large number of samples, completes the results described by several studies conducted locally in each African country [11–13] Subtype A was found in all parts of west and central Africa and the largest diversity of HIV-1 subtypes was found in central Africa, indicating a large co-circulation of variants in these countries. However, we reported 13% of HIV-1 B subtype, which seems higher than previously reported either in west or central Africa. It was difficult to determine whether these mothers had been infected before or after moving to France. However, they are likely to have been infected with African strains because they have been living in France for less than 2–3 years and they mostly stay within their own community.Fig. 1.: Map of Africa: the repartition of the viral subtypes is indicated for each of the 18 countries.Therefore, as early as 1986, a very high diversity of HIV-1 subtypes was circulating among the community of African mothers living in France. This emphazises the increasing importance of viral strains trafficking in France. It has been reported that HIV-1 subtype diversity may have a major impact on viral load quantification [14,15] Therefore, it is important to be aware of this viral diversity existing in France, to avoid viral load misquantification in pregnant women and the misdiagnosis of HIV-1 infection in babies. In our laboratory, diagnosis is performed using HIV-1 polymerase chain reaction DNA on peripheral blood mononuclear cells with two different pairs of primers, selected within conserved genes (LTR and gag) in order to be able to detect the majority of viral strains. At present, in the French National Cohort Study, no difference in HIV-1 transmission rates has been found between Caucasian and African mothers [8] In conclusion, the periodic evaluation of circulating viral strains is necessary for epidemiological surveys; moreover, such studies should allow the characterization of sufficient samples to address the question of the eventual differences in the pathogenicity of the different viral subtypes, parti-cularly in the context of mother-to-child transmission. Marie-Laure Chaixa Olivier Manigartab Franck Letourneurc Marianne Burgarda Marie-Jeanne Mayauxd Christine Rouziouxa the French Pediatric Cohort Study Group Acknowledgements The authors are grateful to James Mullins for providing plasmids for the heteroduplex mobility assay.