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Since its co-receptors were discovered, HIV tropism is defined by the type of co-receptor used to infect its host cells : R5 for viruses using only CCR5, X4 for viruses using only CXCR4, and R5/X4 or dual for viruses using either CCR5 or CXCR4. Tropism prediction actually made is via recombinant phenotypic assays, which are labour-intensive, long-lasting and expensive, available in only a few highly qualified laboratories. Prescription of CCR5-antagonists requires screening for the presence of X4 variants before starting therapy. With development of this new class of antiretrovirals there is a need for genotypic tests, based on V3 loop gp 120 env gene sequencing and its interpretation with an algorithm. As for resistance tests 10 years ago, these genotypic tests will be easier to introduce into routine clinical practice. These genotypic tropism assays will help to select patients before CCR5-antagonist prescription and to follow patients treated by this class of antiretrovirals, looking for a potential switch of tropism during therapy.

Resume En Europe, la transmission verticale du virus de l'hepatite C est asymptomatique, et se produirait dans 0 a 25 % des cas avec viremie maternelle. La seule mesure preventive est de deconseiller l'allaitement. La faible charge virale, l'absence de replication ancienne et la non-integration genomique sont des conditions favorables a un essai de sero-prophylaxie chez le nouveau-ne par des anticorps neutralisants d'origine humaine. Les obstacles a un essai randomise et controle sont nombreux : - Epidemiologiques : rarete du recrutement; risque faible; transmission in utero possible par les meres les plus viremiques; risque de contamination horizontale du nourrisson au foyer. - Methodologiques : randomisation complexe des groupes (genotypes, PCR quantitative, hepatite maternelle, modes d'accouchement et d'allaitement). - Ethiques : benefice individuel direct non etabli; l'allaitement par des meres viremiques serait-il autorise en l'absence de seroprophylaxie ? Risque de fvoriser l'emergence de variants viraux chez le nourrisson; origine et selection des plasmas-source.

HBs Ag carrier rate among pregnant women is 1.5% in our hospital near Paris, six times higher than French national prevalence among women. 78% of them are of extra-metropolitan origin (especially from the African continent), 80% have a low socioeconomic status. Their newborns are at risk of "mother-to-infant" transmission of the virus HB. The risks, mechanisms and consequences of such a transmission are studied. For these reasons, it seems reasonable to perform routine prenatal testing for HBs Ag carriage. We have successively carried out two prophylactic methods. From June 1980 to October 1982, prevention with specific immunoglobulins (HBIG) was used: ten infants received at birth 0.5 ml, and 0.1 ml/kg at 1, 2, 4, 6 months of age. At 6 months, they all were safe of liver damage, HBs Ag and HBe Ag negative. Eleven infants received only the first HBIG injection. From October 1982 to September 1983, fifteen carrier women were identified at the time of delivery, and all accepted the sero-vaccination procedure for the newborn: HBIG (1 ml) and vaccine before 48 hours of life and at one month, vaccine alone at two months. The babies were controlled (9 at 4 months, 3 at 12 months) and all were safe of liver damage, HBs Ag and HBe Ag negative, with HBs antibody mean value of 240 m I.U./ml. We are grateful to the collaboration of the Departments for Mother and Infant Protection in our region--according to the usual chronology of the visits--for these satisfactory performance and results of the sero-vaccination.