EVIDENCE IN GABON FOR AN INTRAFAMILIAL CLUSTERING WITH MOTHER-TO-CHILD AND SEXUAL TRANSMISSION OF A NEW MOLECULAR VARIANT OF HUMAN T-LYMPHOTROPIC VIRUS TYPE-II SUBTYPE-B

Following the observation of an HTLV-II seropositive 60-year-old woman living in Gabon (Central Africa), a serologic and molecular study of her family members was conducted in an attempt to determine the durati on of the HTLV-II infection and the modes of transmission of the virus . Among 41 family members, five were HTLV-I seropositive and 7 exhibit ed specific HTLV-II antibodies in their sera as demonstrated by high i mmunofluorescence titers on C19 cells and/or specific Western-blot pat tern. The second husband of the index case and two of his sisters were infected by the virus, suggesting the presence of HTLV-II in this fam ily over two generations. Sequence analysis of an amplified fragment o f 172 nucleotides within the gp21 of the env region (6469-6640) of fou r HTLV-II infected individuals revealed a new HTLV-II molecular varian t of the subtype b diverging from the prototypes NRA and G12 by seven (4.1%) and five (2.9%) bases substitutions, respectively. Molecular an alysis of the total env gene (1462 bp) and fragments of the pol and pX regions confirmed that this new African variant was the most divergen t HTLV-II subtype b yet described, exhibiting 2.3% of nucleotide subst itutions in the env gene (33 bases) as compared to the two HTLV-II b p rototypes. These data demonstrate, for the first time in Africa, intra familial both mother-to-child transmission and sexual transmission bet ween spouses of an HTLV-II b molecular variant, and also suggest that this virus has been present in Gabon for a long period of time. (C) 19 96 Wiley-Liss, Inc.