7th International AIDS Conference Florence, Italy — June 16-21, 1991

Int Conf AIDS 1991 Jun 16-21; 7:28 (abstract no. M.A.28)
Calabro ML, Hoad JH, Matutes E, Catovsky D, Weiss RA, Schulz TF; Institute of Cancer Research, Chester Beatty Labs., London, England

OBJECTIVE: Comparative analysis of HTLV-I envelope sequences derived from ATL cases of different countries was performed in order to evaluate their genetic distance from prototype sequences and to identify amino acid changes localized in immunogenic regions of the envelope.

METHODS: PCR-amplified envelope regions of 5 Brazilian, 2 Caribbean and 1 Romanian cases of ATL were cloned in Bluescript and sequenced by dideoxy chain termination method. Nucleotide changes were confirmed by direct sequencing. RESULTS AND DISCUSSION: The data confirmed that the HTLV-I env sequence is highly conserved among strains from different geographical regions; however, none of the env sequences was completely identical. The sequence from the Romanian patient, in spite of its different geographical origin, was not significantly more divergent than any of the others. Sequence analysis revealed two changes in a region (aa176-209) which has previously been shown to contain a linear B-cell epitope recognized by most patient sera. In order to assess whether these changes would affect antibody binding to this epitope, we expressed aa 157-225 from two sequence variants in E.Coli. We could show that monoclonal antibodies to this epitope exhibited differential reactivity to these sequence variants. This is the first demonstration of envelope epitope variability of this highly conserved human retrovirus.

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