Immunoreactivity and conformation of the immunodominant domain of HTLV-I envelope surface glycoprotein

The envelope of the human retrovirus HTLV-I (humanT-cell leukemia virus type I), like those of otherretroviruses, plays an important role in viralinfection. One of the major immunodominant domains ofHTLV-I surface glycoprotein (gp46), inducing antibodyreactions in over 90% of infected individuals, isbounded by amino acids 175 and 199. As compared toHTLV-I prototype strain MT-2, few amino acidsubstitutions have been described in this region; themost frequently observed is the replacement of aproline by a serine at position 192. In order toinvestigate the antigenic impact of this variation, weanalysed the reactivity of synthetic peptides,harbouring either a proline or a serine residue,towards antibody containing HTLV-I positive sera inenzyme linked immunosorbent assays. The possibleinfluence of this amino acid substitution on theconformational behaviour has been examined by studyingthe solution structure of two model peptides(corresponding to the 175–199 region) usingtwo-dimensional ¹H NMR spectroscopy. The resultsof this work should allow us to find out whether thisamino acid substitution has to be taken into accountfor the design of a future peptide-based vaccineagainst HTLV-I infection.