Recognition by human sera of a variable region of the surface glycoprotein of HTLV-I

The region comprised between the amino acids 175 and 199 of the HTLV-I envelope surface glycoprotein is one of the immunodominant domains of this molecule. In this region, which is well recognized by sera from HTLV-I infected patients, a substitution of the proline at position 192 by a serine has been described in some isolates. Because this mutation could modify the secondary structure of the glycoprotein molecule, we studied the inference of the presence of proline or serine on the recognition of the region 175-199 by human sera. For this, three peptides have been synthetized (a 25-mer 175-199 corresponding to the sequence of the ATK prototype, and two internal 10-mer 190-Pro-199 and 190-Ser-199 having a proline or a serine at position 192) and tested by immunosorbent assay. While most sera reacted with 190-Pro-199 and with 190-Ser-199 synthetic peptides, a differential recognition was observed according to the pathology associated to HTLV-I infection. Moreover sera corresponding to patients infected with a virus harboring a serine at position 192 were found to recognize only the 10-mer with a serine. These data indicates that HTLV-I is subject to antigenic variability.