CHARACTERIZATION OF HIV TYPE-1 FROM ROMANIAN CHILDREN - LACK OF CORRELATION BETWEEN V3 LOOP AMINO-ACID-SEQUENCE AND SYNCYTIUM FORMATION IN MT-2 CELLS

The biological properties and amino acid sequences of the third variab le domain (V3 loop and flanking regions) of the env region of 34 HIV-1 isolates obtained from Romanian children were analyzed, Unambiguous n ucleic acid sequences were obtained from 31 isolates, The derived V3 a mino acid sequences were highly homologous (93-100%) and clustered wit h the HIV-1 subtype F Romanian consensus. Five of the 31 isolates pres ented a syncytium-inducing phenotype in MT-2 cells and established con tinuous viral replication in various CD4(+) cell lines (rapid/high phe notype), The V3 sequence from one of these isolates showed a slightly lesser degree of homology with the consensus sequence, The presence of positively charged amino acids at positions 306 and 320 has been stro ngly associated with the ability to induce syncytia in MT-2 cells, whe reas negatively or uncharged amino acids at these positions are presen t in non-syncytium-inducing isolates (slow/low phenotype). There was, however, no correlation between phenotype and amino acid sequence in t he five syncytium-inducing isolates; negatively or uncharged amino aci ds were conserved at positions 306 and 320 for all 31 isolates in sequ ences obtained from PBMCs, A tendency toward a more positive net charg e in the V3 loop of syncytium-inducing isolates was noted, These data confirm the recent observations that HIV-1 isolates from Romania not o nly cluster in subtype F, but also show a high degree of interpatient homogeneity in the V3 region, Our data also suggest that amino acids i n the V3 loop at positions other than 306/320 or region(s) outside the V3 loop domain may harbor determinants for syncytium induction in MT- 2 cells.