IDENTIFICATION OF IIA AND IIB MOLECULAR SUBTYPES OF HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-II AMONG ITALIAN INJECTING DRUG-USERS

The molecular characterization of two human T-cell lymphotropic virus type II (HTLV-II) isolates, Gu and Va, obtained from Italian injecting drug users (IDUs) has indicated that these isolates belong to the HTL V-IIb subtype. To establish whether Italian IDUs are also infected by the HTLV-IIa variant, sequencing of the gp21 env gene of proviral DNA from further patients was carried out. Two new isolates, Bo and Md, we re found, which presented a divergence of 0.4-0.7% from the IIa protot ype HTLV-II-Mo, thus indicating that they belong to the HTLV-IIa subty pe. The results strongly support the existence of two distinct molecul ar subtypes of HTLV-II infecting Italian IDUs and demonstrate that, al though the IIb subtype appears to be prevalent, there is the same vari ability for this virus in Europe as found in the United States. The It alian IIb isolates were also seen to encode an additional 25 amino aci ds at the C-terminal end of tax protein, as already shown for other II b isolates. The identification of two HTLV-II molecular subtypes among Italian drug addicts will be useful in tracing the worldwide distribu tion of this virus and in further understanding its molecular structur e and biology.