HTLV-I infection among relatives of patients with adult T-cell Leukemia/Lymphoma in Brazil: Analysis of infection transmission

We examined the presence of HTLV-I infection among 66 family members of 13 patients with well documented ATL to investigate the routes of HLTV-I trans mission in a Southeast region of Brazil. HTLV-I infection was screened by a n enzyme immunossay (ELISA) test and an repeatedly positive or indeterminat e ELISA samples were further tested by a Western-Blot (WB) technique. Indet erminate and inconclusive WE samples were confirmed by a polymerase chain r eaction (PCR). ELISA results showed that 40 (60.6%) individuals were not in fected; 16 (24.2%) were positive; and 10 (15.2%) were undetermined. Among 1 6 ELISA positive subjects, 14 (87.5%) were confirmed to be positive by WE w hile 2 (12.5%) showed inconclusive results. Based on the laboratory data, q uestionnaire analysis, and family/epidemiological studies, we concluded tha t HTLV-I vertical transmission occurred in 6 of the 13 families. In 3 of th ese 6 families, the horizontal transmission also could be demonstrated. An isolated horizontal transmission was detected in one family, and in 6 famil ies we did not find any infected family member. All HTLV-I-infected persons were clinically asymptomatic. The occurrence of an effective HTLV-I vertic al transmission detected by the present study suggest that HTLV-I infection is endemic in the Southeast region of Brazil. Consistent with the modes of transmission, the HTLV-I antibody seroprevalence was greater in relatives of ATL patients than in the general blood donor Brazilian population (0.4%) . In addition, the present data suggest that HTLV-I carries a high infectiv ity rate but a low virulence.