Laboratory Characterization of Human T Cell Lymphotropic Virus Types 1 (HTLV-1) and 2 (HTLV-2) Infections in Blood Donors from Sao Paulo, Brazil

Serologic screening for human T cell lymphotropic virus types 1/2 (HTLV-1/2) infection in blood donors has been recently introduced in Brazil. Analysis of 351,639 blood donations in Sao Paulo from January 1992 to October 1993 identified 1,063 positive (0.30%) and 2,238 indeterminate (0.63%) samples based on serologic confirmation using a 21e Western blot. A detailed analysis (serologic, molecular, and virologic), based on a laboratory diagnostic algorithm for characterization of HTLV-1 and HTLV-2 infections was undertaken in 50 seropositive or seroindeterminate blood donors. Modified serologic assays (2.3 Western blot that incorporate type-specific recombinant peptides) performed in 29 HTLV-1/2 positive and 21 HTLV-1/2 indeterminate donors with the 21e Western blot identified 25 as infected with HTLV-1, four with HTLV-2, five with untypable HTLV-1/2, 15 as HTLV-1/2 indeterminate, and one as seronegative. Polymerase chain reaction (PCR) analysis using DNA amplification of proviral pol and tax sequences from peripheral blood mononuclear cells confirmed HTLV-1 and HTLV-2 infections in all 2.3 Western blot seropositive donors; of the five serologically untypable donors, three were confirmed to be HTLV-1 positive, one HTLV-2 positive, and one negative by PCR. All of the seroindeterminate donors were also negative by PCR. Furthermore, HTLV-1 could be isolated in cocultures from 10 of 18 infected donors. Cell lines developed from two HTLV-1-infected donors were of T cell phenotype (CD2+, CD3+), exhibiting surface markers of activated CD4 cells (CD4+ CD25+ HLA-DR+). Thus, we provide evidence for the high seroprevalence of HTLV infection in blood donor population in Sao Paulo, Brazil compared with North American donors and propose a comprehensive serologic and genotypic diagnostic algorithm for HTLV-infected donors that has strong implications for counseling of these individuals.