Pooling of samples for seroepidemiological surveillance of human T-cell lymphotropic virus types I and II

We evaluated a straight forward pooling strategy for antibody screening of HTLV-I/II, using panels of sera from various parts of the world including a total of 43 HTLV-I and 54 HTLV-II positive specimens. Four antibody screen ing assays were included in the evaluation: the HTLV-I/II GE 80/81 (Murex D iagnostics), the HTLV-I/HTLV-II Ab Capture ELISA (Ortho Diagnostics), the H TLV-1/11 ELISA 3.0 (Genelabs Diagnostics) and the Serodia HTLV-I (Fujirebio ). The Murex and Ortho assays represent a new generation of HTLV screening tests with a sandwich format incorporating both HTLV-I and HTLV-II syntheti c and/or recombinant peptide antigens. The Genelabs assay is an indirect EL ISA with recombinant HTLV-I and -II antigens and Serodia is a particle aggl utionation assay with HTLV-I whole viral lysate. Each HTLV-positive sample was included in pools of 1/1 up to 1/16, in two-fold steps made in normal H TLV-negative blood donor ser-um from one up to nine donors. For HTLV-I, wit h the exception of one false negative sample in dilution 1/16 with Genelabs ELISA, all assays were positive at all dilutions. The Murex assay had abso rbance values at maximum levels for all samples at all dilutions. The other assays had gradually decreasing absorbance values although clearly above c ut-off. For HTLV-II, the Murex assay correctly detected all samples to dilu tion 1/16 despite gradually decreasing signals. The Serodia assay had 100% sensitivity to dilution 1/4 while at 1/8 and 1/16 it decreased 82 and 80%, respectively. The Genelabs ELISA had gradually decreasing sensitivity for H TLV-II from 98 (1/1) to 33% (1/16) while the Ortho assay detected all speci mens at all dilutions in a limited set of samples tested. Taken together, t his evaluation has shown that pooling of samples may be an appropriate stra tegy for serosurveillance of HTLV. It is, however, crucial to limit the num ber of samples and to choose assays that allow the dilution caused by the p ooling. Using the best performing assays in this evaluation for pools of e. g. five samples would leave a reasonable safety margin. (C) 2001 Elsevier S cience BN. All rights reserved.