Evaluation of the human T-cell leukemia virus type I seropositivity of blood donors by the particle agglutination inhibition test

Mortality among inhabitants of an HTLV-I endemic area in Japan

A community-based cohort study was conducted to clarify the risk of human T-cell leukemia virus type I (HTLV-I) infection for cause-specific deaths. A total of 1,997 individuals (751 men and 1,246 women) aged 30 or older in A-Island, Nagasaki Prefecture, Japan who had voluntarily attended annual mass health examinations, including serum HTLV-I antibody test, were followed up for a mean period of 5.3 years. In a Cox proportional hazards analysis adjusted for age at baseline, the HTLV-I seropositivity was found to be associated with mortality from all causes in men (hazard ratio (HR) 1.89; 95% confidence interval (CI) 1.01-3.54) and women (HR 1.94; 95% CI 1.16-3.22). When the effects of 2 deaths (1 man and 1 woman) from adult T-cell leukemia/lymphoma (ATL) were excluded, the mortality risk decreased slightly but was still significantly or marginally significantly greater than 1 in both men (HR 1.77; 95% CI 0.93-3.37) and women (HR 1.87; 95% CI 1.12-3.12). Further analysis of cause-specific deaths revealed a significant increase in the risk for non-neoplastic diseases but not for neoplasms excluding ATL. These findings suggest that long-term HTLV-I infection represents a health hazard greater than just that for the development of ATL. It was difficult, however, to draw a conclusion regarding the association between HTLV-I infection and cancer risk, because the number of cancer deaths was small and the incidence of cancer was not investigated.

Absence of HTLV-I infection among seronegative subjects in an endemic area of Japan

To examine the prevalence of infection by human T-cell leukemia virus type I (HTLV-I) among seronegative subjects, healthy subjects on Tsushima Island, Japan, where the infection is endemic, were evaluated. A total of 209 healthy adults were examined for HTLV-I provirus in peripheral blood mononuclear cells by the polymerase chain reaction (PCR), as well as for anti-HTLV-I antibodies by the particle agglutination (PA) method, the enzyme-linked immunosorbent assay (ELISA) and by immunofluorescence analysis (IF). A total of 76 subjects were positive and 133 were negative for the provirus, showing a close correlation with the results of 3 assays for anti-HTLV-I serum antibodies. None of the seronegative subjects reacted positively on PCR analysis. These observations indicate that seronegative HTLV-I carriers are rare in an area of Japan in which this viral infection is endemic.

Comparison of immunofluorescence, particle agglutination, and enzyme immunoassays for detection of human T-cell leukemia virus type I antibody in African sera

The effectiveness of four screening tests for detecting antibody to human T-cell leukemia virus type I (HTLV-I) was determined by using 2,700 African serum specimens. The tests studied were indirect immunofluorescence, particle agglutination from Fujirebio, and two enzyme immunoassays, one from Abbott Laboratories that used virus lysate from HUT 102 cells and the other from Cambridge BioScience Corp. that used an env recombinant protein. Positive and doubtful sera were confirmed by Western immunoblot and radioimmunoprecipitation assay with Food and Drug Administration seropositivity criteria. The best results were obtained with the two enzyme immunoassays, which were more sensitive (100 and 98.6% [Abbott and Cambridge, respectively]) and more specific (98.7 and 96.5%). Indirect immunofluorescence exhibited difficulties for reading and interpretation. With particle agglutination, prozone was observed for 9 of 78 HTLV-I-positive serum specimens. False-positives in any of the tests were not linked to cross-reactions with human immunodeficiency viruses. However, confirmation tests remain necessary for HTLV-I screening.