Western blotting (WB) for human T cell leukemia virus type 1 (HTLV-1) is performed to confirm anti-HTLV-1 antibodies detected at the initial screening of blood donors and in pregnant women. However, the frequent occurrence of indeterminate results is a problem with this test. We therefore assessed the cause of indeterminate WB results by analyzing HTLV-1 provirus genomic sequences. A quantitative PCR assay measuring HTLV-1 provirus in WB-indeterminate samples revealed that the median proviral load was approximately 100-fold lower than that of WBpositive samples (0.01 versus 0.71 copy/100 cells). Phylogenic analysis of the complete HTLV-1 genomes of WB-indeterminate samples did not identify any specific phylogenetic groups. When we analyzed the nucleotide changes in 19 HTLV-1 isolates from WB-indeterminate samples, we identified 135 single nucleotide substitutions,

The residual number of HTLV-1-infected cells after LR is substantially lower than the viral load necessary for TT-HTLV-1. LR therefore appears to be effective in minimizing the incidence of TT-HTLV-1.

Background: The reliable diagnosis of human T-cell leukemia virus type 1 (HTLV-1) infection is important, particularly as it can be vertically transmitted by breast feeding mothers to their infants. However, current diagnosis in Japan requires a confirmatory western blot (WB) test after screening/primary testing for HTLV-1 antibodies, but this test often gives indeterminate results. Thus, this collaborative study evaluated the reliability of diagnostic assays for HTLV-1 infection, including a WB-based one, along with line immunoassay (LIA) as an alternative to WB for confirmatory testing. Results: Using peripheral blood samples from blood donors and pregnant women previously serologically screened and subjected to WB analysis, we analyzed the performances of 10 HTLV-1 antibody assay kits commercially available in Japan. No marked differences in the performances of eight of the screening kits were apparent. However, LIA determined most of the WB-indeterminate samples to be conclusively positive or negative (an 88.0% detection rate). When we also compared the sensitivity to HTLV-1 envelope gp21 with that of other antigens by LIA, the sensitivity to gp21 was the strongest. When we also compared the sensitivity to envelope gp46 by LIA with that of WB, LIA showed stronger sensitivity to gp46 than WB did. These findings indicate that LIA is an alternative confirmatory test to WB analysis without gp21. Therefore, we established a novel diagnostic test algorithm for HTLV-1 infection in Japan,

The Mirasol PRT system inactivated greater than 2 to 3 logs of live HEV in PLTs and can potentially be used to lower the possibility of blood-borne HEV transmission. The G3 and G4 HEV inocula identified in this study and the hepatoma cell culture system provide a new means to assess HEV infectious titer and to evaluate other pathogen reduction strategies.

Quantitative PCR (qPCR) analysis of human T-cell leukemia virus type 1 (HTLV-1) was used to assess the amount of HTLV-1 provirus DNA integrated into the genomic DNA of host blood cells. Accumulating evidence indicates that a high proviral load is one of the risk factors for the development of adult T-cell leukemia/lymphoma and HTLV-1-associated myelopathy/tropical spastic paraparesis. However, interlaboratory variability in qPCR results makes it difficult to assess the differences in reported proviral loads between laboratories. To remedy this situation, we attempted to minimize discrepancies between laboratories through standardization of HTLV-1 qPCR in a collaborative study. TL-Om1 cells that harbor the HTLV-1 provirus were serially diluted with peripheral blood mononuclear cells to prepare a candidate standard. By statistically evaluating the proviral loads of the standard and those determined using in-house qPCR methods at each laboratory, we determined the relative ratios of the measured values in the laboratories to the theoretical values of the TL-Om1 standard. The relative ratios of the laboratories ranged from 0.84 to 4.45. Next, we corrected the proviral loads of the clinical samples from HTLV-1 carriers using the relative ratio. As expected, the overall differences between the laboratories were reduced by half, from 7.4-fold to 3.8-fold on average, after applying the correction. HTLV-1 qPCR can be standardized using TL-Om1 cells as a standard and by determining the relative ratio of the measured to the theoretical standard values in each laboratory. Human T-cell leukemia virus type 1 (HTLV-1) is present in certain regions of endemicity, including sub-Saharan Africa, the Caribbean, parts of South America, the Middle East, Melanesia, and southwest Japan (1, 2). HTLV-1 mainly infects vertically from infected mothers to children through breastfeeding and horizontally between adults by sexual intercourse and transmission through transfusions with blood products. Although the majority of infected people live without any symptoms, some HTLV-1 carriers suffer from adult T-cell leukemia (ATL), HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), and HTLV-1 uveitis/HTLV-1-associated uveitis after a long period of latency (3).HTLV-1 mainly infects CD4-positive peripheral blood cells, and the provirus is integrated into the host genome. Generally, HTLV-1 infection is determined by serological testing. Detection of proviral DNA in peripheral blood mononuclear cells (PBMCs) by PCR is one of the methods to detect the infection. Quantitation of both the provirus and a cellular gene in PBMCs by TaqMan quantitative PCR (qPCR) enables calculation of the percentages of