Seronegative human T‐cell lymphotropic virus 1 carriers in blood banks: A potential viral source for silent transmission?

Background and Objectives Transfusion‐transmitted viruses count among the greatest threats to blood safety. In Argentina, current laws oblige testing all donated blood for the presence of antibodies against human T‐cell lymphotropic viruses 1 and 2 (HTLV‐1/2). In endemic zones of the country, a high rate of seronegative HTLV‐1 individuals with clear evidence of infection because of symptoms and/or presence of tax sequences of HTLV‐1 and/or IgG anti‐Tax antibodies has been recently described. Migration from endemic to nonendemic zones of Argentina is very frequent. Materials and Methods During a 1‐year period, in the blood bank of Córdoba city, we performed molecular screening of all donors who were born in or arose from endemic zones for HTLV‐1/2 in Argentina and neighbouring countries. Results By screening 219 bp of HTLV‐1/2 tax gene, 0.6% (2/317) of the blood donors proved to be positive for HTLV‐1 tax sequence. One of the donors presented anti‐Tax antibodies, demonstrating the transcriptional activity of the tax gene, and the other donor was also positive for LTR and pol gene sequences. The HTLV‐1 genetic analysis of the LTR sequence determined that it belonged to the Cosmopolitan subtype HTLV‐1aA. Conclusion These findings suggest potential limitations of some currently approved screening assays for HTLV‐1 detection applied in some donor populations and the possibility of an HTLV‐1 seronegative carrier state with the potential for silent transmission by blood.