Mother-to-Child Transmission of Human T-Cell Leukemia Virus Type 1: Mechanisms and Nutritional Strategies for Prevention

SIMPLE SUMMARY: Mother-to-child transmission (MTCT) of human T-cell leukemia virus type 1 (HTLV-1) is a major cause of adult T-cell leukemia (ATL). Owing to the poor prognosis of ATL and the fact that more than one million people have been infected with this virus, the HTLV-1 antibody screening test was established in Japan in 2010 for all pregnant women to detect carriers and prevent MTCT. Because breastfeeding is the most common route of postnatal MTCT, exclusive formula feeding is widely used as a measure to prevent MTCT. Recently, it was reported that there is no obvious difference in the efficacy of short-term breastfeeding for ≤3 months in preventing MTCT compared to that in exclusive formula feeding, and that a duration of breastfeeding that does not exceed four months can be effective for preventing MTCT. ABSTRACT: Approximately 95% of mother-to-child transmission (MTCT) of human T-cell leukemia virus type-1 (HTLV-1) is derived from prolonged breastfeeding, which is a major cause of adult T-cell leukemia (ATL). Exclusive formula feeding (ExFF) is therefore generally used to prevent MTCT. A recent cohort study revealed that 55% of pregnant carriers chose short-term breastfeeding for ≤3 months in Japan. Our meta-analysis showed that there was no significant increase in the risk of MTCT when breastfeeding was carried out for ≤3 months compared with ExFF (pooled relative risk (RR), 0.72; 95% confidence interval (CI), 0.30–1.77), but there was an almost threefold increase in risk when breastfeeding was carried out for up to 6 months (pooled RR, 2.91; 95% CI, 1.69–5.03). Thus, short-term breastfeeding for ≤3 months may be useful in preventing MTCT. Breastmilk is the best nutritional source for infants, and any approach to minimizing MTCT by avoiding or limiting breastfeeding must be balanced against the impact on the child’s health and mother–child bonding. To minimize the need for nutritional interventions, it is necessary to identify factors that predispose children born to carrier mothers to MTCT and thereby predict MTCT development with a high degree of accuracy.