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

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.

Keywords: exclusive formula feeding; frozen and thawed breastmilk feeding; human T cell leukemia virus type 1; mother-to-child transmission; short-term breastfeeding; transplacental transmission.

Figure 1

Flowchart to determine HTLV-1 carriers among pregnant women. CLEIA, chemiluminescent enzyme immunoassay; CLIA, chemiluminescent immunoassay; ECLIA, electro-chemiluminescent immunoassay; PA, particle agglutination; WB, Western blot; LIA, line immunoassay; PCR, polymerase chain reaction.

Figure 2

Forest plot of the risk ratios of HTLV-1 MTCT in the ‘STBF ≤3 months’ group compared with that of the ExFF group. STBF, short-term breastfeeding; ExFF, exclusive formula feeding; M–H, Mantel–Haenszel; CI, confidence interval; RR, risk ratio; MTCT, mother-to-child transmission; Events, number of cases with mother-to-child transmission; Total, number of children born to carrier mother; Weight, influence of studies on overall meta-analysis. The figure is reproduced from Miyazawa et al. [112].

Figure 3

Forest plot of the risk ratios of HTLV-1 MTCT in the ‘STBF ≤6 months’ group compared with that of the ExFF group. STBF, short-term breastfeeding; ExFF, exclusive formula feeding; M–H, Mantel–Haenszel; CI, confidence interval; RR, relative risk; MTCT, mother-to-child transmission; Events, number of cases with mother-to-child transmission; Total, number of children born to carrier mother; Weight, influence of studies on overall meta-analysis. The figure is reproduced from Miyazawa et al. [112].

Figure 4

Forest plot of the risk ratios of HTLV-1 MTCT in the FTBMF group compared with that of the ExFF group. FTBMF, frozen-thawed breastmilk feeding; ExFF, exclusive formula feeding; M–H, Mantel–Haenszel; CI, confidence interval; RR, relative risk; MTCT, mother-to-child transmission; Events, number of cases with mother-to-child transmission; Total, number of children born to carrier mother; Weight, influence of studies on overall meta-analysis. The figure is reproduced from Miyazawa et al. [112].