Breast-feeding mothers frequently transmit cytomegalovirus (CMV) to preterm infants of very low birth weight. Current recommendations for prevention of virus transmission are based on data published 20 y ago in the context of human milk banking. Two recent clinical trials examined storage of breast milk at ?20°C to reduce virus transmission. However, in both studies, CMV transmission occurred. Using sensitive tools like quantitative PCR, CMV pp67 late mRNA assay, and a high-speed, centrifugation-based microculture assay for quantification of CMV infectivity, we reassessed the virological and biochemical characteristics of freeze-storing breast milk at ?20°C, compared it with traditional Holder pasteurization (30 min at 62.5°C), and a new short-term pasteurization (5 s at 72°C) based on the generation of a milk film. Both heat treatment procedures were able to destroy viral infectivity and pp67 RNA completely. Preliminary results showed short-term heat inactivation below 72°C was less harmful in reducing the activity of marker enzymes than Holder pasteurization. Freezing breast milk preserved the biochemical and immunologic quality of the milk; however, late viral RNA and viral infectivity was also preserved. Compared with viral DNA, CMV-RNA more directly reflects infectious CMV in human milk samples. Further studies are necessary to evaluate short-term heat treatment below 72°C as an effective tool for prevention of CMV transmission.Abbreviations: AP, alkaline phosphatase; CMV, cytomegalovirus; HFF, human foreskin fibroblasts; IE, immediate early; NASBA, nucleic acid sequence–based amplification; p.p., post partum; sIgA, secretory IgA; VLBW, very low birth weight
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