Cytomegalovirus (CMV) inactivation in breast milk:: Reassessment of pasteurization and freeze-thawing

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 degreesC 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 degreesC, compared it with traditional Holder pasteurization (30 min at 62.5 degreesC), and a new short-term pasteurization (5 s at 72 degreesC) 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 degreesC was less harmful in reducing the activity of marker enzymes than Holder pasteurization. Freezing breast milk pre-served 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 degreesC as an effective tool for prevention of CMV transmission.