HUMAN CYTOMEGALOVIRUS-INFECTION OF BREAST-MILK

Human cytomegalovirus is the most common cause of congenital and perin atal infections throughout the world. Primary infection with human cyt omegalovirus usually follows a benign course, but the virus remains la tent or persistent in the host cell thereafter. Understanding the epid emiology of human cytomegalovirus is a key element in the development of strategies for prevention of infection. Although the actual sites o f latency or persistence of human cytomegalovirus infections are still controversial, peripheral blood mononuclear cells and endothelial cel ls appear to be major sites of infection. Persistent: infections cause d by human cytomegalovirus could be augmented by a decrease in major h istocompatibility complex expression as well as by virus-mediated immu ne dysfunction. It is possible that specific cellular interactions as well as production of several cytokines are necessary for the reactiva tion of human cytomegalovirus. Breast-fed infants are susceptible to h uman cytomegalovirus infection from breast milk. Human cytomegalovirus was isolated more frequently from breast milk at more than 1 month af ter delivery than from colostrum or early breast milk. Human cytomegal ovirus DNA was also not detected in colostrum, but was found in breast milk samples 1 month after delivery. To clarify the role of milk cell s and whey in vertical infection by breast feeding, we separated breas t milk into milk cells and whey and examined each fraction. Human cyto megalovirus was isolated more frequently from milk whey samples than f rom cell samples. Human cytomegalovirus particle shedding into whey ma y be more important in vertical infection by breast milk than cell-to- cell transmission. The supernatant of colostrum did not exert an inhib itory effect on human cytomegalovirus-infected cells. Serum levels of cell free soluble interleukin-2 receptor of mothers with DNA-positive milk at 1 month after delivery were significantly higher than those of mothers with DNA-negative milk. It is likely that levels of factors s uch as soluble interleukin-2 receptor in serum are related to the reac tivation of human cytomegalovirus which occurs locally in the mammary gland of the lactating mother after delivery. This minireview focuses on recent advances in the study of human cytomegalovirus infection of breast milk.