Human Cytomegalovirus Reactivation During Lactation: Impact of Antibody Kinetics and Neutralization in Blood and Breast Milk

Abstract

Human cytomegalovirus (HCMV) is shed into breast milk in nearly every seropositive woman during lactation. This reactivation shows mostly a self-limited, unimodal course. The dynamics and functional role of HCMV-specific-IgG in breast milk and in plasma during reactivation are unknown. Milk whey viral loads were monitored with real-time PCR in 18 HCMV-seropositive mothers over two months postpartum. HCMV-antibody binding assays (ECLIA) and antigen-specific immunoblotting were performed from plasma and corresponding milk samples. Epithelial-cell-specific neutralization was used to analyze functional antibodies in plasma- and whey-pools. Viral loads in milk whey showed unimodal courses in 15 of 18 mothers with peak viral loads around one month postpartum. HCMV-specific-IgG-antibodies increased significantly in plasma and milk whey during reactivation. The mean levels of plasma IgG were about 275-fold higher than in whey. Only antibodies against tegument protein p150 were continuously expressed in both compartments. Anti-glycoprotein-B1 IgG-antibodies were variably expressed in whey, but continuously in plasma. Neutralization assays showed 40-fold higher NT-50 values in plasma compared to whey at two months postpartum. During reactivation, HCMV-specific-IgG reactivities and neutralizing capacities are much lower in whey than in plasma. Therefore, their specific role in the decrease and discontinuation of virus-shedding in milk remains unclear.

Human Cytomegalovirus Genome Diversity in Longitudinally Collected Breast Milk Samples

“…As HCMV reactivates strictly locally in the mammary glands during lactation and none of the women showed signs of systemic HCMV reactivation with DNAemia, strain composition and diversity among different compartments (blood and mammary glands) could not be analyzed (Lazar et al, 2020). Local reactivation during lactation is thought to be triggered by invasion of CD14+ monocytes (one site of HCMV latency) into the mammary glands (Maschmann et al, 2015).…”

“…BM samples originated from the BlooMil study (Lazar et al, 2020;Rabe et al, 2020) and were analyzed in collaboration with the Department of Neonatology at the University Children's Hospital, Tuebingen. Samples (~80 ml) from HCMVseropositive mothers of mostly preterm infants were collected within four defined time periods: 10-15, 25-30, 40-45 and 55-60 days postpartum (T1-T4).…”

“…BM was prepared and centrifuged as described previously (Lazar et al, 2020) to separate cellular, whey and fatty fractions. HCMV DNA loads of cell-free whey fraction specimens were determined by quantitative real-time PCR (CMV-R-Gene, bioMeŕieux, lower limit of detection = 600 copies/ml) on a LightCycler (Roche).…”

“…A main source of postnatal HCMV infections is the feeding of raw breast milk (BM), which is considered to be the principal transmission route (Stagno et al, 1980;Doctor et al, 2005;Hamprecht et al, 2008). Local HCMV reactivation during lactation is observed in up to 97% of HCMV-IgG-seropositive mothers, lasting around three months postpartum, and viral DNA can be detected by PCRbased methods in milk whey (DNA lactia) (Hamprecht et al, 2001;Lazar et al, 2020). This unique reactivation mode at the onset of lactation is limited to a local reactivation in the mammary glands, whereas HCMV DNA is not detected in the mother's blood during this period (Mosca et al, 2001;Numazaki et al, 2001;Hamprecht et al, 2003).…”

Impact of breast milk‐acquired cytomegalovirus infection in premature infants: Pathogenesis, prevention, and clinical consequences?

“…Virus neutralization assays demonstrated substantially higher values in plasma compared to whey at 2 months postpartum. No newborn transmission correlates were provided, but the authors concluded that, during reactivation in the post‐partum period, CMV‐specific‐IgG reactivities and neutralizing capacities are much lower in whey than in plasma 32 . These findings suggest that any beneficial effect of maternal antibody on modulating breast milk‐associated transmission may be mediated by protection against infection in the systemic, not mucosal, compartment.…”