Antiviral activity of colostrum and serum immunoglobulins A and G

Maternal immunization with a DNA vaccine candidate elicits specific passive protection against post-natal Zika virus infection in immunocompetent BALB/c mice

Zika virus (ZIKV) infection is closely associated in the fetus with microcephaly and in the adults with Guillain-Barré syndrome and even male infertility. It is an urgent international priority to develop a safe and effective vaccine that offers protection to both women of childbearing age and their children. In this study, female immunocompetent BALB/c mice were immunized with a DNA-based vaccine candidate, pVAX1-ZME, expressing the prM/E protein of ZIKV, and the immunogenicity for maternal mice and the post-natal protection for suckling mice were evaluated. It was found that administration with three doses of 50 μg pVAX1-ZME via in vivo electroporation induced robust ZIKV-specific cellular and long-term humoral immune responses with high and sustained neutralizing activity in adult mice. Moreover, using a maternal immunization protocol, neutralizing antibodies provided specific passive protection against ZIKV infection in neonatal mice and effectively inhibited the growth delay. This vaccine candidate is expected to be further evaluated in higher animals, and maternal vaccination shows great promise for protecting both women of childbearing age and their offspring against post-natal ZIKV infection. The vaccinated mothers and ZIKV-challenged pups provide key insight into Zika vaccine evaluation in an available fully immunocompetent animal model.

Maternal antibodies in breast milk protect the child from enterovirus infections

OBJECTIVE

Enterovirus infections are frequent in infants and may cause severe complications. We set out to assess whether breastfeeding can protect against these infections and whether such an effect is related to maternal antibodies in breast milk or in the peripheral circulation of the infant.

METHODS

One hundred fifty infants who were prospectively followed up from birth were monitored for enterovirus infections. The duration of breastfeeding was recorded, and maternal breast milk and blood samples were regularly taken at 3-month intervals for the detection of enterovirus antibodies and RNA. Maternal serum was available from early pregnancy, delivery, and 3 months postpartum.

RESULTS

Enterovirus infections were frequent and were diagnosed in 43% of infants before the age of 1 year and in 15% of the mothers during pregnancy. Infants exclusively breastfed for >2 weeks had fewer enterovirus infections by the age of 1 year compared with those exclusively breastfed for < or =2 weeks (0.38 vs 0.59 infections per child). High maternal antibody levels in serum and in breast milk were associated with a reduced frequency of infections. This effect was seen only in those infants breastfed >2 weeks, indicating that breast milk antibodies mediate this effect. Enterovirus RNA was not found in any of the breast milk samples.

CONCLUSIONS

These results suggest that breastfeeding has a protective effect against enterovirus infections in infancy. This effect seems to be mediated primarily by maternal antibodies in breast milk.

Salivary antibody responses to oral and parenteral vaccines in children

Salivary IgA antibody to poliovirus and tetanus toxoid was measured in whole salivas of 151 children between 2 and 48 months of age from North America and from Scandinavia. Children from urban and suburban populations in the greater Boston, MA, area receive both oral poliovaccine and a parenteral injection with tetanus toxoid (TT), initially at approximately 2 months of age. Children from Göteborg, Sweden, initially receive parenteral injections of TT at 2 months of age and parenteral injections of killed polio vaccine initially at 9 to 10 months of age. Twenty-six percent of the Boston subjects who were less than 12 months old had detectable salivary IgA antibody to poliovirus after oral immunization. In contrast, within the first year after parenteral immunization with killed poliovirus, the Swedish group had detectable salivary antibody in 9% (1 of 13) of the subjects. Forty to 65% of the children in the older Boston-area age groups had positive salivary IgA antibody levels to this antigen. No differences were seen in salivary IgA antibody to TT among the three populations. By 36 months of age at least 50% of all populations had detectable salivary antibody to TT. The ratio of enzyme-linked immunosorbent assay (ELISA) activity using rabbit anti-human secretory component versus rabbit anti-human alpha chain was significantly higher in subjects less than 12 months of age compared with older groups. This suggested either that free secretory component was binding to tetanus toxoid or that secretory antibody of isotypes other than IgA was present in these youngest subjects.

Rapid diagnosis of echovirus type 33 meningitis by specific IgM detection using an enzyme linked immunosorbent assay (ELISA)

During an outbreak of meningitis in France (in the Lyon area), from June to October 1982, serum and stool samples were collected from 227 patients. An enzyme-linked immunosorbent assay (ELISA) for titrating IgG and IgM antibodies anti-echovirus type 33 was developed and compared with the virus isolation technique, and with the titration of neutralizing antibodies. In 39 patients excreting echovirus 33 in faeces, the ELISA test allowed a positive serodiagnosis in 85% of the cases by detection of specific IgM (64% of the cases) and by seroconversion (21%). Compared with the neutralization (Nt) test, ELISA was found to be more sensitive. The antibody titres in ELISA were over 50 times higher and detected earlier than the neutralizing antibodies. This early immune response allowed a rapid diagnosis by specific IgM detection in the acute sera collected within 8 days after the appearance of the clinical symptoms in more than 50% of the 97 patients examined, whereas the Nt test allowed a positive serodiagnosis in only 32% of the patients. The use of a caesium chloride purified antigen insured the specificity of the reactions.

Antimicrobial properties and microbial contaminants of breast milk--an update

A review of recent studies of antibacterial, antiviral and antiprotozoan factors in human breast milk is presented. Also reviewed are the microbial contaminants that have been detected in human milk with a particular focus on cytomegalovirus and rubella virus, both of which have recently been shown to infect infants via breast milk.

Neonatal rotavirus infection: role of lacteal neutralising alpha1-anti-trypsin and nonimmunoglobulin antiviral activity in protection

Expressed breast milks (EBMs) were collected from mothers of rotavirus (RV)-excreting babies and from mothers whose babies were RV free during an outbreak of asymptomatic RV infection in a newborn nursery to determine the role of lacteal anti-RV neutralising activity, alpha1-anti-trypsin activity, and nonimmunoglobulin antiviral factor in protection of neonates from RV infection, and although all of the above factors were present in the majority of the EBMs, no correlation could be found between their presence in EBM and protection from RV infection. A significant rise in both neutralising activity and subgroup 2 antibodies, was demonstrated in the EBM of one mother who experienced a subgroup 2 RV-associated diarrhoea during lactation. However, the alpha1-anti-trypsin activity and the nonimmunoglobulin antiviral levels remained the same. The importance of these factors in passive immunity with reference to virus dose is discussed.

Detection of human cytomegalovirus- specific IgA antibodies in colostrum by enzyme-linked immunosorbent assay (ELISA)

Fifty women were examined after delivery for the prevalence of antibodies to human cytomegalovirus in colostrum and sera. Eighty percent of them had specific CMV IgG antibodies in the sera, as determined by the immunoperoxidase antibody to membrane antigen (IPAMA) technique. Of the CMV-seropositive women, 60% had specific CMV IgA antibodies in high titer in the colostrum as determined by enzyme-linked immunosorbent assay (ELISA). In only two of the seropositive women were specific CMV IgA antibodies detected in the sera as well. The significance of specific CMV IgA antibodies in colostrum as protection against perinatal infection and the mechanism of this production will be discussed.

Bronchomammary axis in the immune response to respiratory syncytial virus

The products of lactation from 26 nursing mothers were sequentially examined over several months for the presence or appearance of antibodies directed against respiratory syncytial virus. Antiviral IgM and IgG were rarely identified in either colostrum or milk. RSV-specific IgA was found in 75% (18/24) of specimens of colostrum; 40% (6/15) and 59% (4/7) of milk samples obtained at three and six months still contained specific IgA antibody. The latter increase was felt to represent boosting of exposed individuals when the virus was present in the community. Infection with the virus was documented in two mothers. Both had specific IgG, IgM, and IgA antibody responses in serum and nasopharyngeal secretions, but response in milk was limited to IgA. These data confirm that antibody to a specific respiratory tract pathogen is present in the products of lactation, that the specific activity is mainly of the IgA class, and that booster responses in milk are exclusively of the IgA class. Since RSV appears to replicate only in the respiratory tract, it is suggested that viral specific antibody activity observed in the mammary gland may be derived from the bronchopulmonary lymphoid tissue.