Neutralizing activity and secretory IgA antibodies reactive with rotavirus SA-11 (serotype G3) in colostrum and milk from Brazilian women

Background: Rotavirus is an important aetiological agent for severe diarrhoea in infants and young children worldwide. Anti-rotavirus antibodies in human colostrum and milk may interfere with rotavirus vaccination seroconversion. Aims: To verify the presence of anti-rotavirus secretory IgA antibodies (SIgA) and the neutralizing capacity of 30 colostrum and 30 milk samples from Brazilian women in two different centres and analyze their persistence throughout lactation. Methods: Colostrum and milk samples from healthy nursing mothers were tested for the presence of anti-rotavirus SIgA using conventional ELISA and their capacity to neutralize rotavirus using MA-104 cell cultures. Total IgA concentrations and anti-rotavirus SIgA levels were measured in samples collected from three mothers during 90 or 240 days of the lactation period. Results: Colostrum samples showed higher levels of anti-rotavirus SIgA and higher neutralizing ability than in milk. However, these antibodies levels were not statistically different. In addition, there was no correlation between antibody levels and the neutralizing activity observed in colostrum and milk samples. Follow-up of three mothers demonstrated the persistence of anti-rotavirus and total IgA levels throughout lactation. Conclusions: These results support the encouragement of breastfeeding as a mechanism of protection against rotavirus infection in lactating infants. Components other than SIgA antibodies might play an important role in virus neutralization.