Development of serum antibodies during early infancy in rhesus macaques: implications for humoral immune responses to vaccination at birth.

A better understanding of immune responses in human infants could lead to more effective immunization and vaccination strategies in early life. Since antibodies are key components of protective vaccine responses, we examined developmental changes in serum levels of immunoglobulins (IgG, IgA, IgM) in infant rhesus macaques from birth through 6 months of age. As in human infants, macaques are born with high levels of IgG in sera, with rapid increases in serum IgM, yet very slow increases in levels of IgA from birth. We also examined levels of anti-tetanus antibodies in infants born to vaccinated dams to distinguish and track maternal and infant antibodies. These data suggest essentially all serum IgG in newborn infants is derived from the dams, which gradually wanes over a few weeks. In contrast, levels of IgM and IgA appear to all be infant-derived, as evidenced by their low to undetectable levels at birth. In addition, abnormally high levels of serum IgM and IgA were detected in a few infants, which correlated with specific, yet clinically silent disease processes. Our data indicate that newborn macaques have competent immune systems, and are able to produce their own antibodies in response to exposure to environmental antigens immediately upon birth.