Effects Of Antigen-Specific Maternal Immunity On The Induction Of Responses To The Same Antigen In The Offspring

Maternal immunity (MI) is considered beneficial for the first protection against pathogens, but it also hampers the efficiency of early vaccination. The precise mode of action of MI is not fully understood and therefore studies were performed using a nonreplicating protein antigen, TNP-KLH. Eight White Leghorns were vaccinated repeatedly to obtain high levels of serum antibodies. First the transfer of TNP-specific maternal antibodies into the eggs was examined. TNP-specific antibodies in the yolk were strongly related to the maternal serum titer with a constant ratio of around 3, indicating a concentration step. Then the prehatching uptake of TNP-specific maternal antibodies from the yolk into the chicken serum was examined. Substantial levels were detected from day 18 of incubation, which increased till hatch with a ratio yolk: embryonic serum of around 2, indicating a dilution step. Subsequently age-matched control and MI chickens were primed with KLH-TNP at day 3 or day 24 after hatch and anti-TNP serum titers were determined using ELISA. After priming at day 3, controls showed no detectable response, whereas in MI chickens only TNP-specific IgG derived from the mother were found. After priming at day 24, control chickens showed high levels of TNP-specific IgM, whereas MI chickens did not have any detectable IgM response, even though levels of TNP-specific maternal IgG were undetectable. The lack of immune reactivity of maternal immune chickens was seen until the age of 56 days. Booster immunization at 3- weeks after the priming did not repair the lack of immune response. In view of the absence of TNP-specific maternal antibodies in the young chicks, these results indicate that the suppressive effects of maternal immunity are due to mechanisms additional to IgG antibodies transferred via the yolk.