Page 761 - Veterinary Immunology, 10th Edition

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FIG. 23.10 Effect of the presence of maternal antibodies to canine
parvovirus in 653 puppies on their response to a modified live
parvovirus vaccine. The pre-vaccination antibody titer profoundly
inhibits the response of the puppies to the vaccine. (From Carmichael
LE: Compend Contin Educ Prac Vet 5:1043-1054, 1983.)

Several different mechanisms of this suppression have been
suggested. The simplest is the rapid neutralization of live viral

vaccines by the maternal antibody. This would prevent viral
replication and provide insufficient antigen to prime neonatal B
cells. However, data from human infants and domestic mammals
indicate that sufficient antigen is present to prime T cells. Likewise,

this mechanism could not account for inhibition of the immune
response to nonliving vaccines.
A second proposed mechanism suggests that the inhibition
results from antibodies binding to B cell Fc receptors (CD32) and

blocking BCR signaling (see Fig. 20.9). However, studies of mice
whose Fc receptors have been deleted (FcR knockout mice) have
shown that the ability of maternal antibodies to inhibit antibody
responses is unaffected. This clearly cannot be the mechanism

involved.
A third suggested mechanism is that maternal antibodies simply

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