Positive serum IgG responses did not appear until day 30 in
animal no. 147. Positive reactions developed on day 54 in
animals no. 127 and 199 and day 102 in animal no. 143
(Fig. 1A). The IgM and IgA responses were borderline
positive throughout the study, with the caveat that the
cutoff values for the IgM and IgA ELISAs have not been
validated and the cutoff value of the IgG ELISA was used.