Humoral immune response against antigen 60 in BCG-vaccinated infants.

An ELISA assay based on the A-60 antigen complex from Mycobacterium bovis BCG cytoplasm was used to detect anti-mycobacterial antibodies of different classes in the sera of 63 BCG-vaccinated infants during the 6-month post-vaccination period. The mean IgM and IgA levels increased, whereas the mean IgG level decreased after BCG vaccination. However, in a minority of cases only Ig levels were above the cut-off line: this was true for IgM in 11/63 (17%) cases and for IgA in 14/63 (22%) of cases but none of the tested infants was anti-A60 IgG ELISA positive. Fifty-two infants (83%) were tuberculin-positive eight weeks after vaccination, and no significant difference in mean antibody levels of tuberculin-positive and negative cases was observed, except for IgG (p < 0.05).