Revaccination of neonatal calves with Mycobacterium bovis BCG reduces the level of protection against bovine tuberculosis induced by a single vaccination.
Cattle may provide a suitable model for testing ways of improving tuberculosis vaccine efficacy in human infants. A vaccination and challenge study was undertaken in calves to determine the optimal time to vaccinate neonatal animals with Mycobacterium bovis bacillus Calmette-Guérin (BCG) for protection against tuberculosis and to determine whether revaccination with BCG was beneficial. Calves (10 per group) were vaccinated with BCG within 8 h of birth or at 6 weeks of age, when immune responses to antigens of environmental mycobacteria were detectable, or vaccinated at birth and revaccinated at 6 weeks. A control group was not vaccinated. BCG vaccination at birth induced strong antigen-specific gamma interferon (IFN-gamma) and interleukin-2 (IL-2) responses and antigen-specific activation in CD4(+), CD8(+), and WC1(+) gammadelta T-cell subsets from blood. The proportions of animals per group with macroscopic tuberculous lesions after challenge were 0/10 for BCG at birth, 1/9 for BCG at 6 weeks, 4/10 for the revaccinated group, and 10/10 for the nonvaccinated group. There was no significant difference in the levels of protection between groups vaccinated at birth or at 6 weeks, while animals vaccinated both at birth and at 6 weeks had significantly less protection than those vaccinated only at birth. The revaccinated calves that subsequently developed tuberculous lesions had significantly stronger IFN-gamma and IL-2 responses to bovine purified protein derivative after the BCG booster than those in the same group that did not develop lesions. The results indicated that BCG vaccination at birth induced a high level of immunity and that the sensitization of very young animals to antigens of environmental mycobacteria by 6 weeks of age did not affect the effectiveness of BCG. However, BCG revaccination of these young animals was contraindicated.
AgResearch, Wallaceville Animal Research Centre, Upper Hutt, New Zealand. bryce.buddle@agresearch.co.nz
B M
BM
Buddle
D N
DN
Wedlock
N A
NA
Parlane
L A L
LA
Corner
G W
GW
De Lisle
M A
MA
Skinner
D000818:Animals; D000831:Animals, Newborn; D000907:Antibodies, Bacterial / Q000097:blood; D001500:BCG Vaccine / Q000276:immunology*; D002417:Cattle; D007371:Interferon-gamma / Q000096:biosynthesis; D007376:Interleukin-2 / Q000096:biosynthesis; D015847:Interleukin-4 / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis; D014373:Tuberculin / Q000276:immunology; D014374:Tuberculin Test; D014380:Tuberculosis, Bovine / Q000276:immunology / Q000517:prevention & control*; D014611:Vaccination / Q000662:veterinary*
D000907:Antibodies, Bacterial; D001500:BCG Vaccine; D007376:Interleukin-2; D012333:RNA, Messenger; D015375:Receptors, Interleukin-2; D014373:Tuberculin; D015847:Interleukin-4; D007371:Interferon-gamma