Data from: Revaccination of cattle with Bacille Calmette-Guérin two years after first vaccination when immunity has waned, boosted protection against challenge with Mycobacterium bovis

In both humans and animals, controversy exists concerning the duration of
protection induced by BCG vaccine against tuberculosis (TB) and whether
revaccination enhances protection. A long-term study was undertaken to
determine whether BCG-vaccinated calves would be protected against
challenge with Mycobacterium bovis 2½ years after vaccination and to
determine the effect of revaccination after 2 years. Seventy–nine calves
were divided into five groups (n = 15–17 calves/group) with four of the
groups vaccinated subcutaneously with 105 CFU of BCG Danish at 2–4 weeks
of age and the fifth group serving as non-vaccinated controls. Three of
the four BCG-vaccinated groups were revaccinated 2 years after the initial
vaccination. One BCG-vaccinated group was revaccinated with BCG. A second
group was vaccinated subcutaneously with a TB protein vaccine consisting
of biopolyester particles (Biobeads) displaying two mycobacterial
proteins, ESAT-6 and Antigen 85A, mixed with an adjuvant. A third group
was vaccinated with TB proteins from M. bovis culture filtrate, mixed with
an adjuvant. Twenty-three weeks after the BCG revaccination, all animals
were challenged endotracheally with virulent M. bovis and a further 13
weeks later, animals were killed and necropsied to determine protection
against TB. The BCG-vaccinated animals produced positive tuberculin caudal
fold intradermal (15 of 62 animals) and IFN-γ TB test responses (six of 62
animals) at 6 months after vaccination, but not at subsequent time-points
compared to the non-vaccinated animals. Calves receiving a single
vaccination with BCG vaccine 2½ years prior to challenge were not
protected against TB, while those revaccinated with BCG 2 years after the
initial vaccination displayed significant reductions in lung and pulmonary
lymph node lesion scores compared to the non-vaccinated animals. In
contrast, no reduction in lesion scores was observed in the animals
revaccinated with the TB protein vaccines with their immune responses
biased towards induction of antibody.