Revaccination of Cattle with Bacille Calmette-Guerin Two Years after First Vaccination when Immunity Has Waned, Boosted Protection against Challenge with Mycobacterium bovis: e106519

• Published in: PloS one Vol. 9; no. 9
• Main Authors: Parlane, Natalie A, Shu, Dairu, Subharat, Supatsak, Wedlock, D Neil, Rehm, Bernd HA, Lisle, Geoffrey Wde, Buddle, Bryce M
• Format: Journal Article
• Language: English
• Published: 01-09-2014
• Subjects: Mycobacterium bovis
• ISSN: 1932-6203
• DOI: 10.1371/journal.pone.0106519

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 21/2 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- gamma 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 21/2 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.