Intranasal mucosal boosting with an adenovirus-vectored vaccine markedly enhances the protection of BCG-primed guinea pigs against pulmonary tuberculosis.
BACKGROUND
Recombinant adenovirus-vectored (Ad) tuberculosis (TB) vaccine platform has demonstrated great potential to be used either as a stand-alone or a boost vaccine in murine models. However, Ad TB vaccine remains to be evaluated in a more relevant and sensitive guinea pig model of pulmonary TB. Many vaccine candidates shown to be effective in murine models have subsequently failed to pass the test in guinea pig models.


RESULTS
Specific pathogen-free guinea pigs were immunized with BCG, AdAg85A intranasally (i.n), AdAg85A intramuscularly (i.m), BCG boosted with AdAg85A i.n, BCG boosted with AdAg85A i.m, or treated only with saline. The animals were then infected by a low-dose aerosol of M. tuberculosis (M.tb). At the specified times, the animals were sacrificed and the levels of infection in the lung and spleen were assessed. In separate studies, the long-term disease outcome of infected animals was monitored until the termination of this study. Immunization with Ad vaccine alone had minimal beneficial effects. Immunization with BCG alone and BCG prime-Ad vaccine boost regimens significantly reduced the level of M.tb infection in the tissues to a similar extent. However, while BCG alone prolonged the survival of infected guinea pigs, the majority of BCG-immunized animals succumbed by 53 weeks post-M.tb challenge. In contrast, intranasal or intramuscular Ad vaccine boosting of BCG-primed animals markedly improved the survival rate with 60% of BCG/Ad i.n- and 40% of BCG/Ad i.m-immunized guinea pigs still surviving by 74 weeks post-aerosol challenge.


CONCLUSIONS
Boosting, particularly via the intranasal mucosal route, with AdAg85A vaccine is able to significantly enhance the long-term survival of BCG-primed guinea pigs following pulmonary M.tb challenge. Our results thus support further evaluation of this viral-vectored TB vaccine in clinical trials.
Xing
Zhou
Z
Centre for Gene Therapeutics, MG DeGroote Institute for Infectious Disease Research, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada. xingz@mcmaster.ca
McFarland
Christine T
CT
Sallenave
Jean-Michel
JM
Izzo
Angelo
A
Wang
Jun
J
McMurray
David N
DN
D000256:Adenoviridae / Q000235:genetics*; D000281:Administration, Intranasal; D000818:Animals; D000942:Antigens, Bacterial / Q000378:metabolism; D001500:BCG Vaccine / Q000378:metabolism*; D004195:Disease Models, Animal; D005822:Genetic Vectors; D006168:Guinea Pigs; D007114:Immunization; D009169:Mycobacterium tuberculosis / Q000378:metabolism; D009297:Nasal Mucosa / Q000473:pathology; D013997:Time Factors; D032581:Tuberculosis Vaccines / Q000008:administration & dosage*; D014397:Tuberculosis, Pulmonary / Q000517:prevention & control*
D000942:Antigens, Bacterial; D001500:BCG Vaccine; D032581:Tuberculosis Vaccines