Protection and polyfunctional T cells induced by Ag85B-TB10.4/IC31 against Mycobacterium tuberculosis is highly dependent on the antigen dose.
BACKGROUND
Previously we have shown that Ag85B-TB10.4 is a highly efficient vaccine against tuberculosis when delivered in a Th1 inducing adjuvant based on cationic liposomes. Another Th1 inducing adjuvant, which has shown a very promising profile in both preclinical and clinical trials, is IC31. In this study, we examined the potential of Ag85B-TB10.4 delivered in the adjuvant IC31 for the ability to induce protection against infection with Mycobacterium tuberculosis. In addition, we examined if the antigen dose could influence the phenotype of the induced T cells.


RESULTS
We found that vaccination with the combination of Ag85B-TB10.4 and IC31 resulted in high numbers of polyfunctional CD4 T cells co-expressing IL-2, IFN-gamma and TNF-alpha. This correlated with protection against subsequent challenge with M.tb in the mouse TB model. Importantly, our results also showed that both the vaccine induced T cell response, and the protective efficacy, was highly dependent on the antigen dose. Thus, whereas antigen doses of 5 and 15 microg did not induce significant protection against M.tb, reducing the dose to 0.5 microg selectively increased the number of polyfunctional T cells and induced a strong protection against infection with M.tb. The influence of antigen dose was also observed in the guinea pig model of aerosol infection with M.tb. In this model a 2.5 fold increase in the antigen dose reduced the protection against infection with M.tb to the level observed in non-vaccinated animals.


CONCLUSIONS
Small changes in the antigen dose can greatly influence the induction of specific T cell subpopulations and the dose is therefore a crucial factor when testing new vaccines. However, the adjuvant IC31 can, with the optimal dose of Ag85B-TB10.4, induce strong protection against Mycobacterium tuberculosis. This vaccine has now entered clinical trials.
Aagaard
Claus
C
Department of Infectious Disease Immunology, Statens Serum Institute, Copenhagen, Denmark.
Hoang
Truc Thi Kim Thanh
TT
Izzo
Angelo
A
Billeskov
Rolf
R
Troudt
JoLynn
J
Arnett
Kim
K
Keyser
Andrew
A
Elvang
Tara
T
Andersen
Peter
P
Dietrich
Jes
J
D000217:Acyltransferases / Q000737:chemistry*; D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D015496:CD4-Positive T-Lymphocytes / Q000382:microbiology; D004338:Drug Combinations; D005260:Female; D006168:Guinea Pigs; D007371:Interferon-gamma / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009169:Mycobacterium tuberculosis / Q000502:physiology*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry*; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology*; D018417:Th1 Cells / Q000276:immunology; D014376:Tuberculosis / Q000382:microbiology / Q000517:prevention & control; D032581:Tuberculosis Vaccines / Q000737:chemistry
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D004338:Drug Combinations; C544002:IC31 adjuvant; D009838:Oligodeoxyribonucleotides; D009842:Oligopeptides; C501710:TB10.4 antigen, Mycobacterium tuberculosis; D032581:Tuberculosis Vaccines; D007371:Interferon-gamma; D000217:Acyltransferases; C121433:antigen 85B, Mycobacterium tuberculosis