Novel lipopeptides of ESAT-6 induce strong protective immunity against Mycobacterium tuberculosis: Routes of immunization and TLR agonists critically impact vaccine's efficacy.
Mycobacterium tuberculosis (Mtb), the bacterial cause of tuberculosis, is a leading infectious agent worldwide. The development of a new vaccine against Mtb is essential to control global spread of tuberculosis, since the current vaccine BCG is not very effective and antibiotic resistance is a serious, burgeoning problem. ESAT-6 is a secreted protein of Mtb, which is absent in BCG but has been implicated in inducing protective immunity against Mtb. Peptide based subunit vaccines are attractive due to their safety and high specificity in eliciting immune responses, but small synthetic peptides are usually not very immunogenic. We have designed a novel subunit vaccine for Mtb by using simple lipid (palmitic acid) modified derivatives of peptides from ESAT-6 protein corresponding to dominant human T cell epitopes and examined their ability to stimulate protective immunity against Mtb by intranasal and subcutaneous immunization in mice. We also investigated how individual TLR agonists as adjuvants (PolyI:C, MPL and GDQ) contribute to enhancing the induced immune responses and resulting protective efficacy of our vaccine. We observed that single C-terminal palmitoyl-lysine modified lipopeptides derived from ESAT-6 induce significant cellular immune responses on their own upon mucosal and subcutaneous immunizations. Intriguingly, a combination of immunogenic lipopeptides of ESAT-6 antigen exhibited local (pulmonary) and systemic immune responses along with efficient protective efficacy when administered intranasally or subcutaneously. Surprisingly, combination of ESAT-6 derived lipopeptides with a TLR-4 agonist (MPL) enhanced protection, whereas TLR-3 (Poly I:C) and TLR-7/8 agonists (gardiquimod, GDQ) led to reduced protection associated with specific local and systemic immune modulation. Our studies demonstrate the potential of ESAT-6 derived lipopeptides as a promising vaccine candidate against Mtb, and emphasize that selection of adjuvant is critical for the success of vaccines. These findings demonstrate the promise of synthetic lipopeptides as the basis of a subunit vaccine for TB.
Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
Nancy
N
Gupta
Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
Satish
S
Vedi
Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
Dennis Y
DY
Kunimoto
Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
Babita
B
Agrawal
Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada. Electronic address: rkumar@ualberta.ca.
Rakesh
R
Kumar
D000276:Adjuvants, Immunologic; D000281:Administration, Intranasal; D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry / Q000276:immunology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000276:immunology*; D016207:Cytokines / Q000096:biosynthesis; D018984:Epitopes, T-Lymphocyte / Q000737:chemistry; D007111:Immunity, Cellular; D007114:Immunization / Q000379:methods; D055666:Lipopeptides / Q000008:administration & dosage / Q000138:chemical synthesis / Q000737:chemistry* / Q000276:immunology; D054878:Lipoylation; D051379:Mice; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D019308:Palmitic Acid / Q000737:chemistry / Q000378:metabolism; D051193:Toll-Like Receptors / Q000819:agonists*; D014376:Tuberculosis / Q000517:prevention & control; D032581:Tuberculosis Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000737:chemistry / Q000276:immunology*; D022223:Vaccines, Subunit / Q000008:administration & dosage / Q000009:adverse effects / Q000737:chemistry / Q000276:immunology
D000276:Adjuvants, Immunologic; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D016207:Cytokines; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D018984:Epitopes, T-Lymphocyte; D055666:Lipopeptides; D051193:Toll-Like Receptors; D032581:Tuberculosis Vaccines; D022223:Vaccines, Subunit; D019308:Palmitic Acid
ESAT-6; Lipopeptides; Mycobacterium tuberculosis; Palmitoylation; Promiscuous epitopes; Route of immunization; TLR-agonist