Antigen-specific antibody and polyfunctional T cells generated by respiratory immunization with protective Burkholderia ΔtonB Δhcp1 live attenuated vaccines

Abstract

Melioidosis, caused by Burkholderia pseudomallei (Bpm), lacks a vaccine. We identify the immune correlates of protection induced by B. mallei ΔtonB Δhcp1 (CLH001) and Bpm ΔtonB Δhcp1 (PBK001) vaccines against inhalational melioidosis. Mucosal immunization with either vaccine generates Bpm-specific IgM and IgG (IgG2b/c > IgG1 > IgG3) antibodies in sera and lungs, and lung IgA antibodies. Sera confers complement-independent bactericidal activity and macrophages opsonophagocytic uptake but is insufficient in passive transfer experiments to provide significant protection. Both vaccines elicit memory Th1 and Th17 CD4+ T-cell responses in lung and spleen after Bpm antigen-specific recall. The PBK001 vaccine is superior in generating respiratory IgA post-boost, anamnestic IgG at challenge, T-cell recall to specific antigen, and development of diverse polyfunctional memory T-cell pools. Analysis of lung histology suggests that potent polyfunctional T-cell memory and/or IL-17 signatures generated with PBK001 vaccination may be associated with moderate lung inflammation post vaccination.

Self-adjuvanting nanovaccines boost lung-resident CD4+ T cell immune responses in BCG-primed mice

“…Splenocytes from the same samples were collected after antigen recall and processed for intracellular staining to characterize groups of cytokine-producing T cells 29 , including polyfunctional CD4 + T cells using combinatorial Boolean analysis. The number of cells in lung tissue were too few for flow cytometric analysis of both memory subpopulations and intracellular cytokine recall; however, spleen provided sufficient cells numbers (Supplemental Figs.…”

BpOmpW Antigen Stimulates the Necessary Protective T-Cell Responses Against Melioidosis

“…The continued emergence of this pathogen throughout tropical and subtropical regions ( 29 ), together with the global increase of T2D ( 30 ), is a cause of major concern in these areas and has accelerated the search for new remedies to combat this disease ( 31 ). Although the protective immune response against B. pseudomallei is not fully understood, it is widely acknowledged that, due to the intracellular nature of B. pseudomallei , an effective vaccine should induce both T-cell and B-cell responses ( 32 ). Therefore, the elucidation of the protective cell-mediated immune responses of the BpOmpW antigen in preclinical studies is essential to advance the development of an efficacious human T-cell-inducing vaccine against melioidosis.…”

Recent Progress in Shigella and Burkholderia pseudomallei Vaccines

“…Intranasal vaccination with Bpm ∆tonB ∆hcp1 conferred 100% protection against aerosolized Bpm infection in the C57BL/6 mice model of melioidosis, and bacterial clearance in lungs and other target organs was indicative of sterilizing immunity [107]. A recent study illustrated the protective capacity of this vaccine, which generated Bpmspecific serum IgM, IgG, and lung IgA and developed diverse polyfunctional memory T cell pools as well as Th1 and Th17 CD4 + T cell responses in the lungs and spleens of vaccinated mice [109].…”

“…These should be critical concerns during development of the next generation of vaccines. Therefore, double gene mutation strategies were used to create Bpm LAVs strains [106][107][108][109]. The double deletion mutant of genes encoding (p)ppGpp-synthesis enzyme (∆relA ∆spoT) in Bpm K96243 provided significant protection for immunized C57BL/6 mice of 100% up to 30 days post-challenge, and the 60% survivor mice remained until day 55, but sterile immunity was not accomplished [106].…”

“…The Bm and Bpm ∆tonB ∆hcp1 double deletion mutant strains were constructed by deleting genes encoding a protein involved in the uptake of iron, tonB, and a gene encoding for a protein that is a component of type 6 secretory system cluster 1 (T6SS-1), hcp1 [107,110]. Bpm ∆tonB ∆hcp1 was revealed as the safest and the most efficient LAV strain developed to date because it provides comprehensive evidence of immune responses correlated to protection [107,109]. Intranasal vaccination with Bpm ∆tonB ∆hcp1 conferred 100% protection against aerosolized Bpm infection in the C57BL/6 mice model of melioidosis, and bacterial clearance in lungs and other target organs was indicative of sterilizing immunity [107].…”