Protection against Mycobacterium tuberculosis Infection Offered by a New Multistage Subunit Vaccine Correlates with Increased Number of IFN-γ+IL-2+ CD4+ and IFN-γ+ CD8+ T Cells

Abstract

Protein subunit vaccines present a compelling new area of research for control of tuberculosis (TB). Based on the interaction between Mycobacterium tuberculosis and its host, five stage-specific antigens of M. tuberculosis that participate in TB pathogenesis—Rv1813, Rv2660c, Ag85B, Rv2623, and HspX—were selected. These antigens were verified to be recognized by T cells from a total of 42 whole blood samples obtained from active TB patients, patients with latent TB infections (LTBIs), and healthy control donors. The multistage polyprotein A1D4 was developed using the selected five antigens as a potentially more effective novel subunit vaccine. The immunogenicity and protective efficacy of A1D4 emulsified in the adjuvant MTO [monophosphoryl lipid A (MPL), trehalose-6,6′-dibehenate (TDB), components of MF59] was compared with Bacillus Calmette-Guerin (BCG) in C57BL/6 mice. Our results demonstrated that A1D4/MTO could provide more significant protection against M. tuberculosis infection than the PBS control or MTO adjuvant alone judging from the A1D4-specific Th1-type immune response; however, its efficacy was inferior to BCG as demonstrated by the bacterial load in the lung and spleen, and by the pathological changes in the lung. Antigen-specific single IL-2-secreting cells and different combinations with IL-2-secreting CD4+ T cells were beneficial and correlated with BCG vaccine-induced protection against TB. Antigen-specific IFN-γ+IL-2+ CD4+ T cells were the only effective biomarker significantly induced by A1D4/MTO. Among all groups, A1D4/MTO immunization also conferred the highest number of antigen-specific single IFN-γ+ and IFN-γ+TNF-α+ CD4+ T cells, which might be related to the antigen load in vivo, and single IFN-γ+ CD8+ T cells by mimicking the immune patterns of LTBIs or curable TB patients. Our strategy seems promising for the development of a TB vaccine based on multistage antigens, and subunit antigen A1D4 suspended in MTO adjuvant warrants preclinical evaluation in animal models of latent infection and may boost BCG vaccination.

First-in-human trial of the post-exposure tuberculosis vaccine H56:IC31 in Mycobacterium tuberculosis infected and non-infected healthy adults

“…Some trial participants had pre-existing, low-level Rv2660c-specific responses, which did not markedly increase after H56:IC31 vaccination. This is consistent with reports of Rv2660c-specific T cell responses in persons with latent M.tb infection and/or TB disease [34] [22,35,36].…”

A New Adjuvant MTOM Mediates Mycobacterium tuberculosis Subunit Vaccine to Enhance Th1-Type T Cell Immune Responses and IL-2+ T Cells

“…As shown in Figure 4B, MTO elicited mainly single IFN-γ + and single TNF-α + CD4 + and CD8 + T cells, which is consistent with previous findings (18). Mv induced mainly single IL-2 + CD4 + T cells and single IFN-γ + CD8 + T cells.…”

“…Water-in-oil adjuvant, MTO, was prepared as described previously (18). Mv was cultivated in sterile medium (2.5 g/L yeast extract, 5 g/L tryptone, 1 g/L glucose) at 37°C.…”

Age predicts cytokine kinetics and innate immune cell activation following intranasal delivery of IFNγ and GM-CSF in a mouse model of RSV infection

“…Typically, production of these cytokines are mediated through TLR-ligation by pattern associated molecular patterns [56] and a growing number of studies report cytokine-eliciting adjuvants as promising vaccine strategies [10, 11, 13, 42]. To determine if immune activation was altered following direct delivery of IFNγ or GM-CSF during RSV infection in the infant lung, infant mice were infected with RSV and treated with intranasal IFNγ or GM-CSF as described in the methods section.…”