HBHA-Induced Polycytotoxic CD4+ T Lymphocytes Are Associated with the Control of Mycobacterium tuberculosis Infection in Humans

Abstract

Heparin-binding hemagglutinin (HBHA), a surface protein of Mycobacterium tuberculosis, is an attractive vaccine candidate and marker of protective immunity against tuberculosis, although the mechanisms underlying this protective immunity are not fully understood. Comparisons of the immune responses of latently M. tuberculosis-infected (LTBI) subjects to those of patients with active tuberculosis (aTB) may help to identify surrogate markers of protection, as LTBI subjects are most often lifelong protected against the disease. HBHA was shown to induce strong Th1 responses and cytotoxic CD8 + responses in LTBI subjects, but additional mechanisms of control of M. tuberculosis infection remain to be identified. In this study, using HBHA-induced blast formation as a readout of specific T lymphocyte activation, we report the presence in M. tuberculosis-infected subjects of HBHAinduced CD4 + T cell blasts that degranulate, as measured by surface capture of CD107a. This suggests the induction by HBHA of a CD4 + T cell subset with cytolytic function, and as nearly half of these cells also contained IFN-g, they had both Th1 and cytotoxic characteristics. We further identified a CD4 + T lymphocyte subset producing IFN-g together with a combination of mediators of cytotoxicity, i.e., perforin, granzymes, and granulysin, and we called them polycytotoxic CD4 + T lymphocytes. Interestingly, whereas purified protein derivative induced such cells in both LTBI subjects and patients with aTB, HBHA-specific polycytotoxic CD4 + T lymphocytes were detected in LTBI subjects and not in patients with pulmonary aTB. To our knowledge, we thus identified a new HBHA-induced CD4 + T cell subset that may contribute to the control of M. tuberculosis infection.

Identification of antigens presented by MHC for vaccines against tuberculosis

“…In this study we identified nested peptides presented by MHC-II, originating from Heparin-binding hemagglutinin, hbhA in M. bovis BCG, which is 199 amino acid long, and has 100% identity to Rv0475 of M.tb H37Rv and is an important virulence factor of M.tb . 39 This antigen is a well-known immunogen and vaccine candidate 40,41 that is able to induce multifunctional CD4 + T cells in HIV and non-HIV co-infected TB patients. 42 It induces a subset of CD4 + T cells with cytolytic functions, 41 and it is a known adhesin 43 that is involved in bacterial agglutination and has been implicated in the dissemination of M.tb .…”

“…39 This antigen is a well-known immunogen and vaccine candidate 40,41 that is able to induce multifunctional CD4 + T cells in HIV and non-HIV co-infected TB patients. 42 It induces a subset of CD4 + T cells with cytolytic functions, 41 and it is a known adhesin 43 that is involved in bacterial agglutination and has been implicated in the dissemination of M.tb . 44 It has been found in different intracellular locations, participates in the formation of lipid inclusions and can bind charged lipids specifically to 4,5-phosphatidylinositol diphosphate.…”

Mycobacterium tuberculosis Primary Infection and Dissemination: A Critical Role for Alveolar Epithelial Cells

“…Interestingly, while ESAT-6 is considered to be a promising vaccine component, the vaccine formulations, strategy, and evaluation has been designed to exploit its ability to elicit strong IFN-γ responses (van Dissel et al, 2010; Kwon et al, 2018). HBHA has been shown to induce a cytolytic CD4+ T cell subset in persons with LTBI but not active TB, suggesting a role for HBHA in the control of M. tb infection (Aerts et al, 2019), and both HBHA-induced IFN-γ responses and anti-HBHA IgA were found to be elevated in household contacts and community controls compared to untreated TB patients in TB-endemic Addis-Ababa, Ethiopia, suggesting HBHA can confer both protective cell-mediated and humoral immune responses (Belay et al, 2016). While the exact mechanisms of most vaccines are unknown, several successful vaccines have been designed to use the humoral immune response as their mode of protection, e.g., polio, tetanus, diphtheria and pertussis, hepatitis A, and MMRV vaccines.…”

Recombinant fusion protein of Heparin-Binding Hemagglutinin Adhesin and Fibronectin Attachment Protein (rHBHA-FAP) of Mycobacterium avium subsp. paratuberculosis elicits a strong gamma interferon response in peripheral blood mononuclear cell culture

“…The full length of FAP-P has been demonstrated to have the potential to induce cell-mediated immunity in vitro [24] and in vivo [43]. Some studies have demonstrated that methylated HBHA causes specific IFN-γ response in latent M. tuberculosis infection [20, 21] and the induction capability of both CD4 + and CD8 + lymphocytes in M. tuberculosis [22]. Then, it was predicted that our chimeric protein can induce cell-mediated immunity.…”

“…Some studies have demonstrated that methylated HBHA causes specific IFN-γ response in latent M. tuberculosis infection [20, 21]. Also, there is some reports about the induction by HBHA of both CD4 + and CD8 + T lymphocytes producing cytokines like IFN-γ in M. tuberculosis infection [22, 23]. The FN-binding glycoprotein family including fibronectin attachment proteins (FAPs) is important for attachment and internalization of MAP by epithelial cells and induce Th 1 polarization and IFN-γ production in vitro [24].…”