Combined Use of Mycobacterium tuberculosis-Specific CD4 and CD8 T-Cell Responses Is a Powerful Diagnostic Tool of Active Tuberculosis

Immune-based assays are promising tools to help to formulate diagnosis of active tuberculosis. A multiparameter flow cytometry assay assessing T-cell responses specific to Mycobacterium tuberculosis and the combination of both CD4 and CD8 T-cell responses accurately discriminated between active tuberculosis and latent infectio

A quantitative analysis of complexity of human pathogen-specific CD4 T cell responses in healthy M. tuberculosis infected South Africans

Author Summary: Human pathogen-specific immune responses are tremendously complex and the techniques to study them ever expanding. There is an urgent need for a quantitative analysis and better understanding of pathogen-specific immune responses. Mycobacterium tuberculosis (Mtb) is one of the leading causes of mortality due to an infectious agent worldwide. Here, we were able to quantify the Mtb-specific response in healthy individuals with Mtb infection from South Africa. The response is highly diverse and 66 epitopes are required to capture 80% of the total reactivity. Our study also show that the majority of the identified epitopes are restricted by multiple HLA alleles. Thus, technical advances are required to capture and characterize the complete pathogen-specific response. This study demonstrates further that the approach combining identified epitopes into "megapools" allows capturing a large fraction of the total reactivity. This suggests that this technique is generally applicable to the characterization of immunity to other complex pathogens. Together, our data provide for the first time a quantitative analysis of the complex pathogen-specific T cell response and provide a new understanding of human infections in a natural infection setting

Meeting report: 6th Global Forum on Tuberculosis Vaccines, 22–25 February 2022, Toulouse, France

Safe, effective, and accessible vaccines are urgently needed to end tuberculosis (TB) by 2030. The 6th Global Forum on TB Vaccines, convened virtually 22–25 February 2022, was hosted by Toulouse, France, under the high patronage of President Emmanuel Macron, and the patronages of Minister for Solidarity and Health, Olivier Véran, and Minister for Higher Education, Research and Innovation, Frédérique Vidal. The theme for the meeting, “New horizons for TB vaccines”, reflected the changing landscape in which TB vaccine research and development (R&D) is being conducted: TB vaccines advancing into late-stage clinical trials and toward licensure, innovative research toward diversifying the TB vaccine pipeline and developing the next generation of candidates, increasing political, civil society, and community support for TB vaccines, and the ongoing COVID-19 pandemic. In this report, we summarize key themes and findings from the meeting, highlighting progress and gaps in the TB vaccine field

Proliferation Capacity and Cytotoxic Activity Are Mediated by Functionally and Phenotypically Distinct Virus-Specific CD8 T Cells Defined by Interleukin-7Rα (CD127) and Perforin Expression▿ †

Cytotoxicity and proliferation capacity are key functions of antiviral CD8 T cells. In the present study, we investigated a series of markers to define these functions in virus-specific CD8 T cells. We provide evidence that there is a lack of coexpression of perforin and CD127 in human CD8 T cells. CD127 expression on virus-specific CD8 T cells correlated positively with proliferation capacity and negatively with perforin expression and cytotoxicity. Influenza virus-, cytomegalovirus-, and Epstein-Barr virus/human immunodeficiency virus type 1-specific CD8 T cells were predominantly composed of CD127+ perforin−/CD127− perforin+, and CD127−/perforin− CD8 T cells, respectively. CD127−/perforin− and CD127−/perforin+ cells expressed significantly more PD-1 and CD57, respectively. Consistently, intracellular cytokine (gamma interferon, tumor necrosis factor alpha, and interleukin-2 [IL-2]) responses combined to perforin detection confirmed that virus-specific CD8 T cells were mostly composed of either perforin+/IL-2− or perforin−/IL-2+ cells. In addition, perforin expression and IL-2 secretion were negatively correlated in virus-specific CD8 T cells (P < 0.01). As previously shown for perforin, changes in antigen exposure modulated also CD127 expression. Based on the above results, proliferating (CD127+/IL-2-secreting) and cytotoxic (perforin+) CD8 T cells were contained within phenotypically distinct T-cell populations at different stages of activation or differentiation and showed different levels of exhaustion and senescence. Furthermore, the composition of proliferating and cytotoxic CD8 T cells for a given antiviral CD8 T-cell population appeared to be influenced by antigen exposure. These results advance our understanding of the relationship between cytotoxicity, proliferation capacity, the levels of senescence and exhaustion, and antigen exposure of antiviral memory CD8 T cells

H4:IC31 and BCG induced immune responses in a prevention of M. tuberculosis infection efficacy trial

Immunogenicity responses from the C040-404 clinical trial were measured by whole blood intracellular cytokine staining at baseline and 70 days after vaccination with H4:IC31 (subunit vaccine containing Ag85B and TB10.4), Bacille Calmette-Guerin (BCG, a live attenuated vaccine) or placebo (n=~30 per group) using flow cytometry.</div

A comparison of antigen-specific T cell responses induced by six novel tuberculosis vaccine candidates.

Eradication of tuberculosis (TB), the world's leading cause of death due to infectious disease, requires a highly efficacious TB vaccine. Many TB vaccine candidates are in pre-clinical and clinical development but only a few can be advanced to large-scale efficacy trials due to limited global resources. We aimed to perform a statistically rigorous comparison of the antigen-specific T cell responses induced by six novel TB vaccine candidates and the only licensed TB vaccine, Bacillus Calmette-Guérin (BCG). We propose that the antigen-specific immune response induced by such vaccines provides an objective, data-driven basis for prioritisation of vaccine candidates for efficacy testing. We analyzed frequencies of antigen-specific CD4 and CD8 T cells expressing IFNγ, IL-2, TNF and/or IL-17 from adolescents or adults, with or without Mycobacterium tuberculosis (M.tb) infection, who received MVA85A, AERAS-402, H1:IC31, H56:IC31, M72/AS01E, ID93+GLA-SE or BCG. Two key response characteristics were analyzed, namely response magnitude and cytokine co-expression profile of the memory T cell response that persisted above the pre-vaccination response to the final study visit in each trial. All vaccines preferentially induced antigen-specific CD4 T cell responses expressing Th1 cytokines; levels of IL-17-expressing cells were low or not detected. In M.tb-uninfected and -infected individuals, M72/AS01E induced higher memory Th1 cytokine-expressing CD4 T cell responses than other novel vaccine candidates. Cytokine co-expression profiles of memory CD4 T cells induced by different novel vaccine candidates were alike. Our study suggests that the T cell response feature which most differentiated between the TB vaccine candidates was response magnitude, whilst functional profiles suggested a lack of response diversity. Since M72/AS01E induced the highest memory CD4 T cell response it demonstrated the best vaccine take. In the absence of immunological correlates of protection, the likelihood of finding a protective vaccine by empirical testing of candidates may be increased by the addition of candidates that induce distinct immune characteristics

PLOS Pathogens publication: A comparison of antigen-specific T cell responses induced by six novel tuberculosis vaccine candidates.

Tuberculosis (TB) causes more deaths than any other single infectious disease, and a new, improved vaccine is needed to control the epidemic. Many new TB vaccine candidates are in clinical development, but only one or two can be advanced to expensive efficacy trials. In this study, we compared magnitude and functional attributes of memory T cell responses induced in recently conducted clinical trials by six TB vaccine candidates, as well as BCG. The results suggest that these vaccines induced CD4 and CD8 T cellresponses with similar functional attributes, but that one vaccine, M72/AS01 E , induced the largest responses. This finding may indicate a lack of diversity in T cell responses induced by different TB vaccine candidates. A repertoire of vaccine candidates that induces more diverse immune response characteristics may increase the chances of finding a protective vaccine against TB.</div

Vaccines

The dataset (Vaccines) contains background subtracted frequencies of CD4 and CD8 T cells producing a combination of IFNγ, IL-2, TNF and IL-17 in response to stimulation by vaccine-specific antigens for the vaccines included in the paper "A head-to-head comparison of specific T cell responses induced by six novel tuberculosis vaccine candidates". See paper for details. See Column names - Vaccines.docx for meanings of column names in the dataset (Vaccines)

A comparison of antigen-specific T cell responses induced by six novel tuberculosis vaccine candidates (BioRxiv preprint)

Pre-print submitted to BioRxiv.Abstract: Eradication of tuberculosis (TB), the world's leading cause of death due to infectious disease, requires a highly efficacious TB vaccine. Many TB vaccine candidates are in pre-clinical and clinical development but only a few can be advanced to large - scale efficacy trials due to limited global resources. We aimed to perform a statistically rigorous comparison of the antigen - specific T cell responses induced by six novel TB vaccine candidates and the only licensed TB vaccine, Bacillus Calmette - Guérin (BCG). We propose that the antigen - specific immune response induced by such vaccines provides an objective, data - driven basis for prioritisation of vaccine candidates for efficacy testing. We analyze d frequencies of antigen - specific CD4 and CD8 T cells expressing IFN γ, IL - 2, TNF and/or IL - 17 from adolescents or adults, with or without Mycobacterium tuberculosis ( M.tb ) infection, who received MVA85A, A ERAS - 402, H1:IC31, H56:IC31, M72/AS01 E, ID93 + GLA - SE or BCG. Two key response characteristics were analyzed, namely response magnitude and cytokine co - expression profile of the memory T cell response that persisted above the pre-vaccination response to the final study visit in each trial. All vaccines preferentially induced antigen - specific CD4 T cell responses expressing Th1 cytokines; levels of IL - 17 - expressing cells were low or not detected. In M.tb - uninfected and - infected individuals, M72/AS01 E induced higher memory Th1 cytokine - expressing CD4 T cell response s than other novel vaccine candidates. Cytokine co - expression profile s of memory CD4 T cells induced by different novel vaccine candidates were alike. Our study suggests that the T cell response feature which most differentiated between the TB vaccine candidates was response magnitude, whilst functional profiles suggested a lack of response diversity. Since M72/AS01 E induced the highest memory CD4 T cell response it demonstrated the best vaccine take. In the absence of immunological correlates of protection the likelihood of finding a protective vaccine by empirical testing of candidates may be increased by the addition of candidates that induce distinct immune characteristics. <br

Megapool

This dataset (Megapool) contains background subtracted frequencies of CD4 and CD8 T cells producing a combination of IFNγ, IL-2 and TNF in response to stimulation by Megapool for Mtb-infected but healthy individuals (Lindestam Arlehamn, 2016). See referenced paper for details. See Column names - Megapool.docx for meanings of column names in Megapool.xlsx.<br