This study assessed the polyfunctional T cells in healthy household contacts (HHCs) and TB patients. This study also assessed the memory subsets responsible for the secretion of IFN-γ during the short-term culture with Mycobacterium tuberculosis antigens. Frequencies of CD4+IFN-γ+TNF-α+ T cells and CD8+IFN-γ+TNF-α+ T cells specific to M. tuberculosis antigens were significantly higher in TB patients compared to HHC. IFN-γ-secreting T cells, during overnight stimulation with M. tuberculosis antigens, belonged to effector memory subset with a CD45RA?CD27? phenotype. However, the number of IFN-γ-secreting effector memory cells did not differ between HHC and TB patients. 1. Introduction Tuberculosis (TB) is a global health problem with 2 billion people infected with the causative agent Mycobacterium tuberculosis (M. tuberculosis). Of these, only 10 percent will progress to active TB disease resulting in almost 2 million deaths per year [1]. This provides compelling evidence that the human immune system is capable of controlling the pathogen. However, the precise mechanisms contributing to the loss of immune control and progression of active TB disease are not known. A better understanding of these processes is critical for the development of improved diagnostics, treatment protocols, and vaccines. It has been long recognized that Interferon gamma (IFN-γ) producing T cells provide the major effector response in TB [2–5]. However, assessment of IFN-γ producing T cells alone may not be sufficient. Further analysis of various T cell memory subsets, such as central memory and effector memory subsets, may provide some light in understanding the T cell protection in TB. T cells are able to produce multiple factors simultaneously and they are termed polyfunctional T cells. The evidence from animal and human models of chronic viral infections indicates that high levels of chronic antigen stimulation lead to functional impairment of antigen-specific T cell responses, with reduced cytokine production, cytotoxicity, and proliferative capacity [6–11]. The capacity of antigen-specific T cells to produce multiple cytokines simultaneously has been associated with superior functional capacity [12] and has been correlated with control of human chronic viral infections such as human immunodeficiency virus (HIV) [13–15] and hepatitis C virus (HCV) [16]. Moreover, polyfunctional T cells have been associated with protection against disease progression in mouse models of Leishmania major [17] and M. tuberculosis [18]. Polyfunctional T cells, which produce IFN-γ, IL-2, and TNF-α,
L. Goldsack and J. R. Kirman, “Half-truths and selective memory: interferon gamma, CD4+ T cells and protective memory against tuberculosis,” Tuberculosis, vol. 87, no. 6, pp. 465–473, 2007.
[3]
J. L. Flynn, “Immunology of tuberculosis and implications in vaccine development,” Tuberculosis, vol. 84, no. 1-2, pp. 93–101, 2004.
[4]
E. van de Vosse, M. A. Hoeve, and T. H. M. Ottenhoff, “Human genetics of intracellular infectious diseases: molecular and cellular immunity against mycobacteria and salmonellae,” The Lancet Infectious Diseases, vol. 4, no. 12, pp. 739–749, 2004.
[5]
O. Filipe-Santos, J. Bustamante, A. Chapgier et al., “Inborn errors of IL-12/23- and IFN-gamma-mediated immunity: molecular, cellular, and clinical features,” Seminars in Immunology, vol. 18, pp. 347–361, 2006.
[6]
D. L. Barber, E. J. Wherry, D. Masopust et al., “Restoring function in exhausted CD8 T cells during chronic viral infection,” Nature, vol. 439, no. 7077, pp. 682–687, 2006.
[7]
S. D. Blackburn, H. Shin, W. N. Haining et al., “Coregulation of CD8+ T cell exhaustion by multiple inhibitory receptors during chronic viral infection,” Nature Immunology, vol. 10, no. 1, pp. 29–37, 2009.
[8]
C. L. Day, D. E. Kaufmann, P. Kiepiela et al., “PD-1 expression on HIV-specific T cells is associated with T-cell exhaustion and disease progression,” Nature, vol. 443, no. 7109, pp. 350–354, 2006.
[9]
R. B. Jones, L. C. Ndhlovu, J. D. Barbour et al., “Tim-3 expression defines a novel population of dysfunctional T cells with highly elevated frequencies in progressive HIV-1 infection,” Journal of Experimental Medicine, vol. 205, no. 12, pp. 2763–2779, 2008.
[10]
D. E. Kaufmann, D. G. Kavanagh, F. Pereyra et al., “Upregulation of CTLA-4 by HIV-specific CD4+ T cells correlates with disease progression and defines a reversible immune dysfunction,” Nature Immunology, vol. 8, no. 11, pp. 1246–1254, 2007.
[11]
S. Urbani, B. Amadei, D. Tola et al., “PD-1 expression in acute hepatitis C virus (HCV) infection is associated with HCV-specific CD8 exhaustion,” Journal of Virology, vol. 80, no. 22, pp. 11398–11403, 2006.
[12]
S. Kannanganat, C. Ibegbu, L. Chennareddi, H. L. Robinson, and R. R. Amara, “Multiple-cytokine-producing antiviral CD4 T cells are functionally superior to single-cytokine-producing cells,” Journal of Virology, vol. 81, no. 16, pp. 8468–8476, 2007.
[13]
G. Makedonas and M. R. Betts, “Living in a house of cards: Re-evaluating CD8+ T-cell immune correlates against HIV,” Immunological Reviews, vol. 239, no. 1, pp. 109–124, 2011.
[14]
S. Kannanganat, B. G. Kapogiannis, C. Ibegbu et al., “Human immunodeficiency virus type 1 controllers but not noncontrollers maintain CD4 T cells coexpressing three cytokines,” Journal of Virology, vol. 81, no. 21, pp. 12071–12076, 2007.
[15]
M. R. Betts, M. C. Nason, S. M. West et al., “HIV nonprogressors preferentially maintain highly functional HIV-specific CD8+ T cells,” Blood, vol. 107, no. 12, pp. 4781–4789, 2006.
[16]
D. Ciuffreda, D. Comte, M. Cavassini et al., “Polyfunctional HCV-specific T-cell responses are associated with effective control of HCV replication,” European Journal of Immunology, vol. 38, no. 10, pp. 2665–2677, 2008.
[17]
P. A. Darrah, D. T. Patel, P. M. De Luca et al., “Multifunctional TH1 cells define a correlate of vaccine-mediated protection against Leishmania major,” Nature Medicine, vol. 13, no. 7, pp. 843–850, 2007.
[18]
E. K. Forbes, C. Sander, E. O. Ronan et al., “Multifunctional, high-level cytokine-producing Th1 cells in the lung, but not spleen, correlate with protection against Mycobacterium tuberculosis aerosol challenge in mice,” Journal of Immunology, vol. 181, no. 7, pp. 4955–4964, 2008.
[19]
N. Caccamo, G. Guggino, S. A. Joosten et al., “Multifunctional CD4+ T cells correlate with active Mycobacterium tuberculosis infection,” European Journal of Immunology, vol. 40, no. 8, pp. 2211–2220, 2010.
[20]
C. L. Day, N. Mkhwanazi, S. Reddy et al., “Detection of polyfunctional Mycobacterium tuberculosis-specific T cells and association with viral load in HIV-1-infected persons,” Journal of Infectious Diseases, vol. 197, no. 7, pp. 990–999, 2008.
[21]
J. M. Young, I. M. O. Adetifa, M. O. C. Ota, and J. S. Sutherland, “Expanded polyfunctional T cell response to mycobacterial antigens in TB disease and contraction post-treatment,” PLoS ONE, vol. 5, no. 6, Article ID e11237, 2010.
[22]
K. A. Millington, J. A. Innes, S. Hackforth et al., “Dynamic relationship between IFN-γ and IL-2 profile of Mycobacterium tuberculosis-specific T cells and antigen load,” Journal of Immunology, vol. 178, no. 8, pp. 5217–5226, 2007.
[23]
M. Kumar, N. Meenakshi, J. C. Sundaramurthi, G. Kaur, N. K. Mehra, and A. Raja, “Immune response to Mycobacterium tuberculosis specific antigen ESAT-6 among south Indians,” Tuberculosis, vol. 90, no. 1, pp. 60–69, 2010.
[24]
M. Kumar, J. C. Sundaramurthi, N. K. Mehra, G. Kaur, and A. Raja, “Cellular immune response to Mycobacterium tuberculosis-specific antigen culture filtrate protein-10 in South India,” Medical Microbiology and Immunology, vol. 199, no. 1, pp. 11–25, 2010.
[25]
A. Harari, V. Rozot, F. B. Enders et al., “Dominant TNF-α+Mycobacterium tuberculosis-specific CD4+ T cell responses discriminate between latent infection and active disease,” Nature Medicine, vol. 17, no. 3, pp. 372–376, 2011.
[26]
A. J. Zajac, J. N. Blattman, K. Murali-Krishna et al., “Viral immune evasion due to persistence of activated T cells without effector function,” Journal of Experimental Medicine, vol. 188, no. 12, pp. 2205–2213, 1998.
[27]
M. Lucas, C. L. Day, J. R. Wyer et al., “Ex vivo phenotype and frequency of influenza virus-specific CD4 memory T cells,” Journal of Virology, vol. 78, no. 13, pp. 7284–7287, 2004.
[28]
J. P. Casazza, M. R. Betts, D. A. Price et al., “Acquisition of direct antiviral effector functions by CMV-specific CD4+ T lymphocytes with cellular maturation,” Journal of Experimental Medicine, vol. 203, no. 13, pp. 2865–2877, 2006.
[29]
S. C. Derrick, I. M. Yabe, A. Yang, and S. L. Morris, “Vaccine-induced anti-tuberculosis protective immunity in mice correlates with the magnitude and quality of multifunctional CD4 T cells,” Vaccine, vol. 29, no. 16, pp. 2902–2909, 2011.
[30]
P. Klenerman and A. Hill, “T cells and viral persistence: lessons from diverse infections,” Nature Immunology, vol. 6, no. 9, pp. 873–879, 2005.
[31]
A. Harari, S. Petitpierre, F. Vallelian, and G. Pantaleo, “Skewed representation of functionally distinct populations of virus-specific CD4 T cells in HIV-1-infected subjects with progressive disease: changes after antiretroviral therapy,” Blood, vol. 103, no. 3, pp. 966–972, 2004.
[32]
C. L. Day, D. A. Abrahams, L. Lerumo et al., “Functional capacity of Mycobacterium tuberculosis-specific T cell responses in humans is associated with mycobacterial load,” Journal of Immunology, vol. 187, no. 5, pp. 2222–2232, 2011.
[33]
U. Sester, M. Fousse, J. Dirks et al., “Whole-blood flow-cytometric analysis of antigen-specific CD4 T-cell cytokine profiles distinguishes active tuberculosis from non-active states,” PLoS ONE, vol. 6, no. 3, Article ID e17813, 2011.
[34]
D. Goletti, O. Butera, F. Bizzoni, R. Casetti, E. Giradi, and F. Poccia, “Region of difference 1 antigen-specific CD4+ memory T cells correlate with a favorable outcome of tuberculosis,” Journal of Infectious Diseases, vol. 194, no. 7, pp. 984–992, 2006.