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Bretscher PA. On the mechanism determining the TH1/TH2 phenotype of an immune response, and its pertinence to strategies for the prevention, and treatment, of certain infectious diseases. Scand J Immunol 2014; 79:361-76. [PMID: 24684592 PMCID: PMC4282429 DOI: 10.1111/sji.12175] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 03/27/2014] [Indexed: 12/31/2022]
Abstract
It is well recognized that the physiological/pathological consequences of an immune response, against a foreign or a self-antigen, are often critically dependent on the class of immunity generated. Here we focus on how antigen interacts with the cells of the immune system to determine whether antigen predominantly generates Th1 or Th2 cells. We refer to this mechanism as the 'decision criterion' controlling the Th1/Th2 phenotype of the immune response. A plausible decision criterion should account for the variables of immunization known to affect the Th1/Th2 phenotype of the ensuing immune response. Documented variables include the nature of the antigen, in terms of its degree of foreignness, the dose of antigen and the time after immunization at which the Th1/Th2 phenotype of the immune response is assessed. These are quantitative variables made at the level of the system. In addition, the route of immunization is also critical. I describe a quantitative hypothesis as to the nature of the decision criterion, referred to as the Threshold Hypothesis. This hypothesis accounts for the quantitative variables of immunization known to affect the Th1/Th2 phenotype of the immune response generated. I suggest and illustrate how this is not true of competing, contemporary hypotheses. I outline studies testing predictions of the hypothesis and illustrate its potential utility in designing strategies to prevent or treat medical situations where a predominant Th1 response is required to contain an infection, such as those caused by HIV-1 and by Mycobacterium tuberculosis, or to contain cancers.
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Affiliation(s)
- P A Bretscher
- University of SaskatchewanSaskatoon, Saskatchewan, Canada
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Hamilton D, Ismail N, Kroeger D, Rudulier C, Bretscher P. Macroimmunology and immunotherapy of cancer. Immunotherapy 2011; 1:367-83. [PMID: 20635957 DOI: 10.2217/imt.09.6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cytotoxic T lymphocytes (CTLs), associated with Th1 responses, are the most important mediators of resistance against most tumors. We argue that most murine tumors grow progressively when a significant Th2 component to their immune response develops, which is associated with the downregulation of the CTL response. We outline recent evidence that strongly supports this Th2-skewing hypothesis as the prevalent mechanism of tumor escape in murine systems. We describe the conceptual grounds and evidence for the 'threshold hypothesis' that proposes how the Th1/Th2 phenotype of an immune response generated against 'nonliving' antigens is determined. We suggest that this threshold hypothesis also accurately describes how the Th1/Th2 phenotype of murine antitumor immune responses is determined, as this hypothesis can account for the critical and known features of these immune responses. The efficacy of several manipulations that prevent or arrest progressive tumor growth in murine models, through their effects on the antitumor immune response, can be understood within the context of the threshold hypothesis. Indirect evidence supports the view that similar relationships between cancers and the immune system are present in humans. We propose means by which these insights can be employed to optimize the harnessing of protective Th1 CTL immunity against tumors.
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Affiliation(s)
- Duane Hamilton
- Department of Microbiology & Immunology, University of Saskatchewan, 107 Wiggins Road, Saskatoon, Saskatchewan, Canada
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Kiros TG, Power CA, Wei G, Bretscher PA. Immunization of newborn and adult mice with low numbers of BCG leads to Th1 responses, Th1 imprints and enhanced protection upon BCG challenge. Immunotherapy 2010; 2:25-35. [DOI: 10.2217/imt.09.80] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Neonatal bacille Calmette–Guerin (BCG) vaccination is widely employed to protect against tuberculosis. Predominant Th1 but not mixed Th1/Th2 responses are thought to be protective. If so, effective vaccination must cause Th1 imprints. The immune system of infants differs from that of adults and such differences could critically affect neonatal vaccination. We demonstrate that BCG infection of infant and adult mice produces similar responses. Infection with low and high numbers of BCG, respectively, leads to sustained Th1 and mixed Th1/Th2 responses. Low-dose but not high-dose infection also results in Th1 imprints, guaranteeing a Th1 response upon high-dose challenge, and resulting in optimal bacterial clearance. Our observations on low-dose Th1 imprinting are intriguing in the context of the well-known madras trial. In this trial, the highest dose of BCG, which had insignificant side effects, was administered to over 250,000 human subjects. This high-dose vaccination resulted in insignificant protection against tuberculosis.
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Affiliation(s)
- Tadele G Kiros
- Vaccine & Infectious Diseases Organization, University of Saskatchewan, Canada
| | | | - Guojian Wei
- Western College of Veterinary Medicine, Canada
| | - Peter A Bretscher
- Department of Microbiology & Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E5, Canada
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Khare S, Hondalus MK, Nunes J, Bloom BR, Garry Adams L. Mycobacterium bovis DeltaleuD auxotroph-induced protective immunity against tissue colonization, burden and distribution in cattle intranasally challenged with Mycobacterium bovis Ravenel S. Vaccine 2006; 25:1743-55. [PMID: 17240005 DOI: 10.1016/j.vaccine.2006.11.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2006] [Revised: 11/04/2006] [Accepted: 11/13/2006] [Indexed: 11/29/2022]
Abstract
Bovine tuberculosis is a chronic granulomatous disease caused by Mycobacterium bovis. Lack of definitive diagnostics and effective vaccines for domestic animals are major obstacles to the control and eradication of bovine tuberculosis. Auxotrophic mutants of Mycobacterium tuberculosis have shown promise as vaccine candidates for preventing human tuberculosis. Similarly, we constructed a leucine auxotroph of M. bovis, by using allelic exchange to delete leuD (encoding isopropyl malate isomerase), creating a strain requiring exogenous leucine for growth in vitro. We vaccinated 10 cattle subcutaneously with 10(9)CFU of M. bovis DeltaleuD and 10 age-matched, gender-matched controls were injected with phosphate-buffered saline. Vaccinated cattle had significantly increased in vitro antigen-specific T-cell-mediated responses. All cattle were challenged intranasally on day 160 post-immunization with 10(6)CFU of virulent M. bovis Ravenel S. On day 160 post-challenge vaccinated cattle had significantly reduced tissue mycobacterial burdens and 6 of 10 had complete clearance of the challenge strain and histopathological lesions were dramatically less severe in the vaccinated group. Thus, a single subcutaneous immunization of the M. bovis DeltaleuD mutant produced highly significantly protective immunity as measured by a reduction in tissue colonization, burden, bacilli dissemination, and histopathology caused by virulent M. bovis Ravenel S challenge.
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Affiliation(s)
- Sangeeta Khare
- Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA
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Fattorini L, Nisini R, Fan Y, Li YJ, Tan D, Mariotti S, Teloni R, Iona E, Orefici G. Exposure of BALB/c mice to low doses of Mycobacterium avium increases resistance to a subsequent high-dose infection. MICROBIOLOGY (READING, ENGLAND) 2002; 148:3173-3181. [PMID: 12368451 DOI: 10.1099/00221287-148-10-3173] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BALB/c mice exposed intranasally (i.n.), intradermally (i.d.) or intraperitoneally (i.p.) to low doses of Mycobacterium avium (20 c.f.u. at three different times two weeks apart) showed an increased resistance to a subsequent high-dose (10(5) c.f.u.) infection. I.n.-exposed mice had few mycobacteria in the tissues (>100 c.f.u.) and showed an expansion of CD4(+) T cells associated with overproduction of IL-12 and IFN-gamma, but not IL-4 and IgG antibodies. Parenterally (i.p. and i.d.) exposed animals showed c.f.u. numbers higher than i.n.-exposed mice, together with overproduction of IL-12, IFN-gamma and IL-4 in the case of i.p.-exposed mice, and of IL-12, IFN-gamma and IgG2a and IgG1 antibodies in the case of i.d.-exposed mice. Low-dose exposures were not contained by athymic BALB/c nude mice; however, naive nude mice reconstituted with i.n.-primed CD4(+) T cells of BALB/c mice were protected against high-dose infection, indicating that CD4(+) T cells are essential to control even low-dose infections by M. avium. Overall, these data suggest that continuous i.n. exposure to M. avium doses commonly found in the environment may play a role in determining the natural resistance of normal hosts against this organism.
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Affiliation(s)
- Lanfranco Fattorini
- Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy1
| | - Roberto Nisini
- Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy1
| | - Yuming Fan
- Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy1
| | - Yong-Jun Li
- Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy1
| | - Dejiang Tan
- Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy1
| | - Sabrina Mariotti
- Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy1
| | - Raffaela Teloni
- Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy1
| | - Elisabetta Iona
- Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy1
| | - Graziella Orefici
- Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy1
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