Elsevier

Tuberculosis

Volume 85, Issues 5–6, September–November 2005, Pages 277-293
Tuberculosis

Animal models of tuberculosis

https://doi.org/10.1016/j.tube.2005.08.008Get rights and content

Summary

It was Robert Koch who recognized the spectrum of pathology of tuberculosis (TB) in different animal species. The examination of clinical specimens from infected humans and animals confirmed the variable patterns of pathological reactions in different species. Guinea pigs are innately susceptible while humans, mice and rabbits show different level of resistance depending upon their genotype. The studies of TB in laboratory animals such as mice, rabbits and guinea pigs have significantly increased our understanding of the aetiology, virulence and pathogenesis of the disease. The introduction of less than five virulent organisms into guinea pigs by the respiratory route can produce lung lesions, bacteraemia and fatal diseases, which helped the extrapolation of results of such experiments to humans. The similarities in the course of clinical infection between guinea pigs and humans allow us to model different forms of TB and to evaluate the protective efficacy of candidate vaccines in such systems. The only limitation of this model, however, is a dearth of immunological reagents that are required for the qualitative and quantitative evaluation of the immune responses, with special reference to cytokines and cell phenotypes. Another limitation is the higher cost of guinea pigs compared with mice. The rabbit is relatively resistant to Mycobacterium tuberculosis, however following infection with virulent Mycobacterium bovis, the rabbit produces pulmonary cavities like humans. The rabbit model, however, is also limited by the lack of the immunological reagents. Mice are the animal of choice for studying the immunology of mycobacterial infections and have contributed much to our current understanding of the roles of various immunological mechanisms of resistance. The resistance of mice to the development of classic TB disease, however, represents a significant disadvantage of the mouse model. Although non-human primates are closely related to humans, owing to high cost and handing difficulties they have not been exploited to a large extent. As all existing animal models fail to mimic the human disease perfectly, efforts should be focused on the development of the non-human primate(s) as the alternative animal model for TB.

Introduction

Tuberculosis (TB) caused by Mycobacterium tuberculosis is the leading bacterial cause of death. TB remains a global threat to public health, with approximately 2 million people dying from M. tuberculosis infections every year and one-third of the world's population latently infected with M. tuberculosis. Every year, 8 million individuals develop active disease.1 In India, TB remains one of the most pressing health problems, accounting for 30% of the global cases.2 It has been estimated in India that every year 2 million people develop TB and nearly 25% of them succumb to the disease, accounting for more than 1000 deaths every day. A vaccine against TB was developed about 80 years ago; various drugs for the control of the disease were developed about 40–50 years ago and combination chemotherapy has been in place for about 2 decades. Yet today we do not seem to be any closer to eliminating TB than we were a century ago.

Complete eradication of TB requires a vaccine that is cost effective and can be used for mass immunization. BCG (live attenuated Mycobacterium bovis BCG), the only TB vaccine presently being used, has succeeded only in some countries but has shown very limited usefulness in countries like India. It is the most widely used of all the vaccines in the WHO Expanded Programme for immunization,3 but has been estimated to prevent only 5% of all potentially vaccine-preventable deaths due to TB.4 It has been found to be protective against disseminated and meningeal TB in young children.5 The protective efficacy of BCG vaccine against adult pulmonary TB has varied widely in different geographical areas and different populations.6 Thus, a TB vaccine that protects consistently against adult TB in all populations is needed. Emergence of drug resistance has also led to renewed interest in development of alternate drug formulations. To study alternate modes of treatment and new vaccines and to better understand the host–parasite relationship, animal models are necessary. In the present article, we discuss the different animal models currently available for TB, and propose improvements of the existing models.

Section snippets

Mouse model

Robert Koch, who discovered the tubercle bacillus, first used the mouse as an experimental model. He showed that inoculation with M. tuberculosis induced lesions like those seen in the natural disease in humans.7 Subsequently, investigators established infection in a variety of animals (rabbits, guinea pigs, rats and mice) with pure cultures of M. tuberculosis. Due to interest in progressive pulmonary infection, these studies tended to involve guinea pigs and rabbits because of their higher

TB in immunodeficient mouse models

Because immunity to TB is T-cell mediated, the nude mouse and severe combined immunodeficiency (SCID) mouse that cannot produce T-cells are of interest as models in TB. The nude mouse is furless and suffers from thymic aplasia. These mice cannot produce functional T-cells, therefore they have substantially less resistance to TB and other mycobacterial infections. On the other hand, SCID mice lack both T- and B-cells owing to a defect in the variable region gene recombination61 and lack

Gene-disrupted and transgenic mice

A new model of TB using targeted gene disruption was developed by Dalton et al.64 In this model, the IFN-γ gene was specifically disrupted by the insertion of a neomycin resistance gene after the second exon. Mice in which the IFN-γ gene has been disrupted (IFN-γ−/−) are unable to control a normally sublethal dose of M. tuberculosis, delivered either by intravenous or aerosol route.

These IFN-γ KO mice have been shown to be extremely susceptible to M. tuberculosis, and a progressive and

Immunosenescent mice

Another form of immunodeficiency is the decline in immunological response with age. It was observed that young mice infected intravenously with a sub-lethal dose (105) of M. tuberculosis bacilli could contain and control infection but that the same dose was fatal in mice of 24–28 months age.79 Initially, it was thought that this mortality was due to lack of protective T-cells in old animals, however Orme80 showed that T-cells that are capable of recognizing mycobacterial antigens in old animals

Immunology of TB in the mouse model

It has become clear from the research of the last few years that all three subsets of T-cells, namely CD4, CD8 and γδ T-cells, play a crucial role in the acquired cellular immune response to experimental M. tuberculosis infection in the mouse.20 The use of gene-disrupted mice70, 81 confirmed the role of CD4+ T-cells in the murine model. The main role that the CD4+ T-cell population plays in the combat against the pathogen is secretion of the cytokine IFN-γ. Other cytokines that activate

Modelling persistence and reactivation in the mouse

Little is known about the basic mechanism involved in maintaining a latent M. tuberculosis infection or the causes of reactivation. In large part, this is due to the difficulty in developing and manipulating an animal model of latent TB. The design of an adequate animal model of latent M. tuberculosis infection is hampered by lack of knowledge about the biological characteristics of both the tubercle bacilli and host immunity during human latent TB. Two murine models of latent M. tuberculosis

Guinea pig model of TB

In the 1800s and 1900s, the guinea pig was the most widely used experimental animal for infectious disease studies. The classic experiments that established a microorganism as the aetiological agent of TB were carried out with guinea pigs infected with M. tuberculosis.92 Koch's principle reason for choosing this species for studies of M. tuberculosis in those days is still valid today—the susceptibility of this species to infection with human tubercle bacilli.93

Sisk94 outlined a number of

Modelling other clinical forms of TB

Besides primary pulmonary TB, the guinea pig model may be useful for other forms of the disease such as tuberculous pleuritis, exogenous re-infection and endogenous reactivation. Pleuritis can be induced in previously immunized guinea pigs by the intrapleural injection of either living BCG148 or heat-killed M. tuberculosis.149 Phalen and McMurray150 reported enhanced TNF-α levels in effusion fluid as well as in supernatant fluids from pleural fusion lymphocytes stimulated with PPD. Exogenous

Studies of cytokines and chemokines in guinea pigs

Several guinea pig cytokine and chemokine genes have been cloned in recent years.156, 157, 158, 159 Using Northern blot and real-time RT-PCR methodologies, it was demonstrated that splenocytes from BCG-vaccinated guinea pigs stimulated with whole mycobacteria or purified antigens responded with higher levels of IFN-γ mRNA.160 BCG vaccination augmented TNF-α protein production in splenocytes, resident peritoneal cells, and bronchoalveolar lavage cells following exposure to virulent and

Rabbit model of TB

In rabbits, TB is a disease in which lung tissue is destroyed, largely as a result of the host's own reaction to bacillary antigens. The most extensive studies on TB using the rabbit as an experimental model were made by Lurie170, 171, 172 and Lurie and Dannenberg.173 Inbred lines of rabbit were developed for resistance and susceptibility to TB. Resistant rabbits developed cavitary TB like adult immunocompetent humans when infected with the virulent Ravenel strain of M. bovis. The susceptible

TB in monkeys

There are a number of reports that suggest that rhesus monkeys (Macaca mulatta) are highly susceptible to virulent M. tuberculosis and virulent M. bovis.194, 195, 196, 197 The disease in monkeys is usually a rapidly progressive pulmonary disease with both haematogenous and bronchial spread of the bacilli. There are reports that suggest extensive caseous necrosis along with liquefaction of the caseous material with cavity formation.194, 195, 198, 199 The walls of the cavities harbour numerous

Conclusions

Non-human primates (monkeys) appear to have significant advantages over conventional laboratory animals in terms of modelling pulmonary TB for the purpose of vaccine evaluation201 as they are closely related to humans, are quite susceptible to infection by the aerosol route, develop human-like disease, exhibit antigen-induced T-lymphocyte activity both in vivo and in vitro, and can be protected quite effectively by BCG. In addition, major advances in availability of immunologic and other

Acknowledgements

I thank Dr. David N. McMurray, Department of Medical Microbiology and Immunology, Texas A & M University System Health Science Center, 407 Reynolds Medical Building, College Station, TX 77843-1114, USA for critical reading of the manuscript.

References (203)

  • J.E. Moss et al.

    The regulation of apoptosis by microbial pathogens

    Int Rev Cytol

    (1999)
  • R.J. North

    Importance of thymus-derived lymphocytes in cell-mediated immunity to infection

    Cell Immunol

    (1973)
  • J.E. Pearl et al.

    Inflammation and lymphocyte activation during mycobacterial infection in the interferon-γ-deficient mouse

    Cell Immunol

    (2001)
  • J.L. Flynn et al.

    Tumor necrosis-alpha is required in the protective immune response against Mycobacterium tuberculosis in mice

    Immunity

    (1995)
  • I.M. Orme

    Immunity to mycobacteria

    Curr Opin Immunol

    (1993)
  • I.M. Orme et al.

    Adoptive protection of the Mycobacterium tuberculosis-infected lung. Dissociation between cells that passively transfer protective immunity and those that transfer delayed-type hypersensitivity to tuberculin

    Cell Immunol

    (1984)
  • D.B. Sisk

    Physiology

  • J. Cegielski et al.

    The global tuberculosis situation. Progress and problems in the 20th century, prospects for the 21st century

    Infect Dis Clin North Am

    (2002)
  • V. Pathania et al.

    TB patients and private for care providers in India

    WHO/TB/97

    (1997)
  • S.H.E. Kaufmann

    Is the development of tuberculosis vaccine possible?

    Nat Med

    (2000)
  • P.M. Udani

    BCG vaccination in India and tuberculosis in children; newer facts

    Indian J Pediatr

    (1994)
  • F.M. Collins

    Immunology of tuberculosis

    Am Rev Respir Dis

    (1982)
  • C.H. Browning et al.

    Studies on experimental tuberculosis in mice. I. The susceptibility of mice to inoculation with tubercle bacilli

    J Hyg

    (1926)
  • F.D. Gunn et al.

    Susceptibility of white mouse to tuberculosis

    Proc Soc Exp Biol Med

    (1933)
  • G.P. Youmans et al.

    Streptomycin in experimental tuberculosis

    Am Rev Tuberc

    (1945)
  • G.W. Raleigh et al.

    The use of mice in experimental chemotherapy of tuberculosis

    J Infect Dis

    (1949)
  • C.M. McKee et al.

    The use of mouse in a standard test for anti-tuberculosis activity of compounds of natural or synthetic origin

    Am Rev Tuberc

    (1949)
  • R.J. Dubos et al.

    Differential characteristics in vitro and in vivo of several sub-strains of BCG. IV. Immunizing effectiveness

    Am Rev Tuberc

    (1956)
  • C.H. Pierce et al.

    Differential characteristics in vitro and vivo of sub-strains of BCG. III. Multiplication and survival in vivo

    Am Rev Tuberc

    (1956)
  • M.J. Lefford

    Transfer of adoptive immunity to tuberculosis in mice

    Infect Immun

    (1975)
  • G.B. Mackaness

    The immunology of antituberculous immunity

    Am Rev Respir Dis

    (1968)
  • F.M. Collins

    Cellular antimicrobial immunity

    Crit Rev Microbiol

    (1979)
  • S.H.E. Kaufmann et al.

    The role of cell-mediated immunity in bacterial infections

    Rev Infect Dis

    (1981)
  • L.N. Brown

    Animal models and immune mechanisms in mycobacterial infection

  • R.J. Dubos

    Rapid and submerged growth of mycobacteria in liquid media

    Proc Soc Exp Biol Med

    (1945)
  • F. Fenner et al.

    The enumeration of viable tubercle bacilli in cultures and infected tissues

    Ann N Y Acad Sci

    (1949)
  • F. Fenner

    The enumeration of viable tubercle bacilli by surface plate counts

    Am Rev Tuberc

    (1951)
  • F.M. Collins et al.

    A comparative study of the virulence of Mycobacterium tuberculosis measured in mice and guinea pigs

    Am Rev Respir Dis

    (1969)
  • F.M. Collins et al.

    The effect of cultural conditions on the distribution of Mycobacterium tuberculosis in the spleens and lungs of specific pathogen-free mice

    Am Rev Respir Dis

    (1974)
  • T.H. Kim et al.

    Long term preservation and storage of mycobacteria

    Appl Microbiol

    (1972)
  • T.H. Kim et al.

    Preservation of mycobacteria: 100% viability of suspensions stored at −70 °C

    Appl Microbiol

    (1973)
  • F.M. Collins et al.

    Relative immunogenicity of streptomycin-susceptible and -resistant strains of BCG. II. Effect of the route of inoculation on growth and immunogenicity

    Am Rev Respir Dis

    (1975)
  • F.M. Collins et al.

    Distribution of mycobacteria in vivo grown in the organs of intravenously infected mice

    Am Rev Respir Dis

    (1976)
  • D.N. McMurray et al.

    Response to Mycobacterium tuberculosis BCG vaccination in protein- and zinc-deficient guinea pigs

    Infect Immun

    (1983)
  • J. Chan et al.

    Effects of protein calorie malnutrition on tuberculosis in mice

    Proc Natl Acad Sci USA

    (1996)
  • J. Chan et al.

    Killing of virulent Mycobacterium tuberculosis by reactive nitrogen intermediates produced by activated murine macrophages

    J Exp Med

    (1992)
  • J.P. Cegielski et al.

    The relationship between malnutrition and tuberculosis: evidence from studies in humans and experimental animals

    Int J Tuberc Lung Dis

    (2004)
  • I.M. Orme

    The kinetics of emergence and loss of mediator T lymphocytes acquired in response to infection with Mycobacterium tuberculosis

    J Immunol

    (1987)
  • M.J. Lefford

    Diseases in mice and rats

  • J. Chan et al.

    Lipoarabinomannan: a possible virulence factor involved in persistence of Mycobacterium tuberculosis within macrophages

    Infect Immun

    (1991)
  • Cited by (104)

    • Human mesenchymal stem cell based intracellular dormancy model of Mycobacterium tuberculosis

      2020, Microbes and Infection
      Citation Excerpt :

      Increased tolerance of MSC-residing M. tuberculosis to RIF and INH during later stages of infection thus clearly indicated that in these specialized stem cells, the pathogen gradually attains increased tolerance to antibiotics, a phenotype that has been associated with dormant bacilli. Characteristic features of M. tuberculosis dormancy as seen in humans is not recapitulated in any available animal models, and a more robust system is needed to study and understand the natural course of infection and disease progression [11]. Studying dormancy in human subjects in vivo is extremely challenging because of the difficulties in obtaining specimens from asymptomatic subjects and unknown niches that potentially harbor dormant bacteria.

    • Lung-on-a-chip platforms for modeling disease pathogenesis

      2019, Organ-on-a-chip: Engineered Microenvironments for Safety and Efficacy Testing
    • Animals in Respiratory Research

      2024, International Journal of Molecular Sciences
    View all citing articles on Scopus
    View full text