1
|
Thacker VV, Dhar N, Sharma K, Barrile R, Karalis K, McKinney JD. A lung-on-chip model of early Mycobacterium tuberculosis infection reveals an essential role for alveolar epithelial cells in controlling bacterial growth. eLife 2020; 9:59961. [PMID: 33228849 PMCID: PMC7735758 DOI: 10.7554/elife.59961] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 11/10/2020] [Indexed: 12/14/2022] Open
Abstract
We establish a murine lung-on-chip infection model and use time-lapse imaging to reveal the dynamics of host-Mycobacterium tuberculosis interactions at an air-liquid interface with a spatiotemporal resolution unattainable in animal models and to probe the direct role of pulmonary surfactant in early infection. Surfactant deficiency results in rapid and uncontrolled bacterial growth in both macrophages and alveolar epithelial cells. In contrast, under normal surfactant levels, a significant fraction of intracellular bacteria are non-growing. The surfactant-deficient phenotype is rescued by exogenous addition of surfactant replacement formulations, which have no effect on bacterial viability in the absence of host cells. Surfactant partially removes virulence-associated lipids and proteins from the bacterial cell surface. Consistent with this mechanism, the attenuation of bacteria lacking the ESX-1 secretion system is independent of surfactant levels. These findings may partly explain why smokers and elderly persons with compromised surfactant function are at increased risk of developing active tuberculosis. Tuberculosis is a contagious respiratory disease caused by the bacterium Mycobacterium tuberculosis. Droplets in the air carry these bacteria deep into the lungs, where they cling onto and infect lung cells. Only small droplets, holding one or two bacteria, can reach the right cells, which means that just a couple of bacterial cells can trigger an infection. But people respond differently to the bacteria: some develop active and fatal forms of tuberculosis, while many show no signs of infection. With no effective tuberculosis vaccine for adults, understanding why individuals respond differently to Mycobacterium tuberculosis may help develop treatments. Different responses to Mycobacterium tuberculosis may stem from the earliest stages of infection, but these stages are difficult to study. For one thing, tracking the movements of the few bacterial cells that initiate infection is tricky. For another, studying the molecules, called ‘surfactants’, that the lungs produce to protect themselves from tuberculosis can prove difficult because these molecules are necessary for the lungs to inflate and deflate normally. Normally, the role of a molecule can be studied by genetically modifying an animal so it does not produce the molecule in question, which provides information as to its potential roles. Unfortunately, due to the role of surfactants in normal breathing, animals lacking them die. Therefore, to reveal the role of some of surfactants in tuberculosis, Thacker et al. used ‘lung-on-chip’ technology. The ‘chip’ (a transparent device made of a polymer compatible with biological tissues) is coated with layers of cells and has channels to simulate air and blood flow. To see what effects surfactants have on M. tuberculosis bacteria, Thacker et al. altered the levels of surfactants produced by the cells on the lung-on-chip device. Two types of mouse cells were grown on the chip: lung cells and immune cells. When cells lacked surfactants, bacteria grew rapidly on both lung and immune cells, but when surfactants were present bacteria grew much slower on both cell types, or did not grow at all. Further probing showed that the surfactants pulled out proteins and fats on the surface of M. tuberculosis that help the bacteria to infect their host, highlighting the protective role of surfactants in tuberculosis. These findings lay the foundations for a system to study respiratory infections without using animals. This will allow scientists to study the early stages of Mycobacterium tuberculosis infection, which is crucial for finding ways to manage tuberculosis.
Collapse
Affiliation(s)
- Vivek V Thacker
- School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland
| | - Neeraj Dhar
- School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland
| | - Kunal Sharma
- School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland
| | | | | | - John D McKinney
- School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland
| |
Collapse
|
2
|
Franco NH, Correia-Neves M, Olsson IAS. Animal welfare in studies on murine tuberculosis: assessing progress over a 12-year period and the need for further improvement. PLoS One 2012; 7:e47723. [PMID: 23110093 PMCID: PMC3482232 DOI: 10.1371/journal.pone.0047723] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Accepted: 09/14/2012] [Indexed: 11/19/2022] Open
Abstract
There is growing concern over the welfare of animals used in research, in particular when these animals develop pathology. The present study aims to identify the main sources of animal distress and to assess the possible implementation of refinement measures in experimental infection research, using mouse models of tuberculosis (TB) as a case study. This choice is based on the historical relevance of mouse studies in understanding the disease and the present and long-standing impact of TB on a global scale. Literature published between 1997 and 2009 was analysed, focusing on the welfare impact on the animals used and the implementation of refinement measures to reduce this impact. In this 12-year period, we observed a rise in reports of ethical approval of experiments. The proportion of studies classified into the most severe category did however not change significantly over the studied period. Information on important research parameters, such as method for euthanasia or sex of the animals, were absent in a substantial number of papers. Overall, this study shows that progress has been made in the application of humane endpoints in TB research, but that a considerable potential for improvement remains.
Collapse
Affiliation(s)
- Nuno Henrique Franco
- IBMC - Institute for Molecular and Cell Biology, Laboratory Animal Science Group, University of Porto, Portugal.
| | | | | |
Collapse
|
3
|
Biketov S, Potapov V, Ganina E, Downing K, Kana BD, Kaprelyants A. The role of resuscitation promoting factors in pathogenesis and reactivation of Mycobacterium tuberculosis during intra-peritoneal infection in mice. BMC Infect Dis 2007; 7:146. [PMID: 18086300 PMCID: PMC2241625 DOI: 10.1186/1471-2334-7-146] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 12/17/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mycobacterium tuberculosis can enter into a dormant state which has resulted in one third of the world's population being infected with latent tuberculosis making the study of latency and reactivation of utmost importance. M. tuberculosis encodes five resuscitation promoting factors (Rpfs) that bear strong similarity to a lysozyme-like enzyme previously implicated in reactivation of dormant bacteria in vitro. We have developed an intraperitoneal infection model in mice, with immune modulation, that models chronic infection with similar properties in mouse lungs as those observed in the murine aerosol infection model. We have assessed the behavior of mutants that lack two or three rpf genes in different combinations in our intraperitoneal model. METHODS C57Bl/6 mice were intraperitonealy infected with H37Rv wild type M. tuberculosis or mutant strains that lacked two or three rpf genes in different combinations. After 90 days of infection aminoguanidine (AG) or anti-TNFalpha antibodies were administrated. Organ bacillary loads were determined at various intervals post infection by plating serial dilutions of organ homogenates and enumerating bacteria. RESULTS We found that the rpf triple and double mutants tested were attenuated in their ability to disseminate to mouse lungs after intraperitoneal administration and were defective in their ability to re-grow after immunosuppression induced by administration of aminoguanidine and anti-TNFalpha antibodies. CONCLUSION Rpf proteins may have a significant physiological role for development of chronic TB infection and its reactivation in vivo.
Collapse
Affiliation(s)
- Sergey Biketov
- Bakh Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia.
| | | | | | | | | | | |
Collapse
|
4
|
Senaratne RH, De Silva AD, Williams SJ, Mougous JD, Reader JR, Zhang T, Chan S, Sidders B, Lee DH, Chan J, Bertozzi CR, Riley LW. 5'-Adenosinephosphosulphate reductase (CysH) protects Mycobacterium tuberculosis against free radicals during chronic infection phase in mice. Mol Microbiol 2006; 59:1744-53. [PMID: 16553880 DOI: 10.1111/j.1365-2958.2006.05075.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A major obstacle to tuberculosis (TB) control is the problem of chronic TB infection (CTBI). Here we report that 5'-adenosinephosphosulphate reductase (CysH), an enzyme essential for the production of reduced-sulphur-containing metabolites, is critical for Mycobacterium tuberculosis (Mtb) survival in chronic infection phase in mice. Disruption of cysH rendered Mtb auxotrophic for cysteine and methionine, and attenuated virulence in BALB/c and C57BL/6 immunocompetent mice. The mutant and wild-type Mtb replicated similarly during the acute phase of infection, but the mutant showed reduced viability during the persistent phase of the infection. The cysH mutant caused disease and death after 4-7 weeks of infection in four different groups of mice - Rag1(-/-), NOS2(-/-), gp91phox(-/-) NOS2(-/-) and gp91phox(-/-) mice given aminoguanidine [to suppress the effects of nitric oxide synthase 2 (NOS2)]- indicating minimal metabolic effect on the cysH mutant survival in these mice. The cysH mutant was also susceptible to peroxynitrite and hydrogen peroxide in vitro. These results show that CysH is important for Mtb protection during the chronic infection phase, and that resistance to nitrosative and oxidative stress may be the mechanism of this protection. Thus, this metabolic gene of an intracellular pathogen could have a secondary role in protection against the host immune response. Finally the lack of an endogenous human orthologue of cysH and its possible role in defence against adaptive immunity renders CysH an attractive enzyme for further studies as a target for therapeutics active against CTBI.
Collapse
Affiliation(s)
- Ryan H Senaratne
- School of Public Health, University of California, Berkeley, 94720, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Abstract
As many mononuclear cells from Mycobacterium tuberculosis-infected lung tissues are not available for fluorescence-activated cell sorter (FACS) analysis and the tuberculin test is not feasible in a mouse tuberculosis model, we attempted to develop a rat tuberculosis model. We have previously reported that rat tuberculosis is associated with granulomas that lack central necrosis. In order to develop a better animal model of tuberculosis in immunocompromised humans (tuberculosis associated with HIV infection or tuberculosis of the elderly), we infected F344/N-rnu nude rats with M. tuberculosis via the airborne route. The animals developed pulmonary granulomas with central necrosis encapsulated by dense collagen fibres, closely resembling those of human tuberculosis. The nude rats died of disseminated tuberculosis by the 85th day after aerosol infection, while F344 wild-type rats did not. Interestingly, T-cells that were reactive with anti-CD4 antibody and anti-CD8 antibody, indicating the presence of remnant thymus, were observed in the infected lung tissues of the nude rats. Therefore, T-cell precursors may be present in nude rats. The nude rat tuberculosis model mimics tuberculosis in immunocompromised humans and may provide a suitable model for immunological studies in vivo.
Collapse
Affiliation(s)
- Isamu Sugawara
- Mycobacterial Reference Center, The Research Institute of Tuberculosis, Kiyose, Tokyo 204-0022, Japan.
| | | | | |
Collapse
|
6
|
Chambers MA, Gavier-Widén D, Hewinson RG. Antibody bound to the surface antigen MPB83 ofMycobacterium bovisenhances survival against high dose and low dose challenge. ACTA ACUST UNITED AC 2004; 41:93-100. [PMID: 15145452 DOI: 10.1016/j.femsim.2004.01.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2003] [Revised: 12/18/2003] [Accepted: 01/14/2004] [Indexed: 11/16/2022]
Abstract
Tuberculosis caused by infection with Mycobacterium tuberculosis or Mycobacterium bovis is a significant disease of man and animals. Whilst cellular immunity is the major immunological component required for protection against these organisms, recent reports have suggested that monoclonal antibodies can modify infection with M. tuberculosis. To test whether the same was true for M. bovis infection, we determined the effect of preincubation of M. bovis with a monoclonal antibody on subsequent intravenous infection of mice. Antibodies bound to the surface of M. bovis increased the survival time of mice infected with M. bovis and changed the morphology of granulomas and the distribution of acid-fast bacilli in the lung. These studies suggest that antibodies directed to the surface of virulent mycobacteria can modulate their virulence in vivo.
Collapse
Affiliation(s)
- Mark A Chambers
- TB Research Group, Department of Statutory and Exotic Bacterial Diseases, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, Surrey KT15 3NB, UK.
| | | | | |
Collapse
|
7
|
Roach DR, Bean AGD, Demangel C, France MP, Briscoe H, Britton WJ. TNF regulates chemokine induction essential for cell recruitment, granuloma formation, and clearance of mycobacterial infection. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:4620-7. [PMID: 11971010 DOI: 10.4049/jimmunol.168.9.4620] [Citation(s) in RCA: 519] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Host immunity to mycobacterial infection is dependent on the activation of T lymphocytes and their recruitment with monocytes to form granulomas. These discrete foci of activated macrophages and lymphocytes provide a microenvironment for containing the infection. The cytokine, TNF, is essential for the formation and maintenance of granulomas, but the mechanisms by which TNF regulates these processes are unclear. We have compared the responses of TNF-deficient (TNF(-/-)) and wild-type C57BL/6 mice to infection with Mycobacterium smegmatis, a potent inducer of TNF, and virulent Mycobacterium tuberculosis to delineate the TNF-dependent and -independent components of the process. The initial clearance of M. smegmatis was TNF independent, but TNF was required for the early expression of mRNA encoding C-C and C-X-C chemokines and the initial recruitment of CD11b(+) macrophages and CD4(+) T cells to the liver during the second week of infection. Late chemokine expression and cell recruitment developed in TNF(-/-) mice associated with enhanced Th1-like T cell responses and mycobacterial clearance, but recruited leukocytes did not form tight granulomas. Infection of TNF(-/-) mice with M. tuberculosis also resulted in an initial delay in chemokine induction and cellular recruitment to the liver. Subsequently, increased mRNA expression was evident in TNF(-/-) mice, but the loosely associated lymphocytes and macrophages failed to form granulomas and prevent progressive infection. Therefore, TNF orchestrates early induction of chemokines and initial leukocyte recruitment, but has an additional role in the aggregation of leukocytes into functional granulomas capable of controlling virulent mycobacterial infection.
Collapse
Affiliation(s)
- Daniel R Roach
- Centenary Institute of Cancer Medicine and Cell Biology, Newton, Sydney, New South Wales, Australia
| | | | | | | | | | | |
Collapse
|
8
|
Young DB. Novel strategies for intervention targeted at mycobacterial persistence. SCANDINAVIAN JOURNAL OF INFECTIOUS DISEASES 2002; 33:403-4. [PMID: 11450856 DOI: 10.1080/00365540152029837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Effective global control of tuberculosis is likely to require intervention at multiple points in the course of infection. In addition to existing approaches based on treatment of active disease and preventive vaccination of unexposed individuals, current research on the biology of mycobacterial persistence suggests the potential for the development of novel disease-control strategies targeted at infected asymptomatic populations.
Collapse
Affiliation(s)
- D B Young
- Imperial College School of Medicine, London, UK
| |
Collapse
|
9
|
Abstract
The increasing incidence of disease associated with HIV infection highlights the crucial role of the immune response in susceptibility to tuberculosis and has stimulated renewed efforts to develop improved vaccines. Vaccine targets include prevention of infection in naive individuals, prevention of re-activation in individuals harbouring latent infection, and prevention of relapse by immunotherapy in tuberculosis patients. Advances in mycobacterial molecular genetics have facilitated development of a range of live attenuated and subunit vaccine candidates that have been screened in experimental models of infection. Evaluation of the immunogenicity of selected candidate vaccines in clinical trials should be combined with a continuation of fundamental research on the immune response to mycobacterial infection and persistence.
Collapse
Affiliation(s)
- Douglas B Young
- Centre for Molecular Microbiology and Infection, Faculty of Medicine, Imperial College of Science, Technology and Medicine, South Kensington, London, UK
| | | |
Collapse
|
10
|
Leal IS, Smedegård B, Andersen P, Appelberg R. Failure to induce enhanced protection against tuberculosis by increasing T-cell-dependent interferon-gamma generation. Immunology 2001; 104:157-61. [PMID: 11683955 PMCID: PMC1783293 DOI: 10.1046/j.1365-2567.2001.01305.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We evaluated the use of recombinant human interleukin-6 (rhIL-6) and a monoclonal antibody specific for interferon-gamma (IFN-gamma) as co-adjuvants in a subunit vaccine against tuberculosis consisting of the culture filtrate proteins of Mycobacterium tuberculosis (ST-CF) emulsified in the adjuvant dimethyl-dioctadecylammonium bromide (DDA). Both the addition of rhIL-6 and the neutralization of IFN-gamma resulted in an increased T helper type 1 (Th1) response characterized by enhanced IFN-gamma production and cell proliferation. Nevertheless, this did not result in the enhancement of protection against either an intravenous or an aerosol M. tuberculosis challenge. Our data stress the need to identify further correlates of protection in addition to IFN-gamma production to screen vaccines against tuberculosis infection.
Collapse
Affiliation(s)
- I S Leal
- Laboratory of Microbiology and Immunology of Infection, Institute for Molecular and Cell Biology, University of Porto, Porto, Portugal
| | | | | | | |
Collapse
|
11
|
Dannenberg AM, Collins FM. Progressive pulmonary tuberculosis is not due to increasing numbers of viable bacilli in rabbits, mice and guinea pigs, but is due to a continuous host response to mycobacterial products. Tuberculosis (Edinb) 2001; 81:229-42. [PMID: 11466035 DOI: 10.1054/tube.2001.0287] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Tuberculosis (TB) kills more people in the world today than any other infectious disease. A better vaccine to prevent clinical tuberculosis is greatly needed. Candidate vaccines are often evaluated by infecting rabbits, mice and guinea pigs by an aerosol of virulent tubercle bacilli and culturing their lungs for viable bacilli at various times thereafter. In all three species, however, the number of viable bacilli usually does not continuously increase until the host succumbs. The number of viable bacilli increases logarithmically for only about 3 weeks. Then, the host develops delayed-type hypersensitivity (DTH) and cell-mediated immunity (CMI), which keep the number of viable bacilli rather constant during the subsequent weeks. In the immunized host, DTH and CMI stop the logarithmic increase sooner than in the unimmunized controls, so that the stationary bacillary levels that follow are lower. This review analyzes host-parasite interactions in the lungs of rabbits, mice and guinea pigs. All three species cannot prevent inhaled fully virulent tubercle bacilli from establishing an infection, but they differ markedly in the type of the disease produced once it is established.
Collapse
Affiliation(s)
- A M Dannenberg
- Department of Environmental Health Sciences, School of Hygiene and Public Health, The Johns Hopkins University, Baltimore, MD 21205-2179, USA.
| | | |
Collapse
|
12
|
Wangoo A, Sparer T, Brown IN, Snewin VA, Janssen R, Thole J, Cook HT, Shaw RJ, Young DB. Contribution of Th1 and Th2 cells to protection and pathology in experimental models of granulomatous lung disease. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 166:3432-9. [PMID: 11207301 DOI: 10.4049/jimmunol.166.5.3432] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mice that had received adoptive transfer of DO11.10 TCR transgenic T cells polarized toward a Th1 or a Th2 phenotype were challenged with Ag-coated beads or with recombinant Mycobacterium tuberculosis expressing the OVA determinant. The resulting bead-induced pulmonary granulomas reflected the phenotype of the adoptively transferred T cells, with the Th2 cells promoting a fibrotic reaction. Mice receiving Th1 cells mounted an epitope-specific protective response to challenge with recombinant M. tuberculosis. Th2 recipients were characterized by enhanced weight loss and lung fibrosis during acute high-dose infection. The combination of TCR transgenic T cells and epitope-tagged mycobacteria provides a novel experimental model for investigation of the pathogenesis of tuberculosis.
Collapse
Affiliation(s)
- A Wangoo
- Department of Respiratory Medicine, National Heart and Lung Institute, London, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Cassidy JP, Bryson DG, Gutiérrez Cancela MM, Forster F, Pollock JM, Neill SD. Lymphocyte subtypes in experimentally induced early-stage bovine tuberculous lesions. J Comp Pathol 2001; 124:46-51. [PMID: 11428188 DOI: 10.1053/jcpa.2000.0427] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The identity of the lymphocyte subtypes constituting the lymphocytic mantle within developing early-stage lesions of bovine tuberculosis was investigated immunohistochemically in calves inoculated intranasally with 2 x 10(7) colony-forming units of a field isolate of Mycobacterium bovis. Pulmonary lesions were examined 7, 14, 21, 28 and 42 days after inoculation, and bronchial lymph node lesions at 35 days. The immunolabelling results reported were obtained with monoclonal antibodies against two T-cell epitopes (WC1+ gamma delta and CD2+) and against B-cell epitopes. Large numbers of CD2+ T-lymphocytes were observed around developing areas of necrosis throughout the study; WC1+ gamma delta cells, however, were more numerous at these sites up to and including day 21. On the other hand, aggregates of B lymphocytes did not become prominent in areas adjacent to lesions until day 42. The results suggest that these lymphocyte phenotypes play a role in the pathogenesis of early-stage lesions.
Collapse
Affiliation(s)
- J P Cassidy
- Veterinary Sciences Division, Department of Agriculture and Rural Development for Northern Ireland, Stoney Road, Stormont, Belfast BT4 3SD, Northern Ireland
| | | | | | | | | | | |
Collapse
|
14
|
Guleria I, Teitelbaum R, McAdam RA, Kalpana G, Jacobs WR, Bloom BR. Auxotrophic vaccines for tuberculosis. Nat Med 1996; 2:334-7. [PMID: 8612234 DOI: 10.1038/nm0396-334] [Citation(s) in RCA: 138] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Tuberculosis is responsible for the deaths of more people each year than any other single infectious disease, with greater than 7 million new cases and 2 million deaths annually. It remains the largest attributable cause of death in HIV-infected individuals, responsible for 32% of deaths of HIV-infected individuals in Africa. The only currently available vaccine for tuberculosis, bacille Calmette-Guerin (BCG) is the most widely used vaccine in the world, being administered to approximately 100 million children each year. Although untoward effects were not seen in several studies of HIV-seropositive children, the safety of live attenuated BCG vaccine in HIV-positive adults remains unknown and a matter of some concern. To obviate potential adverse affects of BCG vaccines in immunodeficient individuals, we have studied five auxotrophic strains of BCG produced by insertional mutagenesis for safety in administration to mice with severe combined immunodeficiency disease (SCID), and for protection in a susceptible strain of mice. The results indicate that viable BCG could no longer be detected in mice receiving the auxotrophs after 16-32 weeks, and that infected SCID mice survived for at least 230 days. In contrast, all SCID mice succumbed within eight weeks to conventional BCG vaccine. When susceptible BALB/c mice were immunized with auxotrophs and subsequently challenged with virulent Mycobacterium tuberculosis, several of the auxotrophs produced comparable protection against intravenous and intratracheal challenge with M. tuberculosis relative to conventional BCG. These results suggest that auxotrophic strains of BCG represent a potentially safe and useful vaccine against tuberculosis for populations at risk for HIV.
Collapse
Affiliation(s)
- I Guleria
- Howard Hughes Medical Institute, Bronx, New York 10461, USA
| | | | | | | | | | | |
Collapse
|