Guinea pigs infected by low dose aerosol with the H37Rv strain of Mycobacterium tuberculosis rapi... more Guinea pigs infected by low dose aerosol with the H37Rv strain of Mycobacterium tuberculosis rapidly developed granulomatous lesions in the pulmonary parenchyma and within the intra-thoracic hilar lymph node cluster. Lung lesions showed no predilection for specific lobes and were perivascular, peribronchial and peribronchiolar throughout the subpleural, hilar and pulmonary parenchyma. Marked hilar lymph node enlargement was due to coalescing foci of subcapsular, paracortical and medullary granulomatous inflammation that progressed to necrosis that effaced normal lymph node architecture. Lymph node lesions became severe and progressed more rapidly than pulmonary lesions. Immunization with BCG 6 weeks prior to infection significantly reduced the lung and lymph node lesion burden as well as the progression to necrosis in both tissues. Lymph node inflammation in BCG immunized animals partially resolved and was replaced by fibroblasts and fibrous connective tissue while lesions from non-immunized animals continued to progress to necrosis. We discuss here the observation that the distribution and progression of lung and lymph node lesions in the guinea pig aerosol model of tuberculosis have considerable similarity to the naturally occurring disease in children.
The guinea pig model of tuberculosis is used extensively in different locations to assess the eff... more The guinea pig model of tuberculosis is used extensively in different locations to assess the efficacy of novel tuberculosis vaccines during pre-clinical development. Two key assays are used to measure protection against virulent challenge: a 30 day post-infection assessment of mycobacterial burden and long-term post-infection survival and pathology analysis. To determine the consistency and robustness of the guinea pig model for testing vaccines, a comparative assessment between three sites that are currently involved in testing tuberculosis vaccines from external providers was performed. Each site was asked to test two "subunit" type vaccines in their routine animal model as if testing vaccines from a provider. All sites performed a 30 day study, and one site also performed a long-term survival/pathology study. Despite some differences in experimental approach between the sites, such as the origin of the Mycobacterium tuberculosis strain and the type of aerosol exposure device used to infect the animals and the source of the guinea pigs, the data obtained between sites were consistent in regard to the ability of each "vaccine" tested to reduce the mycobacterial burden. The observations also showed that there was good concurrence between the results of short-term and long-term studies. This validation exercise means that efficacy data can be compared between sites.
Tumor necrosis factor-alpha (TNF-alpha) plays critical and opposing roles in the pathogenesis of ... more Tumor necrosis factor-alpha (TNF-alpha) plays critical and opposing roles in the pathogenesis of tuberculosis (TB). We examined the effects of Mycobacterium bovis BCG vaccination on TNF-alpha production in three distinct guinea pig leukocyte populations before and after pulmonary infection with M. tuberculosis H37Rv. Following BCG vaccination alone, and following challenge, bronchoalveolar lavage cells (BALC), resident peritoneal cells (PC), and splenocytes (SPC) were stimulated with purified protein derivative (PPD). Before virulent challenge, BCG vaccination clearly enhanced the ability of BALC, PC and SPC to produce TNF-alpha in response to PPD stimulation ex vivo. Following challenge, the TNF-alpha production of all three leukocyte populations from BCG-vaccinated animals remained relatively constant at pre-challenged levels. In sharp contrast, 5 weeks post-challenge, all three leukocyte populations from unvaccinated animals produced very high amounts of TNF-alpha in response to PPD. Three weeks post-challenge, SPC from one of the unvaccinated animals produced higher levels of TNF-alpha but the others produced lower levels of TNF-alpha than BCG-vaccinated animals. As expected, BCG vaccination reduced the levels of virulent mycobacteria in both the lungs and spleens. Thus, BCG vaccination allows guinea pigs to modulate TNF-alpha levels in conjunction with a reduction in bacillary loads in their tissues.
Abstract Pathogen-free guinea pigs maintained on isocaloric, purified low protein (LP), low zinc ... more Abstract Pathogen-free guinea pigs maintained on isocaloric, purified low protein (LP), low zinc (LZ) and control (C) diets and commercial chow (Ch) were vaccinated with viable Mycobacterium bovis BCG and sacrificed 4, 5, and 6 weeks later. Both groups of malnourished animals showed weight loss and zinc-deficient guinea pigs had reduced plasma zinc levels. Serum proteins and albumin levels were reduced in LP guinea pigs. Animals on LP and LZ diets showed significantly impaired delayed hypersensitivity to dinitrochlorobenzene and tuberculin when compared to animals consuming the C and the CH regimen. The ability of peritoneal exudate cells to produce macrophage migration inhibition factor (MIF) when stimulated with PPD in vitro was diminished in animals maintained on the LZ diet for more than 5 weeks, but was unaffected by protein deficiency. Reduced capacity to produce functional lymphokines may contribute to skin test anergy in chronic zinc deficiency, but does not explain loss of delayed hypersensitivity in protein-deprived guinea pigs.
We utilized magnetic resonance imaging to visualize lesions in the lungs of guinea pigs infected ... more We utilized magnetic resonance imaging to visualize lesions in the lungs of guinea pigs infected by low-dose aerosol exposure to Mycobacterium tuberculosis. Lesions were prominent in such images, and colorized three-dimensional reconstructions of images revealed a very uniform distribution in the lungs. Lesion numbers after 1 month were approximately similar to the aerosol exposure algorithm, suggesting that each was established by a single bacterium. Numbers of lesions in unprotected and vaccinated animals were similar over the first month but increased thereafter in the control animals, indicating secondary lesion development. Whereas lesion sizes increased progressively in control guinea pigs, lesions remained small in BCG-vaccinated animals. A prominent feature of the disease pathology in unprotected animals was rapid and severe lymphadenopathy of the mediastinal lymph node cluster, which is paradoxical given the strong state of cellular immunity at this time. Further developmen...
Guinea pigs exposed to very small numbers of virulent tubercle bacilli by the respiratory route d... more Guinea pigs exposed to very small numbers of virulent tubercle bacilli by the respiratory route develop a disease which mimics many of the important features of the pathogenesis of human tuberculosis (TB), including the expression of strong protective immunity following vaccination with BCG. In order to elucidate the precise immunological mechanisms of vaccine-induced resistance in this model, both mRNA and protein assays for several guinea pig cytokines and chemokines have been developed. The coordinated expression of cytokine and chemokine mRNA and protein was examined in various leukocyte populations and in inflammatory cells and fluid collected following the induction of tuberculous pleurisy in BCG-vaccinated guinea pigs. Real-time RT-PCR assays revealed that the mRNA levels for IFNgamma, TNFalpha, and IL-8 rose over the first few days of TB pleuritis and then declined over the 9 days of the study. Injection of anti-TGFbeta on day 8 following pleurisy induction resulted in significant changes in cytokine mRNA levels and PPD-induced proliferation in pleural effusion lymphocytes taken 24h later. BCG vaccination induced significantly higher levels of bioactive TNFalpha protein in the supernatants of alveolar, peritoneal and splenic cells from BCG-vaccinated guinea pigs cultured in the presence of attenuated or virulent mycobacteria. In sharp contrast, following virulent challenge, all three cell types from BCG-vaccinated guinea pigs produced significantly less TNFalpha. Thus, BCG vaccination appears to modulate the potentially harmful effects of TNFalpha in this model of pulmonary TB. Levels of mRNA for IL-12p40 were upregulated by exposure of infected and uninfected macrophages to recombinant guinea pig (rgp)TNFalpha. The intracellular survival of mycobacteria was enhanced when endogeous TNFalpha activity was neutralized with anti-rgpTNFalpha antiserum. rgp RANTES (CCL5) upregulated mRNA levels for TNFalpha, IL-1beta, MCP-1 (CCL2), and IL-8 (CXCL8) in alveolar and peritoneal macrophages. These results illustrate the profound effects of prior vaccination with BCG on the cytokine and chemokine responses of distinct cell populations in the guinea pig following exposure to attenuated and virulent strains of M. tuberculosis.
ABSTRACTGamma interferon (IFN-γ) plays a critical role in the protective immune responses against... more ABSTRACTGamma interferon (IFN-γ) plays a critical role in the protective immune responses against mycobacteria. We previously cloned a cDNA coding for guinea pig IFN-γ (gpIFN-γ) and reported that BCG vaccination induced a significant increase in the IFN-γ mRNA expression in guinea pig cells in response to living mycobacteria and that the virulent H37Rv strain ofMycobacterium tuberculosisstimulated less IFN-γ mRNA than did the attenuated H37Ra strain. In this study, we successfully expressed and characterized recombinant gpIFN-γ with a histidine tag at the N terminus (His-tagged rgpIFN-γ) inEscherichia coli. rgpIFN-γ was identified as an 18-kDa band in the insoluble fraction; therefore, the protein was purified under denaturing conditions and renatured. N-terminal amino acid sequencing of the recombinant protein yielded the sequence corresponding to the N terminus of His-tagged gpIFN-γ. The recombinant protein upregulated major histocompatibility complex class II expression in perito...
The influence of acute dietary protein restriction on the development of Babesia microti infectio... more The influence of acute dietary protein restriction on the development of Babesia microti infection in the mouse model was investigated. Female mice consuming a diet either devoid of protein or adequate with respect to protein were infected with B. microti-parasitized erythrocytes and sacrificed 7 days later. Absence of dietary protein resulted in a delay in the onset of infection and a significantly reduced peak parasitemia. Non-specific antibody responses to heterologous erythrocytes and specific anti-babesial antibody titers were impaired in mice consuming the protein-free diets, suggesting that the enhanced resistance to experimental babesiosis observed in protein-malnourished mice is not an antibody-mediated phenomenon. In addition, protein-malnourished mice did not demonstrate significantly lower concentrations of the serum complement component, C3, which has been implicated as a participant in the invasion process of host erythrocytes by parasites. Serum C3 levels were significantly reduced in infected mice consuming both diets. The mechanism by which acute protein deprivation protects mice against lethal babesiosis remains to be determined.
Guinea pigs infected by low dose aerosol with the H37Rv strain of Mycobacterium tuberculosis rapi... more Guinea pigs infected by low dose aerosol with the H37Rv strain of Mycobacterium tuberculosis rapidly developed granulomatous lesions in the pulmonary parenchyma and within the intra-thoracic hilar lymph node cluster. Lung lesions showed no predilection for specific lobes and were perivascular, peribronchial and peribronchiolar throughout the subpleural, hilar and pulmonary parenchyma. Marked hilar lymph node enlargement was due to coalescing foci of subcapsular, paracortical and medullary granulomatous inflammation that progressed to necrosis that effaced normal lymph node architecture. Lymph node lesions became severe and progressed more rapidly than pulmonary lesions. Immunization with BCG 6 weeks prior to infection significantly reduced the lung and lymph node lesion burden as well as the progression to necrosis in both tissues. Lymph node inflammation in BCG immunized animals partially resolved and was replaced by fibroblasts and fibrous connective tissue while lesions from non-immunized animals continued to progress to necrosis. We discuss here the observation that the distribution and progression of lung and lymph node lesions in the guinea pig aerosol model of tuberculosis have considerable similarity to the naturally occurring disease in children.
The guinea pig model of tuberculosis is used extensively in different locations to assess the eff... more The guinea pig model of tuberculosis is used extensively in different locations to assess the efficacy of novel tuberculosis vaccines during pre-clinical development. Two key assays are used to measure protection against virulent challenge: a 30 day post-infection assessment of mycobacterial burden and long-term post-infection survival and pathology analysis. To determine the consistency and robustness of the guinea pig model for testing vaccines, a comparative assessment between three sites that are currently involved in testing tuberculosis vaccines from external providers was performed. Each site was asked to test two "subunit" type vaccines in their routine animal model as if testing vaccines from a provider. All sites performed a 30 day study, and one site also performed a long-term survival/pathology study. Despite some differences in experimental approach between the sites, such as the origin of the Mycobacterium tuberculosis strain and the type of aerosol exposure device used to infect the animals and the source of the guinea pigs, the data obtained between sites were consistent in regard to the ability of each "vaccine" tested to reduce the mycobacterial burden. The observations also showed that there was good concurrence between the results of short-term and long-term studies. This validation exercise means that efficacy data can be compared between sites.
Tumor necrosis factor-alpha (TNF-alpha) plays critical and opposing roles in the pathogenesis of ... more Tumor necrosis factor-alpha (TNF-alpha) plays critical and opposing roles in the pathogenesis of tuberculosis (TB). We examined the effects of Mycobacterium bovis BCG vaccination on TNF-alpha production in three distinct guinea pig leukocyte populations before and after pulmonary infection with M. tuberculosis H37Rv. Following BCG vaccination alone, and following challenge, bronchoalveolar lavage cells (BALC), resident peritoneal cells (PC), and splenocytes (SPC) were stimulated with purified protein derivative (PPD). Before virulent challenge, BCG vaccination clearly enhanced the ability of BALC, PC and SPC to produce TNF-alpha in response to PPD stimulation ex vivo. Following challenge, the TNF-alpha production of all three leukocyte populations from BCG-vaccinated animals remained relatively constant at pre-challenged levels. In sharp contrast, 5 weeks post-challenge, all three leukocyte populations from unvaccinated animals produced very high amounts of TNF-alpha in response to PPD. Three weeks post-challenge, SPC from one of the unvaccinated animals produced higher levels of TNF-alpha but the others produced lower levels of TNF-alpha than BCG-vaccinated animals. As expected, BCG vaccination reduced the levels of virulent mycobacteria in both the lungs and spleens. Thus, BCG vaccination allows guinea pigs to modulate TNF-alpha levels in conjunction with a reduction in bacillary loads in their tissues.
Abstract Pathogen-free guinea pigs maintained on isocaloric, purified low protein (LP), low zinc ... more Abstract Pathogen-free guinea pigs maintained on isocaloric, purified low protein (LP), low zinc (LZ) and control (C) diets and commercial chow (Ch) were vaccinated with viable Mycobacterium bovis BCG and sacrificed 4, 5, and 6 weeks later. Both groups of malnourished animals showed weight loss and zinc-deficient guinea pigs had reduced plasma zinc levels. Serum proteins and albumin levels were reduced in LP guinea pigs. Animals on LP and LZ diets showed significantly impaired delayed hypersensitivity to dinitrochlorobenzene and tuberculin when compared to animals consuming the C and the CH regimen. The ability of peritoneal exudate cells to produce macrophage migration inhibition factor (MIF) when stimulated with PPD in vitro was diminished in animals maintained on the LZ diet for more than 5 weeks, but was unaffected by protein deficiency. Reduced capacity to produce functional lymphokines may contribute to skin test anergy in chronic zinc deficiency, but does not explain loss of delayed hypersensitivity in protein-deprived guinea pigs.
We utilized magnetic resonance imaging to visualize lesions in the lungs of guinea pigs infected ... more We utilized magnetic resonance imaging to visualize lesions in the lungs of guinea pigs infected by low-dose aerosol exposure to Mycobacterium tuberculosis. Lesions were prominent in such images, and colorized three-dimensional reconstructions of images revealed a very uniform distribution in the lungs. Lesion numbers after 1 month were approximately similar to the aerosol exposure algorithm, suggesting that each was established by a single bacterium. Numbers of lesions in unprotected and vaccinated animals were similar over the first month but increased thereafter in the control animals, indicating secondary lesion development. Whereas lesion sizes increased progressively in control guinea pigs, lesions remained small in BCG-vaccinated animals. A prominent feature of the disease pathology in unprotected animals was rapid and severe lymphadenopathy of the mediastinal lymph node cluster, which is paradoxical given the strong state of cellular immunity at this time. Further developmen...
Guinea pigs exposed to very small numbers of virulent tubercle bacilli by the respiratory route d... more Guinea pigs exposed to very small numbers of virulent tubercle bacilli by the respiratory route develop a disease which mimics many of the important features of the pathogenesis of human tuberculosis (TB), including the expression of strong protective immunity following vaccination with BCG. In order to elucidate the precise immunological mechanisms of vaccine-induced resistance in this model, both mRNA and protein assays for several guinea pig cytokines and chemokines have been developed. The coordinated expression of cytokine and chemokine mRNA and protein was examined in various leukocyte populations and in inflammatory cells and fluid collected following the induction of tuberculous pleurisy in BCG-vaccinated guinea pigs. Real-time RT-PCR assays revealed that the mRNA levels for IFNgamma, TNFalpha, and IL-8 rose over the first few days of TB pleuritis and then declined over the 9 days of the study. Injection of anti-TGFbeta on day 8 following pleurisy induction resulted in significant changes in cytokine mRNA levels and PPD-induced proliferation in pleural effusion lymphocytes taken 24h later. BCG vaccination induced significantly higher levels of bioactive TNFalpha protein in the supernatants of alveolar, peritoneal and splenic cells from BCG-vaccinated guinea pigs cultured in the presence of attenuated or virulent mycobacteria. In sharp contrast, following virulent challenge, all three cell types from BCG-vaccinated guinea pigs produced significantly less TNFalpha. Thus, BCG vaccination appears to modulate the potentially harmful effects of TNFalpha in this model of pulmonary TB. Levels of mRNA for IL-12p40 were upregulated by exposure of infected and uninfected macrophages to recombinant guinea pig (rgp)TNFalpha. The intracellular survival of mycobacteria was enhanced when endogeous TNFalpha activity was neutralized with anti-rgpTNFalpha antiserum. rgp RANTES (CCL5) upregulated mRNA levels for TNFalpha, IL-1beta, MCP-1 (CCL2), and IL-8 (CXCL8) in alveolar and peritoneal macrophages. These results illustrate the profound effects of prior vaccination with BCG on the cytokine and chemokine responses of distinct cell populations in the guinea pig following exposure to attenuated and virulent strains of M. tuberculosis.
ABSTRACTGamma interferon (IFN-γ) plays a critical role in the protective immune responses against... more ABSTRACTGamma interferon (IFN-γ) plays a critical role in the protective immune responses against mycobacteria. We previously cloned a cDNA coding for guinea pig IFN-γ (gpIFN-γ) and reported that BCG vaccination induced a significant increase in the IFN-γ mRNA expression in guinea pig cells in response to living mycobacteria and that the virulent H37Rv strain ofMycobacterium tuberculosisstimulated less IFN-γ mRNA than did the attenuated H37Ra strain. In this study, we successfully expressed and characterized recombinant gpIFN-γ with a histidine tag at the N terminus (His-tagged rgpIFN-γ) inEscherichia coli. rgpIFN-γ was identified as an 18-kDa band in the insoluble fraction; therefore, the protein was purified under denaturing conditions and renatured. N-terminal amino acid sequencing of the recombinant protein yielded the sequence corresponding to the N terminus of His-tagged gpIFN-γ. The recombinant protein upregulated major histocompatibility complex class II expression in perito...
The influence of acute dietary protein restriction on the development of Babesia microti infectio... more The influence of acute dietary protein restriction on the development of Babesia microti infection in the mouse model was investigated. Female mice consuming a diet either devoid of protein or adequate with respect to protein were infected with B. microti-parasitized erythrocytes and sacrificed 7 days later. Absence of dietary protein resulted in a delay in the onset of infection and a significantly reduced peak parasitemia. Non-specific antibody responses to heterologous erythrocytes and specific anti-babesial antibody titers were impaired in mice consuming the protein-free diets, suggesting that the enhanced resistance to experimental babesiosis observed in protein-malnourished mice is not an antibody-mediated phenomenon. In addition, protein-malnourished mice did not demonstrate significantly lower concentrations of the serum complement component, C3, which has been implicated as a participant in the invasion process of host erythrocytes by parasites. Serum C3 levels were significantly reduced in infected mice consuming both diets. The mechanism by which acute protein deprivation protects mice against lethal babesiosis remains to be determined.
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