Todd M. Lasco

The Protective Effect of the Mycobacterium bovis BCG Vaccine Is Increased by Coadministration with the Mycobacterium tuberculosis 72-Kilodalton Fusion Polyprotein Mtb72F in M. tuberculosis-Infected Guinea Pigs

ABSTRACT A tuberculosis vaccine candidate consisting of a 72-kDa polyprotein or fusion protein based upon the Mtb32 and Mtb39 antigens of Mycobacterium tuberculosis and designated Mtb72F was tested for its protective capacity as a potential adjunct to the Mycobacterium bovis BCG vaccine in the mouse and guinea pig models of this disease. Formulation of recombinant Mtb72F (rMtb72F) in an AS02A adjuvant enhanced the Th1 response to BCG in mice but did not further reduce the bacterial load in the lungs after aerosol challenge infection. In the more stringent guinea pig disease model, rMtb72F delivered by coadministration with BCG vaccination significantly improved the survival of these animals compared to BCG alone, with some animals still alive and healthy in their appearance at >100 weeks post-aerosol challenge. A similar trend was observed with guinea pigs in which BCG vaccination was boosted by DNA vaccination, although this increase was not statistically significant due to excellent protection conferred by BCG alone. Histological examination of the lungs of test animals indicated that while BCG controls eventually died from overwhelming lung consolidation, the majority of guinea pigs receiving BCG mixed with rMtb72F or boosted twice with Mtb72F DNA had mostly clear lungs with minimal granulomatous lesions. Lesions were still prominent in guinea pigs receiving BCG and the Mtb72F DNA boost, but there was considerable evidence of lesion healing and airway remodeling and reestablishment. These data support the hypothesis that the coadministration or boosting of BCG vaccination with Mtb72F may limit the lung consolidation seen with BCG alone and may promote lesion resolution and healing. Collectively, these data suggest that enhancing BCG is a valid vaccination strategy for tuberculosis that is worthy of clinical evaluation.

Non-clinical efficacy and safety of HyVac4:IC31 vaccine administered in a BCG prime-boost regimen

Despite the extensive success with the introduction of M. bovis Bacille Calmette-Guérin (BCG), tuberculosis (TB) remains a major global epidemic infecting between 8 and 9 million people annually with an estimated 1.7 million deaths each year. However, because of its demonstrated effectiveness against some of the most severe forms of childhood TB, it is now realized that BCG vaccination of newborns is unlikely to be replaced. Therefore, BCG or an improved BCG will continue to be used as a prime TB vaccine and there is a need to develop effective boost vaccines that would enhance and prolong the protective immunity induced by BCG prime immunization. We report on a heterologous booster approach using two highly immunogenic TB antigens comprising Ag85B and TB10.4 (HyVac4) delivered as a fusion molecule and formulated in the proprietary adjuvant IC31. This vaccine was found to be immunogenic and demonstrated greater protection in the more stringent guinea pig model of pulmonary tuberculosis than BCG alone when used in a prime/boost regimen. Significant difference in lung involvement was observed for all animals in the HyVac4 boosted group compared to BCG alone regardless of time to death or sacrifice. A vaccine toxicology study of the HyVac4:IC31 regimen was performed and it was judged safe to advance the vaccine into clinical trials. Therefore, all non-clinical data supports the suitability of HyVac4 as a safe, immunogenic, and effective vaccination in a prime-boost regimen with BCG.

Recombinant guinea pig tumor necrosis factor alpha stimulates the expression of interleukin-12 and the inhibition of Mycobacterium tuberculosis growth in macrophages

ABSTRACT Tumor necrosis factor alpha (TNF-α) plays an important role in the host immune response to infection with the intracellular pathogen Mycobacterium tuberculosis. It is essential for the formation of protective tuberculous granulomas and regulates the expression of other cytokines which contribute to a protective immune response. Interleukin-12 (IL-12) is known to promote a Th1 response, which is essential for antimycobacterial resistance. Recombinant guinea pig TNF-α (rgpTNF-α) protein (17 kDa) was purified, and its bioactivity was confirmed by its cytotoxicity for L929 fibroblasts. High titers of polyclonal anti-gpTNF-α antibody were obtained by immunization of rabbits. Resident alveolar and peritoneal macrophages were isolated from guinea pigs and infected with either the H37Ra or H37Rv strain of M. tuberculosis. The mRNA levels for TNF-α and IL-12 p40 were measured using real-time PCR. IL-12 p40 mRNA was up-regulated in a dose-dependent manner by rgpTNF-α alone. In infected macrophages, a lower dose of rgpTNF-α intensified the mRNA levels of TNF-α and IL-12 p40. However, higher doses of rgpTNF-α suppressed TNF-α and IL-12 p40 mRNA. The antimycobacterial activity of macrophages was assessed by metabolic labeling of M. tuberculosis with [3H]uracil. Resident alveolar and peritoneal macrophages treated with anti-gpTNF-α antibody to block endogenous TNF-α exhibited increased intracellular mycobacterial growth. These data suggest that the dose of TNF-α is crucial to the stimulation of optimal expression of protective cytokines and that TNF-α contributes to the control of mycobacterial replication to promote host resistance against M. tuberculosis.

Rapid Accumulation of Eosinophils in Lung Lesions in Guinea Pigs Infected with Mycobacterium tuberculosis

ABSTRACT Guinea pig eosinophils were positively identified in bronchoalveolar lavage populations and in the lung granulomas of Mycobacterium tuberculosis-infected guinea pigs. It is possible that the rapid influx of these cells, and their subsequent degranulation during acute pulmonary tuberculosis, may play a key role in the susceptibility of this animal model.

Production and Characterization of Guinea Pig Recombinant Gamma Interferon and Its Effect on Macrophage Activation

ABSTRACT Gamma 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 of Mycobacterium tuberculosis stimulated 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) in Escherichia 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 peritoneal macrophages. The antiviral activity of rgpIFN-γ was demonstrated with a guinea pig fibroblast cell line (104C1) infected with encephalomyocarditis virus. Interestingly, peritoneal macrophages treated with rgpIFN-γ did not produce any nitric oxide but did produce hydrogen peroxide and suppressed the intracellular growth of mycobacteria. Furthermore, rgpIFN-γ induced morphological alterations in cultured macrophages. Thus, biologically active rgpIFN-γ has been successfully produced and characterized in our laboratory. The study of rgpIFN-γ will further increase our understanding of the cellular and molecular responses induced by BCG vaccination in the guinea pig model of pulmonary tuberculosis.

Effect of Neutralizing Transforming Growth Factor β1 on the Immune Response against Mycobacterium tuberculosis in Guinea Pigs

ABSTRACT Transforming growth factor β (TGF-β) is a cytokine which has been shown to suppress the antimycobacterial immune responses of humans and experimental animals. In this study, the contributions of TGF-β to cytokine production in vivo were investigated by using the established guinea pig model of tuberculous pleurisy. Mycobacterium bovis BCG-vaccinated guinea pigs were injected intrapleurally with heat-killed virulent Mycobacterium tuberculosis. Eight days following induction of an antigen-specific pleural effusion, guinea pigs were injected intrapleurally with anti-TGF-β1 or isotype control antibody. The following day, pleural exudates were removed, and the fluid volume and characteristics of the infiltrating cells were determined. Pleural fluid was analyzed for total interferon (IFN) and tumor necrosis factor (TNF) protein levels by using appropriate bioassays. RNA from pleural effusion cells was examined to determine TGF-β1, TNF-α, IFN-γ, and interleukin-8 mRNA levels by using real-time PCR. Proliferative responses of pleural effusion lymphocytes were examined in response to concanavalin A and purified protein derivative (PPD) in vitro. Treatment with anti-TGF-β1 resulted in decreased pleural fluid volume and decreased cell numbers in the pleural space along with an increased percentage of lymphocytes and a decreased percentage of neutrophils. The bioactive TNF protein levels in pleural fluid were increased in guinea pigs treated with anti-TGF-β1, while the bioactive IFN protein concentrations were not altered. Expression of TGF-β1 and TNF-α mRNA was significantly increased following TGF-β1 neutralization. Finally, PPD-induced proliferative responses of pleural cells from anti-TGF-β1-treated animals were significantly enhanced. Thus, TGF-β1 may be involved in the resolution of this local, mycobacterial antigen-specific inflammatory response.

Effect of Mycobacterium bovis BCG Vaccination on Mycobacterium-Specific Cellular Proliferation and Tumor Necrosis Factor Alpha Production from Distinct Guinea Pig Leukocyte Populations

ABSTRACT In this study, we focused on three leukocyte-rich guinea pig cell populations, bronchoalveolar lavage (BAL) cells, resident peritoneal cells (PC), and splenocytes (SPC). BAL cells, SPC, and PC were stimulated either with live attenuated Mycobacterium tuberculosis H37Ra or with live or heat-killed virulent M. tuberculosis H37Rv (multiplicity of infection of 1:100). Each cell population was determined to proliferate in response to heat-killed virulent H37Rv, whereas no measurable proliferative response could be detected upon stimulation with live mycobacteria. Additionally, this proliferative capacity (in SPC and PC populations) was significantly enhanced upon prior vaccination with Mycobacterium bovis BCG. Accordingly, in a parallel set of experiments we found a strong positive correlation between production of antigen-specific bioactive tumor necrosis factor alpha (TNF-α) and prior vaccination with BCG. A nonspecific stimulus, lipopolysaccharide, failed to induce this effect on BAL cells, SPC, and PC. These results showed that production of bioactive TNF-α from mycobacterium-stimulated guinea pig cell cultures positively correlates with the vaccination status of the host and with the virulence of the mycobacterial strain.