Mycobacterium tuberculosis is the causative agent of a pulmonary epidemic that is estimated to infect one-third of the worlds population and that has an increased incidence of multidrug resistance. The evaluation of new chemical entities against M. tuberculosis is hampered by the lack of biological tools to help predict efficacy, from early drug development to clinical trials. As the rat is the animal species of choice in the pharmaceutical industry, we have developed a rat model of acute and chronic phases of M. tuberculosis infection for drug efficacy testing. In this model, we have evaluated the impact of tuberculosis drugs on T cell response using the enzyme-linked immunospot assay methodology. Infected rats treated with isoniazid (INH) or rifampin (RIF) responded to therapy, the potency of which was comparable to that seen in the mouse. Peripheral blood mononuclear cells from infected rats produced gamma interferon (IFN-?) in response to RD-1 antigens, such as the 6-kDa early secretory antigen target (ESAT-6) and the 10-kDa culture filtrate protein (CFP-10). A decrease in IFN-? spot-forming cells (SFCs) was consistently observed in response to drug treatment. In both the acute- and chronic-phase models, the T cell response was more sensitive to ESAT-6 than to CFP-10. The SFC count in response to ESAT-6 appears to be an indicator of bacterial killing in the rat. Collectively, our data suggest that the ESAT-6 response could be used as a potential surrogate of drug efficacy in the rat and that such a readout could help shorten drug testing during preclinical development.
Despite the availability of many animal models for tuberculosis (TB) research, there still exists a need for better understanding of the quiescent stage of disease observed in many humans. Here, we explored the use of the Wistar rat model for the study of protective immunity and control of Mycobacterium tuberculosis (Mtb) infection.
Enterovirus 71 (EV71) is the major causative agent of hand, foot, and mouth disease (HFMD) in young children and has been consistently associated with the most severe complications of the disease, including central nervous system inflammation and pulmonary edema. Increasing frequency and amplitude of EV71 outbreaks have raised awareness and concerns worldwide. Previous reports proposed that overwhelming virus replication combined with the induction of massive proinflammatory cytokines is responsible for the pathogenicity of EV71. Specifically, elevated interleukin-6 (IL-6) levels were observed consistently in patients and strongly correlated with disease severity. In this study, we show in the neonate mouse model that sustained high levels of IL-6 produced upon EV71 infection lead to severe tissue damage and eventually death of the animals. Administration of anti-IL-6 neutralizing antibodies after the onset of the clinical symptoms successfully improved the survival rates and clinical scores of the infected hosts. Compared to untreated infected controls, anti-IL-6-treated mice displayed reduced tissue damage, absence of splenic atrophy, and increased immune cell activation. In addition, markedly elevated systemic levels of IL-10 were measured in the protected animals. Furthermore, there was no significant difference in virus titers between anti-IL-6-treated mice and untreated mice, indicating that the anti-IL-6 antibody-mediated protection is independent of the virus load. Our findings thus demonstrate that IL-6 plays a major role in EV71-induced immunopathogenesis. As there is still neither vaccine nor treatment available against EV71, anti-IL-6 antibody treatment represents a potential therapeutic approach to providing protection from the most severe complications of the disease.
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