Leukotrienes are not essential for the efficacy of a heterologous vaccine against Mycobacterium tuberculosis infection

Leukotrienes are reported to be potent proinflammatory mediators that play a role in the development of several inflammatory diseases such as asthma, rheumatoid arthritis and periodontal disease. Leukotrienes have also been associated with protection against infectious diseases. However, the role of leukotrienes in Mycobacterium tuberculosis infection is not understood. To answer this question, we studied the role of leukotrienes in the protective immune response conferred by prime-boost heterologous immunization against tuberculosis. We immunized BALB/c mice (4-11/group) with subcutaneous BCG vaccine (1 x 10(5) M. bovis BCG) (prime) followed by intramuscular DNA-HSP65 vaccine (100 µg) (boost). During the 30 days following the challenge, the animals were treated by gavage daily with MK-886 (5 mg·kg-1·day-1) to inhibit leukotriene synthesis. We showed that MK-886-treated mice were more susceptible to M. tuberculosis infection by counting the number of M. tuberculosis colony-forming units in lungs. The histopathological analysis showed an impaired influx of leukocytes to the lungs of MK-886-treated mice after infection, confirming the involvement of leukotrienes in the protective immune response against experimental tuberculosis. However, prime-boost-immunized mice treated with MK-886 remained protected after challenge with M. tuberculosis, suggesting that leukotrienes are not required for the protective effect elicited by immunization. Protection against M. tuberculosis challenge achieved by prime-boost immunization in the absence of leukotrienes was accompanied by an increase in IL-17 production in the lungs of these animals, as measured by ELISA. Therefore, these data suggest that the production of IL-17 in MK-886-treated, immunized mice could contribute to the generation of a protective immune response after infection with M. tuberculosis.

Th1 polarized response induced by intramuscular DNA-HSP65 immunization is preserved in experimental atherosclerosis

We previously reported that a DNA vaccine constructed with the heat shock protein (HSP65) gene from Mycobacterium leprae (DNA-HSP65) was protective and also therapeutic in experimental tuberculosis. By the intramuscular route, this vaccine elicited a predominant Th1 response that was consistent with its protective efficacy against tuberculosis. It has been suggested that the immune response to Hsp60/65 may be the link between exposure to microorganisms and increased cardiovascular risk. Additionally, the high cholesterol levels found in atherosclerosis could modulate host immunity. In this context, we evaluated if an atherogenic diet could modulate the immune response induced by the DNA-HSP65 vaccine. C57BL/6 mice (4-6 animals per group) were initially submitted to a protocol of atherosclerosis induction and then immunized by the intramuscular or intradermal route with 4 doses of 100 mug DNA-HSP65. On day 150 (15 days after the last immunization), the animals were sacrificed and antibodies and cytokines were determined. Vaccination by the intramuscular route induced high levels of anti-Hsp65 IgG2a antibodies, but not anti-Hsp65 IgG1 antibodies and a significant production of IL-6, IFN-g and IL-10, but not IL-5, indicating a Th1 profile. Immunization by the intradermal route triggered a mixed pattern (Th1/Th2) characterized by synthesis of anti-Hsp65 IgG2a and IgG1 antibodies and production of high levels of IL-5, IL-6, IL-10, and IFN-g. These results indicate that experimentally induced atherosclerosis did not affect the ability of DNA-HSP65 to induce a predominant Th1 response that is potentially protective against tuberculosis.

DNA Vaccine for the Prevention and Treatment fo Tuberculosis

Tradicional systems for developing drugs and vaccines are failing spectaculary to deliver the goods in the fight against tuberculosis (TB). The disease that afflicts the developing world defies the imagination in its scale. One third of the world's population - 2 billion people - is infected with Mycobacterium tuberculosis, and 16 million have active TB. Shockingly, TB hit an all-time high in 1999 with 8 million new cases - 95 per cent of them in developing countries - and 2 million deaths. The disease is spreading rapidly throughout the world. The toll is set to rise; AIDS activates the dormant form of the disease, while multidrug resistance is spreading across the planet. The last new drug for TB was introduced over thirty years ago and industry has been reluctant to invest in discovering new families of drugs because of the financial risks in investing in products destined largely for developing country markets. If global health is left to market forces, historians will remember this era as one in which humanity stood idly by while half the planet languished in sickness. Fortunately some researchers have realized this, and are driving forward new models for TB therapy and vaccine discovery. One of the latest sign of this trend is the development of a DNA vaccine for the prevention and treatment of TB by our research group. Over the last few years, some of our experiments in wich mycobacterial antigens were presented to the immune system, as of they were viral antigens (DNA vaccine), have had a significant impact on our understanding of protective immunity against tuberculosis. They also markedly enhanced the prospects for new vaccines. We now know that individual mycobacterial-protein antigens expressed from DNA-vaccine constructs can confer protection equal to that from live BCG vaccine in mice. A critical determinant of the outcome of immunization appears to be the degree to which antigen-specific cytotoxic T cells are generated by the immune response. We have demonstrated that DNA vaccination is an affective way of establishing long lasting cytotoxic T-cell memory and protection against tuberculosis. Moreover, our new preclinical work shows that DNA vaccines, initially designed to prevent infection, can also have a dramatic therapeutic action. In infected mice, the immune response can be caused to switch from one that is relatively inefficient and gives bacterial stasis to one that kills the bacteria, eliminating...

DNA encoding individual mycobacterial antigens protects mice against tuberculosis

Over the last few years, some of our experiments in which mycobacterial antigens were presented to the immune system as if they were viral antigens have had a significant impact on our understanding of protective immunity against tuberculosis. They have also markedly enhanced the prospects for new vaccines. We now know that individual mycobacterial protein antigens can confer protection equal to that from live BCG vaccine in mice. A critical determinant of the outcome of immunization appears to be the degree to which antigen-specific cytotoxic T cells are generated by the immune response. Our most recent studies indicate that DNA vaccination is an effective way to establish long-lasting cytotoxic T cell memory and protection against tuberculosis