Assessment of protective efficacy

To measure the ability of Ag85A DNA to confer protective immunity against mycobacterial challenge, we used several animal models. In mice Ag85A DNA

FIG. 3. Induction of cytotoxic T lymphocyte responses by vaccination with Ag85A DNA. BALB/c mice were injected with 100 ^g Ag85A DNA and spleen cells were prepared for antigen restimulation at 1 year after injection. Pools of three spleens per group were restimulated with peptide (corresponding to amino acids 61—80 of Ag85A) and tested for lytic activity against P815 target cells that were untreated (open circles), pulsed with 61—80 peptide (solid circles), pulsed with 141—160 peptide (solid squares) or transfected with Ag85A (solid triangles). Data shown are per cent specific lysis for effector:target ratios of 4 : 1,20 : 1 and 100 : 1.

Effector: Target

FIG. 3. Induction of cytotoxic T lymphocyte responses by vaccination with Ag85A DNA. BALB/c mice were injected with 100 ^g Ag85A DNA and spleen cells were prepared for antigen restimulation at 1 year after injection. Pools of three spleens per group were restimulated with peptide (corresponding to amino acids 61—80 of Ag85A) and tested for lytic activity against P815 target cells that were untreated (open circles), pulsed with 61—80 peptide (solid circles), pulsed with 141—160 peptide (solid squares) or transfected with Ag85A (solid triangles). Data shown are per cent specific lysis for effector:target ratios of 4 : 1,20 : 1 and 100 : 1.

was protective against systemic challenge with a high dose of BCG, as well as against a low dose aerosol challenge with M. tuberculosis (Huygen et al 1996). The level of protection achieved was comparable to that induced by BCG vaccine. In addition, mice were protected from a low dose aerosol challenge with a highly virulent human clinical isolate of M. tuberculosis that grows to high levels in the lungs of unprotected mice (-107 colony-forming units). Finally, guinea pigs were protected from a low dose aerosol challenge with M. tuberculosis, as indicated by improved lung pathology and by decreased morbidity (weight loss) and mortality compared to controls in a long-term study (31 weeks; Baldwin et al 1998). Therefore, by several criteria, Ag85A DNA was shown to confer protective immunity against mycobacterial disease in animal models.

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