Recombinant Adenovirus Delivery of Calreticulin-ESAT-6 Produces an Antigen-Specific Immune Response but no Protection Against a Mycobacterium Tuberculosis Challenge

• Published in: Scandinavian journal of immunology 2012-03, Vol.75 (3), p.259-265
• Main Authors: Esparza-González, S. C., Troy, A., Troudt, J., Loera-Arias, M. J., Villatoro-Hernández, J., Torres-López, E., Ancer-Rodríguez, J., Gutiérrez-Puente, Y., Muñoz-Maldonado, G., Saucedo-Cárdenas, O., Montes-de-Oca-Luna, R., Izzo, A.
• Format: Article
• Language: English
• Subjects: Adenoviridae - genetics; Adenoviridae - metabolism; Adenovirus; Adjuvants; Aerosols; Animal models; Animals; Antigens, Bacterial - biosynthesis; Antigens, Bacterial - genetics; Antigens, Bacterial - immunology; Bacterial Proteins - biosynthesis; Bacterial Proteins - genetics; Bacterial Proteins - immunology; BCG; Calreticulin; Calreticulin - biosynthesis; Calreticulin - genetics; Calreticulin - immunology; Colony Count, Microbial; Cytokines; ESAT-6 antigen; Female; Fusion protein; gamma -Interferon; Genetic Vectors - genetics; Genetic Vectors - metabolism; Immune response; Immune response (cell-mediated); Immunization; Infection; Interferon-gamma - immunology; Lung - microbiology; Mice; Mice, Inbred C57BL; Mycobacterium bovis; Mycobacterium tuberculosis; Mycobacterium tuberculosis - immunology; Recombinant Fusion Proteins - administration & dosage; Recombinant Fusion Proteins - biosynthesis; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - immunology; Specific Pathogen-Free Organisms; Spleen - microbiology; Tuberculosis; Tuberculosis - immunology; Tuberculosis - prevention & control; Tumor necrosis factor- alpha; Tumor Necrosis Factor-alpha - immunology; Vaccines; Virulence
• ISSN: 0300-9475; 1365-3083
• DOI: 10.1111/j.1365-3083.2011.02655.x

Bacillus Calmette–Guerin (BCG) has failed to efficaciously control the worldwide spread of the disease. New vaccine development targets virulence antigens of Mycobacterium tuberculosis that are deleted in Mycobacterium bovis BCG. Immunization with ESAT‐6 and CFP10 provides protection against M. tuberculosis in a murine infection model. Further, previous studies have shown that calreticulin increases the cell‐mediated immune responses to antigens. Therefore, to test whether calreticulin enhances the immune response against M. tuberculosis antigens, we fused ESAT‐6 to calreticulin and constructed a recombinant replication‐deficient adenovirus to express the resulting fusion protein (AdCRT–ESAT‐6). The adjuvant effect of calreticulin was assayed by measuring cytokine responses specific to ESAT‐6. Recombinant adenovirus expressing the fusion protein produced higher levels of interferon‐γ and tumour necrosis factor‐α in response to ESAT‐6. This immune response was not improved by the addition of CFP‐10 to the CRT‐ESAT‐6 fusion protein (AdCRT–ESAT‐6–CFP10). Mice immunized with these recombinant adenoviruses did not decrease the mycobacterial burden after low‐dose aerosol infection with M. tuberculosis. We conclude that calreticulin can be used as an adjuvant to enhance the immune response against mycobacterial antigens, but it is not enough to protect against tuberculosis.