Immunization with Chlamydia psittaci plasmid-encoded protein CPSIT_p7 induces partial protective immunity against chlamydia lung infection in mice

• Published in: Immunologic research 2018-08, Vol.66 (4), p.471-479
• Main Authors: Tan, Yuan, Li, Yumeng, Zhang, Yang, Yu, Jian, Wen, Yating, Wang, Chuan, Xu, Man, Chen, Qian, Lu, Chunxue, Wu, Yimou
• Format: Article
• Language: English
• Subjects: Adjuvants; Adoptive transfer; Allergology; Animals; Antigens, Bacterial - genetics; Antigens, Bacterial - immunology; Bacterial Load; Bacterial Vaccines - immunology; Biomedical and Life Sciences; Biomedicine; CD4 antigen; CD4-Positive T-Lymphocytes - immunology; Chlamydia; Chlamydia psittaci; Chlamydophila psittaci - physiology; Coding; Female; Immune response (cell-mediated); Immune response (humoral); Immunity, Cellular; Immunization; Immunology; Interferon; Interferon-gamma - blood; Internal Medicine; Lung - microbiology; Lung - pathology; Lungs; Lymphocytes; Lymphocytes T; Medicine/Public Health; Mice; Mice, Inbred BALB C; Neutralization; Original Article; p7 Protein; Plasmids - genetics; Proteins; Psittacosis - immunology; Spleen; Vaccination; Vaccines, Synthetic - immunology; γ-Interferon
• ISSN: 0257-277X; 1559-0755
• DOI: 10.1007/s12026-018-9018-3

The present study evaluated the immune-protective efficacy of the Chlamydia psittaci ( C. psittaci ) plasmid protein CPSIT_p7 and analyzed the potential mechanisms of this protection. The current study used recombinant CPSIT_p7 protein with Freund’s complete adjuvant and Freund’s incomplete adjuvant to vaccinate BALB/c mice. Adjuvants alone or PBS formulated with the same adjuvants was used as negative controls. Mice were intranasally challenged with 10 5 inclusion-forming units (IFU) of C. psittaci . We found that CPSIT_p7 vaccination significantly decreased the mouse lung chlamydial load, interferon-γ (IFN-γ) level, and pathological injury. This protection correlated well with specific humoral and cellular immune responses against C. psittaci . In vitro or in vivo neutralization of C. psittaci with sera harvested from immunized mice did not reduce the number of recoverable C. psittaci in the infected lungs, but CD4 + spleen cells collected from CPSIT_p7-immunized mice significantly decreased the chlamydial load via adoptive transfer to native mice. These results reveal that the protection conferred by CPSIT_p7 is dependent on CD4 + T cells.