title: Suppression of antitumour protective cytotoxic T lymphocyte responses to a human papillomavirus 16 E7 DNA vaccine by coinjection of interleukin-12 complementary DNA: involvement of nitric oxide in immune suppression.
abstract: Interleukin-12 (IL-12) has been shown to enhance cellular immunity in vitro and in vivo. The beneficial roles of IL-12 as a DNA vaccine adjuvant have been commonly observed. Here the impact of IL-12 complementary DNA (cDNA) as an adjuvant for a human papillomavirus (HPV) type 16 E7 DNA vaccine is investigated in a mouse tumour model. Coinjection of E7 DNA vaccine with IL-12 cDNA completely suppressed antigen-specific cytotoxic T-lymphocyte (CTL) responses, leading to a complete loss of antitumour protection from a tumour cell challenge. In addition, antigen-specific antibody and T helper cell proliferative responses were also suppressed by IL-12 cDNA coinjection. This inhibition was observed over different IL-12 cDNA doses. Furthermore, separate leg injections of IL-12 and E7 cDNAs suppressed antigen-specific CTL and tumour protective responses, but not antibody and T helper cell proliferative responses, suggesting different pathways for suppression of these two separate responses. Further knockout animal studies demonstrated that interferon-gamma and nitric oxide are not directly associated with suppression of antigen-specific antibody responses by IL-12 cDNA coinjection. However, nitric oxide was found to be involved in suppression of antigen-specific CTL and tumour protective responses by IL-12 cDNA coinjection. These data suggest that coinjection of IL-12 cDNA results in suppression of E7-specific CTL responses through nitric oxide, leading to a loss of antitumour resistance in this DNA vaccine model. This study further shows that the adjuvant effect of IL-12 is dependent on the antigen types tested.
authors.affiliation: Department of Microbiology, School of Medicine, Catholic University of Daegu, Namgu, Daegu, Korea. jsin1964@hanmail.net
authors.forename: Jeong-Im
authors.initials: JI
authors.lastname: Sin
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000818:Animals; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D018076:DNA, Complementary / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D005260:Female; D052162:Human papillomavirus 16 / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007111:Immunity, Cellular; D056724:Immunity, Humoral; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D017942:Nitric Acid / Q000378:metabolism; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000276:immunology*; D050725:Papillomavirus E7 Proteins; D030361:Papillomavirus Infections / Q000276:immunology / Q000517:prevention & control*; D053918:Papillomavirus Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D002583:Uterine Cervical Neoplasms / Q000276:immunology / Q000517:prevention & control*; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D018076:DNA, Complementary; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D053918:Papillomavirus Vaccines; D019444:Vaccines, DNA; C059731:oncogene protein E7, Human papillomavirus type 16; D018664:Interleukin-12; D017942:Nitric Acid; D007371:Interferon-gamma