“Natural” presentation of human papillomavirus type‐16 E7 protein to immunocompetent mice results in antigen‐specific sensitization or sustained unresponsiveness

Abstract

We have used a mouse model that utilizes the exclusively epithelial nature of human papillomavirus (HPV) infections to investigate the in vivo immune response to the E7 protein of human papillomavirus type-16. A keratinocyte cell line expressing E7 protein has been established and grafted onto syngeneic mice using a transplantation technique that permits the reformation of a differentiated epithelium on a granulation tissue bed. In this way viral antigens may be presented to the immune system in a way comparable to natural infection. A delayed-type hypersensitivity (DTH) response was studied post grafting by intradermal challenge with recombinant E7 protein. A significant response to E7 has been demonstrated in this way; however, priming with a low amount of HPV-16 E7 antigen induces immunological unresponsiveness, as measured by a loss of DTH reactivity to the protein, and persistence of keratinocytes expressing E7. Lymphocytes from mice exhibiting DTH reactivity have been shown to proliferate when stimulated with purified recombinant E7 protein in vitro, while immunoperoxidase staining of tissue from the sites of immunologically-induced inflammation has defined the cell infiltrate to be phenotypically characteristic of DTH. The observations reported here have important implications for vaccine strategy.

T-cell responses to human papillomavirus type 16 among women with different grades of cervical neoplasia

“…In invasive carcinoma, there will also be an increase in the amount of infected tissue and subsequently viral load. Indeed, HPV16 responses have been shown to be dependent on antigen dose in experiments using a murine model in which viral antigen is expressed in keratinocytes and mimics the natural route of infection (Chambers et al, 1994). A surprisingly high frequency of HPV-specific CD4 þ T-cell responses in women with cervical carcinoma compared to those with high-grade CIN has also been observed in a similar study published recently by de Jong et al (2004).…”

Split tolerance to a viral antigen expressed in thymic epithelium and keratinocytes

“…The total level of expression of E7 in the skin may therefore be a major determinant of whether the immune system responds to or ignores the autoantigen. This has been observed as a dose-dependent induction of E7-specific DTH following grafting of E7-transfected keratinocytes [28]. Despite apparently normal K b -specific CTL responses in vitro in the K14.K b model referred to above, K b -positive skin allografts were not rejected from the K4.K b -transgenic animals [7], although they were rejected from non-transgenic littermate controls.…”

Radiation-enhanced expression of E6/E7 transforming oncogenes of human papillomavirus-16 in human cervical carcinoma

“…31,32 Chambers et al also have shown that high or low concentrations of viral oncoproteins can play a crucial role in determining successful induction of delayed-type hypersensitivity or unresponsiveness in mouse models. 33 Finally, Alexander et al have reported activation of specific cytolytic T-lymphocytes in patients with advanced cervical carcinoma after stimulation with a synthetic HPV-16 E7 epitope. 34 However, although radiation therapy plays a major role in the treatment of cervical carcinoma, adequate documentation of the effects of irradiation on the expression of HPV viral antigens or other surface antigens such as MHC is lacking.…”