Cross‐typic specificity and immunotherapeutic potential of a human HPV16 E7‐specific CTL line

Abstract

Cervical cancer (CaCx) is strongly associated with human papillomavirus (HPV) infection, particularly HPV types 16 and 18. The constitutive expression of HPV E6 and E7 proteins in CaCx makes them attractive targets for CTL based immunotherapy. However cervical carcinomas may have features, e.g., antigen processing defects, that limit the effectiveness of HPV specific CTL. Furthermore most vaccine development has concentrated on HPV type 16, and it is not clear whether such vaccines could induce CTL able to cross-react on related oncogenic HPV types, e.g., HPV31 and 52. To investigate these potentially important parameters in vitro, we used a CTL (D4) specific for HPV16 E7 11-20 . D4 was able to kill a variety of HPV16؉ CaCx cell lines including those with suspected (CaSki) or known antigen processing defects (C33A), and with low HPV DNA copy number (SiHa). D4 was also able to cross react on a related peptide from HPV52 E7 but not HPV31 E7. Further analysis suggested that D4 cross reactivity against related peptides was influenced both by TCR contact residues and a certain threshold for peptide binding. The HPV cross-reactivity was confirmed at the whole protein level as D4 was also able to recognize the endogenously processed forms of HPV16 and 52 E7 but not 31 E7. These results suggest that HPV16 E7 11-20 would be a useful epitope for immunotherapy in both HPV 16 and 52 tumours. Despite this, it is difficult to generate these CTL in response to vaccination, emphasizing the need for definition of novel epitopes and more efficient vaccination strategies.Key words: HPV; CTL; cervical cancer; immunotherapy; cross-reactivity Cervical cancer (CaCx) is the second most common cause of cancer in women world wide and with premalignant cervical intraepithelial neoplasia (CIN3) is associated with HPV infection. In developing countries where 80% of cases occur, this is the principal female cancer. 1 The DNA of HPVs, particularly 16 and 18, are found in Ͼ99% of CaCx patients. 2 It is the E6 and E7 proteins, which are consistently retained and expressed in cervical tumor cells, that give the virus its transforming properties. 3,4 HPVs are defined as low and high risk, high-risk types being associated with invasive cervical cancer, while low risk types are associated with warts. There are 11 HPV types that are consistently classified as high-risk types: 16,18,31,33,35, 39, 45, 51, 52, 56 and 58. These types are further divided into classes: type A (16, 31, 33, 35, 52 and 58), C (18, 39 and 45) and D (51 and 56).HPV type-specific prevalence varies geographically. Worldwide, types 16 and 18 dominate but in other non-Caucasian populations, 31, 52 and 58 dominate. The infection rate with each HPV type varies from country to country, i.e., HPV16 is found in 43.9% of cases in the Philippines and 72.4% in Morocco. According to Mûnoz et al., 95% of all infections were caused by 8 types: 16, 18, 45, 31, 33, 52, 58 and 35. They suggest that vaccination against the 5 most common types could prevent 90% of cases of CaCx. 5 The geographi...

Detection of human papillomavirus type 18 E6 and E7‐specific CD4+ T‐helper 1 immunity in relation to health versus disease

“…In fact, several groups have found examples of such cross-reactivity. 17,25,26 It is presently unclear whether these examples constitute exceptions or reflect a more common feature. Because the extent of immunological cross-reactivity between HPV types within clades has important consequences for both the interpretation of immunological data and the design of vaccines that are to protect against a broad array of HPV-types, this issue is currently investigated in more detail in our laboratory.…”

‘1-8 interferon inducible gene family’: putative colon carcinoma-associated antigens

“…Antigens that are uniquely expressed in tumours (Luftl et al, 2004); antigens derived from differentiation markers (Panelli et al, 2000); antigens arise from mutations that are common in tumours (McArdle et al, 2000); antigens from a viral source (Youde et al, 2004); and selfantigens that are overexpressed in tumours (Bar-Haim et al, 2004). In the latter category, although strong immune reactions against this type of antigens might result in the destruction of normal tissues, experience with peptide immunisation has not demonstrated high toxicity in humans and animals (Gross et al, 2004).…”

HPV16 E629‐38‐specific T cells kill cervical carcinoma cells despite partial evasion of T‐cell effector function

“…17 Generation of the SiHa-A2 transfectant expressing HLA-A*0201 has been previously described. 13 CaSki was grown in RPMI/FCS, SiHa cells were grown in DMEM/FCS (DMEM with 10% FCS, 2 mM glutamine, 100 lg/ml streptomycin, 100 U/ml penicillin, 25 mM Hepes and 1% nonessential amino acids). SiHa-A2 cells were grown in DMEM/FCS with the addition of 400 lg/ml G418.…”

“…We proposed that this was due to defects in antigen processing, because we showed that these cell lines had low or undetectable levels of several intracellular proteins involved in the MHC class I antigen processing pathway. 12 However, we subsequently demonstrated that CTL against a different peptide epitope, HPV16 E7 [11][12][13][14][15][16][17][18][19][20] was capable of killing the same carcinoma cell lines. 13 This suggested that the defects in antigen processing in the carcinoma cell lines were not global, but perhaps might be specific for the E6 [29][30][31][32][33][34][35][36][37][38] epitope.…”