HPV18 E1-antigen specific CD8+ T cells show cross-reactivity against cells expressing E1 from HPV16, 31, 33 and 53.

Abstract

Abstract CD8+ mediated immune response plays a major role in the clearance of Human Papillomavirus (HPV) infected cells. Although HPV vaccines prevent HPV infections through humoral response, they do not protect against established infections and its cross protection is limited. In the HPV infection, the expression of E1 helicase during viral replication makes it a potential immunological target. The E1 protein is one of the most conserved proteins among papillomaviruses. We demonstrate in previous work, that immunization of HPV type 18 E1 protein plus α-GalactosylCeramide (α-GalCer) elicited CD8 T cell-immune response, able to eliminate tumor cells expressing HPV18 E1 protein. For this study, we analyzed the amino acids sequence of E1carboxi-terminal (CT) domains from HPV18, 16, 31, 33 and 53, using Rankpep and Clustal software to determine the number of conserved peptides among E1 proteins. These sequences share 20 predicted peptides. We cloned E1-CT domains of HPV16, 31, 33 and 53, and its expression in B16-F0 cells was determine. We show that CD8 T cells from mice immunized with HPV18 E1 protein plus α-GalCer, are actively cytotoxic in co-culture with B16-F0 cells expressing different E1-CT proteins in comparison with unimmunized mice, showing a cross-reactivity. Cytotoxicity activity was evaluated by detection of CD107a and CD107b on the CD8 T cells surface as part of cytotoxic granule exocytosis, through flow cytometry. Ongoing experiments will examine if mice immunized with HPV18 E1 protein plus α-GalCer are able to eliminate tumors cells expressing different E1-CT proteins in a mouse model. The characterization of new immunological targets against HPV, could help to develop new strategies to clearance HPV established infections.