Identification of Novel CD4+ T Helper Peptide Epitopes from HSV Glycoprotein (gD) that Confer Protective Immunity

Abstract

Abstract: : Purpose:The purpose is to identify CD4+ T cells epitopes based on the amino acid sequences of HSV-1 gD that are capable of eliciting protective immunity. Methods:HSV-1 gD was analyzed by the novel T cell epitope prediction algorithm based on TEPITOPE®. Mice were immunized and T cell immunogenicity of each predicted peptide was determined by proliferation assays, cytokines secretion, and CTL assays. The protective efficacy of the identified epitope peptides against an ocular HSV-1 infection was evaluated in mice. Results:We identified 12 regions bearing potential CD4+ T-cell epitopes, each 27 to 34 amino acids in length, within HSV-1 gD. These peptides were used in binding assays with 13 different human leukocyte antigen class II (HLA-DR) molecules. Peptides with high binding affinity were selected. Immunogenicity studies of the corresponding medium-sized peptides emulsified in Montanide’s ISA-720 (a human compatible adjuvant), confirmed all previously known gD epitopes and additionally revealed four new region-bearing-epitopes that elicited potent T-cell responses in mice of diverse MHC backgrounds. The T-cells induced were defined as a Th-1 subset by the selective expansion of CD4+ T-cells and stimulation of IL-2 and IFN-g, crucial cytokines in the elimination of the virus. Immunization with some of these peptides generated CD4+ T-cells that were biologically active against the viral expressed gD, as presented by HSV-1-infected bone marrow derived-dendritic cells. In addition, virus-primed CD4+ T-cells derived from mice infected with HSV-1 recognized most of the selected peptides. Importantly, immunization of H-2d mice with the newly identified peptide epitopes induced a CD4+ T-cell-dependent protective immunity against a lethal ocular HSV-1 infection. Conclusions:(1) The use of the TEPITOPE® program to select universal epitopes allowed rapid screening of epitopes capable of inducing a Th1 response (2) Immunization of mice with corresponding peptide epitopes produced in vivo T-cells dependent protective immunity. (3) The peptide epitopes, particularly the new ones described, are potentially important components of an effective therapeutic or prophylactic subunit vaccine strategy against herpes.

Keywords: antigen presentation/processing • immunomodulation/immunoregulation • herpes simplex virus