A Transmissible Gastroenteritis Coronavirus Nucleoprotein Epitope Elicits T Helper Cells That Collaborate in the in Vitro Antibody Synthesis to the Three Major Structural Viral Proteins

Abstract

Four strong T cell epitopes have been identified studying the blastogenic response of lymphocytes from haplotype-defined transmissible gastroenteritis virus (TGEV) immune miniswine to sixty-one 15-mer synthetic peptides. Three of these epitopes are located on the nucleoprotein (N₄₈ amino acids 46 to 60; N₂₇₂, amino acids 272 to 286; and N₃₂₁ amino acid 321 to 335), and one on the membrane protein (M₁₉₆, amino acids 196 to 210). N₃₂₁, peptide induced the highest T cell response and was recognized by immune miniswine lymphocytes with haplotypes dd, aa , and cc. T lymphocytes from peptide N₃₂₁-immune miniswine reconstituted the in vitro synthesis of TGEV-specific antibodies by complementing CD4^- TGEV-immune cells. This response was directed at least against the three major structural proteins. The synthesized antibodies specific for S protein preferentially recognized discontinous epitopes and neutralized TGEV infectivity. These results show that peptide N₃₂₁ defines a functional T helper epitope eliciting T cells capable of collaborating with B cells specific for different proteins of TGEV.