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

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 (N(48) amino acids 46 to 60; N(272), amino acids 272 to 286; and N(321) amino acid 321 to 335), and one on the membrane protein (M(196), amino acids 196 to 210). N(321), peptide induced the highest T cell response and was recognized by immune miniswine lymphocytes with haplotypes dd, aa , and cc. T lymphocytes from peptide N(321)-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 N(321) defines a functional T helper epitope eliciting T cells capable of collaborating with B cells specific for different proteins of TGEV.