Cytolytic T lymphocyte and antibody responses to synthetic peptides of influenza virus hemagglutinin.

Two peptides corresponding to HA1(181-204) and HA2(103-123) of the A/Japan/305/57 influenza virus hemagglutinin (HA) were chemically synthesized by solid-phase methods and were tested for their ability to generate murine secondary anti-influenza cytolytic T lymphocytes (CTL) in vitro and to bind monoclonal anti-HA antibodies. Peptide HA1(181-204) could only generate CTL in the presence of helper factors contained in supernatant fluids from either Concanavalin A-stimulated mouse spleen cultures or WEHI-3 cells grown in vitro. Peptide HA2(103-123) stimulated the induction of anti-influenza CTL independent of helper factors, but the stimulation was also greatly increased if helper factors were added. A 10-fold molar excess of peptide HA2(103-123) was required to obtain optimal CTL activation over the quantities required in the HA1(181-204) system. This molar ratio remained unchanged, even in the presence of helper factors. Induction of influenza-specific CTL was antigen-dependent in both systems, even though some killing of noninfected target cells was also occasionally observed. Our results suggest that synthetic peptides can be recognized as antigenic determinants in the generation of H-2-restricted anti-viral CTL capable of killing appropriately infected target cells. The inability of peptide HA1(181-204) to generate sufficient help for CTL development suggests that certain regions of the HA can be recognized by CTL precursors, but not by all of the required helper cells. Peptide HA1(181-204) also reacted with three monoclonal anti-HA antibodies as well as mouse anti-influenza (A/Japan/305/57) immune sera. This antibody reactivity suggests the possibility of a shared antigenic epitope or region between T and B cells, and therefore provides new insight in our understanding of viral antigenicity.