H1N1 G4 swine influenza T cell epitope analysis in swine and human
vaccines and circulating strains uncovers potential risk to swine and
humans
Abstract
Pandemic influenza viruses may emerge from animal reservoirs and spread
among humans in the absence of cross-reactive antibodies in the human
population. Immune response to highly conserved T cell epitopes in
vaccines may still reduce morbidity and limit the spread of the new
virus even when cross-protective antibody responses are lacking. We used
an established epitope content prediction and comparison tool, EpiCC, to
assess the potential for emergent H1N1 G4 swine influenza A virus (G4)
to impact swine and human populations. We identified and computed the
total cross-conserved T cell epitope content in HA sequences of human
seasonal and experimental influenza vaccines, swine influenza vaccines
from Europe and the United States (US) against G4. The overall T cell
epitope content of US commercial swine vaccines was poorly conserved
with G4, with an average T cell epitope coverage of 35.7%. EpiCC scores
for the comparison between current human influenza vaccines and
circulating human influenza strains were also very low. In contrast, the
T cell epitope coverage of a recent European swine influenza vaccine
(HL03) was 65.8% against G4. Poor T cell epitope cross-conservation
between emergent G4 and swine and human influenza vaccines in the US may
enable G4 to spread in swine and spillover to human populations in the
absence of protective antibody response. One European influenza vaccine,
HL03, may protect against emergent G4. This study illustrates the use of
the EpiCC tool for prospective assessment of existing vaccine strains
against emergent viruses in swine and human populations.