Induction of neutralising antibodies and cellular immune responses against SARS coronavirus by recombinant measles viruses

Live attenuated recombinant measles viruses (rMV) expressing a codon-optimised spike glycoprotein (S) or nucleocapsid protein (N) of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) were generated (rMV-S and rMV-N). Both recombinant viruses stably expressed the corresponding SARS-CoV proteins, grew to similar end titres as the parental strain and induced high antibody titres against MV and the vectored SARS-CoV antigens (S and N) in transgenic mice susceptible to measles infection. The antibodies induced by rMV-S had a high neutralising effect on SARS-CoV as well as on MV. Moreover, significant N-specific cellular immune responses were measured by IFN-γ ELISPOT assays. The pre-existence of anti-MV antibodies induced by the initial immunisation dose did not inhibit boost of anti-S and anti-N antibodies. Immunisations comprising a mixture of rMV-S and rMV-N induced immune responses similar in magnitude to that of vaccine components administered separately. These data support the suitability of MV as a bivalent candidate vaccine vector against MV and emerging viruses such as SARS-CoV.