Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe respiratory disease in humans with a case fatality rate of over 39%, and poses a considerable threat to public health. A lack of approved vaccine or drugs currently constitutes a roadblock in controlling disease outbreak and spread. In this study, we generated MERS-CoV VLPs using the baculovirus expression system. Electron microscopy and immunoelectron microscopy results demonstrate that MERS-CoV VLPs are structurally similar to the native virus. Rhesus macaques inoculated with MERS-CoV VLPs and Alum adjuvant induced virus-neutralizing antibodies titers up to 1:40 and induced specific IgG antibodies against the receptor binding domain (RBD), with endpoint titers reaching 1:1,280. MERS-CoV VLPs also elicited T-helper 1 cell (Th1)-mediated immunity, as measured by ELISpot. These data demonstrate that MERS-CoV VLPs have excellent immunogenicity in rhesus macaques, and represent a promising vaccine candidate.

Middle East Respiratory Syndrome (MERS) is a highly lethal pulmonary infection caused by a coronavirus (CoV), MERS-CoV. With the continuing spread of MERS-CoV, prophylactic and therapeutic treatments are urgently needed. In this study, we prepared purified equine F(ab') from horses immunized with MERS-CoV virus-like particles (VLPs) expressing MERS-CoV S, M and E proteins. Both IgG and F(ab') efficiently neutralized MERS-CoV replication in tissue culture. Passive transfer of equine immune antibodies significantly reduced virus titers and accelerated virus clearance from the lungs of MERS-CoV infected mice. Our data show that horses immunized with MERS-CoV VLPs can serve as a primary source of protective F(ab') for potential use in the prophylactic or therapeutic treatment of exposed or infected patients.

BackgroundMarburg virus (MARV) causes severe haemorrhagic fever in humans and nonhuman primates and has a high mortality rate. However, effective drugs or licensed vaccines are not currently available to control the outbreak and spread of this disease.MethodsIn this study, we generated MARV virus-like particles (VLPs) by co-expressing the glycoprotein (GP) and matrix protein (VP40) using the baculovirus expression system. MARV VLPs and three adjuvants, Poria cocos polysaccharide (PCP-II), poly(I:C) and aluminium hydroxide, were evaluated after intramuscular vaccination in mice.ResultsMurine studies demonstrated that vaccination with the MARV VLPs induce neutralizing antibodies and cellar immune responses. MARV VLPs and the PCP-II adjuvant group resulted in high titres of MARV-specific antibodies, activated relatively higher numbers of B cells and T cells in peripheral blood mononuclear cells (PBMCs), and induced greater cytokine secretion from splenocytes than the other adjuvants.ConclusionMARV VLPs with the PCP-II adjuvant may constitute an effective vaccination and PCP-II should be further investigated as a novel adjuvant.