Inactivated Split MERS-CoV Antigen Prevents Lethal Middle East Respiratory Syndrome Coronavirus Infections in Mice

Middle East respiratory syndrome coronavirus (MERS-CoV) causes fatal infections, with about 36% mortality in humans, and is endemic to the Middle East. MERS-CoV uses human dipeptidyl peptidase 4 (hDPP4) as a receptor for infection. Despite continued research efforts, no licensed vaccine is available for protection against this disease in humans. Therefore, this study sought to develop an inactivated fragmented MERS-CoV vaccine grown in Vero cells in an hDPP4-transgenic mouse model. Two-dose immunisation in mice with 15, 20, or 25 μg of spike proteins of inactivated split MERS-CoV antigens induced neutralising antibodies, with titres ranging from NT 80 to 1280. In addition, all immunised mice were completely protected, with no virus detection in tissues, weight loss, or mortality. The immunised splenocytes produced more cytokines that stimulate immune response (IFN-γ and TNF-α) than those that regulate it (IL-4 and IL-10). Taken together, the inactivated fragmented MERS-CoV vaccine is effective for the protection of mice against lethal MERS-CoV. Thus, the inactivated fragmented MERS-CoV vaccine warrants further testing in other hosts.