Description
MERS is a viral respiratory infection caused by the newly identified MERS-coronavirus (MERS-CoV), a betacoronavirus derived from bats. MERS can range from asymptomatic disease to severe pneumonia leading to the acute respiratory distress syndrome. As of Jan 2015, MERS caused more than 900 human infections with ~40% mortality. MERS-CoV cases have been reported in several Middle Eastern countries, Bangladesh, the United Kingdom, and the United States. Early research suggested the virus is related to one found in the bats and in dromedary camels, as 90-100% camels have antibodies to the MERS-CoV spike protein. Human or animal's diagnostic serology is based upon PCR or ELISA or antibody neutralization tests. There are no vaccines available for MERS.
MERS-CoV, a +RNA virus from Betacoronavirus lineage C, is more closely related to the bat coronaviruses HKU4 and HKU5 (lineage 2C, ~90% identity) than it is to SARS-CoV (lineage 2B). Serologic analysis of CoVs is challenging because of crossreactivity between CoVs infecting the same host and the broad distribution of CoVs in diverse mammalian species. Many small animals (mice, hamsters and ferrets) lack the functional MERSCoV receptor (DPP4) and are not susceptible to infection.
MERS produces structural proteins (Spike, S; Envelope (E), Membrane (M), and Nucleocapsid protein (NP). S protein (1353-aa) has 2 well defined domains: S1 (1-751aa) and S2 (752-1353aa). During viral entry, the S protein is cleaved into S1 and S2 subunits by host cell derived proteases. S1 subunit mediates virus binding to cells expressing DPP4 through its receptor-binding domain (RBD, 367-606 aa) region and an S2 subunit that mediates virus-cell membrane fusion. A truncated RBD domain (377-588) protein binds efficiently to DPP4. NP protein is required for RNA synthesis, and has RNA chaperone activity. The presence of MERS viral antibodies (N, E and S, and S1) have been used to detect MERS infection