Antibodies against MERS coronavirus in dromedary camels, United Arab Emirates, 2003 and 2013

Abstract

Middle East respiratory syndrome coronavirus (MERS-CoV) has caused an ongoing outbreak of severe acute respiratory tract infection in humans in the Arabian Peninsula since 2012. Dromedary camels have been implicated as possible viral reservoirs. We used serologic assays to analyze 651 dromedary camel serum samples from the United Arab Emirates; 151 of 651 samples were obtained in 2003, well before onset of the current epidemic, and 500 serum samples were obtained in 2013. Recombinant spike protein-specific immunofluorescence and virus neutralization tests enabled clear discrimination between MERS-CoV and bovine CoV infections. Most (632/651, 97.1%) camels had antibodies against MERS-CoV. This result included all 151 serum samples obtained in 2003. Most (389/651, 59.8%) serum samples had MERS-CoV-neutralizing antibody titers >1,280. Dromedary camels from the United Arab Emirates were infected at high rates with MERS-CoV or a closely related, probably conspecific, virus long before the first human MERS cases.

Keywords: MERS; MERS-CoV; Middle East respiratory syndrome; Middle East respiratory syndrome coronavirus; United Arab Emirates; antibodies; camels; coronavirus; dromedary camels; serologic analysis; viruses.

Figure

Immunofluorescence and microarray reactivity patterns for antibodies (SF74, H40, H97, and S11) against Middle East respiratory syndrome coronavirus (MERS-CoV) in serum samples from camels, United Arab Emirates, 2013. A) Serum samples tested against overexpressed MERS-CoV spike protein (MERS-S), overexpressed human CoV-OC43 spike protein (OC43-S), and Vero cells infected with MERS-CoV (MERS-V). Fluorescence intensities were evaluated as follows: –, negative; +, weakly reactive; ++, reactive; +++, strongly reactive. Scale bar indicates 20 μm. B) Relative fluorescence units (RFU) were determined for the same serum samples by microarray using S1 domains of MERS-CoV and human CoV-OC43.