Middle East Respiratory Syndrome Coronavirus in Dromedaries in Ethiopia Is Antigenically Different From the Middle East Isolate EMC

• Published in: Frontiers in microbiology Vol. 10; p. 1326
• Main Authors: Shirato, Kazuya, Melaku, Simenew Keskes, Kawachi, Kengo, Nao, Naganori, Iwata-Yoshikawa, Naoko, Kawase, Miyuki, Kamitani, Wataru, Matsuyama, Shutoku, Tessema, Tesfaye Sisay, Sentsui, Hiroshi
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 19.06.2019
• Subjects: antigenicity; dromedary; Ethiopia; Microbiology; Middle East respiratory syndrome; Middle East respiratory syndrome coronavirus; neutralization; antigenicity; Middle East respiratory syndrome coronavirus; Middle East respiratory syndrome; neutralization; Ethiopia; dromedary
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2019.01326

Middle East respiratory syndrome (MERS) is an emerging respiratory disease caused by the MERS coronavirus (MERS-CoV). MERS has been endemic to Saudi Arabia since 2012. The reservoir of MERS-CoV is the dromedary camel, suggesting that MERS is primarily a zoonotic disease. MERS-CoV is common in dromedaries throughout the Middle East, North Africa, and East Africa as evidenced by neutralizing antibodies against MERS-CoV; however, human cases have remained limited to the Middle East. To better understand the cause of this difference, the virological properties of African camel MERS-CoV were analyzed based on the spike (S) protein in Ethiopia. Nasal swabs were collected from 258 young dromedaries (≤ 2 years old) in the Afar region of Ethiopia, of which 39 were positive for MERS-CoV, as confirmed by genetic tests. All positive tests were exclusive to the Amibara woreda region. Using next-generation sequencing, two full-length genomes of Amibara isolates were successfully decoded; both isolates belonged to the C2 clade based on phylogenetic analysis of full-length and S protein sequences. Recombinant EMC isolates of MERS-CoV, in which the S protein is replaced with those of Amibara isolates, were then generated to test the roles of these proteins in viral properties. Amibara S recombinants replicated more slowly in cultured cells than in EMC S recombinants. In neutralizing assays, Amibara S recombinants were neutralized by lower concentrations of sera from both Ethiopian dromedaries and EMC isolate (wild-type)-immunized mouse sera, relative to the EMC S recombinants, indicating that viruses coated in the Amibara S protein were easier to neutralize than the EMC S protein. Neutralization experiments performed using S1/S2 chimeric recombinants of the EMC and Amibara S proteins showed that the neutralization profile was dependent on the S1 region of the S protein. These results suggest that the slower viral replication and the ease of neutralization seen in the Ethiopian MERS-CoV are due to strain-specific differences in the S protein and may account for the absence of human MERS-CoV cases in Ethiopia.