14.06.2021: MERS-CoV, a betacoronavirus transmitted by dromedaries, is significantly more lethal than SARS-CoV-2, with a mortality rate in humans of up to 35%. A recently published international study led by Vetmeduni Vienna suggests that the immune response to MERS-CoV and SARS-CoV-2 is similar in infected individuals, whether human or dromedary. According to the researchers, further work is now urgently needed to better understand MERS-CoV disease dynamics in both dromedaries and humans.
The SARS-CoV-2 pandemic has refocused attention to the betacoronaviruses, only eight years after the emergence of Middle East respiratory syndrome coronavirus (MERS-CoV), another zoonotic betacoronavirus, for which dromedary camels are considered to be the intermediate host wild source. While the infection takes a mild course in dromedaries, the disease progresses more severely in humans, with a mortality rate of up to 35%. To better understand this discrepancy in disease progression, an international team of researchers led by Vetmeduni Vienna recently tested immune-response genes (IR genes) of dromedaries, specifically studying the extent to which these genes are associated with MERS-CoV infection. This is also important because MERS-CoV poses a serious threat to humans, with MERS-CoV infection in dromedaries confirmed in more than 25 countries on all continents except Australia.
Majority of dromedaries infected with MERS-CoV
The scientists sequenced 100 IR genes from 121 dromedaries, with samples taken from three different locations in the United Arab Emirates (UAE). All dromedaries were assessed for MERS-CoV antibodies to account for (past) infection and were also tested for the presence of the active virus. The assessment revealed an enormously high prevalence of antibodies in the animals, as first author Sara Lado from the Research Institute of Wildlife Ecology at Vetmeduni Vienna explains: “Most of the 121 dromedaries harboured MERS-CoV antibodies, and even young animals from the age of two months had already been exposed to the virus.”
Immune system responds similarly to SARS-CoV-1 and SARS-CoV-2
Using a phenotype-genotype association test, the researchers identified those IR genes that might be associated with MERS-CoV infection in dromedaries. Sara Lado: “We identified candidate genes with important functions in the adaptive (MHC-class I and II) and innate immune response (PTPN4, MAGOHB) as well as in cilia coating the respiratory tract (DNAH7). Some of these genes previously have been associated with viral replication in SARS-CoV-1/-2 in humans, while others have an important mechanical role in the movement of bronchial cilia.”
Although some of the gene variants associated with MERS-CoV have previously been linked to SARS-CoV-1/-2 and other respiratory infectious diseases, the researcher believe that further genomic and functional analyses will be necessary to confirm these results. “With our work, we are opening the door for future novel research, including large-scale screening for genes underlying defence mechanisms against zoonotic MERS-CoV,” says last author Pamela A. Burger, head of the Population Genetics and Conservation Genetics working group at the Research Institute of Wildlife Ecology at Vetmeduni Vienna.
Graphic "MERS-CoV and immune response genes in dromedaries" for download
The article “Innate and Adaptive Immune Genes Associated with MERS-CoV Infection in Dromedaries” by Sara Lado, Jean P. Elbers, Martin Plasil, Tom Loney, Pia Weidinger, Jeremy V. Camp, Jolanta Kolodziejek, Jan Futas, Dafalla A. Kannan, Pablo Orozco-terWengel, Petr Horin, Norbert Nowotny and Pamela A. Burger was published in cells.