Friday, December 27, 2013

CDC EID: Replicative Capacity of MERS Coronavirus in Livestock Cell Lines

Volume 20, Number 2—February 2014




Replicative capacity of Middle East respiratory syndrome coronavirus (MERS-CoV) was assessed in cell lines derived from livestock and peridomestic small mammals on the Arabian Peninsula. Only cell lines originating from goats and camels showed efficient replication of MERS-CoV. These results provide direction in the search for the intermediate host of MERS-CoV.



Transmission of MERS-CoV between humans is still limited, and the identification of an intermediate animal host could enable the development of public health measures to prevent future spread of the virus among humans. Although MERS-CoV neutralizing antibodies have been detected in camels from Oman, Spain, and Egypt, the virus has not previously been detected in camels (8,9). An informed focusing of investigations on a select group of species, such as camels, could benefit epidemiologic investigations. To identify potential intermediate host species of MERS-CoV, we used in vitro testing to determine virus permissiveness in select cell culture models. In general, cell lines cannot depict the full pathogenicity of in vivo infection because infection is influenced by epithelium-specific differentiation of target cells and the presence of immune cells. However, for viruses such as CoVs, whose tropism is believed to be determined mainly by the availability of an appropriate entry receptor (10), epithelial cell cultures could indeed constitute valid surrogates of virus permissiveness in vivo. With these limitations in mind, our results are in concordance with the findings of MERS-CoV neutralizing antibodies in camels and with information regarding patient contact with animals in reports of 2 human cases of MERS-CoV infection (11,15). One of the patients owned a farm on which camels and goats were kept. Before onset of his own illness, the patient reported illness in several goats on his farm. The patient did not have direct contact with animals, but he reported having eaten goat meat and having had contact with one of the animal caretakers, who suffered from respiratory disease (15). The second patient reported direct contact with a diseased camel shortly before onset of his symptoms (11).
In our study, production of infectious virus particles was seen in goat lung and kidney cells and in camelid kidney cells. Excretion patterns indicative of kidney infection should be investigated once further clues to the identity of the MERS-CoV animal reservoir become available. Our preliminary findings suggest that ungulates, such as goats and camels, are a possible intermediate host of MERS-CoV; thus, exposure to urine and feces from these animals might constitute a source of human infection. Moreover, food products derived from these animals (e.g., meat and milk) should be tested for their potential to transmit MERS-CoV. The results of our study suggest that investigations into the MERS-CoV animal reservoir and intermediate host should focus on caprid (e.g., goats) and camelid hosts, and we identified several new cell lines for use in virus isolation studies.
Dr Eckerle is a virologist at the Institute of Virology in Bonn, Germany. Her primary research interest is characterization of novel and emerging zoonotic viruses.

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