Murine coronavirus (M-CoV) is a virus in the genus Betacoronavirus that infects mice. Belonging to the subgenus Embecovirus, murine coronavirus strains are enterotropic or polytropic. Enterotropic strains include mouse hepatitis virus (MHV) strains D, Y, RI, and DVIM, whereas polytropic strains, such as JHM and A59, primarily cause hepatitis, enteritis, and encephalitis. Murine coronavirus is an important pathogen in the laboratory mouse and the laboratory rat. It is the most studied coronavirus in animals other than humans, and has been used as an animal disease model for many virological and clinical studies.
Types
Murine hepatitis virus Murine coronavirus was first discovered in 1949. The researchers isolated the virus from the brain, spinal cord, liver, lung, spleen, and kidney of a rat with symptoms of encephalitis and severe myelin injury, and gave it the strain name mouse hepatitis virus (MHV)-JHM. MHV is now the most studied coronavirus in animals other than humans, acting as a model organism for coronaviruses. There are more than 25 different strains of murine coronavirus. Transmitted by the fecal–oral or respiratory route, these viruses infect the livers of mice and have been used as an animal disease model for hepatitis. Transmitted in fecal matter, the strains MHV-D, MHV-DVIM, MHV-Y and MHV-RI mainly infect the digestive tract, sometimes infecting the spleen, liver and lymphatic tissue. MHV-1, MHV-2, MHV-3, MHV-A59, MHV-S, MHV-JHM and other virus strains replicate in the respiratory tract and then spread to other organs such as the liver, lungs and brain. MHV-JHM mainly infects the central nervous system and has been widely studied since 1949. In rats, these nerve-infecting hepatitis viruses can cause acute or chronic neurological symptoms. Infection leads to demyelination, serving as an animal disease model of multiple sclerosis. MHV-2, MHV-3 and MHV-A59 can also infect the liver; the first two of these are more virulent. MHV-3 is the main virus strain used to study hepatitis; MHV-1 mainly infects the lungs. Murine hepatitis virus is highly infectious and is one of the most common pathogens in laboratory mice. The symptoms of infection vary according to the type, path of infection, genotype and age of mouse. MHV-1, MHV-S and MHV-Y are weak viral strains; MHV-2, MHV-3, MHV-A5 9 and MHV-JHM are more virulent, being relatively mild in adult mice but having a high mortality in newborns. Infection, even if it does not cause obvious symptoms, may affect the immune system of laboratory subjects and cause errors in the interpretation of experimental results. For example, the virus can replicate in macrophages and affect their function, as well as in the spleen, where infection stimulates natural killer cells and affects T cell and B cells. There is no vaccine to prevent and treat hepatitis virus infection in mice, mainly because of the high mutation rate and the variety of virus strains, as well as concerns that vaccination may itself interfere with the interpretation of experimental research results, but this virus can be used as an experimental model for the development of other coronavirus vaccines. In 1991, Michael M. C. Lai's laboratory completed the whole genome sequencing of the murine hepatitis virus. With a total length of 31,000 nucleotides, it was the largest RNA virus genome known at that time. In 2002, American virologist Ralph S. Baric developed a reverse genetic system for mouse hepatitis virus in which a complete MHV cDNA was assembled from smaller fragments.
Fancy rat coronavirus In fancy rats, the rat coronavirus (RCoV or RCV) consists mainly of two virus strains, sialodacryoadenitis virus (SDAV) and Parker's RCoV (RCoV-P), both of which cause respiratory tract infections, with the former also affecting the eyes, Harderian gland, and salivary glands. In the past, it was believed that the symptoms caused by the two infections were different, but in recent years, it has been argued that the symptoms of both include eye and nasal discharge, large salivary gland enlargement, sialadenitis, photosensitivity, keratitis, shortness of breath, and pneumonia, among others. There is little to no obvious difference, and it has been suggested that Parker's rat coronavirus is only one type of rat salivary adenovirus. It is highly infectious. Generally, the symptoms in young rats are more serious, and some individuals suffer permanent eye damage.
Others In 1982, researchers found a coronavirus in the brains of mice after isolation of puffinosis coronavirus (PCoV), which causes skin and eye disease in Manx shearwaters. The virus found was very similar to rat hepatitis virus, but due to the use of laboratory mice in the isolation process, the possibility cannot be excluded that it was derived from a mouse and not from the birds. Subsequent studies have shown that the virus has hemagglutinin esterase (HE). If the coronavirus did indeed originate from shearwater, it is one of few bird coronaviruses that is not a gammacoronavirus or deltacoronavirus. In 2009, the International Committee on Taxonomy of Viruses (ICTV) classified this bird coronavirus as belonging to the murine coronavirus clade. From 2011 to 2013, researchers collected mouse samples at several locations in Zhejiang, China, and discovered three new virus strains in Longquan lesser ricefield rat, collectively described in 2015 as Longquan Rl rat coronavirus (LRLV).
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