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News Story - Assignment 2Infected for life. How does human cytomegalovirus do it?
Joshua Deerain 2013
Scientists from the University of Queensland may have uncovered how one of the world’s most prevalent viruses, human cytomegalovirus manages to infect us and set up a lifelong infection. Human cytomegalovirus (HCMV) is known to infect up to 90% of the population worldwide. It is one of the main causes of chronic rejection in transplant patients as well as a major infection of newborns. This can go on to cause a number of hearing, visual and mental impairments. The Australian research group is looking into a mouse virus (MCMV) that is very closely related to HCMV. What they discovered when they looked into this virus was a viral protein which is modified copy of a protein made by mice. Over a long period of time the mouse cytomegaloviruses have evolved to copy, modify and use host proteins in order to infect more efficiently by a process call viral mimicry. The viral protein they found, named M33, is a modified copy of a transmembrane receptor found in all animals including mice and humans. In order to test what importance this viral protein has in the virus, the scientists made a number of mutations to different regions of the protein. What they found was that when they made truncations to the end of the protein it lost its ability to signal and be moved around the cell properly. They then went on to infect mice with MCMV that had the mutated M33. The observation they made was that the virus had a reduced ability to set up the characteristic lifelong infection of the salivary glands. This has lead researchers to believe that the M33 viral protein has an important role in the initial infection stage. These types of viral proteins have attracted a lot of attention as potential antiviral drug targets. The researchers of this study report their results offer the first evidence that signaling disruption is accompanied by virus attenuation. The close relationship between the human and mouse cytomegaloviruses means that this discovery could be the key for developing new drugs to treat human cytomegalovirus infections. A viral protein made by HMCV known as UL33, has been found which behaves in a similar manner to M33 from MCMV. When the researchers infected mice with MCMV that had UL33 as well as the defective M33, they saw that the virus was able to set up an infection again. What does this mean for UL33 and HCMV? UL33 is looking like it is an essential protein used by HCMV to target and infect the salivary glands and a promising new drug target. Infection of the salivary glands is extremely important for these viruses to set up the lifelong infection undetectable by the immune system. In the case of humans and HCMV, salivary gland infection is a key contributor to the high frequency of infection observed worldwide. Virus replication in the salivary glands allows for direct exit out of the body, with our saliva the perfect vehicle for infecting new people. This is why we see such a high frequency of cases even in the developed world. In cancer research the contribution viruses’ play is becoming better understood and it appears they have a significant impact. Upwards of 15-20% of cancers are associated with viruses. While HCMV is not directly associated with any disease in healthy people, recent research has identified HCMV as potentially playing a role in some cancers. Research is not conclusive but suggests that HCMV infection of cancerous cells could promote the progression to later stage cancer and spread around the body. |
The article written here is in response to the journal article from Case et al. 2008, 'Functional Analysis of the Murine Cytomegalovirus Chemokine Receptor Homologue M33: Ablation of Constitutive Signaling is Associated with an Attenuated Phenotype in vivo' |