Isolates of cytomegalovirus (CMV) from the black rat Rattus rattus form a distinct group of rat CMV

Abstract

Two different betaherpesviruses, the English and Maastricht species of rat cytomegalovirus (CMV), have previously been isolated from Rattus norvegicus. CMVs were isolated from both the brown rat, R. norvegicus, and the black rat, R. rattus, within Australia. The viruses isolated from R. norvegicus appeared to be genetically related to the English species of rat CMV by PCR, RFLP, and sequencing, but the viruses isolated from R. rattus were distinct from both prototype virus species, although more closely genetically related to the Maastricht virus. This is the first genetic characterization of cytomegaloviruses from R. rattus, and the first isolation of CMVs from Australian rats.Cytomegaloviruses (CMVs) are species-specific betaherpesviruses capable of causing both acute and latent infections. They infect a broad range of species with individual virus strains exhibiting strict species specificity. Consequently, a species-specific CMV can be found in a diverse range of animals from mice to pigs, apes and humans (Staczek, 1990).CMVs have previously been isolated from the brown rat Rattus norvegicus [the Maastricht and English species of rat CMV (RCMV)] (Bruggeman et al., 1982;Priscott & Tyrrell, 1982). Whilst RFLP and sequence analysis has shown that the genomes of these viruses are collinear with the genomes of other CMVs, analysis of their genome size, growth characteristics, and sequencing of the major immediateearly locus suggests that they are not simply different strains of RCMV, but are in fact different betaherpesvirus species (Beisser et al., 1998). Sequencing of random clones derived from the English RCMV genome in our laboratory has confirmed the variation in sequence homology and possibly gene content between this virus and the Maastricht species (L. M. Smith & J. Redwood, unpublished data).The genome of the Maastricht species of RCMV has been fully sequenced (Vink et al., 2000). It is 230 138 bp in length, and contains a predicted 166 genes, 53 of which contain no significant homology to open reading frames in either murine (MCMV) or human (HCMV) cytomegaloviruses. This species of RCMV has been extensively studied as a model for cardiovascular disease, atherogenesis and transplant rejection caused by HCMV in humans (Streblow et al., 2003;Bruggeman et al., 1999;Orloff et al., 2002).We have isolated and characterized CMVs from several wild brown and black rats, as the isolation of betaherpesviruses from two closely related species would provide us with an opportunity to examine the evolutionary relationship between host and virus. The brown rat is also the only species apart from humans from which multiple betaherpesviruses have been isolated, allowing us to examine virusvirus interactions within the same host, and to more closely examine the immune-evasion genes found in each virus. The RCMVs isolated in this laboratory are the only CMVs isolated from R. norvegicus in Australia, and we report here the first genetic analysis of CMV isolates from the black rat, R. rattus, anywhere. Whilst CMV has previous...

Identification of Novel Rodent Herpesviruses, Including the First Gammaherpesvirus of Mus musculus

“…In Peromyscus maniculatus (deer mouse), as well as in R. norvegicus and R. rattus, several cytomegaloviruses have been detected recently. It remains to be determined how these relate to the rodent viruses described here, because only short partial sequences of the ORFs of UL33 (P. maniculatus) and R87 (Rattus species) have been published (22,18).…”

M‐CSF directs myeloid and NK cell differentiation to protect from CMV after hematopoietic cell transplantation

“…The role of monocytes and macrophages in CMV infection is multifaceted. On the one hand, rodent studies have shown they can be target cells for MCMV infection (Hanson et al , 1999 ; Hokeness et al , 2005 ; Daley‐Bauer et al , 2012 ), thus serving as vehicles of CMV dissemination (Smith et al , 2004 ; Daley‐Bauer et al , 2014 ). On the other hand, the observation that macrophage depletion in vivo increased MCMV burden (Hanson et al , 1999 ), also supports a protective role during CMV infection.…”

M-CSF induces a coordinated myeloid and NK cell differentiation program protecting against CMV after hematopoietic cell transplantation

“…The role of monocytes and macrophages in CMV infection is multifaceted. On the one hand, they can be target cells for MCMV infection ( 79–81 ), thus serving as vehicles of CMV dissemination ( 32, 82 ). On the other hand, the observation that macrophage depletion increased MCMV burden ( 79 ), also support a protective role during CMV infection.…”