The rat cytomegalovirus R78 G protein-coupled receptor gene is required for production of infectious virus in the spleen.
The rat cytomegalovirus (RCMV) R33 and R78 genes are conserved within members of the subfamily Betaherpesvirinae and encode proteins (pR33 and pR78, respectively) that show sequence similarity with G protein-coupled receptors. Previously, the biological relevance of these genes was demonstrated by the finding that R33- and R78-deleted RCMV strains are severely attenuated in vivo. In addition, R78-deleted strains were found to replicate less efficiently in cell culture. To monitor of the expression of R33- and R78-encoded proteins, recombinant RCMV strains, designated RCMV33G and RCMV78G, were generated. These recombinants expressed enhanced green fluorescent protein (EGFP)-tagged versions of pR33 and pR78 instead of native pR33 and pR78, respectively. Here it is reported that, although RCMV33G replicates as efficiently as wt virus in rat embryo fibroblast cultures, strain RCMV78G produces virus titres that are 3- to 4-fold lower than wt RCMV in the culture medium. This result indicates that the pR78-EGFP protein, as expressed by RCMV78G, does not completely functionally replace its native counterpart (pR78) in vitro. Interestingly, in infected rats, infectious RCMV33G was produced in significantly lower amounts than infectious wt RCMV, as well as RCMV78G, in the salivary glands. Conversely, although RCMV33G replicated to similar levels as wt virus in the spleen, both RCMV78G and an R78 knock-out strain (RCMV Delta R78a) replicated poorly in this organ. Together, these data indicate that R78 is crucial for the production of infectious RCMV in the spleen of infected rats.
Kaptein
Suzanne J F
SJF
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands.
Beisser
Patrick S
PS
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands.
Gruijthuijsen
Yvonne K
YK
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands.
Savelkouls
Kim G M
KGM
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands.
van Cleef
Koen W R
KWR
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands.
Beuken
Erik
E
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands.
Grauls
Gert E L M
GELM
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands.
Bruggeman
Cathrien A
CA
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands.
Vink
Cornelis
C
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6202 AZ Maastricht, The Netherlands.
D000818:Animals; D004195:Disease Models, Animal; D017353:Gene Deletion; D049452:Green Fluorescent Proteins; D006566:Herpesviridae Infections / Q000378:metabolism / Q000821:virology*; D008164:Luminescent Proteins; D008297:Male; D018146:Muromegalovirus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D012367:RNA, Viral / Q000032:analysis; D051381:Rats; D011917:Rats, Inbred Lew; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D013154:Spleen / Q000821:virology; D013997:Time Factors; D014162:Transfection; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014779:Virus Replication
D008164:Luminescent Proteins; C110721:R33 protein, rat cytomegalovirus; C120868:R78 protein, cytomegalovirus; D012333:RNA, Messenger; D012367:RNA, Viral; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D014764:Viral Proteins; D049452:Green Fluorescent Proteins