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1.  Cytomegalovirus Infection Modulates Cellular Immunity in an Experimental Model for Autoimmune Diabetes 
Background: Viral infections are thought to play a role in the development of autoimmune diseases like type 1 diabetes. In this study we investigated the effect of Rat Cytomegalovirus (RCMV) infection on cellular immunity in a well-defined animal model for diabetes, the Biobreeding (BB) rat.
Methods: Diabetes prone (DP)- and Diabetes resistant (DR)-BB rats were infected with 2 × 106 plaque forming units (pfu) RCMV. Diabetes development was monitored by frequent blood-glucose analysis. Effects of RCMV on CD4+, CD8+ and Vβ-TCR+ T-cell subsets were measured in vivo, and in vitro after restimulation with RCMV-infected fibroblasts. Proliferative capacity was determined by 3H-Thymidine incorporation.
Results: RCMV-infection resulted in a significant acceleration of diabetes onset in DP-BB rats ( p=0.003). Percentages CD4+ and CD8+ T-cells were not affected in vivo. In vitro, RCMV-restimulation resulted in a decreased CD4+/CD8+ blastoid T-cell ratio compared to ConA ( p=0.00028). Furthermore, RCMV-restimulation resulted in a strong RCMV-specific proliferation, which comprises about 50% of the response triggered by ConA. Vβ-TCR percentages did not change upon RCMV-infection or RCMV-restimulation.
Interpretation: RCMV-restimulation of splenic T-cells in vitro resulted in a strong RCMV-specific proliferation, probably also including autoreactive T-cells. In vivo, this polyclonal response might be involved in the observed accelerated diabetes development in DP-BB rats upon RCMV-infection.
PMCID: PMC2485415  PMID: 14768946
2.  RCMV increases intimal hyperplasia by inducing inflammation, MCP-1 expression and recruitment of adventitial cells to intima 
Herpesviridae  2010;1:7.
Cytomegalovirus (CMV) infection has been associated with accelerated transplant vasculopathy. In this study, we assessed the effects of acute rat CMV (RCMV) infection on vessel remodeling in transplant vasculopathy, focusing on allograft morphology, inflammation and contribution of adventitial cells to intimal hyperplasia.
Infrarenal aorta was locally infected with RCMV and transplanted from female F344 rats to male Lewis rats. Graft samples were collected 2 and 8 weeks after transplantation and analyzed for intimal hyperplasia, collagen degradation and inflammation. Transplantation of aorta followed by transplantation of RCMV infected and labeled isogenic adventitia were performed to study migration of adventitial cells towards the intima.
Intimal hyperplasia was increased threefold in infected allografts. RCMV induced apoptosis in the media, expression of matrix metalloproteinase 2, and decreased collagen deposits. Macrophage infiltration was increased in the infected allografts and resulted in increased production of MCP-1. RCMV-infected macrophages were observed in the adventitia and intima. Cells derived from infected adventitia migrated towards the intima of the allograft.
RCMV enhances infiltration of macrophages to the allografts, and thereby increases MCP-1 production and inflammation, followed by recruitment of adventitial cells to the intima and accelerated intimal hyperplasia.
PMCID: PMC3063229  PMID: 21429242
3.  Cytomegalovirus Latency Promotes Cardiac Lymphoid Neogenesis and Accelerated Allograft Rejection in CMV Naïve Recipients 
Human Cytomegalovirus (HCMV) infection is associated with the acceleration of transplant vascular sclerosis (TVS) and chronic allograft rejection (CR). HCMV-negative recipients of latently HCMV infected donor grafts are at highest risk for developing CMV-disease. Using a rat heart transplant CR model, we have previously shown that acute rat CMV (RCMV) infection following transplantation significantly accelerates both TVS and CR. Here, we report that RCMV-naïve recipients of heart allografts from latently RCMV-infected donors undergo acceleration of CR with similar kinetics as acutely infected recipients. In contrast to acutely infected recipients, treatment of recipients of latently infected donor hearts with ganciclovir did not prevent CR or TVS. We observed the formation of tertiary lymphoid structures (TLOs) containing macrophages and T-cells in latently infected hearts prior to transplantation but not in uninfected rats. Moreover, pathway analysis of gene expression data from allografts from latently infected donors, indicated an early and sustained production of TLO-associated genes compared to allografts from uninfected donors. We conclude that RCMV-induced TLO formation and alteration of donor tissue T-cell profiles prior to transplantation in part mediate the ganciclovir-insensitive rejection of latently infected donor allografts transplanted into naïve recipients by providing a scaffold for immune activation.
PMCID: PMC3454525  PMID: 21199347
Cytomegalovirus; Chronic Rejection; Transplant Vascular Sclerosis; Latency
4.  Cytomegalovirus-Mediated Upregulation of Chemokine Expression Correlates with the Acceleration of Chronic Rejection in Rat Heart Transplants 
Journal of Virology  2003;77(3):2182-2194.
Cytomegalovirus (CMV) infections have been shown to dramatically affect solid organ transplant graft survival in both human and animal models. Recently, it was demonstrated that rat CMV (RCMV) infection accelerates the development of transplant vascular sclerosis (TVS) in both rat heart and small bowel graft transplants. However, the mechanisms involved in this process are still unclear. In the present study, we determined the kinetics of RCMV-accelerated TVS in a rat heart transplant model. Acute RCMV infection enhances the development of TVS in rat heart allografts, and this process is initiated between 21 and 24 days posttransplantation. The virus is consistently detected in the heart grafts from day 7 until day 35 posttransplantation but is rarely found at the time of graft rejection (day 45 posttransplantation). Grafts from RCMV-infected recipients had upregulation of chemokine expression compared to uninfected controls, and the timing of this increased expression paralleled that of RCMV-accelerated neointimal formation. In addition, graft vessels from RCMV-infected grafts demonstrate the increased infiltration of T cells and macrophages during periods of highest chemokine expression. These results suggest that CMV-induced acceleration of TVS involves the increased graft vascular infiltration of inflammatory cells through enhanced chemokine expression.
PMCID: PMC140920  PMID: 12525653
5.  Tumor necrosis factor alpha promotes replication and pathogenicity of rat cytomegalovirus. 
Journal of Virology  1994;68(4):2297-2304.
We investigated the role of tumor necrosis factor alpha (TNF-alpha) in the pathogenesis of rat cytomegalovirus (RCMV) infection. TNF-alpha levels found in the sera of radiation-immunosuppressed rats in the course of infection (> 350 pg/ml) correlated with the development of RCMV disease. Administration of anti-TNF-alpha antibodies strongly reduced the severity of pneumonia and led to a reduction in virus titers. In immunocompetent rats, anti-TNF-alpha antibodies also significantly suppressed viral replication. Conversely, administration of TNF-alpha augmented RCMV replication and aggravated the disease signs. In vitro, TNF-alpha enhanced RCMV replication in the macrophage, whereas a reduction of viral replication was observed in fibroblasts, indicating that the effect on viral replication is cell type specific. Besides activation of viral replication and exacerbation of RCMV disease, TNF-alpha also favored lymphoid and hematopoietic tissue reconstitution after irradiation, which may contribute to antiviral resistance and survival. This finding demonstrates the protean nature of TNF-alpha, with both beneficial and adverse effects for the host. Our results suggest that TNF-alpha plays an important role in modulating the pathogenesis of RCMV infection.
PMCID: PMC236705  PMID: 8139014
6.  Infection With Viruses From Several Families Triggers Autoimmune Diabetes in LEW.1WR1 Rats 
Diabetes  2009;59(1):110-118.
The contribution of antecedent viral infection to the development of type 1 diabetes in humans is controversial. Using a newer rat model of the disease, we sought to 1) identify viruses capable of modulating diabetes penetrance, 2) identify conditions that increase or decrease the diabetogenicity of infection, and 3) determine whether maternal immunization would prevent diabetes.
About 2% of LEW.1WR1 rats develop spontaneous autoimmune diabetes, but disease penetrance is much higher if weanling rats are exposed to environmental perturbants including Kilham rat virus (KRV). We compared KRV with other viruses for diabetogenic activity.
Both KRV and rat cytomegalovirus (RCMV) induced diabetes in up to 60% of LEW.1WR1 rats, whereas H-1, vaccinia, and Coxsackie B4 viruses did not. Simultaneous inoculation of KRV and RCMV induced diabetes in 100% of animals. Pretreatment of rats with an activator of innate immunity increased the diabetogenicity of KRV but not RCMV and was associated with a moderate rate of diabetes after Coxsackie B4 and vaccinia virus infection. Inoculation of LEW.1WR1 dams with both KRV and RCMV prior to pregnancy protected weanling progeny from virus-induced diabetes in a virus-specific manner.
Exposure to viruses can affect the penetrance of autoimmune diabetes in genetically susceptible animals. The diabetogenicity of infection is virus specific and is modified by immunomodulation prior to inoculation. Maternal immunization protects weanlings from virus-induced diabetes, suggesting that modification of immune responses to infection could provide a means of preventing islet autoimmunity.
PMCID: PMC2797911  PMID: 19794063
7.  Cytomegalovirus CC Chemokine Promotes Immune Cell Migration 
Journal of Virology  2012;86(21):11833-11844.
Cytomegaloviruses manipulate the host chemokine/receptor axis by altering cellular chemokine expression and by encoding multiple chemokines and chemokine receptors. Similar to human cytomegalovirus (HCMV), rat cytomegalovirus (RCMV) encodes multiple CC chemokine-analogous proteins, including r129 (HCMV UL128 homologue) and r131 (HCMV UL130 and MCMV m129/130 homologues). Although these proteins play a role in CMV entry, their function as chemotactic cytokines remains unknown. In the current study, we examined the role of the RCMV chemokine r129 in promoting cellular migration and in accelerating transplant vascular sclerosis (TVS) in our rat heart transplant model. We determined that r129 protein is released into culture supernatants of infected cells and is expressed with late viral gene kinetics during RCMV infection and highly expressed in heart and salivary glands during in vivo rat infections. Using the recombinant r129 protein, we demonstrated that r129 induces migration of lymphocytes isolated from rat peripheral blood, spleen, and bone marrow and from a rat macrophage cell line. Using antibody-mediated cell sorting of rat splenocytes, we demonstrated that r129 induces migration of naïve/central memory CD4+ T cells. Through ligand-binding assays, we determined that r129 binds rat CC chemokine receptors CCR3, CCR4, CCR5, and CCR7. In addition, mutational analyses identified functional domains of r129 resulting in recombinant proteins that fail to induce migration (r129-ΔNT and -C31A) or alter the chemotactic ability of the chemokine (r129-F43A). Two of the mutant proteins (r129-C31A and -ΔNT) also act as dominant negatives by inhibiting migration induced by wild-type r129. Furthermore, infection of rat heart transplant recipients with RCMV containing the r129-ΔNT mutation prevented CMV-induced acceleration of TVS. Together our findings indicate that RCMV r129 is highly chemotactic, which has important implications during RCMV infection and reactivation and acceleration of TVS.
PMCID: PMC3486311  PMID: 22915808
Virology  2009;388(1):78-90.
While cytomegalovirus (CMV) infects and replicates in a multitude of cell types, the ability of the virus to replicate in antigen presenting cells (APCs) is believed to play a critical role in the viral dissemination and latency. CMV infection of APCs and manipulation of their function is an important area of investigation. CMV down regulation of MHC II is reportedly mediated by the HCMV proteins US2, US3, UL83, UL111a (vIL10) or through the induction of cellular IL10. In this study, we demonstrate that rat CMV (RCMV) significantly reduces MHC II expression by mechanisms that do not involve orthologues of the known HCMV genes nor by an increase in cellular IL10. Rat bone marrow derived dendritic cells (BMDC) were highly susceptible to infection with RCMV and a recombinant RCMV expressing eGFP. RCMV infection of BMDCs depleted both surface and intracellular MHC II to nearly undetectable levels as well as reduced surface expression of MHC I. The effect on MHC II only occurred in the infected GFP positive cells and is mediated by an immediate early or early viral gene product. Furthermore, treatment of uninfected immature DCs with virus-free conditioned supernatants from infected cells failed to down regulate MHC II. RCMV depletion of MHC II was sensitve to treatment with lysosomal inhibitors but not proteasomal inhibitors suggesting that the mechanism of RCMV mediated down-regulation of MHC II occurs through endocytic degradation. Since RCMV does not encode homologues of US2, US3, UL83 or UL111a, these data indicate a novel mechanism for RCMV depletion of MHC II.
PMCID: PMC2749604  PMID: 19349057
9.  Pathogenesis and vertical transmission of a transplacental rat cytomegalovirus 
Virology Journal  2006;3:42.
Cytomegalovirus (CMV) congenital infection is the major viral cause of well-documented birth defects in human. Because CMV is species-specific, the main obstacle to developing animal models for congenital infection is the difference in placental architecture, which preludes virus transmission across the placenta. The rat placenta, resembling histologically to that of human, could therefore facilitate the study of CMV congenital infection in human.
In this report, we present clear evidences of the transplacental property of a new rat CMV (RCMV), namely ALL-03, which had been isolated from placenta and uterus of the house rat. Our study signifies the detection of infectious virus, virus particles, viral protein and DNA as well as immune response to demonstrate a natural model of acute CMV infection including the immunocompetent and immunocompromised host associated with or without pregnancy. It is characterized by a full range of CMV related clinical signs; lesions and anatomical virus distribution to uterus, placenta, embryo, fetus, neonate, lung, kidney, spleen, liver and salivary gland of the infected rats in addition to the virus-specific seroconversion. The preference of the virus for different organs mimics the situation in immunocompromised man. Most interestingly, the placenta was observed to be involved in the maternofetal infection and hence confirmed the hypothesis that the RCMV strain ALL-03 is capable to cross the placenta and infect the offsprings congenitally.
The maternal viremia leading to uterine infection which subsequently infecting to the fetus through the placenta is the most likely phenomenon of CMV vertical transmission in our study.
PMCID: PMC1500997  PMID: 16737550
10.  The r144 Major Histocompatibility Complex Class I-Like Gene of Rat Cytomegalovirus Is Dispensable for both Acute and Long-Term Infection in the Immunocompromised Host 
Journal of Virology  2000;74(2):1045-1050.
The rat cytomegalovirus (RCMV) r144 gene encodes a polypeptide homologous to major histocompatibility complex class I heavy chains. To study the role of r144 in virus replication, an RCMV r144 null mutant strain (RCMVΔr144) was generated. This strain replicated with efficiency similar to that of wild-type (WT) RCMV in vitro. Additionally, WT RCMV and RCMVΔr144 were found not to differ in their replication characteristics in vivo. First, the survival rate was similar among groups of immunosuppressed rats infected with either RCMVΔr144 or WT RCMV. Second, the dissemination of virus did not differ in either RCMVΔr144- or WT RCMV-infected, immunosuppressed rats, either in the acute phase of infection or approximately 1 year after infection. These data indicate that the RCMV r144 gene is essential neither for virus replication in the acute phase of infection nor for long-term infection in immunocompromised rats. Interestingly, in a local infection model in which footpads of immunosuppressed rats were inoculated with virus, a significantly higher number of infiltrating macrophage cells as well as of CD8+ T cells was observed in WT RCMV-infected paws than in RCMVΔr144-infected paws. This suggests that r144 might function in the interaction with these leukocytes in vivo.
PMCID: PMC111630  PMID: 10623772
11.  Rotavirus Infection Accelerates Type 1 Diabetes in Mice with Established Insulitis▿  
Journal of Virology  2008;82(13):6139-6149.
Infection modulates type 1 diabetes, a common autoimmune disease characterized by the destruction of insulin-producing islet β cells in the pancreas. Childhood rotavirus infections have been associated with exacerbations in islet autoimmunity. Nonobese diabetic (NOD) mice develop lymphocytic islet infiltration (insulitis) and then clinical diabetes, whereas NOD8.3 TCR mice, transgenic for a T-cell receptor (TCR) specific for an important islet autoantigen, show more rapid diabetes onset. Oral infection of infant NOD mice with the monkey rotavirus strain RRV delays diabetes development. Here, the effect of RRV infection on diabetes development once insulitis is established was determined. NOD and NOD8.3 TCR mice were inoculated with RRV aged ≥12 and 5 weeks, respectively. Diabetes onset was significantly accelerated in both models (P < 0.024), although RRV infection was asymptomatic and confined to the intestine. The degree of diabetes acceleration was related to the serum antibody titer to RRV. RRV-infected NOD mice showed a possible trend toward increased insulitis development. Infected males showed increased CD8+ T-cell proportions in islets. Levels of β-cell major histocompatibility complex class I expression and islet tumor necrosis factor alpha mRNA were elevated in at least one model. NOD mouse exposure to mouse rotavirus in a natural experiment also accelerated diabetes. Thus, rotavirus infection after β-cell autoimmunity is established affects insulitis and exacerbates diabetes. A possible mechanism involves increased exposure of β cells to immune recognition and activation of autoreactive T cells by proinflammatory cytokines. The timing of infection relative to mouse age and degree of insulitis determines whether diabetes onset is delayed, unaltered, or accelerated.
PMCID: PMC2447104  PMID: 18417562
12.  Dissemination of Rat Cytomegalovirus through Infected Granulocytes and Monocytes In Vitro and In Vivo 
Journal of Virology  2003;77(20):11274-11278.
The role of leukocytes in the in vivo dissemination of cytomegalovirus was studied in this experiment. Rat cytomegalovirus (RCMV) could be transferred to rat granulocytes and monocytes by cocultivation with RCMV-infected fibroblasts in vitro. Intravenous injection of purified infected granulocytes or monocytes resulted in a systemic infection in rats, indicating that our model is a powerful tool to gain further insight into CMV dissemination and the development of new antivirals.
PMCID: PMC224975  PMID: 14512575
13.  Complete Genome Sequence of the English Isolate of Rat Cytomegalovirus (Murid Herpesvirus 8) 
Journal of Virology  2012;86(24):13838.
The complete genome of the English isolate of rat cytomegalovirus (RCMV-E) was determined. RCMV-E has a 202,946-bp genome with noninverting repeats but without terminal repeats. Thus, it differs significantly in size and genomic arrangement from closely related rodent cytomegaloviruses (CMVs). To account for the differences between the rat CMV isolates of Maastricht and England, RCMV-E was classified as Murid herpesvirus 8 by the International Committee on Taxonomy of Viruses.
PMCID: PMC3503139  PMID: 23166247
14.  Rotavirus Infection of Infant and Young Adult Nonobese Diabetic Mice Involves Extraintestinal Spread and Delays Diabetes Onset▿  
Journal of Virology  2007;81(12):6446-6458.
Rotaviruses have been implicated as a possible viral trigger for exacerbations in islet autoimmunity, suggesting they might modulate type 1 diabetes development. In this study, the ability of rotavirus strain RRV to infect the pancreas and affect insulitis and diabetes was examined in nonobese diabetic (NOD) mice, an experimental model of type 1 diabetes. Mice were inoculated either orally or intraperitoneally as infants or young adults. In infant mice inoculated orally, rotavirus antigen was detected in pancreatic macrophages outside islets and infectious virus was found in blood cells, pancreas, spleen, and liver. Extraintestinal RRV spread and pancreatic presence of infectious virus also occurred in intraperitoneally inoculated infant and adult mice. The initiation of insulitis was unaltered by infection. The onset of diabetes was delayed in infant mice inoculated orally and infant and adult mice inoculated intraperitoneally. In contrast, adult mice inoculated orally showed no evidence of pancreatic RRV, the lowest rate of detectable RRV replication, and no diabetes modulation. Thus, the ability of RRV infection to modulate diabetes development in infant and young adult NOD mice was related to the overall extent of detectable virus replication and the presence of infectious virus extraintestinally, including in the pancreas. These studies show that RRV infection of infant and young adult NOD mice provides significant protection against diabetes. As these findings do not support the hypothesis that rotavirus triggers autoimmunity related to type 1 diabetes, further research is needed to resolve this issue.
PMCID: PMC1900081  PMID: 17428851
15.  Rat Cytomegalovirus Gene Expression in Cardiac Allograft Recipients Is Tissue Specific and Does Not Parallel the Profiles Detected In Vitro▿  
Journal of Virology  2007;81(8):3816-3826.
Rat cytomegalovirus (RCMV) is a β-herpesvirus with a 230-kbp genome containing over 167 open reading frames (ORFs). RCMV gene expression is tightly regulated in cultured cells, occurring in three distinct kinetic classes (immediate early, early, and late). However, the extent of viral-gene expression in vivo and its relationship to the in vitro expression are unknown. In this study, we used RCMV-specific DNA microarrays to investigate the viral transcriptional profiles in cultured, RCMV-infected endothelial cells, fibroblasts, and aortic smooth muscle cells and to compare these profiles to those found in tissues from RCMV-infected rat heart transplant recipients. In cultured cells, RCMV expresses approximately 95% of the known viral ORFs with few differences between cell types. By contrast, in vivo viral-gene expression in tissues from rat heart allograft recipients is highly restricted. In the tissues studied, a total of 80 viral genes expressing levels twice above background (5,000 to 10,000 copies per μg total RNA) were detected. In each tissue type, there were a number of genes expressed exclusively in that tissue. Although viral mRNA and genomic DNA levels were lower in the spleen than in submandibular glands, the number of individual viral genes expressed was higher in the spleen (60 versus 41). This finding suggests that the number of viral genes expressed is specific to a given tissue and is not dependent upon the viral load or viral mRNA levels. Our results demonstrate that the profiles, as well as the amplitude, of viral-gene expression are tissue specific and are dramatically different from those in infected cultured cells, indicating that RCMV gene expression in vitro does not reflect viral-gene expression in vivo.
PMCID: PMC1866122  PMID: 17251289
16.  Complete DNA Sequence of the Rat Cytomegalovirus Genome 
Journal of Virology  2000;74(16):7656-7665.
We have determined the complete genome sequence of the Maastricht strain of rat cytomegalovirus (RCMV). The RCMV genome has a length of 229,896 bp and is arranged as a single unique sequence flanked by 504-bp terminal direct repeats. RCMV was found to have counterparts of all but one of the open reading frames (ORFs) that are conserved between murine CMV (MCMV) and human CMV (HCMV). Like HCMV, RCMV lacks homologs of the genes belonging to the MCMV m02 glycoprotein gene family. However, RCMV contains 15 ORFs with homology to members of the MCMV m145 glycoprotein gene family. Four ORFs are predicted to encode homologs of host proteins; R33 and R78 both putatively encode G protein-coupled receptors, whereas r144 and r131 encode homologs of major histocompatibility class I heavy chains and CC chemokines, respectively. An intriguing feature of the RCMV genome is the presence of an ORF, r127, with similarity to the rep gene of parvoviruses as well as ORF U94 of human herpesvirus 6A (HHV-6A) and HHV-6B. Counterparts of these ORFs have not been found in the other sequenced herpesviruses.
PMCID: PMC112289  PMID: 10906222
17.  Developing a Vaccine against Congenital Cytomegalovirus (CMV) Infection: What Have We Learned from Animal Models? Where Should We Go Next? 
Future virology  2013;8(12):1161-1182.
Congenital human cytomegalovirus (HCMV) infection can lead to long-term neurodevelopmental sequelae, including mental retardation and sensorineural hearing loss. Unfortunately, CMVs are highly adapted to their specific species, precluding the evaluation of HCMV vaccines in animal models prior to clinical trials. Several species-specific CMVs have been characterized and developed in models of pathogenesis and vaccine-mediated protection against disease. These include the murine CMV (MCMV), the porcine CMV (PCMV), the rhesus macaque CMV (RhCMV), the rat CMV (RCMV), and the guinea pig CMV (GPCMV). Because of the propensity of the GPCMV to cross the placenta, infecting the fetus in utero, it has emerged as a model of particular interest in studying vaccine-mediated protection of the fetus. In this paper, a review of these various models, with particular emphasis on the value of the model in the testing and evaluation of vaccines against congenital CMV, is provided. Recent exciting developments and advances in these various models are summarized, and recommendations offered for high-priority areas for future study.
PMCID: PMC3919633  PMID: 24523827
Cytomegalovirus; Animal cytomegalovirus models; Guinea pig CMV; Rat CMV; Murine CMV; Rhesus CMV; Porcine CMV; Cytomegalovirus vaccine; Live; attenuated CMV vaccines; CMV pentameric complex; Guinea pig model; placenta; immune modulation
18.  Suppression of rat cytomegalovirus replication by antibodies against gamma interferon. 
Journal of Virology  1994;68(4):2305-2312.
The role of gamma interferon (IFN-gamma) in the resolution of rat cytomegalovirus (RCMV) infection was investigated. In the spleen, IFN-gamma-producing cells reached maximum numbers on day 7 after infection. Prophylactic treatment with high doses of recombinant rat IFN-gamma exerted antiviral activity in fibroblasts and protected immunosuppressed rats against a lethal RCMV challenge. Remarkably, in immunocompetent rats, neutralization of endogenous IFN-gamma activity significantly reduced the numbers of RCMV antigen-expressing cells in the spleen, the predominant site of viral replication. Moreover, protection of radiation-immunosuppressed infected rats by transferred immune T cells was enhanced by coinjection of IFN-gamma neutralizing antibodies. The observations were paralleled by in vitro findings: low concentrations of IFN-gamma enhanced viral replication in both macrophages and fibroblasts. These data suggest that IFN-gamma can play different and even opposite roles in the regulation of RCMV replication in vivo; T lymphocytes may contribute to the progression of RCMV infection by secreting IFN-gamma.
PMCID: PMC236706  PMID: 8139015
19.  Characterization of the major locus of immediate-early genes of rat cytomegalovirus. 
Journal of Virology  1993;67(7):4093-4103.
A major locus of rat cytomegalovirus (RCMV) immediate-early (IE) RNA transcription was identified. A cDNA library from rat embryo fibroblasts infected with RCMV under IE conditions was constructed and screened by using appropriate RCMV DNA probes, revealing at least two IE genes (IE1 and IE2) transcribed from this locus by differential splicing. The first three exons (the first is noncoding) are spliced to exon 4 to form IE1 and to exon 5 to form IE2. The structural organization of the RCMV major IE region is therefore similar to that of human cytomegalovirus (HCMV) and murine cytomegalovirus (MCMV). When we compared the predicted amino acid sequences of the IE1 proteins of RCMV, HCMV, and MCMV, no areas of homology were found across all three proteins, while a few small areas of homology were found between RCMV IE1 and MCMV IE1. In contrast, large areas of homology were found across the carboxyl half of RCMV IE2, HCMV IE2, and MCMV ie3 proteins. In addition, similarities were found at the beginning of exon 5 of RCMV and MCMV. The possible significance of these conserved regions is discussed. Dinucleotide frequency analysis demonstrated a decrease in CpG frequency over the IE region. The IE gene products were able to transactivate heterologous promoters.
PMCID: PMC237778  PMID: 8389919
20.  Rat Cytomegalovirus Major Immediate-Early Enhancer Switching Results in Altered Growth Characteristics 
Journal of Virology  2001;75(11):5076-5083.
It has been hypothesized that the major immediate-early (MIE) enhancer of cytomegalovirus (CMV) is important in determining virus tropism and latency because of its essential role in initiating the cascade of early gene expression necessary for virus replication. Although rat CMV (RCMV) and murine CMV (MCMV) exhibit extreme species specificity in vivo, they differ in their ability to replicate in tissue culture. MCMV can replicate in a rat embryo fibroblast (REF) cell line while RCMV does not grow in murine fibroblasts. The tropism is not due to a block in virus entry into the cell. We have constructed a recombinant RCMV in which the RCMV MIE enhancer has been replaced with that of MCMV. Growth of the recombinant virus in tissue culture remains restricted to rat cells, suggesting that other viral and/or host factors are more important in determining in vitro tropism. Unlike findings using recombinant MCMV in which the human CMV (HCMV) MIE enhancer substitutes for the native one (A. Angulo, M. Messerle, U. H. Koszinowski, and P. Ghazal, J. Virol. 72:8502–8509, 1998), infection with our recombinant virus at a low multiplicity of infection resulted in a substantial decrease in virus replication. This occurred despite comparable or increased MIE transcription from the recombinant virus. In vivo experiments showed that the recombinant virus replicates normally in the spleen during acute infection. Notably, the recombinant virus appears to be deficient in spreading to the salivary gland, suggesting a role for the MIE enhancer in tropism for certain tissues involved in virus dissemination. Four months after infection, recombinant virus with the foreign MIE enhancer was reactivated from spleen explants.
PMCID: PMC114912  PMID: 11333888
21.  Nitric Oxide Partially Controls Coxiella burnetii Phase II Infection in Mouse Primary Macrophages  
Infection and Immunity  2003;71(3):1225-1233.
In most primary or continuous cell cultures infected with the Q-fever agent Coxiella burnetii, bacteria are typically sheltered in phagolysosome-like, large replicative vacuoles (LRVs). We recently reported that only a small proportion of mouse peritoneal macrophages (PMΦ) infected with a nonvirulent, phase II strain of C. burnetii developed LRVs and that their relative bacterial load increased only slowly. In the majority of infected PMΦ, the bacteria were confined to the small vesicles. We show here that nitric oxide (NO) induced by the bacteria partially accounts for the restricted development of LRVs in primary macrophages. Thus, (i) PMΦ and bone marrow-derived macrophages (BMMΦ) challenged with phase II C. burnetii produced significant amounts of NO; (ii) the NO synthase inhibitors aminoguanidine and N-methyl-l-arginine reduced the production of NO and increased the frequency of LRVs (although the relative bacterial loads of individual LRVs did not change, the estimated loads per well increased appreciably); (iii) gamma interferon (IFN-γ) or the NO donor sodium nitroprusside, added to BMMΦ prior to or after infection, reduced the development and the relative bacterial loads of LRVs and lowered the yield of viable bacteria recovered from the cultures; and (iv) these effects of IFN-γ may not be entirely dependent on the production of NO since IFN-γ also controlled the infection in macrophages from inducible NO synthase knockout mice. It remains to be determined whether NO reduced the development of LRVs by acting directly on the bacteria; by acting on the traffic, fusion, or fission of cell vesicles; or by a combination of these mechanisms.
PMCID: PMC148841  PMID: 12595436
22.  Regenerating 1 and 3b Gene Expression in the Pancreas of Type 2 Diabetic Goto-Kakizaki (GK) Rats 
PLoS ONE  2014;9(2):e90045.
Regenerating (REG) proteins are associated with islet development, β-cell damage, diabetes and pancreatitis. Particularly, REG-1 and REG-3-beta are involved in cell growth/survival and/or inflammation and the Reg1 promoter contains interleukin-6 (IL-6)-responsive elements. We showed by transcriptome analysis that islets of Goto-Kakizaki (GK) rats, a model of spontaneous type 2 diabetes, overexpress Reg1, 3α, 3β and 3γ, vs Wistar islets. Goto-Kakizaki rat islets also exhibit increased cytokine/chemokine expression/release, particularly IL-6. Here we analyzed Reg1 and Reg3β expression and REG-1 immuno-localization in the GK rat pancreas in relationship with inflammation. Isolated pancreatic islets and acinar tissue from male adult Wistar and diabetic GK rats were used for quantitative RT-PCR analysis. REG-1 immunohistochemistry was performed on paraffin sections with a monoclonal anti-rat REG-1 antibody. Islet cytokine/chemokine release was measured after 48 h-culture. Islet macrophage-positive area was quantified on cryostat sections using anti-CD68 and major histocompatibility complex (MHC) class II antibodies. Pancreatic exocrine-to-endocrine Reg1 and Reg3β mRNA ratios were markedly increased in Wistar vs GK rats. Conversely, both genes were upregulated in isolated GK rat islets. These findings were unexpected, because Reg genes are expressed in the pancreatic acinar tissue. However, we observed REG-1 protein labeling in acinar peri-ductal tissue close to islets and around large, often disorganized, GK rat islets, which may retain acinar cells due to their irregular shape. These large islets also showed peri-islet macrophage infiltration and increased release of various cytokines/chemokines, particularly IL-6. Thus, IL-6 might potentially trigger acinar REG-1 expression and secretion in the vicinity of large diabetic GK rat islets. This increased acinar REG-1 expression might reflect an adaptive though unsuccessful response to deleterious microenvironment.
PMCID: PMC3936001  PMID: 24587207
23.  The R33 G Protein-Coupled Receptor Gene of Rat Cytomegalovirus Plays an Essential Role in the Pathogenesis of Viral Infection 
Journal of Virology  1998;72(3):2352-2363.
We have identified a rat cytomegalovirus (RCMV) gene that encodes a G-protein-coupled receptor (GCR) homolog. This gene (R33) belongs to a family that includes the human cytomegalovirus UL33 gene. R33 was found to be transcribed during the late phase of RCMV infection in rat embryo fibroblasts. Unlike the mRNAs from all the other members of the UL33 family that have been studied to date, the R33 mRNA is not spliced. To study the function of the R33 gene, we constructed an RCMV strain in which the R33 open reading frame is disrupted. The mutant strain (RCMVΔR33) did not show differences in replication from wild-type RCMV upon infection of several rat cell types in vitro. However, marked differences were seen between the mutant and wild-type strain in the pathogenesis of infection in immunocompromised rats. First, the mutant strain induced a significantly lower mortality than the wild-type virus did. Second, in contrast to wild-type RCMV, the mutant strain did not efficiently replicate in the salivary gland epithelial cells of immunocompromised rats. Although viral DNA was detected in salivary glands of RCMVΔR33-infected rats up to 14 days postinfection, it could not be detected at later time points. This indicates that although the strain with R33 deleted is probably transported to the salivary glands in a similar fashion to that for wild-type virus, the mutant virus is not able to either enter or replicate in salivary gland epithelial cells. We conclude that the RCMV R33 gene plays a vital role in the pathogenesis of infection.
PMCID: PMC109535  PMID: 9499096
24.  Cytomegalovirus infection enhances smooth muscle cell proliferation and intimal thickening of rat aortic allografts. 
Journal of Clinical Investigation  1993;92(2):549-558.
Inbred DA (AG-B4, RT1a) and WF (AG-B2, RT1v) rats were used as donors and recipients of aortic allografts. The recipient rats were inoculated i.p. either on day 1 (early infection) or on day 60 (late infection) with 10(5) plaque-forming units of rat cytomegalovirus (RCMV). The control rats were left noninfected. The presence of viral infection was demonstrated by plaque assays from biopsies of the salivary glands, liver, and spleen at sacrifice. The rats received 300 microCi[3H]thymidine by i.v. injection 3 h before sacrifice, and the grafts were removed at various time points for histology, immunohistochemistry, and autoradiography. RCMV infection significantly enhanced the generation of allograft arteriosclerosis. Infection at the time of transplantation had two important effects. First, the infection was associated with an early, prominent inflammatory episode and proliferation of inflammatory cells in the allograft adventitia. Second, the viral infection doubled the proliferation rate of smooth muscle cells and the arteriosclerotic alterations in the intima. In late infection the impact of RCMV infection on the allograft histology was nearly nonexistent. RCMV infection showed no effect in syngeneic grafts. These results suggest that early infection is more important to the generation of accelerated allograft arteriosclerosis than late infection, and that an acute alloimmune response must be associated with virus infection, to induce accelerated allograft arteriosclerosis. RCMV-infected aortic allografts, as described here, provide the first experimental model to investigate the interaction between the virus and the vascular wall of the transplant.
PMCID: PMC294886  PMID: 8394384
25.  Rat cytomegalovirus-induced pneumonitis after allogeneic bone marrow transplantation: effective treatment with (S)-1-(3-hydroxy-2-phosphonyl-methoxypropyl)cytosine. 
Two antiviral compounds, (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) and 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG), were evaluated for their effects on rat cytomegalovirus (RCMV)-induced interstitial pneumonitis after allogeneic bone marrow transplantation (BMTx). Eight-week-old Brown Norway rats immunosuppressed by a lethal dose of total body irradiation were inoculated with RCMV and received allogeneic bone marrow cells from Lewis rats. Animals were treated with either HPMPC (20 mg/kg of body weight as a single dose) or DHPG (20 mg/kg as two daily doses for 5 days). The effect of antiviral therapy was monitored by measuring RCMV titers in different organs and the histopathologic changes in lungs at 8 to 10 days postinfection. In RCMV-infected allogeneic BMTx recipients, severe diffuse thickening of alveolar septa (6.02 microns) with a diffuse infiltration of mononuclear cells occurred, whereas in the noninfected allogeneic BMTx recipients, the septal width was on the order of 2 microns (P < 0.01). Treatment with DHPG (20 mg/kg in two daily doses for 5 days) resulted in a decrease in virus titers (log10 PFU per gram of tissue) in lungs and spleens from 3.81 +/- 0.34 and 4.29 +/- 1.07 (untreated animals) to 1.26 +/- 0.53 and 3.22 +/- 0.27 (treated animals), respectively. Treatment with HPMPC (20 mg/kg as a single dose) resulted in a complete reduction of virus titers in all organs to below the detection level (P < 0.01). Furthermore, antiviral treatment resulted in a reduction of the alveolar septal width from 6.02 +/- 1.59 microns (untreated animals) to 4.67 +/- 1.70 and 3.32 +/- 0.63 microns after DHPG and HPMPC treatment, respectively. Treatment with HPMPC (20 mg/kg as a single dose) resulted in a complete reduction of virus titers in all organs to below the detection level (P <0.01). Furthermore, antiviral treatment resulted in a reduction of the alveolar septal width from 6.02 +/- 1.59 micrometre (untreated animals) to 4.67 +/- 0.63 micrometre after DHPG and HPMPC treatment, respectively. Furthermore, the influx of mononuclear cells in the alveolar septa was significantly impaired after treatment with HPMPC (P <0.01). We conclude that in the described rat model, HPMPC is highly effective in suppressing RCMV-induced interstitial pneumonitis after allogeneic BMTx.
PMCID: PMC187642  PMID: 8383939

Results 1-25 (689321)