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At least 19 recordsLinked to original sources
PubMed2005

The English strain of rat cytomegalovirus (CMV) contains a novel captured CD200 (vOX2) gene and a spliced CC chemokine upstream from the major immediate-early region: further evidence for a separate evolutionary lineage from that of rat CMV Maastricht.

Sequence data for eight genes, together with time-course Northern blotting and 3'- and 5'-RACE (rapid amplification of cDNA ends) analysis for some mRNAs from a 12 kb region upstream from the major immediate-early (MIE) genes of the English isolate of rat cytomegalovirus (RCMV), are presented. The results identified important differences compared to both murine cytomegalovirus (MCMV) and the Maastricht isolate of RCMV. A striking finding is the presence of a highly conserved, rightwards-oriented homologue of the rat cellular CD200 (OX2) gene immediately to the right of the MIE region, which replaces either the leftwards-oriented AAV REP gene of RCMV (Maastricht) or the upstream spliced portions of the immediate-early 2 gene (ie2) in MCMV. From the presence of other homologues of MCMV- and RCMV-specific genes, such as the beta-chemokine MCK-2, SGG1 and an Fcgamma receptor gene, as reported here, the basic architecture of the MIE region (reported previously) and the level of IE2 and DNA polymerase (POL) protein conservation in phylogenetic analyses, it is clear that the English strain of RCMV is also a member of the genus Muromegalovirus, but is a beta-herpesvirus species that is very distinct from both MCMV and RCMV (Maastricht). Both the lack of a CD200 homologue in the other two rodent viruses and the depth of sequence divergence of the rodent CMV IE2 and POL proteins suggest that these three viruses have evolved as separate species in the genus Muromegalovirus since very early in the host rodent lineage.

Animals↗
PubMed2001

Structural organization and analysis of the viral terminase gene locus of Tupaia herpesvirus.

Tupaia herpesvirus (THV) was isolated from spontaneously degenerating tissue cultures of malignant lymphoma, lung, and spleen cell cultures of tree shrews (Tupaia spp.). In order to determine the phylogenetic relatedness of THV the complete nucleotide sequence of the viral terminase (VTER) gene locus (6223 bp) of Tupaia herpesvirus strain 2 (THV-2) was elucidated and analysed. The VTER gene locus, encoding one of the most highly conserved herpes viral proteins is composed of two exons. The intron contains five potential open reading frames (ORFs). The arrangement of these ORFs is colinear with the corresponding regions in the genomes of the mammalian cytomegaloviruses. The precise primary structure of the THV-2 VTER splice junction was determined using RT-PCR and was found to be in agreement with the corresponding splice donor and acceptor sites of the mammalian cytomegaloviruses. The comparison of all six putative THV-2 proteins with the corresponding counterparts in other herpesviruses revealed that THV resides between the Human and the Murine cytomegalovirus (HCMV, MCMV). These results are in agreement with our previous statement, that THV and the known cytomegaloviruses are closely related to each other and should be classified into one taxonomic group. The genetic data presented here and in previous studies are based on the detailed comparison of highly conserved viral genes. Consequently, the classification of the Human and the cytomegaloviruses into the two genera Cyto- and Muromegalovirus, that is mainly based on overall genome structure, should be reconsidered.

Amino Acid Sequence↗
PubMed1996

Investigation of murine cytomegalovirus latency and reactivation in mice using viral mutants and the polymerase chain reaction.

Studies with 6 ts mutants of mouse cytomegalovirus indicated that mutants tsm1, tsm2, tsm3, and tsm6, like wild-type (wt) virus, produced acute infection in mice, became latent, and were reactivated as infectious virus immunosuppression. Using PCR, all five viruses expressed immediate-early (IE)-1, early (E)-1, and late (L, gB) genes during acute infection in all tissues examined (salivary glands, lung, spleen, liver, kidney, and heart). DNA was present in most tissues during latent infection with all five viruses, but transcription was restricted to the IE-1 gene in the salivary glands of wt infected mice only, suggesting true molecular latency rather than low level virus persistence. Similarly, mutant tsm5 expressed all three genes following primary inoculation. Although no detectable virus was produced, tsm5 subsequently entered the latent state as evidenced by DNA detection without RNA transcription indicating that productive infection is not required to initiate latency. This mutant also failed to reactivate from latency, although all three marker genes were expressed in most tissues. In contrast, tsm4 expressed all three marker genes and produced infectious virus during acute infection, then became latent. However, upon immunosuppression to reactivate tsm4, IE-1 and E-1 transcription occurred but neither gB transcription nor infectious virus was detectable in salivary glands, lung, spleen, liver, kidney, heart, or blood. The significance of this with regard to reactivation from latency is discussed.

3T3 Cells↗
PubMed2000

Murine cytomegalovirus replication in salivary glands is controlled by both perforin and granzymes during acute infection.

The course of mouse cytomegalovirus (MCMV) infection was compared between wild-type and mutant C57BL / 6 (B6) mice deficient in either RAG-2, perforin, granzyme A, granzyme B or combinations thereof at two time points post infection (p. i.). At day 15 p. i., virus titers were similarly elevated in salivary glands of all mutant, but not wild-type B6 mice and undetectable in lung and spleen tissues of any of the mouse strains. Significant pathological alterations were only seen in salivary glands and spleen from RAG2(- / -), but not in those from other mice whereas few inflammatory foci were observed in lung tissues of all mice except B6. At day 30 p. i., elevated virus titers were observed only in salivary glands, lung and spleen from RAG2(- / -), but in none of the other mice, and were accompanied by extended pathological alterations in all three organs. The data extend previous reports on the critical role of NK / CD8(+) T cells in the early control of MCMV infection by showing that both perforin and granzymes A / B contribute to viral elimination in salivary glands; however, neither of the three molecules alone seem to be indispensable for the final control of infection.

Animals↗
PubMed2000

Replication-defective mutants of mouse cytomegalovirus protect against wild-type virus challenge.

Five temperature-sensitive mutants (tsm9, tsm13, tsm20, tsm22, tsm30) of murine cytomegalovirus have been shown previously not to produce infectious virus in mice. In the present study, the stage at which these mutants are blocked in their replication in vitro was examined by transcriptional analysis of 4 temporally regulated marker genes (IE-1, E-1, gB and gH) using a semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) coupled with an electron microscopic analysis of infected cells incubated at permissive (33 degrees C) and non-permissive (39 and/or 40 degrees C) temperatures. Replication of tsm13 appeared to be blocked at a late phase of replication after capsid formation while the block appeared to be as early as the immediate-early phase in tsm22- infected cells. In contrast, mutants tsm9, tsm20 and tsm30 were blocked at a maturation step, probably of capsid formation, as gene transcription of all 4 marker genes occurred, albeit at reduced level, at 39 and 40 degrees C but no capsids or virions were produced at 40 degrees C. Replication and transcription of mutants tsm13, tsm20 and tsm30 were also examined in infected mice. Mutant tsm13 showed no gene expression or infectious virus while mutants tsm20 and tsm30 produced no infectious virus from days 3-60 post infection, except unusually for a low titre of tsm30 (2.3 x 10(3) pfu/ml) in salivary glands 21 days post infection. Gene transcription of all 4 marker genes was observed in one or more tissues (salivary glands, spleen, kidneys, liver, thymus, heart, lungs) at one or more time points (3, 7, 10, 14, 21 days post-infection) with both mutants. Mice became infected latently with tsm20 but not tsm30, and mice previously infected with tsm20 or tsm30 were protected against a sub-lethal challenge with virulent parental virus; tsm30 also protected against a lethal challenge. This suggests that these two mutants may be good model vaccines for further studies on the mechanism of protection induced and for identification of the ts genes.

Animals↗
PubMed2001

NK cell functions restrain T cell responses during viral infections.

NK cell functions for regulation of T cell responses were evaluated during acute viral infections. In vivo depletion studies established that the presence of NK cells in murine cytomegalovirus (MCMV)-infected immunocompetent mice negatively affected CD4 and CD8 T cell IFN-gamma expression, bromodeoxyuridine (BrdU) incorporation, and expansion. To evaluate NK cell effects, under conditions when NK cells do not control viral replication, experiments were performed using lymphocytic choriomeningitis virus (LCMV). Depletion of NK cells did not affect LCMV-elicited T cell responses in immunocompetent mice; however, the presence of NK cells did inhibit CD4 T cell IFN-gamma production, BrdU incorporation, and expansion in infected MHC class I- and CD8 T cell-deficient beta2M-/- mice. Together, the results reveal a previously unappreciated immunoregulatory role of NK cells for downstream T cell responses.

Animals↗
PubMed2002

Mechanism of host cell protection from complement in murine cytomegalovirus (CMV) infection: identification of a CMV-responsive element in the CD46 promoter region.

Mouse cells ubiquitously express CRRY, which is a functional orthologue of human decay-accelerating factor (DAF; CD55) and membrane cofactor protein (MCP; CD46), and thus protects cells from homologous complement. NIH3T3 cells expressed minute levels of mouse CD46 (mCD46) mRNA but barely produced mCD46 protein. mCD46 message and protein levels were markedly increased during mouse cytomegalovirus (mCMV) infection. Consistently, mCD46-expressing cells became resistant to mouse complement; primary-cultured fibroblasts from mCD46 gene-disrupted mice showed no increase in protection, resulting in complement-dependent cytolysis. Thus, the marked up-regulation of mCD46 in mouse fibroblast cells/cell lines by mCMV infection participates in host cell protection from complement. By mCD46 promoter deletion assay, the region necessary for induction of the promoter activity by mCMV infection was shown to be restricted to a sequence of 19 bp, which was homologous to the corresponding portion in human CD46, and the promoter regions of early-inducible human CMV UL36 and human herpesvirus 6 UL29. The results were confirmed by mutation analysis of this 19-bp region. We designated this sequence as the CMV-responsive element (CMVRE). Electrophoretic mobility shift assay demonstrated the existence of a CMVRE-binding factor, expression of which was significantly increased after mCMV infection. Thus, mCMV up-regulates the gene expression of mCD46 via CMVRE and CMVRE-binding factor, resulting in mCD46 protein expression on mCMV-infected cells. Since both the membrane and soluble mCD46retained complement regulatory activity, mCD46 induced by mCMV infection may act as a regulator of systemic complement activation. This represents a unique strategy of mCMV survival in host cells with sufficient replication by circumventing host complement attack.

3T3 Cells↗
PubMed1998

Murine cytomegalovirus induces a Sjögren's syndrome-like disease in C57Bl/6-lpr/lpr mice.

OBJECTIVE: To analyze Fas and tumor necrosis factor receptor I (TNFRI) apoptosis pathways in salivary gland inflammatory disease induced by murine cytomegalovirus (MCMV) infection. METHODS: Four different strains of mice (C57BI/6 [B6]-+/+, Fas-deficient B6-lpr/lpr, TNFRI-deficient B6-tnfr1(0/0), and B6-tnfr1(0/0)-lpr/lpr mice) were infected intraperitoneally with the Smith strain of MCMV (1 x 10(5) plaque-forming units). Viral load was determined by a plaque assay, inflammation and apoptosis by immunohistochemistry and staining with terminal dUTP nickend labeling, and autoantibodies by enzyme-linked immunosorbent assay. RESULTS: Infectious MCMV was not detectable by day 100. Although all MCMV-infected mice developed acute sialadenitis by day 28, a chronic (>100 days), severe salivary gland inflammation and anti-Ro and anti-La antibodies developed only in the B6-lpr/lpr mice. Apoptotic cells were detected during the acute, but not the chronic, phase of inflammation. CONCLUSION: Both Fas- and TNFRI-mediated apoptosis contribute to the clearance of MCMV-infected cells in the salivary glands. However, because Fas-mediated apoptosis is necessary for the down-modulation of the immune response, a defect in this process can lead to a postinfection, chronic inflammatory response that resembles Sjögren's syndrome.

Animals↗
PubMed2001

Treatment of chronic sialadenitis in a murine model of Sjögren's syndrome by local fasL gene transfer.

OBJECTIVE: Infection of Fas (Fas/CD95)-mutant C57BL/6 (B6)-lpr/lpr mice with murine cytomegalovirus (MCMV) leads to a chronic sialadenitis similar to that of Sjögren's syndrome (SS). The aim of this study was to evaluate whether chronic sialadenitis would also occur in Fas ligand (FasL/CD95L)-mutant B6-gld/gld mice upon infection with MCMV and whether the expression of FasL by local gene transfer using recombinant adenoviral vectors would be an effective therapeutic strategy. METHODS: B6-gld/gld mice were infected intraperitoneally with MCMV, and salivary glands were analyzed histologically at different time points. For treatment of sialadenitis, recombinant adenoviral vectors expressing the fasL gene (AdLoxpFasL + AxCANCre) or the lacZ gene (AdCMVLacZ) were locally injected into the salivary glands of MCMV-infected B6-gld/gld mice and uninfected B6-+/+ and B6-gld/gld mice. RESULTS: Following MCMV infection, B6-gld/gld mice developed an acute and chronic sialadenitis characterized by multiple foci of infiltrating T cells. After local injection of adenoviral vectors, high levels of lacZ or fasL gene expression could be detected in acinar and ductal cells. Treatment of acute and chronic sialadenitis in B6-gld/gld mice with local fasL gene transfer resulted in a significant reduction in the number of inflammatory foci and tissue destruction in salivary glands compared with mice treated with AdCMVLacZ. Despite high levels of FasL expression after injection of recombinant vectors, <5% of ductal and acinar cells were TUNEL positive, demonstrating that, in this model of SS, acinar and ductal cells were not highly sensitive to FasL-mediated apoptosis. CONCLUSION: Chronic sialadenitis similar to that of SS developed in B6-gld/gld mice after MCMV infection. FasL expression was reconstituted by local gene transfer, resulting in significant reduction of infiltrating mononuclear cells, which indicates that local gene transfer of fasL might be a novel treatment for chronic sialadenitis.

Animals↗
PubMed2006

Mouse embryonic stem cells are not susceptible to cytomegalovirus but acquire susceptibility during differentiation.

BACKGROUND: Cytomegalovirus (CMV) is the most significant infectious cause of congenital anomalies of the central nervous system caused by intrauterine infection in humans. The timing of infection and the susceptibility of cells in early gestational stages are not well understood. In this study we investigated the susceptibility of embryonic stem (ES) cells to CMV infection during differentiation. METHODS: ES cell lines were established from transgenic mice integrated with the murine CMV (MCMV) immediate-early (IE) promoter connected with a reporter lacZ gene. The susceptibility of the ES cells was analyzed in terms of viral gene expression and viral replication after induction of differentiation. RESULTS: ES cells were nonpermissive to MCMV infection in the undifferentiated state. Upon differentiation, permissive cells appeared approximately 2 weeks after the leukemia inhibitory factor was removed. Upon neural differentiation by retinoic acid (RA), glial cells showed specific susceptibility in terms of expression of the viral antigen. The MCMV IE promoter was not activated in ES cells from the transgenic mice. Activation of the IE promoter was detected approximately 2 weeks after induction of differentiation and observed predominantly in glial cells. Upon MCMV infection of the ES cells, viral infection was correlated with the activation of the IE promoter. CONCLUSIONS: ES cells are nonpermissive to MCMV infection and acquire permissiveness about 2 weeks after induction of differentiation, especially in glial cells. Acquisition of permissiveness in differentiated ES cells may be associated with activation of the IE promoter.

Animals↗
PubMed2004

Hepatic dendritic cell subsets in the mouse.

The CD11c(+) cell population in the non-parenchymal cell population of the mouse liver contains dendritic cells (DC), NK cells, B cells and T cells. In the hepatic CD11c(+) DC population from immunocompetent or immunodeficient [recombinase-activating gene-1 (RAG1)(-/-)] C57BL/6 mice (rigorously depleted of T cells, B cells and NK cells), we identified a B220(+) CD11c(int) subset of 'plasmacytoid' DC, and a B220(-) CD11c(+) DC subset. The latter DC population could be subdivided into a major, immature (CD40(lo) CD80(lo) CD86(lo) MHC class II(lo)) CD11c(int) subset, and a minor, mature (CD40(hi) CD80(hi) CD86(hi) MHC class II(hi)) CD11c(hi) subset. Stimulated B220(+) but not B220(-) DC produced type I interferon. NKT cell activation in vivo increased the number of liver B220(-) DC three- to fourfold within 18 h post-injection, and up-regulated their surface expression of activation marker, while it contracted the B220(+) DC population. Early in virus infection, the hepatic B220(+) DC subset expanded, and both, the B220(+) as well as B220(-) DC populations in the liver matured. In vitro, B220(-) but not B220(+) DC primed CD4(+) or CD8(+)T cells. Expression of distinct marker profiles and functions, and distinct early reaction to activation signals hence identify two distinct B220(+) and B220(-) subsets in CD11c(+) DC populations freshly isolated from the mouse liver.

Animals↗
PubMed2005

Evolution of diverse antiviral CD8+ T cell populations after murine cytomegalovirus infection.

Cytomegalovirus (CMV) is a major human pathogen normally controlled by cellular immune responses. The infection can be modeled in the mouse using murine CMV (MCMV). During the latent phase of infection, two different patterns of CD8(+) T cell responses have been observed: some specificities show increasing frequencies over time ("memory inflation"), while others, which are present acutely, are barely detectable at later time points. This distinction is independent of initial immunodominance. We analyzed the extent to which such responses differ functionally and tracked both their population distribution and their evolution over time. We observed two clear patterns of memory development that diverged early after infection. Acutely, CD8(+) T cells directed against all epitopes showed similar activation, phenotype and distribution. Thereafter, one set of responses ("inflationary") increased in frequency over time, was found in high numbers in non-lymphoid organs and was associated with an activated (CD28(low) CD27(low)CD122(low)) phenotype. In contrast, CD8(+) T cells responses specific for other MCMV epitopes ("non-inflationary") showed a slow reversion to a classical "central" memory phenotype without enrichment in non-lymphoid organs. A simple model to describe the equilibrium state in MCMV is presented, which may point to previously unexplored antiviral populations present after human CMV infection.

Animals↗
PubMed2005

Direct effects of T-bet and MHC class I expression, but not STAT1, on peripheral NK cell maturation.

The homeostatic maturation of NK cells is severely impaired in mice lacking the transcription factor T-bet, and the expression of the NK cell maturation marker killer cell lectin-like receptor G1 (KLRG1) has been shown to be dependent on MHC class I molecules. Interferon (IFN)-gamma signaling via the signal transducer and activator of transcription (STAT)1 is vital for T-bet and MHC class I induction. Here we investigated the relationship between STAT1, T-bet, and MHC class I molecules with regard to the phenotypic maturation of peripheral NK cells. We demonstrate that, to varying degrees, the maturation status of peripheral NK cells is impaired in naive mice with deficiencies in STAT1, T-bet, or MHC class I molecules. We find that in naive animals, the expression of wild-type levels of MHC class I molecules in trans is sufficient to restore the maturation profiles of STAT1(-/-) NK cells in vivo. In contrast, expression of T-bet is required in cis for normal NK cell maturation to occur. Additionally, we demonstrate that the activation-induced maturation of NK cells during the course of murine cytomegalovirus (MCMV) infection does not require expression of MHC class I molecules or STAT1 but is severely delayed in the absence of T-bet.

Animals↗
PubMed2001

Activation of murine cytomegalovirus immediate-early promoter in cerebral ventricular zone and glial progenitor cells in transgenic mice.

Cytomegalovirus (CMV) is the most common infectious cause of congenital anomalies of the CNS in humans. We recently reported that the murine cytomegalovirus (MCMV) immediate-early (IE) gene promoter directs astrocyte-specific expression in adult transgenic mice. In the present study, we analyzed the activation of the MCMV IE promoter in developing transgenic mouse brains and compared the activation with that of the Musashi 1 (Msi1) gene, which is expressed in neural progenitor cells, including neural stem cells. During the early phase of neurogenesis, the transgene was expressed predominantly in endothelial cells of the vessels, but not in neuroepithelial cells in which Msi1 was expressed. During later stages of gestation, expression of the transgene was largely restricted to the ventricular zone (VZ) in the CNS, similar to the expression of Msi1. In neurosphere cultures from transgenic embryos in the late phase of neurogenesis, the transgene was expressed in some cells of neurospheres expressing Msi1 and nestin. In neural precursor cells induced to differentiate from stem cells, expression of the transgene was detected in glial progenitor cells, expressing GFAP, nestin, and Msi1, but not in cells expressing MAP2 or MAG. In postnatal development, persistent expression of the transgene was observed in astrocyte lineage cells as was Msi1. These spatiotemporal changes of the MCMV IE promoter activity during development of transgenic mice correlated with susceptible sites in congenital HCMV infection. Moreover, this transgenic mouse model may provide useful model for analysis of the regulation of the switching of neuronal and astrocyte differentiation, and the maintenance of the astrocyte lineage.

Animals↗
PubMed2006

STAT1 contributes to dsRNA inhibition of liver regeneration after partial hepatectomy in mice.

Increasing evidence suggests that liver regeneration is suppressed in patients with chronic HCV infection; however, the underlying mechanisms remain unclear. Previously, we demonstrated that injection of the synthetic double-stranded RNA (dsRNA) poly I:C to mimic viral infection suppresses liver regeneration in the partial hepatectomy (PHx) model, whereby IFN-gamma contributes to the inhibition. In this study, we examined the role of the IFN-gamma-activated downstream signal (STAT1) and genes (IRF-1, p21(cip1), and SOCS1) in liver regeneration and hepatocyte proliferation. Results show that disruption of the STAT1 gene abolished poly I:C suppression of liver regeneration and the inhibitory effect of poly I:C on liver regeneration was diminished in IRF-1(-/-) and p21(cip1-/-)mice. Treatment with IFN-gamma in vitro inhibited cell proliferation of wild-type mouse hepatocytes, but not STAT1(-/-) hepatocytes. The inhibitory effect of IFN-gamma on cell proliferation was also diminished in IRF-1(-/-) and p21(cip1-/-) hepatocytes, but enhanced in SOCS1(-/-) hepatocytes. Hepatocyte proliferation was unaffected by treatment with poly I:C alone, but when hepatocytes were co-cultured with liver lymphocytes, proliferation was inhibited by IFN-gamma/STAT1-dependent mechanisms. Moreover, in HCV-infected livers with cirrhosis, activation of STAT1 was detected and correlated positively with liver injury (elevated serum levels of AST) but negatively with hepatocyte proliferation (hepatocyte PCNA and Ki-67 positive immunostaining). In conclusion, STAT1 is involved in dsRNA suppression of liver regeneration; not only does STAT1 activation contribute to liver injury, it may also block liver repair through inhibition of hepatocyte proliferation in HCV-infected patients, playing an important role in the pathogenesis of disease.

Animals↗
PubMed2003

High-frequency interferon-gamma-secreting splenocytes specific for murine cytomegalovirus immediate-early-1 (IE-1) peptide 168YPHFMPTNL176 are insufficient to provide complete protection from viral challenge.

Infection of Balb/c mice with murine cytomegalovirus (MCMV) has been used extensively as a model system with which to study host mechanisms of immunity to cytomegaloviruses. In this model, the cytotoxic T-lymphocyte (CTL) response crucial for clearing infected cells is dominated by CTLs specific for the MCMV nonapeptide 168YPHFMPTNL176 encoded by the immediate-early 1 (IE-1) gene. The intradermal injection of plasmid pcDNA89 encoding IE-1 has been shown to offer some protection from viral challenge. In the present studies, the protective efficacy of immunisation with pcDNA89 given by intradermal injection was compared with particle-mediated DNA delivery (PMDD) and contrasted with that induced by injection with the K181 MCMV strain and with temperature-sensitive mutants (tsm) derived from the K181 strain. Modest protection was afforded by pcDNA89 immunisation given by PMDD, but none was observed after intradermal injection. PMDD immunisation induced a frequency of 168YPHFMPTNL176-specific interferon-gamma (IFN-gamma)-secreting splenocytes, which was equivalent to that after K181 infection and significantly higher than tsm immunisation. Whereas tsm-immunised mice were completely protected from MCMV challenge, PMDD-immunised mice were only weakly protected. Tsm immunisation protected mice completely against challenge with natural isolates having sequence variation in the IE-1 nonapeptide, while PMDD-immunised mice were weakly protected from isolates encoding 168YPHFMPTNL176 and were not protected against isolates encoding 168YPHFMPPSL176 or 168YLDFMPPNL176. Thus, while IE-1-specific IFN-gamma-secreting splenocytes do contribute to immunity from MCMV challenge, their presence in isolation is insufficient to provide complete protection and they may not be involved in the protection observed against MCMV isolates having IE-1 sequence variation.

3T3 Cells↗
PubMed1994

Studies of the pathogenesis of wild-type virus and six temperature-sensitive mutants of mouse cytomegalovirus.

A comparison of six temperature-sensitive (ts) mutants with the parental wild-type (wt) virus showed that, when 1-week-old BALB/c mice were inoculated intraperitoneally with 300 pfu of mouse passaged virus, the viruses could be broadly categorized into two groups. Two viruses (wt and tsm6) were lethal at this dose (10 and 2 LD50 respectively); animals died within 4-6 days of inoculation and the virus became generalized infecting heart, lung, liver, spleen, kidney, and salivary glands to high titre (> 4.3 log10 pfu/g). In contrast, for viruses (tsm1, tsm3, and tsm4) not lethal at this dose (300 pfu = 0.1 to 0.25 LD50), viral replication was poor (< 3.4 log10 pfu/g) except in the salivary glands (5.6 to 7.5 log10 pfu/g). Mutant tsm5 failed to replicate in any tissue while mutant tsm2, lethal at this dose (300 pfu = 1 LD50), produced levels of virus similar to those found with tsm1, tsm3, and tsm4. Comparison of all viruses at sub-lethal doses (0.1 to 0.25 LD50) did show minor differences in their replication in heart, and in levels of virus and duration of infection in kidney and salivary glands. More marked differences were evident between the viruses in their ability to be reactivated from the latent state during immunosuppression. Wild-type virus was most easily reactivated in that 67% of animals exhibited virus in salivary glands, heart, lung, spleen, and kidney. Mutants tsm1, tsm2, tsm3 and tsm6 could be reactivated but from fewer animals (33%, 33%, 18%, and 38% respectively) and fewer tissues. Mutants tsm4 and tsm5 could not be reactivated. Differences in the ability of the viruses to replicate in the lungs and to cause pneumonitis in intranasally-inoculated immunosuppressed mice were also seen. Although immunosuppression was necessary for the induction of severe pneumonitis, differences in severity of pneumonitis resulted from differences in the ability of the mutants to replicate in the lung in vivo. These different mutants should prove useful for examining the viral and host factors involved in CMV-induced pneumonitis, and for examining mechanisms involved in latency and reactivation.

Animals↗
PubMed1995

Pathogenesis of ocular cytomegalovirus infection in the immunocompromised host.

Balb/C nude and C.B-17 SCID mice were inoculated with salivary gland passaged cytomegalovirus (SG-MCMV) intraperitoneally. Dissemination of the virus in the systemic and ocular tissues was studied by the direct immunofluorescence test, and the virus growth in each tissue was titrated in mouse embryonic fibroblasts. The mode of viral spread was assessed by inhibiting macrophage function by silica and administering polyclonal murine anti-MCMV antibody in the circulation. The virus first reached the eyelid, conjunctiva, and cornea. Subsequently, it spread in the outer ocular muscles and chorioretinal layer. Ocular tissues were involved as part of a generalized infection. Abrogation of macrophage function by silica did not affect the outcome of the viral distribution. Administration of antibody prior to and 3 days after the viral infection prevented virus dissemination. Ocular CMV infection occurred initially at the anterior segment of the eye in an immunocompromised host. Free virus, not macrophage-bound virus, disseminated via the bloodstream.

Animals↗