SOCS3 expression correlates with severity of inflammation in mouse hepatitis virus strain 3-induced acute liver failure and HBV-ACLF / 华中科技大学学报（医学）（英德文版）

Recently, suppressor of cytokine signaling-3 (SOCS3) has been shown to be an inducible endogenous negative regulator of Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway which is relevant in inflammatory response, while its functions in acute liver failure and HBV-induced acute-on-chronic liver failure (HBV-ACLF) have not been fully elucidated. In this study, we explored the role of SOCS3 in the development of mouse hepatitis virus strain 3 (MHV-3)-induced acute liver failure and its expression in liver and peripheral blood mononuclear cells (PBMCs) of patients with HBV-ACLF. Inflammation-related gene expression was detected by real-time PCR, immunohistochemistry and Western blotting. The correlation between SOCS3 level and liver injury was studied. Our results showed that the SOCS3 expression was significantly elevated in both the liver tissue and PBMCs from patients with HBV-ACLF compared to mild chronic hepatitis B (CHB). Moreover, a time course study showed that SOCS3 level was increased remarkably in the liver of BALB/cJ mice at 72 h post-infection. Pro-inflammatory cytokines, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, were also increased significantly at 72 h post-infection. There was a close correlation between hepatic SOCS3 level and IL-6, and the severity of liver injury defined by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, respectively. These data suggested that SOCS3 may play a pivotal role in the pathogenesis of MHV-3-induced acute liver failure and HBV-ACLF.

CD69+NK cells contribute to the murine hepatitis virus strain 3-induced murine hepatitis / 华中科技大学学报（医学）（英德文版）

The role of hepatic CD69+ natural killer (NK) cells in virus-induced severe liver injury and subsequent hepatic failure is not well defined. In this study, a mouse model of fulminant liver failure (FHF) induced by murine hepatitis virus strain 3 (MHV-3) was used to study the role of hepatic CD69+NK cells in the development of FHF. The CD69 expression in NK cells in the liver, spleen, bone marrow and peripheral blood was detected by using flow cytometry. The correlation between the CD69 level in hepatic NK cells and liver injury was studied. The functional marker (CD107a), and activating and inhibitory receptor (NKG2D and NKG2A) expressed on CD69+NK cells and CD69-NK cells were detected by using flow cytometry. Pro-inflammatory cytokines (IL-9, IFN-γ and TNF-α) were also examined by using intracellular staining. After MHV-3 infection, the number of CD69+NK cells in the liver of BALB/cJ mice was increased markedly and peaked at 72 h post-infection. Similar changes were also observed in the spleen, bone marrow and peripheral blood. Meanwhile, the CD69 expression in hepatic NK cells was highly correlated with the serum level of ALT and AST. The expression of CD107a and NKG2D, as well as the production of TNF-α, IFN-γ and IL-9 in hepatic CD69+NK cells was all significantly up-regulated during 48-72 h post-infection. In contrast, the NKG2A expression was increased in hepatic CD69-NK cells but not in CD69+NK cells. These results suggested that hepatic CD69+NK cells play a pivotal role in the pathogenesis of FHF by enhancing degranulation and cytotoxic ability of NK cells and increasing the production of pro-inflammatory cytokines.

Contribution of IL-17 to mouse hepatitis virus strain 3-induced acute liver failure / 华中科技大学学报（医学）（英德文版）

Recently, the Th17 cells and IL-17 have been shown to play a critical role in the immune-mediated liver injury in hepatitis B, while their functions in acute liver failure have not been well elucidated yet. In this study, we primarily investigated the role of IL-17 in the development of mouse hepatitis virus strain 3 (MHV-3)-induced acute liver failure. IL-17 mRNA levels in liver tissue were quantified by using quantitative real-time polymerase chain reaction, and cytokine IL-17 levels in liver tissue and serum were determined by using ELISA in MHV-3-induced murine fulminant hepatitis model. The IL-17 expression levels on CD4(+)T and CD8(+)T cells were determined by using flow cytometry. The correlation between IL-17 level and liver injury was studied. Th17 associated cytokines were also investigated by intracellular staining. Our results showed that the IL-17 expression was significantly elevated in the liver and serum of BALB/cJ mice infected with MHV-3. Moreover, a time course study showed that the percentage of both IL-17-producing CD4(+)T cells and IL-17-producing CD8(+)T cells was increased remarkably in the liver starting from 48 h and peaked at 72 h post-infection. There was a close correlation between hepatic or serum IL-17 concentration and the severity of liver injury defined by ALT level, respectively. Th17 associated cytokines, IL-6, IL-21 and IL-22, were also increased significantly at 72 h post-infection. It was concluded that IL-17 may contribute to the pathogenesis of MHV-3-induced acute liver failure.

Establishment of a murine model of hepatic steatosis induced by chronic viral hepatitis / 南方医科大学学报

<p><b>OBJECTIVE</b>To establish a animal model of hepatic steatosis induced by chronic viral hepatitis in C(57)BL/6 mice.</p><p><b>METHODS</b>C(57)BL/6 mice were randomly assigned to control group, high-fat diet group, mouse hepatitis virus strain A59 (MHV-A59) virus infection group, and high-fat diet plus virus infection group. At 13 weeks of the experiment, serum samples were collected to detect MHV antibodies and transaminase and lipid levels. The hepatic pathologies of the mice were examined with Oil red O staining of the frozen sections the and HE staining of paraffin-embedded sections.</p><p><b>RESULTS</b>The mice in the two virus infection groups showed strong positivity of MHV antibodies in the serum. Compared with the control group, the mice in high-fat diet group and the two virus infection groups had significantly increased AST and ALT levels with also elevated TC and LDL-C levels. The two virus infection groups both exhibited obvious pathologies in the liver characteristic of chronic viral hepatitis with increased lipid accumulation in the hepatocytes.</p><p><b>CONCLUSION</b>We have successfully established a mouse model of hepatic steatosis induced by chronic viral hepatitis, which provides the basis for further study of the disease mechanism.</p>

KCTD9, a novel potassium channel related gene, was highly expressed in hepatic NK cells and T cells of fulminant hepatitis mice induced by MHV-3 / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To explore the mechanisms of a novel potassium channel gene named KCTD9 (potassium channel tetramerization domain containing 9) in model of fulminant viral hepatitis induced by murine hepatitis virus 3 (MHV-3).</p><p><b>METHODS</b>78 BALB/cJ mice(6 male) were randomly and equally assigned to two groups, model group of fulminant viral hepatitis induced by MHV3 and its control. 75 C3H/HeJ female mice were done into two groups, 39 for model group of chronic hepatitis induced by MHV3, 36 for control. Various samples including spleen, liver and lymphocytes from mice of two model groups and the controls were examined for KCTD9 expression by real time quantitative PCR and Immunohistochemistry. Independent-samples T test or one-way ANOVA were carried out in different groups.</p><p><b>RESULTS</b>Increased expressions of KCTD9 mRNA was observed in livers of both model mice of fulminant viral hepatitis and chronic hepatitis. Compared with the control mice, the expressions of KCTD9 mRNA were up-regulated by 577.1-, 8.8-, 59.4- and 10.8-fold in hepatic NK cells, CD4+ T cells, CD8+ T cells and splenic NK cells respectively in model mice of fulminant viral hepatitis 48 hr post MHV-3 infection, whereas down-regulation by 43% and 69% in splenic CD4 + T cells and CD8+ T cells were found respectively. In contrast, in model mice of chronic viral hepatitis the expressions of KCTD9 mRNA were down-regulated by 71% and 51% in hepatic CD4+ T cells and NK cells, respectively. The expression of KCTD9 protein was mainly evidenced in infiltrative mononuclear cells of liver as shown by immunohistochemistry. Basal expression was also investigated and showed constitutive expression of KCTD9 in brain, thymus and other organs in BALB/cJ mice.</p><p><b>CONCLUSION</b>A novel potassium channel gene KCTD9 was highly expressed in hepatic NK cells and T cells of fulminant hepatitis mice induced by MHV-3.</p>

Construction of MHV-A59 damp-heat mouse model and analysis of the relevant indices / 南方医科大学学报

<p><b>OBJECTIVE</b>To explore the impact of inflammation, water metabolism and immune function on the establishment of a mouse model of damp-heat syndrome with MHV-A59 infection.</p><p><b>METHODS</b>Twenty-four mice were randomly divided into control group, virus group, damp-heat group and model group. The peripheral blood CD4(+) and CD8(+) lymphocytes were detected by flow cytometry, and the serum levels of IFN-γ and IL-4 were assayed by ELISA. The expressions of NF-κB and AQP4 in the liver and stomach were determined using immunohistochemistry.</p><p><b>RESULTS</b>The expression of NF-κB and CD4(+)/CD8(+) ratio in the virus and model groups were significantly higher than those in the damp-heat and control groups, while the expression of AQP4 was significantly higher in the model and damp-heat groups than in the other groups. Compared with the control group, the model group showed a significantly higher ratio of IFN-γ/IL-4.</p><p><b>CONCLUSIONS</b>MHV-A59 virus is the main cause of elevated NF-κB expression and CD4(+)/CD8(+)/ ratio, while damp-heat syndrome is responsible for increased AQP4 expression, and their synergistic effect results in increased IFN-γ/IL-4 ratio. The mouse model established using MHV-A59 virus and the damp-heat factors can mimic damp-heat syndrome described in traditional Chinese medicine theory.</p>

Microbiological Contamination of Laboratory Mice and Rats in Korea from 2007 to 2008 / 한국실험동물학회지

In order to assess the microbiological contamination of laboratory mice and rats in Korea over the 2-year period from 2007 to 2008, we monitored animals housed in mouse and rat facilities equipped with barrier systems. In a barrier animal facility in Korea, the most important viruses in the identified pathogen were the mouse hepatitis virus (MHV) and Pasteurella (Pa.) pneumotropica, and Staphylococcus aureus was identified as the most common bacterial pathogen in Korea. The most commonly detected parasite in the identified pathogen was Trichomonas spp. in the mouse facilities and Entamoeba spp. in the rat facilities. In many cases, these pathogen-contaminated animals were genetically modified animals obtained from the university. Currently, consistent with the increased transfer of genetically modified animals between domestic and foreign animal facilities, the Pa. pneumotropica and parasites infection rates were shown to have increased as compared to those of the 2004-2006 period. Indeed, the MHV infection rate has been maintained at almost 20% in Korean animal facilities over the past 10 years. These results showed that effective quarantine programs for contaminated genetically engineered mutant mice and the monitoring of regular or irregular MHV monitoring in animal colonies should help to reduce pathogen contamination in Korean animal facilities.

Microbiological Contamination of Laboratory Mice and Rats in Korea from 2007 to 2008 / 한국실험동물학회지

In order to assess the microbiological contamination of laboratory mice and rats in Korea over the 2-year period from 2007 to 2008, we monitored animals housed in mouse and rat facilities equipped with barrier systems. In a barrier animal facility in Korea, the most important viruses in the identified pathogen were the mouse hepatitis virus (MHV) and Pasteurella (Pa.) pneumotropica, and Staphylococcus aureus was identified as the most common bacterial pathogen in Korea. The most commonly detected parasite in the identified pathogen was Trichomonas spp. in the mouse facilities and Entamoeba spp. in the rat facilities. In many cases, these pathogen-contaminated animals were genetically modified animals obtained from the university. Currently, consistent with the increased transfer of genetically modified animals between domestic and foreign animal facilities, the Pa. pneumotropica and parasites infection rates were shown to have increased as compared to those of the 2004-2006 period. Indeed, the MHV infection rate has been maintained at almost 20% in Korean animal facilities over the past 10 years. These results showed that effective quarantine programs for contaminated genetically engineered mutant mice and the monitoring of regular or irregular MHV monitoring in animal colonies should help to reduce pathogen contamination in Korean animal facilities.

Structures of the N- and C-terminal domains of MHV-A59 nucleocapsid protein corroborate a conserved RNA-protein binding mechanism in coronavirus

Coronaviruses are the causative agent of respiratory and enteric diseases in animals and humans. One example is SARS, which caused a worldwide health threat in 2003. In coronaviruses, the structural protein N (nucleocapsid protein) associates with the viral RNA to form the filamentous nucleocapsid and plays a crucial role in genome replication and transcription. The structure of N-terminal domain of MHV N protein also implicated its specific affinity with transcriptional regulatory sequence (TRS) RNA. Here we report the crystal structures of the two proteolytically resistant N- (NTD) and C-terminal (CTD) domains of the N protein from murine hepatitis virus (MHV). The structure of NTD in two different crystal forms was solved to 1.5 Å. The higher resolution provides more detailed structural information than previous reports, showing that the NTD structure from MHV shares a similar overall and topology structure with that of SARS-CoV and IBV, but varies in its potential surface, which indicates a possible difference in RNA-binding module. The structure of CTD was solved to 2.0-Å resolution and revealed a tightly intertwined dimer. This is consistent with analytical ultracentrifugation experiments, suggesting a dimeric assembly of the N protein. The similarity between the structures of these two domains from SARS-CoV, IBV and MHV corroborates a conserved mechanism of nucleocapsid formation for coronaviruses.

Role of CD4-CD8- T cells in the murine hepatitis virus type 3 induced chronic viral hepatitis / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To investigate role of CD4-CD8- T cells in murine hepatitis virus type 3 (MHV-3) induced chronic viral hepatitis in C3H/Hej mice and to identify their surface markers.</p><p><b>METHODS</b>Thirty C3H/Hej mice received 10 Pfu MHV-3 intraperitoneally, the CD4-CD8- T cells were isolated using magnetic bead sorting on 0, 4, 15, 30, 40 days post MHV-3 infection. The cytotoxic effects of CD4-CD8- T cells on normal and infected hepatocytes, CD8+ T cells and unrelated-virus (murine cytomegalovirus, MCMV) infected CD8+ T cells were examined by non-radioactive cytotoxicity assay. The surface markers of CD4-CD8- T cells were determined by flow cytometry.</p><p><b>RESULTS</b>MHV-3 infected CD4-CD8- T cells showed significant cytotoxic effect on CD8+ T cells, but not on infected hepatocytes or MCMV infected CD8+ T cells. The analysis of cell surface markers demonstrated that the CD4-CD8- T cells are a completely new T cell subset.</p><p><b>CONCLUSIONS</b>CD4-CD8- T cells have significant cytotoxic effect on virus specific CD8+ T cells in MHV-3 infected C3H/Hej mice, which suggests that CD4-CD8- T cells have immune modulatory functions in the development of chronic viral hepatitis. The phenotype of these CD4-CD8- T cells detected by flow cytometry is TCR alpha beta +CD3+CD4- CD8- CD25- CD28- CD30- CD44+.</p>

The functions of liver natural killer cells in murine fulminant hepatitis induced by murine hepatitis virus strain 3 / 中华肝脏病杂志

<p><b>OBJECTIVES</b>To investigate the role of liver natural killer cells (NK cells) in murine hepatitis virus strain 3 (MHV-3) induced murine fulminant hepatitis.</p><p><b>METHOD</b>Balb/cJ mice (6-8 weeks, female) were intraperitoneally injected with 100 PFU MHV-3. The numbers of NK cells in their livers, spleens, blood and bone marrow and the expression of CD69 on liver NK cells at 0, 24, 48 and 70 h after MHV-3 infection were analyzed by flow cytometry. The cytotoxic activity of liver NK cells was detected by a non-radioactive cytotoxicity assay. The levels of IFN gamma produced by hepatic NK cells were detected by intracellular cytokine staining.</p><p><b>RESULT</b>Following MHV-3 infection, the proportion of liver NK cells in the mice increased remarkably and reached the peak (43.9%+/-2.3%) at 48 h, then kept a high proportion until the mice were sacrificed. The proportion of NK cells in the peripheral blood also significantly increased and reached the peak (18.0%+/-5.4%) at 48 h. However, there were few NK cells in the peripheral blood at 70 h after infection; the ratio was only 1.3%+/-0.6%. In the spleens and bone marrow, the proportions of NK cells were both significantly decreased from 0 h to 48 h and then slightly increased. The expression of CD69 on liver NK cells was highly up-regulated after the infection and the cytotoxic activity of hepatic NK cells at 48 h was also significantly enhanced. In addition, an increase in IFN gamma production by hepatic NK cells was observed at 48 h.</p><p><b>CONCLUSION</b>After MHV-3 infection, NK cells were recruited to the liver quickly, probably from the spleen and bone marrow. Recruited NK cells remarkably express CD69, enhance cytotoxic activity and IFN gamma production, which correlate with the disease severity of fulminant viral hepatitis. Our results suggest that liver NK cells may play a pivotal role in the pathogenesis of fulminant viral hepatitis.</p>

Differential gene expression profiles in acute hepatic failure model in mice infected with MHV-3 virus intervened by anti-hepatic failure compound / 华中科技大学学报（医学）（英德文版）

Differential gene expression profiles in Balb/cJ mouse model of acute hepatic failure infected with MHV-3 virus intervened by anti-hepatic failure compound (AHFC) and the changes of cytokines regulated by genes were investigated. The Balb/cj mice were divided into AHFC-intervened group and control group randomly. Acute hepatic failure model of Balb/cJ mice infected with MHV-3 virus was established. The survival rate in the two groups was observed. It was found that the survival rate in the AHFC-intervened group and control group was 90% and 50% respectively 48 h after intraperitoneal injection of MHV-3 (P<0.05). Before and after the experiment, the cytokines in peripheral blood of the survival mice were determined, and RNA was extracted from survival mouse liver tissue for the analysis of the differential gene expression by a 36 kb mouse oligonucleotide DNA array. In all the genes of microarray there were 332 genes expressed differently in the two groups, in which 234 genes were up-regulated and 78 genes down-regulated. Through clustering analysis, the differential expression of immune related genes, including TNF receptor superfamily, Kctd9, Bcl-2, Fgl2, IL-8, IL-6, IFN-gamma, TNF-alpha etc. might be related with the curative effectiveness of AHFC. It was suggested that AHFC can balance the immune state of mouse model of acute hepatic failure infected with MHV-3 virus mainly through regulating the expression of immune related genes, decrease the immune damage and inhibit liver cell apoptosis of mouse acute hepatic failure model obviously so as to increase the survival rate of mouse models of acute hepatic failure.

Gene expression in IFN-gamma-activated murine macrophages

Macrophages are critical for natural immunity and play a central role in specific acquired immunity. The IFN-gamma activation of macrophages derived from A/J or BALB/c mice yielded two different patterns of antiviral state in murine hepatitis virus 3 infection, which were related to a down-regulation of the main virus receptor. Using cDNA hybridization to evaluate mRNA accumulation in the cells, we were able to identify several genes that are differently up- or down-regulated by IFN-gamma in A/J (267 and 266 genes, respectively, up- and down-regulated) or BALB/c (297 and 58 genes, respectively, up- and down-regulated) mouse macrophages. Macrophages from mice with different genetic backgrounds behave differently at the molecular level and comparison of the patterns of non-activated and IFN-gamma-activated A/J or BALB/c mouse macrophages revealed, for instance, an up-regulation and a down-regulation of genes coding for biological functions such as enzymatic reactions, nucleic acid synthesis and transport, protein synthesis, transport and metabolism, cytoskeleton arrangement and extracellular matrix, phagocytosis, resistance and susceptibility to infection and tumors, inflammation, and cell differentiation or activation. The present data are reported in order to facilitate future correlation of proteomic/transcriptomic findings as well as of results obtained from a classical approach for the understanding of biological phenomena. The possible implication of the role of some of the gene products relevant to macrophage biology can now be further scrutinized. In this respect, a down-regulation of the main murine hepatitis virus 3 receptor gene was detected only in IFN-gamma-activated macrophages of resistant mice.

Targeted RNA recombination of the membrane and nucleocapsid protein genes between mouse hepatitis virus and bovine coronavirus

The targeted RNA recombination was attempted to substitute the membrane (M) protein gene and part of the nucleocapsid (N) protein gene of mouse hepatitis virus with the corresponding sequences from bovine coronavirus. Using a defective interfering (DI) RNA-like cDNA construct derived from pMH54, 690 nucleotides representing the entire M gene and the 5' most 915 nucleotides of the N gene of the mouse hepatitis virus Albany 4 mutant were attempted to be replaced. Upon infection of cells with Albany 4 followed by transfection with synthetic RNA transcribed from the DI-like cDNA construct, recombinant mouse hepatitis viruses as the large plaque forming phenotype were isolated by plaque assays at the non-permissive temperature of 391 degrees C. By RT-PCR and sequencing, those large plaque phenotypes were confirmed to have contained the thermostable phenotype marker derived from the transfected RNA, demonstrating that recombination occurred between the Albany 4 genomic RNA and the in vitro RNA transcripts. Further analysis of the recombinant viruses indicated that there combination had taken place within the region of 222 nucleotides between positions 916 and 1,137 of the N gene. This is the region immediately downstream of the replacement sequence and the start of the temperature resistant phenotype marker. The results suggest that the M and part of the N genes of bovine coronavirus may not be able to complement the function of those of mouse hepatitis virus. This study redirects our current approach of utilizing the MHV targeted RNA recombination as a means to study bovine coronavirus genetics towards the construction of an infectious cDNA clone.

Detecçäo do vírus da hepatite murina utilizando-se a reaçäo em cadeia pela polimerase / Detection of mouse hepatitis virus in mouse colonies using the nested polymerase chain reaction

Desenvolveu-se a técnica de transcriçäo reversa - reaçäo em cadeia pela polimerase para detectar o vírus da hepatite do camundongo em tecido hepático. Para se eliminar possíveis falhas na reaçäo de amplificaçäo RT-PCR usou-se um segundo ciclo de amplificaçäo com primers internos para confirmar a especificidade e aumentar a sensibilidade do teste. Após a optimizaçäo do protocolo, descreve-se a detecçäo da amplificaçäo específica da seqüência-alvo em camundongos de 18 das 20 colônias examinadas

Antiviral activity of interferon gamma in vivo during mouse hepatitis virus infection

A/J mice became resistant to experimental MHV3 infection after immunization with UV-inactivated MHV3 (0 percent mortality, 0/10). Depletion of interferon (IFN) gamma-producing CD4+ T lymphocytes with monoclonal antibodies to CD4+ led to susceptibility to virus infection (60 percent of mortality, 6/10). The resistance to MHV3 infection of CD4+ T lymphocyte-depleted-A/J mice was restored by treatment with 1000 U of IFN gamma on days -1, 0, 1, 2, 3 and 4 (10 percent of mortality, 1/10). The low virus titers observed in resistant mice (controls or CD4+ depleted plus IFN gamma treated) were cleared 6 days after infection and the virus titers observed among susceptible mice (CD4+ depleted) increased gradually and peaked on day 6, when the animals died. Previous data, taken together with the direct evidence presented in this paper, provide strong evidence supporting the concept of an in vivo antiviral role of IFN gamma through a central action on the mechanisms of resistance to MHV3 infection

Reduction of the accumulation of viral mRNA and of cellular rRNA synthesis in MHV3-infected macrophages of resistant mice

1. After MHV3 infection, only macrophages from resistant A/J mice partially restricted virus growth compared to those from susceptible BALB/c mice (2 logs of difference in virus titer). 2. Cellular ribosomal ribonucleic acid (rRNA) synthesis by MHV3-infected macrophages was decreased only in A/J mouse macrophages as indicated by accumulation of the 28S rRNA fraction. 3. The accumulation of viral messenger ribonucleic acids (mRNAs) in MHV3-infected macrophages was also reduced in A/J mouse macrophages compared to BALB/c mice. 4. In pulse-chase experiments of viral protein synthesis, the appearance, glycosylation and cleavage of glycoprotein S, as well as the metabolism of nucleoprotein N were delayed in A/J mouse macrophages. 5. These data show that MHV3 infection of A/J mouse macrophages induced an imbalanced accumulation of the 28S fraction of rRNA. Furthermore the synthesis of mRNAs correlated with viral protein synthesis in both A/J and BALB/c macrophages, but was delayed in A/J mice. 6. These results suggest that the partial restriction of MHV3 replication in macrophages of resistant A/J mice may take place during or before the mRNA synthesis, although it is correlated with the appearance, glycosylation, cleavage and metabolism of viral proteins

Mouse hepatitis virus 3 and interferon gamma binding to extracted macrophage proteins correlate with virus growth in A/J and BALB/c mice

1. After immunization, adult A/J mice are resistant and BALB/c mice are susceptible to MHV3 infection. After IFN gamma activation, only macrophages originating from A/J mice were able to partially restrict MHV3 growth. 2. When the binding of MHV3 and interferon (IFN) gamma to solubilized cytoplasmic and membrane macrophage proteins of mice was determined by ELISA, there was more binding of MHV3 to proteins extracted from BALB/c macrophages than to proteins extracted from A/J macrophages. When the proteins were obtained from IFN gamma-activated macrophages, decreased MHV3 binding was observed only in proteins originating from A/J macrophages. 3. ELISA showed a comparable binding of IFN gamma to A/J or BALB/c macrophage proteins. When the proteins were obtained from IFN gamma-activated macrophages, only IFN gamma-binding to A/J macrophage proteins was increased. 4. The results indicate a different expression and IFN gamma modulation of MHV3 receptors in macrophages from A/J and BALB/c mice, which directly correlated with their acquired resistance or susceptibility to MHV3 infection

A comparative study of resistance to MHV3 infection in genetically homogeneous and heterogeneous mouse populations

Resistance to MHV3 infection was investigated in genetically homogeneous inbred (A/J, BALB/c) and genetically selected (High, Low) mouse lines. The A/J and L lines are resistant and the BALB/c and H mice are susceptible. The genetic analysis was performed on the F1 hybrids, as well as on the genetically heterogeneous F2 populations and backcrosses bred from HxL and A/JxBALB/c lines. The mortality rates of the F1 hybrids showed codominance of susceptibility and resistance characters. The results indicate that the same MHV3 susceptibility genes are present in isogenic and selected lines and corroborate previous results showing that at least two major genes are involved in the control of this response