The effect of ghrelin on bursa and cecal tonsils of chickens infected with an attenuated virus strain of infectious bursal disease virus.

Infectious bursal disease (IBD) significantly affects the poultry industry, causing substantial economic losses. This study aimed to investigate the effects of ghrelin on chicks infected with an attenuated virus strain of IBDV (aIBDV). Chicks were divided into 3 groups: a control group (group I), an aIBDV infection group (group II), and a ghrelin + aIBDV infection group (group III). Mice in groups II and III were fed until they reached 19 d of age and then inoculated with aIBDV to establish a subclinical infection model. Group III received an intraperitoneal injection of 0.5 nmol/100 g ghrelin from d 17 to 23. The present study utilized paraffin sectioning, H&E staining, and immunohistochemical staining to examine the effects of ghrelin on the bursa of fabricius and cecum tonsils in aIBDV-infected chicks. The results indicated that at 3 d postinfection (dpi), the average body weight of group III was significantly greater than that of group II (P < 0.05). At 3 and 7 dpi, the proportion of large lymphoid follicles in the bursa of fabricius in group III was notably greater than that in group II (P < 0.05). aIBDV infection resulted in bleeding, edema, and fibrosis in the cecal mucosal layer of chicks, but ghrelin administration mitigated these pathological changes. At 3 and 7 dpi, the thickness of the lamina propria in the cecal tonsils of group III was significantly lower than that in the cecal tonsils of group II (P < 0.05). Additionally, the percentage of large lymphoid follicles in the cecal tonsils of group III was significantly greater than that in group II at 3 and 5 dpi (P < 0.05). There were significantly fewer macrophages in the cecal tonsils of group III than in those of group II at 1, 3, and 5 dpi (P < 0.05). In conclusion, ghrelin supplementation improved performance and mitigated bursal atrophy in aIBDV-infected chicks. It also reduced histological lesions and immune responses in the cecum tonsil. Notably, the reduction in macrophages in the cecum tonsil following ghrelin administration may decrease the risk of aIBDV spread.

Prevalence of murine astrovirus in laboratory animal facilities in Japan.

To investigate the prevalence of murine astrovirus (MuAstV) in mice in laboratory animal facilities in Japan, a polymerase chain reaction (PCR) test targeting the RNA-dependent RNA polymerase (RdRP) gene was performed on the cecum contents of 1,212 mice (1,183 immunocompetent mice and 29 immunodeficient mice) from 226 facilities. The results showed that 118 (52.2%) of the 226 facilities were positive for MuAstV. Out of the 1,212 mice, 424 (35.0%) were positive. No gross lesions were observed in any of the mice examined. A phylogenetic analysis for 15 selected strains revealed that 13 strains formed one cluster, while two were genetically distant from that cluster. These results suggest that multiple strains are prevalent in laboratory mice in Japan.

Porcine deltacoronavirus causes diarrhea in various ages of field-infected pigs in China.

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that causes acute diarrhea in suckling piglets. In Henan province of China, three swine farms broke out diarrhea in different ages of pigs during June of 2017, March of 2018 and January of 2019, respectively. PCR method, Taqman real-time RT-PCR method, sequencing, histopathology and immunohistochemistry (IHC) were conducted with the collected samples, and the results showed that PDCoV was detected among the suckling piglets, commercial fattening pigs and sows with diarrhea. PDCoV-infected suckling piglets were characterized with thin and transparent intestinal walls from colon to caecum, spot hemorrhage at mesentery and intestinal bleeding. PDCoV RNA was detected in multiple organs and tissues by Taqman real-time RT-PCR, which had high copies in ileum, inguinal lymph node, rectum and spleen. PDCoV antigen was detected in the basal layer of jejunum and ileum by IHC. In this research, we found that PDCoV could infect various ages of farmed pigs with watery diarrhea and anorexia in different seasons in a year.

Comparative evaluation of Salmonella Typhimurium vaccines derived from UK-1 and 14028S: Importance of inherent virulence.

The initial virulence and invasiveness of a bacterial strain may play an important role in leading to a maximally efficacious attenuated live vaccine. Here we show that χ9909, derived from Salmonella Typhimurium UK-1 χ3761 (the most virulent S. Typhimurium strain known to us), is effective in protecting mice against lethal UK-1 and 14028S (less virulent S. Typhimurium strain) challenge. As opposed to this, 14028S-derived vaccine χ12359 induces suboptimal levels of protection, with survival percentages that are significantly lower when challenged with lethal UK-1 challenge doses. T-cell assays have revealed that significantly greater levels of Th1 cytokines IFN-γ and TNF-α were secreted by stimulated T-lymphocytes obtained from UK-1(ΔaroA) immunized mice than those from mice immunized with 14028S(ΔaroA). In addition, UK-1(ΔaroA) showed markedly higher colonizing ability in the spleen, liver, and cecum when compared to 14028S(ΔaroA). Enumeration of bacteria in fecal pellets has also revealed that UK-1(ΔaroA) can persist in the host for over 10 days whereas 14028S(ΔaroA) titers dropped significantly by day 10. Moreover, co-infection of parent strains UK-1 and 14028S resulted in considerably greater recovery of the former in multiple mucosal and gut associated lymphatic tissues. Mice immunized with UK-1(ΔaroA) were also able to clear UK-1 infection remarkably more efficiently from the target organs than 14028S(ΔaroA). Together, these results provide ample evidence to support the hypothesis that attenuated derivatives of parent strains with higher initial virulence make better vaccines.

Microencapsulation with alginate/CaCO3: A strategy for improved phage therapy.

Bacteriophages are promising therapeutic agents that can be applied to different stages of the commercial food chain. In this sense, bacteriophages can be orally administered to farm animals to protect them against intestinal pathogens. However, the low pH of the stomach, the activities of bile and intestinal tract enzymes limit the efficacy of the phages. This study demonstrates the utility of an alginate/CaCO3 encapsulation method suitable for bacteriophages with different morphologies and to yield encapsulation efficacies of ~100%. For the first time, a cocktail of three alginate/CaCO3-encapsulated bacteriophages was administered as oral therapy to commercial broilers infected with Salmonella under farm-like conditions. Encapsulation protects the bacteriophages against their destruction by the gastric juice. Phage release from capsules incubated in simulated intestinal fluid was also demonstrated, whereas encapsulation ensured sufficient intestinal retention of the phages. Moreover, the small size of the capsules (125-150 µm) enables their use in oral therapy and other applications in phage therapy. This study evidenced that a cocktail of the three alginate/CaCO3-encapsulated bacteriophages had a greater and more durable efficacy than a cocktail of the corresponding non-encapsulated phages in as therapy in broilers against Salmonella, one of the most common foodborne pathogen.

Effect of route of inoculation on replication of avian influenza virus (H9N2) and interferon gene expression in guinea fowl (Numida meleagridis).

The study was designed to investigate the replication of a re-assortant H9N2 avian influenza virus (AIV) and induction of the interferon (IFNγ) response after aerosol or intranasal inoculation with the virus in guinea fowl. To determine virus shedding pattern, oropharyngeal and cloacal swabs and tissue specimens of trachea, lungs, spleen and caecal tonsils were collected post-inoculation (pi). Infected guinea fowl showed mild clinical signs, while negative control guinea fowl remained healthy and active throughout the experiment irrespective of the inoculation route. However, the clinical signs were more prominent in guinea fowl infected through the aerosol route. Virus was detected in all oropharyngeal and cloacal swabs up to 7 d pi in guinea fowl from both inoculation groups. However, virus was detected more frequently and in higher titres in oropharyngeal swabs and specimens of trachea and lungs from the group exposed to aerosols than in the group given intranasal drops. In accordance with viral replication findings, expression of IFNγ was up-regulated on 1, 2 and 4 d pi to a significantly higher level in lung tissue specimens from the group exposed to virus aerosol than from controls treated with PBS intranasally. On the other hand, IFNγ was up-regulated above that of controls in lung tissue specimens from the group treated with intranasal drops of virus only on 4 d pi. These findings indicate that virus administered in aerosols was more efficient in infecting the lower respiratory tract and in inducing activity of the IFNγ gene than virus administered as intranasal drops. The results of this study suggest that virus aerosols cause more intense respiratory infection and increase the shedding of the H9N2 AIV in guinea fowl, highlighting the potential role of guinea fowl as a mixing bowl for transmission and maintenance of H9N2 AIV between poultry premises.

Alteration of Polymeric Immunoglobulin Receptor and Neonatal Fc Receptor Expression in the Gut Mucosa of Immunodeficiency Virus-Infected Rhesus Macaques.

Polymeric immunoglobulin receptors (pIgR) and neonatal Fc receptors (FcRn) are crucial immunoglobulin (Ig) receptors for the transcytosis of immunoglobulins, that is IgA, IgM and IgG, the levels of which in mucosal secretions were altered in both HIV- and SIV-infected individuals. To gain an insight into the changes of pIgR and FcRn expression after immunodeficiency virus (SHIV/SIV) infection, real-time RT-PCR methods were established and the mRNA levels of pIgR and FcRn in normal and SHIV/SIV-infected rhesus macaques were quantitatively examined. It was found that the levels of pIgR mRNA were within a range of 10(7) copies per million copies of GAPDH mRNA in the gut mucosa of rhesus macaques, which were up to 55 times higher than that in the oral mucosa, the highest among the non-gut tissues examined. Levels of FcRn mRNA were generally lower than that of pIgR, and the levels of FcRn mRNA in the gut mucosa were also lower than that in most non-gut tissues examined. Notably, the levels of pIgR mRNA in the duodenal mucosa were positively correlated with that of IL-17A in normal rhesus macaques. Both pIgR and FcRn mRNA levels were significantly reduced in the duodenal mucosa during acute SHIV infection and in the jejunum and caecum during chronic SHIV/SIV infection. These data expanded our knowledge on the expression of pIgR and FcRn in the gastrointestinal tract of rhesus macaques and demonstrated altered expression of pIgR and FcRn in SHIV/SIV, and by extension HIV infections, which might have contributed to HIV/AIDS pathogenesis.

An in vitro attenuated strain of Histomonas meleagridis provides cross-protective immunity in turkeys against heterologous virulent isolates.

In the current study, cross-protective immunity induced by a well-defined clonal strain of Histomonas meleagridis, attenuated by prolonged in vitro cultivation against different clonal heterologous isolates of the same parasite was investigated. For this purpose, 86 turkey poults were assigned to groups consisting of 9-10 birds. Birds of four groups were vaccinated on their 1st day of life followed by re-vaccination on their 14th day of life when the remaining turkeys were left untreated. The challenge was performed using four strains of H. meleagridis that were isolated from chickens or turkeys from different outbreaks of histomonosis in Europe and three of them showed diversities in their genome. Hence, every strain used for the challenge was applied to a group of vaccinated and a group of non-vaccinated birds while birds of the negative control group were sham inoculated. Non-vaccinated birds suffered from severe histomonosis due to the challenge with fatalities reaching from 5 to 10 turkeys per group. Vaccinated birds did not contract clinical signs of the disease following challenge and the increase in weight was unaffected compared to birds of the negative control group. A significant difference in lesion scores was recorded between vaccinated and non-vaccinated groups, with very few instances of liver involvement in the former groups. Livers of vaccinated birds that were without recordable macroscopic lesions were also found negative by immunohistochemical investigation. According to the data obtained, the present study demonstrates, for the first time, the cross-protective capability of a tentative vaccine strain of H. meleagridis attenuated in vitro against heterologous virulent isolates of different origin.

Differential expression of immune-related cytokine genes in response to J group avian leukosis virus infection in vivo.

Infection with J group avian leukosis virus (ALV-J) can result in immunosuppression and subsequently increased susceptibility to secondary infection. The innate immune system is the first line defense system in prevention of further bacterial and viral infections. Cytokines play key roles in the innate immune system. In this study, we used RT-qPCR technology to test the cytokine mRNA expression levels in various immune tissues, including the spleen, bursa of fabricius and cecal tonsil, in the days following ALV-J infection. The results indicated that in the infected group, the expression levels of interleukin-6 (IL-6), IL-18, interferon-α (IFN-α) and IFN-γ significantly increased in the spleen and reached peak levels that were thousandfolds higher than baselines at 9-12 days post-infection (d.p.i.). The levels in the bursa of fabricius slightly increased, and the levels in the cecal tonsil were not significantly altered. Moreover, the pattern of the expression of these three cytokines in the spleens of the infected group was similar to the pattern of viremia of this group. These results suggest that the spleen plays an important role in the interaction between ALV-J infection and the innate immune system. This study contributes to the understanding of innate immune responses to ALV-J infection and also elucidates the mechanisms of the pathogenicity of ALV-J in chickens.

Characterization of virus-like particles associated with the human faecal and caecal microbiota.

This work represents an investigation into the presence, abundance and diversity of virus-like particles (VLPs) associated with human faecal and caecal samples. Various methodologies for the recovery of VLPs from faeces were tested and optimized, including successful down-stream processing of such samples for the purpose of an in-depth electron microscopic analysis, pulsed-field gel electrophoresis and efficient DNA recovery. The applicability of the developed VLP characterization method beyond the use of faecal samples was then verified using samples obtained from human caecal fluid.

Marek's disease virus-induced transient cecal tonsil atrophy.

Marek's disease (MD) is a lymphoproliferative disease of domestic chickens that is caused by a highly cell-associated oncogenic alpha-herpesvirus, Marek's disease virus (MDV). MDV replicates in chicken lymphocytes and establishes a latent infection within CD4+ T cells. MD is characterized by bursal and thymic atrophy and rapid onset of T cell lymphomas that infiltrate lymphoid tissues, visceral organs, and peripheral nerves with severe clinical symptoms that include transient paralysis, anemia, weight loss, and neurologic disorders. The cecal tonsils (CT) are considered the largest lymphoid aggregates of avian gut-associated lymphoid tissue (GALT). Along with Peyer's patches, CT elicits protective immune responses against bacterial and viral pathogens in the intestinal tract of avian species. In this study we investigated the effect of MDV infection on CT structural changes and cytokine gene expression in two MD-susceptible and resistant chicken lines. The histopathologic analysis revealed that MDV causes the loss of germinal follicular centers within the CT of the resistant line while inducing a severe, near-total lymphoid depletion in the susceptible line during cytolytic infection. The lymphoid depletion, however, recovered approximately 2 wk postinfection but the loss of germinal centers persisted during the latent phase of infection in both lines. The atrophy of this important GALT was transient and there were no visible differences between the CT of the infected and control birds of either line by 21 days postinfection. Of the genes tested, IFN-beta and IFN-gamma were up regulated in the CT of both infected lines during lytic infection. The expression levels of both genes were much higher in the susceptible line than in the resistant line. A similar pattern of expression was observed for IL-6, IL-10, IL-13, and iNOS. IL-12 was up regulated in the CT of birds of the susceptible line during all three phases of infection. An over expression of IL-18 was also observed in CT of the susceptible line during lytic and latent phases of infection. IL-8 was the only cytokine expressed at higher levels in the CT of the resistant line during the lytic and reactivation phases of infection. The histopathologic observations and gene expression profiling are further discussed.

Pathogenicity and cytokine gene expression pattern of a serotype 4 fowl adenovirus isolate.

Hydropericardium-hepatitis syndrome (HHS), a recently emerged disease of chickens, is caused by some strains of fowl adenovirus serotype 4 (FAdV-4). In this study, a Canadian FAdV-4 isolate, designated as FAdV-4 ON1, was evaluated for pathogenicity after oral and intramuscular (im) infection of specific pathogen free (SPF) chickens. Pathogenicity was evaluated by observation of clinical signs and gross and histological lesions. The highest viral DNA copy numbers, irrespective of the inoculation route, were detected in the cecal tonsils. Virus titers in cloacal swabs collected over the entire study period were compared between the orally and im inoculated chickens, and the difference in titers between the two groups was significant (P<0.001), the oral group had a higher rank. The antibody response of infected chickens tested by an adenovirus-specific ELISA showed a statistically significant (P<0.001) difference between the orally and im inoculated chickens. The im inoculated chickens had higher values than birds inoculated orally (P<0.001). Serum samples from both groups collected at 14 days post-infection completely neutralized FAdV-4 ON1. In addition, the effects of FAdV-4 ON1 infection on transcription of a number of avian cytokines were studied in vivo. The expression of interferon (IFN)-γ and interleukin (IL)-10 in the liver was induced at early times after infection. This FAdV-4 ON1 potentially could be used as a live vaccine against HHS and developed as vaccine vector. The GenBank/EMBL/DDBJ accession number for the FAdV-4 ON1 sequence is GU188428.

Identification of an astrovirus commonly infecting laboratory mice in the US and Japan.

Mice (Mus musculus) are the most commonly used laboratory animals. Viral metagenomics on tissues of immunodeficient mice revealed sequences of a novel mammalian astrovirus. Using PCR, we screened mice from 4 breeders, 4 pharmaceutical companies, 14 research institutes and 30 universities in the US and Japan. Mice from one US breeder tested positive while none from Japanese breeders were positive for MuAstV. Mice in over half of the universities (19/30), institutes (7/14) and pharmaceutical animal facilities (2/4) investigated revealed the presence of MuAstV. Nine mice strains tested positive including both immunodeficient strains (NSG, NOD-SCID, NSG-3GS, C57BL6-Timp-3 (-/-), and uPA-NOG) and immunocompetent strains (B6J, ICR, Bash2, BALB/c). Our data indicates that MuAstV has a wide geographical, institutional and host strain distribution. Comparison of the MuAstV RdRp sequences showed numerous mutations indicating ongoing viral divergence in different facilities. This study demonstrates the need for metagenomic screening of laboratory animals to identify adventitious infections that may affect experimental outcomes.

The survey of porcine teschoviruses, sapeloviruses and enteroviruses B infecting domestic pigs and wild boars in the Czech Republic between 2005 and 2011.

This study presents results of epidemiological survey and genetic characterisation of porcine enteric picornaviruses belonging to the genera Teschovirus, Sapelovirus, and Porcine enterovirus B. Faecal or gut content samples from domestic pigs (Sus scrofa f. domestica) and the cecal content of wild boars (Sus scrofa) of different ages (collected between 2005 and 2011) were analysed by molecular methods. Porcine enterovirus B was the most prevalent virus detected in both domestic pigs and wild boars (50.2% and 69.4%, respectively), followed by Porcine teschovirus and Porcine sapelovirus. The majority of positive domestic pigs (69.4%) and wild boars (64.3%) were infected with two or three tested viruses. There was no significant difference in prevalences of teschoviruses, sapeloviruses, and enteroviruses among healthy and diarrhoeic pigs. Results of epidemiological survey demonstrated that all target viral genera are common in Czech farms producing pigs and wild boars. Amplified nucleotide fragments of VP2 region obtained from randomly selected both historical and recent Teschovirus isolates were sequenced. Based on sequence data, historical Porcine teschovirus isolate CAPM V-180, previously determined as serotype 1 was reclassified into serotype 11. Moreover, another recent Porcine teschovirus isolate OH264/2010 was described and classified into serotype 11. Four nontypeable PTV strains (historical isolate CAPM V-182/1976 and recent isolates JA247/2010, NI429/2010, and BR1576/2007) identified in this study might represent novel serotypes. To the best of our knowledge, our study represents the first description of this serotype in the Czech Republic.

Development of a reverse-genetics system for murine norovirus 3: long-term persistence occurs in the caecum and colon.

Human noroviruses (HuNoV) are a major cause of viral gastroenteritis worldwide, yet, due to the inability to propagate HuNoV in cell culture, murine norovirus (MNV) is typically used as a surrogate to study norovirus biology. MNV-3 represents an attractive strain to study norovirus infections in vivo because it establishes persistence in wild-type mice, yet causes symptoms resembling gastroenteritis in immune-compromised STAT1(-/-) mice. The lack of reverse-genetics approaches to recover genetically defined MNV-3 has limited further studies on the identification of viral sequences that contribute to persistence. Here we report the establishment of a combined DNA-based reverse-genetics and mouse-model system to study persistent MNV-3 infections in wild-type (C57BL/6) mice. Viral RNA and infectious virus were detected in faeces for at least 56 days after inoculation. Strikingly, the highest concentrations of viral RNA during persistence were detected in the caecum and colon, suggesting that viral persistence is maintained in these tissues. Possible adaptive changes arising during persistence in vivo appeared to accumulate in the minor capsid protein (VP2) and the viral polymerase (NS7), in contrast with adaptive mutations selected during cell-culture passages in RAW264.7 cells that appeared in the major capsid protein (VP1) and non-structural protein NS4. This system provides an attractive model that can be readily used to identify viral sequences that contribute to persistence in an immunocompetent host and to more acute infection in an immunocompromised host, providing new insights into the biology of norovirus infections.

Viral nucleoprotein localization and lesions of Newcastle disease in tissues of indigenous ducks.

Localization of Newcastle disease viral nucleoprotein and pathological lesions was evaluated in tissues of 55 indigenous ducks (45 experimentally infected and 10 sentinel ones). In addition, ten Newcastle disease infected chickens were used to ensure that the virus inoculum administered to the ducks produced the disease in chickens, the susceptible hosts. Ducks were killed on day 1, 4, 8 and 14 post-infection. Post-mortem examination was done with six tissues (liver, spleen, lung, caecal tonsils, kidneys and brain) being collected from each bird. The tissues were preserved in 10% neutral formalin for 24 h. They were then transferred to 70% ethanol for histology and immunohistochemical staining. Airsacculitis, necrotic splenic foci, congested intestines, lymphoid depleted caecal tonsils and focal infiltrations by mononuclear cells were the main pathological lesions in infected ducks. Over 28.9% of the infected ducks had Newcastle disease viral nucleoprotein in macrophage-like large mononuclear cells in the caecal tonsils and kidney tubular epithelium. The viral antigens were located in the cytoplasm and nucleolus of the cells. The other organs had no detectable viral antigens. This study shows that the kidneys and caecal tonsils are the likely predilection sites for the virus in ducks. They thus need to be considered as diagnostic indicators for the viral carriage in ducks.

Direct feeding of microencapsulated bacteriophages to reduce Salmonella colonization in pigs.

Salmonella shedding often increases in pigs after transportation and/or lairage. We previously showed that administering anti-Salmonella bacteriophages to pigs by gavage significantly reduced Salmonella colonization when the pigs were exposed to a Salmonella-contaminated holding pen. Here we tested whether a microencapsulated phage cocktail would remain effective if the treatment was administered to pigs in the feed. Pigs (n=21) were randomly placed into three groups: feed, gavage, and control. The feed group was direct-fed a microencapsulated phage cocktail daily for 5 days. On the fifth day, the gavage group received the same phage cocktail by gavage, whereas control pigs received a mock treatment containing no phage. All pigs were then orally challenged with Salmonella enterica serovar Typhimurium. Fecal swab samples were collected every 2 h. At 6 h postchallenge, all pigs were euthanized, and ileal and cecal contents and mesenteric lymph nodes were collected and analyzed for the challenge organism. Pigs in the feed group were less likely to shed Salmonella Typhimurium at 2 h (38.1%) and 4 h (42.9%) postchallenge than pigs in both the gavage (2 h: 71.4%; 4 h: 81.1%) and control (2 h: 71.4%; 4 h: 85.7%) groups (p<0.05). Likewise, concentrations of Salmonella Typhimurium in ileal (2.0 log(10) colony forming units [CFU]/mL [contents]) and cecal (2.7 log(10) CFU/mL) contents from feed pigs were lower than ileal (3.0 log(10) CFU/mL) and cecal (3.7 log(10) CFU/mL) contents from control pigs. High concentrations of anti-Salmonella phages were detected in ileal and cecal contents from both feed and gavage pigs (feed ileal: 1.4×10(6); feed cecal 8.5×10(6); gavage ileal 2.0×10(4); gavage cecal: 2.2×10(3)). It is concluded that direct feeding of microencapsulated phages is a practical and effective means of reducing Salmonella colonization and shedding in pigs.

Early occurrence of apoptosis in lymphoid tissues from chickens infected with strains of Newcastle disease virus of varying virulence.

Newcastle disease virus (NDV), the causative agent of Newcastle disease, is a prevalent problem in the poultry industry and often the cause of severe economic loss. There are many strains of the virus and these have varying virulence. The most virulent strains cause systemic lesions of lymphoid tissues, with necrosis and severe lymphoid depletion. Less virulent strains do not cause as much necrosis, but may predispose to secondary infection with other pathogens. Apoptosis or programmed cell death, has been demonstrated to play a role in the pathogenesis of other paramyxovirus infections, notably those caused by measles and canine distemper viruses. To investigate the role of apoptosis in lymphoid organs during NDV infection, immunohistochemistry for determination of expression of caspase-3, a marker of imminent apoptosis, was performed on formalin-fixed paraffin wax-embedded tissues (spleen, thymus, caecal tonsils and bursa of Fabricius) from 4-week-old chickens infected with NDV strains of varying virulence 2 days previously. The amount of apoptosis was proportional to the severity of the clinical disease elicited by the strains.

Transient or persistent norovirus infection does not alter the pathology of Salmonella typhimurium induced intestinal inflammation and fibrosis in mice.

Murine noroviruses (MNV) are currently the most prevalent viruses infecting mouse research colonies. Concurrent infection of research mice with these viruses can dramatically alter the experimental outcome in some research models, but not others. In this report, we investigated the effect of MNV1 and MNV4 on a murine model of intestinal inflammation and fibrosis induced by Salmonella typhimurium infection in C57BL/6 mice. Subsequent co-infection of these mice with MNV1 or MNV4 did not lead to major changes in histopathology, the inflammatory response, or the fibrotic response. Thus, MNV does not substantially alter all gastrointestinal research models, highlighting the importance of investigating potential alterations in the research outcome by MNV on an individual basis. We hypothesize that this is particularly important in cases of research models that use immunocompromised mice, which could be more sensitive to MNV infection-induced changes.

Molecular detection of murine norovirus from experimentally and spontaneously infected mice.

The RNA polymerase gene of murine norovirus (MNV) was isolated from feces and organ samples by the reverse transcription (RT)-polymerase chain reaction (PCR). For experimental infection, homogenate of cecum obtained from an MNV-infected mouse was gavaged to 3 C.B-17-Prkdc(scid) (scid) mice and 3 ICR mice at 6 weeks of age. Sixty days after oral inoculation, MNV was isolated from the cecum (3/3 scid and 3/3 ICR), feces (3/3 scid and 3/3 ICR), duodenum (1/3 scid and 3/3 ICR), liver (1/3 scid and 1/3 ICR), and spleen (3/3 ICR) samples, but MNV was not detected in the brain, heart, kidney, lung, salivary gland, ovary, thymus, or uterus samples of any of the orally inoculated mice. Feces of males cohabiting with MNV infected dams were positive for viral RNA after 18 days of cohabitation, but 8 fetuses (embryonic day 18.0) derived from the dams were negative for the virus. The results suggest that the cecum and feces are the most suitable sample types for the detection of MNV in infected animals and that caesarean section is efficient for the elimination of the virus. In terms of spontaneous infection, the RNA polymerase gene of MNV was isolated from 33/245 (13.1%) cecum samples derived from 15/59 (25.4%) facilities, and the sequence analysis revealed that at least 5 types of the virus were prevalent. This is the first report on MNV infection in mouse colonies in Japan.