Noroviruses are the leading cause of food-borne outbreaks, including those that involve lettuce. The culturable porcine sapovirus (SaV) was used as a norovirus surrogate to study the persistence and the potential transfer of the virus from roots to leaves and from outer to inner leaves of lettuce plants. Treatment of lettuce with SaV was done through the roots of young plants, the soil, or the outer leaves of mature plants. Sampling of roots, xylem sap, and inner and outer leaves followed by RNA extraction and SaV-specific real-time reverse transcription (RT)-PCR was performed at 2 h and on postinoculation days (PID) 2, 5, 7, 14, and/or 28. When SaV was inoculated through the roots, viral RNA persisted on the roots and in the leaves until PID 28. When the virus was inoculated through the soil, viral RNA was detected on the roots and in the xylem sap until PID 14; viral RNA was detected in the leaves only until PID 2. No infectious virus was detected inside the leaves for either treatment. When SaV was inoculated through the outer leaves, viral RNA persisted on the leaves until PID 14; however, the virus did not transfer to inner leaves. Infectious viral particles on leaves were detected only at 2 h postinoculation. The milky sap (latex) of leaves, but not the roots' xylem sap, significantly decreased virus infectivity when tested in vitro. Collectively, our results showed the transfer of SaV from roots to leaves through the xylem system and the capacity of the sap of lettuce leaves to decrease virus infectivity in leaves.
Noroviruses are a common cause of gastrointestinal disease in humans worldwide. Here, we report the full-length genomic characterization of GII.4 norovirus strain HS191, which was associated with gastroenteritis in a laboratory worker in 2004.
Human noroviruses (HuNoVs) are the leading cause of food-borne illness, accounting for 58% of U.S. cases. Because HuNoVs are unculturable, surrogates are needed to investigate transmission routes and evaluate disinfection methods. However, the current surrogates, feline calicivirus (FCV) and murine NoV (MNV), are less tolerant than HuNoVs to acid and chlorine, respectively. Porcine sapovirus (SaV) is the only culturable enteropathogenic calicivirus. In this study, the resistance of SaV to physicochemical treatments was compared to that of HuNoVs (by reverse transcription-PCR), FCV, and MNV (by infectivity assays). Sapovirus and HuNoV (viral RNA) showed similar resistances to heat (56°C) and to different concentrations of chlorine. However, SaV was more resistant than HuNoVs to ethanol treatment (60% and 70%). Like HuNoVs, SaV was stable at pH 3.0 to 8.0, with a <1.0 log10 50% tissue culture infective dose (TCID50) reduction at pH 3.0 compared to the value for pH 4.0 to 8.0. SaV and MNV showed similar resistances, and both were more resistant than FCV to heat inactivation (56°C). FCV was more resistant than MNV and SaV to ethanol, and all three viruses showed similar resistances to treatment with low concentrations of chlorine for 1 min. Those results indicate that SaV is a promising surrogate for HuNoVs. Next, we used SaV as a surrogate to examine virus attachment to lettuce at different pHs. Sapovirus attached to lettuce leaves significantly at its capsid isoelectric point (pH 5.0), and the attached viral particles remained infectious on lettuce after 1 week of storage at 4°C. The culturable SaV is a good surrogate for studying HuNoV contamination and transmission in leafy greens and potential disinfectants.
Group A Rotaviruses are the most common cause of severe, dehydrating diarrhea in children worldwide. The aim of the present work was to evaluate protection against rotavirus (RV) diarrhea conferred by the prophylactic administration of specific IgY antibodies (Ab) to gnotobiotic piglets experimentally inoculated with virulent Wa G1P human rotavirus (HRV). Chicken egg yolk IgY Ab generated from Wa HRV hyperimmunized hens specifically recognized (ELISA) and neutralized Wa HRV in vitro. Supplementation of the RV Ab free cow milk diet with Wa HRV-specific egg yolk IgY Ab at a final ELISA Ab titer of 4096 (virus neutralization –VN- titer = 256) for 9 days conferred full protection against Wa HRV associated diarrhea and significantly reduced virus shedding. This protection was dose-dependent. The oral administration of semi-purified passive IgY Abs from chickens did not affect the isotype profile of the pig Ab secreting cell (ASC) responses to Wa HRV infection, but it was associated with significantly fewer numbers of HRV–specific IgA ASC in the duodenum. We further analyzed the pigś immune responses to the passive IgY treatment. The oral administration of IgY Abs induced IgG Ab responses to chicken IgY in serum and local IgA and IgG Ab responses to IgY in the intestinal contents of neonatal piglets in a dose dependent manner. To our knowledge, this is the first study to show that IgY Abs administered orally as a milk supplement passively protect neonatal pigs against an enteric viral pathogen (HRV). Piglets are an animal model with a gastrointestinal physiology and an immune system that closely mimic human infants. This strategy can be scaled-up to inexpensively produce large amounts of polyclonal IgY Abs from egg yolks to be applied as a preventive and therapeutic passive Ab treatment to control RV diarrhea.
Norovirus (NoV) genogroup II genotype 4 (GII.4) strains are the dominant cause of the majority of food-borne outbreaks, including those that involve leafy greens, such as lettuce. Since human NoVs use carbohydrates of histo-blood group antigens as receptors/coreceptors, we examined the role of carbohydrates in the attachment of NoV to lettuce leaves by using virus-like particles (VLPs) of a human NoV/GII.4 strain. Immunofluorescence analysis showed that the VLPs attached to the leaf surface, especially to cut edges, stomata, and along minor veins. Binding was quantified using enzyme-linked immunosorbent assay (ELISA) performed on cell wall materials (CWM) from innermost younger leaves and outermost lamina of older leaves. The binding to CWM of older leaves was significantly (P < 0.05) higher (1.5- to 2-fold) than that to CWM of younger leaves. Disrupting the carbohydrates of CWM or porcine gastric mucin (PGM) (a carbohydrate control) using 100 mM sodium periodate (NaIO4) significantly decreased the binding an average of 17% in younger leaves, 43% in older leaves, and 92% for PGM. In addition, lectins recognizing GalNAc, GlcNAc, and sialic acid at 100 μg/ml significantly decreased the binding an average of 41%, 33%, and 20% on CWM of older leaves but had no effect on younger leaves. Lectins recognizing α-d-Gal, α-d-Man/α-d-Glc, and α-l-Fuc showed significant inhibition on CWM of older leaves as well as that of younger leaves. All lectins, except for the lectin recognizing α-d-Gal, significantly inhibited NoV VLP binding to PGM. Collectively, our results indicate that NoV VLPs bind to lettuce CWM by utilizing multiple carbohydrate moieties. This binding may enhance virus persistence on the leaf surface and prevent effective decontamination.
In April 2008, a nucleotide sequence-based, complete genome classification system was developed for group A rotaviruses (RVs). This system assigns a specific genotype to each of the 11 genome segments of a particular RV strain according to established nucleotide percent cut-off values. Using this approach, the genome of individual RV strains are given the complete descriptor of Gx-P[x]-Ix-Rx-Cx-Mx-Ax-Nx-Tx-Ex-Hx. A Rotavirus Classification Working Group (RCWG) was formed by scientists in the field to maintain, evaluate, and develop the RV genotype classification system, in particular to aid in the designation of new genotypes. Since its conception, the group has ratified 50 new genotypes: as of January 2011, new genotypes for VP7 (G20–G26), VP4 (P–P), VP6 (I12–I16), VP1 (R5–R9), VP2 (C6–C9), VP3 (M7–M8), NSP1 (A15–A16), NSP2 (N6–N9), NSP3 (T8–T12), NSP4 (E12–E14), and NSP5/6 (H7–H11) have been defined for RV strains identified in humans, cows, pigs, horses, mice, South American camelids (guanaco and vicuña), chickens, turkeys, pheasants, and bats. With increasing numbers of complete RV genome sequences becoming available, a standardized RV strain nomenclature system is needed and the RCWG proposes that individual RV strains are named as follows: RV group/species of origin/country of identification/common name/year of identification/G- and P-type. In collaboration with the National Center for Biotechnology Information (NCBI), the RCWG is also working on developing a RV-specific resource for the deposition of nucleotide sequences. This resource will provide useful information regarding RV strains, including but not limited to, the individual gene genotypes, epidemiological, and clinical information. Together, the proposed nomenclature system and the NCBI RV resource will offer highly useful tools for investigators to search for, retrieve, and analyze the ever-growing volume of RV genomic data.
Rotavirus; Classification; Nomenclature; Strain; Nomenclature guidelines
The lack of an animal model for human norovirus (HuNoV) has hindered the development of therapeutic strategies. This study demonstrated that a commonly used cholesterol-lowering statin medication, simvastatin, which increases HuNoV replication in an in vitro replicon system, also enhances HuNoV infectivity in the gnotobiotic (Gn) pig model. In contrast, oral treatment with interferon (IFN)-α reduces HuNoV infectivity. Young piglets, all with A or H1 histo-blood group antigens on enterocytes, were treated orally with 8 mg/kg/day of simvastatin; 5 days later, the pigs were inoculated orally with a GII.4 HuNoV (HS194/2009/US strain) and then treated with simvastatin for 5 more days. Simvastatin induced significantly earlier onset and longer duration of HuNoV fecal shedding in treated pigs, frequently with higher fecal viral titers. Simvastatin impaired poly (I:C)-induced IFN-α expression in macrophages or dendritic cells, possibly due to lowered toll-like receptor (TLR) 3 expression; however, the mechanisms were not related to interferon regulatory factor 3 or nuclear factor kappa B signaling pathway. Thus, the enhanced, earlier infectivity of HuNoV in simvastatin-treated pigs coincided with the inhibitory effect of simvastatin on innate immunity. In contrast to the increased HuNoV shedding that simvastatin induced, viral shedding during the treatment period was reduced or curtailed in the HuNoV-inoculated pigs pre-treated/treated with human IFN-α. Our findings are the first to indicate that IFN-α has potential as antiviral therapy against HuNoV. Based on these intriguing and novel findings using the Gn pig model, we confirmed that HuNoV infectivity is altered by treatment with simvastatin or IFN-α. Collectively, these findings indicate that Gn pigs are a useful model to test immunomodulators or efficacy of antivirals against HuNoV.
γδ T cell responses are induced by various viral and bacterial infections. Different γδ T cells contribute to activation and regulation of the inflammatory response and to epithelial repair. How γδ T cells respond to rotavirus infection and how the colonization of probiotics influences the γδ T cell response were unknown. In this study, we evaluated by multicolor flow cytometry the frequencies and distribution of total γδ T cells and three major subsets (CD2−CD8−, CD2+CD8− and CD2+CD8+) in ileum, spleen and blood of gnotobiotic (Gn) pigs at early (3–5 days) and late phases (28 days) after rotavirus infection. The Gn pigs were inoculated with the virulent human rotavirus Wa strain and colonized with a mixture of two strains of probiotics Lactobacillus acidophilus and Lactobacillus reuteri. In naive pigs, the highest frequency of total γδ T cells was found in blood, followed by spleen and ileum at the early age (8–10 days old) whereas in older pigs (32 days of age) the highest frequency of total γδ T cells was found in ileum and spleen followed by blood. Rotavirus infection significantly increased frequencies of intestinal total γδ T cells and the putatively regulatory CD2+CD8+ γδ T cell subset and decreased frequencies of the putatively proinflammatory CD8− subsets in ileum, spleen and blood at post-infection days (PID) 3 or 5. The three γδ T cell subsets distributed and responded differently after rotavirus infection and/or lactobacilli colonization. The CD2+CD8+ subset contributed the most to the expansion of total γδ T cells after rotavirus infection in ileum because more than 77% of the total γδ T cells there were CD2+CD8+ cells. There was an additive effect between lactobacilli and rotavirus in inducing total γδ T cell expansion in ileum at PID 5. The overall effect of lactobacilli colonization versus rotavirus infection on frequencies of the CD2+CD8+ γδ T cell subset in ileum was similar; however, rotavirus-infected pigs maintained significantly higher frequencies of CD8− subsets in ileum than lactobacilli-colonized pigs. The dynamic γδ T cell responses suggest that γδ T cell subsets may play important roles in different stages of immune responses after rotavirus infection and probiotic colonization. The knowledge on the kinetics and distribution patterns of γδ T cell subsets in naïve pigs and after rotavirus infection or lactobacilli colonization provides the foundation for further mechanistic studies of their functions.
gamma delta (γδ) T cells; rotaviruses; lactobacilli; gnotobiotic pigs
A coronavirus (CoV) previously shown to be associated with catarrhal gastroenteritis in mink (Mustela vison) was identified by electron microscopy in mink faeces from two fur farms in Wisconsin and Minnesota in 1998. A pan-coronavirus and a genus-specific RT-PCR assay were used initially to demonstrate that the newly discovered mink CoVs (MCoVs) were members of the genus Alphacoronavirus. Subsequently, using a random RT-PCR approach, full-genomic sequences were generated that further confirmed that, phylogenetically, the MCoVs belonged to the genus Alphacoronavirus, with closest relatedness to the recently identified but only partially sequenced (fragments of the polymerase, and full-length spike, 3c, envelope, nucleoprotein, membrane, 3x and 7b genes) ferret enteric coronavirus (FRECV) and ferret systemic coronavirus (FRSCV). The molecular data presented in this study provide the first genetic evidence for a new coronavirus associated with epizootic catarrhal gastroenteritis outbreaks in mink and demonstrate that MCoVs possess high genomic variability and relatively low overall nucleotide sequence identities (91.7 %) between contemporary strains. Additionally, the new MCoVs appeared to be phylogenetically distant from human (229E and NL63) and other alphacoronaviruses and did not belong to the species Alphacoronavirus 1. It is proposed that, together with the partially sequenced FRECV and FRSCV, they comprise a new species within the genus Alphacoronavirus.
Norovirus is a major cause of acute gastroenteritis in humans. A norovirus outbreak occurred in Ohio in January 2010. Stool and saliva samples were obtained from six infected individuals. The full-length genomes of two representative strains (HS206 and HS210) were characterized. They belonged to GII.12 in the capsid but GII.g in the RNA polymerase region. Interestingly, an immunocompetent 2-year-old male shed virus for up to 30 days, as detected by real-time reverse transcription (RT)-PCR. Histo-blood group antigen (HBGA) typing of saliva showed that the norovirus strains infected various types of secretor-positive individuals (types A, B, and O). The viruslike particles of strain HS206 did not bind substantially to A/B/O antigens by synthetic HBGA binding, hemagglutination, or saliva binding assays. These results suggest that infection by this strain may not be A/B/O antigen dependent or that in vitro binding patterns do not always accurately reflect in vivo HBGA usage. This is different from the HBGA binding pattern of the previously reported GII.12/Aichi76 strain. Structural analysis of the predicted capsid of these GII.12 strains revealed two amino acid mismatches located near the HBGA binding sites. Four gnotobiotic pigs were inoculated orally with HS206 (6 × 1010 genomic equivalents [GE]/pig). Virus shedding began at postinoculation days (PID) 1 to 3 and continued up to PID 16 (1 × 105 to 2 × 107 GE/ml). Gastroenteritis cases caused by GII.12 noroviruses have been recently reported worldwide. We observed that this emerging GII.12 norovirus infected humans regardless of A/B/O blood type. The infection of pigs by strain HS206 suggests that interspecies transmission of this strain is possible under experimental conditions.
Norovirus (NoV) RNA was detected in the stools of 6 out 14 (42.8%) 8–12-week-old cats with enteritis from a feline shelter, in New York State. Upon sequence analysis of the complete capsid, the six NoVs were found to be identical, suggesting the spread of a unique NoV strain in the shelter. The full-length genomic sequence (7839 nt) of one feline NoV, CU081210E/2010/US, was determined. In the capsid protein VP1 region, the virus displayed the highest amino acid identity to animal genogroup IV genotype 2 (GIV.2) NoVs: lion/Pistoia-387/06/IT (97.9%) and dog/Bari-170/07/IT (90.4%). These findings document the discovery of a novel feline calicivirus, different from vesiviruses, and extend the spectrum of NoV host range. Epidemiological studies using feline NoV-specific diagnostic tools and experimental infection of cats are required to understand whether NoVs have a pathogenic role in this species.
We performed a comprehensive analysis of innate and adaptive immune responses in dual-virus infected pigs to understand whether a pre-existing immunomodulatory respiratory viral infection affects the overall immunity to a subsequent porcine respiratory coronavirus (PRCV) infection in pigs. Pigs were either mock-infected or infected with porcine reproductive and respiratory syndrome virus (PRRSV), a virus known to cause immunosuppressive respiratory disease, and then pigs were co-infected with PRCV, which normally causes subclinical respiratory infection. We collected samples for six independent experiments from 178 pigs that were also used for pathological studies. We detected a significant reduction in innate NK-cell-mediated cytotoxic function in PRRSV-infected pigs, which was synergistically further decreased in pigs co-infected with PRCV. Subsequently, in association with clinical signs we observed elevated levels of proinflammatory (IL-6), Th-1 (IL-12), and regulatory (IL-10 and TGF-β) cytokines. Increased frequencies of CD4CD8 double-positive T lymphocytes and myeloid cells, in addition to the elevated Th-1 and proinflammatory cytokines in dual-infected pigs, contributed to the severity of lung disease in pigs. The results of our study clarify how each virus modulates the host innate and adaptive immune responses, leading to inflammatory reactions and lung pathology. Thus measurements of cytokines and frequencies of immune cells may serve as indicators of the progression of respiratory viral co-infections, and provide more definitive approaches for treatment.
There is little information on the role of nitric oxide (•NO) in innate immunity to respiratory coronavirus (CoV) infections. We examined •NO levels by Greiss assay in bronchoalveolar lavage (BAL) of pigs infected with either porcine respiratory coronavirus (PRCV) or porcine reproductive and respiratory syndrome virus (PRRSV), a member of Nidovirales, like CoV. The antiviral effects of •NO on these two viruses were tested in an in vitro system using a •NO donor, S-nitroso-N-acetylpenicillamine (SNAP). We detected a large increase in •NO levels in BAL fluids of PRCV-infected pigs, but not in PRRSV-infected pigs. Pulmonary epithelial cell necrosis induced by PRCV coincided with increased •NO. Moreover, •NO levels in cell culture medium of PRRSV-infected alveolar macrophages (AMs) did not differ from that of mock-infected AMs. Antiviral assays showed that •NO significantly inhibited PRCV replication in swine testicular (ST) cells, whereas PRRSV was not susceptible to •NO based on the conditions tested. Our study suggests that unlike PRRSV which induces apoptosis in AMs, respiratory CoVs such as PRCV that infect pulmonary epithelial cells and cause cytolysis, induce •NO production in the respiratory tract. Thus, •NO may play a role in innate immunity to respiratory CoV infections by inhibiting viral replication.
Coronavirus; Porcine respiratory coronavirus; Porcine reproductive and respiratory syndrome virus (PRRSV); Nitric oxide; Antiviral effects
Real-time reverse transcription PCR revealed that new St-Valerien–like porcine caliciviruses are prevalent (2.6%–80%; 23.8% overall) in finisher pigs in North Carolina. One strain, NC-WGP93C, shares 89.3%–89.7% genomic nucleotide identity with Canadian strains. Whether these viruses cause disease in pigs or humans or are of food safety concern requires further investigation.
calicivirus; St-Valerien-like virus; porcine; prevalence; viruses; swine; United States; dispatch
The innate immune response is critical for host defence against respiratory coronaviruses (CoVs). Our study demonstrates that an ongoing respiratory virus infection compromises innate immune responses and affects the pathogenesis of a respiratory CoV co-infection. We established an innate immunosuppressive respiratory virus infection by infecting weaned pigs with porcine reproductive and respiratory syndrome virus (PRRSV), and then 10 days later, we exposed the pigs to porcine respiratory coronavirus (PRCV). The PRRSV/PRCV dual-infected pigs had reduced weight gains, higher incidence of fever and more severe pneumonia compared to either single infection. Significant suppression of innate immune responses [reduced interferon (IFN)-α levels in lung and blood natural killer (NK) cell cytotoxicity] by the ongoing PRRSV infection was observed in dual-infected pigs, which coincided with exacerbated pneumonia during early PRCV infection. The subsequent PRCV infection led to enhanced PRRSV replication in lung and a trend toward increased serum Th1 (IFN-γ) but decreased Th2 (IL-4) responses, further exacerbating PRRSV pneumonia. Following PRCV infection, more severe PRRSV-related pulmonary alveolar macrophage (PAM) apoptosis occurred, as determined by in situ TUNEL assay, suggesting increased PRRSV replication in PAMs. Collectively, our observations suggest interactive effects between PRCV and PRRSV via early innate (IFN-α) and later adaptive Th1 (IFN-γ) and Th2 (IL-4) immune responses. These findings imply that an existing immunomodulating respiratory viral co-infection may be a contributing factor to more severe pneumonia in respiratory CoV disease. Our study provides new insights into host-pathogen interactions related to co-infections by CoVs and other respiratory viruses.
Coronavirus; Co-infections; Porcine respiratory coronavirus; Porcine reproductive and respiratory syndrome virus (PRRSV); Innate immunity
The innate immune response is critical for host defence against respiratory coronaviruses (CoVs). This study demonstrated that an ongoing respiratory virus infection compromises innate immune responses and affects the pathogenesis of a respiratory CoV co-infection. An innate immunosuppressive respiratory virus infection was established by infecting weaned pigs with porcine reproductive and respiratory syndrome virus (PRRSV); 10 days later, the pigs were exposed to porcine respiratory coronavirus (PRCV). The PRRSV/PRCV dual-infected pigs had reduced weight gains, a higher incidence of fever and more severe pneumonia compared with either single infection. Significant suppression of innate immune responses [reduced alpha interferon (IFN-α) levels in the lungs and reduced blood natural killer cell cytotoxicity] by the ongoing PRRSV infection was observed in dual-infected pigs, which coincided with exacerbated pneumonia during early PRCV infection. The subsequent PRCV infection led to enhanced PRRSV replication in the lungs and a trend towards increased serum T-helper type 1 (Th1) (IFN-γ) but decreased Th2 [interleukin (IL)-4] responses, further exacerbating PRRSV pneumonia. Following PRCV infection, more severe PRRSV-related pulmonary alveolar macrophage (PAM) apoptosis occurred, as determined by an in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling assay, suggesting increased PRRSV replication in PAMs. Collectively, these observations suggest interactive effects between PRCV and PRRSV via early innate (IFN-α) and later adaptive Th1 (IFN-γ) and Th2 (IL-4) immune responses. These findings imply that an existing immunomodulating respiratory viral co-infection may be a contributing factor to more severe pneumonia in respiratory CoV disease. This study provides new insights into host–pathogen interactions related to co-infection by CoVs and other respiratory viruses.
We determined the impact of mucosal prime/boost regimens and vaccine type (attenuated Wa human rotavirus [AttHRV] or nonreplicating Wa 2/6 rotavirus-like particles [VLP]) on protection and antibody-secreting cell (ASC) responses to HRV in a neonatal gnotobiotic pig disease model. Comparisons of delivery routes for AttHRV and evaluation of nonreplicating VLP vaccines are important as alternative vaccine approaches to overcome risks associated with live oral vaccines. Groups of neonatal gnotobiotic pigs were vaccinated using combinations of oral (PO) and intranasal (IN) inoculation routes as follows: (i) 3 oral doses of AttHRV (AttHRV3×PO); (ii) AttHRV3×IN; (iii) AttHRVPO, then 2/6VLP2×IN; (iv) AttHRVIN, then 2/6VLP2×IN; and (v) mock-inoculated controls. Subsets of pigs from each group were challenged with virulent Wa HRV [P1A(8) G1] (4 weeks post-primary inoculation) to assess protection. The AttHRVPO+2/6VLP2×IN pigs had the highest protection rates against virus shedding and diarrhea (71% each); however, these rates did not differ statistically among the vaccine groups, except for the AttHRVIN+2/6VLPIN group, which had a significantly lower protection rate (17%) against diarrhea. The isotype, magnitude, and tissue distribution of ASCs were analyzed by enzyme-linked immunospot assay. The highest mean numbers of virus-specific IgG and IgA ASCs were observed pre- and postchallenge in both intestinal and systemic lymphoid tissues of the AttHRVPO+2/6VLPIN group. Thus, the AttHRVPO+2/6VLPIN vaccine regimen using immunostimulating complexes (ISCOM) and multiple mucosal inductive sites, followed by AttHRV3×PO or IN regimens, were the most effective vaccine regimens, suggesting that either AttHRVPO+2/6VLPIN or AttHRV3×IN may be an alternative approach to AttHRV3×PO for inducing protective immunity against rotavirus diarrhea.
By sequence and phylogenetic analyses, the 11 genomic segments of two bovine rotaviruses isolated from clinically infected calves were proven to be derived from the swine-like PG5 genotype. This finding reinforced the hypothesis that interspecies transmission of completely heterologous strains can occur in nature.
Toll-like receptors (TLR) play an important role in the recognition of microbes by host sentinel cells that leads to the subsequent innate and adaptive immune responses. In this study, we evaluated the patterns of TLR2-, TLR3- and TLR9-expressing antigen presenting cells (APCs) in spleen and blood of gnotobiotic (Gn) pigs after colonization with a mixture of two strains of lactic acid bacteria (LAB), Lactobacillus acidophilus and Lactobacillus reuteri or infection with the virulent human rotavirus (HRV) Wa strain. We also assessed the influence of LAB on TLR and serum innate cytokine responses induced by HRV. Distributions of subpopulations of APCs [CD14+/−SWC3+CD11R1− monocytes/macrophages and CD14+/−SWC3+CD11R1+ conventional dendritic cells (cDCs)] were described in our previous report (Zhang, W., Wen, K., Azevedo, M.S., Gonzalez, A.M., Saif, L.J., Li, G., Yousef, A.E., Yuan, L., 2008. Lactic acid bacterial colonization and human rotavirus infection influence distribution and frequencies of monocytes/macrophages and dendritic cells in neonatal gnotobiotic pigs. Vet. Immunol. Immunopathol. 121, pp. 222–231). We demonstrated that LAB induced strong TLR2-expressing APC responses in blood and spleen, HRV induced a TLR3 response in spleen, and TLR9 responses were induced by either HRV (in spleen) or LAB (in blood). LAB and HRV have an additive effect on TLR2- and TLR9-expressing APC responses, consistent with the adjuvant effect of LAB. Overall, the frequencies of TLR-expressing CD14+ APCs were higher than CD14− APCs. LAB enhanced the IFN-γ and IL-4 responses in serum, but it had a suppressive effect on the TLR3- and TLR9-expressing CD14− APC responses in spleen and the serum IFN-α response induced by HRV. These results elucidated the systemic TLR2-, TLR3-, and TLR9-expressing monocyte/macrophage and cDC responses after HRV infection, LAB colonization, and the two combined. Our findings facilitate the understanding of the mechanism of LAB’s adjuvant effect on rotavirus vaccines and the diverse innate and adaptive immune responses induced by commensal LAB colonization versus rotavirus infection and the interactions between them.
Toll-like receptors Rotavirus; Lactobacilli; Dendritic cells; Monocytes/macrophages; Gnotobiotic pigs
Summary: Host range is a viral property reflecting natural hosts that are infected either as part of a principal transmission cycle or, less commonly, as “spillover” infections into alternative hosts. Rarely, viruses gain the ability to spread efficiently within a new host that was not previously exposed or susceptible. These transfers involve either increased exposure or the acquisition of variations that allow them to overcome barriers to infection of the new hosts. In these cases, devastating outbreaks can result. Steps involved in transfers of viruses to new hosts include contact between the virus and the host, infection of an initial individual leading to amplification and an outbreak, and the generation within the original or new host of viral variants that have the ability to spread efficiently between individuals in populations of the new host. Here we review what is known about host switching leading to viral emergence from known examples, considering the evolutionary mechanisms, virus-host interactions, host range barriers to infection, and processes that allow efficient host-to-host transmission in the new host population.
Porcine enteric caliciviruses include sapoviruses and noroviruses. Porcine sapoviruses infect pigs of all ages and cause diarrhea in young pigs, whereas porcine noroviruses were detected exclusively from adult pigs without clinical signs. Importantly, certain porcine norovirus strains were genetically and antigenically related to human noroviruses. This raises public health concerns that pigs may be reservoirs for emergence of epidemic human norovirus strains. This article reviews the discovery of porcine noroviruses and sapoviruses, their classification, diagnosis, epidemiology and genetic and antigenic relatedness to human caliciviruses.
calicivirus; porcine; norovirus; sapovirus
We evaluated virus-specific B and T cell responses induced by the attenuated Wa (P1AG1) human rotavirus (AttHRV) oral 2-dose vaccine with or without Lactobacillus acidophilus (LA) colonization in neonatal gnotobiotic (Gn) pigs. The AttHRV vaccinated and LA-fed pigs had a significantly higher magnitude of HRV-specific IFN-γ producing CD8+ T cell responses in ileum and spleen, IgA and IgG antibody-secreting cell responses in ileum, and serum IgM, IgA and IgG antibody and virus neutralizing antibody titers compared to the AttHRV vaccinated pigs without LA colonization. These findings suggest thatL. acidophilus has significant immunopotentiating effects and may be used as a safe oral adjuvant for rotavirus vaccines in neonates.
Probiotic Lactobacillus; Gnotobiotic pigs; B and T cell immune responses to rotavirus; vaccine
We examined rotavirus-specific IFN-γ producing CD4+, CD8+ and CD4+CD8+ T cell responses in gnotobiotic pigs infected with a virulent human rotavirus (VirHRV) or vaccinated with an attenuated (Att) HRV vaccine (AttHRV3x or AttHRV2x) or an AttHRV oral priming and 2/6-virus-like particle (VLP) intranasal boosting (AttHRV-2/6VLP) regimen. In VirHRV infected pigs, HRV-specific IFN-γ producing T cells reside primarily in ileum. AttHRV-2/6VLP induced similar frequencies of intestinal IFN-γ producing T cells as the VirHRV, whereas AttHRV3x or 2x vaccines were less effective. Protection rates against rotavirus diarrhea upon VirHRV challenge significantly correlated (r = 0.97–1.0, p < 0.005) with frequencies of intestinal IFN-γ producing T cells, suggesting their role in protective immunity.
Human rotavirus vaccine; T cell responses; Gnotobiotic pigs
We sequenced and analyzed the full-length genomes of four coronaviruses (CoVs), each from a distinct wild-ruminant species in Ohio: sambar deer (Cervus unicolor), a waterbuck (Kobus ellipsiprymnus), a sable antelope (Hippotragus niger), and a white-tailed deer (Odocoileus virginianus). The fecal samples from the sambar deer, the waterbuck, and the white-tailed deer were collected during winter dysentery outbreaks and sporadic diarrhea cases in 1993 and 1994 (H. Tsunemitsu, Z. R. el-Kanawati, D. R. Smith, H. H. Reed, and L. J. Saif, J. Clin. Microbiol. 33:3264-3269, 1995). A fecal sample from a sable antelope was collected in 2003 from an Ohio wild-animal habitat during the same outbreak when a bovine-like CoV from a giraffe (GiCoV) was isolated (M. Hasoksuz, K. Alekseev, A. Vlasova, X. Zhang, D. Spiro, R. Halpin, S. Wang, E. Ghedin, and L. J. Saif, J. Virol. 81:4981-4990, 2007). For two of the CoVs (sambar deer and waterbuck), complete genomes from both the cell culture-adapted and gnotobiotic-calf-passaged strains were also sequenced and analyzed. Phylogenetically, wild-ruminant CoVs belong to group 2a CoVs, with the closest relatedness to recent bovine CoV (BCoV) strains. High nucleotide identities (99.4 to 99.6%) among the wild-ruminant strains and recent BCoV strains (BCoV-LUN and BCoV-ENT, isolated in 1998) further confirm the close relatedness. Comparative genetic analysis of CoVs of captive wild ruminants with BCoV strains suggests that no specific genomic markers are present that allow discrimination between the bovine strains and bovine-like CoVs from captive wild ruminants; furthermore, no specific genetic markers were identified that defined cell cultured or calf-passaged strains or the host origin of strains. The results of this study confirm prior reports of biologic and antigenic similarities between bovine and wild-ruminant CoVs and suggest that cattle may be reservoirs for CoVs that infect captive wild ruminants or vice versa and that these CoVs may represent host range variants of an ancestral CoV.
Group A rotavirus is one of the most common causes of severe diarrhea in human infants and newborn animals. Rotavirus virions are triple-layered particles. The outer capsid proteins VP4 and VP7 are highly variable and represent the major neutralizing antigens. The inner capsid protein VP6 is conserved among group A rotaviruses, is highly immunogenic, and is the target antigen of most immunodiagnosis tests. Llama-derived single-chain antibody fragments (VHH) are the smallest molecules with antigen-binding capacity and can therefore be expected to have properties different from conventional antibodies. In this study a library containing the VHH genes of a llama immunized with recombinant inner capsid protein VP6 was generated. Binders directed to VP6, in its native conformation within the viral particle, were selected and characterized. Four selected VHH directed to conformational epitopes of VP6 recognized all human and animal rotavirus strains tested and could be engineered for their use in immunodiagnostic tests for group A rotavirus detection. Three of the four VHH neutralized rotavirus in vivo independently of the strain serotype. Furthermore, this result was confirmed by in vivo partial protection against rotavirus challenge in a neonatal mouse model. The present study demonstrates for the first time a broad neutralization activity of VP6 specific VHH in vitro and in vivo. Neutralizing VHH directed to VP6 promise to become an essential tool for the prevention and treatment of rotavirus diarrhea.