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An enteric virus can replace the beneficial function of commensal bacteria.

Kernbauer E, Ding Y, Cadwell K - Nature (2014)

Bottom Line: Intestinal microbial communities have profound effects on host physiology.Consistent with this observation, the IFN-α receptor was essential for the ability of MNV to compensate for bacterial depletion.Importantly, MNV infection offset the deleterious effect of treatment with antibiotics in models of intestinal injury and pathogenic bacterial infection.

View Article: PubMed Central - PubMed

Affiliation: 1] Kimmel Center for Biology and Medicine at the Skirball Institute, New York University School of Medicine, New York, New York 10016, USA [2] Department of Microbiology, New York University School of Medicine, New York, New York 10016, USA.

ABSTRACT
Intestinal microbial communities have profound effects on host physiology. Whereas the symbiotic contribution of commensal bacteria is well established, the role of eukaryotic viruses that are present in the gastrointestinal tract under homeostatic conditions is undefined. Here we demonstrate that a common enteric RNA virus can replace the beneficial function of commensal bacteria in the intestine. Murine norovirus (MNV) infection of germ-free or antibiotic-treated mice restored intestinal morphology and lymphocyte function without inducing overt inflammation and disease. The presence of MNV also suppressed an expansion of group 2 innate lymphoid cells observed in the absence of bacteria, and induced transcriptional changes in the intestine associated with immune development and type I interferon (IFN) signalling. Consistent with this observation, the IFN-α receptor was essential for the ability of MNV to compensate for bacterial depletion. Importantly, MNV infection offset the deleterious effect of treatment with antibiotics in models of intestinal injury and pathogenic bacterial infection. These data indicate that eukaryotic viruses have the capacity to support intestinal homeostasis and shape mucosal immunity, similarly to commensal bacteria.

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Mono-association of germfree mice with MNV does not lead to uncontrolled viral replication or disease(a) Schematic of MNV mono-association procedure (see methods for additional details). Germfree (GF) breeder pairs (F0) within a gnotobiotic isolator were infected with 3×106 plaque forming units (pfu) of MNV.CR6, which was allowed to transmit naturally to offspring (F1). Weaned offspring were maintained in isolators until adulthood, and then either used for analysis or as breeders to generate additional experimental animals (F2). (b) Successful transmission to offspring and the persistent presence of the virus in mono-associated GF mice (GF+MNV) was confirmed by performing a plaque assay using stool harvested from 8 week old offspring (~1 month after weaning). The amount of virus in stool from GF mice, antibiotics (ABX)-treated WT and IFNAR−/− mice, and conventional (Conv) mice infected with 3×106 pfu of the indicated strains of MNV for 10 days are also shown, N = 5 mice per group. (c-f) Mice receiving the indicated treatments did not display significant histopathology in the small intestine (c,e) and colon (d,f) based on blind quantification of H&E-stained sections using a previously described scoring system37. Mice receiving a pathology score of 1 displayed mild blunting of villi (additional details in Methods section). No histopathology was detected in spleens, and no other signs of disease were noted. Note that a previous publication in which mice were reported to display pathologies following MNV infection used a different strain of MNV, an early time point (24 hours post-infection), and mice on a different background (129/Sv) 38. The lack of pathology in C57BL/6 mice persistently infected with MNV.CR6 is consistent with our previous publication15. N = 5-7 mice/group. *p<0.05; **p<0.01. All graphs display means ± SEM.
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Figure 6: Mono-association of germfree mice with MNV does not lead to uncontrolled viral replication or disease(a) Schematic of MNV mono-association procedure (see methods for additional details). Germfree (GF) breeder pairs (F0) within a gnotobiotic isolator were infected with 3×106 plaque forming units (pfu) of MNV.CR6, which was allowed to transmit naturally to offspring (F1). Weaned offspring were maintained in isolators until adulthood, and then either used for analysis or as breeders to generate additional experimental animals (F2). (b) Successful transmission to offspring and the persistent presence of the virus in mono-associated GF mice (GF+MNV) was confirmed by performing a plaque assay using stool harvested from 8 week old offspring (~1 month after weaning). The amount of virus in stool from GF mice, antibiotics (ABX)-treated WT and IFNAR−/− mice, and conventional (Conv) mice infected with 3×106 pfu of the indicated strains of MNV for 10 days are also shown, N = 5 mice per group. (c-f) Mice receiving the indicated treatments did not display significant histopathology in the small intestine (c,e) and colon (d,f) based on blind quantification of H&E-stained sections using a previously described scoring system37. Mice receiving a pathology score of 1 displayed mild blunting of villi (additional details in Methods section). No histopathology was detected in spleens, and no other signs of disease were noted. Note that a previous publication in which mice were reported to display pathologies following MNV infection used a different strain of MNV, an early time point (24 hours post-infection), and mice on a different background (129/Sv) 38. The lack of pathology in C57BL/6 mice persistently infected with MNV.CR6 is consistent with our previous publication15. N = 5-7 mice/group. *p<0.05; **p<0.01. All graphs display means ± SEM.

Mentions: Much of our knowledge on the role of commensal bacteria in mucosal immunity comes from characterization of germfree (GF) mice, which display aberrant intestinal morphology and deficiencies in the lymphocyte compartment due to the absence of bacteria16. Thus, we utilized GF mice as a reductionist model to determine if MNV infection can provide developmental cues that have been mainly attributed to bacteria. GF mice were mono-associated with MNV.CR6 (GF+MNV) in a gnotobiotic isolator by infecting breeding pairs with 3×106 plaque forming units (PFU) and allowing the virus to be naturally propagated to offspring in subsequent generations, analogous to newborns that inherit commensal bacteria from parents (Extended data Fig. 1a). Despite persistent presence of the virus, there were no signs of overt inflammation in the intestine (Extended data Fig. 1b-d).


An enteric virus can replace the beneficial function of commensal bacteria.

Kernbauer E, Ding Y, Cadwell K - Nature (2014)

Mono-association of germfree mice with MNV does not lead to uncontrolled viral replication or disease(a) Schematic of MNV mono-association procedure (see methods for additional details). Germfree (GF) breeder pairs (F0) within a gnotobiotic isolator were infected with 3×106 plaque forming units (pfu) of MNV.CR6, which was allowed to transmit naturally to offspring (F1). Weaned offspring were maintained in isolators until adulthood, and then either used for analysis or as breeders to generate additional experimental animals (F2). (b) Successful transmission to offspring and the persistent presence of the virus in mono-associated GF mice (GF+MNV) was confirmed by performing a plaque assay using stool harvested from 8 week old offspring (~1 month after weaning). The amount of virus in stool from GF mice, antibiotics (ABX)-treated WT and IFNAR−/− mice, and conventional (Conv) mice infected with 3×106 pfu of the indicated strains of MNV for 10 days are also shown, N = 5 mice per group. (c-f) Mice receiving the indicated treatments did not display significant histopathology in the small intestine (c,e) and colon (d,f) based on blind quantification of H&E-stained sections using a previously described scoring system37. Mice receiving a pathology score of 1 displayed mild blunting of villi (additional details in Methods section). No histopathology was detected in spleens, and no other signs of disease were noted. Note that a previous publication in which mice were reported to display pathologies following MNV infection used a different strain of MNV, an early time point (24 hours post-infection), and mice on a different background (129/Sv) 38. The lack of pathology in C57BL/6 mice persistently infected with MNV.CR6 is consistent with our previous publication15. N = 5-7 mice/group. *p<0.05; **p<0.01. All graphs display means ± SEM.
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Related In: Results  -  Collection

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Figure 6: Mono-association of germfree mice with MNV does not lead to uncontrolled viral replication or disease(a) Schematic of MNV mono-association procedure (see methods for additional details). Germfree (GF) breeder pairs (F0) within a gnotobiotic isolator were infected with 3×106 plaque forming units (pfu) of MNV.CR6, which was allowed to transmit naturally to offspring (F1). Weaned offspring were maintained in isolators until adulthood, and then either used for analysis or as breeders to generate additional experimental animals (F2). (b) Successful transmission to offspring and the persistent presence of the virus in mono-associated GF mice (GF+MNV) was confirmed by performing a plaque assay using stool harvested from 8 week old offspring (~1 month after weaning). The amount of virus in stool from GF mice, antibiotics (ABX)-treated WT and IFNAR−/− mice, and conventional (Conv) mice infected with 3×106 pfu of the indicated strains of MNV for 10 days are also shown, N = 5 mice per group. (c-f) Mice receiving the indicated treatments did not display significant histopathology in the small intestine (c,e) and colon (d,f) based on blind quantification of H&E-stained sections using a previously described scoring system37. Mice receiving a pathology score of 1 displayed mild blunting of villi (additional details in Methods section). No histopathology was detected in spleens, and no other signs of disease were noted. Note that a previous publication in which mice were reported to display pathologies following MNV infection used a different strain of MNV, an early time point (24 hours post-infection), and mice on a different background (129/Sv) 38. The lack of pathology in C57BL/6 mice persistently infected with MNV.CR6 is consistent with our previous publication15. N = 5-7 mice/group. *p<0.05; **p<0.01. All graphs display means ± SEM.
Mentions: Much of our knowledge on the role of commensal bacteria in mucosal immunity comes from characterization of germfree (GF) mice, which display aberrant intestinal morphology and deficiencies in the lymphocyte compartment due to the absence of bacteria16. Thus, we utilized GF mice as a reductionist model to determine if MNV infection can provide developmental cues that have been mainly attributed to bacteria. GF mice were mono-associated with MNV.CR6 (GF+MNV) in a gnotobiotic isolator by infecting breeding pairs with 3×106 plaque forming units (PFU) and allowing the virus to be naturally propagated to offspring in subsequent generations, analogous to newborns that inherit commensal bacteria from parents (Extended data Fig. 1a). Despite persistent presence of the virus, there were no signs of overt inflammation in the intestine (Extended data Fig. 1b-d).

Bottom Line: Intestinal microbial communities have profound effects on host physiology.Consistent with this observation, the IFN-α receptor was essential for the ability of MNV to compensate for bacterial depletion.Importantly, MNV infection offset the deleterious effect of treatment with antibiotics in models of intestinal injury and pathogenic bacterial infection.

View Article: PubMed Central - PubMed

Affiliation: 1] Kimmel Center for Biology and Medicine at the Skirball Institute, New York University School of Medicine, New York, New York 10016, USA [2] Department of Microbiology, New York University School of Medicine, New York, New York 10016, USA.

ABSTRACT
Intestinal microbial communities have profound effects on host physiology. Whereas the symbiotic contribution of commensal bacteria is well established, the role of eukaryotic viruses that are present in the gastrointestinal tract under homeostatic conditions is undefined. Here we demonstrate that a common enteric RNA virus can replace the beneficial function of commensal bacteria in the intestine. Murine norovirus (MNV) infection of germ-free or antibiotic-treated mice restored intestinal morphology and lymphocyte function without inducing overt inflammation and disease. The presence of MNV also suppressed an expansion of group 2 innate lymphoid cells observed in the absence of bacteria, and induced transcriptional changes in the intestine associated with immune development and type I interferon (IFN) signalling. Consistent with this observation, the IFN-α receptor was essential for the ability of MNV to compensate for bacterial depletion. Importantly, MNV infection offset the deleterious effect of treatment with antibiotics in models of intestinal injury and pathogenic bacterial infection. These data indicate that eukaryotic viruses have the capacity to support intestinal homeostasis and shape mucosal immunity, similarly to commensal bacteria.

Show MeSH
Related in: MedlinePlus