Interferon treatment suppresses enteric adenovirus infection in a model gastrointestinal cell-culture system

Curcumin dispersed with colloidal nano-particles inhibits enteric viruses replication

Acute gastroenteritis remains one of the most common health problems despite the progress in prevention and vaccination. The options for viral diarrhea therapy are limited and there is the need for effective treatment. Recently a novel form of the nano-dispersed curcumin that is highly bioavailable was described. This form of curcumin was well tolerated by the cells in culture and was rapidly absorbed into the blood plasma after oral administration. We tested the antiviral activity of this curcumin formulation in vitro using several viruses associated with gastrointestinal infections, like astrovirus, norovirus rotavirus, adenovirus, echovirus, and coxackievirus. We did observe strong replication inhibition of all tested viruses. These results suggest that the tested form of curcumin is a promising candidate for a broad-spectrum antiviral drug.

Intestinal HAdV Infection: Tissue Specificity, Persistence, and Implications for Antiviral Therapy

Human adenovirus (HAdV) causes infections predominantly in early childhood and the tissue tropism of specific HAdV species determines the clinical manifestation, including infections of the gastrointestinal tract, respiratory tract, and keratoconjunctivitis. Why HAdV shows such a tropism has not yet been fully elucidated, but in the intestine different mechanisms for virus entry or resistence to immune modulatory factors have been described. Recently identified antiviral strategies by interferons provide evidence about the repression of E1A and maybe even promote HAdV persistence. The presence of HAdV in a persistent status in the gut is of importance in the setting of pediatric stem cell transplant recipients where HAdV detection in stool usually preceds clinical signs and severe infections are related to mortality. The reactivation of persistent intestinal HAdV infections in these patients needs further investigation also with regard to successful therapy options. In addition, several newly identified recombinant HAdV types have been isolated from stool samples, thus raising the question of possible recombination events in the gut. In this review, intestinal HAdV infections are discussed in relation to the tissue tropism, persistence, recombination, and new in-vitro models to enhance the knowledge about virus–host interactions and support the development of new treatment approaches.

Distinct Effects of Type I and III Interferons on Enteric Viruses

Interferons (IFNs) are key host cytokines in the innate immune response to viral infection, and recent work has identified unique roles for IFN subtypes in regulating different aspects of infection. Currently emerging is a common theme that type III IFNs are critical in localized control of infection at mucosal barrier sites, while type I IFNs are important for broad systemic control of infections. The intestine is a particular site of interest for exploring these effects, as in addition to being the port of entry for a multitude of pathogens, it is a complex tissue with a variety of cell types as well as the presence of the intestinal microbiota. Here we focus on the roles of type I and III IFNs in control of enteric viruses, discussing what is known about signaling downstream from these cytokines, including induction of specific IFN-stimulated genes. We review viral strategies to evade IFN responses, effects of IFNs on the intestine, interactions between IFNs and the microbiota, and briefly discuss the role of IFNs in controlling viral infections at other barrier sites. Enhanced understanding of the coordinate roles of IFNs in control of viral infections may facilitate development of antiviral therapeutic strategies; here we highlight potential avenues for future exploration.

Type I Interferon Response Limits Astrovirus Replication and Protects against Increased Barrier Permeability In Vitro and In Vivo

Little is known about intrinsic epithelial cell responses against astrovirus infection. Here we show that human astrovirus type 1 (HAstV-1) infection induces type I interferon (beta interferon [IFN-β]) production in differentiated Caco2 cells, which not only inhibits viral replication by blocking positive-strand viral RNA and capsid protein synthesis but also protects against HAstV-1-increased barrier permeability. Excitingly, we found similar results in vivo using a murine astrovirus (MuAstV) model, providing new evidence that virus-induced type I IFNs may protect against astrovirus replication and pathogenesis in vivo.

IMPORTANCE

Human astroviruses are a major cause of pediatric diarrhea, yet little is known about the immune response. Here we show that type I interferon limits astrovirus infection and preserves barrier permeability both in vitro and in vivo. Importantly, we characterized a new mouse model for studying astrovirus replication and pathogenesis.

Construction of high-quality Caco-2 three-frame cDNA library and its application to yeast two-hybrid for the human astrovirus protein-protein interaction

Human epithelial colorectal adenocarcinoma (Caco-2) cells are widely used as an in vitro model of the human small intestinal mucosa. Caco-2 cells are host cells of the human astrovirus (HAstV) and other enteroviruses. High quality cDNA libraries are pertinent resources and critical tools for protein-protein interaction research, but are currently unavailable for Caco-2 cells. To construct a three-open reading frame, full length-expression cDNA library from the Caco-2 cell line for application to HAstV protein-protein interaction screening, total RNA was extracted from Caco-2 cells. The switching mechanism at the 5' end of the RNA transcript technique was used for cDNA synthesis. Double-stranded cDNA was digested by Sfi I and ligated to reconstruct a pGADT7-Sfi I three-frame vector. The ligation mixture was transformed into Escherichia coli HST08 premium electro cells by electroporation to construct the primary cDNA library. The library capacity was 1.0×10(6)clones. Gel electrophoresis results indicated that the fragments ranged from 0.5kb to 4.2kb. Randomly picked clones show that the recombination rate was 100%. The three-frame primary cDNA library plasmid mixture (5×10(5)cfu) was also transformed into E. coli HST08 premium electro cells, and all clones were harvested to amplify the cDNA library. To detect the sufficiency of the cDNA library, HAstV capsid protein as bait was screened and tested against the Caco-2 cDNA library by a yeast two-hybrid (Y2H) system. A total of 20 proteins were found to interact with the capsid protein. These results showed that a high-quality three-frame cDNA library from Caco-2 cells was successfully constructed. This library was efficient for the application to the Y2H system, and could be used for future research.

Enhanced growth of recombinant human adenovirus type 41 (HAdV-41) carrying ADP gene

Human adenovirus type 41 (HAdV-41) has the potential to be constructed as a gene transfer vector for oral vaccine or gene therapy targeting gastrointestinal tract. Block in release of progeny virus from host cell severely affects the yield during virus amplification. In this study, HAdV-5 adenovirus death protein (ADP) gene was used to replace the open reading frames (ORFs) of the HAdV-41 E3 region to construct a backbone plasmid pAdbone41ADP. Recombinant adenoviral plasmids harboring ADP and GFP genes (pAd41ADP-GFP) were generated. Plaques were formed and HAdV-41-ADP-GFP virus was rescued after transfecting pAd41ADP-GFP into the packaging cell line 293TE32. When amplified on 293TE32 cells, HAdV-41-ADP-GFP virus released to the culture medium was 10-50 times more than control virus HAdV-41-GFP, which did not carry ADP gene. The results demonstrated that incorporation of the ADP gene substantially increased the yield of recombinant HAdV-41 virus through enhancing spread of progeny virus among packaging cells.