Background: Recent recognition of invasive astrovirus infections, including encephalitis and viremia in humans, have highlighted the need for effective anti-astrovirus therapeutics. However, there is a paucity of data regarding the in vitro activity of broad-spectrum RNA antivirals against astroviruses, including ribavirin and favipiravir. Objectives: We quantified the EC50 values for ribavirin and favipiravir against two human astrovirus strains, astrovirus VA1 (VA1) and human astrovirus 4 (HAstV4). Study Design: Caco-2 cells were infected with VA1 or HAstV4 in the presence of ribavirin or favipiravir (dose range 0.1-1000 mu M), and the cells were maintained in media containing the drugs for 72 h. Viral RNA was extracted and quantified by qRT-PCR. As a surrogate for cytotoxicity, cellular adenosine triphosphate (ATP) from each drug treatment was also measured. Results: VA1 replication was inhibited 10-100-fold by both ribavirin (EC50 = 154 mu M) and favipiravir (EC50 = 246 mu M). In contrast, ribavirin inhibited HAstV4 replication (EC50 = 268 mu M) but favipiravir only reduced replication by 44% at the highest dose. Mild reductions in ATP (17-31%) was only observed at the highest concentration of ribavirin (1000 mu M) and no significant decrease in ATP was detected for any concentration of favipiravir. Conclusions: Ribavirin inhibited both human astrovirus species and favipiravir was only active against VA1. In the future, the in vivo efficacy of these drugs could be tested with development of an animal model of human astrovirus infection.

Next-generation sequencing (NGS) technologies are becoming increasingly accessible, leading to an expanded interest in the composition of the porcine enteric virome. In the present study, the fecal virome of a non-diarrheic Belgian piglet was determined. Although the virome of only a single piglet was analyzed, some interesting data were obtained, including the second complete genome of a pig group C rotavirus (RVC). This Belgian strain was only distantly related to the only other completely characterized pig RVC strain, Cowden. Its relatedness to RVC strains from other host species was also analyzed and the porcine strain found in our study was only distantly related to RVCs detected in humans and cows. The gene encoding the outer capsid protein VP7 belonged to the rare porcine G3 genotype, which might be serologically distinct from most other pig RVC strains. A putative novel RVC VP6 genotype was identified as well. A group A rotavirus strain also present in this fecal sample contained the rare pig genotype combination G11P[27], but was only partially characterized. Typical pig RVA genotypes I5, A8, and T7 were found for the viral proteins VP6, NSP1, and NSP3, respectively. Interestingly, the fecal virome of the piglet also contained an astrovirus and an enterovirus, of which the complete genomes were characterized. Results of the current study indicate that many viruses may be present simultaneously in fecal samples of non-diarrheic piglets. In this study, these viruses could not be directly associated with any disease, but still they might have had a potential subclinical impact on pig growth performance. The fast evolution of NGS will be a powerful tool for future diagnostics in veterinary practice. Its application will certainly lead to better insights into the relevance of many (sub) clinical enteric viral infections, that may have remained unnoticed using traditional diagnostic techniques. This will stimulate the development of new and durable prophylactic measures to improve pig health and production. (C) 2016 Elsevier B.V. All rights reserved.