Astrovirus
Dongyou Liu in Laboratory Models for Foodborne Infections, 2017
Since the Astroviridae family was established by the ICTV in 1995, there have been considerable changes in our understanding of the diversity, molecular evolution, and host range of the family. In just the last decade, the numbers of host species detected with astroviruses have increased more than fourfold.22 Additionally our appreciation of the diversity of astrovirus genotypes capable of infecting a given host has led to a reevaluation of their classification system. Currently, Astroviridae is divided into two genera (Table 3.1), Mamastrovirus (MAstV) and Avastrovirus (AAstV), representing viruses that affect mammals and avian species, respectively. Within each of these two genera, viruses are classified by distinct genotypic differences within their polymerase and/or capsid genomic sequences.23
Astrovirus
Dongyou Liu in Handbook of Foodborne Diseases, 2018
After the virus was first sequenced in 1993, it was proposed that these unique enteric pathogens be classified under a new family: Astroviridae.11 The International Committee on Taxonomy of Viruses divides Astroviridae into two genera according to species specificity12: Avastrovirus infects avian species and Mamastrovirus infects mammalian species (Figure 3.1). Both genera are subdivided into two genogroups on the basis of their genetic relatedness within the ORF2 gene, which encodes the highly variable capsid protein. These genogroups are further classified into individual genotypes according to their mean amino acid distance.
Other Positive Single-Stranded RNA Viruses
Paul Pumpens, Peter Pushko, Philippe Le Mercier in Virus-Like Particles, 2022
According to the current taxonomy (ICTV 2020), the order Stellavirales is one of the two members of the class Stelpaviricetes, together with the Patatavirales order described in the neighboring Chapter 29. The Stelpaviricetes class belongs to the Pisuviricota phylum from the kingdom Orthornavirae, realm Riboviria. The small Stellavirales order currently involves a single family Astroviridae with two genera Avastrovirus and Mamastrovirus and 22 species altogether. Human astrovirus (HAstV) is an important cause of acute gastroenteritis.
Vaccines against gastroenteritis, current progress and challenges
Published in Gut Microbes, 2020
Hyesuk Seo, Qiangde Duan, Weiping Zhang
Progress has been also made in vaccine development for the other enteric viruses including astroviruses (Astroviridae), adenoviruses (Adenoviridae), and sapoviruses (Caliciviridae). Other Astroviridae members such as VA-Like and MLB-like astroviruses, Picornaviridae (silivirus, cosavirus), and Parvoviridae families (bocaviruses, bufaviruses) are also isolated from patients (usually in infants and children) with gastroenteritis. Several subunit vaccines have been investigated for prevention against astrovirus infections. In particular, a trivalent subunit vaccine for hepatitis E virus, norovirus, and astrovirus was generated by fusing together the dimeric P domains of the three viruses to form a tetramer.93 When intranasally administered to mice, this trivalent product induced significant neutralizing antibody responses to the P domains of all three viruses. Another subunit astrovirus vaccine candidate used the capsid protein (CP) of mink astrovirus elicited high levels of serum anti-CP antib odies and lymphoproliferation responses and also stimulated IFN-γ levels in mice.94 Importantly, it was observed that virus shedding was suppressed and clinical signs including severe diarrhea were reduced in the litters born to the immunized mink mothers when challenged with a heterogeneous astrovirus strain.94 Future human volunteer studies and clinical trials are needed to assess the efficacy of these vaccine candidates against viral gastroenteritis.
Progress on norovirus vaccine research: public health considerations and future directions
Published in Expert Review of Vaccines, 2018
Claire P. Mattison, Cristina V. Cardemil, Aron J. Hall
The Cincinnati Children’s Hospital Medical Center, University of Cincinnati, and Virginia Polytechnic Institute and State University are developing a norovirus vaccine using norovirus P particles, designed to resemble the protruding P domain of the virus [60,61]. Development began on a monovalent GII.4 norovirus vaccine, but as it progressed, hepatitis E and astrovirus antigens were added. A trial of an intranasal GII.4 norovirus P particle vaccine in gnotobiotic pigs showed a higher intestinal T-cell immune response when compared to pigs vaccinated with a GII.4 norovirus VLP vaccine [90]. In mice, an intranasal bivalent vaccine using a fused P protein from the P domains of norovirus and hepatitis E showed increased antibody titers when compared to vaccination with a mixture of P dimers from norovirus and hepatitis E [91]. Most recently, a trivalent intranasal GII.4 norovirus, hepatitis E, and astrovirus vaccine, using a fusion of the three P domains, produced a 1.9-fold higher norovirus IgG titer than immunization with norovirus P particle alone in mice [92]. These trials show the potential for a P particle vaccine to vaccinate against multiple diseases.
Helminth–virus interactions: determinants of coinfection outcomes
Published in Gut Microbes, 2021
Pritesh Desai, Michael S. Diamond, Larissa B. Thackray
Another mechanism by which helminths could impact enteric viral infection is by modulating or expanding the specific cell types that viruses target. In the MNoV study, although a defect in AAM-mediated priming of virus-specific CD8+ T cells was implicated in enhanced viral burden, AAMs induced in vitro supported higher replication of MNoV.23 The possible skewing of AAMs by IL-4 compromises their innate antiviral functions, enabling viruses to replicate within them. Indeed, AAMs are less efficient than conventional macrophages in their ability to phagocytose antigens and kill engulfed pathogens.45 Helminth infection also results in the expansion of specific intestinal epithelial lineages including tuft cells and goblet cells, which have roles in the detection and clearance of luminal worms through a “weep and sweep” response.58,59 Coinfection of helminths and enteric viruses that have tropism for these specific cell types might result in greater numbers of susceptible target cells and increased viral infection. Notably, the MNoV strain CR6, which has tropism for tuft cells and shows higher levels of shedding following a coinfection with T. spiralis or during treatment with IL-4 complexes (IL-4 c).23,60 Similarly, coinfection with H. polygyrus enhanced murine astrovirus (muAstV) infection and shedding in the GI tract possibly due to an increased number of infected goblet cells, a target of muAstV.61 Thus, enteric helminth coinfection could be detrimental to the host by enhancing infection and transmission of some enteric viral infections (Table 2). Whether enteric helminth coinfection also enhances host susceptibility to other enteric viruses (e.g., rotavirus and enteroviruses) remains to be determined.