Ecological studies on reovirus pollution of rivers in Toyama Prefecture. II. Molecular epidemiological study of reoviruses isolated from river water

Surveillance of SARS-CoV-2 in Sewage Treatment Plants between January 2020 and July 2021 in Taiwan

An outbreak of a new type of coronavirus pneumonia (COVID-19) began in Wuhan, Hubei Province, China, at the end of 2019, and it later spread to other areas of China and around the world. Taiwan reported the first confirmed case from an individual who returned from Wuhan, China, in January 2020 for Chinese New Year. Monitoring microbes in environmental sewage is an important epidemiological indicator, especially for pathogens that can be shed in feces such as poliovirus. We have conducted additional SARS-CoV-2 sewage testing since January 2020 using a well-established poliovirus environmental sewage surveillance system in Taiwan. Wastewater samples were collected from 11 sewage treatment plants from different parts of Taiwan twice a month for laboratory testing. By the end of July 2021, 397 wastewater specimens had been tested, and two samples were positive for SARS-CoV-2. These two wastewater samples were collected in the northern region of Taiwan from Taipei (site A) and New Taipei City (site C) at the beginning of June 2021. This result is consistent with the significant increase in confirmed COVID-19 cases observed in the same period of time. As the pandemic ebbed after June, the wastewater samples in these areas also tested negative for SARS-CoV-2 in July 2021.

Intertypic reassortment of mammalian orthoreovirus identified in wastewater in Japan

Mammalian orthoreovirus (MRV), a non-enveloped virus with a ten-segmented double-stranded RNA genome, infects virtually all mammals, including humans. Human infection with MRV seems to be common in early childhood, but is rarely symptomatic. Despite the ubiquitous presence of MRV in mammals as well as in environmental waters, the molecular characterisation of the MRV genome remains to be fully elucidated. In this study, two novel strains, MRV-2 THK0325 and MRV-1 THK0617, were unintentionally isolated from wastewater in Japan via an environmental surveillance of enteric viruses. Homology and phylogenetic analysis demonstrated that all the segments of THK0325 were closely related to the MRV-2 Osaka strains, which were recently proposed to have existed for at least two decades in Japan. Most of the segments in THK0617 also showed a close relationship with the MRV-2 Osaka strains, but the M2, S1, and S3 segments belong to another MRV cluster. According to the S1 sequence, the determinant of serotype THK0617 was classified as MRV-1, and both the M2 and S3 segments were closely related to MRV-1 and -3 from the tree shrew in China. These results suggest that the MRV-2 Osaka-like strain spread widely throughout Japan, accompanied by intertypic reassortment occurring in East Asia.

Bat mammalian orthoreoviruses cause severe pneumonia in mice

Mammalian orthoreovirus (MRV) infections are ubiquitous in mammals. Increasing evidence suggests that some MRVs can cause severe respiratory disease and encephalitis in humans and other animals. Previously, we isolated six bat MRV strains. However, the pathogenicity of these bat viruses remains unclear. In this study, we investigated the host range and pathogenicity of 3 bat MRV strains (WIV2, 3 and 7) which represent three serotypes. Our results showed that all of them can infect cell lines from different mammalian species and displayed different replication efficiency. The BALB/c mice infected by bat MRVs showed clinical symptoms with systematic infection especially in lung and intestines. Obvious tissue damage were found in all infected lungs. One of the strains, WIV7, showed higher replication efficiency in vitro and vivo and more severe pathogenesis in mice. Our results provide new evidence showing potential pathogenicity of bat MRVs in animals and probable risk in humans.

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Bat MRVs show wide cell tropism in vivo and in vitro and have a high replication efficiency in lung and intestines.

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Mice infected by bat MRVs showed clinical illness, but without death.

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The higher replication in brain, lung damage and weak innate immune response may be responsible for severe diseases for WIV7.

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The results indicate the potential pathogenicity of bat MRV to human and animals.

Novel human reovirus isolated from children and its long-term circulation with reassortments

Mammalian orthoreovirus (MRV), also known as reovirus, was discovered in the 1950s and became the first reported segmented double-stranded RNA virus. MRVs have since been found in a variety of animal species, including humans. However, reports on MRV infections are scarce due to the rarity of their symptomatic occurrence. In Japanese surveillance studies, MRVs have been detected as gastrointestinal pathogens since 1981, with a total of 135 records. In Osaka City, Japan, MRV was first isolated in 1994 from a child with meningitis, and then in 2005 and 2014 from children with gastroenteritis. Here, we conducted the first molecular characterization of human MRV isolates from Japan and identified a novel human reovirus strain belonging to MRV type 2, designated the MRV-2 Osaka strain. This strain, with all three isolates classified, is closely related to MRV-2 isolates from sewage in Taiwan and is relatively close to an MRV-2 isolate from a bat in China. Our data suggest that the MRV-2 Osaka strain, which has circulated amongst humans in Japan for at least two decades, has spread internationally.

High Incidence of Mammalian Orthoreovirus Identified by Environmental Surveillance in Taiwan

Wild poliovirus (WPV) persists in diverse locales worldwide, spreading outward from endemic areas. In response to the international threat of WPV transmission and changes in the national vaccination policy, we established an environmental surveillance system to monitor the circulation of wild and vaccine-related poliovirus in Taiwan. From July 2012 to December 2013, we collected sewage specimens every month from 10 sewage treatment plants located throughout Taiwan. The specimens were concentrated by the two-phase separation method and then inoculated into L20B, RD, and A549 cells for virus isolation. Viral isolates were identified and serotyped by immunofluorescence assay or molecular analysis. A total of 300 sewage samples were collected, and the results showed 163 samples (54.3%) were positive for virus, and 268 isolates were identified. Among these, 75 samples (25%) were positive for enterovirus (EV), but no poliovirus was found. In addition, 92 isolates were identified as enteroviruses and the most common serotypes were coxsackievirus B4, coxsackievirus B3, and coxsackievirus B2. Interestingly, 102 (34%) and 82 (27.3%) specimens were positive for mammalian orthoreovirus (MRV) and adenovirus, respectively. This study confirmed that sewage surveillance can be a useful additional modality for monitoring the possible presence of wild-type or vaccine-derived poliovirus in wastewater, and can indicate the current types of viruses circulating in the population. Furthermore, since MRV was found in children with acute necrotizing encephalopathy and meningitis, the high incidence of MRV detected by environmental surveillance warrants further investigation.

Reovirus serotypes elicit distinctive patterns of recall immunity in humans

Mammalian orthoreoviruses (reoviruses) are ubiquitous viral agents that infect cells in respiratory and enteric tracts. The frequency and nature of human cellular immunoregulatory responses against reovirus are unknown. Here we establish systems to detect and quantify reovirus-induced cytokine and chemokine recall responses using primary cultures of virus-infected peripheral blood mononuclear cells (PBMC) and two widely used reovirus serotypes, type 1 Lang (T1L) and type 3 Dearing (T3D) reexposure in vitro. In cultures from 44 healthy adults, reovirus induced exceptionally strong CD4 and CD8 T-cell-dependent gamma interferon (IFN-gamma) recall responses concomitant with intense interleukin 10 (IL-10) production. These responses were elicited independently of viral replication. Surprisingly, paired analyses of subject responses to these two common serotypes revealed that while both elicit intense Th1-dominated immunity, median T3D-driven responses were 2.2-fold weaker (P = 0.0004) than those elicited by T1L. Recall responses evoked by these viral serotypes differed markedly in their mechanism of regulation. T3D IL-10 and IFN-gamma responses were CD4 and CD8 dependent and blocked by interfering with CD86 costimulation but were CD80 independent. T1L responses were consistently CD28 and CD80/86 independent. Thus, despite extensive genetic and morphological similarities between reovirus serotypes, the nature and intensity of the human recall responses as well as the control mechanisms regulating them are clearly distinct.

Chapter 7 Global Supply of Virus-Safe Drinking Water

This chapter illustrates the recommendations and guidelines of the World Health Organization (WHO) concerning water, sanitation, and health. The recommendations and guidelines are evaluated in the light of disease caused by human pathogenic viruses. The guidelines outline a preventive management framework for safe drinking water. The framework includes health-based targets to assist national authorities who are normally responsible to set the targets for the protection of public health from risks by exposure to drinking water. Assessing the adequacy of systems, defining and monitoring control measures, and establishing management plans are the three components of the so-called water safety plans. Achievement of health-based targets may be verified by independent surveillance to assess the safety of the drinking water through additional verification or audit-based approaches. This framework for safe drinking water can be adapted according to environmental, social, economic, and cultural circumstances of drinking water provision on the national, regional, and local level. The chapter concludes that viruses could be considered as biocolloids with specific properties such as size, shape, structure, charge, composition, and genome. These viral characteristics determine their behavior in the environment, resistance to natural inactivation and treatment, and disinfection processes. For each (re-)emerging virus these properties may be known or could be assessed predicting the effectiveness of possible intervention measures for prevention of waterborne disease.

Presence of noroviruses and other enteric viruses in sewage and surface waters in The Netherlands

Since virus concentrations in drinking waters are generally below the detection limit, the infectious risk from drinking water consumption requires assessment from the virus concentrations in source waters and removal efficiency of treatment processes. In this study, we estimated from reverse transcription-PCR on 10-fold serially diluted RNA that noroviruses, the most prevalent waterborne gastroenteritis agents, were present at 4 (0.2 to 38) to 4,900 (303 to 4.6 x 10(4)) PCR-detectable units (PDU) per liter of river water (ranges are given in parentheses). These virus concentrations are still high compared with 896 to 7,499 PDU/liter of treated sewage and 5,111 to 850,000 PDU/liter in raw sewage. Sequencing analyses designated human norovirus GGII.4 Lordsdale as the most prevalent strain in the sampling period 1998 to 1999 in both sewage and surface waters. Other GGII strains were also very abundant, indicating that the majority of the virus contamination was derived from urban sewage, although very divergent strains and one animal strain were also detected in the surface and sewage waters. Rotaviruses were also detected in two large rivers (the Maas and the Waal) at 57 to 5,386 PDU/liter. The high virus concentrations determined by PCR may in part be explained by the detection of virus RNA instead of infectious particles. Indeed, reoviruses and enteroviruses that can be cultured were present at much lower levels, of 0.3 to 1 and 2 to 10 PFU/liter, respectively. Assuming 1% of the noroviruses and rotaviruses to be infectious, a much higher disease burden than for other viruses can be expected, not only because of the higher levels but also because of these viruses' higher infectivity and attack rates.

Mycophenolic acid inhibits replication of Type 2 Winnipeg, a cerebrospinal fluid-derived reovirus isolate

BACKGROUND

The role of reoviruses in human disease is uncertain. Most identified cases are sporadic and asymptomatic or produce minor upper respiratory or gastrointestinal symptoms. In November 1997, a reovirus was isolated from the cerebrospinal fluid of a severe combined immune deficient infant in Winnipeg, Manitoba. RNA characterization and sequencing studies demonstrated this reovirus isolate to be unique. Thus, the virus was named Type 2 Winnipeg (T2W).

OBJECTIVE

Mycophenolic acid (MPA), a drug primarily used as an immunosuppressive agent, was assessed in the capacity to inhibit T2W viral growth.

METHODS

The effects of MPA on viral growth were determined by plaque reduction assays. Cells were treated with different MPA concentrations, infected with T2W and incubated at 37 degrees C for 0 h to 72 h. Virus titres were determined and compared with untreated controls.

RESULTS

Production of infectious T2W progeny decreased more than 99% at 3 microg/mL MPA compared with untreated controls. Inhibition was not caused by cell toxicity because there was no difference in cell viability. The 50% cell toxic dose was 30 microg/mL MPA.

CONCLUSIONS

MPA was able to inhibit viral growth of the novel reovirus T2W. Although MPA is usually used as an immunosuppressive agent, and despite the fact that T2W was isolated from an immunocompromised patient, these results suggest that MPA could have been used as a possible treatment at subimmunosuppressive doses. Animal studies to better define the antiviral and immunosuppressive activities of MPA (and its prodrug mycophenolate mofetil) appear warranted.

Reovirus type 2 isolated from cerebrospinal fluid

An 8-week-old female infant presented with a history of active varicella complicated by Escherichia coli sepsis, oral thrush, hypoalbuminemia, intermittent fevers, diarrhea and feeding intolerance. Rhesus monkey kidney cells inoculated with cerebrospinal fluid revealed reovirus-like particles by electron microscopy. Virus neutralization and RNA-gel electrophoresis studies identified the isolated pathogen as reovirus serotype 2. This report represents one of only a few to isolate reovirus from the central nervous system in humans.

Detection of mammalian reovirus RNA by using reverse transcription-PCR: sequence diversity within the lambda3-encoding L1 gene

Reoviruses infect virtually all mammalian species, and infection of humans is associated with mild gastrointestinal or upper respiratory illnesses. To improve reovirus detection strategies, we developed a reverse transcription-PCR technique to amplify a fragment of the reovirus L1 gene segment. This assay was capable of detecting 44 of 44 reovirus field isolate strains and was sufficiently sensitive to detect nearly a single viral particle (1.16 +/- 0.13) per PCR of prototype strain type 3 Dearing. Pairwise comparisons of the 44 partial L1 gene sequences revealed that nucleotide variability ranged from 0 to 24.7%, with most of the nucleotide polymorphism occurring at synonymous positions. Phylogenetic trees generated from amplified L1 gene sequences suggest that multiple alleles of the L1 gene cocirculate in nature and that genetic diversity of the L1 gene is largely independent of the host species, geographic locale, or date of isolation. Phylogenetic trees constructed from the L1 gene sequences are distinct from those constructed from the four reovirus S-class gene segments, which supports the hypothesis that reovirus gene segments reassort in nature. This study establishes a new sensitive and specific technique for the identification of mammalian reoviruses and enhances our understanding of reovirus evolution.

Assessment of poliovirus eradication in Japan: genomic analysis of polioviruses isolated from river water and sewage in toyama prefecture

Seventy-eight poliovirus strains isolated from river water and sewage in Toyama Prefecture, Japan, during 1993 to 1995 were characterized by the PCR-restriction fragment length polymorphism (RFLP) method and by partially sequencing the VP3 and VP1 regions of the viral genome. Of these isolates, 36 were identified as Sabin vaccine strains, and 42 were identified as vaccine variant strains that had less than 1.4% nucleotide divergence from the Sabin strains, including 7 isolates with patterns different from those of Sabin strains as determined by PCR-RFLP analysis. These findings suggest that wild-type poliovirus was not circulating in Toyama Prefecture.

Seasonal distribution of adenoviruses, enteroviruses and reoviruses in urban river water

In the 63-month period from January 1988 to March 1993, monthly levels of adenoviruses, enteroviruses (coxsackie B, polio, echo) and reoviruses in the urban river water in Nara Prefecture, Japan were in the range 0-25, 0-190 and 0-325, plaque forming units per liter (PFU/liter), and the average levels were 2.4, 40.6 and 56.2 PFU/liter, respectively. The peak reovirus level was found in winter during the cold weather months (Nov. to Mar.). The peak enterovirus level was found in summer (May to Sept.) but continued to be found in autumn-winter (Oct. to Jan.) from 1991 to 1993. The levels of adenoviruses were low throughout all 5 years, as compared to those of reoviruses and enteroviruses. Polioviruses were isolated following the administration of vaccine. Although a changing pattern of serotype prevalence was seen with the coxsackie B viruses and echoviruses from 1988 to 1993, this is not so for polioviruses, which remained almost unchanged for the five-year period. Adenoviruses were isolated throughout all five years, though in small numbers. Reoviruses were isolated most frequently throughout five years.

The Reoviridae family

The members of the Reoviridae family are extremely varied in host ranges and have such diverse natural histories that it is compelling to conclude that their structural asset and replication strategy are uniquely successful in evolutionary terms. It follows that their study addresses fundamental aspects of virology, besides the ones which are customary with important pathogens affecting humans, animals and plants. We deal here with the present taxonomy of the family Reoviridae and of its genera, two of which (Orbivirus and Rotavirus) are treated separately in this issue. Along with a cursory presentation of the remaining genera, we give a concise update of recent findings on the genus Orthoreovirus.