Saffold Virus Research Articles

Viruses in Vietnamese Patients Presenting with Community-Acquired Sepsis of Unknown Cause.

Community-acquired (CA) sepsis is a major public health problem worldwide, yet the etiology remains unknown for >50% of the patients. Here we applied metagenomic next-generation sequencing (mNGS) to characterize the human virome in 492 clinical samples (384 sera, 92 pooled nasal and throat swabs, 10 stools, and 6 cerebrospinal fluid samples) from 386 patients (213 adults and 173 children) presenting with CA sepsis who were recruited from 6 hospitals across Vietnam between 2013 and 2015. Specific monoplex PCRs were used subsequently to confirm the presence of viral sequences detected by mNGS. We found sequences related to 47 viral species belonging to 21 families in 358 of 386 (93%) patients, including viruses known to cause human infections. After PCR confirmation, human viruses were found in 52 of 386 patients (13.4%); picornavirus (enteroviruses [n = 14], rhinovirus [n = 5], and parechovirus [n = 2]), hepatitis B virus (n = 10), cytomegalovirus (n = 9), Epstein-Barr virus (n = 5), and rotavirus A (n = 3) were the most common viruses detected. Recently discovered viruses were also found (gemycircularvirus [n = 5] and WU polyomavirus, Saffold virus, salivirus, cyclovirus-VN, and human pegivirus 2 [HPgV2] [n, 1 each]), adding to the growing literature about the geographic distribution of these novel viruses. Notably, sequences related to numerous viruses not previously reported in human tissues were also detected. To summarize, we identified 21 viral species known to be infectious to humans in 52 of 386 (13.4%) patients presenting with CA sepsis of unknown cause. The study, however, cannot directly impute sepsis causation to the viruses identified. The results highlight the fact that it remains a challenge to establish the causative agents in CA sepsis patients, especially in tropical settings such as Vietnam.

Frequent detection of Saffold cardiovirus in adenoids.

Saffold virus (SAFV) is classified into the Cardiovirus genus of the Picornaviridae family. Up to now, eleven genotypes have been identified however, their clinical significance remains unclear. Here, we investigated the presence of SAFV in asymptomatic patients admitted for adenoidectomy. A total of 70 adenoid tissue samples were collected from children with clinical symptoms caused by hypertrophy of adenoids but without symptoms of airway infection. Samples were investigated for SAFV by RT-nested PCR and sequence analysis. Eleven of 70 (15.7%) samples were positive for SAFV. Nasopharyngeal swabs were available from 45 children just before surgery. SAFV was rarely found and only in children with SAFV-positive adenoids 2/8. Our findings indicate that the presence of SAFV seems to be more frequent in adenoid tissue than expected. This could support the notion of a longer than previously anticipated persistence of SAFV nucleic acids in the respiratory tract and possibly a chronic infection. Further investigations are necessary to establish the role of SAFV infection in humans.

The Saffold Virus-Penang 2B and 3C Proteins, but not the L Protein, Induce Apoptosis in HEp-2 and Vero Cells.

Our previous work has shown that Saffold virus (SAFV) induced several rodent and primate cell lines to undergo apoptosis (Xu et al. in Emerg Microb Infect 3:1-8, 2014), but the essential viral proteins of SAFV involved in apoptotic activity lack study. In this study, we individually transfected the viral proteins of SAFV into HEp-2 and Vero cells to assess their ability to induce apoptosis, and found that the 2B and 3C proteins are proapoptotic. Further investigation indicated the transmembrane domain of the 2B protein is essential for the apoptotic activity and tetramer formation of the 2B protein. Our research provides clues for the possible mechanisms of apoptosis induced by SAFV in different cell lines. It also opens up new directions to study viral proteins (the 2B, 3C protein), and sets the stage for future exploration of any possible link between SAFV, inclusive of its related uncultivable genotypes, and multiple sclerosis.

Longitudinal Epidemiology of Viral Infectious Diseases Combining Virus Isolation, Antigenic Analysis, and Phylogenetic Analysis as Well as Seroepidemiology in Yamagata, Japan, between 1999 and 2018.

We introduced a microplate method for virus isolation in the Department of Microbiology, Yamagata Prefectural Institute of Public Health (YPIPH) in 1999 in Yamagata, Japan. We have since carried out longitudinal epidemiological studies on viral infectious diseases, particularly respiratory viruses, combining traditional technologies such as virus isolation and serological techniques and newly developed molecular methods. Here, we provide an overview of our activities at YPIPH between 1999 and 2018. During the study period, we observed emerging and re-merging diseases such as those caused by echovirus type 13, enterovirus D68, parechovirus-A3 (PeV-A3), and Saffold virus. With regard to PeV-A3, we proposed a new disease concept, "PeV-A3-associated myalgia/myositis." We also revealed the longitudinal epidemiologies of several viruses such as enterovirus A71 and coxsackievirus A16. To perform longitudinal epidemiological studies at any time in Yamagata, we established a system for stocking clinical specimens, viral isolates, complementary DNAs, and serum specimens. We have also pursued collaboration works with virology laboratories across Japan. We hope our experiences, findings, and research materials will further contribute to the development of countermeasures against viral infectious diseases and improvement in public health strategies in Yamagata, Japan, Asia, and around the world.

Recombination Located over 2A-2B Junction Ribosome Frameshifting Region of Saffold Cardiovirus.

Here we report the nearly full-length genome of a recombinant Saffold virus strain (SAFV-BR-193) isolated from a child with acute gastroenteritis. Evolutionary analysis performed using all available near-full length Saffold picornavirus genomes showed that the breakpoint found in the Brazilian strain (SAFV-BR-193) is indeed a recombination hotspot. Notably, this hotspot is located just one nucleotide after the ribosomal frameshift GGUUUUU motif in the SAFV genome. Empirical studies will be necessary to determine if this motif also affects the binding affinity of RNA-dependent RNA-polymerase (RdRp) and therefore increases the changes of RdRp swap between molecules during the synthesis of viral genomes.

Prevalence of human cosavirus and saffold virus in young children with gastroenteritis, Northern Italy

Gastroenteritis is a common disease in children, characterized by diarrhea, vomiting, abdominal pain, and fever. Human Cosavirus (HCoSV) and Saffold virus (SAFV) both have a worldwide distribution. Both viruses have been detected in the stools of patients with acute gastroenteritis in several countries. In order to provide more insights into the epidemiology of enteric viruses that are not included usually in routine diagnostic tests, cases of childhood sporadic gastroenteritis of unknown etiology requiring hospital admission in Turin, Italy, during December 2014 to November 2015, were screened for HCoSV and SAFV. A total of 1 out of 164 (0.6%) episodes of acute gastroenteritis were associated with SAFV genomic detection. Among the 1 SAFV-positive cases, 1 were also positive for adenovirus. The patient positive for SAFV don't present diarrheal episodes but vomiting. HCoSV was not detected in any of the samples. In conclusion, this study presents the current epidemiological data regarding the two viruses, HCoSV and SAFV, circulating in pediatric patients admitted to hospital with acute gastroenteritis in Turin, Italy.

Detection of nineteen enteric viruses in raw sewage in Japan

One-year surveillance for enteric viruses in raw sewage was conducted in Kansai area, central part of Japan from July 2015 to June 2016. The raw sewage was collected monthly from an inlet polluted pool and was concentrated by polyethylene glycol (PEG) precipitation. Twelve sewage samples were screened for nineteen kinds of enteric viruses by using RT-PCR method and further analyzed by nucleotide sequencing. Twelve enteric viruses were found in the investigative sewage samples. Rotavirus A and norovirus GI and GII with several genotypes were detected all year round. Interestingly, norovirus GII.17 (Kawasaki-like strain) and rotavirus G2 that caused the outbreaks in Japan last epidemic season were also found in sewage. Moreover, adenovirus, astrovirus, sapovirus, bocavirus, human parechovirus, enterovirus, Aichi virus, Saffold virus and salivirus were also detected. Enterovirus D68 was detected only in the same month as those of enterovirus D68 outbreak in Japan. The rotavirus B and C, hepatitis A and E viruses, human cosavirus, bufavirus and rosavirus were not detected in this surveillance. The study provides the information on the enteric viruses contaminated in raw sewage, which is valuable for risk assessment. Our results imply that the viruses detected in sewage may be associated with infections in the Japanese population.

Detection of Saffold viruses from children with acute respiratory infections in Yamagata, Japan, between 2008 and 2015.

Although Saffold virus (SAFV) was reported as a novel human cardiovirus in 2007, no causative association between SAFV and clinical disease has been proven and the longitudinal epidemiology of SAFVs is not available. To establish the relationship between SAFVs and acute respiratory infections (ARIs) and to clarify the longitudinal epidemiology of SAFVs, 7258 nasopharyngeal specimens were collected from children with ARIs in Yamagata, Japan between 2008 and 2015. The specimens were inoculated on a microplate including six cell lines as part of routine surveillance, and molecular screening was performed for SAFVs using a reverse transcription (RT)-PCR method. Throughout the study period, 95 (1.3%) SAFV genotype 2 (SAFV2), and 28 (0.4%) SAFV3 were detected, mainly between September and November. There were two outbreaks of SAFV2 in 2009 and 2013, and one outbreak of SAFV3 in 2012 and the positive rates during these outbreaks were 12.1% (53/439), 11% (35/319), and 4.4% (20/453), respectively. Sixty-three SAFV2 and 28 SAFV3 strains were detected as a single virus from children with ARIs such as pharyngitis, herpangina, and tonsillitis. These results suggested that SAFV2 and SAFV3 are possible causative agents of ARIs among children and their infections occur mainly in the autumn season in Japan.

Nonstructural Protein L* Species Specificity Supports a Mouse Origin for Vilyuisk Human Encephalitis Virus.

Vilyuisk human encephalitis virus (VHEV) is a picornavirus related to Theiler's murine encephalomyelitis virus (TMEV). VHEV was isolated from human material passaged in mice. Whether this VHEV is of human or mouse origin is therefore unclear. We took advantage of the species-specific activity of the nonstructural L* protein of theiloviruses to track the origin of TMEV isolates. TMEV L* inhibits RNase L, the effector enzyme of the interferon pathway. By using coimmunoprecipitation and functional RNase L assays, the species specificity of RNase L antagonism was tested for L* from mouse (DA) and rat (RTV-1) TMEV strains as well as for VHEV. Coimmunoprecipitation and functional assay data confirmed the species specificity of L* activity and showed that L* from rat strain RTV-1 inhibited rat but not mouse or human RNase L. Next, we showed that the VHEV L* protein was phylogenetically related to L* of mouse viruses and that it failed to inhibit human RNase L but readily antagonized mouse RNase L, unambiguously showing the mouse origin of VHEV.IMPORTANCE Defining the natural host of a virus can be a thorny issue, especially when the virus was isolated only once or when the isolation story is complex. The species Theilovirus includes Theiler's murine encephalomyelitis virus (TMEV), infecting mice and rats, and Saffold virus (SAFV), infecting humans. One TMEV strain, Vilyuisk human encephalitis virus (VHEV), however, was isolated from mice that were inoculated with cerebrospinal fluid of a patient presenting with chronic encephalitis. It is therefore unclear whether VHEV was derived from the human sample or from the inoculated mouse. The L* protein encoded by TMEV inhibits RNase L, a cellular enzyme involved in innate immunity, in a species-specific manner. Using binding and functional assays, we show that this species specificity even allows discrimination between TMEV strains of mouse and of rat origins. The VHEV L* protein clearly inhibited mouse but not human RNase L, indicating that this virus originates from mice.

Prevalence of human cosavirus and saffold virus with an emergence of saffold virus genotype 6 in patients hospitalized with acute gastroenteritis in Chiang Mai, Thailand, 2014–2016

Human cosavirus and saffold virus are both newly discovered members of the Picornaviridae family. It has been suggested that these viruses may be the causative agents of acute gastroenteritis. In this study, 1093 stool samples collected from patients with acute gastroenteritis between January 2014 and December 2016, were screened for cosavirus and saffold virus using reverse transcription-polymerase chain reaction. The viral genotypes were then established via nucleotide sequencing. Here, cosavirus was detected in 16 of 1093 stool samples (1.5%) and saffold virus was detected in 18 of 1093 stool samples (1.6%). The saffold virus genotypes 1 (16.7%), 2 (50%) and 6 (33.3%), and the cosavirus genetic groups A (87.5%), C (6.25%) and D (6.25%), were all identified across the three-year study period. Interestingly, saffold virus genotype 6 has now been detected for the first time in Thailand. The present study provides the prevalence of cosavirus and saffold virus with the emergence of saffold virus genotype 6 in Thailand.

Analysis of Aichi virus and Saffold virus association with pediatric acute gastroenteritis

BackgroundAichi virus (AiV) and Saffold virus (SAFV) have been reported in children with acute gastroenteritis and respiratory disease worldwide; however, their causative role in acute gastroenteritis remains ambiguous. ObjectivesTo assess the clinical association of AiV and SAFV with acute gastroenteritis in the pediatric population. Study designA case-control study involving 461 paired stool samples from pediatric cases with diarrhea and healthy controls was conducted in China. Quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) was used to screen AiV and SAFV. ResultsIn the 461 paired samples, AiV and SAFV were more prevalent among asymptomatic children than children with acute gastroenteritis (0.87% vs. 0.43% and 2.8% vs. 1.5%, respectively), with no significant differences between groups (p=0.142 and p=0.478, respectively). Cox regression model analysis revealed no correlation between AiV (odds ratio, OR=2.24; 95% confidence interval, CI, 0.76–6.54) or SAFV infection (OR=1.36; 95% CI, 0.86–2.15) and diarrhea. High viral loads were found in both AiV- and SAFV-positive groups, with no significant difference in viral load between the groups (p=0.507 and p=0.677, respectively). No other known enteric pathogens were found in the AiV-positive samples but common in SAFV-positive cases. Phylogenetic analysis revealed that all 6 AiV subjects clustered with genotype B. All 7 SAFV-positive cases and 8 of 13 SAFV-positive controls were genotyped successfully; the genotypes identified included SAFV-1, SAFV-2 SAFV-3, and SAFV-6. ConclusionOur study revealed no association of these viruses in acute gastroenteritis in children. These viruses may have the ability to replicate in humans; however, the infections are usually asymptomatic.

Immunohistochemical insights into Saffold virus infection of the brain of juvenile AG129 mice.

BackgroundSaffold Virus (SAFV) is a human cardiovirus that is suspected of causing infection of the central nervous system (CNS) in children. While recent animal studies have started to elucidate the pathogenesis of SAFV, very little is known about the mechanisms behind it.MethodIn this study, we attempted to elucidate some of the mechanisms of the pathogenesis of SAFV in the brain of a juvenile mouse model by using immunohistochemical methods.ResultsWe first showed that SAFV is able to infect both neuronal and glial cells in the brain of 2 week-old AG129 mice. We then showed that SAFV is able to induce apoptosis in both neuronal and glial cells in the brain. Lastly, we showed that SAFV infection does not show any signs of gross demyelination in the brain.ConclusionOverall, our results provide important insights into the mechanisms of SAFV in the brain.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-016-0654-8) contains supplementary material, which is available to authorized users.

Saffold virus, an emerging human cardiovirus

SummarySaffold virus (SAFV) is an emerging human cardiovirus that has been shown to be ubiquitous. Initial studies of SAFV focused on respiratory and gastrointestinal infection; however, it has also recently been associated with diverse clinical symptoms including the endocrine, cardiovascular, and neurological systems. Given the systemic nature of SAFV, and its high prevalence, understanding its pathogenicity and clinical impact is of utmost importance. This comprehensive review highlights and discusses recent developments in epidemiology, human pathogenicity, animal, and molecular studies related to SAFV. It also provides detailed insights into the neuropathogenicity of SAFV. We argue that human studies have been confounded by coinfections and therefore require support from robust molecular and animal research. Thereby, we aim to provide foresight into further research to better understand this emerging virus.

Neurotrophic potential of Saffold virus and the effects of its leader protein in the central nervous system of a mouse model

Neurotrophic potential of Saffold virus and the effects of its leader protein in the central nervous system of a mouse model

Intracerebral Inoculation of Mouse-Passaged Saffold Virus Type 3 Affects Cerebellar Development in Neonatal Mice.

Saffold virus (SAFV), a human cardiovirus, is occasionally detected in infants with neurological disorders, including meningitis and cerebellitis. We recently reported that SAFV type 3 isolates infect cerebellar glial cells, but not large neurons, in mice. However, the impact of this infection remained unclear. Here, we determined the neuropathogenesis of SAFV type 3 in the cerebella of neonatal ddY mice by using SAFV passaged in the cerebella of neonatal BALB/c mice. The virus titer in the cerebellum increased following the inoculation of each of five passaged strains. The fifth passaged strain harbored amino acid substitutions in the VP2 (H160R and Q239R) and VP3 (K62M) capsid proteins. Molecular modeling of the capsid proteins suggested that the VP2-H160R and VP3-K62M mutations alter the structural dynamics of the receptor binding surface via the formation of a novel hydrophobic interaction between the VP2 puff B and VP3 knob regions. Compared with the original strain, the passaged strain showed altered growth characteristics in human-derived astroglial cell lines and greater replication in the brains of neonatal mice. In addition, the passaged strain was more neurovirulent than the original strain, while both strains infected astroglial and neural progenitor cells in the mouse brain. Intracerebral inoculation of either the original or the passaged strain affected brain Purkinje cell dendrites, and a high titer of the passaged strain induced cerebellar hypoplasia in neonatal mice. Thus, infection by mouse-passaged SAFV affected cerebellar development in neonatal mice. This animal model contributes to the understanding of the neuropathogenicity of SAFV infections in infants. IMPORTANCE Saffold virus (SAFV) is a candidate neuropathogenic agent in infants and children, but the neuropathogenicity of the virus has not been fully elucidated. Recently, we evaluated the pathogenicity of two clinical SAFV isolates in mice. Similar to other neurotropic picornaviruses, these isolates showed mild infectivity of glial and neural progenitor cells, but not of large neurons, in the cerebellum. However, the outcome of this viral infection in the cerebellum has not been clarified. Here, we examined the tropism of SAFV in the cerebellum. We obtained an in vivo-passaged strain from the cerebella of neonatal mice and examined its genome and its neurovirulence in the neonatal mouse brain. The passaged virus showed high infectivity and neurovirulence in the brain, especially the cerebellum, and affected cerebellar development. This unique neonatal mouse model will be helpful for elucidating the neuropathogenesis of SAFV infections occurring early in life.

Structure and Genome Release Mechanism of the Human Cardiovirus Saffold Virus 3.

ABSTRACTIn order to initiate an infection, viruses need to deliver their genomes into cells. This involves uncoating the genome and transporting it to the cytoplasm. The process of genome delivery is not well understood for nonenveloped viruses. We address this gap in our current knowledge by studying the uncoating of the nonenveloped human cardiovirus Saffold virus 3 (SAFV-3) of the family Picornaviridae. SAFVs cause diseases ranging from gastrointestinal disorders to meningitis. We present a structure of a native SAFV-3 virion determined to 2.5 Å by X-ray crystallography and an 11-Å-resolution cryo-electron microscopy reconstruction of an “altered” particle that is primed for genome release. The altered particles are expanded relative to the native virus and contain pores in the capsid that might serve as channels for the release of VP4 subunits, N termini of VP1, and the RNA genome. Unlike in the related enteroviruses, pores in SAFV-3 are located roughly between the icosahedral 3- and 5-fold axes at an interface formed by two VP1 and one VP3 subunit. Furthermore, in native conditions many cardioviruses contain a disulfide bond formed by cysteines that are separated by just one residue. The disulfide bond is located in a surface loop of VP3. We determined the structure of the SAFV-3 virion in which the disulfide bonds are reduced. Disruption of the bond had minimal effect on the structure of the loop, but it increased the stability and decreased the infectivity of the virus. Therefore, compounds specifically disrupting or binding to the disulfide bond might limit SAFV infection.IMPORTANCE A capsid assembled from viral proteins protects the virus genome during transmission from one cell to another. However, when a virus enters a cell the virus genome has to be released from the capsid in order to initiate infection. This process is not well understood for nonenveloped viruses. We address this gap in our current knowledge by studying the genome release of Human Saffold virus 3. Saffold viruses cause diseases ranging from gastrointestinal disorders to meningitis. We show that before the genome is released, the Saffold virus 3 particle expands, and holes form in the previously compact capsid. These holes serve as channels for the release of the genome and small capsid proteins VP4 that in related enteroviruses facilitate subsequent transport of the virus genome into the cell cytoplasm.

Prevalence and clinical features of encephalomyocarditis virus infection in children with acute respiratory infection or digestive tract infection

Objective To investigate the possible existence of encephalomyocarditis virus (EMCV) in children with acute respiratory infection or digestive tract infection. Methods Nasopharyngeal aspirates from 577 children with acute respiratory infection and fecal samples from 384 children with digestive tract infection in Tianjin Children′s Hospital were collected from January 2013 to December 2013.Viral nucleic acid was extracted, and EMCV infection was determined by using real-time quantitative PCR.Positive PCR products were sequenced.The sequencing results were aligned with known gene sequences of EMCV sequences in GenBank.Other common respiratory tract or digestive tract viruses were also detected.Direct immunofluorescence was used to detect 7 common respiratory viruses; colloidal gold labeled method was used to detect rotavirus and adenovirus; enzyme linked immunosorbent assay was used to detect avastrovirus; PCR was used to detect human rhinovirus, WU polyomavirus, KI polyomavirus, human bocavirus, norovi-ruses, enteroviruses, Aichi virus and human parechovirus.Real-time PCR was used to detect saffold virus. Results Seven(1.2%) nasopharyngeal aspirates from children with acute respiratory infection were positive for EMCV.These children aged 1-6 months.The infection seasons were in autumn and winter.Eleven(2.9%) fecal samples from children with digestive tract infection were positive for EMCV.Positive specimens were in patients less than 1 year of age and 4-7 years of age.EMCV was identified in other 3 seasons except spring.The clinical diagnosis of the EMCV-po-sitive patients were fever or diarr-hea, which was similar with other respiratory tract or digestive tract viruses.There were 88.9% (16/18 cases) of these EMCV infected children lived in suburbs or countryside.There were a few co-infections with EMCV and other respiratory tract or digestive tract viruses.There was no obvious difference in the clinical symptoms between EMCV-positive patients with or without coinfection. Conclusions Infection of EMCV often occurs in children with acute respiratory infection or digestive tract infection in China.Some of acute respiratory infection or digestive tract infection in pediatric patients was related to EMCV. Key words: Encephalomyocarditis virus; Acute respiratory infection; Digestive tract infection; Child

Neurotropism of Saffold virus in a mouse model.

Saffold virus (SAFV) is a highly seroprevalent human Cardiovirus discovered recently. No clear association between SAFV infection and human disease has been established. Rare infection cases, however, correlated with neurological symptoms. To gain insight into the pathogenesis potential of the virus, we performed experimental mouse infection with SAFV strains of genotypes 2 and 3 (SAFV-2 and SAFV-3). After intraperitoneal infection, both strains exhibited a typical Cardiovirus tropism. Viral load was most prominent in the pancreas. Heart, spleen, brain and spinal cord were also infected. In IFN-receptor 1 deficient (IFNAR-KO) mice, SAFV-3 caused a severe encephalitis. The virus was detected by immunohistochemistry in many parts of the brain and spinal cord, both in neurons and astrocytes, but astrocyte infection was more extensive. In vitro, SAFV-3 also infected astrocytes better than neurons in mixed primary cultures. Astrocytes were, however, very efficiently protected by IFN-α/β treatment.

The Pathogenesis of Saffold Virus in AG129 Mice and the Effects of Its Truncated L Protein in the Central Nervous System.

Saffold Virus (SAFV) is a human cardiovirus that has been suggested to cause severe infection of the central nervous system (CNS). Compared to a similar virus, Theiler’s murine encephalomyelitis virus (TMEV), SAFV has a truncated Leader (L) protein, a protein essential in the establishment of persistent CNS infections. In this study, we generated a chimeric SAFV by replacing the L protein of SAFV with that of TMEV. We then compared the replication in cell cultures and pathogenesis in a mouse model. We showed that both SAFV and chimeric SAFV are able to infect Vero and Neuro2a cells well, but only chimeric SAFV was able to infect RAW264.7. We then showed that mice lacking IFN-α/β and IFN-γ receptors provide a good animal model for SAFV infection, and further identified the locality of the infection to the ventral horn of the spine and several locations in the brain. Lastly, we showed that neither SAFV nor chimeric SAFV causes persistence in this model. Overall, our results provide a strong basis on which the mechanisms underlying Saffold virus induced neuropathogenesis can be further studied and, hence, facilitating new information about its pathogenesis.

Neuropathogenicity of Two Saffold Virus Type 3 Isolates in Mouse Models.

ObjectiveSaffold virus (SAFV), a picornavirus, is occasionally detected in children with acute flaccid paralysis, meningitis, and cerebellitis; however, the neuropathogenicity of SAFV remains undetermined.MethodsThe virulence of two clinical isolates of SAFV type 3 (SAFV-3) obtained from a patient with aseptic meningitis (AM strain) and acute upper respiratory inflammation (UR strain) was analyzed in neonatal and young mice utilizing virological, pathological, and immunological methods.ResultsThe polyproteins of the strains differed in eight amino acids. Both clinical isolates were infective, exhibited neurotropism, and were mildly neurovirulent in neonatal ddY mice. Both strains pathologically infected neural progenitor cells and glial cells, but not large neurons, with the UR strain also infecting epithelial cells. UR infection resulted in longer inflammation in the brain and spinal cord because of demyelination, while the AM strain showed more infectivity in the cerebellum in neonatal ddY mice. Additionally, young BALB/c mice seroconverted following mucosal inoculation with the UR, but not the AM, strain.ConclusionsBoth SAFV-3 isolates had neurotropism and mild neurovirulence but showed different cell tropisms in both neonatal and young mouse models. This animal model has the potential to recapitulate the potential neuropathogenicity of SAFV-3.