Current status of enterovirus D68 worldwide and in Taiwan

VP1 is the primary determinant of neuropathogenesis in a mouse model of enterovirus D68 acute flaccid myelitis

Enterovirus D68 (EV-D68) is an emerging pathogen that can cause severe respiratory and neurologic disease [acute flaccid myelitis (AFM)]. Intramuscular (IM) injection of neonatal Swiss Webster (SW) mice with US/IL/14-18952 (IL52), a clinical isolate from the 2014 EV-D68 epidemic, results in many of the pathogenic features of human AFM, including viral infection of the spinal cord, death of motor neurons, and resultant progressive paralysis. In distinction, CA/14-4231 (CA4231), another clinical isolate from the 2014 EV-D68 outbreak, does not cause paralysis in mice, does not grow in the spinal cord, and does not cause motor neuron loss following IM injection. A panel of chimeric viruses containing sequences from IL52 and CA4231 was used to demonstrate that VP1 is the main determinant of EV-D68 neurovirulence following IM injection of neonatal SW mice. VP1 contains four amino acid differences between IL52 and CA4231. Mutations resulting in substituting these four amino acids (CA4231 residues into the IL52 polyprotein) completely abolished neurovirulence. Conversely, mutations resulting in substituting VP1 IL52 amino acid residues into the CA4231 polyprotein created a virus that induced paralysis to the same degree as IL52. Neurovirulence following infection of neonatal SW mice with parental and chimeric viruses was associated with viral growth in the spinal cord.

IMPORTANCE

Emerging viruses allow us to investigate mutations leading to increased disease severity. Enterovirus D68 (EV-D68), once the cause of rare cases of respiratory illness, recently acquired the ability to cause severe respiratory and neurologic disease. Chimeric viruses were used to demonstrate that viral structural protein VP1 determines growth in the spinal cord, motor neuron loss, and paralysis following intramuscular (IM) injection of neonatal Swiss Webster (SW) mice with EV-D68. These results have relevance for predicting the clinical outcome of future EV-D68 epidemics as well as targeting retrograde transport as a potential strategy for treating virus-induced neurologic disease.

Investigation of the Correlation between Enterovirus Infection and the Climate Factor Complex Including the Ping-Year Factor and El Niño-Southern Oscillation in Taiwan

Enterovirus infection and enterovirus infection with severe complications (EVSC) are critical issues in several aspects. However, there is no suitable predictive tool for these infections. A climate factor complex (CFC) containing several climate factors could provide more effective predictions. The ping-year factor (PYF) and El Niño-Southern Oscillation (ENSO) are possible CFCs. This study aimed to determine the relationship between these two CFCs and the incidence of enterovirus infection. Children aged 15 years and younger with enterovirus infection and/or EVSC were enrolled between 2007 and 2022. Each year was categorized into a ping-year or non-ping-year according to the PYF. Poisson regression was used to evaluate the associations between the PYF, ENSO, and the incidence of enterovirus infection. Compared to the ping-year group, the incidence rate of enterovirus infection, the incidence rate of EVSC, and the ratio of EVSC in the non-ping-year group were 1.24, 3.38, and 2.73 times higher, respectively (p < 0.001). For every one-unit increase in La Niña, the incidence rate of enterovirus infection decreased to 0.96 times (p < 0.001). Our study indicated that CFCs could be potential predictors for enterovirus infection, and the PYF was more suitable than ENSO. Further research is needed to improve the predictive model.

Off-season circulation and characterization of enterovirus D68 with respiratory and neurological presentation using whole-genome sequencing

To explore an off-season enterovirus D68 (EV-D68) upsurge in the winter season of 2019/2020, we adapted a whole-genome sequencing approach for Nanopore Sequencing for 20 hospitalized patients with accompanying respiratory or neurological presentation. Applying phylodynamic and evolutionary analysis on Nextstrain and Datamonkey respectively, we report a highly diverse virus with an evolutionary rate of 3.05 × 10^-3 substitutions per year (entire EV-D68 genome) and a positive episodic/diversifying selection with persistent yet undetected circulation likely driving evolution. While the predominant B3 subclade was identified in 19 patients, one A2 subclade was identified in an infant presenting with meningitis. Exploring single nucleotide variations using CLC Genomics Server showed high levels of non-synonymous mutations, particularly in the surface proteins, possibly highlighting growing problems with routine Sanger sequencing for typing enteroviruses. Surveillance and molecular approaches to enhance current knowledge of infectious pathogens capable of pandemic potential are paramount to early warning in health care facilities.

Etiologies of outpatient medically attended acute respiratory infections among young Ecuadorian children prior to the start of the 2020 SARS-CoV-2 pandemic

BACKGROUND

Implementation of respiratory virus prevention measures requires detailed understanding of regional epidemiology; however, data from many tropical countries are sparse. We describe etiologies of ambulatory pediatric acute respiratory tract infections (ARTI) in Ecuador immediately preceding the onset of the SARS-CoV-2 pandemic.

METHODS

Children < 5 years presenting to a designated study site with an ARTI were eligible. Informed consent was obtained. Demographic and clinical data were recorded. A nasopharyngeal swab was collected, processed, and analyzed using multiplex polymerase chain reaction (PCR) for common respiratory pathogens. Rhinovirus/enterovirus positive samples were further characterized by genomic sequencing.

RESULTS

A total of 820 subjects were enrolled in the study between July 2018 and March 2020. A total of 655 (80%) samples identified at least one pathogen. Rhinoviruses (44%) were most common, followed by enteroviruses (17%), parainfluenza viruses (17%), respiratory syncytial virus (RSV) (15%), and influenza viruses (13%). Enterovirus D68 was the most common enterovirus detected and was among the leading causes of bronchiolitis. Seasonal RSV and influenza virus activity were different along the coast compared with the highlands.

CONCLUSIONS

Ongoing regional surveillance studies are necessary to optimize available and emerging pathogen-specific preventative measures.

Seroepidemiology of enterovirus D68 infection in Kuala Lumpur, Malaysia between 2013 and 2015

Enterovirus D68 (EV-D68) is an emerging respiratory pathogen since the 2014 outbreak in the United States. A low level of virus circulation has been reported in Kuala Lumpur, Malaysia, in the past. However, the extent of the infection in Malaysia is not known. In the present study, we determine the seroepidemiology of EV-D68 in Kuala Lumpur, Malaysia, before and after the United States outbreak in August 2014. A luciferase-based seroneutralization test was developed using a clone-derived prototype Fermon strain carrying a nanoluciferase marker. We screened the neutralization capacity of 450 serum samples from children and adults (1-89 years old) collected between 2013 and 2015. EV-D68 seropositivity increased with age, with children aged 1-3 showing significantly lower seroprevalence compared to adults. Multivariate analysis showed that older age groups 13-49 years (odds ratio [OR] = 4.78; 95% confidence interval [CI] = 2.69-8.49; p < 0.0001) and ≥50 years (OR = 3.83; 95% CI = 2.19-6.68; p < 0.0001) were more likely to be EV-D68 seropositive than children <13 years. Sampling post-September 2014 compared to pre-Sept 2014 also predicted seropositivity (OR = 1.66; 95% CI = 1.04-2.65). The presence of neutralizing antibodies against EV-D68 in the study population suggests that EV-D68 was circulating before 2014. A higher seropositivity post-September 2014 suggests that Malaysia also experienced an upsurge in EV-D68 infections after the United States outbreaks in August 2014. A low seropositivity rate observed in children, especially those aged 1-3 years old, suggests that they are at risk and should be prioritized for future vaccination.

Enterovirus D68 Subclade B3 in Children with Acute Flaccid Paralysis in West Africa, 2016

We tested for enterovirus D68 in fecal samples collected during June-September 2016 from 567 patients with acute flaccid paralysis in 7 West Africa nations. Children <5 years old comprised 64.3% of enterovirus D68 positive patients. Our findings emphasize the need for active surveillance for acute flaccid myelitis.

Mapping Attenuation Determinants in Enterovirus-D68

Enterovirus (EV)-D68 has been associated with epidemics in the United Sates in 2014, 2016 and 2018. This study aims to identify potential viral virulence determinants. We found that neonatal type I interferon receptor knockout mice are susceptible to EV-D68 infection via intraperitoneal inoculation and were able to recapitulate the paralysis process observed in human disease. Among the EV-D68 strains tested, strain US/MO-14-18949 caused no observable disease in this mouse model, whereas the other strains caused paralysis and death. Sequence analysis revealed several conserved genetic changes among these virus strains: nucleotide positions 107 and 648 in the 5′-untranslated region (UTR); amino acid position 88 in VP3; 1, 148, 282 and 283 in VP1; 22 in 2A; 47 in 3A. A series of chimeric and point-mutated infectious clones were constructed to identify viral elements responsible for the distinct virulence. A single amino acid change from isoleucine to valine at position 88 in VP3 attenuated neurovirulence by reducing virus replication in the brain and spinal cord of infected mice.