EV-D68 virus-like particle vaccines elicit cross-clade neutralizing antibodies that inhibit infection and block dissemination

Emerging and re-emerging viral infections of the central nervous system in Australasia and beyond

Viral infections of the central nervous system (CNS) have been emerging and re-emerging worldwide, and the Australasia region has not been spared. Enterovirus A71 and enterovirus D68, both human enteroviruses, are likely to replace the soon-to-be eradicated poliovirus to cause global outbreaks associated with neurological disease. Although prevalent elsewhere, the newly emergent orthoflavivirus, Japanese encephalitis virus (genotype IV), caused human infections in Australia in 2021, and almost certainly will continue to do so because of spillovers from the natural animal host-vector life cycle endemic in the country. Another orthoflavivirus, Murray Valley encephalitis virus, has re-emerged in Australia. The Hendra henipavirus together with Nipah henipavirus ​are listed as high-risk pathogens by the World Health Organization because both can cause lethal encephalitis. The former remains a health threat in Australasia because bats may still be able to spread the infection to unvaccinated Australian horses and other animals acting as intermediate hosts, and thence to humans. The global COVID-19 pandemic, caused by the emerging severe acute respiratory syndrome coronavirus-2, a virus transmitted from animals to humans that was first described and first arose in China, is associated with acute and long-lasting CNS pathology. Fortunately, the pathology and pathogenesis of these important neurotropic viruses are now better understood, leading to better management protocols and prevention strategies. Pathologists are in a unique position to contribute to the diagnosis and advancement in our knowledge of infectious diseases. This review summarises some of the current knowledge about a few important emerging and re-emerging CNS infections in Australasia and beyond.

Enterovirus D68 infection in cotton rats results in systemic inflammation with detectable viremia associated with extracellular vesicle and neurologic disease

Enterovirus D68 (EV-D68) is a non-polio enterovirus that causes respiratory illness and is linked to acute flaccid myelitis (AFM) in infants and children. Recent demonstration of association of EV-D68 with extracellular vesicles (EVs) released from infected cells in vitro suggests a role for these vesicles in non-lytic dissemination of virus beyond the respiratory tract. We previously reported the permissiveness of cotton rat (Sigmodon hispidus) to infection with different EV-D68 strains of clades A and B, but did not investigate the virus association with EVs. We present a model of acute respiratory infection with a clinical isolate of EV-D68 of clade B3 in immunocompetent cotton rats featuring systemic dissemination of the virus. EV-D68 was detected in circulation and organs outside of the respiratory tract with the inflammatory response accompanying dissemination. Further analysis demonstrated that the virus was associated with extracellular vesicles purified from plasma. We also present a model of intraperitoneal infection with EV-D68 in young cotton rats featuring dissemination of the virus to spinal cord and brain with associated clinical signs of neurologic disease. EV-D68-associated with EVs produced in cotton rat cells and injected intraperitoneally into young cotton rats also resulted in detection of virus in the CNS. Our results provide the first in vivo experimental support for the notion that respiratory infection with EV-D68 generates virus associated with extracellular vesicles that disseminate outside the respiratory tract. These models of infection could be used to investigate the role of EVs-associated EV-D68 in the pathogenesis of EV-D68 infection and to assess therapeutic interventions.

Insights Into Enterovirus D68 Immunology: Unraveling the Mysteries of Host-Pathogen Interactions

BACKGROUND

Enterovirus D68 (EV-D68) has emerged as a significant respiratory and neurological pathogen, particularly affecting children with severe respiratory illnesses and acute flaccid myelitis. Understanding the interaction between EV-D68 and the host immune system is crucial for developing effective prevention and treatment strategies.

OBJECTIVES

This review aims to examine the immune response to EV-D68, its mechanisms of immune evasion, and the current progress in vaccine and antiviral development while identifying gaps in knowledge and future research directions.

METHODS

A comprehensive review of the literature was conducted, focusing on the innate and adaptive immune responses to EV-D68, its strategies for immune evasion, and advancements in therapeutic interventions.

RESULTS

Pattern recognition receptors detect EV-D68 and trigger antiviral defenses, including interferon production and activation of natural killer cells. B cells generate antibodies, while T cells coordinate a targeted response to the virus. EV-D68 employs mechanisms such as antigenic variation and disruption of host antiviral pathways to evade immune detection. Progress in vaccine and antiviral research shows promise but remains in the early stages.

CONCLUSIONS

EV-D68 represents a complex and evolving public health challenge. Although the immune system mounts a robust response, the virus's ability to evade these defenses complicates efforts to control it. Continued research is essential to develop effective vaccines and antivirals and to address gaps in understanding its pathogenesis and immune interactions.

IMPLICATIONS

A multidisciplinary approach is critical to improving diagnostic, preventive, and therapeutic strategies for EV-D68, ensuring better preparedness for future outbreaks.

Global age-stratified seroprevalence of enterovirus D68: a systematic literature review

Enterovirus D68 (EV-D68), first isolated in 1962, emerged in 2014, causing outbreaks of severe respiratory infections and acute flaccid myelitis. In this systematic review, we have compiled all available literature on age-stratified seroprevalence estimates of EV-D68. Ten studies from six countries were retained, all conducted using microneutralisation assays, despite wide variations in protocols and challenge viruses. The age profiles of seroprevalence were similar across time and regions; seroprevalence increased quickly with age, reaching roughly 100% by the age of 20 years and with no sign of decline throughout adulthood. This suggests continuous or frequent exposure of the populations to the virus, or possible cross-reactivity with other viruses. Studies with two or more cross-sectional surveys reported consistently higher seroprevalence at later timepoints, suggesting a global increase in transmission over time. This systematic review concludes that standardising serological protocols, understanding the contribution of cross-reactivity with other pathogens to the high reported seroprevalence, and quantifying individual exposure to EV-D68 over time are the main research priorities for the future.

Some assembly required: a single-RNA vaccine against enterovirus-D68

A single-RNA-based vaccine against enterovirus-D68, a respiratory virus and causative agent of severe paralytic disease in children, by the Erasmus group shows great promise in generating broadly cross-neutralizing antibodies in mice and macaque models of infection.

A self-amplifying RNA vaccine prevents enterovirus D68 infection and disease in preclinical models

The recent emergence and rapid response to severe acute respiratory syndrome coronavirus 2 was enabled by prototype pathogen and vaccine platform approaches, driven by the preemptive application of RNA vaccine technology to the related Middle East respiratory syndrome coronavirus. Recently, the National Institutes of Allergy and Infectious Diseases identified nine virus families of concern, eight enveloped virus families and one nonenveloped virus family, for which vaccine generation is a priority. Although RNA vaccines have been described for a variety of enveloped viruses, a roadmap for their use against nonenveloped viruses is lacking. Enterovirus D68 was recently designated a prototype pathogen within the family Picornaviridae of nonenveloped viruses because of its rapid evolution and respiratory route of transmission, coupled with a lack of diverse anti-enterovirus vaccine approaches in development. Here, we describe a proof-of-concept approach using a clinical stage RNA vaccine platform that induced robust enterovirus D68-neutralizing antibody responses in mice and nonhuman primates and prevented upper and lower respiratory tract infections and neurological disease in mice. In addition, we used our platform to rapidly characterize the antigenic diversity within the six genotypes of enterovirus D68, providing the necessary data to inform multivalent vaccine compositions that can elicit optimal breadth of neutralizing responses. These results demonstrate that RNA vaccines can be used as tools in our pandemic-preparedness toolbox for nonenveloped viruses.

Enteroviruses: epidemic potential, challenges and opportunities with vaccines

Enteroviruses (EVs) are the most prevalent viruses in humans. EVs can cause a range of acute symptoms, from mild common colds to severe systemic infections such as meningitis, myocarditis, and flaccid paralysis. They can also lead to chronic diseases such as cardiomyopathy. Although more than 280 human EV serotypes exist, only four serotypes have licenced vaccines. No antiviral drugs are available to treat EV infections, and global surveillance of EVs has not been effectively coordinated. Therefore, poliovirus still circulates, and there have been alarming epidemics of non-polio enteroviruses. Thus, there is a pressing need for coordinated preparedness efforts against EVs.This review provides a perspective on recent enterovirus outbreaks and global poliovirus eradication efforts with continuous vaccine development initiatives. It also provides insights into the challenges and opportunities in EV vaccine development. Given that traditional whole-virus vaccine technologies are not suitable for many clinically relevant EVs and considering the ongoing risk of enterovirus outbreaks and the potential for new emerging pathogenic strains, the need for new effective and adaptable enterovirus vaccines is emphasized.This review also explores the difficulties in translating promising vaccine candidates for clinical use and summarizes information from published literature and clinical trial databases focusing on existing enterovirus vaccines, ongoing clinical trials, the obstacles faced in vaccine development as well as the emergence of new vaccine technologies. Overall, this review contributes to the understanding of enterovirus vaccines, their role in public health, and their significance as a tool for future preparedness.

Doxycycline inhibits neurotropic enterovirus proliferation in vitro

Human enteroviruses (EVs) represent a global public health concern due to their association with a range of serious pediatric illnesses. Despite the high morbidity and mortality exerted by EVs, no broad-spectrum antivirals are currently available. Herein, we presented evidence that doxycycline can inhibit in vitro replication of various neurotropic EVs, including enterovirus A71 (EV-A71), enterovirus D68 (EV-D68), and coxsackievirus (CV)-A6, in a dose-dependent manner. Further investigations indicated that the drug primarily acted at the post-entry stage of virus infection in vitro, with inhibitory effects reaching up to 89 % for EV-A71 when administered two hours post-infection. These findings provide valuable insights for the development of antiviral drugs against EV infections.

Enterovirus virus-like-particle and inactivated poliovirus vaccines do not elicit substantive cross-reactive antibody responses

Human enteroviruses are the most common human pathogen with over 300 distinct genotypes. Previous work with poliovirus has suggested that it is possible to generate antibody responses in humans and animals that can recognize members of multiple enterovirus species. However, cross protective immunity across multiple enteroviruses is not observed epidemiologically in humans. Here we investigated whether immunization of mice or baboons with inactivated poliovirus or enterovirus virus-like-particles (VLPs) vaccines generates antibody responses that can recognize enterovirus D68 or A71. We found that mice only generated antibodies specific for the antigen they were immunized with, and repeated immunization failed to generate cross-reactive antibody responses as measured by both ELISA and neutralization assay. Immunization of baboons with IPV failed to generate neutralizing antibody responses against enterovirus D68 or A71. These results suggest that a multivalent approach to enterovirus vaccination is necessary to protect against enterovirus disease in vulnerable populations.

Nanotechnology's frontier in combatting infectious and inflammatory diseases: prevention and treatment

Inflammation-associated diseases encompass a range of infectious diseases and non-infectious inflammatory diseases, which continuously pose one of the most serious threats to human health, attributed to factors such as the emergence of new pathogens, increasing drug resistance, changes in living environments and lifestyles, and the aging population. Despite rapid advancements in mechanistic research and drug development for these diseases, current treatments often have limited efficacy and notable side effects, necessitating the development of more effective and targeted anti-inflammatory therapies. In recent years, the rapid development of nanotechnology has provided crucial technological support for the prevention, treatment, and detection of inflammation-associated diseases. Various types of nanoparticles (NPs) play significant roles, serving as vaccine vehicles to enhance immunogenicity and as drug carriers to improve targeting and bioavailability. NPs can also directly combat pathogens and inflammation. In addition, nanotechnology has facilitated the development of biosensors for pathogen detection and imaging techniques for inflammatory diseases. This review categorizes and characterizes different types of NPs, summarizes their applications in the prevention, treatment, and detection of infectious and inflammatory diseases. It also discusses the challenges associated with clinical translation in this field and explores the latest developments and prospects. In conclusion, nanotechnology opens up new possibilities for the comprehensive management of infectious and inflammatory diseases.

Enterovirus-D68 - A Reemerging Non-Polio Enterovirus that Causes Severe Respiratory and Neurological Disease in Children

The past decade has seen the global reemergence and rapid spread of enterovirus D68 (EV-D68), a respiratory pathogen that causes severe respiratory illness and paralysis in children. EV-D68 was first isolated in 1962 from children with pneumonia. Sporadic cases and small outbreaks have been reported since then with a major respiratory disease outbreak in 2014 associated with an increased number of children diagnosed with polio-like paralysis. From 2014-2018, major outbreaks have been reported every other year in a biennial pattern with > 90% of the cases occurring in children under the age of 16. With the outbreak of SARS-CoV-2 and the subsequent COVID-19 pandemic, there was a significant decrease in the prevalence EV-D68 cases along with other respiratory diseases. However, since the relaxation of pandemic social distancing protocols and masking mandates the number of EV-D68 cases have begun to rise again - culminating in another outbreak in 2022. Here we review the virology, pathogenesis, and the immune response to EV-D68, and discuss the epidemiology of EV-D68 infections and the divergence of contemporary strains from historical strains. Finally, we highlight some of the key challenges in the field that remain to be addressed.

Clinical and molecular epidemiology of enterovirus D68 from 2013 to 2020 in Shanghai

Enterovirus D68 (EV-D68) is an emerging pathogen that has caused outbreaks of severe respiratory disease worldwide, especially in children. We aim to investigate the prevalence and genetic characteristics of EV-D68 in children from Shanghai. Nasopharyngeal swab or bronchoalveolar lavage fluid samples collected from children hospitalized with community-acquired pneumonia were screened for EV-D68. Nine of 3997 samples were EV-D68-positive. Seven of nine positive samples were sequenced and submitted to GenBank. Based on partial polyprotein gene (3D) or complete sequence analysis, we found the seven strains belong to different clades and subclades, including three D1 (detected in 2013 and 2014), one D2 (2013), one D3 (2019), and two B3 (2014 and 2018). Overall, we show different clades and subclades of EV-D68 spread with low positive rates (0.2%) among children in Shanghai between 2013 and 2020. Amino acid mutations were found in the epitopes of the VP1 BC and DE loops and C-terminus; similarity analysis provided evidence for recombination as an important mechanism of genomic diversification. Both single nucleotide mutations and recombination play a role in evolution of EV-D68. Genetic instability within these clinical strains may indicate large outbreaks could occur following cumulative mutations.