A comparative study of multiple clinical enterovirus 71 isolates and evaluation of cross protection of inactivated vaccine strain FY-23 K-B in vitro

The Milk of Cows Immunized with Trivalent Inactivated Vaccines Provides Broad-Spectrum Passive Protection against Hand, Foot, and Mouth Disease in Neonatal Mice

Hand, foot, and mouth disease (HFMD) is a contagious viral infection predominantly affecting infants and young children, caused by multiple enteroviruses, including Enterovirus 71 (EV71), Coxsackievirus A16 (CA16), Coxsackievirus A10 (CA10), and Coxsackievirus A6 (CA6). The high pathogenicity of HFMD has garnered significant attention. Currently, there is no specific treatment or broad-spectrum preventive measure available for HFMD, and existing monovalent vaccines have limited impact on the overall incidence or prevalence of the disease. Consequently, with the emergence of new viral strains driven by vaccine pressure, there is an urgent need to develop strategies for the rapid response and control of new outbreaks. In this study, we demonstrated the broad protective effect of maternal antibodies against three types of HFMD by immunizing mother mice with a trivalent inactivated vaccine targeting EV71, CA16, and CA10, using a neonatal mouse challenge model. Based on the feasibility of maternal antibodies as a form of passive immunization to prevent HFMD, we prepared a multivalent antiviral milk by immunizing dairy cows with the trivalent inactivated vaccine to target multiple HFMD viruses. In the neonatal mouse challenge model, this immunized milk exhibited extensive passive protection against oral infections caused by the three HFMD viruses. Compared to vaccines, this strategy may offer a rapid and broadly applicable approach to providing passive immunity for the prevention of HFMD, particularly in response to the swift emergence and spread of new variants.

Immune responses of a CV-A16 live attenuated candidate strain and its protective effects in rhesus monkeys

Coxsackievirus A16 (CV-A16) is a major causative pathogen of hand, foot, and mouth diseases (HFMDs). The licensed HFMD vaccine targets EV-A71 without cross-protection against CV-A16. Thus, a CV-A16 vaccine is needed. In this study, the immunogenicity and protective efficacy of a live attenuated CV-A16 candidate, K168-8Ac, were evaluated in a rhesus monkey model. Four passages of this strain (P35, P50, P60, and P70) were administered to monkeys, and its protective effect was identified. The immunized monkeys were clinically asymptomatic, except for slight fever. Weak viraemia was observed, and two doses of vaccination were found to significantly reduce virus shedding. High levels of antibody responses were observed (1:1024–1:2048), along with a significant increase in plasma IL-8. The I.M. group showed a much stronger humoural immunity. Pathological damage was detected mainly in lung tissues, although thalamus, spinal cord, lymph nodes, and livers were involved. After the viral challenge, it was found that two doses of vaccine reduced virus shedding, and the degree of lung damage and the number of organs involved decreased as the passage number increased. Overall, a robust immune response and partial protection against CV-A16, triggered by the K168-8Ac strain, were demonstrated. This study provides valuable data for CV-A16 vaccine development.

Enterovirus-A71 exploits peripherin and Rac1 to invade the central nervous system

Enterovirus-A71 (EV-A71) has been associated with severe neurological forms of hand, foot, and mouth disease (HFMD). EV-A71 infects motor neurons at neuromuscular junctions (NMJs) to invade the central nervous system (CNS). Here, we investigate the role of peripherin (PRPH) during EV-A71 infection, a type III intermediate neurofilament involved in neurodegenerative conditions. In mice infected with EV-A71, PRPH co-localizes with viral particles in the muscles at NMJs and in the spinal cord. In motor neuron-like and neuroblastoma cell lines, surface-expressed PRPH facilitates viral entry, while intracellular PRPH influences viral genome replication through interactions with structural and non-structural viral components. Importantly, PRPH does not play a role during infection with coxsackievirus A16, another causative agent of HFMD rarely associated with neurological complications, suggesting that EV-A71 ability to exploit PRPH represents a unique attribute for successful CNS invasion. Finally, we show that EV-A71 also exploits some of the many PRPH-interacting partners. Of these, small GTP-binding protein Rac1 represents a potential druggable host target to limit neuroinvasion of EV-A71.

Assessing the vaccine effectiveness for hand, foot, and mouth disease in Guangzhou, China: a time-series analysis

Objective: Hand, foot, and mouth disease (HFMD) is an important public health issue in China. Although efficacy has been demonstrated by randomized controlled trials, the evidence for effectiveness of the monovalent Enterovirus 71 (EV71) vaccine against HFMD remains unknown. This study aimed to assess the vaccine effectiveness for HFMD in Guangzhou, China. Methods: Routinely collected vaccination and HFMD surveillance data were captured from the China Information System for Disease Control and Prevention. We estimated the EV71 vaccine effectiveness using spatial ecologic and time-series analysis approaches. Results: A total of 174,002 HFMD cases under 5 years of age were reported to the Guangzhou, China surveillance system from January 2016 to December 2018. A total of 408,664 children completed a two-dose EV71 vaccination series. In an ecologic analysis, a two-dose EV71 vaccination rate above the median conferred lower HFMD risk relative to a vaccination rate below the median (ratio ratio = 0.955, 95% confidence interval (CI): 0.949, 0.962; P < .001). In the time-series approach, 0.9% fewer HFMD cases were associated with a 1% increase in the two-dose EV71 vaccination rate, but without statistical significance (P = .094). However, we detected statistically significant protective associations for HFMD among children 3 years of age (0.9% fewer HFMD cases with a 1% increased vaccination rate; P = .046), and for EV71 (1.4%; P = .012) and "other viruses" (1.3%; P = .002), although not for Coxsackievirus A16 (CVA16). Conclusion: Our findings, based on real-world data, provide evidence of EV71 vaccine effectiveness for preventing EV71 and "other" viruses associated with HFMD. An expanded program of EV71 vaccination is urgently needed.

Safety and immunogenicity of an experimental live combination vaccine against enterovirus 71 and coxsackievirus A16 in rhesus monkeys

Enterovirus 71 (EV-A71) and Coxsackievirus A16 (CV-A16) are the two most common pathogens causing hand, foot, and mouth disease (HFMD). Previously, we obtained one candidate live attenuated strain each for EV-A71 and CV-A16; here, we evaluated the safety and immunogenicity of a combinedlive vaccine against EV-A71 and CV-A16 generated from these two candidate strains. Rhesus monkeys were intramuscularly treated with a live combinationvaccine against both EV-A71 and CV-A16 or with either vaccine alone. No fever or atypical clinical signs were observed in any animals. Monkeys vaccinated with the combinationlive vaccine presented no notable pathological changes in the brain, spinal cord, lung, and liver; in contrast, these regions showed inflammatory cell infiltration in monkeys treated with EV-A71 alone or CV-A16 alone. Weak viremia was detected in plasma after inoculation with the combinationvaccine; however, the duration of viral shedding in feces was increased. Biochemical studies revealed a slight increase in aspartate aminotransferase levels in monkeys inoculated with the live combination vaccine; however, histopathological findings did not attribute this change to liver damage. We also found that the live combinationvaccine induced a dual humoral immune response. Cytokine analysis indicated that the combined EV-A71/CV-A16 vaccine significantly down-regulated interleukin-8 production. Here, we have demonstrated that the live attenuated EV-A71/CV-A16 vaccine was safe and could trigger a dual specific immune response. However, its immune protection efficacy requires further investigation.

Newly emerged enterovirus-A71 C4 sublineage may be more virulent than B5 in the 2015-2016 hand-foot-and-mouth disease outbreak in northern Vietnam

Enterovirus-A71 (EV-A71) is a common cause of hand-foot-and-mouth disease (HFMD) and, rarely, causes severe neurological disease. This study aimed to elucidate the epidemiological and genetic characteristics and virulence of EV-A71 strains isolated from children diagnosed with HFMD. Rectal and throat swabs were collected from 488 children with HFMD in Hanoi, Vietnam, in 2015-2016. From 391 EV-positive patients, 15 EVs, including coxsackievirus A6 (CV-A6; 47.1%) and EV-A71 (32.5%, n = 127), were identified. Of the 127 EV-A71 strains, 117 (92.1%) were the B5 subgenotype and 10 (7.9%) were the C4 subgenotype. A whole-genome analysis of EV-A71 strains showed that seven of the eight C4a strains isolated in 2016 formed a new lineage, including two possible recombinants between EV-A71 C4 and CV-A8. The proportion of inpatients among C4-infected children was higher than among B5-infected children (80.0% vs. 27.4%; P = 0.002). The virulence of EV-A71 strains was examined in human scavenger receptor class B2 (hSCARB2)-transgenic mice, and EV-A71 C4 strains exhibited higher mortality than B5 strains (80.0% vs. 30.0%, P = 0.0001). Thus, a new EV-A71 C4a-lineage, including two possible recombinants between EV-A71 C4 and CV-A8, appeared in 2016 in Vietnam. The EV-A71 C4 subgenotype may be more virulent than the B5 subgenotype.

Glutathione facilitates enterovirus assembly by binding at a druggable pocket

Enteroviruses cause a range of human and animal diseases, some life-threatening, but there remain no licenced anti-enterovirus drugs. However, a benzene-sulfonamide derivative and related compounds have been shown recently to block infection of a range of enteroviruses by binding the capsid at a positively-charged surface depression conserved across many enteroviruses. It has also been established that glutathione is essential for the assembly of many enteroviruses, interacting with the capsid proteins to facilitate the formation of the pentameric assembly intermediate, although the mechanism is unknown. Here we show, by high resolution structure analyses of enterovirus F3, that reduced glutathione binds to the same interprotomer pocket as the benzene-sulfonamide derivative. Bound glutathione makes strong interactions with adjacent protomers, thereby explaining the underlying biological role of this druggable binding pocket and delineating the pharmacophore for potential antivirals.

Enterovirus 71 infection of human airway organoids reveals VP1-145 as a viral infectivity determinant

Human enteroviruses frequently cause severe diseases in children. Human enteroviruses are transmitted via the fecal-oral route and respiratory droplets, and primary replication occurs in the gastro-intestinal and respiratory tracts; however, how enteroviruses infect these sites is largely unknown. Human intestinal organoids have recently proven to be valuable tools for studying enterovirus-host interactions in the intestinal tract. In this study, we demonstrated the susceptibility of a newly developed human airway organoid model for enterovirus 71 (EV71) infection. We showed for the first time in a human physiological model that EV71 replication kinetics are strain-dependent. A glutamine at position 145 of the VP1 capsid protein was identified as a key determinant of infectivity, and residues VP1-98K and VP1-104D were identified as potential infectivity markers. The results from this study provide new insights into EV71 infectivity in the human airway epithelia and demonstrate the value of organoid technology for virus research.