Pathologic and immunologic characteristics of coxsackievirus A16 infection in rhesus macaques.

Coxsackievirus A16 (CV-A16) causes human hand, foot and mouth disease, but its pathogenesis is unclear. In rhesus macaques, CV-A16 infection causes characteristic vesicles in the oral mucosa and limbs as well as viremia and positive viral loads in the tissues, suggesting that these animals reflect the pathologic process of the infection. An immunologic analysis indicated a defective immune response, which included undetectable neutralizing antibodies and IFN-γ-specific memory T-cells in macaques infected with CV-A16. Furthermore, existing neutralizing antibodies in macaques immunized with the inactivated vaccine were surprisingly unable to protect against a viral challenge despite the presence of a positive T-cell memory response against viral antigens. The virus was capable of infecting pre-conventional dendritic cells and replicating within them, which may correlate with the immunological characteristics observed in the animals.

The Structure, Pathogenicity and Immunogenicity of Two Virion Fractions Harvested from Cell Cultures Infected with the CA16 Virus.

OBJECTIVES: To investigate the biological characteristics of the two types of virion fractions of Coxsackievirus A 16 (CA16), which include the real virion fraction and pseudo-virion fraction in their structure, pathogenicity and immunogenicity. METHODS: We obtained the two CA16 virion fractions by density gradient centrifugation. The morphology of virion fractions was analyzed by electron microscopy, while the antigenic characteristics and immunogenicity of two virion fractions were determined by ELISA, SDS-PAGE, Western blot, qRT-PCR, and the mouse model of immune response. RESULTS: The two virion fractions contained the major viral antigen components in their structures, showed similar pathogenicity in a neonatal murine model and were capable of inducing an effective primary immune response in adult mice, regardless of the essential distinction between the two virion fractions, which was the cleavage of VP0 to VP2 and VP4. CONCLUSIONS: The two CA16 virion fractions showed antigenicity and immunogenicity with inducing a specific immune response in animals.

Immunity and clinical efficacy of an inactivated enterovirus 71 vaccine in healthy Chinese children: a report of further observations.

BACKGROUND: To investigate the long-term effects on immunity of an inactivated enterovirus 71 (EV71) vaccine and its protective efficacy. METHODS: A sub-cohort of 1,100 volunteers from Guangxi Province in China was eligible for enrolment and randomly administered either the EV71 vaccine or a placebo on days 0 and 28 in a phase III clinical trial and then observed for the following 2 years with approval by an independent ethics committee of Guangxi Zhuang Autonomous Region, China. Serum samples from the 350 participants who provided a full series of blood samples (at all the sampling points) within the 2-year period were collected. Vaccine-induced immune effects, including the neutralizing antibody titres and cross-protection against different genotypes of EV71, were examined. This study also evaluated the protective efficacy of this vaccine based upon clinical diagnosis. RESULTS: This sub-cohort showed a >60% drop-out rate over 2 years. The seroconversion rates among the 161 immunized subjects remained >95% at the end of study. The geometric mean titres of neutralizing antibodies (anti-genotype C4) 360 days after vaccination in 350 subjects were 81.0 (subjects aged 6-11 months), 98.4 (12-23 months), 95.0 (24-35 months), and 81.8 (36-71 months). These titres subsequently increased to 423.1, 659.0, 545.0, and 321.9, respectively, at 540 days post-immunization (d.p.i.), and similar levels were maintained at 720 d.p.i. Higher IFN-γ/IL-4-specific responses to the C4 genotype of EV71 and cross-neutralization reactivity against major EV71 genotype strains were observed in the vaccine group compared to those in the placebo group. Five EV71-infected subjects were observed in the placebo-treated control group and none in the vaccine-immunized group in per-protocol analysis. CONCLUSION: These results are consistent with the induction of dynamic immune responses and protective efficacy of the vaccine against most circulating EV71 strains. TRIAL REGISTRATION NUMBER: Clinicaltrials.gov, NCT01569581, Trial registration date: March 2012.

[Heat effect stability of inactivated enterovirus 71 vaccine].

OBJECTIVE: To investigate the effect of temperature on the stability of intermediate and final products of inactivated enterovirus 71 vaccine, which was prepared in human diploid cells. METHODS: The different batches of harvest viral cultures, the vaccine stock solutions and the final productions of inactivated enterovirus 71 vaccine were stored at different temperatures. The samples of viral culture stored at -20°C or 4°C were harvested at 0, 6, 12 and 24 months later. The samples of vaccine stock solutions stored at -20°C were harvested at 0, 6, 12 and 24 months later, and that stored at 4°C were harvested at 0, 1, 3, 6 and 12 months later. The samples of finial products were harvested at different time points (0, 6, 12 and 24 months for storing at 4°C; 0, 7, 14, 28, 42 and 60 d for storing at 25°C; 0, 3, 7, 14 and 21 d for storing at 37°C). The viral titer, antigen content, antigen purity, endotoxin content, effectiveness, pH and appearance of samples were determined, respectively. A total of 1 800 BLAB/c mice were immunized by vaccine and 150 control mice were injected by diluents without antigen via intraperitoneal. The tail vein blood (500 µl per mouse) from 1 950 mice were harvested after 4 weeks post injected. The neutralization antibody titers of the serum were tested to calculate the half effective dose (ED50) of final products. All results were analyzed using analysis of variance to compare the differences of the above indexes. RESULTS: The viral titers of harvest viral culture of inactivated EV71 vaccine were (6.67 ± 0.13), (6.56 ± 0.09), (6.52 ± 0.04), (6.39 ± 0.16) lgCCID50/ml (CCID50, the half cell culture infective dose) after 0, 6, 12 and 24 months storage at -20°C; and (6.67 ± 0.13), (6.41 ± 0.13), (6.19 ± 0.18), (5.97 ± 0.09) lgCCID50/ml at 4°C. The viral titers reduced with time (F = 9.81 or 44.16, P < 0.05). The antigen contents of the vaccine stock solution were maintained at (3 626.67 ± 1 382.56) EU/ml within 3 months at 4°C, but were (2 080.00 ± 876.36), (951.17 ± 346.35) EU/ml at 6 and 12 months, respectively. The ED50 of the final production were (31.00 ± 2.71), (32.93 ± 3.22), (39.37 ± 3.44) and (46.04 ± 3.25) EU/ml after 0, 6, 12 and 24 months storage at 4 °C, but were (31.00 ± 2.71), (32.23 ± 2.66), (34.70 ± 1.77), (40.04 ± 2.10), (47.78 ± 1.93) and (56.97 ± 0.50) EU/ml at 0, 7, 14, 28, 42 and 60 days at 25°C, and were (31.00 ± 0.00), (36.20 ± 0.00), (41.87 ± 0.50), (53.25 ± 0.50) and (64.84 ± 0.58) EU/ml at 0, 3, 7, 14 and 21 days at 37°C, respectively. The ED50 had increased with the time by and had significantly differences compared with the beginning level (F = 28.49, 215.15 or 156.12, P < 0.05). CONCLUSION: There is a good stability of the intermediate and final productions of inactivated enterovirus 71 (EV71) vaccines, within 24 months at -20°C or 6 months at 4°C storage for viral culture, 24 months at -20°C or 3 months at 4°C storage for stock solution and 24 months at 4°C or 28 d at 25°C or 7 d at 37°C storage for finial vaccine.

Comparative study of the immunogenicity in mice and monkeys of an inactivated CA16 vaccine made from a human diploid cell line.

The coxsackie A16 virus (CA16), along with enterovirus 71 (EV71), is a primary pathogen that causes hand, foot, and mouth disease (HFMD). To control HFMD, CA16, and EV71 vaccines are needed. In this study, an experimental inactivated CA16 vaccine was prepared using human diploid cells, and the vaccine's immunogenicity was analyzed in mice and rhesus monkeys. The results showed that the neutralizing antibody was developed in a dose-dependent manner, and was sustained for 70 days with an average GMT (geometric mean titer) level of 80 to 90 in immunized mouse and for 56 days with GMT of higher than 300 in monkeys. The neutralizing antibody had a cross-neutralizing activity against different viral strains (genotype A and B), and the specific IFN-γ-secreting cell response was activated by these virus strains in an ELISPOT assay. This study provides evidence for the potential use of inactivated CA16 as a candidate for use in vaccines.

An inactivated enterovirus 71 vaccine in healthy children.

BACKGROUND: Enterovirus 71 (EV71) is a major cause of hand, foot, and mouth disease in children and may be fatal. A vaccine against EV71 is needed. METHODS: We conducted a randomized, double-blind, placebo-controlled phase 3 trial involving healthy children 6 to 71 months of age in Guangxi Zhuang Autonomous Region, China. Two doses of an inactivated EV71 vaccine or placebo were administered intramuscularly, with a 4-week interval between doses, and children were monitored for up to 11 months. The primary end point was protection against hand, foot, and mouth disease caused by EV71. RESULTS: A total of 12,000 children were randomly assigned to receive vaccine or placebo. Serum neutralizing antibodies were assessed in 549 children who received the vaccine. The seroconversion rate was 100% 4 weeks after the two vaccinations, with a geometric mean titer of 170.6. Over the course of two epidemic seasons, the vaccine efficacy was 97.4% (95% confidence interval [CI], 92.9 to 99.0) according to the intention-to-treat analysis and 97.3% (95% CI, 92.6 to 99.0) according to the per-protocol analysis. Adverse events, such as fever (which occurred in 41.6% of the participants who received vaccine vs. 35.2% of those who received placebo), were significantly more common in the week after vaccination among children who received the vaccine than among those who received placebo. CONCLUSIONS: The inactivated EV71 vaccine elicited EV71-specific immune responses and protection against EV71-associated hand, foot, and mouth disease. (Funded by the National Basic Research Program and others; ClinicalTrials.gov number, NCT01569581.).

Study of the integrated immune response induced by an inactivated EV71 vaccine.

UNLABELLED: Enterovirus 71 (EV71), a major causative agent of hand-foot-and-mouth disease (HFMD), causes outbreaks among children in the Asia-Pacific region. A vaccine is urgently needed. Based on successful pre-clinical work, phase I and II clinical trials of an inactivated EV71 vaccine, which included the participants of 288 and 660 respectively, have been conducted. In the present study, the immune response and the correlated modulation of gene expression in the peripheral blood mononuclear cells (PBMCs) of 30 infants (6 to 11 months) immunized with this vaccine or placebo and consented to join this study in the phase II clinical trial were analyzed. The results showed significantly greater neutralizing antibody and specific T cell responses in vaccine group after two inoculations on days 0 and 28. Additionally, more than 600 functional genes that were up- or down-regulated in PBMCs were identified by the microarray assay, and these genes included 68 genes associated with the immune response in vaccine group. These results emphasize the gene expression profile of the immune system in response to an inactivated EV71 vaccine in humans and confirmed that such an immune response was generated as the result of the positive mobilization of the immune system. Furthermore, the immune response was not accompanied by the development of a remarkable inflammatory response. CLINICAL TRIAL REGISTRATION: NCT01391494 and NCT01512706.

Comparative analysis of the immunogenicity and protective effects of inactivated EV71 vaccines in mice.

BACKGROUND: Enterovirus 71 (EV71) is the major causative agent of hand, foot, and mouth disease (HFMD). Three inactivated EV71 whole-virus vaccines of different strains developed by different manufacturers in mainland China have recently entered clinical trials. Although several studies on these vaccines have been published, a study directly comparing the immunogenicity and protective effects among them has not been carried out, which makes evaluating their relative effectiveness difficult. Thus, properly comparing newly developed vaccines has become a priority, especially in China. METHODS AND FINDINGS: This comparative immunogenicity study was carried out on vaccine strains (both live and inactivated), final container products (FCPs) without adjuvant, and corresponding FCPs containing adjuvant (FCP-As) produced by three manufacturers. These vaccines were evaluated by neutralizing antibody (NAb) responses induced by the same or different dosages at one or multiple time points post-immunization. The protective efficacy of the three vaccines was also determined in one-day-old ICR mice born to immunized female mice. Survival rates were observed in these suckling mice after challenge with 20 LD(50) of EV71/048M3C2. Three FCP-As, in a dose of 200 U, generated nearly 100% NAb positivity rates and similar geometric mean titers (GMTs), especially at 14-21 days post-inoculation. However, the dynamic NAb responses were different among three vaccine strains or three FCPs. The FCP-As at the lowest dose used in clinical trials (162 U) showed good protective effects in suckling mice against lethal challenge (90-100% survival), while the ED(50) of NAb responses and protective effects varied among three FCP-As. CONCLUSIONS: These studies establish a standard method for measuring the immunogenicity of EV71 vaccines in mice. The data generated from our mouse model study indicated a clear dose-response relationship, which is important for vaccine quality control and assessment, especially for predicting protective efficacy in humans when combined with future clinical trial results.

The effect of enterovirus 71 immunization on neuropathogenesis and protein expression profiles in the thalamus of infected rhesus neonates.

Enterovirus 71 (EV71) is a major pathogen that causes hand-foot-mouth disease (HFMD). Our previous studies have demonstrated that the complete process of pathogenesis, which may include tissue damage induced by host inflammatory responses and direct tissue damage caused by viral infection, can be observed in the central nervous system (CNS) of animals infected in the laboratory with EV71. Based on these observations, the neuropathogenesis and protein expression profiles in the thalamic tissues of EV71-infected animals were further analyzed in the present study. Changes in protein expression profiles following immunization with the inactivated EV71 vaccine followed by virus challenge were observed and evaluated, and their physiological roles in viral pathogenesis are discussed. Taken together, the results of these experiments provide evidence regarding the neuropathogenesis and molecular mechanisms associated with EV71 infection and identify several protein indicators of pathogenic changes during viral infection.

Analysis of the Th1/Th2 reaction in the immune response induced by EV71 inactivated vaccine in neonatal rhesus monkeys.

Although clinical trials for the enterovirus type 71 (EV71) inactivated vaccine have been progressing, the potential mechanism of EV71 infection and its associated pathogenesis are not well-characterized in terms of comprehensive analysis of the induced immune response, which is generally recognized as an important indicator of the safety of vaccines. To investigate the Th1/Th2 response following viral challenge in neonatal rhesus monkeys immunized with different doses of EV71 inactivated vaccines, the variety of different Th1 and Th2 cytokines in the organs or tissues of the monkeys were identified. The results suggest that depending on the viral challenge, the Th1/Th2 reaction induced by different doses of EV71 inactivated vaccine varies. More specifically, there is an enhanced immune response in 80EU- and 1280EU-immunized monkeys, whereas 320EU immunization induces a mild response. Although there is no direct impact on the variation in immune protection induced by the vaccine, the Th1 reaction functions in T-cell cytotoxicity, which will aid further investigation of the pathogenic characteristics of small pathological changes in the central nerves system (CNS) likely induced by the Th1 response.

A comparative study of the characteristics of two Coxsackie A virus type 16 strains (genotype B).

Coxsackie A virus is one of the major pathogens associated with hand, foot and mouth disease (HFMD). The etiological characteristics of Coxsackie A virus type 16 (CA16) are thought to correlate with the pathological process of its infection. Two CA16 strains that were isolated from a severe HFMD patient presented with different plaque forms. This observation, along with biological analysis, indicated that the differences in the strains' biological characteristics, such as proliferation kinetics and immunogenicity, correlate with differences in their pathogenicity toward neonatal mice. Furthermore, these differences are thought to be associated with the sequence of the 5' non-coding region of the viral genome and the VP1 structural region sequence. The results suggest that the biological and genetic characteristics of the CA16 viral strains are relevant to their pathogenicity.

Establishing China's national standards of antigen content and neutralizing antibody responses for evaluation of enterovirus 71 (EV71) vaccines.

Enterovirus 71 (EV71) is a highly infectious agent that causes hand-foot-mouth disease (HFMD) in humans. Effective vaccination against EV71 infection is critically important, given the recent outbreak of HFMD in the Asia-Pacific region, where it has shown significant mortality and morbidity. There is currently no approved anti-viral therapy available to treat the disease. While several vaccine manufacturers are actively developing EV71 vaccines, there are no international reference standards available to conduct quality control on EV71 vaccines or to assess the effectiveness of EV71 vaccines in immunized populations. In the current report, antigen reference standard based on the C4 subtype of the EV71 vaccine strain was developed. In addition, neutralizing antibody (NTAb) reference panels were analyzed and standards with various neutralizing titers were selected. These reference antigens were used to calibrate vaccine samples from several producers and found that five EV71 antigens and the national reference standards showed good linearity and parallelism. Moreover, mice immunized with various vaccines at doses standardized by these national references showed comparable NTAb responses. Finally, the national NTAb reference panels were found to effectively reduce assay discrepancy between different labs. Taken together, these national reference standards are highly valuable for the standardization and evaluation of EV71 vaccines.

Immunoprotection elicited by an enterovirus type 71 experimental inactivated vaccine in mice and rhesus monkeys.

A number of commonly recognized public health issues are associated with EV71 infection, including the induction of severe cases of hand-foot-and-mouth disease (HFMD). Because of such issues, research and development of EV71 vaccine candidates is of growing importance. In the present study, an experimental EV71 inactivated vaccine was prepared, and its corresponding immunogenicity was analyzed. The immune responses and immunoprotective effect induced by the vaccine in mice and rhesus monkeys are described, and the two animal models are compared to evaluate the potential of assessing the inactivated vaccine's immunogenicity in these two species. In addition to assessing the vaccine's efficacy in mice, our data further elucidate the significance and value of assessing the immunogenicity and immunoprotection of vaccine candidates in rhesus monkeys by relying on a range of analyses, including pathological, etiological and lethal challenge analyses.

Pathogenesis study of enterovirus 71 infection in rhesus monkeys.

Enterovirus 71 (EV71), a major pathogen that is responsible for causing hand-foot-and-mouth disease (HFMD) worldwide, is a member of the Human Enterovirus species A, family Picornaviridae. HFMD that is caused by EV71 is usually characterized by vesicular lesions on the skin and oral mucosa and high morbidity rates in children; additionally, occasional fatal cases have been reported involving brainstem encephalitis and myelitis associated with cardiopulmonary collapse. Although viral pathogenesis in humans is unclear, previous animal studies have indicated that EV71, inoculated via various routes, is capable of targeting and injuring the central nervous system (CNS). We report here the pathogenic process of systemic EV71 infection in rhesus monkeys after inoculation via intracerebral, intravenous, respiratory and digestive routes. Infection with EV71 via these routes resulted in different rates of targeting to and injury of the CNS. Intracerebral inoculation resulted in pulmonary edema and hemorrhage, along with impairment of neurons. However, intravenous and respiratory inoculations resulted in a direct infection of the CNS, accompanied by obvious inflammation of lung tissue, as shown by impairment of the alveoli structure and massive cellular infiltration around the terminal bronchioles and small vessels. These pathological changes were associated with a peak of viremia and dynamic viral distribution in organs over time in the infected monkeys. Our results suggest that the rhesus monkey model may be used to study not only the basic pathogenesis of EV71 viral infections, but also to examine clinical features, such as neurological lesions, in the CNS and pathological changes in associated organs.

Neonatal rhesus monkey is a potential animal model for studying pathogenesis of EV71 infection.

Data from limited autopsies of human patients demonstrate that pathological changes in EV71-infected fatal cases are principally characterized by clear inflammatory lesions in different parts of the CNS; nearly identical changes were found in murine, cynomolgus and rhesus monkey studies which provide evidence of using animal models to investigate the mechanisms of EV71 pathogenesis. Our work uses neonatal rhesus monkeys to investigate a possible model of EV71 pathogenesis and concludes that this model could be applied to provide objective indicators which include clinical manifestations, virus dynamic distribution and pathological changes for observation and evaluation in interpreting the complete process of EV71 infection. This induced systemic infection and other collected indicators in neonatal monkeys could be repeated; the transmission appears to involve infecting new monkeys by contact with feces of infected animals. All data presented suggest that the neonatal rhesus monkey model could shed light on EV71 infection process and pathogenesis.

Optimized development of a candidate strain of inactivated EV71 vaccine and analysis of its immunogenicity in rhesus monkeys.

Enterovirus type 71 (EV71) is one of the main etiologic agents responsible for periodic epidemics of hand-foot-and-mouth disease (HFMD). The prevention and control of EV71 epidemics with effective anti-viral agents and vaccines is very important for public health. Because the pathogenesis of EV71 in the human body is not completely clear and genetic variations in the virus during its replication are difficult to control, we have focused on the development of an inactivated whole-virus vaccine. In this study, we screened 16 strains isolated from different areas of China and selected one strain for the development of an inactivated EV71 vaccine. The results of our study suggest that the FY-23K-B strain, which is a candidate strain for an EV71 inactivated vaccine, satisfied the requirements of vaccine production in terms of genetic stability, biological activity, and good immunogenicity. The experimentally inactivated vaccine produced using this strain was capable of inducing an immune response and offered protection to rhesus monkeys against future virus attacks.

A comparison of the biological characteristics of EV71 C4 subtypes from different epidemic strains.

The comparative analysis of the biological characterization and the genetic background study of EV71 circulating strains is commonly recognized as basic work necessary for development of an effective EV71 vaccine. In this study, we sequenced five EV71 circulating strains, isolated from Fuyang, Hefei, Kunming and Shenzhen city of China and named them FY-23, FY-22, H44, K9 and S1 respectively. The sequence alignment demonstrated their genotypes be C4. The genetic distance of the VP1 gene from these isolates suggested that they were highly co-related with genetic identity similar to other previously reported EV71 strains in China. Additionally, these strains were identified to display some obvious proliferation dynamics and plaque morphology when propagated in Vero cells. However, a distinctive difference in pathogenic ability in neonatal mice was found. Some differences in cross neutralization test & immunogenic analysis were also found. All these results are related to the biological characterization of circulating EV71 strains in China and aid in the development of an EV71 vaccine in the future.

Identification and development of a promising novel mumps vaccine candidate strain.

Mumps epidemics are usually caused by airborne transmission of mumps virus (MuV) and have high morbidity in non-immunized children. Epidemiological studies in many regions of China show that the genotype F viral strain is the most prevalent. However, the genotype A strain is currently used to prepare vaccines. Regional epidemiological MuV data suggest a significant application for the development of live attenuated mumps vaccines targeting specific genotypes. This article reports the isolation and culture of a genotype F MuV candidate strain that could be used to prepare a live attenuated mumps vaccine. This strain is shown to have good immunological efficacy and stability in neurovirulence evaluations. This work should facilitate the implementation of mumps vaccination in mainland China by targeting the most prevalent MuV genotype, genotype F.

Egress of HSV-1 capsid requires the interaction of VP26 and a cellular tetraspanin membrane protein.

HSV-1 viral capsid maturation and egress from the nucleus constitutes a self-controlled process of interactions between host cytoplasmic membrane proteins and viral capsid proteins. In this study, a member of the tetraspanin superfamily, CTMP-7, was shown to physically interact with HSV-1 protein VP26, and the VP26-CTMP-7 complex was detected both in vivo and in vitro. The interaction of VP26 with CTMP-7 plays an essential role in normal HSV-1 replication. Additionally, analysis of a recombinant virus HSV-1-UG showed that mutating VP26 resulted in a decreased viral replication rate and in aggregation of viral mutant capsids in the nucleus. Together, our data support the notion that biological events mediated by a VP26 - CTMP-7 interaction aid in viral capsid enveloping and egress from the cell during the HSV-1 infectious process.

Herpes simplex virus type 1 tegument protein VP22 is capable of modulating the transcription of viral TK and gC genes via interaction with viral ICP0.

VP22, a tegument protein of herpes simplex virus type 1 (HSV-1), is present in many copies in one virion and undergoes different types of post-translational modification. VP22 is believed to have certain functions in viral infection apart from virus assembly. Here we show that VP22 physically interacted with infected cell polypeptide 0 (ICP0) and colocalized in the nucleus, indicating that VP22 could be functionally involved in the modulation of viral transcription through interaction with ICP0. In the HSV-1 infection system and chloramphenicol acetyltransferase (CAT) transcriptional system, VP22-ICP0 interaction was confirmed to play a role in modulating the transcription of some viral genes and could be a factor in viral transcription, which is probably required in the transcriptional control of latent infection.