Jian-Feng Han

Rational design of thermostable vaccines by engineered peptide-induced virus self-biomineralization under physiological conditions

The development of vaccines against infectious diseases represents one of the most important contributions to medical science. However, vaccine-preventable diseases still cause millions of deaths each year due to the thermal instability and poor efficacy of vaccines. Using the human enterovirus type 71 vaccine strain as a model, we suggest a combined, rational design approach to improve the thermostability and immunogenicity of live vaccines by self-biomineralization. The biomimetic nucleating peptides are rationally integrated onto the capsid of enterovirus type 71 by reverse genetics so that calcium phosphate mineralization can be biologically induced onto vaccine surfaces under physiological conditions, generating a mineral exterior. This engineered self-biomineralized virus was characterized in detail for its unique structural, virological, and chemical properties. Analogous to many exteriors, the mineral coating confers some new properties on enclosed vaccines. The self-biomineralized vaccine can be stored at 26 °C for more than 9 d and at 37 °C for approximately 1 wk. Both in vitro and in vivo experiments demonstrate that this engineered vaccine can be used efficiently after heat treatment or ambient temperature storage, which reduces the dependence on a cold chain. Such a combination of genetic technology and biomineralization provides an economic solution for current vaccination programs, especially in developing countries that lack expensive refrigeration infrastructures.

Virus-like particles for enterovirus 71 produced from Saccharomyces cerevisiae potently elicits protective immune responses in mice

Human Enterovirus 71 (EV71) is recognized as the leading causative agent of hand-foot-and-mouth disease (HFMD) in the Asia-Pacific region in recent years. There are still no approved antiviral drugs or vaccines against EV71 infection yet. In this study, we have developed an advanced platform for production of the virus-like particles (VLPs) for EV71 in Saccharomyces Cerevisiae by co-expressing P1 and 3CD genes of EV71. These VLPs exhibited similar morphology and protein composition as EV71 empty particles produced from EV71-infected cells. Immunization with VLPs in mice elicited robust neutralization antibodies against EV71 and potent cellular immune response. In vivo challenge experiments showed that the immune sera induced by VLP conferred protection in neonate mice against lethal EV71 challenge. Together, our study indicated that VLP from yeast is another potential vaccine candidate against EV71 infection.

Genomic characterization and phylogenetic analysis of Zika virus circulating in the Americas

The rapid spread and potential link with birth defects have made Zika virus (ZIKV) a global public health problem. The virus was discovered 70years ago, yet the knowledge about its genomic structure and the genetic variations associated with current ZIKV explosive epidemics remains not fully understood. In this review, the genome organization, especially conserved terminal structures of ZIKV genome were characterized and compared with other mosquito-borne flaviviruses. It is suggested that major viral proteins of ZIKV share high structural and functional similarity with other known flaviviruses as shown by sequence comparison and prediction of functional motifs in viral proteins. Phylogenetic analysis demonstrated that all ZIKV strains circulating in the America form a unique clade within the Asian lineage. Furthermore, we identified a series of conserved amino acid residues that differentiate the Asian strains including the current circulating American strains from the ancient African strains. Overall, our findings provide an overview of ZIKV genome characterization and evolutionary dynamics in the Americas and point out critical clues for future virological and epidemiological studies.

Antibody dependent enhancement infection of Enterovirus 71 in vitro and in vivo

BackgroundHuman enterovirus 71 (EV71) has emerged as a significant cause of acute encephalitis and deaths in young children. The clinical manifestations caused by EV71 varied from mild hand, foot and mouth disease to severe neurological complications and deaths, but its pathogenesis remains elusive. Antibody dependent enhancement (ADE) infection has been reported in various viruses and has been shown to contribute to disease severity.ResultsIn this study, the presence of sub-neutralizing antibody was demonstrated to enhance EV71 infection in THP-1 cells and increase the mortality of EV71 infection in a suckling mouse model. Further, a secondary infection model was established to characterize the correlation between ADE and disease severity, and primary asymptomatic EV71 infection was shown to increase the mortality of the secondary EV71 infection in suckling mice.ConclusionsTogether, these in vitro and in vivo experiments strongly supported the hypothesis of ADE infection of EV71. The present findings indicate ADE might contribute to the pathogenesis of severe EV71 infection, and raise practical issues of vaccine development and antibody-based therapy.

Virus-like particles produced in Saccharomyces cerevisiae elicit protective immunity against Coxsackievirus A16 in mice

Hand, foot, and mouth disease (HFMD) has caused significant morbidity and mortality in the Asia-Pacific regions, particularly in infants and young children. Coxsackievirus A16 (CA16) represents one of the major causative agents for HFMD, and the development of a safe and effective vaccine preventing CA16 infections has become a public health priority. In this study, we have developed a yeast system for the production of virus-like particles (VLPs) for CA16 by co-expressing P1 and 3CD of CA16 in Saccharomyces cerevisiae. These VLPs exhibit similarity in both protein composition and morphology as empty particles from CA16-infected cells. Immunization with CA16 VLPs in mice potently induced CA16-specific IgG and neutralization antibodies in a dose-dependent manner. IgG subclass isotyping revealed that IgG1 and lgG2b were dominantly induced by VLPs. Meanwhile, cytokine profiling demonstrated that immunization with VLPs significantly induced the secretion of IFN-γ, indicating potent cellular immune response. Furthermore, in vivo challenge experiments showed that passive immunization with anti-VLPs sera conferred full protection against lethal CA16 challenge in neonate mice. Taken together, our data demonstrated that VLPs produced in yeast might have the potential to be further developed as a vaccine candidate against HFMD.

Human enterovirus 71 uncoating captured at atomic resolution.

ABSTRACT Human enterovirus 71 (EV71) is the major causative agent of severe hand-foot-and-mouth diseases (HFMD) in young children, and structural characterization of EV71 during its life cycle can aid in the development of therapeutics against HFMD. Here, we present the atomic structures of the full virion and an uncoating intermediate of a clinical EV71 C4 strain to illustrate the structural changes in the full virion that lead to the formation of the uncoating intermediate prepared for RNA release. Although the VP1 N-terminal regions observed to penetrate through the junction channel at the quasi-3-fold axis in the uncoating intermediate of coxsackievirus A16 were not observed in the EV71 uncoating intermediate, drastic conformational changes occur in this region, as has been observed in all capsid proteins. Additionally, the RNA genome interacts with the N-terminal extensions of VP1 and residues 32 to 36 of VP3, both of which are situated at the bottom of the junction. These observations highlight the importance of the junction for genome release. Furthermore, EV71 uncoating is associated with apparent rearrangements and expansion around the 2- and 5-fold axes without obvious changes around the 3-fold axes. Therefore, these structures enabled the identification of hot spots for capsid rearrangements, which led to the hypothesis that the protomer interface near the junction and the 2-fold axis permits the opening of large channels for the exit of polypeptides and viral RNA, which is an uncoating mechanism that is likely conserved in enteroviruses. IMPORTANCE Human enterovirus 71 (EV71) is the major causative agent of severe hand-foot-and-mouth diseases (HFMD) in young children. EV71 contains an RNA genome protected by an icosahedral capsid shell. Uncoating is essential in EV71 life cycle, which is characterized by conformational changes in the capsid to facilitate RNA release into host cell. Here we present the atomic structures of the full virion and an uncoating intermediate of a clinical C4 strain of EV71. Structural analysis revealed drastic conformational changes associated with uncoating in all the capsid proteins near the junction at the quasi-3-fold axis and protein-RNA interactions at the bottom of the junction in the uncoating intermediate. Significant capsid rearrangements also occur at the icosahedral 2- and 5-fold axes but not at the 3-fold axis. Taking the results together, we hypothesize that the junction and nearby areas are hot spots for capsid breaches for the exit of polypeptides and viral RNA during uncoating.

Human IgG Subclasses against Enterovirus Type 71: Neutralization versus Antibody Dependent Enhancement of Infection

The emerging human enterovirus 71 (EV71) represents a growing threat to public health, and no vaccine or specific antiviral is currently available. Human intravenous immunoglobulin (IVIG) is clinical used in treating severe EV71 infections. However, the discovery of antibody dependent enhancement (ADE) of EV71 infection illustrates the complex roles of antibody in controlling EV71 infection. In this study, to identify the distinct role of each IgG subclass on neutralization and enhancement of EV71 infection, different lots of pharmaceutical IVIG preparations manufactured from Chinese donors were used for IgG subclass fractionation by pH gradient elution with the protein A-conjugated affinity column. The neutralization and ADE capacities on EV71 infection of each purified IgG subclass were then assayed, respectively. The neutralizing activity of human IVIG is mainly mediated by IgG1 subclass and to less extent by IgG2 subclass. Interestingly, IgG3 fraction did not have neutralizing activity but enhanced EV71 infection in vitro. These results revealed the different roles of human IgG subclasses on EV71 infection, which is of critical importance for the rational design of immunotherapy and vaccines against severe EV71 diseases.

Characterization of enterovirus 71 and coxsackievirus A16 isolated in hand, foot, and mouth disease patients in Guangdong, 2010

BACKGROUND Hand, foot, and mouth disease (HFMD) is an acute viral disease caused by human enteroviruses, especially human enterovirus 71 (HEV71) and coxsackievirus A16 (CVA16), and mainly affects infants and young children. After the outbreak in 2008 in Fuyang, China, HFMD was classified as a category C notifiable infectious disease by the Ministry of Health of China. METHODS In this study, we report the epidemiologic and clinical manifestations of HFMD in Guangdong Province, China in 2010, and characterize HEV71 and CVA16 isolated from clinical specimens. RESULTS Among the 542 HFMD patients, 495 (91.3%) were positive for enterovirus as detected by real-time reverse transcriptase PCR; 243 were positive for HEV71 (49.1%, 243/495) and 114 were positive for CVA16 (23.0%, 114/495). Most of the affected children were aged 5 years or under (93.7%, 508/542). Phylogenetic analyses of VP1 gene sequences showed that the HEV71 isolates belonged to C4a subgenotype, and CVA16 isolates belonged to B1 genotype. CONCLUSIONS Our results demonstrate that HEV71 and CVA16 are the primary causative agents responsible for HFMD in Guangdong Province, and their co-circulation poses a potential risk to public health.

Identification of a recombinant dengue virus type 1 with 3 recombination regions in natural populations in Guangdong province, China

Using recombination analysis, we identified a recombinant dengue virus type 1 strain, namely, GD23/95, with three recombination regions, located within the sequences of the prM/E junction, NS1, and NS3, respectively. The recombinant dengue virus was further confirmed by phylogenetic analysis based on its recombination and non-recombination regions. This appears to be the first study to confirm the existence of three recombination regions in a single dengue virus isolate and to report recombination between parent virus strains isolated from the same geographic area (Guangdong province, China). It is also the first to report breakpoints within the NS3 gene of dengue viruses.

Development and Evaluation of a Reverse Transcription-Loop-Mediated Isothermal Amplification Assay for Rapid Detection of Enterovirus 71

ABSTRACT Human enterovirus 71 (EV71) is the major etiological agent of hand, foot, and mouth disease (HFMD), which is a common infectious disease in young children and infants. EV71 can cause various clinical manifestations and has been associated with severe neurological complications; it has resulted in fatalities during recent outbreaks in Asian-Pacific regions since 1997. The early and rapid detection is critical for prevention and control of EV71 infection, since no vaccine or antiviral drugs are currently available. In this study, a simple and sensitive reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay was developed for rapid detection of EV71. The detection limit of the RT-LAMP assay was approximately 0.01 PFU per reaction mixture, and no cross-reactive amplification with other enteroviruses was observed. The assay was evaluated further with 40 clinical specimens and exhibited 92.9% sensitivity and 100% specificity. This RT-LAMP assay may become a useful alternative in clinical diagnosis of EV71, especially in resource-limited hospitals or rural clinics of China and other countries in the Asian-Pacific region.