Enterovirus infection of human beta-cells activates dendritic cells and triggers innate antiviral responses: are enteroviruses convicted now?

Identification of conserved neutralizing linear epitopes within the VP1 protein of coxsackievirus A16

Coxsackievirus A16 (CA16) is a major causative agent of hand, foot, and mouth disease. Immunization with inactivated whole-virus or recombinant virus-like particles (VLP) of CA16 elicits neutralizing antibodies that protect mice against lethal challenge. However, the epitope/s responsible for this induction has not been determined. In this investigation, we identified six neutralizing linear epitopes of CA16. A panel of 95 synthetic peptides spanning the entire VP1 protein of CA16 were screened by ELISA for reactivity with neutralizing antisera against CA16 VLPs, which were generated in a previous study (Vaccine 30:6642-6648). Fifteen high-binding peptides were selected and further examined for their inhibitory effect on neutralization by anti-VLP sera. Among them, six peptides with no overlap significantly inhibited neutralization. Mice immunized with these six peptides generated peptide-specific serum antibodies. The anti-peptide antisera positively detected CA16 via immunofluorescent staining and Western blot assays. More importantly, they neutralized both homologous and heterologous CA16 strains, indicating that these six peptides represented neutralizing epitopes. Sequence alignment also showed that these epitopes are extremely conserved among CA16 strains of different genotypes. These findings have important implications for the development of peptide-based broadly protective CA16 vaccines.

Cross-reactive neutralizing antibody epitopes against Enterovirus 71 identified by an in silico approach

Currently, infections of hand, foot and mouth disease (HFMD) due to Human Enterovirus 71 (EV71) cannot be prevented or treated, as there are no suitable vaccines or antiviral drugs. This study aimed to identify potential vaccine candidates for EV71 using in silico analysis of its viral capsid proteins. A combined in silico approach utilizing computational hidden Markov model (HMM), propensity scale algorithm, and artificial learning, identified three 15-mer structurally conserved B-cell epitope candidates lying within the EV71 capsid proteins. Peptide vaccine candidates incorporating a target B-cell epitope and a promiscuous T-cell epitope from the related polio virus were synthesized using solid-phase Fmoc chemistry. Inbred BALB/C mice which were inoculated with two 10μg doses of the synthetic peptide, generated anti-peptide antibodies. Purified IgG isolated from pooled sera of the inoculated mice neutralized EV71 infections in vitro. Furthermore, these neutralizing antibodies were cross-reactive against other members of the Picornaviridae family, demonstrating greater than 50% virus neutralization. This indicates that the current approach is promising for the development of synthetic peptide-based vaccine candidates against Picornaviridae. Development of effective vaccines is of paramount importance in managing the disease in the Asia Pacific regions where this virus is endemic and has significant social, economic and public health ramifications.