Method for the simultaneous assay of the different poliovirus types using surface plasmon resonance technology

Skin delivery of trivalent Sabin inactivated poliovirus vaccine using dissolvable microneedle patches induces neutralizing antibodies

The cessation of the oral poliovirus vaccine (OPV) and the inclusion of inactivated poliovirus (IPV) into all routine immunization programmes, strengthens the need for new IPV options. Several novel delivery technologies are being assessed that permit simple yet efficacious and potentially dose-sparing administration of IPV. Current disadvantages of conventional liquid IPV include the dependence on cold chain and the need for injection, resulting in high costs, production of hazardous sharps waste and requiring sufficiently trained personnel. In the current study, a dissolvable microneedle (DMN) patch for skin administration that incorporates trivalent inactivated Sabin poliovirus vaccine (sIPV) was developed. Microneedles were physically stable in the ambient environment for at least 30 min and efficiently penetrated skin. Polio-specific IgG antibodies that were able to neutralize the virus were induced in rats upon administration using trivalent sIPV-containing microneedle patches. These sIPV-patch-induced neutralizing antibody responses were comparable to higher vaccine doses delivered intramuscularly for type 1 and type 3 poliovirus serotypes. Moreover, applying the patches to the flank elicited a significantly higher antibody response compared to their administration to the ear. This study progresses the development of a skin patch-based technology that would simplify vaccine administration of Sabin IPV and thereby overcome logistic issues currently constraining poliovirus eradication campaigns.

Plasmonic Selection of ssDNA Aptamers against Fibroblast Growth Factor Receptor

In this work, we describe the selection of ssDNA aptamers targeting fibroblast growth factor receptor binding protein 3 K650E, which has roles in cell division, growth, and differentiation through the kinase cascade. The selection process was based on the label-free, real-time monitoring of binding interactions by surface plasmon resonance, allowing for convenient manipulation of the selection rounds. Next generation sequencing data provided four major motif families from which nine individual sequences were selected based on their abundance levels. Electrophoretic mobility shift assays revealed binding of the selected aptamers to the target protein without significant interference from fibroblast growth factor receptor binding protein 2, indicating the selectivity of the aptamers. The dissociation constant at equilibrium for the best aptamer candidate, SU-3, was found to be (28.2 ± 19.6) × 10^-9 M (n = 5) using a single-cycle kinetic analysis method. Advantages of the experimental setup and potential applications of the selected aptamers are discussed.

Fluorescence correlation spectroscopy as a sensitive and useful tool for revealing potential overlaps between the epitopes of monoclonal antibodies on viral particles

Although the enzyme-linked immunosorbent assay (ELISA) is well established for quantitating epitopes on inactivated virions used as vaccines, it is less suited for detecting potential overlaps between the epitopes recognized by different antibodies raised against the virions. We used fluorescent correlation spectroscopy (FCS) to detect the potential overlaps between 3 monoclonal antibodies (mAbs 4B7-1H8-2E10, 1E3-3G4, 4H8-3A12-2D3) selected for their ability to specifically recognize poliovirus type 3. Competition of the Alexa488-labeled mAbs with non-labeled mAbs revealed that mAbs 4B7-1H8-2E10 and 4H8-3A12-2D3 compete strongly for their binding sites on the virions, suggesting an important overlap of their epitopes. This was confirmed by the cryo-electron microscopy (cryo EM) structure of the poliovirus type 3 complexed with the corresponding antigen-binding fragments (Fabs) of the mAbs, which revealed that Fabs 4B7-1H8-2E10 and 4H8-3A12-2D3 epitopes share common amino acids. In contrast, a less efficient competition between mAb 1E3-3G4 and mAb 4H8-3A12-2D3 was observed by FCS, and there was no competition between mAbs 1E3-3G4 and 4B7-1H8-2E10. The Fab 1E3-3G4 epitope was found by cryoEM to be close to but distinct from the epitopes of both Fabs 4H8-3A12-2D3 and 4B7-1H8-2E10. Therefore, the FCS data additionally suggest that mAbs 4H8-3A12-2D3 and 4B7-1H8-2E10 bind in a different orientation to their epitopes, so that only the former sterically clashes with the mAb 1E3-3G4 bound to its epitope. Our results demonstrate that FCS can be a highly sensitive and useful tool for assessing the potential overlap of mAbs on viral particles.

Mapping of the epitopes of poliovirus type 2 in complex with antibodies

The inactivated polio vaccine (IPV) contains poliovirus (PV) samples that belong to serotypes 1, 2 and 3. All three serotypes contain the D-antigen, which induces protective antibodies. The antigenic structure of PVs consists of at least four different antigenic sites and the D-antigen content represents the combined activity of multiple epitopes (Ferguson et al., 1993; Minor, 1990; Minor et al., 1986). The potency of IPV vaccines is determined by measuring the D-antigen content. Several ELISA methods have been developed using polyclonal or monoclonal antibodies (Mabs) in order to quantify the D-antigen content. Characterization of the epitopes recognized by the different Mabs is crucial to map the entire virus surface and ensure the presence of epitopes able to induce neutralizing antibodies. Using a new approach that we developed to study the interaction between monoclonal antibodies and poliovirus type 2, which combines cryo-electron microscopy, image analysis and X-ray crystallography along with identification of exposed amino acids, we have mapped in 3D the epitope sites recognized by three specific Fabs at the surface of poliovirus type 2 (PV2) and characterized precisely the antigenic sites for these Fabs.

Structural studies of virus-antibody immune complexes (poliovirus type I): Characterization of the epitopes in 3D

The inactivated polio vaccine (IPV) contains poliovirus (PVs) samples that belong to serotypes 1, 2 and 3. All three serotypes contain the D-antigen, which induces protective antibodies. The antigenic structure of PVs consists of at least four different antigenic sites and the D-antigen content represents the combined activity of multiple epitopes (Ferguson et al., 1993; Minor, 1990; Minor et al., 1986). The potency of IPV vaccines is determined by measuring the D-antigen content. Several ELISA methods have been developed using polyclonal or monoclonal antibodies (Mabs) in order to quantify the D-antigen content. Characterization of the epitopes recognized by the different Mabs is crucial to map the entire virus surface and ensure the presence of epitopes able to induce neutralizing antibodies. In a new approach, combining cryo-electron microscopy and image analysis with X-ray crystallography data available along with identification of exposed amino acids we have mapped in 3D the epitope sites recognized by five specific Fabs and one Mab and characterized precisely the antigenic sites for these Mabs. We propose this method to be used to map the entire "epitopic" surface of virus.