Selecting vaccine strains that match circulating influenza viruses antigenically remains an annual challenge. Vaccine mismatch [e.g., for recent A(H3N2) viruses] has contributed to reduced vaccine effectiveness. Reduced vaccine effectiveness not only may affect public health, but also causes economic losses due to absenteeism from work. Vaccine mismatches also fuel the ongoing debate about the effectiveness of the influenza vaccine.
To monitor vaccine efficacy and facilitate vaccine strain selection, methods are needed to characterize the antigenic properties of circulating seasonal influenza viruses. The hemagglutination inhibition (HI) assay has been used for this purpose for decades, and is still successfully applied for subtype A(H1N1) and type B virus strains. However, the majority of recently circulating subtype A(H3N2) strains has lost the capacity to agglutinate red blood cells of various species, calling for alternative assays. One of those alternatives is described in the recently published research article: ViroSpot microneutralization assay for antigenic characterization of human influenza viruses (Van Baalen, et. al., Vaccine, 2016; https://dx.doi.org/10.1016/j.vaccine.2016.11.060)
The ViroSpot assay platform has been developed at Viroclinics Biosciences for the detection and phenotypic characterization of influenza viruses in phase 2 and phase 3 clinical trials of new antiviral compounds. It combines classic virus culture techniques with automated sensitive detection of immunostained virus infected cells, and is now also available in a format for antigenic characterization of influenza A(H3N2) viruses. The ViroSpot MN assay has some favorable properties, including the following:
- It measures neutralization of virus binding to cells and subsequent infection, not inhibition of virus replication;
- It is relatively insensitive to differences in test dose of infectious virus between strains;
- Between-strain comparison is on basis of infectious units rather than replication competence;
- Capture and analysis of raw data is automated, with ample possibility for visual confirmation;
- Full traceability of neutralization and match/mismatch results to raw data (i.e., residual infection patterns);
- Compatible with standardized large scale testing of virus isolates.
The various stakeholders in the influenza vaccine field may benefit from the advantages the ViroSpot MN assays offer, which may aid in achieving the ultimate goal of the best possible match between circulating influenza viruses and vaccine strains.
Learn more about Viroclinics Biosciences contributions to vaccine quality, safety and efficacy:
> Download the full article “ViroSpot microneutralization assay for antigenic characterization of human influenza viruses “ here.
> Viroclinics Biosciences is a full-service CLO. Click here to find out more about our services.
> Contact our assay development scientists here.
> Learn more about Viroclinics research models to test vaccine efficacy.
> The ViroSpot assay platform is currently available for influenza virus and RSV, and under development for multiple other viral targets.