Pseudoparticle neutralization is a reliable assay to measure immunity and cross-reactivity to H5N1 influenza viruses
Isabella Alberini1, Elena Del Tordello, Alba Fasolo
1Novartis Vaccines, Siena, Italy.
Abstract:
The standard serological methods present limitations for the measurement of immunity against H5N1 influenza strains. The hemagglutination inhibition (HI) assay lacks sensitivity and requires standardization, while the viral micro-neutralization (MN) assay needs handling of live virus. We produced pseudoparticles expressing hemagglutinin from clades 1 or 2 H5N1 in order to measure neutralizing antibodies in human sera after prime-boost vaccination with plain or MF59-adjuvanted H5N1 clade 1 subunit vaccines. Titers measured by pseudoparticle neutralization (PPN) assay significantly correlated with those measured by HI, single radial haemolysis or MN, with a PPN titer of 1:357 corresponding to an MN titer of 1:80. Notably, results from the PPN assay, confirm that MF59-H5N1 vaccine induces potent and long-lasting neutralizing antibody responses not only against the vaccine strain, but also against several heterologous clade 2 strains. Overall, the PPN assay represents a valid alternative to conventional serological methods for the evaluation of H5N1 vaccine immunogenicity.
Insights
A novel pseudoparticle neutralization (PPN) assay offers a safer and effective alternative for measuring H5N1 influenza immunity. This method correlates well with standard assays and confirms MF59-adjuvanted vaccines induce robust, long-lasting antibody responses.
Area of Science:
- Virology
- Immunology
- Vaccinology
Background:
- Standard serological assays for H5N1 influenza immunity, such as hemagglutination inhibition (HI) and viral micro-neutralization (MN), have limitations including low sensitivity, need for standardization, and handling of live viruses.
- Accurate measurement of neutralizing antibodies is crucial for evaluating the immunogenicity of H5N1 vaccines.
Purpose of the Study:
- To develop and validate a pseudoparticle neutralization (PPN) assay for measuring neutralizing antibodies against H5N1 influenza.
- To compare the PPN assay with established serological methods (HI, single radial haemolysis, MN).
- To assess the immunogenicity of H5N1 clade 1 subunit vaccines (plain and MF59-adjuvanted) using the PPN assay.
Main Methods:
- Production of pseudoparticles expressing hemagglutinin from H5N1 clades 1 or 2.
- Measurement of neutralizing antibodies in human sera from individuals vaccinated with H5N1 clade 1 subunit vaccines using the PPN assay.
- Correlation analysis of PPN assay titers with HI, single radial haemolysis, and MN assay titers.
Main Results:
- PPN assay titers showed significant correlation with HI, single radial haemolysis, and MN assay titers.
- A PPN titer of 1:357 corresponded to an MN titer of 1:80.
- The PPN assay confirmed that MF59-adjuvanted H5N1 vaccine induced potent and long-lasting neutralizing antibody responses against homologous and heterologous clade 2 strains.
Conclusions:
- The pseudoparticle neutralization (PPN) assay is a valid and safer alternative to conventional serological methods for evaluating H5N1 vaccine immunogenicity.
- The PPN assay provides reliable data on neutralizing antibody responses, supporting vaccine development and efficacy assessment.
- MF59-adjuvanted H5N1 vaccines demonstrate strong immunogenicity, inducing broad and durable protection against diverse H5N1 strains.
