Microneutralization assay titres correlate with protection against seasonal influenza H1N1 and H3N2 in children.

Chris P Verschoor,Dawn M E Bowdish,Margaret L Russell,Brian J Ward,Louis Cyr,Pardeep Singh,Mark Loeb,Angela Brewer,Benjamin J Cowling

doi:10.1371/journal.pone.0131531

Abstract

Although the microneutralization (MN) assay has been shown to be more sensitive than the hemagglutination inhibition (HAI) assay for the measurement of humoral immunity against influenza viruses, further evidence relating MN titres to protective efficacy against infection is needed. Serum antibodies against seasonal H1N1 and H3N2 influenza were measured in children and adolescents (n = 656) by MN and hemagglutination inhibition (HAI) assays. Compared to HAI, the MN assay is more sensitive in detecting serum antibodies and estimates of protective effectiveness against PCR-confirmed infection were higher for both subtypes. Given our findings, the MN assay warrants further consideration as a formal tool for the routine evaluation of vaccine-induced antibody responses.

Highlights

The quantification of serum antibodies to microbial antigens, following immunization, has long been used to assess the likelihood of protection against infection
An hemagglutination inhibition (HAI) titre of 1:40 for H1N1 and H3N2 related to MN titres of approximately 1:200 (H1N1, Fig 1A) and 1:140 (H3N2, Fig 1B), respectively
The goal of the following study was to compare titres derived from the HAI and MN assays, and estimate their protective effectiveness against season H1N1 and H3N2 influenza infection in a cohort of children and adolescents aged 3–15

Summary

Introduction

The quantification of serum antibodies to microbial antigens, following immunization, has long been used to assess the likelihood of protection against infection. One of the classical ways of measuring such antibodies has been the hemagglutination inhibition (HAI) assay, which assesses the ability of test sera to prevent the agglutination of red blood cells by particulate antigens With regard to vaccine-induced protection against influenza infection, it is widely thought that an HAI titre 1:40 corresponds to a 50% reduction in the prevalence of infection [1]. Black and colleagues (2011) estimated that a more appropriate HAI cutoff for 50% protection in children would instead be 1:110 [2]. Others have reported that 1:40 is likely too low of an HAI titre cut-off for adequate protection in the elderly as well [3]

Methods

Results

Conclusion