Lower seroreactivity to European than to North American H3N2 swine influenza viruses in humans, Luxembourg, 2010

Y Qiu,K Van Reeth,C P Muller

doi:10.2807/1560-7917.es2015.20.13.21078

Y Qiu, K Van Reeth + Show 1 more

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https://doi.org/10.2807/1560-7917.es2015.20.13.21078

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Journal: Eurosurveillance	Publication Date: Apr 2, 2015
Citations: 32	License type: CC BY 4.0

Affiliation: Ghent University

Abstract

Seroreactivity to H3N2 swine influenza viruses (SIVs)was evaluated in serum samples collected from 843 people aged 0 to 100 years in 2010 in Luxembourg.Sera were analysed by haemagglutination inhibition(HI) and virus neutralisation (VN) assays targeting a European H3N2 SIV, a North American H3N2 variant of swine origin (H3N2v) and human seasonal H3N2 viruses isolated in 1975, 1995 and 2005. HI antibodies(titre ≥ 10) against European H3N2 SIV were almost exclusively detected in those born before 1990, of whom 70% were seropositive. HI antibodies against H3N2v were predominantly found in those born before 2000, with 86% seropositive. Titres against the North American H3N2v were higher than against the European H3N2 SIV. VN patterns were similar, but with higher rates and titres. We also demonstrated lower seroreactivity to European H3N2 SIV than to North American H3N2v virus. Finally, we found a strong correlation between HI titres against the European H3N2SIV and H3N2v and their respective human ancestors,A/Victoria/3/75 and A/Nanchang/933/95. This finding and the minimal contacts between humans and pigs in Luxembourg suggest that anti-SIV antibodies inhuman serum samples reflect serological cross-reactivity with historical human H3N2 viruses. Our findings help assess the pandemic risk of H3N2 SIV.

Highlights

Three swine influenza virus (SIV) subtypes, H1N1, H1N2 and H3N2, are enzootic throughout the world in regions with a high density of pigs
The present study was designed to investigate the extent to which prior exposure, through infection or vaccination, to earlier antigenic variants of seasonal influenza A(H3N2) viruses was associated with the presence of antibodies against swine-origin H3N2 viruses from Europe and North America in people in Luxembourg born between 1910 and 2010
Our results demonstrate that as many as 70% of people in the study born before 1990 had detectable haemagglutination inhibition (HI) antibodies against the European H3N2 SIV, whereas such antibodies were generally lacking in those born after 1990

Summary

Introduction

Three swine influenza virus (SIV) subtypes, H1N1, H1N2 and H3N2, are enzootic throughout the world in regions with a high density of pigs. In Europe, H3N2 SIVs are derived from descendants of the A/Hong Kong/1/68 pandemic influenza A(H3N2) virus, but they have evolved further through genetic reassortment with the endemic avianlike H1N1 SIVs present in western Europe since the late 1970s. This has resulted in H3N2 SIVs with human-like HA and NA genes and avian-like internal genes [1,2]. In North America, H3N2 viruses have become established in swine since 1998 They are known as ‘triple-reassortant’ viruses because their HA, NA and polymerase B1 genes stem from human seasonal H3N2 viruses and the remaining internal genes from avian influenza virus and classical H1N1 SIV [3]. These viruses, called H3N2 variant or H3N2v when isolated from humans, have caused many zoonotic infections since 2011 [5]

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