Heterologous Humoral Response against H5N1, H7N3, and H9N2 Avian Influenza Viruses after Seasonal Vaccination in a European Elderly Population.

Ivan Sanz,Sonia Tamames,José María Eiros,Silvia Rojo,Raúl Ortiz De Lejarazu

doi:10.3390/vaccines5030017

Abstract

Avian influenza viruses are currently one of the main threats to human health in the world. Although there are some screening reports of antibodies against these viruses in humans from Western countries, most of these types of studies are conducted in poultry and market workers of Asian populations. The presence of antibodies against avian influenza viruses was evaluated in an elderly European population. An experimental study was conducted, including pre- and post-vaccine serum samples obtained from 174 elderly people vaccinated with seasonal influenza vaccines of 2006–2007, 2008–2009, 2009–2010, and 2010–2011 Northern Hemisphere vaccine campaigns. The presence of antibodies against A/H5N1, A/H7N3, and A/H9N2 avian influenza viruses were tested by using haemaglutination inhibition assays. Globally, heterotypic antibodies were found before vaccination in 2.9% of individuals against A/H5N1, 1.2% against A/H7N3, and 25.9% against A/H9N2. These pre-vaccination antibodies were present at titers ≥1/40 in 1.1% of individuals against A/H5N1, in 1.1% against H7N3, and in 0.6% against the A/H9N2 subtype. One 76 year-old male showed pre-vaccine antibodies (Abs) against those three avian influenza viruses, and another three individuals presented Abs against two different viruses. Seasonal influenza vaccination induced a significant number of heterotypic seroconversions against A/H5N1 (14.4%) and A/H9N2 (10.9%) viruses, but only one seroconversion was observed against the A/H7N3 subtype. After vaccination, four individuals showed Abs titers ≥1/40 against those three avian viruses, and 55 individuals against both A/H5N1 and A/H9N2. Seasonal vaccination is able to induce some weak heterotypic responses to viruses of avian origin in elderly individuals with no previous exposure to them. However, this response did not accomplish the European Medicament Agency criteria for influenza vaccine efficacy. The results of this study show that seasonal vaccines induce a broad response of heterotypic antibodies against avian influenza viruses, albeit at a low level.

Highlights

Seasonal influenza vaccination is conceived to protect individuals by inducing protective antibodies after annual administration
There is a lack of information about how trivalent influenza vaccines (TIV) can induce heterotypic responses against other non-seasonal influenza viruses, such as avian influenza viruses (AIV)
Men comprised 64.4% (n1 = 29) of those individuals recruited during the 2006–2007 vaccine campaign cohort (VCC), 46.5% (n2 = 20) in the 2008–2009 VCC, 62.8% (n3 = 27)

Summary

Introduction

Seasonal influenza vaccination is conceived to protect individuals by inducing protective antibodies after annual administration. A vaccine able to induce antibodies (Abs) that can recognize all A and B influenza subtypes and lineages is under research through several approaches [1,2,3,4,5,6] This principle is based on the heterotypic response between influenza viruses due to common parts on the structure of their most external proteins, as haemagglutinin (HA), neuraminidase (NA), and. Heterotypic responses are common between phylogenetically-related viruses [10,11] This issue was widely described in a 2009 pandemic, when some authors demonstrated the existence of individuals with antibodies against the A/H1N1pdm subtype, even before their emergence [12,13]. This issue is especially relevant in the current situation in which important avian influenza outbreaks are taking place

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