Evaluation of In Vitro Cross-Reactivity to Avian H5N1 and Pandemic H1N1 2009 Influenza Following Prime Boost Regimens of Seasonal Influenza Vaccination in Healthy Human Subjects: A Randomised Trial

Delia Bethell,Stuart D Tyner,Nuanpan Khemnu,Jarin Kramyu,David Saunders,Utaiwan Kum-Arb,Douglas S Walsh,Anneke Engering,Arunee Thitithayanont,Richard G Jarman,Mark M Fukuda,Nichapat Uthaimongkol,Sathit Pichyangkul,Anan Jongkaewwattana,Suwimon Wiboon-Ut,Kosol Yongvanitchit,Amporn Limsalakpetch,Duangrat Mongkolsirichaikul,Stephen J Thomas ,Ans Timmermans ,Malik Peiris ,Jean‐Michel Garcia ,Carl J Mason

doi:10.1371/journal.pone.0059674

Abstract

IntroductionRecent studies have demonstrated that inactivated seasonal influenza vaccines (IIV) may elicit production of heterosubtypic antibodies, which can neutralize avian H5N1 virus in a small proportion of subjects. We hypothesized that prime boost regimens of live and inactivated trivalent seasonal influenza vaccines (LAIV and IIV) would enhance production of heterosubtypic immunity and provide evidence of cross-protection against other influenza viruses.MethodsIn an open-label study, 26 adult volunteers were randomized to receive one of four vaccine regimens containing two doses of 2009-10 seasonal influenza vaccines administered 8 (±1) weeks apart: 2 doses of LAIV; 2 doses of IIV; LAIV then IIV; IIV then LAIV. Humoral immunity assays for avian H5N1, 2009 pandemic H1N1 (pH1N1), and seasonal vaccine strains were performed on blood collected pre-vaccine and 2 and 4 weeks later. The percentage of cytokine-producing T-cells was compared with baseline 14 days after each dose.ResultsSubjects receiving IIV had prompt serological responses to vaccine strains. Two subjects receiving heterologous prime boost regimens had enhanced haemagglutination inhibition (HI) and neutralization (NT) titres against pH1N1, and one subject against avian H5N1; all three had pre-existing cross-reactive antibodies detected at baseline. Significantly elevated titres to H5N1 and pH1N1 by neuraminidase inhibition (NI) assay were observed following LAIV-IIV administration. Both vaccines elicited cross-reactive CD4+ T-cell responses to nucleoprotein of avian H5N1 and pH1N1. All regimens were safe and well tolerated.ConclusionNeither homologous nor heterologous prime boost immunization enhanced serum HI and NT titres to 2009 pH1N1 or avian H5N1 compared to single dose vaccine. However heterologous prime-boost vaccination did lead to in vitro evidence of cross-reactivity by NI; the significance of this finding is unclear. These data support the strategy of administering single dose trivalent seasonal influenza vaccine at the outset of an influenza pandemic while a specific vaccine is being developed.Trial RegistrationClinicalTrials.gov NCT01044095

Highlights

Recent studies have demonstrated that inactivated seasonal influenza vaccines (IIV) may elicit production of heterosubtypic antibodies, which can neutralize avian H5N1 virus in a small proportion of subjects
We describe here a pilot feasibility study designed to test the hypothesis that heterologous prime-boost immunization of healthy humans with seasonal trivalent LAIV and IIV would induce evidence of in vitro cross-protection against non-vaccine influenza viruses such as avian H5N1 and pandemic 2009 H1N1
Enrolled subjects were allocated consecutively numbered sealed envelopes containing one of four vaccine regimens: homologous prime boost regimen 1 (Group 1): LAIV two doses separated by 8 weeks (67 days), n = 5; homologous prime boost regimen 2 (Group 2): IIV two doses separated by 8 weeks (67 days), n = 5; heterologous prime boost regimen 1 (Group 3), LAIV single dose, followed by IIV single dose 8 weeks (67 days) later, n = 8; heterologous prime boost regimen 2 (Group 4): IIV single dose followed by LAIV single dose 8 weeks (67 days) later, n = 8

Summary

Introduction

Recent studies have demonstrated that inactivated seasonal influenza vaccines (IIV) may elicit production of heterosubtypic antibodies, which can neutralize avian H5N1 virus in a small proportion of subjects. We hypothesized that prime boost regimens of live and inactivated trivalent seasonal influenza vaccines (LAIV and IIV) would enhance production of heterosubtypic immunity and provide evidence of cross-protection against other influenza viruses. Several avian viruses have crossed the species barrier and directly infected humans, presenting a possible pandemic threat. One of these is avian influenza H5N1 virus, which has a mortality rate of more than 50% in the 600 laboratory-confirmed human cases reported by WHO since 2003 [1]. Ferrets and monkeys demonstrated that a prime boost strategy of a DNA vaccine followed by seasonal IIV conferred protection against a range of influenza viruses by inducing broadly neutralizing antibodies against the stem cell region of the haemagglutinin (HA) glycoprotein [8]

Methods

Results

Conclusion