Conserved HA-peptide NG34 formulated in pCMV-CTLA4-Ig reduces viral shedding in pigs after a heterosubtypic influenza virus SwH3N2 challenge.

Marta Sisteré-Oró,Jens Nielsen,Patrícia Pleguezuelos,Sonia Pina-Pedrero,Sergi López-Serrano,Ayub Darji,Joaquim Segalés,Enric Vidal,Anders Fomsgaard,Mónica Pérez-Maillo,Lorena Córdoba,Thomas Stratmann,Júlia Vergara-Alert,Veljko Veljkovic

doi:10.1371/journal.pone.0212431

Abstract

Swine influenza viruses (SIVs), the causal agents of swine influenza, are not only important to control due to the economic losses in the swine industry, but also can be pandemic pathogens. Vaccination is one of the most relevant strategies to control and prevent influenza infection. Current human vaccines against influenza induce strain-specific immunity and annual update is required due to the virus antigenic shift phenomena. Previously, our group has reported the use of conserved hemagglutinin peptides (HA-peptides) derived from H1-influenza virus as a potential multivalent vaccine candidate. Immunization of swine with these HA-peptides elicited antibodies that recognized and neutralized heterologous influenza viruses in vitro and demonstrated strong hemagglutination-inhibiting activity. In the present work, we cloned one HA-peptide (named NG34) into a plasmid fused with cytotoxic T lymphocyte-associated antigen (CTLA4) which is a molecule that modifies T cell activation and with an adjuvant activity interfering with the adaptive immune response. The resulting plasmid, named pCMV-CTLA4-Ig-NG34, was administered twice to animals employing a needle-free delivery approach. Two studies were carried out to test the efficacy of pCMV-CTLA4-Ig-NG34 as a potential swine influenza vaccine, one in seronegative and another in seropositive pigs against SIV. The second one was aimed to evaluate whether pCMV-CTLA4-Ig-NG34 vaccination would overcome maternally derived antibodies (MDA). After immunization, all animals were intranasally challenged with an H3N2 influenza strain. A complete elimination or significant reduction in the viral shedding was observed within the first week after the challenge in the vaccinated animals from both studies. In addition, no challenged heterologous virus load was detected in the airways of vaccinated pigs. Overall, it is suggested that the pCMV-CTLA4-Ig-NG34 vaccine formulation could potentially be used as a multivalent vaccine against influenza viruses.

Highlights

Influenza-like disease in pigs started occurring in both United States and Europe in connection with the human influenza pandemic in 1918
Results from the vaccinated pigs with pCMV-CTLA4-Ig showed that none of the three pigs were reducing the viral shedding at 7 dpi (S1 Table)
To determine whether the NG34 peptide of H1N1 origin could confer protection against a heterosubtypic circulating influenza strain, pigs were challenged with the H3N2 influenza virus subtype

Summary

Introduction

Influenza-like disease in pigs started occurring in both United States and Europe in connection with the human influenza pandemic in 1918. Vaccines are commonly administered in pregnant sows to stimulate passive antibody transfer via colostrum Protection with these commercial vaccines is only achieved when the strain either closely or completely matches with the challenged virus [9,10,11,12,13]. Vaccinated MDA positive could reduce virus replication and shedding, suggesting that pCMV-CTLA4-Ig-NG34 vaccine could overcome a possible inhibition/delay in inducing an active antibody and/or cellular immune response [19,27]. Elevated levels of anti-HA specific antibodies at 35 PVD and 7days after a H3N2 inoculation in the vaccinated pigs might have played a role in the elimination of the heterologous challenged virus. A tendency of a higher IgG titer in BALFs against H3N2 and H1N1 subtypes was observed in the vaccinated MDA animals compared to the non-vaccinated ones

Methods

Results

Conclusion