Heterosubtypic Protection against Pathogenic Human and Avian Influenza Viruses via In Vivo Electroporation of Synthetic Consensus DNA Antigens

Abstract

BackgroundThe persistent evolution of highly pathogenic avian influenza (HPAI) highlights the need for novel vaccination techniques that can quickly and effectively respond to emerging viral threats. We evaluated the use of optimized consensus influenza antigens to provide broad protection against divergent strains of H5N1 influenza in three animal models of mice, ferrets, and non-human primates. We also evaluated the use of in vivo electroporation to deliver these vaccines to overcome the immunogenicity barrier encountered in larger animal models of vaccination.Methods and FindingsMice, ferrets and non-human primates were immunized with consensus plasmids expressing H5 hemagglutinin (pH5HA), N1 neuraminidase (pN1NA), and nucleoprotein antigen (pNP). Dramatic IFN-γ-based cellular immune responses to both H5 and NP, largely dependent upon CD8+ T cells were seen in mice. Hemaggutination inhibition titers classically associated with protection (>1:40) were seen in all species. Responses in both ferrets and macaques demonstrate the ability of synthetic consensus antigens to induce antibodies capable of inhibiting divergent strains of the H5N1 subtype, and studies in the mouse and ferret demonstrate the ability of synthetic consensus vaccines to induce protection even in the absence of such neutralizing antibodies. After challenge, protection from morbidity and mortality was seen in mice and ferrets, with significant reductions in viral shedding and disease progression seen in vaccinated animals.ConclusionsBy combining several consensus influenza antigens with in vivo electroporation, we demonstrate that these antigens induce both protective cellular and humoral immune responses in mice, ferrets and non-human primates. We also demonstrate the ability of these antigens to protect from both morbidity and mortality in a ferret model of HPAI, in both the presence and absence of neutralizing antibody, which will be critical in responding to the antigenic drift that will likely occur before these viruses cross the species barrier to humans.

A consensus–hemagglutinin-based DNA vaccine that protects mice against divergent H5N1 influenza viruses

“…Nevertheless, DNA vaccines can be modified readily and rapidly to adjust to changes in the circulating viral populations. Others have reported that a DNA vaccine can protect ferrets and rhesus macaques from H5N1 virus challenge (30,38). We believe the vaccine strategy described herein warrants further evaluation as a potentially fast, affordable, and stable prophylactic approach to combating H5N1 influenza viruses.…”

Prototype development and preclinical immunogenicity analysis of a novel minimally invasive electroporation device

“…Guinea pigs were immunized with a variant of a previously described consensus SynCon influenza vaccine by ID EP by MID. 26,27 The previous studies were conducted with a vaccine targeting avian influenza A/H5N1. In this study, we targeted the induction of protective humoral responses against influenza A/H1N1 strains, including the novel influenza A/Mexico/09/H1N1 (2009).…”

“…Having failed to achieve appreciable expression of plasmid through IM/ID injection alone (without EP) at these doses (GFP data above; and previous immunogenicity studies with DNA alone, [17][18][19][20][21][22] we focused our experiments instead on determining the level of humoral immune responses induced by MID delivery. Animals were vaccinated with a combination of plasmids targeting the H1N1 strains (100 mg per plasmid) containing pGX2005 (SynCon vaccine construct that encodes a consensus sequence of hemagglutinin (HA) from H1N1 viruses) 27 and pGX2009 (SynCon vaccine construct that encodes a consensus HA sequence derived from the swine origin influenza A/H1N1 (2009) strains in a volume of 50 ml diluted in 1Âphosphate-buffered saline (PBS). At 2 weeks following two immunizations, each animal developed robust HA-inhibition (HAI) titers (average (1152±784) and significantly over 1:40 against the pandemic H1N1/Mexico/2009 strain (Figure 6a).…”

“…A number of previous studies have reported on the role of cellular immunity in protecting against morbidity and mortality, resulting from influenza infection. 26,27 Many of these reports have also studied M2e and NP proteins. In our study, mirroring the antibody responses (discussed below), we found that the MID generated higher cellular responses in mice than those observed with an IM device (ELGEN 1000) that uses the same pulse generator, but an IM array configuration with an previously optimized EP parameters.…”

What the Novel H1N1 Influenza Outbreak Can Teach us about Influenza as a Bioterrorism Weapon

“…Thus an increase in Influenza infections, even in the "off-season", would not stimulate an immediate public health response to the same degree as an infectious agent that does not commonly circulate, such as Smallpox. Also of distinct possibility is that the release of such a modified virus would happen during the times of peak seasonal Influenza infection in a country such as the United States, which may allow the attack to be unrealized for a longer period of time, as most initial cases of infection would be thought to be due to poor coverage of the seasonal Influenza vaccine for the circulating strains -an event which most recently happened during 2007 in which the seasonal vaccine afforded only 30% coverage [5]. If we further compound this scenario with the fact that the incubation time for Influenza is relatively short when compared with Smallpox (1-4 days for Flu versus 10-14 days for Smallpox [2]), a situation presents itself in which a Bioterrorism agent has been released without notice due to its possible misevaluation as a standard seasonal viral infection and spreads rapidly through the population to a comparatively rapid degree.…”