A West Nile virus (WNV) recombinant canarypox virus vaccine elicits WNV-specific neutralizing antibodies and cell-mediated immune responses in the horse
Introduction
An improved understanding of the contribution of the different immune responses to the prevention and control of infectious diseases is an important step towards rational design of new vaccines. Immune responses to viruses have been extensively studied in humans and mice. In particular, cell-mediated and innate immunity are generally recognized as important for the control and elimination of viral infections (Boehme and Compton, 2004, Doherty, 1996). Several functional assays have been developed to measure cell-mediated immune responses (O’Neill et al., 1999, Paillot et al., 2006). The results of these studies have shown important differences in the immune responses induced by conventional killed vaccines and those resulting from natural infection (Daly et al., 2004). In view of these qualitative differences, significant effort has been directed in the past decade towards the development of equine vaccines that induce strong cellular immune responses. These approaches include the use of plasmid DNA vaccines (Minke et al., 2006) and live vectored vaccines (Breathnach et al., 2004).
One of the most significant changes in the field of veterinary vaccines over the past few years has been the development of several recombinant vaccines based on the canarypox vector (ALVAC®) (Edlund Toulemonde et al., 2005, Karaca et al., 2005, Minke et al., 2007, Pardo et al., 1997, Poulet et al., 2003). Canarypox virus vectors undergo an abortive replication cycle in mammalian cells during which the inserted gene product (transgene) is expressed which results in the stimulation of both humoral and cell-mediated immune responses in a manner similar to a natural infection (Berencsi et al., 2001, Nacsa et al., 2004, Santra et al., 2002). Although not fully explained in its mechanism, canarypox virus vector allows for a strong immunogenicity of the recombinant antigen. Ignatius et al. reported that canarypox vectors were able to induce dendritic cells (DCs) maturation in vitro (Ignatius et al., 2000) but other mechanisms by which these vectors may influence immunogenicity of the transgene could exist. Very interestingly, canarypox vectors appear free of the inhibitory effects of vector immunity even after multiple injections (Franchini et al., 2004). In this regard, canarypox viruses successfully combine the safety of an inactivated vaccine with the efficacy of a modified live vaccine.
Recently, a recombinant West Nile virus (WNV) canarypox vector vaccine has been developed (Minke et al., 2004, Siger et al., 2004) for use in horses against WNV infection, a mosquito-transmitted flavivirus responsible for a potentially fatal or debilitating disease in horses and humans (Hayes and Gubler, 2006). Because horses infected with WNV would benefit from pre-existing virus-specific memory humoral and cell-mediated immune responses (Shrestha and Diamond, 2004), we investigated whether vaccination with the recombinant ALVAC®-WNV vaccine would induce these immune responses in the horse. In addition, we examined whether pre-existing immunity against the canarypox virus vector would inhibit subsequent immune responses against the transgene following repeated injections with this vaccine.
Section snippets
Vaccines
The WNV vaccine consisted of a commercial preparation of a freeze-dried vaccine containing recombinant canarypox virus (ALVAC®) expressing the prM/E genes derived from a 1999 New York isolate of WNV (Gould and Fikrig, 2004). Prior to immunization, the vaccine was reconstituted with 1 ml of diluent containing CARBOPOL® 974P adjuvant (BF Goodrich Chemicals Europe NV, Belgium) at a concentration of 4 mg/ml.
Animals and vaccination schedule
Ten horses (Welsh Mountain ponies and mixed breed) of both sexes were used in this study. The
WNV-specific IFN-γ+ cell responses
The WNV-specific IFN-γ+ responses in vaccinated and control horses are shown in Fig. 2. Only moderate non-specific IFN-γ signals were found at some time points in the non-vaccinated horses (Fig. 2B). In contrast, upon ex vivo stimulation with WNV antigens, prM/E-specific IFN-γ+ responses were found in all ALVAC®-WNV vaccinated horses following the primary vaccination course of two doses. These responses declined over time but were still detectable in two out of five horses on day 91, the last
Discussion
Several studies have examined immune correlates of protection against WNV in mouse models. Although neutralizing antibodies are thought to play a major role in eliminating viremia (Diamond et al., 2003a), the antibody response itself does not completely eliminate virus reservoirs in immunocompromised mice (Engle and Diamond, 2003). It has been established in flavivirus murine infection models that cell-mediated immune responses may contribute to viral protection (Diamond et al., 2003b), and
Acknowledgements
P.M. Guigal and the animal caretakers are gratefully acknowledged for their outstanding management of the horse trials.
References (39)
- et al.
Use of recombinant modified vaccinia Ankara viral vectors for equine influenza vaccination
Vet. Immunol. Immunopathol.
(2004) - et al.
Safety and immunogenicity of NYVAC-JEV and ALVAC-JEV attenuated recombinant Japanese encephalitis virus—poxvirus vaccines in vaccinia-nonimmune and vaccinia-immune humans
Vaccine
(2000) - et al.
Recombinant canarypox vectored West Nile virus (WNV) vaccine protects dogs and cats against a mosquito WNV challenge
Vaccine
(2005) - et al.
Vaccination with two different vaccinia recombinant viruses: long-term inhibition of secondary vaccination
Vaccine
(1993) - et al.
Use of DNA and recombinant canarypox viral (ALVAC) vectors for equine herpes virus vaccination
Vet. Immunol. Immunopathol.
(2006) - et al.
Avipox-based simian immunodeficiency virus (SIV) vaccines elicit a high frequency of SIV-specific CD4+ and CD8+ T-cell responses in vaccinia-experienced SIVmac251-infected macaques
Vaccine
(2004) - et al.
Determination of equid herpesvirus 1-specific, CD8+, cytotoxic T lymphocyte precursor frequencies in ponies
Vet. Immunol. Immunopathol.
(1999) - et al.
Equine interferon gamma synthesis in lymphocytes after in vivo infection and in vitro stimulation with EHV-1
Vaccine
(2005) - et al.
Characterisation of CTL and IFN-gamma synthesis in ponies following vaccination with a NYVAC-based construct coding for EHV-1 immediate early gene, followed by challenge infection
Vaccine
(2006) - et al.
A canarypox vector-expressing cytomegalovirus (CMV) phosphoprotein 65 induces long-lasting cytotoxic T cell responses in human CMV-seronegative subjects
J. Infect. Dis.
(2001)
Innate sensing of viruses by toll-like receptors
J. Virol.
Serological evidence of West Nile virus, Usutu virus and Sindbis virus infection of birds in the UK
J. Gen. Virol.
Comparative immunogenicity in rhesus monkeys of DNA plasmid, recombinant vaccinia virus, and replication-defective adenovirus vectors expressing a human immunodeficiency virus type 1 gag gene
J. Virol.
Current perspectives on control of equine influenza
Vet. Res.
B cells and antibody play critical roles in the immediate defense of disseminated infection by West Nile encephalitis virus
J. Virol.
Innate and adaptive immune responses determine protection against disseminated infection by West Nile encephalitis virus
Viral Immunol.
Cytotoxic T cell effector and memory function in viral immunity
Curr. Top. Microbiol. Immunol.
Efficacy of a recombinant equine influenza vaccine against challenge with an American lineage H3N8 influenza virus responsible for the 2003 outbreak in the United Kingdom
Vet. Rec.
Antibody prophylaxis and therapy against West Nile virus infection in wild-type and immunodeficient mice
J. Virol.
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