Topic:Vaccine development
Vaccine development in horses involves the creation and refinement of immunizations to protect equine populations from infectious diseases. This process includes identifying antigens, formulating vaccines, and evaluating their safety and efficacy through clinical trials. Vaccines stimulate the horse's immune system to recognize and combat specific pathogens, thereby reducing the incidence and severity of diseases. Common equine vaccines target diseases such as equine influenza, tetanus, and West Nile virus. This page compiles peer-reviewed research studies and scholarly articles that explore the methodologies, challenges, and advancements in vaccine development for equine health.
Full protection against African horsesickness (AHS) in horses induced by baculovirus-derived AHS virus serotype 4 VP2, VP5 and VP7. African horsesickness virus serotype 4 (AHSV-4) outer capsid protein VP2, or VP2 and VP5 plus inner capsid protein VP7, derived from single or dual recombinant baculovirus expression vectors were used in different combinations to immunize horses. When the proteins were purified by affinity chromatography, the combination of all three proteins induced low levels of neutralizing antibodies and conferred protection against virulent virus challenge. However, purified VP2 or VP2 and VP5 in the absence of VP7 failed to induce neutralizing antibodies and protection. Immunization with non-purified pro...
Equine influenza. A highly contagious virus infection of horses, influenza is the single most important equine respiratory disease in many countries. Two subtypes of equine influenza virus have been identified, A/equine-1 and A/equine-2, neither of which immunologically cross-reacts. In the case of A/equine-2 virus, two lineages exist, American and European, which appear to have evolved independently of one another. The acute febrile respiratory disease characteristic of influenza is frequently complicated by secondary bacterial infection, especially in unvaccinated horses. Primarily a respiratory-borne infecti...
Antigenic and genetic evolution of equine H3N8 influenza A viruses. Evolution of equine influenza a H3N8 viruses was examined by antigenic and genetic analysis of a collection isolates from around the world. It was noted that antigenic and genetic variants of equine H3N8 viruses cocirculate, and in particular that variants currently circulating in Europe and the USA are distinguishable from one another both in terms of antigenic reactivity and genetic structure of the HA1 portion of the haemagglutinin (HA) molecule. Whilst the divergent evolution of American and European isolates may be due to geographical isolation of the two gene pools, some mixing is believ...
Fine specificity of equine infectious anaemia virus gp90-specific antibodies associated with protective and enhancing immune responses in experimentally infected and immunized ponies. Equine infectious anaemia virus (EIAV) provides a model for examining the natural immunological control of a persistent lentivirus infection and for evaluating the efficacy of various vaccine strategies. As an initial characterization of antibody responses associated with protective or enhancing immune responses elicited by experimental infections or vaccinations, we have utilized synthetic peptide ELISA to characterize the fine specificity of antibodies to linear determinants of the EIAV surface glycoprotein, gp90. The data indicated that serum antibodies associated with protective or enhanci...
Lack of virulence of the murine fibroblast adapted strain, Kentucky A (KyA), of equine herpesvirus type 1 (EHV-1) in young horses. The virulence of the cell culture adapted KyA strain of equine herpesvirus type 1 (EHV-1), which lacks at least six genes by deletions in its genome, was assessed by intranasal inoculation of six young horses that were serologically negative for EHV-1. No horses showed clinical signs, and a neutralizing antibody response against EHV-1 was detected in two horses which had antibodies against EHV-4 prior to the inoculation. A challenge experiment using a highly virulent strain of EHV-1 conducted 4 weeks later against 4 of the 6 horses inoculated intranasally with the KyA strain and 2 control hors...
Expression cloning and antigenic analysis of the nucleocapsid protein of equine arteritis virus. A series of recombinant fusion proteins derived from equine arteritis virus (EAV) open reading frame (ORF) 7 have been used to define the immunoreactive region of the viral nucleocapsid (N) protein. Reactivities of recombinant N fusion proteins with post-infection equine sera in immunoblots and ELISAs indicate that the major nucleocapsid protein epitope is located within amino acid residues 1-69. In ELISAs two recombinant nucleocapsid fusion proteins containing residues 1-69 (rN1-69) and 1-28 (rN1-28) discriminated between pre- and post-infection, and pre- and post-vaccination serum samples. A...
The use of African horse sickness virus NS3 protein, expressed in bacteria, as a marker to differentiate infected from vaccinated horses. Segment 10 of the double-stranded RNA (dsRNA) genome from African horse sickness virus serotype 4 (AHSV-4) was cloned and sequenced. The sequence of the coding region showed a total length of 667 bp. Nucleotide comparisons showed a 95% sequence similarity between serotypes 4 and 9, and 76% between serotypes 4 and 3. cDNA clones containing the coding region were cloned in the vector pET3xb and expressed in Escherichia coli. The NS3 gene product was synthesised at very high level as an insoluble fusion protein. The recombinant protein was used in a differential ELISA to distinguish horses that w...
An assessment of mucosal immunisation in protection against Streptococcus equi (‘Strangles’) infections in horses. The ability of mucosally administered antigen to provide protection against Streptococcus equi ('Strangles') infections in horses was examined. First, an enzyme linked immunosorbent assay (ELISA) was developed to detect the immune status of horses to S. equi. This assay was used to select Strangles-naive horses for the study and also to monitor their response to immunisation. Potential vaccine candidates were: (a) orally administered paraformaldehyde killed S. equi; (b) intraperitoneally (IP) administered paraformaldehyde killed S. equi in a non-inflammatory adjuvant; (c) orally administered l...
Characteristics of equine herpesvirus 1 glycoproteins expressed in insect cells. A series of recombinant baculoviruses containing genes for glycoproteins C, D, H and L of equine herpesvirus 1 (EHV-1) have been constructed, and the EHV-1 products characterised by gel electrophoresis and immunoblotting. The EHV-1 glycoproteins expressed in insect cells were similar but not identical in apparent sizes to those expressed in EHV-1 infected mammalian cells. Each of the EHV-1 products was recognised by convalescent equine sera, indicating that they were all targets for an equine immune response. Mice immunised with baculovirus-expressed EHV-1 gD and gC acquired an enhanced abilit...
Equine arteritis virus-neutralizing antibody in the horse is induced by a determinant on the large envelope glycoprotein GL. Complementary DNAs encoding ORFs 2 to 7 equine arteritis virus (EAV) have been cloned into the expression vector pGEX to produce glutathione-S-transferase fusion proteins. Recombinant proteins were affinity purified and screened in ELISA with equine sera to identify immunoreactive polypeptides. The large envelope glycoprotein (GL) was identified as the most reactive to EAV-positive equine sera and an immuno-dominant epitope was mapped between amino acids 55 and 98 by subcloning and expression. A fusion protein covering this region and a GL-specific synthetic peptide (residues 75 through 97) in...
Detection of tetanus toxoid-specific memory T cells in equine lymph nodes but not in peripheral blood. The use of tetanus toxoid as a recall antigen to investigate equine immune responses would be, in theory, a useful and cost-effective model in vitro. However, by using various regimens for culturing peripheral blood mononuclear cells from horses previously immunised with toxoid no proliferative response to the antigen was obtained in vitro, whereas lymph node mononuclear cells from the same animals proliferated significantly in response to it. The lack of response by the peripheral blood mononuclear cells was not due to the presence of a suppressive factor but to a lack of recognition of the a...
Development and evaluation of an ELISA using recombinant fusion protein to detect the presence of host antibody to equine arteritis virus. A recombinant glutathione-S-transferase fusion protein expressing amino acids 55-98 of equine arteritis virus (EAV) GL (rGL 55-98) was tested in an ELISA for its ability to detect serum antibodies to EAV. Host antibodies induced following EAV infection bound the recombinant antigen by ELISA. The ELISA specificity and sensitivity were determined with a panel of equine sera including postinfection and postvaccination samples. A good correlation existed between EAV neutralizing antibody titers and ELISA absorbance values (r = 0.827). The sensitivity and specificity of the ELISA were 99.6 and 90.1...
Localization of a protective epitope on a Venezuelan equine encephalomyelitis (VEE) virus peptide that protects mice from both epizootic and enzootic VEE virus challenge and is immunogenic in horses. In order to define more precisely the protective epitope encoded within the first 25 amino acids (aa) of the E2 glycoprotein of the Trinidad donkey strain of Venezuelan equine encephalomyelitis (VEE) virus, we examined the immunogenicity of smaller peptides within the first 19 aa. pep1-9 and pep3-10 elicited virus-reactive antibody, but failed to protect mice from virus challenge. Additionally, pep3-10 was identified by a competitive binding assay using overlapping peptide octamers as the putative binding site of the antipeptide monoclonal antibody (mAb) 1A2B-10. Since the E2 amino-terminal se...
Detection of equine arteritis virus (EAV) by polymerase chain reaction (PCR) and differentiation of EAV strains by restriction enzyme analysis of PCR products. A polymerase chain reaction (PCR) based assay capable of detecting and differentiating seven strains of equine arteritis virus (EAV) from around the world was developed. The primers for the PCR were chosen from the ORF6 gene encoding the unglycosylated membrane protein (M). Viral RNA from cell culture fluids infected with each of the seven EAV strains and RNA from the live vaccine, Arvac, was detected by PCR using four sets of primers. The sensitivity of detection was increased from 100 to 1,000 times by performing nested PCR enabling the detection of RNA at a level of 0.5-5 PFU. Differentiati...
Distribution of equid herpesvirus-1 (EHV-1) in the respiratory tract of ponies: implications for vaccination strategies. Twelve adult ponies and 2 conventional foals were exposed to 10(6.6) TCID50 of Equid herpesvirus-1 (EHV-1), strain Ab4 and samples of respiratory tract tissues were recovered. Infectious virus in tissue homogenates was detected using susceptible cell monolayers and expression of viral antigens was monitored using indirect immunoperoxidase histochemistry of paraffin sections. The results illustrated the rapid dissemination of EHV-1 throughout the respiratory tract, with early replication in the lungs one day after exposure. Endothelial cell infection was prominent in all areas of the nasopharyn...
African horsesickness: pathogenesis and immunity. African horsesickness (AHS) is a serious, non-contagious disease of horses and other solipeds caused by an arthropod-borne orbivirus of the family Reoviridae. In horses, AHS causes three distinct clinicopathologic syndromes, the pulmonary, cardiac and fever forms of the disease. Recent work has shown that the primary determinant of the form of disease expressed by naive horses is the virulence of the virus inoculum. Horses which recover from AHS exhibit solid humoral immunity against homologous challenge. Protective antibodies appear to be directed towards neutralizing epitopes on AHS virus VP...
Expression of functional protease and subviral particles by vaccinia virus containing equine infectious anaemia virus gag and 5′ pol genes. Cells infected with vaccinia viruses expressing the equine infectious anaemia virus (EIAV) gag gene (VGag) or gag plus the 5' pol encoding protease (VGag/PR) were evaluated with monoclonal antibody to a p26 capsid protein linear epitope (QEISKFLTD). Both recombinant viruses expressed Gag precursor protein (55K) whereas only VGag/PR expressed a detectable Gag-Pol fusion protein (82K) with a functional protease, shown by subviral particles containing processed p26. Horses inoculated with VGag/PR produced antibodies reactive with EIAV Gag proteins.
Antigenicity and immunogenicity of equine influenza vaccines containing a Carbomer adjuvant. Equine influenza vaccines containing inactivated whole virus and Carbomer adjuvant stimulated higher levels and longer lasting antibody to haemagglutinin in ponies than vaccines of equivalent antigenic content containing aluminium phosphate adjuvants. Five months after the third dose of vaccine containing Carbomer adjuvant, ponies were protected against clinical disease induced by an aerosol of virulent influenza virus (A/equine/Newmarket/79, H3N8). In contrast ponies which received vaccine containing aluminium phosphate adjuvant were susceptible to infection and disease. There was an inverse ...
Enhancement of EIAV replication and disease by immunization with a baculovirus-expressed recombinant envelope surface glycoprotein. The potential for antibody-dependent enhancement of replication of macrophage/monocyte tropic viruses has posed a significant problem in the development of vaccines for several animal and human viruses and has raised significant concern in the design of potential AIDS vaccines. Using the previously described equine infectious anemia virus/Shetland pony system as a model for HIV-1 vaccine development, we have evaluated the efficacy of a recombinant subunit vaccine containing a baculovirus-expressed envelope surface glycoprotein (gp90) of EIAV. The results of these trials demonstrate not only th...
Immunogens of encephalitis viruses. The equine encephalitis viruses are members of the genus Alphavirus, in the family Togaviridae. Three main virus serogroups represented by western (WEE), eastern (EEE) and Venezuelan equine encephalitis (VEE) viruses cause epizootic and enzootic infection of horses throughout the western hemisphere. All equine encephalitis viruses are transmitted through the bite of an infected mosquito. The first equine encephalitis virus vaccines were produced by virus inactivation. Problems with inadequate inactivation, which may have caused a major epidemic/epizootic of VEE in central America and Texas in ...
Immunocastration of colts and immunospeying of fillies. A series of experiments using an ovalbumin conjugated gonadotrophin releasing hormone was used to stimulate antibody production, suppress testosterone secretion and depress testicular function in yearling and 2 year old colts and fillies. In the preliminary experiment, an injectable oil-based formulation was administered to yearling colts. Testicular development and testosterone secretion were retarded for a period of approximately 28-32 weeks while antibody titres were greater than 1:1000. An implant and water-soluble vaccine (200 and 400 mg) is presently being tested in 2 year old colts. Tes...
[The immunogenic properties of a recombinant vaccinia virus with an incorporated DNA copy of the 26S RNA of the Venezuelan equine encephalomyelitis virus]. A recombinant strain of vaccinia virus (VR26) containing a DNA-copy of the subgenomic 26S RNA of Venezuelan equine encephalomyelitis virus (VEE) inserted into the coding region of thymidine kinase (TK) gene was produced. This subgenomic RNA contained the genes for all structural proteins of the VEE virus, the strain Trinidad donkey (TRD). VR26 effectively expressed VEE virus glycoproteins on the membranes of the infected cells. Blood sera of VR26-immunized animals were found to contain VEE virus-specific antibodies. VR26-immunized mice and rabbits showed a high level of resistance to subcutane...
Equine infectious anemia. The ability of EIAV to persistently infect horses in the face of a profound immune response by the host makes it a potentially devastating disease for the horse population of the United States. Its ability to evade host immune defenses by lying dormant in apparently healthy animals and by rapidly changing its antigenic determinants is proving to be a major obstacle to vaccine development. Because most infected horses appear clinically normal and a large proportion of horses in this country remain untested, the virus is not likely to be eradicated in the near future. Yet, for the same reason, b...
Equine influenza. Influenza continues to be one of the most important diseases of horses despite the availability and widespread use of equine influenza vaccines for almost 30 years. In recent years, infection with the influenza A/equine/2 subtype has become endemic in the equine populations of North America, Europe, and Scandinavia. Continued antigenic drift of field virus has compromised the efficacy of vaccines, most of which contain antigens prepared from influenza viruses isolated more than 10 years ago. This article reviews the history, virology, epidemiology, pathogenesis, immunology, clinical presentati...
Equine influenza virus from the 1991 Swedish epizootic shows major genetic and antigenic divergence from the prototype virus. The antigenic properties of H3N8 equine influenza virus from the Swedish epizootic of 1991 differ from those of A/eq 2/Fontainebleau/79 (representative of the Swedish vaccine strain) in hemagglutination inhibition tests. The amino acid sequence of the hemagglutinin (HA) of an isolate from the 1991 outbreak was deduced from the nucleotide sequence and comparison was made to the A/eq 2/Fontainebleau/79 strain. Twenty-three amino acid substitutions were found, 10 mapping onto areas of the HA known to bind antibodies in human H3 influenza viruses. The amino acid changes together with the serologic...
Pathogenicity of a thymidine kinase-deficient mutant of equine herpesvirus 1 in mice and specific pathogen-free foals. Both intranasal (i.n.) and intracerebral (i.c.) inoculation of mice with wild-type equine herpesvirus type 1 (wt EHV-1) caused clinical signs and mortality. Virus could be recovered from target organs (turbinates, lungs and blood) for several days. By contrast, the thymidine kinase (TK)-deficient deletion mutant PR1 produced markedly less clinical disease following both i.n. and i.c. inoculation, and, in particular, no mortality occurred. PR1 did, however, establish productive infections following either route of inoculation. High titres of virus were recovered from target organs although viru...
[Equine influenza outbreaks with viral antigenic drift in Berlin 1988-1991]. In this paper three outbreaks of equine influenza in Berlin (Germany) in the years of 1988, 1989 and 1991 are discussed, reporting mainly clinical, hematological, virological and some epizootiological aspects. We have detected variations from the traditional pattern of equine influenza, whereby the main clinical symptoms like cough or fever were absent in several cases. If cough was found, it was moist. Furthermore a mucous nasal discharge was present in a number of cases for a period of 4-5 days. Extreme neutropenia, lymphocytosis and predominantly an unchanged level of monocytes were observe...
Recommendations for African horse sickness vaccines for use in nonendemic areas. African horse sickness (AHS), which causes mortality up to 95%, is caused by orbiviruses and is transmitted by Culicoides. The goal of a control and eradication program for AHS is to prevent the spread of the virus via the biological vector. Control measures include slaughter of infected animals, housing of suspected infected animals in insect-proof stalls, and vaccination. Vaccination has played a key role in eradication when AHS occurred outside of Africa. Both modified live vaccines (MLV) and inactivated vaccines have been used to control AHS. An acceptable vaccine should be: safe, efficaci...