Recombinant viruses expressing the foot-and-mouth disease virus capsid precursor polypeptide (P1) induce cellular but not humoral antiviral immunity and partial protection in pigs

Genetic stability of attenuated mengovirus vectors with duplicate primary cleavage sequences

Short poly(C)-tract Mengoviruses have proven vaccine efficacy in many species of animals. A novel vector for the delivery of foreign proteins was created by insertion of a second autoproteolytic primary cleavage cassette linked to a multiple cloning site (MCS) into an attenuated variant of Mengo. Nineteen cDNAs from foreign sequences that ranged from 39 to 1653 bases were cloned into the MCS. The viral reading frame was maintained and translation resulted in dual, autocatalytic excision of the foreign peptides without disruption of any Mengo proteins. All cDNAs except those with the largest insertions produced viable virus. Active proteins such as GFP, CAT, and SIV p27 were expressed within infected cells. Relative to parental Mengo, the growth kinetics and genetic stability of each vector was inversely proportional to the size of the inserted sequence. While segments up to 1000 bases could be carried, inserts greater than 500-600 bases were usually reduced in size during serial passage. The limit on carrying capacity was probably due to difficulties in virion assembly or particle stability. Yet for inserts less than 500-600 bases, the Mengo vectors provided an effective system for the delivery of foreign epitopes into cells and mice.

Adenovirus-Mediated Type I Interferon Expression Delays and Reduces Disease Signs in Cattle Challenged with Foot-and-Mouth Disease Virus

Foot-and-mouth disease (FMD) is an economically important disease of livestock. Eliminating FMD outbreaks in previously disease-free countries often relies on restriction of animal movement and massive slaughter of infected and in-contact susceptible animals. To develop a more effective and humane FMD control strategy, we explored the possibility of using type I interferon (IFN-alpha/beta) as a novel anti-FMD agent. We have demonstrated previously that swine inoculated with replication-defective human adenovirus type 5 (Ad5) vector expressing porcine IFN-alpha (Ad5-PoIFN-alpha) were completely protected from FMD virus (FMDV) challenge. To extend this approach to bovines, we constructed Ad5 vectors that express bovine IFN-alpha or IFN-beta (Ad5-BoIFN-alpha and Ad5-BoIFN-beta). Cells infected with these viruses produced high levels of biologically active BoIFN-alpha/beta, but despite expression in vitro, no detectable IFN-induced biologic activity was found in cattle inoculated with Ad5-BoIFN-alpha. Because PoIFN-alpha inhibits FMDV replication in bovine cells, we evaluated the potential use of PoIFN-alpha against FMD in cattle. In cattle inoculated with Ad5-PoIFN-alpha, the appearance of vesicles was delayed after challenge with FMDV and disease was less severe than in control animals. One Ad5-PoIFN-alpha-inoculated animal never developed clinical disease. Similarly, although all the Ad5-PoIFN-alpha-inoculated animals developed viremia, it was delayed for 1 day as compared with the control group. These results suggest that in vivo expression of PoIFN-alpha partially protected cattle from FMD.

Recombinant adenovirus co-expressing capsid proteins of two serotypes of foot-and-mouth disease virus (FMDV): in vitro characterization and induction of neutralizing antibodies against FMDV in swine

Human adenovirus type 5 (Ad5) has been evaluated as a novel gene delivery vector for the development of live-viral vaccines for foot-and-mouth disease (FMD). In this study, we constructed an Ad5 vector co-expressing the capsid precursor proteins, P1, of FMD virus (FMDV) field strains A24 Cruzeiro and O1 Campos and examined the neutralizing antibody responses in swine after inoculation with the vector. To construct the Ad5 vector, a bicistronic expression cassette containing a cytomegalovirus promoter, the P1 coding sequence of FMDV A24, the internal ribosomal entry site (IRES) of FMDV A12, the P1 coding sequence of FMDV O1 Campos and the coding region of A12 3C protease was inserted into the E1 region of an E1/E3-deleted Ad5. The recombinant adenovirus, Ad5A24+O1, was generated by transfection of 293 cells with full-length pAd5A24+O1 recombinant plasmid DNA. The recombinant Ad5 co-expressed P1 of both A24 and O1 in infected 293 cells and P1 of both serotypes was processed to produce VP0, VP3, and VP1. We further demonstrated the formation of capsid protein complexes by co-precipitation of VP0, VP3, and VP1 with monoclonal antibodies against viral capsid proteins. Swine inoculated with Ad5A24+O1 generated neutralizing antibodies against both A24 and O1. However, the overall neutralizing antibody response was considerably lower than that induced by a commercial FMD vaccine or a monovalent Ad5-A24 vaccine.

Foot-and-mouth disease virus: biology and prospects for disease control

Foot-and-mouth disease virus (FMDV) is the causative agent of a disease that constitutes one of the main animal health concerns, as evidenced by the devastating outbreaks that occurred in different areas of the world over the last few years. In this review, we summarise important features of FMDV, aspects of its interactions with cells and hosts as well as current and new strategies for FMD control by vaccination.

Antigenic sites of foot-and-mouth disease virus (FMDV): an analysis of the specificities of anti-FMDV antibodies after vaccination of naturally susceptible host species

Of the known neutralizing antigenic sites of foot-and-mouth disease virus (FMDV), site 1 or A, formed in part by the G-H loop of VP1, has historically been considered immunodominant because of evidence implicating its importance in the induction of a protective immune response. However, no systematic study has been done to determine the relative importance of the various specificities of antibodies against the known neutralizing antigenic sites of FMDV in the polyclonal immune response of a natural host after vaccination. In this report, we have adopted a monoclonal antibody-based competition ELISA and used antibodies specific to sites 1, 2 and 3 to provide some insight into this issue. Following vaccination of the three main target species, cattle, pigs and sheep, with an O1 serotype strain, results indicate that none of these three antigenic sites can be considered immunodominant in a polyclonal serum. Interestingly, pigs did not respond to epitopes on the carboxy terminus end of VP1 as efficiently as the ruminant species. In addition to the known sites, other as yet undefined sites might also be important in the induction of a protective immune response. Possible implications for the design of new vaccine strategies for foot-and-mouth disease are discussed.

Early protection against homologous challenge after a single dose of replication-defective human adenovirus type 5 expressing capsid proteins of foot-and-mouth disease virus (FMDV) strain A24

Previously we demonstrated that two doses of a replication-defective human adenovirus serotype 5 (Ad5) carrying the capsid (P1) and 3C protease coding regions of a laboratory strain of FMDV (A12) completely protected five of six swine challenged with homologous virus. The objective of the current study was to evaluate the efficacy of one dose of an Ad5-vectored vaccine expressing the P1 coding region of an FMDV field strain. A replication-defective Ad5 containing the P1 coding region of FMDV A24 and the 3C coding region of A12 (Ad5A24) was constructed and evaluated for its ability to induce neutralizing antibodies and protect swine against homologous challenge after a single vaccination. Animals were challenged 7, 14 or 42 days after vaccination. Control groups included animals inoculated with commercial vaccine or phosphate-buffered saline. All vaccinated swine were completely protected against homologous challenge at 7, 14 or 42 days after vaccination. Based on these results, we conclude that a single inoculation of Ad5-vectored vaccines could be used as a tool to control FMD in outbreak situations.

Gene gun-mediate DNA vaccination against foot-and-mouth disease virus

Foot-and-mouth disease (FMD) is one of the most dangerous diseases of cloven-hoofed animals and is a constant threat in the Middle-East and other regions throughout the world despite intensive vaccination programs. In this work, we describe the ability of FMDV expression constructs to protect pigs from FMDV challenge when used as a vaccine. The construct consists of encephalomyocarditis virus (EMCV) internal ribosome entry site (IRES), the entire P1 and 2A together with 3CD sequences, all in the same reading frame. Another plasmid that was tested, carries the serotype O1 (G) VP1, Asia1 VP1 and O1 (G) 3C. Between each of the genes the 3C cleavage sequences were inserted. All constructs carried the cytomegalo virus (CMV) promoter. Using immunofluorescent and immunoblot techniques, we could show the expression and processing of viral proteins. Following the application of FMDV expression constructs into pigs skin by 'Gene Gun', pigs were partially protected from FMDV challenge.

Identification of T-cell epitopes in nonstructural proteins of foot-and-mouth disease virus

Porcine T-cell recognition of foot-and-mouth disease virus (FMDV) nonstructural proteins (NSP) was tested using in vitro lymphoproliferative responses. Lymphocytes were obtained from outbred pigs experimentally infected with FMDV. Of the different NSP, polypeptides 3A, 3B, and 3C gave the highest stimulations in the in vitro assays. The use of overlapping synthetic peptides allowed the identification of amino acid regions within these proteins that were efficiently recognized by the lymphocytes. The sequences of some of these antigenic peptides were highly conserved among different FMDV serotypes. They elicited major histocompatibility complex-restricted responses with lymphocytes from pigs infected with either a type C virus or reinfected with a heterologous FMDV. A tandem peptide containing the T-cell peptide 3A[21-35] and the B-cell antigenic site VP1[137-156] also efficiently stimulated lymphocytes from infected animals in vitro. Furthermore, this tandem peptide elicited significant levels of serotype-specific antiviral activity, a result consistent with the induction of anti-FMDV antibodies. Thus, inclusion in the peptide formulation of a T-cell epitope derived from the NSP 3A possessing the capacity to induce T helper activity can allow cooperative induction of anti-FMDV antibodies by B cells.

Immune responses and protection against foot-and-mouth disease virus (FMDV) challenge in swine vaccinated with adenovirus-FMDV constructs

A replication-defective adenovirus 5 encoding foot-and-mouth disease virus (FMDV) capsid and 3C proteinase coding regions (Ad5-FMDV3CWT) was used to vaccinate swine. A single inoculation utilizing 1 x 10(8) plaque forming units (pfu) or an inoculation of 1 x 10(8) followed by a boost of 5 x 10(8) pfu Ad5-FMDV3CWT were tested, along with an inoculation and boost using an adenovirus encoding the FMDV capsid coding region and an inactive form of the 3C proteinase (Ad5-FMDV3CMUT). Sera collected from these animals were examined for the presence of FMDV-specific antibodies using immunoprecipitation, neutralization, and ELISA assays specific for IgM, IgG1 and IgG2. Efficacy studies were performed by placing the vaccinated swine in contact with an FMDV-infected swine and monitoring for signs of disease and changes in serum antibody levels. Ad5-FMDV3CMUT, which is unable to produce FMDV capsid structures, did not elicit FMDV-neutralizing antibodies or protect against FMD. Single inoculation with Ad5-FMDV3CWT generated FMDV-specific neutralizing antibodies, and reduced clinical signs in challenged swine, but failed to completely protect the majority of swine from FMD. Swine which received a primary vaccination with Ad5-FMDV3CWT followed by the boost at 4 weeks generated high levels of FMDV-neutralizing antibodies resulting in complete protection of five of the six swine and limited disease in the remaining animal. Increased efficacy of the two-dose regimen was associated with heightened levels of FMDV-specific IgG1 and IgG2 antibodies.