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Three forms of E2 recombinant protein were expressed in E. coli . Swine sera obtained against different forms of the recombinant protein were cross-studied with indirect ELISA. Using individual proteins as an antigen, only 15% of sera against other forms of protein reacted positively, while 100% of heterologous sera showed positive reaction with fused protein. Challenge experiments showed the existence of protective action only from the individual protein. Specificity and activity of sera obtained from the animals after control challenge was confirmed in a blocking variant of ELISA. Genetic construction used a eukaryotic vector that contained the E2 protein gene. Immunization of mice with the resulting DNA induced synthesis of specific antibodies, the titre of which increased considerably after additional single immunization with the E2 recombinant protein, expressed in E. coli . This demonstrated the effectiveness of animal priming by DNA vaccine, and the possibility of using the E2 recombinant protein in E. coli for booster vaccination.

Two Indian PPRV isolates were subjected to thermal hardening procedures to increase the proportion of temperature-resistant virions. Initial infectivity loss was compensated by titre increases on subsequent cell passages at 37°C. The immunogenicity of ‘thermostable’ viruses was assessed by virulent PPRV challenge and for safety by host animal inoculation and antibodies assessment. Vaccine viruses were not found using PCR on ocular and nasal swabs, although virus nucleic acid and antigens were demonstrated in spleen and lymph nodes by FAT and PCR. One vaccine strain (MIB187(T)) giving 100% protection (tested on only a few animals) was freeze dried and the minimum protective dose calculated. Changes in the virus genome after thermo-adaptation were examined using RT-PCR to amplify portions of the F gene, and three base changes were observed in the thermostable PPR strain (compared with the F gene sequence of the Nigerian PPRV strain). At room temperature, the titre and potency of the thermo-adapted vaccine remained constant up to one month at the 10^5.5 TCID_50 level, and was 10^4.5 TCID_50/100 μl after two months. Field trials with over 40 000 doses of the thermostable vaccine under various environmental conditions have given serum neutralization titres exceeding 2^3 and are assumed protective.

Full-length cDNA of both genome segments of a Bangladeshi strain of very virulent infectious bursal disease virus (BD 3/99) were cloned in plasmid vectors along with the T7 promoter tagged to the 5′-ends. Mutations were introduced in the cloned cDNA to bring about two amino acid exchanges (Q253H and A284T) in the capsid protein VP2. Transfection of primary chicken embryo fibroblast cells with RNA transcribed in vitro from the full-length cDNA resulted in the formation of mutant infectious virus particles that grow in tissue culture. The pathogenicity of this molecularly-cloned, tissue-culture-adapted virus (BD-3tc) was tested in commercial chickens. The parental wild-type strain, BD 3/99, was included for comparison. The subclinical course of the disease and delayed bursal atrophy in BD-3tc-inoculated birds suggested that these amino acid substitutions made BD-3tc partially attenuated.

Post-genomic approaches in the development of new vaccines will fundamentally change how veterinarians prevent and treat diseases. One type of vaccine that has generated renewed interest is the subunit or synthetic vaccine, which has the advantage of rapid, safe and high-throughput production via chemical (as synthetic peptides) or recombinant approaches (as DNA, purified subunit or multigene vaccines). At the heart of such a vaccine are few but powerful epitopes that confer both the humoral and cell-mediated immune responses. Traditional biochemical assays have been used to map these epitopes; however, they are prohibitively labour and capital intensive. In contrast, in silico development of multivalent subunit vaccines is now possible through the availability of genomic information and the nascence of molecular immunoinformatics as a discipline. Algorithms are described in this paper to aid in identifying B and T cell epitopes for design of vaccines based on published available protein databases. From the mapped epitopes, synthetic mimotopes (or epitope-mimicking sequences) are concatenated using glycine bridges aimed at maintaining at least 90% of the secondary structures while minimizing steric hindrances between adjacent epitopes.

The use of nuclear methods can enhance several features of DNA vaccines in protecting livestock against pathogens. While DNA vaccines already have several advantages over their traditional predecessors (e.g. cheap production, stability over a wide range of temperature, amenability to genetic manipulation, and no risk of reversion to pathogenicity), conventional gene delivery systems make immunization of livestock and aquaculture populations tedious. For this reason, we are developing radiation-synthesized intelligent delivery systems for DNA vaccines. We encapsulated a reporter construct pCMV•SPORT-β-gal in radiation-synthesized κ-carrageenan-polyvinylpyr-rolidone microspheres IP20 (for stomach release) and IP18 (for intestinal release). The DNA-loaded polymers were orally administered to Oreochromis niloticus (black Nile tilapia), and whole organs were stained with X-gal to observe β-galactosidase activity. Intense staining was observed in the stomach regions with IP20, while minimal staining was observed with IP18. The gills, in contrast, did not express β-galactosidase activity. Our results show evidence of the successful gene delivery capabilities of radiation-synthesized microspheres.

With the aim of achieving a better understanding of the epidemiology of Bovine leukaemia virus (BLV) infection, we investigated the suitability of milk tank samples for effecting molecular epidemiology studies of BLV in a southern area of Chile. As part of a serological survey for BLV antibodies carried out in 280 herds, we selected 33 strong positive samples, from which DNA was isolated to perform a BLV-specific nested PCR. Using RFLP analysis, all 33 PCR products could be assigned to the known Australian or the Belgium subgroups. A phylogenetic tree resulting from the comparison of these sequences demonstrates the relations and differences among and within the subgroups.

The buffalo is probably the last livestock species to have been domesticated, with many genetic, physiological and behavioural traits not yet well understood. Molecular markers have been used for characterizing animals and breeds, diagnosing diseases and identifying anatomical and physiological anomalies. RFLP studies showed low heterozygosity, but genomic and oligonucleotide probes showed species-specific bands useful for identification of carcass or other unknown samples. Use of RAPD revealed band frequencies, band sharing frequencies, genetic distances, and genetic and identity indexes in different breeds. Bovine microsatellite primers indicate that 70.9% of bovine loci were conserved in buffalo. Allele numbers, sizes, frequencies, heterozygosity and polymorphism information content showed breed-specific patterns. Different marker types - genomic and oligonucleotide probes, RAPD and microsatellites - are useful in parent identification. Individual specific DNA fingerprinting techniques were applied with twinborn animal (XX/XY) chimerism, sex identification, anatomically defective and XO individuals. Molecular markers are a potential tool for geneticists and breeders to evaluate existing germplasm and to manipulate it to develop character-specific strains and to provide the basis for effective genetic conservation.

Because of their close relationship, specific identification of the CaPVs genus inside the Poxviridae family relies mainly on molecular tools rather than on classical serology. We describe the suitability of the G protein-coupled chemokine receptor (GPCR), for host range phylogenetic grouping. The analysis of 26 CaPVs shows 3 tight genetic clusters consisting of goatpox virus (GPV), lumpy skin disease virus (LSDV), and sheeppox virus (SPV).

Rapid identification and differentiation of camel pox (CMP) and camel contagious ecthyma (CCE) were achieved by polymerase chain reaction (PCR) with primers that distinguish Orthopoxvirus (OPV) and Parapovirus (PPV). Forty scab specimens collected from sick camels and sheep were treated by 3 different DNA extraction procedures and examined by PCR. The sensitivity of the PCR was compared with that of electron microscopy and virus isolation in cell culture. Procedure 1, in which viral DNA was extracted directly from scab specimens followed by PCR, proved to be superior and more sensitive. Procedure 2 enables a fast specific diagnosis of PPV and OPV infections directly from scab materials without the need for DNA extraction. These assays provide a rapid and feasible alternative to electron microscopy and virus isolation.

Brucella abortus S19 is the most commonly used attenuated live vaccine to prevent bovine brucellosis. In spite of its advantages, S19 has several drawbacks: it is abortive for pregnant cattle, is virulent for humans, and revaccination is not advised due to the persistence of anti-lipopolysaccharide (LPS) antibodies that hamper the immunoscreening procedures. For these reasons, there is a continuous search for new bovine vaccine candidates. We have previously characterized the phenotype of the phosphoglucomutase ( pgm ) gene disruption in Brucella abortus S2308, as well as the possible role for the smooth LPS in virulence and intracellular multiplication. Here we evaluate the vaccine properties of an unmarked deletion mutant of pgm . Western blot analysis of purified lipopolysaccharide and whole-cell extract from Δ pgm indicate that it synthesizes O-antigen but is incapable of assembling a complete LPS. In consequence Δ pgm has a rough phenotype. Experimental infections of mice indicate that Δ pgm is avirulent. Vaccination with Δ pgm induces protection levels comparable to those induced by S19, and generates a splenocyte proliferative response and cytokines profile typical of a Th-1 response. The ability of the mutant to generate a strong cellular Th-1 response without eliciting specific O-antigen antibodies highlights the potential use of this mutant as a new live vaccine for cattle.