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In the present study, an allele-specific primer-polymerase chain reaction (ASP-PCR) for genotyping a single nucleotide polymorphism (SNP) of swine Toll-like receptor 5 (TLR5) (C1205T; P402L) that is related to the impaired recognition of Salmonella enterica serovar Choleraesuis (SC) was developed. The allele frequencies in several pig breeds in Japan and the Czech Republic were also compared. The swine TLR5 C1205T mutation was successfully determined by ASP-PCR using genomic DNA samples in Japan that had previously been genotyped by a sequencing method. Using the PCR condition determined, genomic DNA samples from blood obtained from 110 pigs from seven different breeds in the Czech Republic were genotyped by the ASP-PCR. The genotyping results from the ASP-PCR completely matched the results from the sequencing method. The allele frequency of the swine TLR5 C1205T mutation was 27.5% in the Landrace breed of the Czech Republic compared with 50.0% in Japanese Landrace. In Japan, the C1205T mutation was found only in the Landrace breed, whereas in the Czech Republic it was found in both the Landrace and Piétrain breeds. These results indicate the usefulness of ASP-PCR for detecting a specific SNP for swine TLR5 affecting ligand recognition. They also suggest the possibility of genetically improving pigs to enhance their resistance against SC infection by eliminating or selecting this specific SNP of swine TLR5., (© 2012 The Societies and Blackwell Publishing Asia Pty Ltd.)

In the present study, we have developed an allele-specific primer-polymerase chain reaction (ASP-PCR) for genotyping a single nucleotide polymorphism (SNP) of swine Toll-like receptor 2 (TLR2) (C406G), which is related to the prevalence of pneumonia caused by Mycoplasma hyopneumoniae. We also compared the allele frequency among several pig breeds of Japan and the Czech Republic. Allele-specific primers were constructed by introducing 1-base mismatch sequence before the SNP site. The swine TLR2 C406G mutation was successfully determined by the ASP-PCR using genomic DNA samples in Japan as previously genotyped by a sequencing method. Using the PCR condition determined, genomic DNA samples from pig blood obtained from 110 pigs from 7 different breeds in the Czech Republic were genotyped by the ASP-PCR. The genotyping results from the ASP-PCR were completely matched with the results from the sequencing method. The allele frequency of the swine TLR2 C406G mutation was 27.5% in the Czech Republic and 3.6% in Japan. The C406G mutation was only found in the Landrace breed in Japan, and was almost exclusively found in the Landrace breed in the Czech Republic as well. These results indicated the usefulness of ASP-PCR for detecting a specific SNP for swine TLR2.

Toll-like receptor 4 (TLR4) responds to lipid A, the active moiety of lipopolysaccharide from gram-negative bacteria, in cooperation with myeloid differentiation protein-2 and plays a vital role in innate immunity. Polymorphisms in TLR4 are associated with changes in susceptibility to various infectious diseases. We previously found seven amino acid polymorphisms in Sus scrofa TLR4. In this study, we showed by luciferase reporter assay that an alteration from cysteine to tryptophan at position 506 (C506W) caused loss of ability to induce nuclear factor-κB activation after lipid A stimulation. This polymorphism was found only in Japanese wild boar (JWB) populations of S. scrofa. Genotyping of TLR4 in different JWB populations revealed that C506W polymorphism was under pressure from purifying selection in a local population (Tajima's D=-0.98; p<0.05). However, in another population, this polymorphism existed at a frequency such that homozygous animals with the W506 alleles seldom appeared. These findings suggest that the C506W polymorphism is under different types of pressure by natural selection between populations, which may reflect differences in residential pathogens or demographic factors.

In the present study, group-specific antigen VP7 of bluetongue virus (BTV) serotype 21 isolated from cattle in Tochigi prefecture in Japan in 1994 was characterized by sequencing and expression. Gene was amplified from cDNA synthesized on viral dsRNA using reverse-transcriptase-PCR. Nucleotide sequence of this isolate showed high similarity with other published BTV VP7 sequences. Full-length and C-terminal truncated forms of VP7 were expressed in insect cells by a baculovirus gene expression system under control of the viral polyhedrin promoter. Expression of full-length recombinant VP7 was confirmed by immunoprecipitation with VP7 specific monoclonal antibody (8A3B.6, ATCC). Recombinant proteins expressed with or without 6x His-tag showed good expression levels in TN5 cells and reacted well with the monoclonal antibody in the indirect ELISA. However C-terminal truncated VP7 with His-tag failed to react with this monoclonal antibody, while poor antigenicity was evident when it was reacted with infected bovine serum. Reduced antigenicity of the latter suggested that C-terminal truncation affects 8A3B.6 epitope construction probably via inhibition of VP7 trimer structure formation.