Effects of Vaccination with the C-Strain Vaccine on Immune Cells and Cytokines of Pigs Against Classical Swine Fever Virus.

The attenuated C-strain vaccine against classical swine fever virus (CSFV) is one of the safest and most effective attenuated vaccines. However, little is known of the host immune response after vaccination with the C-strain vaccine. Blood samples from vaccinated pigs were collected to evaluate the number of immune cells, the level of specific CSFV antibody, and related cytokines induced by the vaccination of C-strain vaccine. The C-strain nucleic acid was gradually removed and specific antibody to vaccine kept increasing; the amount of the lymphocyte, Tc cell, and Th cell increased; some inflammatory cytokines such as interleukin (IL)-1 and tumor necrosis factor-α mainly showed downregulated trends, but IL-6 and IL-8 were upregulated greatly; IL-2, IL-4, IL-5, IL-12p40, IL-13, interferon (IFN)-I, and Toll-like receptors (TLRs) kept high expression level after 28 days postvaccination (dpv); IFN-γ was upregulated slightly at 5 and 9 dpv, respectively. These results suggest that the C-strain vaccine induces a Th2 cell response to produce the specific antibody. The vaccine virus replicates at very low level. C-strain vaccine burden has close relationship with the expression of TLRs. The overexpression of TLRs initiates the innate immune system to clear up the vaccine. Meanwhile, ILs expressed by immune system induce the differentiation of B cells and produce specific antibody.

Dynamic distribution and tissue tropism of classical swine fever virus in experimentally infected pigs.

BACKGROUND: Classical swine fever (CSF), caused by the Classical swine fever virus (CSFV), is an Office International des Epizooties (OIE) notifiable disease. However, we are far from fully understand the distribution, tissue tropism, pathogenesis, replication and excretion of CSFV in pigs. In this report, we investigated the dynamic distribution and tissue tropism of the virus in internal organs of the experimentally infected pigs using real-time RT-PCR and immunohistochemistry (IHC). RESULTS: A relative quantification real-time PCR was established and used to detect the virus load in internal organs of the experimentally infected pigs. The study revealed that the virus was detected in all 21 of the internal organs and blood collected from pigs at day 1 to day 8 post infections, and had an increasing virus load from day 1 to day 8 post infections. However, there was irregular distribution virus load in most internal organs over the first 2 days post infection. Blood, lymphoid tissue, pancreas and ileum usually contain the highest viral loads, while heart, duodenum and brain show relatively low viral loads. CONCLUSIONS: All the data suggest that CSFV had an increasing virus load from day 1 to day 8 post infections in experimentally infected pigs detected by real-time RT-PCR, which was in consistent with the result of the IHC staining. The data also show that CSFV was likely to reproduce in blood, lymphoid tissue, pancreas and the ileum, while unlikely to replicate in the heart, duodenum and brain. The results provide a foundation for further clarification of the pathogenic mechanism of CSFV in internal organs, and indicate that blood, lymphoid tissue, pancreas and ileum may be preferred sites of acute infection.

A novel RT-LAMP assay for rapid and simple detection of classical swine fever virus.

A simple and rapid assay for the detection of Classical swine fever virus (CSFV) was established using reverse transcription loop-mediated isothermal amplification (RT-LAMP). This study describes the amplification of the genomic RNA of CSFV under isothermal conditions (63 °C) within one hour, using a set of six primers (two outer primers, two inner primers and two loop primers). This RT-LAMP assay showed 100-fold higher sensitivity than the standard RT-PCR method and identified eighteen additional positive cases that were negative when tested by RT-PCR. This RT-LAMP was able to detect all the 13 strains of CSFV but not the BVDV. PRRSV. SIV. PRV-PCV, thus showed a good specificity. Products amplified by RT-LAMP can be visualized by agarose gel electrophoresis and in addition, either as a white precipitate at the bottom of the tube after a pulse spin or as a color change when dyed with SYBR Green I which are visible to the naked eye. Because RT-LAMP is low-cost and produces rapid results, it has the potential to be an excellent tool for CSFV surveillance in the field, especially in developing countries.