Classical swine fever (CSF), an acute and highly contagious disease of swine, is caused by classical swine fever virus. CSF is one of the most devastating diseases to the pig industry worldwide and results in serious economic losses. Currently prophylactic vaccination is still an important strategy for the control of CSF. Live attenuated vaccines (such as C-strain) are safe and effective. However, there are significant changes in the clinical features of CSF, displaying concurrent typical and atypical CSF, and simultaneous inapparent and persistent infections. Immunization failure has been reported frequently and it is difficult to distinguish between wild-type infected and vaccinated animals (DIVA). So there is an urgent need to develop more effective and safer DIVA or marker vaccines for the control of CSF. In this review, some of the most recent advances in new-type vaccines against CSF, including DNA vaccines, live virus-vectored vaccines, protein or peptide-based vaccines, gene-deleted vaccines and chimeric pestivirus-based vaccines, are reviewed and discussed.
Animals ; Classical Swine Fever ; prevention & control ; Classical swine fever virus ; Swine ; Vaccination ; veterinary ; Vaccines, Attenuated ; immunology ; Vaccines, DNA ; immunology ; Vaccines, Subunit ; immunology ; Viral Vaccines ; immunology

Classical Swine Fever Virus (CSFV) E2 protein eukaryotic expression plasmid pVAXE2 was constructed. The plasmid pVAXE2 was transformed into Salmonella choleraesuis C500 (S. C500) attenuated vaccine strain by electroporation to generate Salmonella choleraesuis engineering strain S. C500/pVAXE2. The characterization of S. C500/pVAXE2 in morphology, growth, biochemistry and serology indicated that it retained the same properties as its original strain S. C500 with exception of kanamycin resistance originated from the plasmid pVAXE2. The plasmid stable in the bacteria after 15 passages. Kunming mice and rabbits were vaccinated three times at two weeks interval with S. C500/pVAXE2 in oral and intramuscular routes at the dosage of 1 x 10(8) CFU for mice and 2 x 10(9) CFU for rabbits each time. The specific antibody response against CSFV and Salmonella choleraesuis was detected by ELISA. Two weeks after the third boost the immunized rabbits were challenged with 20 ID50 of hog cholera lapinized virus (HCLV), followed by a virulent strain of Salmonella choleraesuis two week later than HCLV challenge. The results showed that all immunized mice and rabbits produced significant antibodies against CSFV and Salmonella choleraesuis, and the immunized rabbits demonstrated the effective protection against the challenge of HCLV and virulent Salmonella choleraesuis. These results indicated the potential of developing multiplex swine DNA vaccine by using this bacteria as the vector.
Animals ; Classical Swine Fever ; immunology ; prevention & control ; virology ; Classical swine fever virus ; genetics ; immunology ; Mice ; Rabbits ; Salmonella arizonae ; genetics ; Swine ; Vaccines, DNA ; immunology ; Viral Envelope Proteins ; biosynthesis ; genetics ; immunology ; Viral Vaccines ; immunology

In 1990, it was reported that the naked DNA encoding an antigen (so-called DNA vaccine) transduced directly into the muscle is able to induce immune responses just like antigen inoculation. Since then, a number of DNA vaccines against different diseases have been developed and shown to induce different levels of specific humoral and/or cell-mediated immunity. Efforts have been made to develop effective DNA vaccines against classical swine fever (CSF). This review covered the following aspects in the development and application of CSF DNA vaccines: construction and evaluation, application of adjuvants, combination with other vaccines and the existing problems and solutions.
Adjuvants, Immunologic ; pharmacology ; Animals ; Classical Swine Fever ; prevention & control ; Swine ; Vaccines, DNA ; biosynthesis ; immunology ; Viral Envelope Proteins ; genetics ; immunology ; Viral Vaccines ; biosynthesis ; immunology

We have shown previously that a Semliki Forest virus (SFV) replicon vectored DNA vaccine (pSFV1CS-E2) expressing the E2 glycoprotein of classical swine fever virus (CSFV) conferred full protection for pigs immunized three times with 600 microg of the vaccine. This study aims to evaluate the efficacy of the DNA vaccine with lower dosage and fewer inoculations. Pigs were immunized twice with 100 microg pSFV1CS-E2 (n = 5) or control plasmid pSFV1CS (n = 3), respectively. Pigs immunized with pSFV1CS-E2 developed high titers of specific neutralizing antibodies against CSFV after the booster, and the antibody titers increased rapidly upon challenge. The immunized animals showed no clinical symptoms except short-term fever and low-level viremia, whereas the control pigs immunized with the control plasmid produced no detectable antibody before challenge and showed obvious clinical signs following challenge, and 2 pigs died on 10 or 11 days post-challenge. All control animals developed extended viremia as detected by nested RT-PCR and real-time RT-PCR. Severe pathologic lesions typical of CSFV infection were observed at necropsy. We conclude that the alphavirus replicon-vectored DNA-based vaccine can be potential marker vaccine against CSFV.
Animals ; Antibodies, Neutralizing ; blood ; immunology ; Antibodies, Viral ; blood ; immunology ; Body Temperature ; immunology ; Classical Swine Fever ; blood ; immunology ; prevention & control ; Classical swine fever virus ; genetics ; immunology ; Genetic Vectors ; genetics ; Immunization ; Plasmids ; genetics ; Replicon ; genetics ; Reverse Transcriptase Polymerase Chain Reaction ; Semliki forest virus ; genetics ; Swine ; virology ; Time Factors ; Vaccines, DNA ; administration & dosage ; genetics ; immunology ; Viral Envelope Proteins ; genetics ; immunology ; Viremia ; genetics ; immunology

To determine the immune responses in pigs to hog cholera virus after treatment with an ionized alkali mineral complex (IAMC), 40 healthy pigs (28-32 days old) from a commercial swine farm were purchased and housed into 4 groups (n=10 each). All pigs were vaccinated intramuscularly (1 ml) with an attenuated live hog cholera virus (HCV, LOM strain) at 28-32 days old and challenged with a virulent hog cholera virus at 8 weeks after vaccination. Each group was treated with PowerFeelTM sprayed diet as 0.05% (w/w) in a final concentration (T-1, n=10), a diet mixed with SuperFeedTM as 3% (w/w) in a final concentration (T-2, n=10), or a diluted PowerFeelTM solution (1:500, v/v) as drinking water (T-3, n=10), respectively. A group (n=10) served as a non-treated control. Proportions of expressing CD2+ and CD8+ cells increased significantly (p<, 0.05) at 8-week post-application. Mean antibody titers of each group against HCV gradually increased to higher levels after vaccination and with challenge of the virulent virus. In conclusion, the IAMC-treated diets can be helpful for the improvement of growth in pigs with proper vaccination program, while the IAMC-treated diets have no effects on the clinical protection against hog cholera.
Alkalies/immunology/*pharmacology ; Animals ; Antibodies, Viral/blood ; Classical Swine Fever/*immunology/prevention & control ; Classical swine fever virus/*immunology ; Flow Cytometry/veterinary ; Fluorescent Antibody Technique, Indirect/veterinary ; HLA Antigens/immunology ; Minerals/immunology/*pharmacology ; Swine ; Vaccination/*veterinary ; Vaccines, Attenuated/immunology ; Viral Vaccines/*immunology

UNLABELLEDThe gene encoding classical swine fever virus (CSFV) T cell epitope E290 peptide was synthesized by PCR, cloned into the expression vector pPG-VP2 and named pPG-VP2-E290. The recombinant plasmid was electrotransformed into Lactobacillus casei 393 generating pPG-VP2-E290/L. casei 393. Specific anti-CSFV E290 peptide immunoglobulin G (IgG) antibody was detected by indirect ELISA in the serum of BALB/c mice and rabbits immunized with recombinant strain by oral administration. The CTL of E290 was analyzed with lymphocytes taken from the immunized mice, and the immunized rabbits were attacked with CSFV to validate the protective function of E290 antibody induced.

RESULTThe recombinant expression system constructed with L. casei 393 in this study show a good immunization property and could elicit the mice and rabbits to produce high anti-E290 antibody levels. Furthermore, E290 peptide antibody could elicit specific CTL response, and restrain attack of CSFV to rabbits.

Administration, Oral ; Animals ; Classical Swine Fever ; prevention & control ; Classical swine fever virus ; genetics ; immunology ; Epitopes, T-Lymphocyte ; biosynthesis ; genetics ; immunology ; Female ; Immunization ; methods ; Lactobacillus casei ; genetics ; immunology ; metabolism ; Male ; Mice ; Mice, Inbred BALB C ; Protein Engineering ; Rabbits ; Recombinant Proteins ; biosynthesis ; genetics ; Swine ; T-Lymphocytes, Cytotoxic ; immunology ; Vaccines, Synthetic ; immunology ; Viral Envelope Proteins ; biosynthesis ; genetics ; immunology ; Viral Vaccines ; immunology

We have previously evaluated a Semliki Forest virus (SFV) replicon vectored DNA vaccine (pSFV1CS2-E2) and a recombinant adenovirus (rAdV-E2) expressing the E2 glycoprotein of classical swine fever virus (CSFV) in pigs. The results showed that the immunized pigs were protected from virulent challenge, but few pigs showed short-term fever and occasional pathological changes following virulent challenge. To enhance the immunogenecity of the vaccines, we tried a prime-boost vaccination strategy using a combination of prime with pSFV1CS2-E2 followed by boost with rAdV-E2. The results showed that all the immunized pigs developed high-level CSFV-specific antibodies following prime-boost immunization. When challenged with virulent CSFV, the immunized pigs (n = 5) from the heterologous boost group showed no clinical symptoms, and CSFV RNA was not detected following challenge, whereas one of five pigs from the homologous boost group developed short-term fever and CSFV RNA was detected. This demonstrates that the heterologous prime-boost vaccination regime has the potential to prevent against virulent challenge.
Adenoviridae ; genetics ; metabolism ; Adenovirus E2 Proteins ; genetics ; immunology ; Animals ; Classical Swine Fever ; immunology ; prevention & control ; Classical swine fever virus ; genetics ; immunology ; Genetic Vectors ; Immunization, Secondary ; Replicon ; genetics ; Semliki forest virus ; genetics ; metabolism ; Swine ; Vaccines, DNA ; immunology ; Viral Envelope Proteins ; genetics ; metabolism ; Viral Vaccines ; immunology