Studies on the tissue culture of hog cholera virus. II. Neutralization test by means of the influence of hog cholera virus infection on newcastle disease virus infection (HEIC method)

A Critical Review about Different Vaccines against Classical Swine Fever Virus and Their Repercussions in Endemic Regions

Classical swine fever (CSF) is, without any doubt, one of the most devasting viral infectious diseases affecting the members of Suidae family, which causes a severe impact on the global economy. The reemergence of CSF virus (CSFV) in several countries in America, Asia, and sporadic outbreaks in Europe, sheds light about the serious concern that a potential global reemergence of this disease represents. The negative aspects related with the application of mass stamping out policies, including elevated costs and ethical issues, point out vaccination as the main control measure against future outbreaks. Hence, it is imperative for the scientific community to continue with the active investigations for more effective vaccines against CSFV. The current review pursues to gather all the available information about the vaccines in use or under developing stages against CSFV. From the perspective concerning the evolutionary viral process, this review also discusses the current problematic in CSF-endemic countries.

Establishment and characterization of an infectious cDNA clone of a classical swine fever virus LOM strain

Classical swine fever virus (CSFV) causes a highly contagious disease among swine that has an important economic impact worldwide. CSFV strain LOM is an attenuated virus of low virulent strain of Miyagi isolated from Japan in 1956. Eight DNA fragments representing the genome of the CSFV strain LOM were obtained by RT-PCR. These were used to determine the complete nucleotide sequence and construct a full-length cDNA clone which was called Flc-LOM. Sequence analysis of the recombinant clone (Flc-LOM) revealed the presence of eight mutations, resulting in two amino acid substitutions, when compared to the parental sequence. RNA transcripts of both LOM and Flc-LOM were directly infectious in PK-15 cells. The rescued Flc-LOM virus grew more slowly than the parental virus, LOM, in the cells. Intramuscular immunization with Flc-LOM was safe and highly immunogenic in pigs; no clinical signs or virus transmission to sentinel animals were observed after 35 days. CSFV-specific neutralizing antibodies were detected 14 days post-infection. After challenge with the virulent CSFV strain SW03, pigs immunized with Flc-LOM were shown to be fully protected. Thus, our newly established infectious clone of CSFV, Flc-LOM, could serve as a vaccine candidate.

Methods to select suitable fetal bovine serum for use in quality control assays for the detection of adventitious viruses from biological products

Production of biological products, especially vaccines, usually requires materials derived from animals, and there are always risks that animal pathogens derived from these materials could contaminate the final products. Detection of adventitious agents is performed by quality control tests. In these biological assays, animal derived materials are also used and another problem arises, as fetal bovine serum (FBS) is used as an ingredient in tissue culture media. FBS contaminated with bovine viral diarrhea virus (BVDV) or other bovine pathogens, as well as antibodies against these pathogens may lead to false results in quality control assays. In this study, in order to determine the actual status of commercial FBS, we performed quality tests on various FBS samples. As a result, in 28 of 49 FBS samples (57.1%), pestivirus genes were detected by pan-pestivirus reverse transcription-polymerase chain reaction assay. Furthermore, two samples contained infectious BVDV. Neutralizing antibodies against BVDVs were detected in 48 of 49 samples (97.6%) by the virus neutralization test based on the serum-dilution or virus-dilution methods. Antibodies against other bovine pathogens were detected rarely in these samples. From our results, we recommend methods to select FBS that are focused on detection of BVDV and neutralizing antibodies against BVDV.