Research Progress and Challenges in Vaccine Development against Classical Swine Fever Virus

Classical swine fever (CSF), caused by CSF virus (CSFV), is one of the most devastating viral epizootic diseases of swine in many countries. To control the disease, highly efficacious and safe live attenuated vaccines have been used for decades. However, the main drawback of these conventional vaccines is the lack of differentiability of infected from vaccinated animals (DIVA concept). Advances in biotechnology and our detailed knowledge of multiple basic science disciplines have facilitated the development of effective and safer DIVA vaccines to control CSF. To date, two types of DIVA vaccines have been developed commercially, including the subunit vaccines based on CSFV envelope glycoprotein E2 and chimeric pestivirus vaccines based on infectious cDNA clones of CSFV or bovine viral diarrhea virus (BVDV). Although inoculation of these vaccines successfully induces solid immunity against CSFV, none of them could ideally meet all demands regarding to safety, efficacy, DIVA potential, and marketability. Due to the limitations of the available choices, researchers are still striving towards the development of more advanced DIVA vaccines against CSF. This review summarizes the present status of candidate CSFV vaccines that have been developed. The strategies and approaches revealed here may also be helpful for the development of new-generation vaccines against other diseases.