Immunity against NS3 protein of classical swine fever virus does not protect against lethal challenge infection

Classical swine fever is a highly contagious disease of swine caused by classical swine fever virus, an OIE list A pathogen. In the European Union the virus has been eradicated from the domestic pig population and prophylactic immunization has been banned. Nevertheless, intervention immunizations using marker vaccines are one possibility to deal with reintroduced CSFV. At present, baculovirus-expressed E2 protein is used as such a marker vaccine. However, this vaccine cannot fully protect against viral spread; hence the use of another subunit, or of a combination of two or more subunits, might be beneficial. Therefore the immunological effects of nonstructural protein 3 (NS3) on the humoral as well as the cellular arms of the immune system were investigated. Although effectors of both sides of the immune system were stimulated by application of recombinant NS3 protein, no protection against lethal CSFV challenge could be achieved.