Novel Vaccine Technologies in Veterinary Medicine: A Herald to Human Medicine Vaccines

Abstract

The success of inactivated and live-attenuated vaccines has enhanced livestock productivity, promoted food security, and attenuated the morbidity and mortality of several human, animal, and zoonotic diseases. However, these traditional vaccine technologies are not without fault. The efficacy of inactivated vaccines can be suboptimal with particular pathogens and safety concerns arise with live-attenuated vaccines. Additionally, the rate of emerging infectious diseases continues to increase and with that the need to quickly deploy new vaccines. Unfortunately, first generation vaccines are not conducive to such urgencies. Within the last three decades, veterinary medicine has spearheaded the advancement in novel vaccine development to circumvent several of the flaws associated with classical vaccines. These third generation vaccines, including DNA, RNA and recombinant viral-vector vaccines, induce both humoral and cellular immune response, are economically manufactured, safe to use, and can be utilized to differentiate infected from vaccinated animals. The present article offers a review of commercially available novel vaccine technologies currently utilized in companion animal, food animal, and wildlife disease control.

Keywords: companion animals; disease control and prevention; food animals; infectious diseases; new technology vaccines; veterinary vaccines.

Figure 1

Six novel vaccine technologies discussed in this review are simplified and summarized starting from the generation and production of antigens to the vaccination. Beginning with plasmid-DNA vaccines, the target antigen is inserted into a plasmid. This serves as the active ingredient that will be used to vaccinate the animal. Upon vaccination, the plasmid-DNA vaccine carrying the DNA encoding for the target antigen is translated into the desired protein in the vaccine recipient's cells. The antigen is then expressed from the cell, consequently eliciting an immune response. Recombinant protein vaccines and chimeric protein vaccines utilize a similar technology. However, suitable cell-lines are transfected with the plasmid in which the antigen(s) is/are expressed. The antigen(s) is/are then harvested, purified, and formulated into the vaccine. Chimeric viral vaccines utilize a plasmid containing the whole genome of a virus that will be used as a vector in addition to the target gene for the desired antigen. This plasmid is then used to transfect a suitable cell-line in which a whole virus expressing the integrated antigen is produced. This virus is harvested and purified, and formulated into a vaccine. Viral vectors utilize a virus that has been engineered to express the gene of interest. The virus is formulated into a vaccine and will release the recombinant genes into the host cells. Similar to a plasmid-DNA vaccine, the genes will be transcribed into the target antigen which will then be expressed and elicit an immune response. RNA replicon vaccines utilize a RNA segment that encodes the desired antigens encapsulated in a vesicle carrier. Once in the host's cell, the RNA is directly translated, resulting in the expression of the target antigen.