Vaccination in its unique notion, aims to mimic the development of naturally acquired immunity by inoculation of nonpathogenic but still immunogenic components of the pathogen in question, or closely related organisms. Conventional vaccines can be of live attenuated organisms or whole inactivated pathogens and/or some bacterial toxins. But each one of these has their own limitations by virtue of being less safe, cost and batch to batch variation. As a result of these lacunae, several modern approaches emerged in the arena of vaccine development like recombinant protein based vaccine and plasmid DNA vaccine. But the problem of less immunogenicity brings the concept of adjuvant and their selection in to the context of effective vaccination. The criteria for successful animal or veterinary vaccines are very different from those for human vaccines in the selection and use of adjutants. Moreover, selection of adjutants for vaccine has been relied on type of vaccine, safety, mode of action, level of toxicity, adjuvanticity and reliability. Conventional adjutants such as Freund complete (FCA) or incomplete adjuvant (IFA) and Alum are the classic adjutants to which most others are compared, but their reactogenicity precludes clinical use in animals or humans. The recent advances in immunology and biotechnology have generated new perspectives for development of novel adjutants. Several recent issues like emergence of new diseases, re-emergence of ‘old’ infections and changing pattern of many viral diseases have urged the need for the development of new and improved vaccines for veterinary applications. These new generation vaccines, particularly those based on recombinant proteins and DNA, are likely to be less reactogenic than traditional ones, but are also less immunogenic. Therefore, there is an urgent need for the development of new and improved vaccine novel adjutants. There is an intensive research in search of modern immune adjuvants to cope with these modern vaccines. In recent past years, several adjuvants have been appeared in scientific literatures and have potential to mimic immune response against large spectrum of antigens with mimimal or no reactivity in recipient host. These novel types of immune adjuvants are of immunostimulatory molecules (several inbuilt or exogenous cytokines and CpG oligonucleotide motifs), targeted delivery systems (mucosal adjuvants, carbohydrate biopolymers and bacterial ghosts) and several mixed oil formulations (montanides preparations). Recently, the innate biosensor molecules called as Toll-like-receptors (TLRs) particularly TLR 2, 4, 7 and 8 ligands found to have potential adjuvant effects when administered prior or along with antigens. However, these new and improved adjuvants are to be further defined for their mechanism of action at molecular level so as to develop potent vaccine against some infectious disease like HIV which usually confers less protective immunity naturally. In addition, economics of immunization are particularly important while attempting for new veterinary vaccine adjuvant development.
