The Challenge of Parasite Control
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2015
Besides being safer, inactivated vaccines are easier and less expensive to produce. Their biggest drawback, as mentioned earlier, is that they do not closely mimic a natural infection and are consequently less effective than live vaccines. Furthermore, because killed preparations are pH labile and susceptible to proteases in the stomach, they usually must be injected, even if the parasite in question is not bloodborne. The efficacy of killed vaccines can often be increased by including adjuvants in the vaccine preparation. An adjuvant is a compound that increases the immune response to the antigens with which it is mixed. Often these adjuvants are ligands for Toll-like receptors (TLRs) that readily bind TLRs on antigen-presenting cells (see the online review of vertebrate immunology).
The Challenge of Parasite Control
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2023
Besides being safer, inactivated vaccines are easier and less expensive to produce. Their biggest drawback, as mentioned earlier, is that they do not closely mimic a natural infection and are consequently less effective than live vaccines. Furthermore, because killed preparations are pH labile and vulnerable to harsh stomach conditions, they usually must be injected, even if the parasite in question is not blood-borne. The efficacy of killed vaccines can often be increased by including adjuvants in the vaccine preparation. An adjuvant is a compound that increases the immune response to the antigens with which it is mixed. Often these adjuvants are ligands for Toll-like receptors (TLRs) that readily bind TLRs on antigen-presenting cells (see the online review of vertebrate immunology).
The Space Shuttle
Norman Begg in The Remarkable Story of Vaccines, 2023
An adjuvant is an important ingredient for some vaccines. These performance-enhancing substances are very useful from a manufacturing perspective. With an improved immune response, it is possible to lower the amount of the active component in the vaccine and make more doses. This can be critical when manufacturing needs to be ramped up quickly, for example in a response to a flu pandemic. The science of adjuvants has mushroomed in recent years. Many naturally derived products have been found to enhance the immune response to vaccines. Squalene is an oil found in many plants and animals, especially sharks. The oil that lubricates human skin and hair contains squalene. It is used as an adjuvant for some flu vaccines. Another adjuvant, monophosphoryl liquid (MPL) is isolated from the surface of a type of salmonella bacteria. The ingredients of these modern bespoke adjuvants are not so easy to come by. For example, one adjuvant is derived from a plant extract from a soap bark tree, Quillaja saponaria, which grows only in central Chile, in protected plantations.
Overcoming scientific barriers in the transition from in vivo to non-animal batch testing of human and veterinary vaccines
Published in Expert Review of Vaccines, 2021
Robin H. G. A. van den Biggelaar, Marcel H.N. Hoefnagel, Rob J. Vandebriel, Arjen Sloots, Coenraad F.M. Hendriksen, Willem van Eden, Victor P. M. G. Rutten, Christine A. Jansen
Many inactivated, toxoid and subunit vaccines require adjuvants to support activation of the immune system. For a long period of time, only aluminum salts and mineral oil emulsions were used as adjuvants. Aluminum salts are used as adjuvants for human vaccines such as diphtheria and tetanus vaccines as well as veterinary vaccines such as the bluetongue vaccine for ruminants, some feline leukemia vaccines and the rabies vaccine for dogs, cats, ruminants and horses [98,99]. The first emulsion adjuvants were Freund’s incomplete adjuvant, based on mineral oil emulsified in a water-in-oil formulation, and Freund’s complete adjuvant, formulated with tubercle bacteria [100]. Mineral oil-based water-in-oil adjuvants are too reactogenic for use in humans, but are widely used in poultry, cattle and fish [101,102]. The first emulsion adjuvant to be approved in humans was MF59, which is an oil-in-water adjuvant based on squalene [103].
Development of thermostable vaccine adjuvants
Published in Expert Review of Vaccines, 2021
Attempts to develop thermostable formulations have been reported for most classes of adjuvants, including aluminum salts, oil-in-water emulsions, liposomes, polymeric particles, virosomes, virus-like particles, mucosal and dermal formulations, and other novel adjuvant platforms. Besides optimization of liquid formulations, lyophilization and spray drying technologies to generate dried adjuvant formulations have been widely employed in preclinical studies. Nevertheless, significant gaps remain. More effort is needed to advance development of thermostable adjuvant-containing products to clinical and licensure stages. Moreover, the thermostability of some candidates is not always well characterized even when there is apparently good potential for expecting increased stability, such as in the case of dried formulations. Translation of the promising approaches reported here to cGMP manufacturing and clinical testing should enable eventual licensure of next generation adjuvant-containing vaccines that are better suited for distribution in resource-poor areas.
Targeting strategies of liposomal subunit vaccine delivery systems to improve vaccine efficacy
Published in Journal of Drug Targeting, 2019
Rui Yu, Yaping Mai, Yue Zhao, Yanhui Hou, Yanhua Liu, Jianhong Yang
Adjuvants are key ingredients of vaccines that potentiate the immune response and/or modulate it toward a desired immune response. Adjuvants usually exhibit multiple mechanisms such as depot formation, increased antigen presentation by antigen presenting cells (APCs) and induced secretion of immune-modulatory cytokines. The first adjuvants used in humans were aluminium-based adjuvants, which rarely impart cytotoxic T lymphocyte (CTL) responses; other common adjuvants such as oil emulsions and saponins usually induce local side effects [4]. Therefore, to obtain the desired immune response and to treat many newly emerging diseases, more powerful, improved adjuvants need to be developed. In recent years, nanoparticles have been found to be potential candidate adjuvants for vaccine formulations. Among the various types of nanoparticles, liposome-based carriers have attracted much attention, owing to their enormous application potential.
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