Adjuvants and Delivery

The word “adjuvant” comes from the Latin adjuvare, meaning “to help.” Adjuvants are substances that enhance the ability of an antigen to stimulate an immune response in the body. IDRI’s Adjuvant and Delivery team focuses its efforts on pairing adjuvants with purified protein and polysaccharide antigens in the production of vaccines for leishmaniasis, chlamydia, TB, pneumoccocus and leprosy vaccines.

HISTORICALLY, vaccines either are prepared from live organisms able to grow in humans without causing disease, or they are prepared from killed organisms. The two vaccines for polio are examples: the oral polio vaccine is an attenuated vaccine made from the live virus, the injected polio vaccine is made from inactivated virus. 

Though either of these methods may produce highly protective vaccines, they may also cause undesirable responses. For some infectious diseases, much of the damage comes from unwanted side effects: from localized inflammation (seen as swelling, redness, and heat) to more severe reactions including fever and toxicity. These side effects are due to the immune response itself, and not directly from the growing pathogen or its toxins. To reduce side effects, vaccines can be designed that limit the amount of inflammation at the site of injection and induce a more favorable protective response by directing the type of immunity to favor a cellular rather than antibody-generated response. Thus, new vaccines that limit inflammation and stimulate effective cellular responses are necessary to combat many infectious diseases.

A third, novel vaccine approach uses purified antigen derived from the pathogen. Using part of the pathogen instead of the whole organism, as in the case of the acellular pertussis component of acellular DPT vaccine or Hepatitis B vaccine, can lessen adverse reactions. On their own, however, subunit vaccines often do not produce good immunity. The addition of adjuvants helps to boost the potency of the antigen and stimulate the immune system in an effective manner. 

IDRI’s Adjuvant and Delivery team has been studying novel adjuvants for use with various antigens in the production of vaccines for leishmaniasis, chlamydia, TB, and leprosy. By using synthetic bacterial lipopolysaccharide molecules, as well as other toll-like receptor agonists, the team is keeping its goal of directing the immune response with little or no side effect. 

THE METHOD OF DELIVERING the antigen-adjuvant mixture also has significant impact on vaccine potency. At IDRI, some of the different delivery systems being examined include emulsions, liposomes, naked DNA, and adenoviral vectors. As a part of these studies, the Adjuvant and Delivery team is also testing needle-free devices. These devices allow direct access to the dermal dendritic cells, which often facilitates a potent immune response—one that is frequently bypassed when vaccines are delivered intramuscularly or subcutaneously. An additional benefit of these needle-free devices is that they can avoid nerve endings in the skin, making immunizations pain-free.