Adjuvant in a vaccine

Subject: Science and tech

Context:

Coronavirus vaccine Covaxin will use adjuvant Alhydroxiquim-II to boost immune response and longer lasting immunity.

Concept:

• An adjuvant is a substance that is co-injected with antigen in order to help stimulate and enhance the adaptive immune system into producing antibodies against the antigen.
• Adjuvants affect the immune response in various ways:
  • To increase the immunogenicity of weak antigens
  • To enhance speed and duration of immune response
  • To stimulate and modulate humoral responses, including antibody isotype
  • To stimulate cell-mediated immunity
  • To improve induction of mucosal immunity
  • Enhance immune responses in immunologically immature patients, particularly infants
  • To decrease the dose of antigen required; reducing costs and eliminating inconvenient requirements for booster shots
• Many molecules have been considered for use as an adjuvant, including mineral compounds (e.g. Alum), water-in-oil or oil-in-water emulsions (e.g. Freund’s adjuvant), as well as natural and synthetic toxins derived from bacteria (e.g. cholera toxin, CT and lymphotoxin, LT).
• Based on their mechanism of action, adjuvants have been categorised into two broad groups; the particulate vaccine-delivery systems that target antigen to antigen presenting cells (APCs) and the immunostimulatory adjuvants that directly activate such cells through specific receptors e.g. toll-like receptors (TLRs) resulting in inflammatory responses that amplify the innate immune response.
• The ultimate aim is to activate the innate immune system to respond more rapidly to infection and for the adaptive immune response to become more specific.