Vacciguard Novel Vaccines

Currently, there are a few vaccine types that are often used to vaccinate large parts of the world's population to prevent selected infectious diseases:

• Attenuated or killed pathogen vaccines - vaccines containing the whole pathogen, bacteria or virus, attenuated or killed or detoxified to stimulate a protective immune response. The main drawbacks include: limited availability; risks in handling pathogenic material; storage and safety problems, especially to elderly and immune-compromised individuals. These significant limitations stimulated the interest in the development of subunit vaccines.

• Subunit vaccines - isolated protective antigenic epitopes derived from the exposed surface of the pathogen, such as proteins or peptides, polysaccharides of bacteria capsules, parts of the bacteria toxin. The main drawback is poor immunogenicity. These antigens are not easily recognized by the cellular immune arm (T cells) and therefore the immune response is inefficient and lacks long-term memory. In order to overcome this problem, adjuvant molecules and carriers are added. Therefore, there is a constant need for new, more effective adjuvant and carrier molecules.

• Conjugated subunit vaccines -An additional solution for improved immunogenicity of the subunit vaccines: the antigen is conjugated to a carrier in order to induce the  T-cell help response. This type of conjugation has been shown to induce antigen-specific immune responses, including long- term memory.
  The main drawbacks include: most carriers consist of high molecular weight proteins such as tetanus toxoid; therefore, there is a risk of sensitization reaction to the carrier itself, as has been reported for tetanus toxoid and flagellin. Although the carrier usually contains stimulatory T-cell epitopes, it also contains suppressive epitopes that may reduce its efficacy. In addition, it has been shown to suffer from a “carrier-induced epitope suppression” phenomenon.
  These significant disadvantages led to extensive efforts to search for improved and more efficient carrier molecules.