Prove the Mucosal Adjuvanticity of LT Mutants with Influenza Antigens for FOR Intranasal Immunisation
Mucosal administration of antigens is a global priority. Many approaches have been adopted to develop vaccines that can be delivered without using syringes and that induce immune response at the mucosal sites that are often the portal of entry of pathogens. Here we propose to manufacture GMP lots of the mucosal adjuvants LTK63 and LTR72, two non-toxic derivatives of E. coli enterotoxin obtained by site-directed mutagenesis, and to test them in a clinical setting in human adult volunteers to obtain proof of concept that these molecules can be effectively used to adjuvant mucosal vaccines for human use. As a model, for this demonstration project we have chosen the influenza vaccine for intranasal administration.
Delivery of vaccines by mucosal route is one of the major goals of today's research. The advantage of easier delivery combined with the possibility of neutralising pathogens at their portal of entry have made mucosal immunisation one of the major targets of the European Union, WHO and the US NIH. Furthermore, mucosal delivery by eliminating the use of syringes would increase compliance and decrease the risk of spread of infectious diseases that has been reported by improper use of syringes during vaccination.[+] Read More
In spite of the obvious advantages offered by mucosal vaccination, and the success obtained in this area in animal models in recent years, mucosal vaccines are not yet a reality, and it remains unclear whether they can be used for human vaccination. It is therefore mandatory to obtain proof of concept of the feasibility in humans of mucosal vaccines.
Most vaccines are unable to induce an immune response when delivered at mucosal sites. In order to make them immunogenic, strong mucosal adjuvants are required. In animals, the most potent mucosal adjuvants are the E. coli enterotoxin (LT) and cholera toxin (CT). Unfortunately, these two toxins cannot be used in humans and therefore their use as mucosal adjuvants has been restricted to animal studies.
Recently, by site-directed mutagenesis, mutants of LT have been obtained which are either completely non-toxic or have greatly reduced toxicity. Preclinical studies have shown that these mutants still act as mucosal adjuvants when used in animal models, and that the LT mutants are generally more active than the CT mutants. Two particular LT mutants, LTK63 and LTR72, both of which are completely non-toxic or with very low residual activity showed, respectively, a good safety and adjuvanticity profile in preclinical studies, suggesting that they could be proposed for human studies.
This project was officially initiated on February 1, 2000, and concluded its technical and experimental activities on January 31, 2003.
The key objectives of the project were to demonstrate:
The following project milestones have been achieved:
Overall, our studies have indeed shown that LTK63 can be safely used as a mucosal adjuvant for intranasal administration in humans and in addition it enhances the immune response at the mucosal level.
The results deriving from this project will be useful to potentially open the way to the clinical development of many other mucosal vaccines, including the development of vaccines against traveller's diarrhoea, which could be targeted by recombinant LT mutants produced in E. coli. The knowledge and results produced in the course of the MUCADJ project will also be used for the development of vaccines for future pandemics such as the H5N1 influenza. To this purpose, several studies have already been started by most MUCADJ participants using a non-pathogenic variant influenza A/Duck/Singapore/97 (H5N3) virus as leading vaccine candidate combined with the adjuvant emulsion MF59TM . The key preclinical and clinical results obtained in the MUCADJ project have already been published in the following papers:
On the whole, these findings have important implications for the rational design of vaccines for future pandemics.