Geir Mathiesen /Norwegian University of Life Sciences

We have input on theme I, action line 1.3, Improve vaccine formulation and delivery
We have developed novel vaccine delivery technologies for oral and nasal administration using Lactobacillus. These bacteria, being food grade and a part of the normal human microflora, have the potential of becoming a cheap and safe alternative for needle-free mucosal vaccination. This strategy would provide an easily produced and distributable vaccine with freezer free storage. The delivery system is designed by modifying Lactobacillus to produce Mycobacterium target antigens and anchoring these to the cell wall. The surface display system allows controllable antigen expression and various surface location, that vary in, for example the extent to which the antigen is exposed on the bacterial cell wall. The thick peptidoglycan cell wall of the gram-positive Lactobacillus offers protection of the embedded antigens from harsh conditions that may be encountered during e.g. storage or exposure to mucosal layers. After producing bacteria with surface displayed antigen by simple fermentation, the producing cells may be inactivated prior to vaccine administration (e.g. by UV-irradiation). Inactivated bacteria will still display functional immunological antigens at the cell surface and can therefore be administrated as (dead) particles covered with antigens. This allows easy control of the amount of antigen and avoids administration of living cells.

A toolbox with different anchors is available, giving us the ability to precisely attach antigens at various locations on the bacterial outer surface, using covalent cell wall anchors, non-covalent (LysM domain-based) cell wall anchors, lipid-based membrane anchors and transmembrane peptide-based anchors. It is anticipated that an antigen attached to the surface of the bacterium increases its on-site concentration and provides good accessibility to immune cells, while simultaneously being protected from harsh conditions in the gastro-intestinal or pulmonary tracts. The exposure of anchored antigens varies depending on the choice of anchor, offering a possibility to optimize the protection exposure balance. The cell wall of lactobacilli may, as such, act as an adjuvant and this property will vary between Lactobacillus species. Our antigen anchoring technologies are available for multiple species of Lactobacillus that all compatible with use in humans.
So far, engineered lactobacilli with surface displayed Ag85B-ESAT6 fusion antigen have been used as a model for anchoring of TB- antigens. Functional tests in mice have shown that Lactobacillus expressing surface displayed antigens induces both cellular and humoral immune responses, as well as an antigen specific IgA responses at mucosal surfaces. In several studies, we have demonstrated the potential of this delivery/anchoring system. In a recent study, it was shown that administration of our recombinant lactobacilli as a booster vaccine of BCG induced specific cellular immunity, demonstrated by T-cell proliferation, antigen specific IFN-γ responses and multifunctional T cells phenotypes (please see attached article by Kuczkowska et al.). Importantly, challenge experiments showed that an intranasal boost with our recombinant Lactobacillus enhanced the protection provided by BCG in terms of reduced loads of M. tuberculosis in the lungs.
Based on our studies of this anchoring and delivery system, and the good results obtained so far with little funding (cf. attached articles), we believe this system should be included in future efforts, to undergo more standardized testing and optimization. Therefore, we believe that this system should be included under “Improve vaccine formulation and delivery” in the Road Map.
Do not hesitate to contact me if you have any questions.

Best regards
Geir Mathiesen
Senior Researcher
Norwegian University of Life Sciences (NMBU),
Faculty of Chemistry, Biotechnology and Food Science,
Chr. M. Falsensvei 1,
Box 5003,
N-1432 Ås,
Tel + 47 67 23 25 21