In situ delivery of Interleukin-7 to adjuvant mucosal vaccines – VacMucIL7

The project uses a combination of in vitro and in vivo approaches to analyze the influence of IL-7 on mucosal immune responses:
1. Impact on the recruitment and activation of immune cells
2. Immunization against model antigens
3. Establishment of the proof of concept for the use of IL-7 as a mucosal vaccinen adjuvant in murine models of pulmonary (Influenza A) and vaginal (HSV-2) infection
4. Validation of the immunization protocol in non-human primates

1. Intratracheal administration of IL-7 induces the development of lymphoid aggregates in the lungs
2. The vaccination protocol using IL-7 as a vaccination adjuvant has been validated in a pulmonary immunization model, in mice
2. We have shown that the adsorption of IL-7 on PLA nanoparticles does not alter its specific activity
3. We have implemented protocols for the administration of PLA particles by aerosol with a device adapted to mice.

1. compare the efficacy of different modes of pulmonary administration (intranasal, intratracheal, by aerosol), in order to find a mode of administration transposable to humans and which induces good protection.
2. Develop the vaginal immunization protocol
3. Proof of concept of the efficacy of immunization protocols in lung and vaginal infection models
4. Implementation in non-human primate model

Poster presentations
1. IL-7 as a mucosal vaccine adjuvant in pulmonary immunization protocols. A. Sandouk, M. Rancez, B. Charmeteau-de-Muylder, S. Figueiredo, M. Benard, I. Garcia-Verdugo,, R. Cheynier, A. Couëdel-Courteille. Annual meeting of the SFI , Paris, 7-9th December, 2021
2. Eosinophils modulate the amplitude of the immune response during lung mucosal vaccination. Prince L, Martin L, Villeret B, Sanchez-Guzman D, LeGuen P, Sallenave JM, Garcia-Verdugo I. Annual meeting of the SFI, Paris, 7-9th December, 2021.
3. Prophylactic treatment with silver nanoparticles protects against influenza infection. L Martín-Faivre, L Prince, B Villeret, D Sanchez-Guzman, J-M Sallenave, I Garcia-Verdugo. Annual meeting of the SFI, Paris, 7-9th December, 2021.

Despite extensive effort on vaccine development, protection against mucosally acquired viruses remains a difficult goal, most vaccines favoring systemic immune responses including T-cell immunity and IgG-based humoral responses. Indeed, to successfully protect against mucosal pathogens, vaccine strategies should combine the use of proper adjuvant and local immunization to trigger efficient and long lasting mucosal immune responses.

We recently demonstrated that IL-7, secreted early and transiently after infection of mucosae, acts as a danger signal by inducing local expression of specific panels of chemokines that attracts immune cells at the infection sites. Similarly, locally administered IL-7 at the surface of vaginal mucosa or in the respiratory tract triggers local expression of chemokines and massive immune cell homing into these mucosae. Exploiting this property, VacMucIL7 project proposes that local delivery of IL-7, linked to poly(D, L-lactic acid) nanoparticles (PLA-NP) to favor mucosal barrier penetration, will prepare mucosae to further antigen delivery, improving immune responses to mucosal vaccines.

We will establish the proof of concept of the IL-7/PLA-NP efficacy to adjuvant mucosal vaccines in mouse and non-human primate models of lung and vaginal infections (Influenza A and Herpes simplex viruses). In a first work package, we will study in details the immediate consequences of local administration of IL-7 in mice and define the best combinations of IL-7 and antigen, associated with PLA-NP to initiate a mucosal immune response using diphtheria toxoid and ovalbumin as model antigens in both the lungs and the vagina. The efficacy of these combinations will then be confirmed in non-human primates.
Once established the best doses, time course and formulations for adequate mucosal vaccine delivery, we will test, both in mice and - non-human primate models, the efficacy of the best vaccine strategy to elicit protective mucosal immunity against respiratory tract infection with Influenza A virus or vaginal challenge with Herpes simplex virus type-2.

The expected impacts of VacMuc7 project will be at different levels:
- Develop an original approach to adjuvant mucosal vaccines by “preparing” the immunization site before vaccination using mucosal administration of a physiological dose of a natural molecule (IL-7) followed by local antigen delivery. This needle-free strategy will also avoid chemicals, presently disregarded by general population and participating to poor adhesion to vaccination campaigns.
- Provide a comprehensive analysis of the IL-7 impact on mucosal immunity, both in lungs and the vagina, strengthening our knowledge concerning this particular arm of the immune system.

Whether our approach of mucosal vaccination is successful to protect the animals not only against disease but, more importantly, against infection as a result of a quicker and better clearance at portals of entry of both airborne or sexually transmitted pathogens, it will be possible to adapt this strategy to the development of vaccines against other viral (HIV, Hepatitis…) and bacterial (Chlamydia…) infections that target mucosae and still represent major public health challenge. This project may also allow improving nanoparticles usage in vaccine development and permit elaborating new spray devices aimed at enhancing the efficiency of antigen availability/distribution at mucosal surfaces.

VacMucIL7 project combines the complementary skills of 3 research teams, from mucosal immunity to nanomedicine and fully meets the requirements of the Axe 3.10 of the ANR program. Through a pre-clinical approach, we will develop an innovative adjuvant strategy to improve mucosal vaccines. Moreover, the molecular and cellular players implicated in the early phase of mucosal immune reactions will be studied in details not only in mice but also more importantly in non-human primates.