Screening of antigen cross-presentation potentiating drugs for vaccine development

Salta

Congreso; LV Reunión Anual de Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2019

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

The cellular immune response mediated by the induction of cytotoxic CD8+ T lymphocytes (CTLs) is crucial for therapeutic interventions in tumor immunotherapy and for the induction of protective immunity against intracellular pathogens. Dendritic cells (DCs) are the only antigen (Ag) presenting cells of the immune system with the ability to activate naïve CD8+ T cells to generate CTLs, and are particularly fitted to internalize and present exogenous Ag (from infected, tumor, or dead cells) bound to MHC I molecules to naïve CD8+ T cells. This process, known as cross-presentation, is essential for antimicrobial and antitumor immunity. Non-living vaccine Ag, especially in subunit vaccines, are often poorly immunogenic and adjuvants are required to boost immunity. Adjuvants enhance immunogenicity of vaccines and experimental Ag by a variety of mechanisms. One of the current major challenges is developing adjuvants that help generation of protective CTLs responses to soluble proteins. So far, many adjuvants activate DCs and other Ag presenting cells to provide proper co-stimulatory signals to T cells. We have found that some adjuvant compounds can also activate Ag cross-presentation, increasing T cells activation levels. The complexity of Ag cross-presentation pathways challenges the identification of therapeutic targets in DCs to stimulate Ag cross-presentation. In this work we performed an in vitro screening using 1760 drugs approved by international agencies such as the FDA to identify chemical entities and molecular pathways capable of enhancing Ag cross-presentation in DCs. To achieve this goal, we developed a high-performance screening method by adapting the colorimetric B3Z presentation assay using JAWSII DC cell line and OVA as soluble Ag model. B3Z is a CD8+ T cell hybridoma specific for OVA257?264 epitope in the context of H-2Kb (MHC I) which is activated by the detection of OVA257-264 peptide associated to MHC I on the DC surface. The primary screening revealed an increase in Ag cross-presentation with approximately 1% of the assayed drugs. Among the active drugs, most of the hits had antiallergic, antimalarial, antiemetic or antipsychotic effects. Although these hits are currently under validation, it is interesting to highlight that several active compounds have biological activities that are compatible with a potential modulatory capacity of Ag cross-presentation (i.e., we found a chloroquine derivative and it has been previously reported that chloroquine favors soluble Ag cross-presentation, presumably by the delay of endosomal maturation). In conclusion, we established a sensitive, fast and robust screening platform for the search of compounds capable of stimulating Ag cross-presentation in DCs. The hits that pass the dose-response, structural and functional validation will be evaluated as adjuvants for both preventive and therapeutic vaccination strategies that require a CTL response.