BLS as an immunomodulator and carrier of tumor associated-antigens for the treatment of B16 melanoma

SOSA, SANTIAGO; GOLDIN CARLA; GOLDBAUM, FERNANDO A.; FARIAS ANA; BERGUER, PAULA M.

Mar del Plata

Congreso; Reunión anual Sociedades Biocientíficas; 2019

SAIC

Brucella lumazine synthase (BLS) is a homodecameric protein that activates dendritic cells (DC) via TLR4 inducing a proinflammatory response. Due to its structure, proteins can be fused to the 10 N-termini, constituting an already proven platform for the development of vaccines. The chimera BLS-OVA (containing ovalbumin peptide 257-264) induces the cross presentation of the peptide and a specific CTL response through TLR4. We have shown that treatment of B16-OVA melanoma-bearing mice with BLS or BLS-OVA have similar therapeutic outcomes, inducing significant but equal tumor growth delay and increased survival. It has been previously reported that the use of synthetic long peptides (SLP) improve the efficacy of immunotherapies. Hence, in order to increase the specific immune response, we designed two new chimeras: BLS-gp100, containing a long peptide from melanoma antigen gp100 with increased affinity to MHCI, and BLS-OVAXL, containing a longer peptide of the ovalbumin protein. To evaluate if the fusion of SLP increases the immune response in vitro, BMDC were stimulated with BLS-OVA or BLS-OVAXL and co-cultured with splenocytes from OT-I mice. Results show that the secretion of IFN-γ is similar in T cells activated with BMDC stimulated with BLS-OVAXL and with BLS-OVA. Interestingly, CD40 levels are higher in BMDC stimulated with BLS-OVAXL, showing that the use of SLP induces a greater DC activation. To evaluate the therapeutic effect of the different chimeras, mice were inoculated sc with B16-OVA cells and 2 days p.i., BLS-OVA, BLS-OVAXL or BLS-gp100 were sc administered. All treatments delay tumor development and improve mice survival. Moreover, both chimeras generated in this work increase the previously described therapeutic effect of BLS-OVA. In conclusion, we demonstrate that BLS can be used as a platform for immunotherapy and that the carrier effect can be enhanced by fusion of SLP, increasing the anti-tumor response.