"EXOSOMES DERIVED FROM THE ASCITIC FLUID OF MICE BEARING A T-CEL LYMPHOMA EXPRESS TUMOR ASSOCIATED ANTIGENS"

MENAY, FLORENCIA; COCOZZA, FEDERICO; VENDRELL, ALEJANDRINA; WALDNER, CLAUDIA; MONGINI, CLAUDIA

Medellin

Congreso; "IMMUNOCOLOMBIA2015 - 11th Congress of the Latin American Association of Immunology - 10o. Congreso de la Asociación Colombiana de Alergia, Asma e Inmunología".; 2015

Asociación Colombiana de Alergia, Asma e Inmunología

Exosomes are extracellular nanovesicles of 60-100 nm (EVs), released by almost all cell types, including tumor cells. EVs are involved in cellcell communication. Through transfer of their molecular contents, EVs are capable of altering the function of recipient cells. Tumor derived exosomes may have either immunostimulating or immunosuppressant properties. Previous works demonstrated that the administration of exosomes derived from tumor cells lines into syngeneic animals produced both humoral and cellular immune response in immunized host, capable of rejecting tumor. These immunological functions have led to the development of antitumor vaccines based on exosomes, which are currently in early clinical development. The aim of this work was to isolate and define the immunomodulating characteristics of exosomes derived from the ascitic fluid obtained from Tcell lymphoma bearing mice. BALB/c mice were inoculated ip. with 1,00E+06 tumor LBC cells and after 20 ± 2 days ascitic fluid was collected by ventral puncture. Exosomes were isolated by a serial of differential centrifugation, ultrafiltration and ultracentrifugation at 100,000xg. The microvesicles were characterized by their floating density in a sucrose gradient and the presence of marker proteins Alix, Tsg101, CD63, and Hsp70 was determined by Western blotting and flow cytometry. BALB/c mice were immunized twice with 20 ug of exosomes/mouse with an interval of 7 days. The humoral immune response induced was studied by dot and Western blot, in sera obtained from immunized mice and compared with those from naïve mice. All mice studied had high titre of serum antibodies against both exosomes and LBC cells (1:12800) and recognized proteins of 45 and 50 kDa present in the exosomes and tumor cell lysate, as determined by Western blot. To study the immune properties in vivo immunized mice were challenged with 1,00E+06 LBC tumor cells. Fifty percent of the mice immunized with exosomes did not develop tumors, while the tumor incidence in control mice (nonimmunized and challenged with the LBC cells) was 100% (n = 8).To assess the specificity of the immune response generated on mice that rejected LBC tumor, mice were rechallenging with 2,00E+05 cells of a non related breast adenocarcinoma (LM3). All LBC tumor free mice that were rechallenged with tumor cells developed the LM3 breast tumor. We conclude that exosomes present in the ascitic fluid of LBC tumor bearing mice express tumor antigens and have immunestimulating properties. The immune response elicited in hosts was specific as it was sufficient to prevent tumor development in syngeneic mice but failed to prevent the progression of a nonrelated tumor. These findings reveal that exosomes are potent immune regulators and are relevant for the development of an "acellular" immunotherapy aproach.