EVALUATION OF A NEW CPG-ODN FORMULATION AS ADJUVANT FOR THE B SUBUNIT OF SHIGA TOXIN 2 (STX2B)

GABRIELA A. FIORENTINO; MARÍA F, SÁNCHEZ VALLECILLO; CONSTANZA MARIN; SANTIAGO D. PALMA; DANIEL A. ALLEMANDI; BELKYS A. MALETTO; MARINA S. PALERMO

Congreso; Reunión Conjunta de Sociedades e Biociencias; 2017

Infection with Shiga toxins (Stx)-producing Escherichia coli can progress to Hemolytic Uremic Syndrome (HUS), for which no effective therapy is presently available. Stx type 2 (Stx2) is the most frequent variant associated with HUS, which constitute an AB5 toxin. The binding subunit (Stx2B) is a good vaccine candidate because it is non toxic and rising of neutralizing antibodies would be able to block the binding of Stx2 to its receptor and the first step in the pathogenesis. However, it is a poor immunogen. Our objective was to evaluate a new adjuvant strategy, CpG-ODN formulated with a nanostructure formed by self-assembly of 6-O-ascorbyl palmitate (Coa-ASC16), because it has been recently demonstrated to be an attractive system for promoting a specific immune response to weak antigens. Adult Balb/c mice were biweekly immunized with three s.c. injections of Stx2B alone (G1), or formulated with CpG-ODN (G2), or with CpG-ODN/Coa-ASC16 (G3), respectively. Mice were serially bled up to three months post-immunization. Titer of anti-Stx2 IgG antibodies (Ab) was determined by ELISA. Ab neutralizing capacity was measured in vitro by the Vero cell assay. For in vivo protective studies, mice were injected i.v. with 1LD100 Stx2 at three-months. Mortality rates and urea values at 72 h post Stx2 were recorded.The Stx-Ab response showed a peak of IgG at 45-day for three groups, and Stx-Ab titer from G2 was significantly higher than G1 since 30-day (30 d=p