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

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

Buenos Aires

Congreso; . Reunión Conjunta de Sociedades de Biociencia; 2017

SAIC-SAIB-SAI-SAA-SAB-SAB-SAFE-SAFI-SAH-SAP

Infection with Shiga toxins (Stx)-producing Escherichiacoli can progress to HemolyticUremic Syndrome (HUS), for which no effective therapy is presentlyavailable. Stx type 2 (Stx2) is the most frequent variant associated with HUS,which constitute an AB5 toxin. The binding subunit (Stx2B) is a good vaccinecandidate because it is non toxic and rising of neutralizing antibodies wouldbe able to block the binding of Stx2 to its receptor and the first step in thepathogenesis. However, it is a poor immunogen. Our objective was to evaluate anew adjuvant strategy, CpG-ODN formulated with a nanostructure formed byself-assembly of 6-O-ascorbyl palmitate (Coa-ASC16), because it has beenrecently demonstrated to be an attractive system for promoting a specificimmune response to weak antigens. Adult Balb/c mice were biweekly immunizedwith three s.c.injections of Stx2B alone (G1), or formulated with CpG-ODN (G2), or withCpG-ODN/Coa-ASC16 (G3), respectively. Mice were serially bled up to threemonths post-immunization. Titer of anti-Stx2 IgG antibodies (Ab) was determinedby ELISA. Ab neutralizing capacity was measured in vitro by the Vero cell assay. For in vivo protective studies, mice were injected i.v. with 1LD100Stx2 at three-months. Mortality rates and urea values at 72 h post Stx2 wererecorded.The Stx-Ab response showed a peak of IgG at 45-day forthree groups, and Stx-Ab titer from G2 was significantly higher than G1 since30-day (30 d=p<0.05; 45 d= p<0.05; 60 d=p<0.01; n=6/group; ANOVA andDunnets post-test). However all serum samples showed a poor in vitro neutralizing activity, and noneof immunized mice were protected against after i.v Stx2.Conclusions: For Stx2B antigen, CpG-ODN formulation with Coa-ASC16did not result in a better Ab specific response than CpG-ODN alone. AlthoughCpG-ODN showed the highest Stx-Ab response, these Ab did not neutralize Stx2 invitro nor protect in vivo against Stx2 injection.