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; MARINA S. PALERMO

Buenos Aires

Congreso; Reunion Conjunta de Sociedades de Biociencias; 2017

Sociedad Argentina de Investigación Clínica | Sociedad Argentina de Investigación Bioquímica y Biología Molecular | Sociedad Argentina de Inmunología | Sociedad Argentina de Andrología | Sociedad Argentina de Biofísica | Sociedad Argentina de Biología | S

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. ObjectiveOur 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.1.-Titer of anti-Stx2 IgG antibodies (Ab) was determined by ELISA.The Stx-Ab response showed a peak of IgG at 45-day for three groups (Fig 1), and Stx-Ab titer from G2 was significantly higher than G1 since 30-day (30 d=p<0.05; 45 d= p<0.05; 60 d=p<0.01; n=6/group; ANOVA and Dunnets post-test).(Fig 2, 3 and 4) 2.- Ab neutralizing capacity was measured in vitro by the Vero cell assay. Stx2 (1ng/mL) was pre-incubated 1h at 37C and 1 h at 4C with serum dilution (1/50). This mixture was added to the monolayer of confluent Vero cells and incubated during 72 h. Viable cells were measured by Crystal violet staining.3.- In vivo protective studies For in vivo protective studies, mice were injected i.v. with 1LD100 Stx2 at three-months. Urea values at 72 h and Mortality rates post Stx2 were recorded. Conclusions For Stx2B antigen, CpG-ODN formulation with Coa-ASC16 did not result in a better Ab specific response than CpG-ODN alone. Although CpG-ODN showed the highest Stx-Ab response, these Ab did not neutralize Stx2 in vitro nor protect in vivo against Stx2 injection.