Development of a mouse model of gradual Shiga toxin 2 (Stx2) intoxication for testing a newly developed polyclonal antibody against Hemolytic Uremic Syndrome (HUS).

MEJIAS MP , ; FERNANDEZ-BRANDO RJ,; RAMOS, MV; ABREY-RECALDE MJ; MEISS R P; PALERMO MS.

Mar del Plata

Congreso; . LIX Reunión Científica Anual de la Sociedad Argentina de Investigación Clínica y LXII Reunión Científica Anual de la Sociedad Argentina de Inmunología; 2014

Sociedad Argentina de Inmunología,

Post-diarrhea HUS is a life-threatening complication of Shiga toxin (Stx)-producing E. coli infections (STEC), characterized by acute renal failure, thrombocytopenia and hemolytic anemia. The Stx is the main pathogenic factor and is responsible for HUS development. As such, mice are often used to explore the effects of Stx intoxication, by the intravenous administration of a high single dose. We developed an alternative mouse model of Stx2 intoxication through a protocol of incremental doses. 1LD100 of Stx2 was divided in four doses that were administrated i.v. once a day for 4 consecutive days. The first two doses were lower (0.009 pmoles/mouse each dose) and the last two doses were higher (0.016 pmoles/mouse each dose), in order to imitate the release of toxin by the bacteria colonizing the intestines. We observed a dose-dependent mortality (n, % of mortality): 2 doses (18, 5.6%), 3 doses (11, 91%) and 4 doses (12, 100%) within 6 days from the first inoculation. In addition, animals developed signs of HUS (n, mean±SEM): neutrophilia (%PMN cells)(day 0: 8,18±2.4; day 4: 8, 38±2.8*; day 5: 4, 49±8.3*) , leukocytopenia (leukocytes x106/ml)(day 0: 8, 10.5±1.2; day 4: 8, 7.8±0.7: day 5: 4, 5.7±1.15*) and increased levels of plasmatic urea (mg%)(day 0: 8, 49.5±2.1; day 4: 8, 136.4±7.9*; day 5: 4, 374.6±24.2*). Finally, we tested the efficacy of a recently developed polyclonal anti-Stx2 antibody (Ab) to block the pathogenicity of Stx2 (in this model). Stx2 was administered daily and a single dose of Ab was administrated i.v. on day 0, or 1 or 2. Ab was able to fully protect mice even when administered on day 2 (n=3). This model would provide an advantage for therapeutic experimentation. Results suggest that the administration of a highly neutralizing anti-Stx2 Ab may be therapeutically effective in humans at risk of developing HUS, if Ab is administered at an early time after STEC infection and before the accumulated effects of Stx result in irreversible structural damage