Immunization with BLS-Stx2B protects rats from early pregnancy loss mediated by Stx2

SACERDOTI FLAVIA; MEJIAS, MARÍA PILAR; PALERMO, MARINA ; IBARRA, CRISTINA

Boston

Congreso; 9th International Symposium on Shiga Toxin (Verocytotin)-Producing Escherichia coli Infections; 2015

Introduction: Shiga toxin type 2 (Stx2) mediates pregnancy loss in rats in early stage of pregnancy. In the present work we assayed an immunization strategy with the Brucella lumazine synthase-Stx2B subunit chimera (BLS-Stx2B) to protect pregnant rats from Stx2 mediated early pregnancy loss.Methods: Adult female Sprague Dawely rats were subcutaneously immunized with 3 doses of BLS-Stx2B on days 0, 15 and 30. No immunized mothers were injected with vehicle. Serum samples were collected one day before every booster and anti-Stx2 serum antibodies were checked by ELISA. Stx2-neutralizing activity was evaluated in Vero cells. Female rats were then mated with males and day 1 of gestation was determined when spermatozoa was found in the vaginal smear. At day 8 of gestation immunized mothers were divided into two groups, and challenged intraperitoneally (i.p) with Stx2 (0.5 ng Stx2/g bwt) or PBS (Control) respectively. No immunized mothers were injected i.p. with the same dose of Stx2 (sublethal, 100% of pregnancy loss). Mothers were weighted daily until 10 days after injection. Progression of pregnancy, number, weight and behavior of the pups at birth were analyzed and compared between groups. Results and Discussion: Immunized rats developed high specific neutralizing antibody titers and mothers challenged with Stx2 gained weight as controls and delivered pups at term. No immunized mothers showed a marked decrease in weight until 4 days after injection and then recovered gradually but had 100% of fetal resorptions. No difference was observed in the number and weight of the pups at birth from immunized rats challenged with Stx2 compared to controls. Studies are in progress to evaluate if immunization of pregnant rats with BLS-Stx2B could confer protection against Stx2 toxicity in their weaned offspring.Implications: Our results of Stx2 mediated early pregnancy loss in rats may be an indication that this event could happen in humans and that an effective immunization could be a successful strategy to prevent this outcome.