VHH ANTIBODIES AGAINST THE B SUBUNIT OF SHIGA TOXIN 2 (STX2B) AS NOVEL THERAPEUTIC TOOLS AGAINST HUS.

MEJIAS MP; HIRIART, Y; FERNÁNDEZ BRANDO, ROMINA J; PARDO, R; BRUBALLA, A; GOLDBAUM, FERNANDO; ZYLBERMAN, VANESA; PALERMO, MARINA S

Buenos Aires

Congreso; IV LASID Meeting LXIII Argentinean Society for Immunology Meeting II French-Argentinean Immunology Meeting; 2015

LASID-FAIC-SAI

Background: Infection with Stx2-producing Escherichia coli (STEC) can progress to Hemolytic UremicSyndrome (HUS), for which no effective therapy is presently available. Wegenerated a chimeric BLS-Stx2B immunogen, which raised high affinity andprotective anti-Stx2B antibodies. The aim of this work was to use BLS-Stx2B toproduce therapeutic VHH antibodies against Stx2.Methods: Two llamas were immunized withBLS-Stx2B and anti-Stx2B VHH clones were selected from a phage display library.Three formats were evaluated: monomeric 2vb27, a bivalent [(2vb27)2]and a heterotrimeric molecule [(2vb27)2-SA; SA: anti-human serumalbumin VHH]. In vitro neutralizingactivity was measured by the Vero cell assay. For in vivo studies, Balb/c mice were injected i.v. with 1LD100Stx2 or i.g. with STEC. The half-life was determined by persistence of antibodyin plasma. Results: (2vb27)2and (2vb27)2-SA showed similar in vitro neutralizing activity, which was higher than 2vb27 (meanpmoles that neutralize 1CD50 Stx2 ±SD) (2vb27: 0.5±0.13, (2vb27)2:0.04±0.007*, (2vb27)2-SA: 0.06±0.04*; *p<0.05). However, all mice injected with Stx2 and treated with (2vb27)2-SA(0.1 pmoles) survived, while all those treated with PBS, 2vb27 or (2vb27)2died. Also, (2vb27)2-SA (0.5 pmoles) was able to fully protectagainst mortality and Stx2-associated renal damage after i.g. STEC challenge. Thein vivo half-life of 2vb27, (2vb27)2and (2vb27)2-SA was below 5 minutes, 5 hours and 10 days,respectively. Conclusions: (2vb27)2-SAshowed the highest in vivo protectionin both experimental models, probably due to the longer in vivo half-life. These VHH are promising therapeutic agents againstHUS.