Antibody response against Shiga toxin-2 subunits in patients with Hemolitic Uremic Syndrome

FERNÁNDEZ BRANDO, RJ; BENTANCOR LV; RAMOS, MV; FERNÁNDES GC; EXENI R; GRIMOLDI I; LASO MC; EXENI A; TIRONI FARINATI C; ISTURIZ MA; PALERMO MS

Buenos Aires

Simposio; 7th International Symposium on Shiga Toxin (Verocytotoxin) Producing E.coli Infections.; 2009

Asociación Argentina de Microbiología

Typical or post-diarrhea hemolytic uremic syndrome (D+SUH) is an endemic disease in Argentina and develops secondary to infections with Shiga-toxin (Stx)-producing Escherichia coli (STEC) strains. Clinical, epidemiologic and experimental data suggest that humoral and specific immunity against anti-Stx limits the risk of HUS.  Clinically, the very low incidence of D+HUS secondary episodes also supports the existence of an efficient anti-Stx protective immunologic response. The aim of the present work was to study specific IgG-antibodies against to Stx2-subunits (A Sub and B Sub) by Western blot (WB) analysis in Argentinean children, as well as the development of a complementary ELISA test to detect Sub B-antibodies. The clinical groups included: D+SUH patients during the acute period (HUS) (n=40) and after different times of recovery (recHUS) (n=17), healthy children (HC) (n=38) and children coursing the acute period of a non-related infection (inf) (n=19). Results: The percentage of positive patients for anti- A Sub and/or anti- B Sub Ab by WB were: HC = 61%, inf = 58%, HUS = 90% and recHUS = 88% (p< 0.01, c2). Comparing double positive sample percentages (B Sub + and A Sub +) in clinical groups, we observed: HC = 32%, inf = 37%, HUS = 60% and recHUS = 41% (p< 0.01, c2). When we analyzed Ab specificity among positive children we found: anti-Sub A: HC = 74%, inf = 82%, HUS = 83% and recHUS = 80%; anti-Sub B: HC = 78%, inf = 82%, HUS = 83%, recHUS = 67%. The ELISA cut-off value was determined as the mean DO ± 2 SD of anti- B Sub negative sera samples by WB which showed low titers of ELISA at the same time. The percentage of positive samples detected by both methodologies was: HC = 39%, inf = 37, HUS = 77%, recHUS = 29% (p< 0.01, c2). Conclusions: The presence of specific Ab in HC and inf group may suggest a previous Stx contact. The high percentage of positive sera in these control groups in our population may be related to the endemic behavior of HUS in Argentina. In addition, HUS patients develop a specific humoral immune response against both Stx2 subunits. The Ab specificity in HC, inf and HUS groups do not indicate a preferential production of Ab against one subunit above the other. Nevertheless, recHUS group shows a slightly lower percentage of patients positive for anti-B Sub. Only in HUS group there is a close association between anti- B Sub Ab detection by WB and ELISA. These results lead us to suggest that the evaluation of Ab response using two methods would allow a better diagnostic approach.