Use of cross-reactivity immunoassay to orient insulin replacement in diabetic patients with high levels of insulin antibodies

CARDOSO LA, POMARES M, AVALOS A, LAPERTOSA S, FRECHTEL G, POSKUS E

MethodX

ELSEVIER SCIENCE BV

Año: 2016 p. 502 - 507

The prevalence and high levels of anti-insulin antibodies (IA) havefrequently been associated with brittle diabetes, lipodystrophy in the areaswhere the insulin is injected and/or poor metabolic control. When this happens the usual criterion adopted is theempirical change of insulin type and/or formulation intending to diminish theIA level and then to decrease the undesirable side-effects. Here, wepresent a rational two step radiometric method consisting in: A) a first-lineradioligand binding assay (RBA) to assess IA in sera of these patients anddetecting those with high levels. B) applying a displacement assay (RIA) todetermine the in vitrocross-reactivity parameters (affinity constants and selectivity ratios) thatquantify the relative degree of interaction between antibodies and alternativeinsulin analogs. In this case report the RIA showed that the analog Glulisine(Glu), exhibited the lowest affinity constant (K0) and selectivityratio (S): K0: 1.00 x106 M-1, SGlu = 7.90 x 108M-1 / 1.00 x106 M-1 = 790). This means thatGlulisine exhibited in vitro 1/790 IA binding rate with respect to the regularhuman insulin at the same doses. Accordingly, we suggest that the analogGlulisine should be in principle the best theoretical option to replaceconventional human insulin. Since the replacement of NPH/regular insulin forinsulin analog the patient recovered metaboliccontrol, presenting with an HbA1c of 7.6% (IFCC 60 mmol/mol), and glycemia notexceeding 170mg% (9.4 mmol/L). The IA evolution after the change ofinsulin showed that the antibody level had decreased: RBA values fell from B%:30.5 to B%: 17.4 after 14 months of the new treatment. From these results weconclude that conventional criteria for selection of insulin analogs, in termsof pharmacokinetic and pharmacodinamic parameters, should be complemented withan appropriate test to assess affinity parameters when high IA title isdemonstrated. As the method was tested in a single case it requires confirmation usinga large group of patients.