LACK OF AN IMMUNE-RESPONSE TO ALBUNEX(R), A NEW ULTRASOUND CONTRAST AGENT BASED ON AIR-FILLED ALBUMIN MICROSPHERES

Albunex(R) is a new ultrasound contrast agent consisting of air-filled microspheres of heat-aggregated human albumin suspended in a 5% (w/v) solution of human albumin for infusion. The structural alterations in duced in the albumin molecules during heat aggregation may cause the f ormation of new epitopes that may provoke an immunological response in recipients. To assess the possible immunogenicity of the contrast age nt, 34 healthy volunteers were randomized to receive four injections o f either Albunex or 5% human serum albumin (0.01 ml/kg) at 4-week inte rvals. Analysis of blood samples taken 3 weeks after each injection di d not reveal any formation of IgE or IgG antibodies directed against t he Albunex microsphere protein or albumin in any of the recipients. Th e evaluation of novel enzyme immunosorbent assays developed to detect the presence of these specific IgE and IgG antibodies is described. It was also investigated whether the heat-aggregated microsphere albumin was structurally altered in such a way that it could be recognized by cat albumin specific IgE, present in the sera of individuals allergic to cat albumin. 187 serum samples shown to contain elevated levels of cat albumin specific IgE were used in the study. No cross-reactive bi nding of the heat-aggregated human albumin to anticat albumin IgE coul d be detected. There is no evidence from the present studies that the heat-aggregated albumin of the Albunex microspheres will provoke an im munological reaction upon repeated injections or cause an adverse reac tion when administered to allergic individuals having cat albumin as o ne of their allergens.