Selection of Suitable Monoclonal Antibodies and Optimization of the Immunohistochemical Method for the Detection of Pathological Prion Protein in the Brains of Patients with Sporadic Creutzfeldt-Jakob Disease
Reliable diagnosis of prion diseases is based on a positive immunohistochemical reaction (IHR) using antibodies against prion protein (PrP). Unfortunately, this does not distinguish between cellular PrP (PrPC) and the pathological isoform (PrPSc). Consequently, this method requires intensive pre-treatments to remove PrPC and retrieve the epitope of PrPSc in paraffin sections of the brains of patients with prion disease.
The aim of this study was to test anti-PrP monoclonal antibodies (MAb) V5B2, K4B3, A4/5 and E5/9, which were prepared at the Blood Transfusion Center of Slovenia, in order to compare them with commercially available MAb 3F4 and 6H4, and to design a simple antigen retrieval method to label PrPSc in immunohistochemistry.
Sections of paraffin-embedded brain tissue for four cases of sporadic Creutzfeldt-Jakob disease (sCJD) and of two deceased patients of similar age who had not had CJD were treated with a modified standard ABC immunohistochemical method using our MAb, control MAb and four pre-treatments. The IHR of our MAb was compared with the IHR of the control MAb (3F4 and 6H4) with regard to the intensity of IHR and the number of positive reactions. The same MAb were tested on the frozen sections of two brains not affected by CJD without any pre-treatment.
The results showed that all four tested MAbs were specific for PrPSc since, unlike the two control MAbs, they did not react with PrPC in the frozen sections of non-CJD brain. An improvement in IHR at more intense section pre-treatments of tissues was also demonstrated in terms of intensity and the number of positive reactions (p<0.05). Our MAb V5B2 is more sensitive than the control MAb 3F4 (p = 0.03). It does not need an equally intense pre-treatment as MAb 3F4 to label PrPSc in CJD-affected brain.
The obtained results confirmed the hypothesis on the specificity of our MAb for PrPSc. Furthermore, we found that MAbs differ in terms of sensitivity and that MAb V5B2 is best suited for the diagnosis of CJD, even more so than the two control MAbs. MAb V5B2 is assumed to be suitable for the development of tests capable of detecting native PrPSc in frozen sections of potentially infected tissues, or in the bodily fluids of patients with prion diseases.