Evaluation of the “shelf Life” of Nitrocellulose Membranes Immobilized with Paracoccidioides Brasiliensis Antigen for Performing the Immunodiagnosis of Paracoccidioidomycosis

The immunoblotting reaction for performing the paracoccidioidomycosis (PCM) immunodiagnosis is an in-house methodology ; and being a laborious task involving two previous steps, SDS-PAGE and Western blot, we evaluated the shelf life of nitrocellulose membranes containing the immobilized P. brasiliensis antigens, stored at -20 o C for 7, 15, 30, 45, 60 and 90 days. Twenty-eight serum samples were analyzed on two nitrocellulose membranes groups: (a) membranes previously blocked with PBS-5 % non-fat dry milk and (b) the priory non-blocked membranes. No difference was detected in the reactivity pattern in serum samples evaluated in the both membrane groups , especially for those stored for 7, 15, 30, 45 and 60 days. It might be emphasized that a good stability of P. brasiliensis antigens , immobilized on the nitrocellulose membranes, enable them to be stored up to 60 days at -20 o C . This finding contributes to the rapid diagnosis of PCM , and for sending them to other laboratories without adequate infrastructure for carrying out the steps that precede the immunodetection as the antigen production, SDS-PAGE and Western blot techniques . This scheme contributes substantially to improve the quality of PCM serodiagnosis , as it provides reproducible results in the units of the Laboratory Network