Cowpea mild mottle virus (CpMMV), the causal agent of stem necrosis disease, has drawn attention of soybean producers in recent years due to yield losses in the main producing regions of Brazil. Serological methods for viral detection require the use of an antiserum of good quality to achieve specificity and sensitivity. The entire coat protein gene of a Brazilian CpMMV isolate was cloned into a bacterial expression vector and transformed into Escherichia coli BL21::DE3 for in vitro expression. The coat protein, fused to a His-tag, was purified under denaturing conditions by affinity chromatography using a Ni-NTA resin. After renaturation, the integrity and identity of the purified recombinant protein was confirmed by SDS-Page and MALDI-ToF/ToF mass spectrometer analyses. A rabbit was immunized with increasing amounts of the recombinant protein. The specificity and sensitivity of the antiserum was demonstrated by Western blot and indirect ELISA assays. The polyclonal antisera raised against recombinant coat protein proved to be a reliable tool for CpMMV detection.

The aim of this study was to confirm clinical diagnosis of paratuberculosis in two cows showing suggestive clinical signs of the disease. Based on clinical signs, in culture and in IS900 PCR results from the individual milk samples it was possible to diagnose paratuberculosis in the cows studied.