ABSTRACT The pacu is one of the most important species for Brazilian fish farming and is considered emerging in the global aquaculture. Despite its importance, no effective tool for evaluation of the adaptive immune response of this species has been developed. Therefore, this study aimed the development and standardization of indirect ELISA for the measurement of pacu antigen-specific antibodies using polyclonal rabbit anti-pacu IgM used as detector antibody. For this purpose was isolated and purificated of pacu IgM using mannose-binding protein affinity chromatography and produced specific polyclonal antibodies against heavy and light chains pacu IgM, that showed a molecular weight of 72 kDa and 26 kDa, respectively. Polyclonal antibodies obtained demonstrated specificity with heavy and light Ig chains of pacu serum in western blotting. These polyclonal antibodies allowed the development of an indirect ELISA assay of high sensitivity and specificity for the detection and quantification of pacu IgM antibodies immunized with bovine IgG. In conclusion, this approach has great potential to improve the monitoring of vaccine-induced immune responses and help develop immunodiagnostic and epidemiological studies of infectious diseases in pacu systems.

Doze isolados de campo do Brasil e uma estirpe de referência vacinal do vírus da bronquite infecciosa das aves (VBI) foram propagadas em ovos embrionados SPF. O gene S1 dessas amostras foi analisado por RT-PCR seguido de RFLP, empregando-se as enzimas de restrição HaeIII, XcmI e BstyI. Observou-se a existência de cinco genotipos diferentes: M (Massachusetts), A , B, C e D. Cinco dos doze isolados de campo do VBI foram classificados no genótipo Massachusetts e os sete vírus restantes foram classificados em quatro genotipos diferentes; A (2), B (2), C (2) ou D (1). Os resultados desta genotipagem concordam com os dados obtidos na análise imunológica previamente realizada para a maior parte destes vírus, destacando a ocorrência de uma variabilidade marcante entre os isolados do VBI que estão circulando nas granjas avícolas comerciais do Brasil.

Twelve Brazilian isolates and one reference vaccine strain of avian infectious bronchitis virus (IBV) were propagated in embryonating chicken eggs. The entire S1 glycoprotein gene of these viruses was analysed by reverse-transcriptase-polymerase chain reaction and restriction fragment length polymorphism (RT-PCR-RFLP), using the restriction enzymes HaeIII, XcmI and BstyI. The RFLP patterns led to the classification of these isolates into five distinct genotypes: A, B, C, D and Massachusetts. Five of twelve isolates were grouped in Massachusetts genotype and the remaining seven viruses were classified into four distinct genotypes: A (2), B (2), C (2) or D (1). Such genotyping classification agreed with previous immunological analysis for most of these viruses, highlighting the occurrence of a relevant variability among the IBV strains that are circulating in Brazilian commercial poultry flocks.