Journal of Virological Methods 89 (2000) 129 – 136 Serodiagnosis of African swine fever using the recombinant protein p30 expressed in insect larvae M.G. Barderas a , A. Wigdorovitz b , F. Merelo c , F. Beitia c , C. Alonso a , M.V. Borca b , J.M. Escribano a, * a Departamento de Mejora Gene ´tica y Biotecnologı ´a, INIA, Ctra A Corun ˜a Km 7, 28040 Madrid, Spain b Instituto de Virologı ´a, C.I.C.V., Inta -Castelar, CC77, Moro ´n, (1708) Pcia. De Buenos Aires, Argentina c Departamento de Proteccio ´n Vegetal, INIA, Ctra A Corun ˜a Km 7, 28040 Madrid, Spain Received 4 April 2000; received in revised form 7 June 2000; accepted 9 June 2000 Abstract African swine fever (ASF) has a substantial economic impact in many African developing countries and its eradication is based only on an efficient diagnosis program because of the absence of an available vaccine. Previous data suggested the convenience of using the highly antigenic virus protein p30 as ELISA antigen for serological diagnosis of this disease. A simple and efficient method is described for producing the recombinant protein p30 from ASF virus in Trichoplusia ni larvae (cabbage looper) in order to facilitate the large-scale production of this recombinant protein in the absence of fermentation procedures. A baculovirus encoding the virus protein p30 was used to infect insect larvae, showing that recombinant protein production had a sharp optimal peak with a time of occurrence dependent on the initial virus dose inoculated to the larvae. Crude lysates of infected larvae were used without further purification as coating antigen in ELISA to analyse a limited number of sera from natural or experimentally ASF virus infected pigs. Remarkably, the recombinant protein obtained from a single infected larva was sufficient for serological diagnosis of at least 3750 serum samples. Recombinant p30 obtained by this procedure was also used in a confirmatory immunoblotting, reacting with all positive sera tested previously by ELISA. In conclusion, production of the recombinant ASF virus protein p30 in larvae should be applicable to large-scale production of diagnostic reagents for this disease in developing countries, eliminating the need for specialised facilities for tissue culture. © 2000 Elsevier Science B.V. All rights reserved. Keywords: African swine fever; p30; Trichoplusia ni larvae www.elsevier.com/locate/jviromet 1. Introduction African swine fever (ASF) virus is an icosahe- dral cytoplasmic deoxyvirus that infects domestic pigs and soft ticks of the Ornithodoros genus. This virus is presently the sole member of the As- * Corresponding author. Fax: +34-91-3573107. E-mail address: escriban@inia.es (J.M. Escribano). 0166-0934/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S0166-0934(00)00209-3