Journal of Virological Methods 121 (2004) 73–78 Development of recombinant capsid antigen/transmembrane epitope fusion proteins for serological diagnosis of animal lentivirus infections S. Rosati a,∗ , M. Profiti a , R. Lorenzetti b , P. Bandecchi c , A. Mannelli a , M. Ortoffi a , F. Tolari c , I.M. Ciabatti b a Dipartimento di Produzioni Animali, Epidemiologia ed Ecologia, Facoltà di Medicina Veterinaria, Università di Torino, Via Leonardo da Vinci 44, 10095 Grugliasco (TO), Italy b Istituto Zooprofilattico Sperimentale delle regioni Lazio e Toscana, Roma, Italy c Dipartimento di Patologia Animale, Profilassi ed Igiene degli Alimenti, Facoltà di Medicina Veterinaria, Università di Pisa, Pisa, Italy Received 16 March 2004; received in revised form 24 May 2004; accepted 15 June 2004 Available online 28 July 2004 Abstract Among animal lentiviruses, Feline immunodeficiency virus (FIV), Equine infectious anaemia virus (EIAV) and Small ruminant lentiviruses (SRLV) are important pathogens associated with a variety of clinical pictures including immunodeficiency, anaemia, arthritis, pneumonia. The detection of viral antibody response represents a practical diagnostic approach in all lentivirus infections since they remain detectable long life. Capsid antigen (CA) is the major viral core protein and specific antibodies against this antigen are usually first recognised in infected sheep, goat and horse, remaining detectable for long period. Transmembrane (TM) domain of envelope glycoprotein contains a well conserved motif known to form an immunodominant epitope in several lentiviruses. In this study a simple strategy was developed to express the entire CA and the TM epitope in a single fusion protein from equine, feline and small ruminant lentiviruses in prokaryotic system and evaluated the diagnostic utility of a purified preparation in an indirect ELISA for each of the three infections. Results demonstrate that, for FIV and SRLV infections, the combination of CA and TM fractions increases the sensitivity of diagnostic tests based only on CA. The corresponding CA/TM antigen from EIAV showed excellent agreement with Coggins test. © 2004 Elsevier B.V. All rights reserved. Keywords: Animal lentiviruses; Recombinant ELISA; Capsid antigen; Transmembrane epitope 1. Introduction The Lentivirus genus of the Retroviridae family includes non oncogenic exogenous viruses associated with a vari- ety of diseases of humans and other mammals. Among animal lentiviruses, feline immunodeficiency virus (FIV), equine infectious anaemia virus (EIAV) and small ruminant lentiviruses (SRLV) are important pathogens associated with a variety of clinical pictures including immunodefi- ciency, anaemia, arthritis, mastitis, pneumonia (McGuire et al., 1990; Hartmann, 1998; Bulgin, 1990; Pepin et al., 1998). The infectious status can be diagnosed well be- ∗ Corresponding author. Tel.: +39-011-6709187; fax: +39-011-6709196. E-mail address: sergio.rosati@unito.it (S. Rosati). fore the clinical stage, through detection of viral antibody response which usually remains long life. Common feature in animal lentiviruses is immunogenicity of some structural proteins. Capsid antigen (CA) is the major core protein with a molecular weight ranging 24–26 kDa and is highly conserved within each viral group. Specific CA antibodies are usually first recognised in infected horses or small ruminant (Houwers and Nauta, 1989; Zanoni et al., 1991; Burki et al., 1992) and remain detectable for long time. Surface glycoproteins (SU) are strong immunogens but antibody response is frequently strain associated due to antigenic drift, well known in EIAV infection (Salinovich et al., 1986; Burki et al., 1992). Transmembrane domain of envelope glycoprotein contains two conserved cysteine residues, known to form an immunodominant epitope in several lentiviruses (Pancino et al., 1994). The amino acid 0166-0934/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jviromet.2004.06.001