Systemic and in vitro expression of goat α1-acid glycoprotein during Caprine Arthritis-Encephalitis Virus infection

The present study was carried out in order to investigate the systemic and local expression of the acute-phase protein alpha(1)-acid glycoprotein (AGP, Orosomucoid) during Caprine Arthritis-Encephalitis Virus (CAEV) natural infection. The aminoacid sequence of goat AGP (gAGP), which was unknown, was determined by cDNA sequencing of the gene. AGP serum concentration was analyzed from 40 healthy and 36 CAEV-induced arthritis-affected goats. The mean concentration of AGP in healthy goats was of 219.8 microg/ml (+/-178.6 s.d.) and did not statistically differ from that of arthritis-affected goats (157 microg/ml, +/-137.8 s.d.). In a second set of experiments, AGP was purified to homogeneity from the serum of healthy and unhealthy goats, and the glycan pattern modifications were analyzed by means of specific binding with lectins. In particular, branching, fucosylation and alpha(1-6)- and alpha(1-3)-linked sialylation were analyzed. Goat AGP is not fucosylated in neither physiological nor pathological status. On the contrary, both major (branching) and minor (sialylation) microheterogeneities increase during arthritis. Finally, the possible local synovial origin of gAGP was determined by means of in vitro expression studies (real-time PCR) which used goat synovial membrane (GSM) as cellular model. It was found that gAGP's mRNA can be constitutively produced by GSM cells, but real-time PCR experiments revealed that the expression of AGP was not influenced by in vitro infection with CAEV.