Cross reaction of recombinant equine infectious anemia virus antigen to heterologous strains and application for serological survey among horses in the field

Cross reactivity of equine infectious anemia virus (EIAV) antigen prepared using a recombinant baculovirus containing the p26 gene of strain P337-V70 was examined by the agar gel immunodiffusion (AGID) test and enzyme-linked immunosorbent assay (ELISA), Serum samples serially collected from 13 horse s experimentally infected with six different EIAV strains (two or three hor ses per strain) were subjected to the test, Positive reactions were observe d in the AGID test and ELISA before or soon after the first feverish period and continued persistently in most of the horses. The results with recombi nant antigens were essentially the same as those with the virion antigen pr epared from horse cell cultures both in the AGID test and ELISA, The reacti vities of the antigens were further compared using serum samples collected from horses in 1999 in certain districts of Mongolia where equine infectiou s anemia has been prevalent, and from horses in Japan in 1973 when EM had n ot been eliminated completely from Japanese horses. These results were comp letely concurrent. Generally, recombinant antigens have high specificity bu t low cross reactivity to heterologous strains. However, the present study showed that the recombinant EIAV p26 antigen has cross reactivity to the he terologous strain and is useful for diagnosis of EIA in the field.