CHANGES IN THE LEUKOCYTE PHENOTYPE PROFILE OF GOATS INFECTED WITH THECAPRINE ARTHRITIS-ENCEPHALITIS VIRUS

The proportions of different sub-populations of leukocytes in five hea lthy goats and five goats infected with the caprine arthritis encephal itis virus (CAEV) were examined using immunofluorescence and flow cyto metry. A panel of monoclonal antibodies that identified a monocyte-gra nulocyte marker (GMI); the CD4, CD8, IgM, MHC Class I, MHC Class II an d T19 antigens, and the gamma delta (gamma delta) T cell receptor was used. We observed a significant (P = 0.016) reduction in the proportio n of monocytes in the peripheral blood of infected (5.98%) compared wi th healthy control goats (9.92%). There was also a decrease in the pro portion of CD4 + T lymphocytes that approached significance (P = 0.076 ) accompanied by a slight increase in the proportion of CD8 + T lympho cytes, in infected compared with uninfected animals. Consequently, thr ee of the five infected animals had lower CD4:CD8 ratios than any of t he healthy animals and two of these three ratios were inverted. Approx imately 14% of T cells in the peripheral blood of healthy goats was id entified as gamma delta T cells and all expressed the T19 antigen. A s ignificantly elevated level of gamma delta T cells (P = 0.030) and an elevated level of T19 cells were observed in infected, compared with h ealthy animals. The proportion of leukocytes expressing surface IgM (B cells) was also elevated, although not significantly, in CAEV-infecte d compared to healthy controls. The changes in peripheral blood leukoc yte subsets in infected goats suggest that immune responses to the inf ection are probably altered in these animals with eventual. progressio n to severe disease and death. (C) 1997 Elsevier Science B.V.