In vivo T-cell subset depletion suggests that CD4(+) T-cells and a humoralimmune response are important for the elimination of orf virus from the skin of sheep
Jb. Lloyd et al., In vivo T-cell subset depletion suggests that CD4(+) T-cells and a humoralimmune response are important for the elimination of orf virus from the skin of sheep, VET IMMUNOL, 74(3-4), 2000, pp. 249-262
In vivo lymphocyte subset depletion offers a unique opportunity to study th
e roles of different cellular components of the immune system of sheep duri
ng infection with orf virus. Lambs were depleted of specific lymphocyte sub
sets by the intravenous administration of monoclonal antibodies against ovi
ne lymphocyte surface markers and then challenged with orf virus. The skin
lesions that developed were scored visually as to their severity. Blood sam
ples were collected to monitor the lymphocyte depletions and to measure orf
-virus-specific antibody levels. Skin biopsies were collected from the lesi
on site and studied to determine the course of the infection, and the prese
nce of various cell types and orf virus.
All the sheep developed orf virus lesions after infection. All three of the
CD4-depleted lambs were unable to clear virus from their skin and did not
have an antibody response to the virus. Virus was also detected in the skin
of one each of the three CD8-depleted, WC1-depleted and control sheep on t
he final day of the trial. CD8(+) lymphocytes did not appear to be essentia
l for viral clearance later in the infection. Depletion of the majority of
gamma delta(+) T-cells did not affect the outcome of orf virus infection. I
n sheep with high orf-virus-specific antibody titres at the time of infecti
on, orf lesions healed faster than lesions in sheep with low antibody level
s, and this occurred regardless of the lymphocyte depletion status of the a
nimals.
This study suggests that the presence of CD4(+) T-cells and orf-virus-speci
fic antibodies are important for the control of viral replication in the sk
in of infected sheep, (C) 2000 Elsevier Science B.V. All rights reserved.