Wc. Brown et al., DNA AND A CPG OLIGONUCLEOTIDE DERIVED FROM BABESIA-BOVIS ARE MITOGENIC FOR BOVINE B-CELLS, Infection and immunity (Print), 66(11), 1998, pp. 5423-5432
DNAs from bacteria and variety of nonvertebrate organisms, including n
ematodes, mollusks, yeasts, and insects, cause polyclonal activation o
f murine: B lymphocytes, Similar studies have not been reported for bo
vine B cells, and to date no studies have reported mitogenic propertie
s of protozoal DNA for any species. However, we and others have observ
ed that protozoal parasite antigens can induce the proliferation of ly
mphocytes from nonexposed donors. Extending these studies, we now show
that the mitogenic property of protozoal antigen preparations is in p
art attributable to parasite DNA and that Babesia bovis DNA is directl
y mitogenic for bovine B cells, DNase treatment of B. bovis extracts a
brogated B. bovis-induced proliferation of peripheral blood mononuclea
r cells from nonexposed cattle. Like DNAs from other organisms that we
re mitogenic for murine B cells, B, bovis DNA is largely nonmethylated
and induced a dose-dependent proliferation of bovine B cells, which w
as reduced upon methylation, Furthermore, B. bovis and E. coil DNAs en
hanced immunoglobulin secretion by cultured B cells, inducing moderate
increases in immunoglobulin GI and stronger increases in immunoglobul
in G2, Because certain nonmethylated CpG motifs present in bacterial D
NA are known to stimulate proliferation of murine and human B cells, i
n Il-kb fragment of B. bovis DNA was analyzed for CG dinucleotide cont
ent and for the presence of known immunostimulatory sequences (ISS) ce
ntered on a CG moth, The frequency of CG dinucleotides was approximate
ly one-half of the expected frequency, and several CpG hexameric seque
nces with known activity for murine B cells were identified. An oligod
eoxynucleotide containing one of these ISS (AACGTT), which: is present
within the rhoptry-associated protein-1 (rap-1) open reading frame, w
as shown to stimulate B-cell proliferation, These ISS may be involved
in host immune modulation during protozoal infection and may be useful
as vaccine adjuvants.