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Journal of Clinical Microbiology, April 2003, p. 1747-1749, Vol. 41, No. 4
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.4.1747-1749.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Use of Monoclonal Antibodies to Lipopolysaccharide for Antigenic Analysis of Coxiella burnetii
Akitoyo Hotta,1 Midori Kawamura,1 Ho To,1 Masako Andoh,1 Tsuyoshi Yamaguchi,1 Hideto Fukushi,1 Ken-Ichi Amano,2 and Katsuya Hirai1*
Department of Veterinary Microbiology, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu, Gifu 501-1193,1
Central Research Laboratory, Akita University School of Medicine, 1-1-1 Hondo, Akita, Akita 010-8543, Japan2
Received 17 May 2002/
Returned for modification 29 September 2002/
Accepted 16 January 2003

ABSTRACT
Antigenic differences among
Coxiella burnetii strains were analyzed.
The monoclonal antibodies against the lipopolysaccharide outer
core did not react with the strains containing a QpRS plasmid
or with plasmidless strains, whereas they reacted with strains
containing a QpH1 or QpDV plasmid.
C. burnetii isolates could
be divided into two groups immunologically.

TEXT
Coxiella burnetii, an obligate intracellular bacterium, is the
etiologic agent of Q fever. It is widely distributed in nature
and is responsible for infection in various animals and humans
(
5,
8). Many
C. burnetii strains have been isolated from milk,
ticks, and human patients with acute and chronic Q fever. Although
all strains so far studied belong to the same serotype, it has
become apparent that
C. burnetii strains differ in their antigenic
(
3,
17) and genetic (
4,
10,
12,
18,
19) properties. The remarkable
antigenic differences among strains are due to lipopolysaccharide
(LPS) (
3). However, the components that differ among strains
have not been elucidated because the LPS ladder-like bands are
close together and share many antigenic epitopes (
9,
16). In
addition, the differences among strains are confounded by an
LPS change that occurs during serial passages in eggs or tissue
culturea process called phase variation (
8). During phase
variation, phase I cells, with full-length LPS O-chains, change
to intermediate phases with decreasing LPS O-chain lengths and
then to phase II, with truncated LPS. This LPS change is an
irreversible transition and is used as one of the criteria for
distinguishing the phase state of
C. burnetii (
11). Recently,
we analyzed this LPS change by the use of monoclonal antibodies
(MAbs) against LPS O-chains and the LPS outer core (
7). In this
report, to define the LPS component that differs among
C. burnetii strains, the reactions of the MAbs against 21 strains were analyzed.
Our results suggest that
C. burnetii strains could be divided
into two groups immunologically. This conclusion is not confounded
by the LPS change that occurs during phase variation.
C. burnetii Nine Mile strain phase I cells and 20 other strains were immunologically compared with respect to their reactivities with 10 MAbs. The name, original source, and plasmid type for each strain are listed in Table 1. Other characteristics of each strain are described elsewhere (6, 16, 17). The samples of strains KAV and PAV used were purified LPSs (2), and the samples of other strains used were prepared from whole-cell lysates by digestion with proteinase K as described previously (6). The MAbs used in this study were previously divided into three groups according to their reactions in Western blots following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) (7). The MAbs of groups I (H5A, H45, and H83) and II (H21), all of which recognize the LPS O-chains of Nine Mile strain phase I, mainly produced ladder-like bands above 20 and 15 kDa, respectively. The MAbs of group III (H73, H76, H78, H91, H99, and H100) recognized the 14-kDa LPS outer core of Nine Mile strain phase I and the Crazy variant (one of the intermediate-phase cells). None of the MAbs reacted with Nine Mile strain phase II LPS (7). SDS-PAGE was carried out by using a 15% separating gel. The LPS profiles were observed by silver staining and Western blotting as described previously (16).
The immunochemical properties of the LPSs of the 21 strains
were compared by Western blotting following SDS-PAGE. The MAbs
of groups I (H5A, H45, and H83) and II (H21) reacted with all
21 strains. Their reaction patterns were slightly different
from those against Nine Mile strain phase I. The MAbs of group
III (H73, H76, H78, H91, H99, and H100) did not react with the
KAV, PAV, Priscilla, G Q212, Ko Q229, and S Q217 strains but
reacted with the other 15 strains with a 14-kDa dense band.
The mouse antiserum against Nine Mile strain phase I cells reacted
with all strains with ladder-like bands above 14 kDa. Figure
1 shows the reaction patterns of the representative MAbs of
groups II (H21) and III (H78) against the El Tayeb, Ohio 314,
California 76, Henzerling, Bangui, MAN, ME, Ko Q229, S Q217,
and Priscilla strains. The reactions of the MAbs are summarized
in Table
2. With silver stain, all 21 strains showed ladder-like
LPS profiles (data not shown).
The reactions of the MAbs of group III, which recognized the
14-kDa LPS outer core of the Nine Mile strain, indicate that
the LPS outer cores of KAV, PAV, Priscilla, G Q212, Ko Q229,
and S Q217 differ antigenically from those of the other 15 strains
(Table
2 and Fig.
1B). This antigenic difference is not due
to the phenomenon of phase variation because the ladder-like
LPS profiles indicate that none of the strains examined are
pure phase II cells and are in good agreement with those observed
by silver staining in the study by Hackstadt (
3). This suggests
that the KAV, PAV, Priscilla, G Q212, Ko Q229, and S Q217 strains
lack the epitopes recognized by the MAbs of group III. On the
other hand, it is unclear whether the difference in the ladder-like
banding above 15 kDa is due to the phenomenon of phase variation
(Fig.
1A). The 14-kDa LPS outer-core oligosaccharide of the
Nine Mile strain contains mainly dihydrohydroxystreptose and
galactosaminuronyl-

(1-6)-glucosamine (
2) and seems to be the
dominant antigenic and immunogenic determinant (
1,
13,
14).
In
C. burnetii, these properties have been analyzed in detail
with the Nine Mile and Priscilla strains. These strains differ
in their distributions of dihydrohydroxystreptose in LPS (
15)
and their immunogenic properties and virulence to experimental
animals (
9). Considering these earlier findings, the antigenic
difference detected in this study could be related to the chemical
and immunogenic differences between the Nine Mile and Priscilla
strains. Furthermore, this antigenic difference might be related
to the virulence difference, since host immune responses are
associated with the infection of this intracellular bacterium.
It is likely that the KAV, PAV, G Q212, Ko Q229 and S Q217 strains
also differ from the Nine Mile strain in their chemical and
immunological properties and virulence. The six strains differentiated
from the other strains have similar genetic properties (QpRS
or plasmidless types) and were isolated in the same part of
the world (Canada or the United States). Therefore, the serotyping
system based on the reactions of the MAbs may be useful in diagnostic
and epidemiologic investigations of Q fever. Using this serotyping
system would allow
C. burnetii strains to be differentiated
into two antigenic groups without confusing the phenomenon of
phase variation. Further studies of the LPS outer core in a
large number of strains from various sources may help us to
understand the differences in immunogenic properties and virulence
among
C. burnetii strains.

ACKNOWLEDGMENTS
We are grateful to J. Kazar, L. P. Mallavia, and H. Nagaoka,
for their help in providing the
C. burnetii strains and purified
LPS.
This work was financially supported by Science Research Grants 07306015 and 10460140 from the Ministry of Education, Science, Sports and Culture and by Health Sciences Research grant H10-Emerg.-7 on Emerging and Re-emerging Infectious Diseases from the Ministry of Health and Welfare of Japan.

FOOTNOTES
* Corresponding author. Mailing address: Department of Veterinary Microbiology, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu, Gifu 501-1193, Japan. Phone and fax: 81-58-293-2945. E-mail:
khirai{at}cc.gifu-u.ac.jp.


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Journal of Clinical Microbiology, April 2003, p. 1747-1749, Vol. 41, No. 4
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.4.1747-1749.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
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