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Journal of Clinical Microbiology, September 1998, p. 2428-2433, Vol. 36, No. 9
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Rapid Identification of Candida
dubliniensis by Indirect Immunofluorescence Based on Differential
Localization of Antigens on C. dubliniensis Blastospores
and Candida albicans Germ Tubes
Joseba
Bikandi,1
Rosario San
Millán,1
María D.
Moragues,2
Gontzal
Cebas,1
Mary
Clarke,3
David C.
Coleman,3
Derek J.
Sullivan,3
Guillermo
Quindós,1 and
José
Pontón1,*
Departamento de Inmunología,
Microbiología y Parasitología, Facultad de Medicina y
Odontología,1 and
Departamento
de Enfermería I,2 Universidad del
País Vasco, E-48080 Bilbao, Vizcaya, Spain, and
Department of Oral Surgery, Oral Medicine and Oral Pathology,
School of Dental Science, Trinity College, University of Dublin,
Dublin 2, Republic of Ireland3
Received 9 March 1998/Returned for modification 13 May
1998/Accepted 2 June 1998
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ABSTRACT |
There is a clear need for the development of a rapid and reliable
test for the identification of Candida dubliniensis and for
the discrimination of this species from Candida albicans. In the present study we have investigated the potential use of C. dubliniensis-specific antigens as a basis for its identification. We produced an anti-C. dubliniensis serum which, after
adsorption with C. albicans blastospores, was found to
differentially label C. dubliniensis isolates in an
indirect immunofluorescence test. In this test, the antiserum reacted
with blastospores and germ tubes of C. dubliniensis and
with blastospores of Candida krusei and Rhodotorula
rubra but did not react with blastospores of several other
Candida species including C. albicans. The
antiserum also reacted with C. albicans germ tubes. The
anti-C. dubliniensis adsorbed serum reacted with specific
components of 25, 28, 37, 40, 52, and 62 kDa in the C. dubliniensis extract and with a variety of antigens from other
yeast species. The antigens from non-C. dubliniensis yeasts
showing reactivity with the anti-C. dubliniensis adsorbed
serum are mostly expressed within the cell walls of these yeast
species, and this reactivity does not interfere with the use of the
anti-C. dubliniensis adsorbed serum in an indirect immunofluorescence test for the rapid identification of C. dubliniensis.
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INTRODUCTION |
Oral candidiasis is one of the most
prevalent clinical presentations of Candida infections,
particularly in human immunodeficiency virus (HIV)-infected
individuals. Although Candida albicans remains the most
common cause of oral candidiasis, the incidence of disease caused by
other species of Candida, including Candida
krusei, Candida tropicalis, and Candida
glabrata, has been increasing steadily (4, 5). The
reason(s) for this epidemiological change is not clear; however, it has
been suggested that the reduced susceptibility of these species to
commonly used antifungal agents, such as fluconazole, may have led to
their selection. Furthermore, different groups of researchers have
reported the recovery of atypical C. albicans isolates from
HIV-infected patients (2, 10, 20, 22). Some of these
organisms have been shown to belong to a recently described species,
C. dubliniensis, which appears to be mainly associated with
oral disease in HIV-infected individuals (4, 23, 25). First
identified as a new species in Ireland in 1995, this organism has since
been identified in laboratories around the world (14, 23,
24). Although the majority of isolates so far examined have been
associated with oral candidiasis and HIV infection, isolates have also
been recovered from other anatomical sites and from healthy individuals
(4, 11, 24).
In order to investigate the significance and incidence of C. dubliniensis in clinical disease and to determine the reasons for
its recent emergence, an in-depth epidemiological analysis of this
species must be performed. However, before this can occur a rapid and
simple means of identification of C. dubliniensis must be
made available. The development of such a technique has been hampered
by the very close phenotypic and genotypic relationships between
C. dubliniensis and C. albicans (24,
25). Indeed, the close similarity between these species has led
to the misidentification of isolates of C. dubliniensis as
C. albicans (4). At present, the most accurate
means of differentiating between isolates of the two species requires
the use of molecular biology-based techniques such as DNA
fingerprinting with repetitive sequence-containing DNA probes, PCR, or
pulsed-field gel electrophoresis (3, 4, 25). However, these
techniques are not readily applicable for use with the large numbers of
isolates regularly encountered in clinical mycology laboratories.
Several phenotype-based methods for the identification of C. dubliniensis isolates have been described. The diagnostic
characteristics used in these methods include colonial coloration on
differential media, such as CHROMagar Candida, atypical carbohydrate
assimilation profiles with commercially available kits, such as the API
ID 32C system, and a lack of 
-glucosidase activity (3, 4,
24). However, there are drawbacks with many of these techniques,
since they can be unreliable and/or time-consuming (14, 21,
24). Recently, it was shown that C. dubliniensis can
be readily differentiated from C. albicans on the basis of
its inability to grow at 45°C (14). Although easy to
perform, this test requires that isolates be incubated for 24 to
48 h before the isolates can be discriminated.
In order to facilitate the development of a rapid and reliable test for
the identification of C. dubliniensis from clinical specimens, the presence of antigenic differences between C. dubliniensis and C. albicans was investigated. In this
study, a rabbit polyclonal anti-C. dubliniensis antiserum
was used to identify cell wall antigens specific for C. dubliniensis. The antigenic composition of C. dubliniensis was found to be very similar to that of C. albicans. However, the use of the anti-C. dubliniensis
antiserum adsorbed with C. albicans blastospores allowed a
clear-cut differentiation between C. dubliniensis and
C. albicans by indirect immunofluorescence.
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MATERIALS AND METHODS |
Yeast strains and clinical isolates.
The reference strains
used in this study are listed in Table 1,
and the clinical isolates of C. dubliniensis and C. albicans used in this study are listed in Table
2.
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TABLE 1.
Reference yeast strains and their reactivities by
indirect immunofluorescence with the rabbit hyperimmune serum
raised against C. dubliniensis NCPF 3949, the serum adsorbed
with C. albicansa blastospores, and the
anti-C. dubliniensis NCPF 3949 cell wall
surface-specific serum
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Culture conditions and preparation of antigens.
C.
dubliniensis and C. albicans strains were routinely
grown in medium 199 (Sigma Chemical Co., St. Louis, Mo.) as described previously (17). Briefly, 48-h-old blastospores grown at
24°C on glucose-yeast extract-agar plates were transferred to
Erlenmeyer flasks containing medium 199 at 5 × 107
blastospores/ml, and the flasks were incubated at 24°C for 18 h
in a rotary shaker set at 100 rpm. Following incubation, the blastospores were harvested by centrifugation, inoculated into fresh
medium, and incubated with shaking as before at 24°C for 24 h to
obtain blastospores. The same conditions were used to obtain
blastospores of the other yeast species studied. C. albicans germ tubes were induced by incubation of similar cultures in medium 199 at 37°C for 4 h. Since C. dubliniensis failed to
produce germ tubes under these conditions, they were obtained by
incubation in horse serum (9). The cell walls of C. dubliniensis and the other yeast species studied were extracted in
the presence of dithiothreitol (DTT; Sigma) as reported previously
(15). To obtain formalin-killed blastospores, the cells of
the different Candida species were resuspended in a 4%
(vol/vol) formaldehyde solution in phosphate-buffered saline (PBS) and
were incubated at 4°C for 18 h. Assessment of the viability of
the cells was determined by incubating the suspension on Sabouraud agar
plates (Difco, Detroit, Mich.).
Antisera.
Two separate female New Zealand White rabbits with
an initial weight of from 2 to 2.5 kg were subcutaneously inoculated
with 5 × 108 formalin-killed cells of C. dubliniensis NCPF 3949 (oral isolate and type strain)
(25) and C. dubliniensis CD57 (vaginal isolate) (11), respectively, which had been grown at 37°C and
resuspended in 0.5 ml of saline and 0.5 ml of Freund's adjuvant.
Immunizations were repeated at weekly intervals. Preimmune sera were
obtained from each rabbit before the immunization, and hyperimmune sera were obtained 5 weeks after the start of the immunization.
Aliquots of the hyperimmune anti-C. dubliniensis serum
obtained from each rabbit were each adsorbed with C. albicans NCPF 3153 blastospores by previously described methods
(17). Briefly, immune sera were mixed and incubated with an
equal volume of a formalin-killed blastospore suspension in saline
(1010 blastospores/ml) for 2 h at room temperature.
After incubation, the suspension was centrifuged and the supernatant
was recovered. This process was repeated up to three times.
Additionally, antibodies directed against C. dubliniensis
cell wall surface components were obtained by a modification of a
previously described method (15). Briefly, 0.5 ml of the
anti-C. dubliniensis NCPF 3949 serum adsorbed three times
with C. albicans blastospores was incubated with
1011 formalin-killed C. dubliniensis NCPF 3949 blastospores for 2 h at room temperature in PBS buffer. Unattached
serum proteins were removed by three washes in PBS, and the attached
antibodies were then eluted by treatment with 2.5 M NaI in PBS for
1 h at room temperature. Blastospores were harvested by
centrifugation, and the supernatant was dialyzed against PBS for
24 h at 4°C.
Immunofluorescence.
Indirect immunofluorescence assay (IFA)
was carried out as described previously (1). Briefly, the
blastospores from the different yeast species studied were grown on
Sabouraud agar plates for 48 h at 24 or 37°C, resuspended in PBS
at a cell density of 106 cells/ml, and placed on
Teflon-coated immunofluorescence slides. The slides were incubated with
the anti-C. dubliniensis serum diluted 1:5 in PBS
supplemented with Evans blue (0.05% [wt/vol]) and Tween 20 (0.05%
[vol/vol]) and washed, and the reacting antibodies were revealed by
incubation with biotin-conjugated anti-rabbit immunoglobulin G (Sigma),
followed by incubation with fluorescein isothiocyanate-conjugated
ExtrAvidin (Sigma). Slides were mounted with carbonate-glycerol
mounting fluid and examined with an epifluorescence microscope.
Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and
Western blotting.
Sodium dodecyl sulfate-polyacrylamide gel
electrophoresis of yeast cell wall extracts prepared in the presence of
DTT was performed by the method of Laemmli (8) in a minigel
system (Bio-Rad Laboratories, Richmond, Calif.). Electrophoresis was carried out in 10% (wt/vol) gels at 200 V. Subsequently, the proteins contained in the gels were electrophoretically transferred to a
nitrocellulose membrane (Bio-Rad) with a fast blot system (Biometra, Göttingen, Germany). After the transfer, the nitrocellulose
membranes were blocked in 10% (wt/vol) nonfat dry milk in
Tris-buffered saline, incubated with the anti-C.
dubliniensis sera, and finally incubated again with
peroxidase-conjugated anti-rabbit immunoglobulin G antibodies (Sigma).
Immunoreactive bands were visualized with 4-chloro-1-naphthol by
standard procedures.
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RESULTS |
Reactivities of the anti-C. dubliniensis sera by
indirect immunofluorescence.
The reactivities of the preimmune
sera and the hyperimmune antisera from rabbits immunized with C. dubliniensis NCPF 3949 and C. dubliniensis CD57 were
first studied by IFA with reference strains of different yeast species,
including several Candida species, Trichosporon
beigelii, Saccharomyces cerevisiae,
Cryptococcus neoformans, and Rhodotorula
rubra (Table 1). The reactivities of the preimmune sera with
the Candida species studied were negative. In preliminary
experiments, both hyperimmune antisera gave identical results and the
antiserum against C. dubliniensis NCPF 3949 was selected for
further studies. The unadsorbed antiserum reacted with all the yeast
species studied, showing a homogeneous reactivity. The reactivity of
the anti-C. dubliniensis serum adsorbed with formalin-killed
C. albicans NCPF 3153 blastospores was initially studied
with cells grown at 37°C on Sabouraud agar. With this culture medium,
all species studied grew as blastospores and the antiserum reacted only
with C. dubliniensis, C. krusei, and R. rubra. The expression of antigens reacting with the anti-C.
dubliniensis adsorbed serum in the C. dubliniensis and
R. rubra strains studied (Table 1) was homogeneous, and most
cells showed fluorescence (Fig. 1).
However, the reactivity of the adsorbed antiserum with the C. krusei strains studied (Table 1) was very heterogeneous, with only
10% of the cells showing reactivity (Fig. 1).
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FIG. 1.
Immunofluorescence photographs of C. dubliniensis NCPF 3949 blastospores (a) and germ tubes (d) stained
with the anti-C. dubliniensis adsorbed serum.
Immunofluorescence (b and c) and phase-contrast (e and f) photographs,
respectively, of the same microscopic fields, show C. krusei
NCPF 3100 blastospores (b and e) and C. albicans NCPF 3153 germ tubes (c and f) stained with the anti-C. dubliniensis
adsorbed serum. Magnification, ×1,000.
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When the yeast species studied (Table
1) were grown at 37°C in medium
199, all species except
C. albicans grew as blastospores.
C. albicans strains produced a mixture of blastospores and
germ
tubes. Since the
C. dubliniensis strains examined did
not produce
germ tubes in medium 199, these were obtained by incubation
in
horse serum. The adsorbed antiserum reacted with blastospores
of
C. dubliniensis,
C. krusei, and
R. rubra as well as with
C. dubliniensis and
C. albicans germ tubes (Fig.
1). Despite the
reactivity of
C. albicans germ tubes with the anti-
C. dubliniensis adsorbed serum, the blastospores attached to them remained negative.
Adsorption of the anti-
C. dubliniensis antiserum with
C. albicans germ tubes resulted in a loss of its reactivity
with
C. dubliniensis.
The anti-
C. dubliniensis
cell wall surface-specific serum showed
a reactivity by IFA identical
to that shown by the anti-
C. dubliniensis adsorbed serum
(Table
1).
The ability of the anti-
C. dubliniensis adsorbed serum to
differentiate clinical isolates of
C. dubliniensis from
clinical
isolates of
C. albicans by IFA was also confirmed
with a group
of 83
C. dubliniensis and 44
C. albicans isolates (Table
2).
These isolates were recovered mainly
from the oral cavities of
patients from disparate geographical
locations and had been identified
by both phenotypic and genotypic
methods (
23,
25). A number
of isolates from nonoral sources
were also studied (Table
2).
The antiserum allowed the rapid and
precise discrimination of
the isolates, since all of the
C. dubliniensis isolates were positive
by immunofluorescence assays
with the antiserum, while all of
the
C. albicans isolates
were negative.
Identification of C. dubliniensis antigens reactive
with the anti-C. dubliniensis serum.
By
immunoblotting, the unadsorbed anti-C. dubliniensis serum
reacted with antigens in DTT extracts from both C. dubliniensis NCPF 3949 and C. albicans NCPF 3153 strains spanning a wide range of molecular weights (Fig.
2A). Most antigenic components present in
the extracts from both species had similar molecular masses, although
differences in banding intensity were observed for some components.
Despite the common reactivity observed between C. dubliniensis and C. albicans, the antiserum reacted
with three components of 25, 35, and 50 kDa in the C. albicans extract which were not observed in the C. dubliniensis extract, while the C. dubliniensis extract
contained 52- and 62-kDa components which were not observed in the
C. albicans extract. The unadsorbed antiserum also reacted
with a variety of components in cell wall extracts from the rest of the
yeast species studied (data not shown).
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FIG. 2.
Western blots of 10% slab gels loaded with extracts
from C. dubliniensis NCPF 3949 blastospores grown at 37°C
(lanes A1 and B2) or 24°C (lane B1) and C. albicans NCPF
3153 germ tubes (lanes A2 and B4) or blastospores (lane B3) stained
with the anti-C. dubliniensis serum (A) or with the
anti-C. dubliniensis adsorbed serum (B). The molecular
masses of standard proteins (in kilodaltons) are listed to the left of
the gels. Relevant antigenic bands are indicated by arrowheads.
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After the adsorption with
C. albicans blastospores, the
anti-
C. dubliniensis serum showed a decrease in reactivity
with components
in the
C. albicans extract but not with
components in the
C. dubliniensis extract (Fig.
2B). The
adsorbed antiserum showed a higher reactivity
with extracts from both
C. dubliniensis NCPF 3949 and
C. albicans NCPF
3153 cells grown at 37°C than with extracts from the cells
grown at
24°C. Furthermore, the adsorbed antiserum stained several
components
of 25, 28, 37, 40, 52, and 62 kDa in the
C. dubliniensis extracts which were not stained in the
C. albicans extracts.
In
contrast, a component of 35 kDa present in the
C. albicans extracts
was not observed in the extracts from
C. dubliniensis cells grown
at both 24 and 37°C. Similar results
were observed when extracts
from
C. dubliniensis CD57 and
C. albicans ATCC 60458 were examined
(data not shown).
The anti-
C. dubliniensis adsorbed serum also reacted by
immunoblotting with antigens from other yeast species (Fig.
3). Major
antigens comprised a 66-kDa
component in the
C. krusei NCPF 3100
extract, a 47-kDa
component in the
C. tropicalis NCPF 3111 extract,
several
components ranging between 29 and 68 kDa in the
Candida parapsilosis NCPF 3104 extract, two components of 66 and 68 kDa
in
the
Candida guilliermondii NCPF 3099 extract, a component of
67 kDa in the
C. glabrata NCPF 3203 extract, and several
components
with molecular masses of >40 kDa in the
R. rubra
UPV94921 extract.
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FIG. 3.
Western blots of 10% slab gels loaded with extracts
from C. krusei NCPF 3100 (lane 1), C. tropicalis
NCPF 3111 (lane 2), C. parapsilosis NCPF 3104 (lane 3),
C. guilliermondii NCPF 3099 (lane 4), C. glabrata
NCPF 3203 (lane 5), and R. rubra UPV94921 (lane 6) stained
with the anti-C. dubliniensis adsorbed serum. The molecular
masses of standard proteins (in kilodaltons) are listed to the left of
the gel.
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Identification of C. dubliniensis antigens reactive
with the anti-C. dubliniensis cell wall surface-specific
serum.
In order to identify the antigens from the cell wall
surface responsible for the fluorescence observed on the C. dubliniensis cells, the reactivity of an anti-C.
dubliniensis cell wall surface-specific serum was studied by
immunoblotting with cell wall extracts from C. dubliniensis,
C. albicans, C. krusei, and R. rubra.
The anti-C. dubliniensis cell wall surface-specific serum
reacted with a component of 33 kDa in the extract from C. dubliniensis cells grown at 24°C and with components of 32 and
77 kDa in the extract from C. dubliniensis cells grown at
37°C (Fig. 4). This antiserum also
stained four components of 33, 70, 74, 77, and 180 kDa in the C. albicans blastospore extract and with components of 33, 74, 77, and >200 kDa in the C. albicans germ tube extract. The
anti-C. dubliniensis cell wall surface-specific serum also
stained a component of 30 kDa in the C. krusei NCPF 3100 extract and several components ranging from 43 to 100 kDa in the
R. rubra UPV94921 extract. In one experiment, the
anti-C. dubliniensis cell wall surface-specific serum was diluted in order to identify the most reactive components present in
the extracts. Under these conditions, only the component of 33 kDa
present in the C. dubliniensis NCPF 3949 extract and the components ranging from 60 to 100 kDa present in the R. rubra UPV94921 extract were stained (data not shown).
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FIG. 4.
Western blots of 10% (wt/vol) acrylamide slab gels
loaded with extracts from C. dubliniensis NCPF 3949 grown at
24°C (lane 1) and 37°C (lane 2), C. albicans NCPF 3153 grown at 24°C (lane 3) and 37°C (lane 4), C. krusei NCPF
3100 (lane 5), and R. rubra UPV94921 (lane 6) stained with
the anti-C. dubliniensis cell wall surface-specific serum.
The molecular masses of standard proteins (in kilodaltons) are listed
to the left of the gel.
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DISCUSSION |
Because species of Candida other than C. albicans continue to be recovered from patients with infection
with increasing frequency, it is clear that routine diagnostic
laboratories should be in a position to identify these species rapidly
and accurately. Precise identification of these species will allow
epidemiological studies to be conducted and may be of benefit in
selecting the most effective therapies (12, 13). However,
Candida species identification can be time-consuming and
inaccurate. This is further complicated by the many anomalies in
candidal classification (4), particularly with the recent
identification of new Candida species such as C. dubliniensis and C. fermentatii (19, 25). As
far as possible, species identification techniques should be easy to
perform, rapid, reliable, inexpensive, and applicable to a large volume
of isolates. In this study, we attempted to develop such a
technique for the identification of clinical C. dubliniensis isolates. Reliable phenotypic identification of
C. dubliniensis has proved to be problematic (21,
24). Although C. dubliniensis and C. albicans are readily distinguishable at the genetic level,
the techniques capable of detecting the discriminatory differences are
not easily applicable to the large numbers of isolates tested
routinely in clinical mycology laboratories. Furthermore, the
phenotypic similarities of the two species, including the ability
to produce germ tubes and chlamydospores, has hampered the development
of a rapid phenotypic test that can discriminate between isolates of
both species (24).
In this paper, we present evidence, for the first time, of the
existence of antigenic differences between C. dubliniensis and C. albicans, thus providing the basis for the
development of a rapid identification test. Anti-C.
dubliniensis sera were raised in rabbits by inoculation with
formalin-killed strains of C. dubliniensis. In order to
remove antibodies raised against common antigens present on the cell
wall surfaces of C. dubliniensis and C. albicans,
the antisera were adsorbed with C. albicans blastospores, a
technique originally used by Hasenclever and Mitchell (7) to
identify the existence of two serotypes in C. albicans.
These adsorbed sera were then investigated for their ability to
identify C. dubliniensis in indirect immunofluorescence
experiments.
The IFA developed with the anti-C. dubliniensis adsorbed
serum takes less than 2 h to perform and correctly identified the C. dubliniensis reference strains NCPF 3949 and CD57 and a
further 83 clinical isolates of C. dubliniensis which had
been identified previously by both phenotypic and genotypic methods. In
all cases, most cells showed fluorescence on the entire cell wall,
although differences in reactivity were observed among C. dubliniensis isolates. This antiserum showed no indirect
immunofluorescence with blastospores of species closely related to
C. dubliniensis, such as C. albicans,
Candida stellatoidea type I, C. stellatoidea type
II, and C. tropicalis. However, the anti-C.
dubliniensis adsorbed serum reacted with R. rubra and
C. krusei, the latter showing a heterogeneous reactivity
with only 10% of the cells being positive. The reactivity with the
anti-C. dubliniensis adsorbed serum shown by C. krusei and R. rubra is not likely to be an important problem when identifying C. dubliniensis by indirect
immunofluorescence, since R. rubra has a distinctive colony
color on conventional mycological media and C. krusei can be
easily differentiated from C. dubliniensis by the
conventional identification methods used in the clinical microbiology
laboratory such as the germ tube or Krusei color tests (6,
9) as well as by growth on CHROMagar Candida medium
(18).
The anti-C. dubliniensis adsorbed serum was also used to
identify the antigens responsible for the fluorescence observed on the
C. dubliniensis cell wall and to study the presence of
similar antigens in the cell walls of other yeasts. This antiserum
reacted with several cell wall components with molecular masses ranging from 25 to 77 kDa, and when compared with the reactivity observed in
the C. albicans extract, some of them seemed to be present only in the C. dubliniensis extract. Some of the components
stained by the anti-C. dubliniensis adsorbed serum in the
C. dubliniensis extract are likely to be located on the
C. dubliniensis cell wall surface since they were stained
with an anti-C. dubliniensis cell wall surface-specific
serum. Among these antigens, the component of 33 kDa seems to be the
most reactive with the anti-C. dubliniensis cell wall
surface-specific serum, and it may be a good candidate for use in the
production of monoclonal antibodies to be used in the identification of
C. dubliniensis.
In addition to the reactivity observed with C. dubliniensis,
the anti-C. dubliniensis adsorbed serum also reacted with
other yeast species. On the basis of their reactivities by both
indirect immunofluorescence and Western blotting, we can speculate
about the distribution of the antigens in the cell wall. Since C. albicans blastospores did not react by indirect immunofluorescence
with either the anti-C. dubliniensis adsorbed serum or the
anti-C. dubliniensis cell wall surface-specific serum, the
antigenic bands observed by Western blotting in the extract from
C. albicans blastospores stained with these antisera must be
located in the inner layers of the cell wall. However, the antigen of
>200 kDa observed in the C. albicans germ tube extracts is
likely to be located on the germ tube cell wall surface since the cell
wall of C. albicans germ tubes is stained by
indirect immunofluorescence with the anti-C.
dubliniensis adsorbed serum and the adsorption of the anti-C. dubliniensis antiserum with C. albicans
germ tubes abolishes the reactivity of this antiserum with C. dubliniensis. The distribution of this antigen in the cell wall of
C. albicans is in agreement with that shown by the
previously described type I antigens, which are specifically expressed
on the germ tube cell wall surface (16). The component of 30 kDa and several components ranging from 43 to 100 kDa are likely to be
located on the cell wall surface of C. krusei and R. rubra, respectively, while the components from C. tropicalis, C. parapsilosis, C. guilliermondii, and C. glabrata extracts reacting with
the anti-C. dubliniensis adsorbed serum are located within
the cell wall.
In conclusion, our results indicate that C. dubliniensis and
C. albicans share a group of cell wall antigens and that a
specific anti-C. dubliniensis serum can be prepared after
removal of the antibodies against the common antigens present on the
cell wall surfaces of both species. The adsorbed anti-C.
dubliniensis serum reacts with several components expressed
specifically on the C. dubliniensis cell wall surface. These
antigens or other antigens showing cross-reactivity with them are
expressed on the cell walls of other Candida species and
R. rubra, but this reactivity does not interfere with the
use of the anti-C. dubliniensis adsorbed serum in an
indirect immunofluorescence test for the rapid identification of
C. dubliniensis.
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ACKNOWLEDGMENTS |
Research performed in Bilbao was supported by grant UPV
093.327-eb131/96 from the Universidad del País Vasco and grant
EX97/4 from the Departamento de Educación, Universidades e
Investigación del Gobierno Vasco. Research performed in Dublin
was supported by Irish Health Research Board grant 41/96 and by the
School of Dental Science, Trinity College, Dublin.
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FOOTNOTES |
*
Corresponding author. Mailing address: Departamento de
Inmunología, Microbiología y Parasitología,
Facultad de Medicina y Odontología, Universidad del
País Vasco, Apartado 699, E-48080 Bilbao, Vizcaya, Spain.
Phone: 4 464 7700, ext. 2746. Fax: 4 464 9266. E-mail:
oipposaj{at}lg.ehu.es.
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Journal of Clinical Microbiology, September 1998, p. 2428-2433, Vol. 36, No. 9
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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Abstract
Introduction
