INFECTION AND IMMUNITY, Feb. 2007, p. 766–773
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
Vol. 75, No. 2
Characterization of the Outer Membrane Proteome of
Leptospira interrogans Expressed during Acute
Jarlath E. Nally,1* Julian P. Whitelegge,2,3Sara Bassilian,2,3David R. Blanco,1and Michael A. Lovett1
Division of Infectious Diseases, Department of Medicine,1The Pasarow Mass Spectrometry Laboratory,2and The Jane and
Terry Semel Institute for Neuroscience and Human Behavior,3David Geffen School of Medicine, University of
California Los Angeles, Los Angeles, California
Received 9 May 2006/Returned for modification 1 June 2006/Accepted 30 October 2006
Pathogenic Leptospira species adapt to a wide range of environmental conditions during disease transmis-
sion and infection. While the proteome of in vitro cultivated Leptospira has been characterized in several
studies to date, relatively little is known of the proteome as expressed by Leptospira during disease processes.
Isolates of Leptospira obtained from patients suffering the severe pulmonary form of leptospirosis cause acute
lethal infection in guinea pigs and chronic asymptomatic infection in rats. Recent studies have demonstrated
that protein and lipopolysaccharide constituents of Leptospira recovered from acutely infected guinea pig tissue
differ from that of Leptospira in chronically infected rat tissue and in vitro cultivated Leptospira (J. E. Nally,
E. Chow, M. C. Fishbein, D. R. Blanco, and M. A. Lovett, Infect. Immun. 73:3251–3260, 2005). In the current
study, the proteome of Leptospira expressed during disease processes was characterized relative to that of in
vitro cultivated Leptospira (IVCL) after enrichment for hydrophobic membrane proteins with Triton X-114.
Protein samples were separated by two-dimensional gel electrophoresis, and antigens expressed during infec-
tion were identified by immunoblotting with monospecific antiserum and convalescent rat serum in addition
to mass spectrometry. Results suggest a significant increase in the expression of the outer membrane protein
Loa22 during acute infection of guinea pigs relative to other outer membrane proteins, whose expression is
generally diminished relative to expression in IVCL. Significant amounts of LipL32 are also expressed by
Leptospira during acute infection of guinea pigs.
Pathogenic species of Leptospira cause the global zoonotic
disease leptospirosis. Chronically infected domestic and wild
animal species harbor in their renal tubules Leptospira which is
shed into the environment upon urination. Excreted Leptospira
continues to survive in suitable moist environments until con-
tact and penetration of new hosts via skin abrasions or mucosal
surfaces such as conjunctival tissue of the eye (1, 4).
Dissemination of Leptospira organisms throughout the in-
fected host can result in a wide range of clinical manifestations
of disease, ranging from a self-limiting fever to acute lethal
forms to asymptomatic chronic carriage. The severe pulmonary
form of leptospirosis (SFPL) results in high mortality rates (18,
20, 21, 23–25). Isolates of Leptospira recovered from patients
suffering from SPFL have been used to develop acute and
chronic experimental animal models of disease (13, 14). Ex-
perimental infection of guinea pigs emulates the acute lethal
form of the disease with pulmonary hemorrhage, as observed
in human patients suffering SPFL. While few Leptospira organ-
isms were found in infected guinea pig lung tissue, large num-
bers were present in liver, kidney, spleen, and intestines (13).
In contrast, experimental infection of rats results in an asymp-
tomatic chronic infection with Leptospira organisms shed in
urine, thus reproducing the natural mode of transmission of
the disease (14).
We have previously reported the development of techniques
to extract intact, motile Leptospira organisms from infected
animal tissue (14). Characterization of Leptospira organisms
recovered from infected host tissue (host tissue Leptospira, or
HTL) indicated that the lipopolysaccharide O-antigen content
of leptospires in guinea pig liver was markedly reduced com-
pared to that of organisms found in rat renal tubules or culti-
vated in vitro (14). Thus, there is an association between di-
minished O-antigen content and acute lethal infection, while
O-antigen content during renal tubular colonization approxi-
mates that of in vitro cultivated leptospires.
In this report, we present an approach to characterize pro-
teins of Leptospira expressed during relevant disease processes
compared to those expressed during in vitro growth.
MATERIALS AND METHODS
Bacteria. An isolate of Leptospira interrogans serovar Copenhageni, designated
RJ16441, was obtained from blood cultures of a patient suffering from the severe
pulmonary form of leptospirosis who was admitted to Antonio Pedro University
Hospital, Rio de Janeiro, Brazil (13, 23). Cultures were maintained in Elling-
hausen-McCullough-Johnson-Harris (EMJH) liquid (Becton Dickinson, MD) or
EMJH semisolid medium (EMJH liquid medium containing 0.2% noble agar).
Isolates were passaged through guinea pigs to maintain virulence as previously
Animals. Hartley male guinea pigs (Charles River Laboratories, Kingston,
NY), 12 to 15 days of age and weighing 200 g, were injected intraperitoneally
with 105cells of low-passage RJ16441 in a final volume of 500 ?l as previously
described (13). Sprague-Dawley rats (Charles River Laboratories, Kingston,
NY), ?6 weeks of age and weighing 130 to 150 g, were injected intraperitoneally
* Corresponding author. Present address: School of Agriculture,
Food Science and Veterinary Medicine, Veterinary Sciences Centre,
University College Dublin, Belfield, Dublin 4, Ireland. Phone: 353 1
716 6182. Fax: 353 1 716 6185. E-mail: Jarlath.Nally@ucd.ie.
?Published ahead of print on 13 November 2006.
with 107cells of low-passage RJ16441 in a final volume of 500 ?l as previously
described (14). Negative-control animals were injected with EMJH medium
alone. Animals were monitored daily for signs of illness including weight loss and
loss of mobility. Guinea pigs were euthanized on day 5 or 6. All animal studies
were approved by the Animal Research Committee of the University of Califor-
nia Los Angeles.
Purification of Leptospira from infected guinea pig liver. Intact motile Lepto-
spira organisms were extracted from infected guinea pig liver over Percoll density
gradients as previously described (14).
Triton X-114 extraction of Leptospira organisms. In vitro cultivated Leptospira
(IVCL) or Percoll-purified Leptospira organisms from infected guinea pig liver
(HTL)were extracted with Triton X-114 (TX-114) (Sigma) as previously de-
scribed (14). The Percoll-purified HTL fraction was diluted 1:8 in phosphate-
buffered saline before extraction with TX-114 to dilute the gradient in the
Gel electrophoresis and immunoblotting. Two-dimensional (2-D) gel electro-
phoresis was performed from pH 3 to 10 and from pH 4 to 7, as previously
described (16). Total protein of 2-D gels was visualized after staining with Deep
Purple (Amersham Biosciences) as per the manufacturer’s instructions. For
immunoblotting, samples were transferred to Immobilon-P transfer membrane
(Millipore, Bedford, MA) and blocked with 5% (wt/vol) nonfat dry milk in
phosphate-buffered saline–0.1% Tween 20. Membranes were individually incu-
bated with indicated antisera for 1 h at indicated concentrations (chronic rat
serum, 1:1,000; anti-outer membrane vesicle [OMV], 1:2,000; anti-OmpL1,
1:4,000; anti-LipL32, 1:5,000; anti-LipL21, 1:4,000; anti-LipL41, 1:4,000; and
anti-LipL31, 1:2,500), followed by incubation with appropriate secondary anti-
bodies: horseradish-peroxidase donkey anti-rabbit immunoglobulin G (IgG) con-
jugate (1:2,500; Amersham Biosciences, Piscataway, NJ), horseradish-peroxidase
goat anti-rat IgG conjugate (1:2,000; Amersham Biosciences, Piscataway, NJ), or
horseradish-peroxidase sheep anti-mouse IgG conjugate (1:2,500; Amersham
Biosciences, Piscataway, NJ). Bound conjugates were detected with SuperSignal
West Dura extended duration substrate (Pierce Biotechnology Inc., Rockford,
IL). Since different proteins have different levels of antigenicity with each serum,
optimal protein amounts for immunoblotting were determined to facilitate the
identification of as many antigens as possible; 2 ?g (see Fig. 2 and 3) or 4 ?g (see
Fig. 4) of processed IVCL cells was used for each immunoblot, and 8 ?g (see Fig.
2 and 3) or 16 ?g (see Fig. 4) of processed HTL cells was used for each
immunoblot. Predicted molecular masses and isoelectric points of mature pro-
teins described in results were based on submission of the amino acid sequences
(without signal peptide) to ExPASy (http://au.expasy.org/tools/pi_tool.html).
Analysis of tryptic peptide sequence tags by micro-liquid chromatography
MS/MS. Protein spots in 2-D gels identified by total protein staining were excised
and digested with trypsin for analysis by mass spectrometry as previously de-
scribed (16). Samples were analyzed by micro-liquid chromatography tandem
mass spectrometry (MS/MS) with data-dependent acquisition (Q STAR XL;
Applied Biosystems, Foster City, CA) after dissolution in 10 ?l of 0.1% formic
acid–5% acetonitrile (vol/vol). A reverse-phase PLRP-S column (200 ?m by 10
cm, 5 ?m, 300 Å; Michrom Biosciences, San Jose, CA) was equilibrated for 20
min at 2 ?l/min with 100% eluent A (0.1% formic acid, 5% acetontrile in water)
prior to sample injection (5 ?l). A compound linear gradient was initiated 3 min
after sample injection ramping to 80% eluent A and 20% eluent B (0.1% formic
acid in acetonitrile) at 8 min; 65% A and 35% B at 13 min; 25% A and 75% B
at 23 min, and 90% A and 10% B at 23.1 min. Column eluent was directed to a
stainless steel nano-electrospray emitter (ES301; Proxeon, Odense, Denmark) at
4.4 kV for ionization without nebulizer gas. The mass spectrometer was operated
in the IDA (information dependent acquisition) mode with a survey scan (400 to
1,500 m/z), data-dependent MS/MS on the two most abundant ions with exclu-
sion after two MS/MS experiments. Individual sequencing experiments were
matched to either a custom L. interrogans serovar Copenhageni strain Fiocruz
L1-130 sequence database downloaded from NCBI (www.ncbi.nlm.nih.gov) (19)
or to the global mass spectrometry database provided at the Matrix Science
server using Mascot software (http://www.matrixscience.com; Matrix Sciences,
London, United Kingdom). The search was run under the mode “no enzyme” to
identify semi- and nontryptic peptides. MS/MS spectra matched to peptide se-
quences with Mascot scores exceeding 30 were examined manually, specifically
with respect to calculated parent and product ion mass accuracy as well as to
whether the return was fully or partially tryptic. Where two or more peptides
were matched reliably, a strong hit was reported. Where a single good quality
peptide hit was returned, a potential hit was reported. The mass spectral data
were interpreted without knowledge of the isoelectric points or molecular masses
predicted from the 2-D analysis.
Identification of TX-114-extracted proteins of IVCL by mass
spectrometry. Fractions of IVCL enriched for hydrophobic
membrane proteins were separated by 2-D gel electrophoresis
and visualized by staining with Deep Purple, (Fig. 1). Table 1
provides a list of those proteins in Fig. 1 that were excised and
identified by mass spectrometry. In addition to several known
outer membrane proteins, including LigA, OmpL1, LipL41,
LipL21, LipL36, LipL32 (also known as Hap-1), LipL31, and
Qlp42 (also known as LipL45), several additional proteins
were identified that confirm annotation of the completed ge-
nomes of Leptospira and confirm the expression of these pro-
teins during in vitro culture. These include a putative outer
membrane protein (spot number 2), four putative lipoproteins
(spot numbers 4, 6, 14, 15, and 23) in addition to the annotated
lipoprotein LipL71 (spot number 16), two conserved hypothet-
ical proteins (spot numbers 17, 18, and 24), two outer mem-
brane efflux proteins (spot numbers 25 to 28), a penicillin G
acylase precursor (spot number 22), and a carboxy-terminal
processing protease precursor (spot numbers 19 to 21). Not all
proteins were amenable to identification by mass spectrometry,
as previously discussed (16).
Identification of antigens expressed in IVCL and HTL using
monospecific antiserum. Since several proteins of the outer
membrane of in vitro cultivated Leptospira have been identi-
fied and characterized at the molecular level, including
OmpL1, LipL41, LipL21, Loa22, LipL32, LipL31, and Qlp42
(3, 5, 6, 8, 10–12, 22), immunoblots of TX-114-extracted IVCL
and HTL samples were probed with monospecific antiserum to
determine whether these proteins were expressed during acute
infection of guinea pigs (Fig. 2).
Immunoblot analysis with anti-OmpL1 indicated that
OmpL1, an outer membrane porin of Leptospira (31.06 kDa;
pI 7.9) is expressed in both IVCL and HTL. Expression of both
LipL41 (36.82 kDa; pI 6.0) and LipL21 (17.83 kDa; pI 6.5),
FIG. 1. Total protein staining of TX-114-extracted IVCL sample
separated by 2-D gel electrophoresis, pH 3 to 10. Protein spots excised
for identification by mass spectrometry are indicated and correspond
to identifications presented in Table 1. Molecular mass markers (kDa)
are provided on the left.
VOL. 75, 2007THE IN VIVO PROTEOME OF LEPTOSPIRA767
surface-exposed lipoproteins, is detected in IVCL and HTL.
Loa22, a surface-exposed lipoprotein (18.73 kDa, pI 6.83), is
also expressed in IVCL and HTL, but larger levels of Loa22
are detected in HTL compared to IVCL, relative to an appar-
ent diminution in levels of OmpL1, LipL41, and LipL21.
LipL32 has a predicted mass of 27.654 kDa and a pI of 5.74
although actual mass ranges from 28.47 to 28.58 kDa due to
the presence of lipoforms (16). LipL32 is detected in both
IVCL and HTL (Fig. 2). In addition, anti-LipL32 is reactive
with lower-molecular-mass antigens, indicating the presence of
lower mass products of LipL32 in each sample. Interestingly,
the lower-molecular-mass products reactive in IVCL are dif-
ferent from lower-molecular-mass products detected in HTL.
Overall, and relative to an apparent diminution of expression
by OmpL1, LipL41, and LipL21, LipL32 is easily detected in
HTL samples at levels comparable to those detected in IVCL
In order to provide improved resolution of LipL32 and the
antigens which have a molecular mass and pI similar to that of
LipL32, immunoblot assays were also performed over a pH
range of 4 to 7 (Fig. 3). LipL31, a cytoplasmic membrane
lipoprotein (25.45 kDa; pI 5.92) was detected in IVCL and
HTL. While Qlp42 has a predicted mass of 39.8 kDa and pI of
6.1, it is actually detected as two proteins with masses of 28.41
and 26.46 kDa (11, 12). Immunoblotting confirmed the expres-
sion of Qlp42 in IVCL but not in HTL at this level of detection.
TABLE 1. TX-114-extracted proteins of L. interrogans serovar Copenhageni identified by mass spectrometry from Fig. 1a
Spot no.TIGR locus TIGR annotationMass pIScoreNo. of peptides
Putative outer membrane protein
6 NT03LI0010 Putative lipoprotein27700.76 6.7327
7 NT03LI1637LipL32 29612.886.80728
8 NT03LI1763 LipL3127620.737.345443
Conserved hypothetical protein
Conserved hypothetical protein
Carboxy-terminal processing protease precursor
Carboxy-terminal processing protease precursor
Carboxy-terminal processing protease precursor
Penicillin G acylase precursor
Conserved hypothetical protein
Outer membrane efflux protein
Outer membrane efflux protein
Outer membrane efflux protein
Outer membrane efflux protein
aProteins of TX-114-extracted IVCL identified by mass spectrometry. Spot numbers correspond to those shown in Fig. 1. Locus, annotation, mass, and isoelectric
point information is as provided by The Institute for Genomic Research based on the annotation of L. interrogans Copenhageni Fiocruz L1-130 (http://www.tigr.org
/tigr-scripts/CMR2/GenomePage3.spl?database?ntli03). A Mascot search score of mass spectrometry results is also provided, as is the number of peptides used to
provide the score.
768 NALLY ET AL.INFECT. IMMUN.
Identification of antigens expressed in IVCL and HTL using
chronic rat serum and anti-OMV serum. TX-114-extracted
antigens from HTL and IVCL samples were detected with
serum from chronically infected rats (chronic rat serum [CRS])
(14) or with serum raised against OMVs prepared from IVCL
(16). Alignment of immunoblots of TX-114-extracted HTL
samples with immunoblots of TX-114-extracted IVCL samples
indicated that both CRS and anti-OMV serum recognize an-
tigens expressed by both IVCL and HTL, as shown in Fig. 4.
However, several antigens are differentially expressed in IVCL
and HTL sample preparations.
Alignment of immunoblots in Fig. 4 with those in Fig. 2
confirms the identity of LipL41, LipL21, LipL32, and Loa22
proteins as antigens reactive with CRS and anti-OMV serum.
However, it was also noted that CRS and anti-OMV, at the
level of detection presented in Fig. 1, do not react with a
protein of similar mass and pI to OmpL1. As shown in Fig. 2,
larger levels of Loa22 are detected with CRS in HTL com-
FIG. 2. Two-dimensional immunoblots, pH 3 to 10, of TX-114-extracted IVCL (2 ?g) or HTL (8 ?g) sample. Samples were probed with
monospecific antiserum specific for OmpL1, LipL41, LipL21, Loa22, and LipL32. Molecular mass markers (kDa) are provided on the left.
VOL. 75, 2007 THE IN VIVO PROTEOME OF LEPTOSPIRA769
pared to IVCL (Fig. 4). Similarly, LipL32 is readily detected in
HTL and IVCL relative to apparently diminished levels of
LipL21 and LipL41. Further, the lower-molecular-mass prod-
ucts of LipL32 shown in Fig. 2 correspond in mass and pI
to lower-molecular-mass antigens reactive with CRS and
To identify antigens of IVCL and HTL samples that were
reactive with CRS and anti-OMV, but not with serum against
known outer membrane proteins, immunoblots with CRS and
anti-OMV (Fig. 4) were aligned with total protein stains of
IVCL (Fig. 1). This allowed for the excision of protein spots
with the same molecular mass and pI values as antigens rec-
ognized by CRS and anti-OMV and their identification by
mass spectrometry. This approach was also used to corrobo-
rate the identity of the antigens identified by immunoblotting
with monospecific antiserum.
Immunoblots of TX-114-extracted IVCL and HTL with an-
tiserum specific for LigA, a putative lipoprotein (126.4 kDa; pI
6.26), were inconclusive for detection of LigA expression in
2-D immunoblot analysis (data not shown). However, mass
spectrometry provided conclusive evidence for its presence in
the TX-114 detergent phase of IVCL (spot number 29). LigA
of IVCL was highly reactive with CRS (Fig. 4), confirming
expression during in vitro growth and chronic infection of rats.
LigA of HTL was also reactive with CRS, though to a lesser
extent than that detected in IVCL and relative to the amounts
loaded for each sample.
Additional antigens reactive with OMV that were identified
6) and the conserved hypothetical protein NT03LIA0039 (Fig. 1,
spot numbers 17 and 18) (proteins are identified by Institute for
Genomic Research [TIGR] locus numbers in Fig. 4). Both anti-
gens were detected in IVCL but not HTL. CRS was reactive with
the putative lipoprotein NT03LI2251 (spot numbers 14 and 15)
which was detected in IVCL but not HTL, suggesting that this is
a lipoprotein expressed at some stage during chronic infection of
rats but not at the time point examined during acute lethal infec-
tion of guinea pigs.
Loa22 was not identified by mass spectrometry, nor was any
protein spot with a similar molecular mass and pI to Loa22
identified on 2-D gels of TX-114-extracted IVCL. However, it
was identified with the added sensitivity provided by immuno-
blotting with Loa22-specific antiserum. Loa22 has previously
been identified by mass spectrometry in 2-D gels of outer
membrane vesicles, which corresponds in molecular mass and
pI to the Loa22 antigen detected in Fig. 2 (16).
It has long been appreciated that Leptospira species adapt to
and survive in vastly different environments, but little is known
about the molecular nature of these adaptations. The lepto-
spiral outer membrane lipoprotein LipL36 has provided one
example of environmentally regulated protein expression.
Immunohistochemical staining demonstrated expression of
LipL36 during in vitro growth at 30°C but not in infected tissue
or at culture temperatures of 37°C, indicating an adaptive
response by the organism to infection which included the dim-
inution of expression of LipL36 (7, 15).
We have recently reported that a human SPFL isolate causes
the severe pulmonary form of leptospirosis in guinea pigs and
chronic asymptomatic carriage in rats (13, 14). Since large
numbers of Leptospira organisms can be found in the livers of
infected guinea pigs, a procedure was developed for extracting
intact motile Leptospira organisms from infected host tissue.
The completed genomes of L. interrogans serovar Lai and
FIG. 3. Two-dimensional immunoblots, pH 4 to 7, of TX-114-extracted IVCL (2 ?g) or HTL (8 ?g) sample. Samples were probed with
monospecific antiserum specific for LipL32, LipL31, and Qlp42. Molecular mass markers (kDa) are provided on the left.
770 NALLY ET AL.INFECT. IMMUN.
serovar Copenhageni are predicted to have 3,728 and 4,727
protein-coding genes, respectively (17). In order to reduce the
complexity of proteins for sample analysis, both IVCL and
HTL samples were extracted with 2% TX-114 which also en-
riches for hydrophobic protein antigens, as previously de-
scribed (9, 15, 26). This has the added advantage of identifying
putative vaccinogen and diagnostic antigens associated with
the outer membrane of Leptospira during infection. Two-di-
mensional immunoblotting of TX-114-extracted IVCL indi-
cated that CRS reacts with several antigens of the outer mem-
brane of IVCL, which is confirmed by their reactivity with
monospecific antiserum for LipL32, LipL21, LipL41, and
Loa22. Mass spectrometry confirmed the identity of two addi-
tional CRS-reactive antigens as the putative lipoprotein
NT03LI2251. Several other antigens have yet to be identified.
By definition, all of these antigens are expressed during the
chronic infection process of rats and in sufficient amounts to
generate an antibody response. Similarly, CRS detected sev-
eral antigens in HTL samples derived from the liver tissue of
acutely infected guinea pigs. These antigens include several
also expressed in IVCL including the aforementioned LipL32,
LigA, LipL21, LipL41, and Loa22.
While absolute quantification of the amounts of each anti-
gen present in each sample is not provided, these findings do
provide an accurate view of the expression of antigens relative
to each other in HTL and IVCL preparations. For example,
Loa 22 is expressed in large amounts in HTL and is the only
antigen whose expression appears to be significantly up-regu-
lated during disease relative to detection of other antigens in
the same sample. In contrast to Loa22, the relative amounts of
LigA, LipL41, and LipL21 are reduced in HTL compared to
IVCL. There are also a number of unidentified antigens de-
tected with CRS or OMV serum, and their expression appears
reduced in HTL relative to their representation in IVCL. Sig-
nificant amounts of LipL32 are detected both during in vitro
growth and disease relative to the diminution of several other
known outer membrane antigens.
Expression of LipL32, LipL21, and Loa22 was detected with
antiserum specific for OMVs of IVCL and serum from chron-
ically infected rats. Some antigens were detected only with
FIG. 4. Two-dimensional immunoblots, pH 3 to 10, of TX-114-extracted IVCL (4 ?g) or HTL (16 ?g) sample. Samples were probed with CRS
or anti-OMV. The antigens identified by mass spectrometry or immunoblotting with monospecific antiserum are indicated. Molecular mass
markers (kDa) are provided on the left.
VOL. 75, 2007 THE IN VIVO PROTEOME OF LEPTOSPIRA771
anti-OMV, including the putative lipoprotein NT03LI0010 and
the conserved hypothetical protein NT03LIA0039, indicating
that they are expressed in IVCL but not in sufficient amounts
during chronic infection of rats to generate a detectable anti-
body response. LigA is reactive with CRS but only slightly
reactive with anti-OMV. Similar amounts of LigA are present
in each IVCL sample, suggesting that the greater reactivity
with CRS is due to the expression of LigA during chronic
infection of rats. As with CRS, anti-OMV generally reacts with
a smaller set of antigens in the HTL sample but does react with
LipL32, LipL21, and Loa22. Reactivity with the putative li-
poprotein NT03LI0010 and the conserved hypothetical protein
NT03LIA0039 is not detected in the HTL sample, confirming
their diminished expression in HTL, as already demonstrated
by a lack of reactivity with CRS.
While LipL32 is expressed in both IVCL and HTL, it was
noted that several lower-molecular-mass antigens are specifi-
cally reactive with LipL32 monospecific antiserum, indicating
that these fragments are likely derived from the mature
LipL32. It is of interest that different lower-molecular-mass
fragments of LipL32 are detected in IVCL and HTL sam-
ples. The meaning of this finding, observed with both CRS
and anti-OMV antiserum, is unclear at this time. However,
breakdown products of LipL32 have previously been noted
during experimental preparations of outer membranes of
IVCL (2, 26).
In this report, we have described the hydrophobic proteome
of guinea pig liver-derived HTL recovered during the course of
acute lethal infection. The relative amounts of Loa22 and
LipL32 were enhanced in HTL compared to IVCL samples.
There is also a striking reduction in the relative content of
other hydrophobic protein antigens in HTL relative to their
representation in IVCL. We have recently demonstrated that
the lipopolysaccharide O-antigen content of HTL found in
guinea pig liver is markedly reduced compared to that of
IVCL. Taken together, these findings indicate that the surface
antigen structure of HTL differs markedly from that of IVCL.
The role of these compositional changes in pathogenesis re-
mains to be determined.
These studies were supported by National Institutes of Health grant
AI056258 to M.A.L. and a Ruth L. Kirschenstein National Research
Service Award AI055235 to J.E.N. from the National Institutes of
Health, National Institute of Allergy and Infectious Diseases.
We thank David Haake for kindly providing antiserum specific for
LipL32, LipL41, Qlp42, OmpL1, LipL21, and LipL31. We thank
Nobuo Koizumi and Haruo Watanabe for kindly providing antiserum
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