Analyses of autoantigens in a new form of
endemic pemphigus foliaceus in Colombia
Ana Marı́a Abrèu-Velez, MD, PhD,a Ernst H. Beutner, PhD,b
Fernando Montoya, MD,c Wendy B. Bollag, PhD,a and Takashi Hashimoto, MDd
Augusta, Georgia; Buffalo, New York; Medellı́n, Colombia; and Fukuoka, Japan
Background: We previously described a new focus of endemic pemphigus foliaceus in rural areas of El Bagre,
Colombia, with clinical and direct immunofluorescence characteristics of pemphigus erythematosus.
Objective: The aim of this study was to characterize autoantigen profiles for 34 serum samples obtained from
patients with this condition.
Methods: Immunofluorescence, various immunoblot analyses with different antigen sources and detection
methods, and immunoprecipitation were performed.
Results: Immunofluorescence with the use of human skin sections showed IgG autoantibodies against
keratinocyte cell surfaces in all 34 serum samples. Some samples also showed weak reactivity with the
basement membrane zone. The results of immunoblot and immunoprecipitation analysis indicated that all
sera had antibodies reactive with desmoglein 1, the pemphigus foliaceus antigen. In addition, in various
immunoblot assays, many sera reacted with several other proteins with molecular weights of 250 kd, 210
kd, and 190 kd, which appear to correspond to desmoplakin I, envoplakin, and periplakin, respectively.
Conclusion: This endemic pemphigus disease in El Bagre showed immunologic features similar to
pemphigus foliaceus or erythematosus. In addition, paraneoplastic pemphigus–like reactivity with various
epidermal antigens was detected. (J Am Acad Dermatol 2003;49:609-14.)
E
ndemic pemphigus foliaceus (PF) represents
a unique group of autoimmune diseases that
occur in well-defined regions of South America1,2 and in Africa.3,4 Recently, we confirmed that
another endemic PF focus exists in a rural mining
municipality in El Bagre, in the northeastern part of
From the Institute for Molecular Medicine and Genetics, Medical
College of Georgiaa; Department of Microbiology, The State
University of New York, and Beutner Laboratories, Buffalo, New
York, USAb; Basic Biomedical Science Corporation, University of
Antioquia, Medellı́nc; and the Department of Dermatology,
Kurume University School of Medicine, Fukuoka.d
Funding sources: Grants from the Embassy of Japan in Colombia;
Mineros de Antioquia, S.A.; the Universidad de Antioquia; Medical College of Georgia; and the National Institutes of Health
(grant no. AR45212). Dr Abrèu-Velez received a scholarship from
Colciencias, Colombia. Studies at Beutner Laboratories on monkey esophagus sections were aided by Beutner Laboratories with
National Institutes of Health grant no. RR00163 to the Oregon
Primate Center.
Conflict of interest: None identified.
Accepted for publication September 29, 2002.
Reprint requests: Ana Marı́a Abrèu-Velez, Institute of Molecular
Medicine and Genetics, Medical College of Georgia, 1120
Fifteenth St, CB 2803, Augusta, GA 30912. E-mail: aavelez@
mail.mcg.edu.
Copyright © 2003 by the American Academy of Dermatology, Inc.
0190-9622/2003/$30.00 ⫹ 0
doi:10.1067/S0190-9622(03)00852-1
Abbreviations used:
Dsg: desmoglein
IF:
immunofluorescence
PF:
pemphigus foliaceus
the state of Antioquia in Colombia, South America.5-7
Ten years of fieldwork in El Bagre confirmed the
endemic nature of this disease.8 The clinical manifestations of El Bagre endemic PF resembled most
closely those of pemphigus erythematosus, also
known as Senear-Usher syndrome. El Bagre endemic PF predominantly affects 40- to 60-year-old
men, as well as a few postmenopausal women, and
the patients are primarily miners who also engage in
farming.5-7 This finding is quite different from that of
Brazilian endemic PF, or fogo selvagem, which primarily affects children and young adults, with the
highest incidence at 10-30 years of age and both
sexes equally affected.1,2 Also in contrast to the El
Bagre form, endemic PF reported in Tunisia most
frequently affects women of childbearing age. Moreover, the endemic nature of Tunisian endemic PF
has not been clearly documented.3,4
In this study, to further characterize the immunopathologic features of El Bagre endemic PF, we
609
610 Abrèu-Velez et al
J AM ACAD DERMATOL
OCTOBER 2003
demonstrated the presence of autoantibodies to various autoantigens in patients with this disease by
means of various immunologic and biochemical
methods, including immunofluorescence (IF), immunoblot, and immunoprecipitation.
MATERIALS AND METHODS
Sera and antibodies
For this study, we used sera from 34 patients with
El Bagre endemic PF in a clinically active stage.
These sera were randomly selected from the stock
collected during our 10-year survey in the endemic
areas of El Bagre. The criteria for diagnosis of this
disease have been previously described.5-7 All patients participated willingly in this study and gave
informed consent.
As controls, serum samples were collected from
34 healthy persons living in nonendemic areas in
Medellı́n, Colombia, and having a similar but not
identical ethnic background to the endemic PF patients. These nonendemic controls were about 50%
American Indian and white (mestizo), 40% white,
6% American Indian and black (zambo), 4% white
and black (mulatto), and a few American Indians,
most of whom were only temporarily visiting the
city.9 We also tested 34 matched controls from the
endemic area of El Bagre, identical in age, sex, and
ethnic background to the PF patients from the endemic area. The El Bagre population includes about
41% mestizos, 15% whites, 14% zambos, 3% mulattoes, and 1% American Indians.10 The proportions of
the individuals studied reflect the ethnic backgrounds in the respective regions. Finally, sera from
34 patients with nonendemic (sporadic) PF, 3 typical
bullous pemphigoid patients, and 3 typical paraneoplastic pemphigus patients from Medellı́n city were
used as additional controls.
IF analysis
Indirect IF with sections of normal human skin
was performed by means of standard methods.11 To
determine IgG subclasses, fluorescence-conjugated
mouse monoclonal antibodies specific to human
IgG1-4 (Sigma, St Louis, Mo) were used.
Immunoblot analysis
We performed various immunoblot methods using different antigen sources and different detection
procedures to identify possible autoantigens recognized by the El Bagre endemic PF sera. Normal
human epidermis (full thickness) was split with a
dermatome, powdered using liquid nitrogen, and
prepared as described previously.12 The extracts of
1mol/L NaCl-split human epidermis were also prepared as previously described.13 For the third antigen source, we prepared extracts of cultured
Fig 1. The results of indirect IF using human skin sections
and a representative El Bagre endemic PF serum. a, IgG
reactivity with keratinocyte cell surfaces (small arrow) and
weak reactivity with the basement membrane zone (large
arrow). b, IgG4 reactivity with cell surfaces (arrows) is
illustrated.
MCF-12 cells, a human mammary epithelial cell line
(American Type Culture Collection).
Detection with the use of alkaline phosphatase–
conjugated secondary antibodies was performed
with standard methods. Detection using iodine 125–
labeled protein A was performed as reported previously.14-18 We also utilized a chemiluminescence detection procedure (SuperSignal; Pierce, Milwaukee,
Wis). Mouse monoclonal antibodies to desmoglein 1
(Dsg1) and desmoplakin were obtained from Progen Biotech (Heidelberg, Germany).
Immunoprecipitation analysis
Protein samples were released from bovine snout
epidermis by means of trypsin digestion and purified with the use of a concanavalin A column. These
proteins were radiolabeled with iodine 125 by
means of the chloramine-T method, as described
previously.14,18 Immunoprecipitation was performed
as described previously.14-18
RESULTS
IF studies
Indirect IF with the use of human skin sections
showed IgG antikeratinocyte cell surface antibodies
in all 34 El Bagre endemic PF serum samples (Fig 1,
a). Furthermore, 7 (20%) of the sera showed IgG
anti– basement membrane zone antibodies, although the reactivity was weak. Indirect IF with
monoclonal antibodies to human IgG subclasses
showed that all 34 endemic PF sera contained IgG4
antibodies to the keratinocyte cell surface (Fig 1, b).
In addition, 9 (26%) sera showed IgG1 anti– cell
surface antibodies, but no sera showed either IgG2
or IgG3 antibodies. Some sera also showed IgG4
antibodies to the basement membrane zone, although the reactivity was again weak (data not
shown).
All 34 sporadic nonendemic PF sera also showed
IgG anti– cell surface antibodies and contained specifically IgG4-type antibodies, while no sera showed
Abrèu-Velez et al 611
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VOLUME 49, NUMBER 4
reactivity with the basement membrane zone. Interestingly, 3 (9%) sera of the 34 healthy persons in
endemic areas showed IgG anti– cell surface antibodies (data not shown), while none of the 34 sera
from the healthy persons in nonendemic areas had
this reactivity.
antibody and sporadic PF sera. The 250-kd protein
comigrated with the protein detected by an antidesmoplakin monoclonal antibody. In addition, the
210-kd and 190-kd proteins comigrated with envoplakin and periplakin, which were identified with
the use of paraneoplastic pemphigus sera.
Immunoblot studies
With the use of extracts of full-thickness epidermis as an antigen source and alkaline phosphatase–
labeled secondary antibody for detection, immunoblot analysis showed that 11 (33%) of the 34 El Bagre
endemic PF sera recognized a 160-kd protein band
(Fig 2, a). This band comigrated with Dsg1, which
also was detected in approximately one third of the
34 sporadic PF sera. However, other protein bands
with molecular weights of approximately 250 kd,
210 kd, and 190 kd were also detected in 12 (35%)
endemic PF sera. An antidesmoplakin monoclonal
antibody reacted with the 250-kd desmoplakin I,
which comigrated with the 250-kd antigen recognized by endemic PF sera. This monoclonal antibody did not show clear reactivity with the 210-kd
desmoplakin II, probably because the amount of
desmoplakin II was too little to be detected. All three
paraneoplastic pemphigus sera also showed reactivity with 210-kd and 190-kd proteins (data not
shown). Surprisingly, 8 (23%) of the 34 sera from
healthy persons in the endemic area also showed
reactivity with the 160-kd protein (data not shown).
Similar reactivity was observed when chemoluminescence was used as a detection procedure in place
of the alkaline phosphatase–labeled secondary antibody (data not shown). In addition, we performed
immunoblot analysis using iodine 125–labeled secondary antibodies for detection. With this method,
11 (33%) endemic PF sera showed the 160-kda protein in the extracts of 1mol/L NaCl-split epidermis
(Fig 2, b). In addition, 13 (38%) of the 34 endemic PF
sera exhibited reactivity with several other protein
bands, particularly those with molecular weights of
approximately 250 kd and 210 kd. The 250-kd protein comigrated with the protein shown by antidesmoplakin monoclonal antibody. The 160-kd Dsg1
was also shown by 11 (33%) sporadic PF sera.
With immunoblot analysis, we further characterized the recognized antigens using MCF-12 cell extracts as an antigen source and alkaline phosphatase–labeled secondary antibody to visualize
reactivity, since this method showed various protein
bands most clearly. With this method, 15 (44%) endemic PF sera reacted with proteins of molecular
weights of about 300 kd, 250 kd, 210 kd, 190 kd, and
160 kd (Fig 2, c). The 160-kd protein comigrated
with Dsg1 detected by an anti-Dsg1 monoclonal
Immunoprecipitation studies
Immunoprecipitation analysis with trypsin-released radiolabeled proteins from bovine snout epidermis showed that 32 (94%) of 34 endemic PF sera
clearly immunoprecipitated a 45-kd protein band
(Fig 3). In previous studies, this 45-kd protein was
shown to be an extracellular fragment of Dsg1 by
excision of the band and amino acid sequence analysis. The sequence thus obtained, EXIKFAAAXREGED, matched the N-terminal domain of the mature
form of bovine Dsg1.16,17,19 The 45-kd band was
recognized by all PF sera and in all patients affected
with El Bagre endemic PF. Three sera obtained from
patients with mild conditions showed relatively
weak reactivity with the 45-kd protein (data not
shown). Interestingly, some endemic PF sera were
able to immunoprecipitate several other protein
bands of approximately 80 kd and 34 kd (Fig 3).
These protein bands may be related to the other
antigens detected by means of immunoblot, such as
the plakin family proteins; however, the proteins
were detected in association with strong reactivity to
the 45-kd Dsg1 fragment. It is also plausible that
these proteins are related to Dsg1 or are degradation
products of Dsg1. Three (9%) of the sera from
healthy individuals in the endemic area also precipitated the 45-kd protein, as well as other proteins of
about 80 kd and 34 kd (Fig 3). None of the healthy
persons in nonendemic areas showed positive reactivity (data not shown).
DISCUSSION
In this study, we found with indirect IF that all
endemic PF sera possessed circulating IgG autoantibodies reactive with the keratinocyte cell surfaces,
the gold standard for the diagnosis of pemphigus.9
Thus this result confirms the autoimmune nature of
this new endemic PF in El Bagre, Colombia. The IgG
subclass study revealed the predominant subclass to
be IgG4, as has been shown previously for other
forms of endemic PF.20
In addition, some endemic PF sera showed circulating IgG (particularly, IgG4) anti– basement membrane zone antibodies, although the significance of
this finding and the antigens recognized by these
autoantibodies are not clear. The presence of anti–
basement membrane zone autoantibodies has also
been reported in a few cases of Brazilian endemic
PF, although this reactivity was not carefully stud-
612 Abrèu-Velez et al
J AM ACAD DERMATOL
OCTOBER 2003
Fig 3. Results of immunoprecipitation analysis using a
trypsin-released radiolabeled protein sample from bovine
snout epidermis. Endemic PF sera recognized a 45-kd
protein, representing a fragment of Dsg1 (EPF, lanes 2-6).
In addition, these sera also reacted with several other
molecules in the region of 80 kd and 34 kd. Serum from a
sibling of an endemic PF patient also showed similar
reactivity (SIB, lane 7). In contrast, a sporadic PF serum
reacted with the 45-kd Dsg1 fragment but not with other
proteins (lane 1). A representative normal serum from the
nonendemic area did not show any specific reactivity
(lane 8). The position of the 45-kd fragment is shown to
the left.
Fig 2. Results of immunoblot studies using different antigen sources and detection methods. a, The results of
immunoblot analysis with extracts of keratome-separated
epidermis, alkaline phosphatase– conjugated secondary
antibody, and PF serum (lane 2) are illustrated. Four representative El Bagre endemic PF sera (EPF, lanes 4-7) also
reacted with a 160-kd protein. In addition, the endemic PF
sera reacted with several other proteins, particularly 250kd, 210-kd, and 190-kd proteins. An antidesmoplakin
monoclonal antibody reacted with 250-kd desmoplakin I
(DPL, lane 1), which comigrated with the 250-kd antigen
recognized by endemic PF sera. A bullous pemphigoid
serum reacted with the 180-kd bullous pemphigoid antigen (BP, lane 3); whereas normal serum did not show any
specific reactivity (lane 8). b, The results of immunoblot
analysis with extracts of 1M NaCl-split epidermis and iodine 125– conjugated secondary antibody show that the
antidesmoplakin monoclonal antibody reacted with the
250-kd desmoplakin I (DPL, lane 1). An anti-Dsg1 monoclonal antibody (lane 2) and a PF serum (lane 3) reacted
with 160-kd Dsg1. Three of the 4 representative El Bagre
endemic PF sera (EPF, lanes 4-7) also reacted with a
160-kd protein. In addition, all endemic PF sera reacted
with the 250-kd and 210-kd proteins. Reactivity with a
190-kd protein was not observed. Normal serum showed
no specific reactivity (lane 8). The broad band seen in the
lower portion of each lane is nonspecific reactivity with
the large quantities of keratins in these extracts. c, Immunoblot analysis with extracts of MCF-12 cells and alkaline
phosphatase– conjugated secondary antibody shows that
an antidesmoplakin monoclonal antibody reacted with
250-kd desmoplakin I (DPL, lane 1). An anti-Dsg1 monoclonal antibody (lane 2) and PF serum (lane 3) reacted
with 160-kd Dsg1. A paraneoplastic pemphigus serum
showed reactivity with 210-kd envoplakin and 190-kd
periplakin, as well as many lower molecular weight protein bands (PNP, lane 4). All 4 endemic PF sera reacted
with the 160-kd, the 210-kd, and the 190-kd proteins (EPF,
lanes 5-8). Two of 4 endemic PF sera reacted with the
250-kd protein (lane 6). The molecular weight of each
recognized protein is indicated to the left.
J AM ACAD DERMATOL
VOLUME 49, NUMBER 4
ied.21 In vivo deposition to the basement membrane
zone was found in 8 (17%) of 47 Brazilian endemic
PF skin biopsy specimens, but the authors described
this finding as nonspecific reactivity.22
Nearly all of the El Bagre endemic PF sera reacted
specifically with Dsg1, the PF antigen,18 in both
human and bovine protein samples using immunoblot and immunoprecipitation methods, as well as a
newly developed enzyme-linked immunosorbent
assay.18 This result further indicates the similarity of
this disease to Brazilian endemic PF, in which about
one-third of fogo selvagem sera have autoantibodies
against linear epitopes of Dsg1 and almost all cases
recognize a conformational epitope of the 45-kd
Dsg1 antigen by means of immunoprecipitation.15,16,18 Because Tunisian endemic PF patients
showed variable reactivity with either Dsg1 or
Dsg3,4 this type of endemic PF does not seem to be
closely related to endemic PF in Colombia and
Brazil.
However, the most interesting and puzzling finding was the complex immunoreactivity exhibited by
the El Bagre endemic PF sera as shown with immunoblot studies. These experiments showed that a
considerable number of El Bagre endemic PF sera
reacted with multiple protein bands, particularly
250-kd, 210-kd, and 190-kd proteins. Studies using
specific monoclonal antibodies and paraneoplastic
pemphigus serum indicated that the 250-kd protein
was likely desmoplakin I and the 210-kd and 190-kd
doublet proteins were envoplakin and periplakin,
respectively. This potential reactivity with various
plakin family proteins may indicate a possible relationship between El Bagre endemic PF and paraneoplastic pemphigus.23-25 This possibility would then
suggest the idea that paraneoplastic pemphigus
could be the result of viral activation of the hematologic malignancy and not a paraneoplastic phenomenon per se. However, to date no reports indicate that viral activation occurs and plays a role in
the production of these autoantibodies in paraneoplastic pemphigus. Therefore, presently we have no
evidence that the production of antidesmoplakin
antibodies in paraneoplastic pemphigus or in endemic PF is related to viral infection in affected
patients.23-25
The heterogeneous reactivity with multiple antigens shown by the sera of El Bagre endemic PF
patients has not been clearly described in Brazilian
endemic PF.26,27 Therefore, the results of this study
suggest that there is a difference between Brazilian
endemic PF and El Bagre endemic PF, although the
two diseases occur inside South America and have
many identical features. Interestingly, some sera
from healthy individuals living in the endemic area
Abrèu-Velez et al 613
around El Bagre showed IgG anti– cell surface antibodies by indirect IF and reacted with Dsg1 and
other El Bagre endemic PF–related molecules with
both immunoblot and immunoprecipitation analyses. This reactivity was not seen in healthy persons
living in nonendemic areas. These results are consistent with the finding that some sera from healthy
persons living in Brazilian endemic PF areas frequently have anti-Dsg1 autoantibodies.27 Therefore,
it is conceivable that environmental factors present
in the endemic areas are responsible for the development of endemic PF both in Brazil and in El
Bagre, Colombia.
An additional puzzling result was the observation
that a considerable number of serum samples from
patients with endemic PF and those with sporadic
PF reacted with a Dsg1-like 160-kd protein in extracts of MCF-12 cells, which were originally derived
from mammary cells. This protein may not be Dsg1
but another molecule with the same molecular
weight or a similar conformational epitope. However, because the protein specifically reacted with
endemic PF and nonendemic PF sera, and because
epidermal-specific Dsg may be expressed in some
cultured nonepidermal cells, such as MDCK cells,28
we considered the possibility that Dsg1 may be
expressed in MCF-12 cells in cell culture. Indeed, a
monoclonal antibody to Dsg1 also recognized this
160-kd protein in extracts of MCF-12 cells, suggesting that this protein is Dsg1 or a closely related
protein.
Although the present study is still somewhat preliminary, this research clarifies the immunologic nature of endemic PF in El Bagre and further suggests
some unique, yet unknown, pathogenic mechanism
specific for this disease. Further studies using modern molecular biologic techniques are in progress to
better characterize the autoimmune mechanism mediating this interesting disease.
We extend our thanks to the people of El Bagre and to
all public and private companies in Colombia that supported our program. We also acknowledge our co-workers who participated in the visits to El Bagre for their
contribution to this research and humanitarian program.
We gratefully appreciate Francois Tron, MD, Joly Pascal,
MD, Fabianne Jouen-Beades, MD, Danielle Gilbert, PhD,
and Vincent Saulot, PhD, Institut National de la Santé et de
la Recherche Médicale (INSERM), France, for their kind
encouragement and for generously providing us with the
MCF-12 cells. In addition, we thank Rhea-Beth Markowitz,
PhD, of the Medical College of Georgia for her excellent
editorial assistance. This article represents a portion of the
PhD thesis of Ana Marı́a Abrèu-Velez, who received a
scholarship from Colciencias, Colombia, administered by
the Latin American Scholarship Program of American Universities (USA).
614 Abrèu-Velez et al
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