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Journal of Clinical Microbiology, August 2008, p. 2783-2785, Vol. 46, No. 8
0095-1137/08/$08.00+0 doi:10.1128/JCM.02370-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Lewis Antigen Expression by Helicobacter pylori Strains Colonizing Different Regions of the Stomach of Individual Patients
Gerardo González-Valencia,1,
Leopoldo Muñoz-Perez,1,
Rosario Morales-Espinosa,2
Margarita Camorlinga-Ponce,1
Onofre Muñoz,3 and
Javier Torres1*
Unidad de Investigación en Enfermedades Infecciosas, Hospital de Pediatría, IMSS, México,1
Departamento de Microbiología y Parasitología, Facultad de Medicina, UNAM, México,2
Hospital Infantil de México, Federico Gómez SS, México3
Received 10 December 2007/
Returned for modification 4 April 2008/
Accepted 29 May 2008

ABSTRACT
The diversity in the expression of Lewis antigens (Le) of 226
single colonies of
Helicobacter pylori isolated from four regions
of the stomach of eight adults is shown. Le
y was expressed more
in strains colonizing antrum than in strains colonizing fundus,
whereas Le
x was more common in fundus strains.
cagA+ strains
were more associated with Le-negative strains.

TEXT
The
Helicobacter pylori Lewis antigens (Le) mimic Lewis blood
group antigens found on the surfaces of human gastric cells,
providing the bacteria with a possible mechanism of immune evasion
(
5). This intimate interaction with the epithelia suggests that
adaptation to specific regions of the stomach might occur. Most
reports have studied
H. pylori Le expression in isolates from
the antrum and corpus exclusively (
6-
8,
10); the present study
sought to characterize Le antigen expression in multiple colonies
isolated from four regions of the stomach, namely, the antrum,
corpus, fundus, and incisura of individual patients. The possible
correlation of Le antigen expression with the presence of
cagA is still contradictory (
8,
10). We also analyzed the possible
association of Le antigens expression with
cagA.
Eight Mexican patients with an average age of 58 years (range, 28 to 71 years; five male, three female) presenting at the Gastroenterology Unit of Hospital de Especialidades, CMNSXXI, Instituto Mexicano del Seguro Social, in Mexico City because of gastroduodenal symptoms were studied. Participants were informed about the nature of the study and asked to sign a consent form; the present study was approved by the Instituto Mexicano del Seguro Social Ethics Committee. Two biopsy samples from each site—the antrum, incisura, corpus, and fundus—were obtained; one biopsy of each site was homogenized and cultured for H. pylori on selective blood agar medium in a 10% CO2 atmosphere, as previously described (6). A total of 226 individual colonies were studied (Table 1), a mean of 28 colonies per patient, and seven patients per region. From each colony, a 48-h culture in blood-agar was harvested in saline solution for DNA isolation and for Le antigen determination. The presence of Le antigens was determined by an enzyme-linked immunosorbent assay using commercial monoclonal antibodies to Lex and Ley (Signet Laboratories, Dedham, MA), as previously described (5). Results were expressed in optical density units (ODU), and values of >100 ODU were considered positive. Each clone was tested in quadruplicate on 2 different days, and the mean of the ODU was used for analysis. Differences in frequencies among regions were analyzed by using the chi-square test. DNA was isolated by using guanidine-isothiocyanate-sarkosyl and then used to determine cagA by PCR (6) and to genotype isolates by RAPD [random(ly) amplified polymorphic DNA] as previously described (1).
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TABLE 1. Frequency of Le antigen expressed by 226 isolates from four different regions of the stomachs of eight Mexican patients
|
In contrast to previous studies (
6-
8,
10), we mapped the expression
of Le antigens by strains colonizing four regions of the stomach.
The frequencies of expression of Le antigens among all of the
226 isolates were 38% for Le
–, 28% for Le
y, 27% for Le
xy,
and 7% for Le
x (Table
1). It is important to note that the frequency
of colonies expressing Le
x+y– was significantly lower
(
P = 0.02) in the antrum than in the fundus. In addition, there
was a trend for colonies Le
x–y– to be less common
in the antrum than in the incisura and fundus, although this
trend was not significant. Taken together, the frequency of
colonies expressing Le
y was significantly higher in antrum (38
of 57) than in both incisura and fundus (27 of 56 in both) (
P = 0.048) (Table
1). In addition, there was a trend for colonies
expressing Le
x+y+ to be more frequent in the antrum than in
the fundus, although this trend was not significant (
P = 0.15).
As in a previous study in Mexican patients (6), a considerable variability in the levels of expression of Le antigens (mean ± the standard deviation) was found in all colonies from the four regions of the stomach (Fig. 1 and Table 2), even among isolates from the same patient. For example, the isolates from patient 256 were highly variable for Ley, and the isolates from patient 251 were highly variable for Lex in the four stomach regions studied. Even so, in the antrum the level of expression of Ley (972 ± 621) was significantly higher than the expression of Lex (599 ± 578), whereas in the other three regions no significant difference was found between the expressions of Ley and Lex. The variability observed in the expression of Le antigen was not due to colonization with different strains, since in seven of the eight patients all of the isolated colonies showed the same RAPD pattern, and only in one case (patient 259) was a mixed infection documented, showing two different RAPD patterns. In accordance with these results, a previous study also reported a high diversity in the expression of Le antigens among multiple isolates from single patients even if they had the same RAPD pattern; the authors of that study suggested that variability in expression of Le antigens is not due to genetic diversity but to mechanisms regulating the expression and activity of fucosyltransferases (11). This variability would justify considering each colony as a phenotypically independent event for the statistical analyses.
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TABLE 2. Comparison of levels of expression of Lewis antigens in four different regions of the stomach by single-colony isolates from eight Mexican patients
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The results presented above suggest that there is selective
expression of Le antigens by
H. pylori in the different regions
of the stomach. The expression of Le
y seems to be predominant,
or selected for in the antrum, whereas that of Le
x–y– and Le
x would be favored in the environment of the fundus. A
limitation of the present study is the number of patients analyzed,
and a study with larger number of cases is needed to confirm
these results. It has been suggested that the expression of
surface antigens involved in interaction and binding to epithelial
cells, such as Le antigens by
H. pylori, is influenced by the
environment present in the different regions of the gastroduodenal
regions (
9). Thus, a previous study found significant differences
between strains colonizing the antrum and those colonizing the
duodenum (
9).
The expression of Le antigens has been associated with the presence of the cagA+ gene. Lex expression has been reported as associated to cagA+ (10); however, and similar to other studies (4, 6, 8), we did not find such an association. In fact, even considering that Lex was the less expressed of the Le antigens (16 of 226 isolates, Fig. 1), only 4 (25%) of the 16 Lex colonies were cagA+. These four colonies were isolated from three different patients. We found a significant decreasing tendency of association with cagA and Le antigens as follows: Lex < Ley (P = 0.02) < Lexy (P = 0.005) < Le– (P < 0.001). Thus, in contrast to previous studies, cagA was significantly more associated with strains not expressing Le antigens.
In contrast to what we found for Le expression, the presence of cagA+ strains was not significantly different among the four regions of the stomach studied, which is consistent with previous results of an in situ study of cagA+ strains (2).

ACKNOWLEDGMENTS
This project was supported by CONACYT and Coordinacíon
de Investigacíon, IMSS, Mexico. J.T. is a recipient of
an exclusivity scholarship from Fundacíon IMSS, Mexico.

FOOTNOTES
* Corresponding author. Mailing address: Av. Centenario 1707-39, México DF, C.P. 01580, México. Phone: 1152-55-5-627-6940. Fax: 1152-55-5-627-6949. E-mail:
jtorresl57{at}yahoo.com.mx 
Published ahead of print on 11 June 2008. 
G.G.-V. and L.M.-P. contributed equally to this study. 

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Journal of Clinical Microbiology, August 2008, p. 2783-2785, Vol. 46, No. 8
0095-1137/08/$08.00+0 doi:10.1128/JCM.02370-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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