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Journal of Clinical Microbiology, May 2004, p. 2294-2297, Vol. 42, No. 5
0095-1137/04/$08.00+0 DOI: 10.1128/JCM.42.5.2294-2297.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Culture-Independent Species Typing of Neotropical Leishmania for Clinical Validation of a PCR-Based Assay Targeting Heat Shock Protein 70 Genes
Lineth Garcia,1,2 Ann Kindt,1 Hernan Bermudez,2 Alejandro Llanos-Cuentas,3 Simonne De Doncker,1 Jorge Arevalo,3 Kelly Wilber Quispe Tintaya,1,3 and Jean-Claude Dujardin1*
"Prince Leopold" Institute of Tropical Medicine, Molecular Parasitology, Antwerp, Belgium,1
Centro Universitario de Medicina Tropical, Cochabamba, Bolivia,2
Instituto de Medicina Tropical "Alexander von Humboldt," Lima, Peru3
Received 3 October 2003/
Returned for modification 1 December 2003/
Accepted 31 January 2004

ABSTRACT
PCR-restriction fragment length polymorphism analysis of heat
shock protein 70 genes discriminates most neotropical
Leishmania species, as well as
Trypanosoma cruzi. The assay, combined with
capillary electrophoresis in a microchip device, may be applied
directly on clinical samples with a high sensitivity, hence
supporting clinical and epidemiological monitoring of leishmaniasis.

TEXT
Leishmaniasis is endemic in 88 countries, causing a burden estimated
at 2,357,000 disability adjusted life years and 59,000 deaths
(
12). The disease is characterized by a considerable clinical
and epidemiological pleomorphism, which is linkedbesides
host factorswith the important diversity of
Leishmania species and their vectors. Clinical and epidemiological monitoring
requires rapid and high throughput tools for species typing.
This can be achieved with PCR assays combining a high detection
level with the adequate discriminatory power. Currently, a few
genetic targets are available: ribosomal DNA internal transcribed
spacers (ITS) (
5),
gp63 genes (
10), miniexon genes (
7), and
kinetoplast DNA (
3). However, there are still very few studies
on their direct application to human tissues as well as their
clinical and epidemiological validation in the New World, where
several species can be sympatric (
6,
11). We report here a complementary
assay based on PCR amplification of the repeated heat shock
protein 70 genes (
1,
8), followed by restriction fragment length
polymorphism analysis (
hsp70 PCR-RFLP).
Development of hsp70 PCR assay.
Reported sequences of Leishmania (Viannia) braziliensis and Leishmania (Leishmania) mexicana hsp70 genes (accession no. AF291716 and M87878) were aligned with the CLUSTAL W 1.8 program. The primers were designed from the conserved region between Leishmania species with PRIMER PREMIER software: Hsp70sen (5' GACGGTGCCTGCCTACTTCAA 3') and Hsp70ant (5' CCGCCCATGCTCTGGTACATC 3'). hsp70 PCR amplification was carried out in a 50-µl solution containing 1x Taq polymerase buffer (Eurogentec, Seraing, Belgium), 1.5 mM MgCl2, a 200 µM concentration of each deoxynucleoside triphosphate, 5% dimethyl sulfoxide, 20 pmol of primers, and 2.5 U of Taq DNA polymerase (Eurogentec). The reaction mixtures were amplified in a MJ Research PTC-100 cycler with a heated lid at 94°C for 5 min followed by 33 cycles, each consisting of 30 s at 94°C, 1 min at 61°C, and 3 min at 72°C, and a final extension step of 10 min at 72°C.
hsp70 PCR on laboratory samples.
We analyzed 59 reference strains (Table 1) of species reported in Latin America: L. (V.) braziliensis, Leishmania (Viannia) peruviana, Leishmania (Viannia) lainsoni, Leishmania (Viannia) guyanensis, Leishmania (Viannia) panamensis, Leishmania (Leishmania) amazonensis, and Leishmania (Leishmania) infantum [synonym Leishmania (Leishmania) chagasi]. Promastigotes were cultivated and harvested (10) and were DNA purified with DNAzol (Gibco, Merelbeke, Belgium). After hsp70 PCR, a single 1,300-bp product was observed in all Leishmania strains, corresponding to the expected size. The same product was encountered in Trypanosoma cruzi, but no amplification was detected with DNA from humans Mycobacterium tuberculosis, or Sporothrix schenckii.
hsp70 PCR-RLFP on laboratory samples.
hsp70 PCR products were ethanol precipitated and resuspended
in 20 µl of water. Digestion with restriction enzymes
was performed according to the suppliers' recommendations in
a final volume of 10 µl. Electrophoretic resolution was
first performed in 3% agarose, by using 9 µl of digestion
products, and then in microchips (2100 Bioanalyzer capillary
electrophoresis system; Agilent Technologies, Karlsruhe, Germany)
(LabChip 1500 or 7500; Caliper Technologies, Mountain View,
Calif.) with only 1 µl of digests because of their high
sensitivity and discriminatory power. From the five restriction
enzymes tested, AsuI, TaqI, AluI, and AvaI distinguished
L. (
L.)
amazonensis from all
Leishmania samples of subgenus
Viannia,
while HaeIII (BsuRI) distinguished all species but
L. (
V.)
peruviana (Fig.
1A), a species found only in the Peruvian highlands (
11).
However,
hsp70 sequencing data revealed a BsiI restriction site
differentiating that species from
L. (
V.)
braziliensis. There
was no intraspecies polymorphism as with assays targeting rDNA
ITS or
gp63 (
5,
10).
T. cruzi, in which a 1,300-bp
hsp70 amplicon
was also encountered, showed a different cleavage pattern (Fig.
1A). This might be particularly useful for identifying mixed
infections of
Leishmania spp. and
T. cruzi, which can be quite
frequent in Latin America (
4). Analytical sensitivity of the
PCR-RFLP assay was higher with capillary (3 parasites/µl
before PCR) than with agarose electrophoresis (30 parasites/µl).
Clinical samples.
Thirty-four biopsy samples (4 mm) from Bolivian patients with
clinical suspicion of tegumentary leishmaniasis (cutaneous and
mucosal) were obtained with informed consent from the Isiboro
secure area, between 1994 and 2000. Frozen biopsy specimens
were lysed at 65°C for 3 h in 50 µl of TNE buffer
(25 mM Tris, 100 mM NaCL, 5 mM EDTA [pH 8]) containing 5% sodium
dodecyl sulfate and 200 µg of proteinase K/µl. After
ethanol precipitation, DNA pellets were resuspended in 15 µl
of buffer TE (10 mM Tris, 1 mM EDTA [pH 7.4]), and 2 µl
was used for
hsp70 PCR.
First, the capacity to detect parasites was considered. Sensitivity was compared with other methods, by using a laboratory case definition (positivity with microscopy, culture, or hsp70 PCR itself) and scored as follows (Table 2): 100% (hsp70 PCR), 92.9% (axenic culture), 80.9% (intradermal reaction of Montenegro [IDRM]), and 28.6% (microscopy). hsp70 PCR is thus slightly more sensitive than similar assays designed for species identification (85 to 89.7%; 6, 11). The relatively high sensitivity observed here for axenic culture can be explained by the fact that in CUMETROP, several aspirates are taken from the same patient to increase the isolation rate. The specificity of hsp70 PCR was 100%, but routinely, any positive sample should be digested to confirm a Leishmania pattern (versus T. cruzi, for instance). Concordance was highest between PCR and culture (kappa = 0.82).
View this table:
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TABLE 2. Diagnostic performance of 34 hsp70 PCRs on samples from Bolivian patients with clinical suspicion of tegumentary leishmaniasis compared to microscopy, culture, and IDRMa
|
Second, species identification was performed by cutting the
hsp70 amplicons of the 28 PCR-positive samples with HaeIII;
26 and 28 patterns were detected in agarose gels and microchips,
respectively. Species identification was
L. (
V.)
braziliensis (27 samples, including the two that were only PCR positive)
and
L. (
V.)
lainsoni (1 sample) (Fig.
1B).
Conclusion.
Our study brings new and original aspects to the field of Leishmania genetic characterization. Microchip capillary electrophoresis increases the performance of PCR-RFLP assays. hsp70 genes represent an adequate target for sensitive typing of neotropical Leishmania species in host tissues. They bring complementary information to other markers: (i) encoding for a major antigen (9), they allow probing of the genetic variability of molecules possibly involved in immunopathology, and (ii) presenting a lower rate of genetic variation than gp63 genes or rDNA ITS, for instance, they may be applied at other taxonomical levels (combining species and genus typing). This new marker also paves the way to future multigenic PCR-based approaches, essential for direct population studies in the host. Further work should be undertaken to compare on the same clinical samples the sensitivity, specificity, and discrimination power of the different PCR-RFLP assays currently available and to confirm the performance of hsp70 PCR-RFLP in other trypanosomatids.

ACKNOWLEDGMENTS
This study received financial support from TDR (grant 00476),
EC (grant IC18-CT96-0123), Belgian technical cooperation (02-0001-BOL/00/003),
the Belgian Agency for Cooperation and Development (DGCD), and
FWO (Flemish fund for Scientific research 1.5.047.02).
We thank C. Barnabé, Institut de recherche pour le Développement, Montpellier, France, for the gift of T. cruzi CANIII DNA.

FOOTNOTES
* Corresponding author. Mailing address: Prins Leopold Instituut voor Tropische Geneeskunde, 155 Nationalestraat, B-2000 Antwerpen, Belgium. Phone: 32.3.2476358. Fax: 32.3.2476359. E-mail:
jcdujard{at}itg.be.


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Journal of Clinical Microbiology, May 2004, p. 2294-2297, Vol. 42, No. 5
0095-1137/04/$08.00+0 DOI: 10.1128/JCM.42.5.2294-2297.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
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