Protective immunogenicity of the paraflagellar rod protein 2 of Leishmania mexicana.

Paraflagellar rod proteins (PFR) are a potent immunogen against experimental Trypanosoma cruzi infection. PFR are highly conserved among kinetoplastid parasites. We therefore evaluated the immunogenicity of the Leishmania mexicana pfr-2 gene and protein product in the hamster model of American cutaneous leishmaniasis. Immunization with pfr-2 DNA-induced specific antibody, confirming immunogenicity. Subsequent challenge with 10,000 and 500 stationary phase L. mexicana promastigotes respectively, resulted in delayed appearance of lesions, and significant reduction in lesions post infection in male hamsters, yet exacerbated lesions in female hamsters. Immunization with recombinant PFR-2 protein (rPFR-2) prevented lesion development in female hamsters challenged with L. panamensis, but was ineffective against L. mexicana. Nevertheless, prime boost immunization of female hamsters with rPFR and pfr-2 DNA significantly reduced lesion size following challenge with 500 L. mexicana promastigotes, supporting the relevance of PFR-2 as a potential vaccine constituent.

Evaluation of nested polymerase chain reaction, pepsin/trypsin digest, and histology for the detection of Myxobolus cerebralis in salmonid fishes of Indiana and Michigan.

The objectives of this study were to survey fish from state hatcheries in Indiana and Michigan and to compare the nested polymerase chain reaction (PCR) test with pepsin/trypsin digest (PTD) and histopathology for the diagnosis of whirling disease (WD). One group of 40 and 9 groups of 60 fish heads, for a total of 580 samples, were submitted from hatcheries in Indiana and Michigan. These samples were examined for myxozoan spores using histopathology, PTD, and PCR tests. The heads were hemisectioned, and one half was fixed in 10% neutral-buffered formalin for histopathologic examination. The other half was processed for PTD. Some of the sediment was examined for the presence of myxozoan spores, and the rest was prepared for the nested PCR. Histologic examinations did not reveal Myxobolus cerebralis in any of the 580 samples. One hundred serial step sections, taken at 5-microm intervals, were evaluated for samples with positive spore identification by PTD. Histologic examination of these sections failed to reveal any myxozoan parasites. Myxozoan spores were observed in 16.9% (98/580) of samples in sediment after PTD. Spores morphologically similar to those of M. cerebralis were observed in 1.0% of PTD samples (n = 6). The nested PCR indicated that M. cerebralis spores were present in 0.5% of samples (n = 3). All 3 nested PCR-positive samples came from the same hatchery, however, spores of M. cerebralis were seen in 1 sample, spores of other myxozoan species were seen in the second sample, and spores were not seen in the third sample. When comparing the PTD to the nested PCR test, the PTD diagnosed 1 true positive, 5 false positives, 2 false negatives, and 572 true negatives, for a sensitivity of 33% and a specificity of 99.1%. Screening for M. cerebrallis infection in this study indicated a low prevalence of the disease. Histopathology was a very insensitive indicator of WD. The PCR test was highly specific and was used to differentiate spores of M. cerebralis from similar spores of other species.

Epidemiologic, genetic, and clinical associations among phenotypically distinct populations of Leishmania (Viannia) in Colombia.

Phenotypic characterization of 511 strains of Leishmania, subgenus Viannia, isolated from Colombian patients was conducted based on electrophoretic polymorphisms of 13 isoenzymes. Ninety-one Colombian strains of L. braziliensis were the most heterogeneous, constituting seven zymodemes while 397 L. panamensis and 22 L. guyanensis strains yielded five and three zymodemes, respectively. Phosphogluconate dehydrogenase, nucleoside hydrolase, and superoxide dismutase were the most polymorphic enzymes in this collection of strains, and together with glucose-6-phosphate dehydrogenase, allowed the discrimination of the three aforementioned species. Hierarchical cluster analysis of the zymodemes using Jaccard's coefficient of similarities revealed two clusters, one constituted by L. braziliensis zymodemes, and another by three subgroups consisting of zymodemes of L. panamensis closely related to the species reference strain, another consisting of L. guyanensis zymodemes, and a third group distinguished by new electromorphs of proline iminopeptidase and aspartate aminotransferase that reacted with the L. panamensis-specific monoclonal antibody B-11. Multiple zymodemes of L. panamensis and L. guyanensis were found to be sympatrically transmitted in foci along the Pacific coast. Leishmania braziliensis variants were ubiquitous throughout the territory of Colombia; L. panamensis was prevalent in the western region and L. guyanensis was prevalent in the Orinoco and Amazon river basins in the eastern half of the country. Distinct zymodemes of L. panamensis predominated in the northern and southern regions of the Pacific coast. Nine zymodemes of all three species were isolated from mucosal lesions. Zymodeme 1.1 of L. braziliensis had the highest frequency of mucosal involvement (10% of the cases), and disease caused by this zymodeme had the longest mean time of evolution (31 months; P = 0.002). In addition to being useful in describing epidemiologic relationships, the intraspecific heterogeneity of strains of the Viannia subgenus within and among foci can be used to understand such fundamental questions as the pathogenicity of different populations of parasites, and the induction of cross-protection against related parasites.

A motility function for the paraflagellar rod of Leishmania parasites revealed by PFR-2 gene knockouts.

We demonstrate a functional role for the paraflagellar rod (PFR) in motility of Leishmania mexicana. The PFR is a complex cytoskeletal structure running parallel to the axoneme in the flagella of kinetoplastid protozoa. The PFR is composed of a latticework of protein filaments whose major constituents are two related proteins (PFR-1 and PFR-2 in Leishmania). The molecular details of their assembly into PFR filaments are unknown as is the biological function of the PFR. As an approach to understanding the structure and function of the PFR in Leishmania, we made L. mexicana null mutants of PFR-2. PFR-2 minus parasites grow and divide normally in culture and still express the PFR-1 protein. They lack most of the PFR structure demonstrating that the PFR-2 protein is an essential constituent of the PFR. Detailed ultrastructural analysis of the PFR-2 null mutant reveals the presence of a residual inner substructure of the PFR which contains PFR-1 protein, indicating that PFR-1 can polymerize in the absence of PFR-2. The PFR-2 null mutant displays pronounced changes in flagellar beat waveform and forward swimming velocity, compared to wild type parasites consistent with decreased internal elastic bending resistance in PFR-lacking flagella, and indicating a functional role for the PFR in the motility of Leishmania.

Stage-specific expression of the Leishmania mexicana paraflagellar rod protein PFR-2.

A screen for Leishmania mexicana genes encoding promastigote-specific flagellar proteins resulted in isolation of genes encoding the major components of the paraflagellar rod. One of these, PFR-2, was characterized extensively. PFR-2 genes are present in the genome as a tandem array of three genes designated PFR-2A, PFR-2B, PFR-2C. PFR-2A and PFR-2B are encoded by a 3.1 transcript while PFR-2C is encoded by a 3.8-kb transcript that has a 3' UTR different from that of the 3.1-kb transcript. Both of these mRNAs were 15-fold more abundant in promastigotes than in amastigotes. Two transcripts immediately upstream of the locus were constitutively expressed while two downstream transcripts were fourfold more abundant in promastigotes than in amastigotes. The PFR genes will provide a good model system for analysis of stage-specific gene regulation in Leishmania as well as assist in the characterization of the function and organization of the paraflagellar rod.

A comparative study of diagnosis by the polymerase chain reaction and by current clinical methods using biopsies from Colombian patients with suspected leishmaniasis.

The results of a preliminary trial are reported in which the diagnostic value of a Polymerase Chain Reaction (PCR) specific for Leishmania of the subgenus Viannia was compared with that of currently recommended methods. These methods were microscopic examination of dermal scrapings, in vitro culture of both patient biopsies and aspirates, an in vitro culture of hamster aspirates following inoculation with patient biopsies. The tests were performed on biopsies of Colombian patients with leishmaniasis or with nonleishmanial ethiologies. The outcome of this trial was that PCR was consistently more sensitive than any of the four currently recommended methods of diagnosis, an gave results much faster than the three culture-based methods. Clinical specificity did not match the absolute specificity obtained in the laboratory when tested against purified kDNAs from various Leishmania species. This is thought to be due to the small sample size and to possible subclinical presence of the parasite in the population. The results nevertheless show that, given a more extensive trial directed at clinical validation, PCR can provide the means for early and rapid diagnosis of leishmaniasis. This should reduce morbidity and treatment costs. Further improvements to the method, its introduction in endemic settings and its possible further clinical uses are also discussed.

Epidemiology of cutaneous leishmaniasis in Colombia: a longitudinal study of the natural history, prevalence, and incidence of infection and clinical manifestations.

This prospective study measured the incidence of Leishmania infection, by Leishmanin skin test (LST) conversion, and leishmaniasis, by new acquisition of lesions, in a Leishmania braziliensis endemic area of Colombia, during 7243 person-years. The incidence rate of infection and leishmaniasis varied greatly by village, ranging from 2.8 to 23.0/100 person-years and 0.0 to 20.4/1000 person-years, respectively. Adult males experienced greater rates of both infection and leishmaniasis. Most primary infections (91%) were subclinical initially. Typical scars were predictive of subsequent leishmaniases both for persons initially LST-reactive (risk ratio = 11.3, P = .003) and for those initially nonreactive (risk ratio = 3.2, P = .02). Only one-third of the diagnosed leishmaniasis cases (24/77) were due to newly acquired infections in naive hosts. The relative contribution of existing lesions, recurrences, and new infections to the burden of disease should be considered in the planning of leishmaniasis control programs.

Epidemiology of cutaneous leishmaniasis in Colombia: environmental and behavioral risk factors for infection, clinical manifestations, and pathogenicity.

Through a longitudinal, active surveillance for Leishmania (Viannia) braziliensis and Leishmania (Viannia) panamensis infection and lesions on the Pacific Coast of Colombia, risk factors for infection (leishmanin skin test conversion), leishmanial lesions, and pathogenicity were examined. Risk factor information was obtained prior to and independently of case ascertainment. Similar factors were associated with acquisition of infection and of leishmaniasis, including male sex, age > 10 years, and farming occupation. The behaviors of entering the forest after sunset, hunting, and lumbering were most strongly associated with Leishmania infection independently of age, sex, and farming occupation. Environmental conditions associated with infection, including tall trees near the home, home located > 15 m from the nearest neighbor, and floor and roof made of open material, were less strong predictors of risk. Pathogenicity, the risk of lesion given a new infection, was reduced in those > 30 years of age and those entering the forest frequently.

Correlation between histopathology, immune response, clinical presentation, and evolution in Leishmania braziliensis infection.

Skin biopsies from 221 parasitologically confirmed cases of tegumentary leishmaniasis caused by Leishmania braziliensis spp. were evaluated with respect to histopathology, the qualitative and quantitative nature of the cellular infiltrate, and the presence of Leishmania amastigotes. These variables were cross correlated with the Leishmania-specific immune response, clinical presentation, and response to treatment. Physical evidence of prior leishmanial lesions was associated with the absence of amastigotes (P less than or equal to 0.001) and the presence of giant (P = 0.03) and epitheloid cells (P = 0.03) in the biopsy of the active lesion. The presence of amastigotes was inversely related to the duration of the lesion (P less than or equal to 0.001) and the presence of eosinophils (P less than or equal to 0.01), whereas the presence of adenopathy (P = 0.01), necrosis (P = 0.001), histiocytes (P = 0.001), and increased serum antibody titer (P = 0.02) were directly associated with the presence of amastigotes. The lymphocyte transformation response was correlated with the presence of granulomas (P = 0.001), but showed no correlation with cutaneous delayed type hypersensitivity. The presence of epithelioid (P = 0.04) and giant cells (P = 0.03) was associated with less drug being required to achieve healing. In contrast, necrosis was associated with a greater amount of drug to achieve healing (P = 0.05). The observed correlations between tissue responses and immune and clinical parameters provide further evidence for the role of antibody and other soluble mediators of the cellular immune response in the evolution of disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Leishmanin skin test standardization and evaluation of safety, dose, storage, longevity of reaction and sensitization.

Leishmanin skin test (LST) antigens prepared from Leishmania braziliensis panamensis were compared with respect to sensitivity, specificity, and side effects. Within the dose range 0.5-3.0 x 10(5) promastigotes of L. b. panamensis and 10 x 10(5) promastigotes of combined L. amazonensis and L. b. panamensis, specificity in healthy controls was nearly 100% for all antigens. Sensitivity increased minimally with increasing dose. Lot-to-lot differences were small. Side effects, such as vesiculation and ulceration at the site of LST application increased with antigen dose. Storage under harsh conditions decreased LST potency but not sensitivity while storage at 2-8 degrees C affected neither potency nor sensitivity. Eighty-five percent of parasitologically diagnosed, LST-positive cases of leishmaniasis remained LST-positive when retested six months to three years later. The LST did not sensitive 19 healthy controls who were skin tested twice or thrice.

Mucosal disease caused by Leishmania braziliensis guyanensis.

Three Leishmania strains were isolated from cutaneous and mucosal lesions of a Colombian male. These strains, shown to be phenotypically identical based on isoenzyme polymorphisms and monoclonal antibody reactivity, were identified as Leishmania braziliensis guyanensis. Six clones of the mucosal strain were phenotypically identical to the 3 strains. The clinical presentation of the cutaneous lesions and the geographic origin of the infection were consistent with infection by L. b. guyanensis.