Skin test antigens for immediate hypersensitivity prepared from infective larvae of Strongyloides stercoralis.

More rapid and simplified diagnostic procedures are needed for the diagnosis of strongyloidiasis. One approach is the use of an immediate hypersensitivity skin test that would reliably identify infected people. Accordingly, somatic and excretion/secretion (E/S) antigens were prepared from filariform larvae of Strongyloides stercoralis and were treated to remove possible adventitious agents. By use of a quantitative method for measurement of skin reactions, several preparations of the 2 antigens were tested in uninfected controls and in various groups of patients. Doses of 0.35 microg of E/S and 4 microg of somatic antigens elicited positive skin tests in 82-100% of infected people, depending on clinical status. A lower frequency of positive skin tests was found in strongyloidiasis patients also infected with human T-cell lymphotropic virus type 1. Cross-reactions, especially to somatic antigens, were frequently found in patients with filarial infections. Despite these limitations and the need for further study of specificity, these results provide a basis for future development of a diagnostic skin test antigen for strongyloidiasis.

Influence of human T-cell lymphocytotropic virus type 1 infection on serologic and skin tests for strongyloidiasis.

The aim of this study was to determine whether human T-cell lymphocytotropic virus type 1 (HTLV-1) infection may affect the levels of parasite-specific immunoglobulin (Ig) G and IgE and the positivity of the skin test for strongyloidiasis. Participants included 67 patients with strongyloidiasis (40 without HTLV-1 infection and 27 coinfected with HTLV-1). We determined IgG and IgE levels by enzyme-linked immunosorbent assay, and the immediate hypersensitivity skin test was performed with the metabolic Strongyloides stercoralis antigen. Specific IgE levels and the size of skin reactions in patients without HTLV-1 were higher (P < 0.01) than those observed in patients coinfected with HTLV-1. Additionally, 89% of patients without HTLV-1 had specific IgE and 92.5% had positive skin tests; however, these values were significantly reduced (P < 0.01) in patients coinfected with HTLV-1 (44% and 59%, respectively). These data show that HTLV-1 infection decreases the sensitivity of detection of S. stercoralis-specific IgE, the size of the immediate hypersensitivity reaction, and the sensitivity of these tests in the diagnosis of strongyloidiasis.

HTLV-1 decreases Th2 type of immune response in patients with strongyloidiasis.

Eosinophils, immunoglobulin (Ig)E and cytokines have important roles in defence mechanisms against helminths. In this study, the influence of HTLV-1 infection, characterized by a Th1 type of immune response, was evaluated on the cytokine pattern and parasitic specific IgE response in patients with strongyloidiasis. Patients were divided into four groups: strongyloidiasis without HTLV-1 infection, strongyloidiasis with HTLV-1, HTLV-1 without strongyloidiasis and controls without either helminth infection or HTLV-1. The cytokine profile was determined in supernatants of mononuclear cells stimulated with Strongyloides stercoralis crude antigen and the parasite specific IgE was measured by ELISA. Patients coinfected with HTLV-1 had higher levels of interferon (IFN)-gamma and interleukin (IL)-10 (P < 0.05) and lower levels of IL-5 and IgE (P < 0.05) than patients with strongyloidiasis without HTLV-1. There was an inverse relationship between IFN-gamma and IL-5 (P = 0.01; rs = - 0.37) and between IFN-gamma and parasite specific IgE (P = 0.01; rs = - 0.39), and a direct relationship between IFN-gamma and IL-10 (P = 0.04; rs = 0.35). These data show that coinfection with HTLV-1 decreases IL-5 and IgE responses in patients with strongyloidiasis consistent with a relative switch from Th2 to Th1 response. Immunological responses such as these are important in the control of this helminthic infection.

Leishmaniasis recidivans recurrence after 43 years: a clinical and immunologic report after successful treatment.

We describe a patient with very late recurring leishmaniasis recidivans from whom lesional biopsy samples were obtained during and after topical steroid treatment that demonstrated the ability of the host to contain the parasite in the absence of therapy. Combination therapy with intralesional sodium stibogluconate and oral itraconazole was successful and immunologic data suggest that both CD4(+) and CD8(+) T cell subsets had roles in this disease process.

Interferon-gamma and interleukin-4 responses in relation to serum IgE levels in persons infected with human T lymphotropic virus type I and Strongyloides stercoralis.

Possible immunologic interaction between infection with human T lymphotropic virus type 1 (HTLV-1), a retrovirus, and the intestinal parasite Strongyloides stercoralis was investigated in persons infected with one or both agents. This was done by examining the cytokine responses of peripheral blood mononuclear cells (PBMC) to mitogens and Strongyloides antigen. PBMC of subjects infected with HTLV-1 spontaneously produced interferon (IFN)-gamma with levels that correlated inversely with serum IgE levels. HTLV-1-infected subjects also had poor interleukin (IL)-4 responses to mitogenic stimulation, unlike persons without HTLV-1 infection. It is postulated that the IFN-gamma produced by activated T cells in some HTLV-1-infected persons acts to down-regulate IL-4 with consequent reduction of serum IgE levels. The impaired IgE responses and other effects of IL-4 down-regulation may be contributing factors to more severe disease and impaired response to treatment of strongyloidiasis in some HTLV-1-infected persons.

Recombinant cDNA clones for immunodiagnosis of strongyloidiasis.

Because diagnosis of strongyloidiasis by stool examination is unreliable and because of the potential for serious disease in Strongyloides infections, there is need for improved diagnostic aids to facilitate recognition and treatment of this parasitic infection. Serologic testing, when available, requires antigen preparation from infected primates or dogs that can be difficult to maintain. Several recombinant clones from a cDNA library prepared from the infective stage of Strongyloides stercoralis were characterized. Serologic results indicate that the recombinant proteins were equally or more reactive than the larval somatic antigen. No cross-reactivity with recombinant antigen 5a was found with sera from patients with filarial or intestinal nematode infections. Recombinant antigens 5a and 12a detected parasite-specific IgE and IgG4 antibodies in Strongyloides-infected patients. Sequence analysis showed these antigens to be rich in proline and charged amino acids. Lack of homology from database searches suggests that the antigens are unique. These recombinant antigens should be useful in diagnostic and epidemiologic studies of strongyloidiasis.

Non-ulcerative cutaneous leishmaniasis in Honduras fails to respond to topical paromomycin.

A double-'blind', placebo-controlled trial of topical therapy with 15% paromomycin (aminosidine) and 10% urea in white paraffin was carried out on 53 patients with non-ulcerating cutaneous leishmaniasis in Honduras. Although the treatment was not effective, several unexpected findings emerged from the trial. Leishmania mexicana was found to be the cause of many of the skin lesions in one of the 2 study sites. These lesions were clinically indistinguishable from those caused by L. chagasi, the aetiologic agent previously found for this form of leishmaniasis. This is the first documented report of L. mexicana in Honduras.

Molecular differences between several species of Strongyloides and comparison of selected isolates of S. stercoralis using a polymerase chain reaction-linked restriction fragment length polymorphism approach.

The relationships between the parasitic nematodes of medical importance belonging to the genus Strongyloides was studied using a polymerase chain reaction (PCR)-linked restriction fragment length polymorphism approach. We used several human and dog isolates of S. stercoralis, a monkey isolate of S. fulleborni, and S. ratti, a rodent parasite. The molecular analysis was based on amplification of the internal transcribed spacer and the 5' portion of the 23S-like rRNA gene followed by restriction enzyme digests. The length of the PCR product was specific to each species and varied around 1.5 kilobase pairs. Using nine restriction enzymes, we were able to analyze both interspecific and intraspecific variations. With four restriction enzymes (Taq I, Dde I, Dra I, and Mwo I), human isolates of S. stercoralis from different parts of the world showed identical patterns and could be differentiated from the dog isolate of S. stercoralis. Interspecific differences were readily observed with these and other enzymes. In addition to providing new information on the genomic characteristics of Strongyloides parasites, the results suggest that this technique could be useful for diagnostic and epidemiologic investigations.

Indian kala-azar caused by Leishmania tropica.

Kala-azar, or visceral leishmaniasis, in India is generally assumed to be a result of infection with Leishmania donovani. 15 parasite isolates collected over the past 10 years from patients with classical disease were typed by monoclonal antibodies, isoenzymes, and kDNA analysis. 4 were shown to be L tropica, a species historically associated with cutaneous disease and more recently a mild "visceralising" disease from the Desert Storm experience. The results confirm that L tropica is a co-endemic agent of visceral leishmaniasis in India, and may shed light on the rising frequency of therapeutic unresponsiveness to sodium antimony gluconate, which complicates treatment of this lethal disease.

Ss40: the zinc endopeptidase secreted by infective larvae of Strongyloides stercoralis.

Infective larvae of a pathogenic nematode of humans, Strongyloides stercoralis, release a potent zinc endopeptidase activity which has a broad substrate specificity for constituents of extracellular dermal matrix, including elastin. Specific inhibitors of zinc endopeptidases prevent the penetration of mammalian skin by S. stercoralis larvae. We now report the molecular size and isoelectric point of the S. stercoralis zinc endopeptidase at 40 kDa, pI 5 by zymogram analysis. The activity was not influenced by incubation with beta-mercaptoethanol at 22 degrees C, but was inactivated by incubation at 100 degrees C for 2 min. The enzyme, which we term Ss40, is immunogenic and stimulates humoral IgG antibodies during infection of humans; the activity was immunoprecipitable from ES with pooled infection sera. In addition, a HPLC-enriched Ss40 preparation stimulated the release of histamine from peripheral blood leukocytes of S. stercoralis-infected persons, suggesting that Ss40 is allergenic in humans.

Age-prevalence and household clustering of Strongyloides stercoralis infection in Jamaica.

The epidemiology of Strongyloides stercoralis was studied in families of clinical (reference) cases and their neighbours at endemic foci in Jamaica. Thirteen foci were studied based on the place of residence of a reference case. For each household of a reference case, the 4 most proximal neighbourhood households (spatial controls) were included in the study. Out of 312 persons contacted 244 were followed up using questionnaires, stool examination and serology. Prevalence of infection based on stool examination was 3.5% and on ELISA 24.2%. Prevalence increased with age but was not related to gender. Reference cases were significantly older than the general study population. The prevalence of infection based on both serology and stool examination was significantly higher in reference than in neighbouring households (the reference cases, themselves, were not included in the analysis). Furthermore, prevalence of infection was highest among persons who shared a bedroom with a reference case and decreased significantly with increasing spatial separation. This is indicative of close contact transmission which has not been previously shown for a geohelminth, but which is common among microparasites.

A randomized trial of single- and two-dose ivermectin versus thiabendazole for treatment of strongyloidiasis.

A randomized trial is described comparing ivermectin and thiabendazole for treatment of chronic infection with Strongyloides stercoralis. Subjects received ivermectin (200 micrograms/kg) in a single dose, ivermectin (200 micrograms/kg) on 2 consecutive days, or thiabendazole (50 mg/kg/day) twice daily for 3 consecutive days. Most subjects (94%) had intermittent symptoms, including urticaria, epigastric pain, and diarrhea. Stools were examined 7 days and 1, 3, 6, 10, and 22 months after treatment. Fifty-three subjects completed at least 3 months of follow-up. Only 1 of 34 and 2 of 19 ivermectin and thiabendazole subjects, respectively, had a stool positive for larvae after treatment. Symptoms were relieved in all 3 groups and eosinophil levels returned to normal in 90% of all subjects by 12 months. Nearly 95% of thiabendazole subjects had short-term adverse effects during therapy versus only 18% of those treated with ivermectin. One dose of ivermectin provides safety and efficacy equivalent to thiabendazole with a much lower prevalence of side effects and, consequently, better compliance.

Immunoepidemiologic studies of Strongyloides stercoralis and human T lymphotropic virus type I infections in Jamaica.

Epidemiologic investigations of Strongyloides stercoralis and human T lymphotropic virus type I (HTLV-I) infections were conducted. Of 312 persons contacted, 209 (67%) provided blood and stool samples. Prevalences of S. stercoralis and HTLV-I antibodies were 26.8% and 8.1% (n = 198), respectively, and S. stercoralis larvae were detected in 4%. HTLV-I antibodies were significantly more common in persons positive for S. stercoralis larvae (10 [58.8%] of 17) compared with seropositive larva-negative (4 [8.9%] of 45) or seronegative persons (9 [6.2%] of 145) (P < .002). IgE levels increased with age in S. stercoralis-seropositive persons who were HTLV-I negative (P < .002). However, there was an age-related depression of serum IgE in HTLV-I-positive positive persons (P < .003) that was sufficient to annul the IgE level-raising effect of S. stercoralis seropositivity. The data provide evidence that HTLV-I infection is associated with increased frequency of larvae in the stool of S. stercoralis-infected persons and suggest that the mechanism may involve suppression of the IgE response.

Identification and genetic comparison of leishmanial parasites causing viscerotropic and cutaneous disease in soldiers returning from Operation Desert Storm.

Six Leishmania major and seven L. tropica parasites were isolated and identified from participants in Operation Desert Shield/Storm. A complete enzyme analysis (21 enzymes) revealed that there was enzyme polymorphism among the isolates of each species group. Any one Desert Storm L. major isolate could differ from any other for 1-3 enzymes, and any L. tropica isolate could differ from any one other for up to eight enzymes. Enzyme polymorphism data from other L. major and L. tropica isolates from Africa and the Middle East region were obtained and combined with the Desert Storm data to produce population enzyme polymorphism estimates. Results from these population data indicated that L. major parasites could be expected to differ from each other for as many as eight enzymes and still be L. major, and similarly, L. tropica isolates could differ for as many as 14 enzymes. These expected isolate variation extremes have not been observed among the isolates studied. All L. major and most L. tropica isolates were from patients who, as expected, presented with cutaneous disease, but the Desert Storm and two Kenyan patients infected with L. tropica presented with a viscerotropic disease, the symptoms of which are unlike those of classic visceral leishmaniasis. Such unrecognized presentation for these L. tropica-infected patients indicates that both parasite and patient can play critical roles in disease manifestations. The Desert Storm isolates are, as indicated, either L. major or L. tropica.

In vivo cytokine profiles in patients with kala-azar. Marked elevation of both interleukin-10 and interferon-gamma.

The immunological mechanisms underlying the susceptibility to disseminated visceral parasitism of mononuclear phagocytes in patients with kala-azar remain undefined. Resistance and susceptibility are correlated with distinct patterns of cytokine production in murine models of disseminated leishmanial disease. To assess lesional cytokine profiles in patients with kala-azar, bone marrow aspirates were analyzed using a quantitative reverse transcriptase PCR technique to amplify specific mRNA sequences of multiple Th1-, Th2-, and/or macrophage-associated cytokines. Transcript levels of IL-10 as well as IFN-gamma were significantly elevated in patients with active visceral leishmaniasis; IL-10 levels decreased markedly with resolution of disease. These findings suggest that IL-10, a potent, pleiotropic suppressor of all known microbicidal effector functions of macrophages, may contribute to the pathogenesis of kala-azar by inhibiting the cytokine-mediated activation of host macrophages that is necessary for the control of leishmanial infection.

Cutaneous leishmaniasis: review of 59 cases seen at the National Institutes of Health.

Fifty-nine cases of cutaneous leishmaniasis seen at the National Institutes of Health in Bethesda, Maryland, are reviewed. The group of patients involved was unique in that the majority were American civilians, their disease was acquired in many different endemic areas of the world, and their illnesses represented all points on the clinical spectrum of cutaneous disease. The majority of American patients acquired leishmaniasis while engaging in activities related to their occupations. Cutaneous disease acquired in the New World usually consisted of one or two lesions, while multiple lesions often characterized Old World infections with Leishmania major. Patients with chronic relapsing or diffuse cutaneous leishmaniasis were native to endemic areas and were infected at an early age. Even the localized form of cutaneous leishmaniasis was often extensive and difficult to treat. Diagnosis with culture and identification of the parasite to the subspecies level is instrumental in the selection of optimal therapy. Cutaneous leishmaniasis may be encountered increasingly often in the United States because of the frequent international travel of U.S. residents and the influx of immigrants from endemic areas of the world.

Strongyloides stercoralis hyperinfection in a carrier of HTLV-I virus with evidence of selective immunosuppression.

A patient with near fatal Strongyloides hyperinfection syndrome is briefly described. Investigation for possible risk factors for this parasitic infection disclosed that he was a carrier of human T-cell leukemia virus type I (HTLV-I), but without evidence of disease due to this retrovirus. Over the next few years, the patient's serum antibody levels of IgG to S. stercoralis larvae declined and became undetectable despite continued infection with the parasite. Repeated courses of appropriate treatment cleared the parasitic infection only temporarily. The patient was also found to have undetectable total serum IgE and a negative immediate hypersensitivity skin test to S. stercoralis antigens. Five of six other patients with HTLV-I-associated disease and with or without strongyloidiasis were also found to have very low total serum IgE levels. It is postulated that HTLV-I infection in certain individuals may selectively impair immune responses that are critical in controlling strongyloidiasis.