Strongyloides stercoralis: ultrastructural study of newly hatched larvae within human duodenal mucosa

Aim—To investigate the ultrastructural features of the newly hatched larvae of Strongyloides stercoralis in human duodenal mucosa. Methods—Duodenal biopsies from an AIDS patient were studied by transmission electron microscopy to investigate morphology, location, and host–worm relations of newly hatched larvae. Results—Newly hatched larvae were found in the Lieberkuhn crypts within the tunnels formed by migration of parthenogenic females. Delimiting enterocytes were compressed. Release of larvae into the gut lumen was also documented. It was shown that both a thin and a thick membrane surrounded the eggs and larvae, as a tegument derived respectively from parasite and host. Segmentary spike-like waves, caused by contractures of worm body musculature, were observed on the surface of newly hatched larvae, and their intestinal lumen was closed and empty, with no budding microvilli. Immaturity of the cuticle and some degree immaturity of amphidial neurones were found, but there was no evidence of either immaturity or signs of damage to other structures. Conclusions—Newly hatched larvae of S stercoralis appear to be a non-feeding immature stage capable of active movement through the epithelium, causing mechanical damage. The tegument resulting from the thin and the thick membrane may protect the parasite and reduce any disadvantage caused by immaturity. Key Words: Strongyloides stercoralis • ultrastructure • larvae • immune deficienc

Cross-reactivity of antibodies in human infections by the kinetoplastid protozoa Trypanosoma cruzi, Leishmania chagasi and Leishmania (Viannia) braziliensis Reatividade cruzada de anticorpos em pacientes com infecções pelos protozoários Trypanosoma cruzi, Leishmania chagasi e Leishmania (Viannia) braziliensis

We have detected antibodies, in the sera of Chagas disease, Kala-azar and Mucocutaneous leishmaniasis patients, that bind multiple antigens shared between the three causative agents. The Chagas disease sera showed 98 to 100% positive results by ELISA when the Leishmania braziliensis and Leishmania chagasi antigens were used, respectively. The Kala-azar sera showed 100% positive results with Trypanosoma cruzi or L. braziliensis antigens by immunofluorescence assays. The antibodies in the sera of Mucocutaneous leishmaniasis patients showed 100% positive results by ELISA assays with T. cruzi or L. chagasi antigens. Furthermore, the direct agglutination of L. chagasi promastigotes showed that 95% of Kala-azar and 35% of Mucocutaneous leishmaniasis sera agglutinated the parasite in dilutions above 1:512. In contrast, 15% of Chagas sera agglutinated the parasite in dilutions 1:16 and below. Western blot analysis showed that the Chagas sera that formed at least 24 bands with the T. cruzi also formed 13 bands with the L. chagasi and 17 bands with the L. braziliensis. The Kala-azar sera that recognized at least 29 bands with the homologous antigen also formed 14 bands with the T. cruzi and 10 bands with the L. braziliensis antigens. Finally, the Mucocutaneous leishmaniasis sera that formed at least 17 bands with the homologous antigen also formed 10 bands with the T. cruzi and four bands with the L. chagasi antigens. These results indicate the presence of common antigenic determinants in several protozoal proteins and, therefore, explain the serologic cross-reactions reported here.<br>Foram detectados anticorpos, nos soros de pacientes com doença de Chagas, Calazar e Leishnnaniose cutâneo-mucosa, que se ligam a antígenos compartilhados pelos três agentes causais. Os pacientes chagásicos mostraram 98 a 100% de soropositividade pelo ELISA quando antígenos de Leishmania braziliensis e de Leishmania chagasi foram usados, respectivamente. Os soros de Calazar mostraram resultados positivos com antígenos de Trypanosoma cruzi ou com L. braziliensis pela imunofluorescência. Ademais, os anticorpos nos soros de pacientes com Leishmaniose cutâneo-mucosa tinham 100% de resultados positivos pelo ELISA com antígenos de T. cruzi ou de L. chagasi. Ademais, a aglutinação direta de promastigotas de L. chagasi mostrou que 95% dos soros de Calazar e 35% de Leishmaniose cutâneo-mucosa algutinaram o parasito em diluições acima de 1:512. Em contraste, 15% dos soros chagásicos aglutinaram o parasito na diluição de 1:16 ou abaixo. Análises pelo Western blot mostraram que os soros chagásicos que formaram pelo menos 24 bandas com antígeno de T. cruzi também foramaram 13 bandas com antígeno de L. chagasi e 17 bandas com L. braziliensis. Os soros de Calazar que reconheceram pelo menos 29 bandas com o antígeno homólogo também formaram 14 bandas com o T. cruzi e 10 bandas com L. braziliensis. Finalmente, os soros de Leishmaniose cutâneo-mucosa que formaram pelo menos 17 bandas com o antígeno homólogo também formaram 10 bandas com os antígenos de T. cruzi e quatro com L. braziliensis. Esses resultados indicam a presença de determinantes antigênicos comuns em várias proteínas desses protozoários e, portanto, explicam as reações sorológicas cruzadas descritas aqui

Serodiagnosis of strongyloidiasis. The application and significance Aplicação e significado do diagnóstico sorológico na estrongiloidíase

Parasitological diagnosis based on the faecal examination is frequently difficult in cases of chronic, low-level S. stercoralis infection. Even when a newly developed sensitive method (an agar plate culture) is applied, it is essential to examine faecal samples repeatedly to achieve a correct diagnosis. Additionally, it is important to note that a negative result does not necessarily indicate the unequivocal absence of the infection. On the other hand, several serological tests which have recently been developed for strongyloidiasis have proven reliable when used to complement parasitological examination. We have developed two serological tests, ELISA and GPAT, to demonstrate Strongyloides infection and possible applications of the serological tests for diagnosis, mass-screening, epidemiological study and postchemotherapy evaluation of strongyloidiasis were reviewed based on our recent studies.<br>O diagnóstico parasitológico baseado no exame de fezes é muitas vezes difícil, principalmente nos casos de infecções crônicas ou leves pelo S. stercoralis. Mesmo utilizando o mais novo e sensível método (cultura em placas de ágar) é essencial examinar repetidamente as amostras fecais, para um diagnóstico correto. É importante ressaltar também que o resultado negativo não indica de modo inequívoco a ausência da infecção. Por outro lado, vários testes sorológicos recentemente desenvolvidos para estrongiloidíase tem provado a sua eficácia quando usados para complementar exames parasitológicos. Para demonstrar infecção por Strongyloides desenvolvemos dois tipos de testes sorológicos - ELISA e GPAT - e, com base em nossos recentes estudos, apresentamos uma opinião sobre sua possível aplicação para screening em massa, estudos epidemiológicos e avaliação pós-tratamento de estrongiloidíases