Toxocara canis and the allergic process

The protective effect of infectious agents against allergic reactions has been thoroughly investigated. Current studies have demonstrated the ability of some helminths to modulate the immune response of infected hosts. The objective of the present study was to investigate the relationship between Toxocara canis infection and the development of an allergic response in mice immunised with ovalbumin (OVA). We determined the total and differential blood and bronchoalveolar lavage fluid cells using BALB/c mice as a model. To this end, the levels of interleukin (IL)-4, IL-5 and IL-10 and anti-OVA-IgE were measured using an ELISA. The inflammatory process in the lungs was observed using histology slides stained with haematoxylin and eosin. The results showed an increase in the total number of leukocytes and eosinophils in the blood of infected and immunised animals at 18 days after infection. We observed a slight lymphocytic inflammatory infiltrate in the portal space in all infected mice. Anti-OVA-IgE levels were detected in smaller proportions in the plasma of immunised and infected mice compared with mice that were only infected. Therefore, we concluded that T. canis potentiates inflammation in the lungs in response to OVA, although anti-OVA-IgE levels suggest a potential reduction of the inflammatory process through this mechanism.

Parasitological characteristics and tissue response in the abomasum of sheep infected with Haemonchus spp

A histopathological study was conducted on the abomasal mucosa of 40 Corriedale sheep exposed to natural infection with Haemonchus spp. The sheep were allowed to graze on contaminated pastures for 14 days and, after being housed for 28 days, they were slaughtered. Fecal samples were collected for fecal egg counts (FEC) and abomasum samples were obtained for histopathological examination and eosinophil, mast cell and globule leucocyte counts. The number of Haemonchus spp. present in the abomasum was estimated from a 10 per cent aliquot of its content. The number of eggs per female was estimated for 10 Haemonchus spp. females collected from each animal. The following significant correlation coefficients were obtained between the characteristics analyzed: number of Haemonchus and FEC (r = 0.86), female length and number of eggs per female (r = 0.60), female length and FEC (r = 0.53), number of eosinophils and number of Haemonchus (r = 0.48), number of eosinophils and number of globule leucocytes (r = 0.54), number of mast cells and female length (r = -0.39), and number of mast cells and number of globule leucocyte (r = 0.34). The characteristics that showed the highest correlation with animal load was FEC

Immunological system and Schistosoma mansoni: co-evolutionary immunobiology. What is the eosinophil role in parasite-host relationship?

Schistosomes, ancestors and recent species, have pervaded many hosts and several phylogenetic levels of immunity, causing an evolutionary pressure to eosinophil lineage expression and response. Schistosoma mansoni adult worms have capitalized on the apparent adversity of living within the mesenteric veins, using the dispersion of eggs and antigens to other tissues besides intestines to set a systemic activation of several haematopoietic lineages, specilly eosinophils and monocytes/macrophages. This activation occurs in bone marrow, spleen, liver, lymph nodes, omental and mesenteric milky spots (activation of the old or primordial and recent or new lymphomyeloid tissue), increasing and making easy the migration of eosinophils, monocytes and other cells to the intestinal periovular granulomas. The exudative perigranulomatous stage of the periovular reaction, which present hystolitic characteristics, is then exploited by the parasites, to release the eggs into the intestinal lumen. The authors hypothesize here that eosinophils, which have a long phylogenic story, could participate in the parasite-host co-evolution, specially with S. mansoni, operating together with monocytes/macrophages, upon parasite transmission.

The enignatic eosinophil: investigation of the biological role of eosinophils in parasitic helminth infection

In many helminth infected hosts the number of eosinophils increases dramatically, often without any concurrent increases in the number of other leukocytes, so that eosinophils become the dominant cell type. Many experimental investigations have shown that the eosinophilia is induced by interleukin-5 (IL-5) but its functional significance remains unclear. Mice genetically deficient in IL-5 (IL-5-/-) have been used to evaluate the functional consequences of the IL-5 dependent eosinophilia in helminth infected hosts. Host pathology and level of infection were determined in IL-5-/- and wild mice infected with a range of species representative of each major group of helminths. The effects of IL-5 deficiency were very heterogeneous. Of the six species of helminth examined, IL-5 dependent immune responses had no detectable effect in infections with three species, namely the cestodes Mesocestoides corti and Hymenolepis diminuta and the trematode Fasciola hepatica. In contrast, IL-5 dependent immune responses were functionally important in mice infected with three species, notably all nematodes. Damage to the lungs caused by migrating larvae of Toxocara canis was reduced in IL-5-/- mice. Infection of the intestine by adult stages of either Strongyloides ratti or Heligmosomoides polygyrus were more severe in IL-5-/- mice. Adult intestinal nematodes were clearly deleteriously affected by IL-5 dependent processes since in its presence there were fewer worms which had reduced fecundity and longevity. The implications of these reults for the viability of using inhibitors of IL-5 as a therapy for asthma are considered.

Cytokines in the modulation of eosinophilia

In this review we discuss our recently results showing interleukin 5 (IL-5) involvement in eosinophil migration and in the maintenance of eosinophilia in blood, bone marrow, lung and peritoneal cavity, in a visceral larva migrans syndrome model using guinea-pigs infected with Toxocara canis. We also describe the sequential release of TNF-a and IL-8 during the course of infection, and the interaction between these cytokines and IL-5 during infection. Finally, we propose a new biological role for IL-5, at least in our model, as a modulator of IL-8 release and secretion.

Nitric oxide mediates the microbicidal activity of eosinophils

There are several experimental evidences that nitric oxide (NO) is involved in the microbicidal activity of macrophages against a number of intracellular pathogens including Leishmania major, Trypanosoma cruzi, Toxoplasma gondii. It is also well known that eosinophils (EO) have microbicidal activity against many parasites such as Schistosoma mansoni, Trichenella spiralis, T. cruzi and L. amazonensis. The purpose of this study was to investigate if NO is involved in the microbicidal activity of EO against L. major. Eosinophils harvested from peritoneal cavity of rats released spontaneously after 24 and 48 hr a small amount of nitrite. This release was enhanced by the treatment of cells with IFN-gamma (200 IU/ml). This release was blocked by addition of the NO synthase inhibitor, L-NIO (100µM) into the culture. To determine the leishmanicidal activity of eosinophils the parasites were incubated with activated eosinophils with IFN-gamma and the abiblity of surviving parasites to incorporate [3H] thymidine was evaluated. IFN-gamma-activated eosinophils were able to kill L. major and to release high levels of nitrite. The ability to destroy L. major and the release of NO were completely blocked by L-NIO. These results indicate that activated eosinophils release NO which is involved in the microbicidal activity of these cells against L. major.

Eosinofilia: revisión del tema / Eosinophilia: a literature review

Se efectuó la revisión referente a la biología y función de los eosinófilos. En qué padecimientos se encuentran elevados, sus causas extrínsecas y se hace énfasis en su relación en endo y ectoparasitosis.

Significado do periovular na esquistossomose / Significance of periovular granuloma in shistosomiasis

Näo está ainda bem definido qual é o significado funcional do granuloma periovular na esquistossomose. Para alguns, as células inflamatórias nos granulomas, sobretudo os eosinófilos, atacam e destroem o miracídio, como comprovam evidências obtidas in vitro e in vivo. Também näo há informaçöes se os vários tipos de granulomas, com morfologia variável conforme o tempo da infecçäo e conforme o órgäo em que estäo localizados, têm correlaçäo com maior ou menor atividade funcional. Para estudar este assunto foram infectados camundongos com 30 cercárias do Schistosoma mansoni. Para se investigar a sobrevivência dos miracídios nos tecidos recorreu-se a uma quimioterapia reconhecidamente curativa para se eliminar a possibilidade da chegada de novos ovos. A viabilidade dos miracídios foi verificada pelo teste da eclosäo e pela evidenciaçäo dos movimentos ciliares e das células em "chama". Os animais tratados foram sacrificados sequencialmente, tendo-se feito perfusäo para a recuperaçäo de vermes, contagem de ovos por grama de tecido e oograma. Para correlaçäo com o tempo de infecçäo foram sacrificados animais com 8 e com 20 semanas de infectados, foram medidos os diâmetros dos granulomas e estudado as suas respectivas composiçöes celulares. Para a obtençäo de muitos granulomas pulmonares foram infectados camundongos nos quais se praticou uma ligadura parcial da veia porta. Foi observado que os camundongos infectados pelo S. mansoni mostraram a presença de ovos viáveis nos tecidos até 17 dias após o tratamento curativo da esquistossomose. Neste particular näo houve diferença com o tipo morfológico dos granulomas. Tanto o granuloma hepático, mal delimitado e com forte componente exsudativo da infecçäo recente, como aquele bem circunscrito, pequeno e proliferativo, da infecçäo tardia, bem como o granuloma pulmonar ou intestinal, em todos eles, houve evidência de que o miracidio podia sobreviver até 17 dias após a suspensäo da postura. Estes resultados estäo em desacordo com os relatos de estudos in vitro e com certas deduçöes a partir de achados in vivo que tendem a indicar os eosinófilos como as células efetoras encarregadas da destruiçäo dos ovos. Por outro lado, o presente estudo da apoio à definiçäo de que o granuloma é uma reaçäo inflamatória focal destinada a sequestrar antígenos de baixa difusibilidade. Na realidade, os resultados repetidamente obtidos no presente trabalho indicam o granuloma periovular na esquistossomose como sendo uma reaçäo que resulta como protetora dos tecidos do hospedeiro contra a açäo irritante, tóxica ou lítica dos produtos do miracídio, e muito menos como uma resposta efetiva para atacar ou destruir o ovo do S. mansoni nos tecidos