Schistosoma mansoni: schistosomulicidal activity of macrophages isolated from liver granulomas of infected mice

Mice infected with Schistosoma mansoni develop T cell-mediated granulomatous reactions around disseminated parasite eggs. In this study, granuloma-derived leucocytes have been examined for schistosomulicidal capacity by the use of in vitro cytotoxicity assays. Adherent macrophages, that were shown by electron microscopy to exhibit no gross morphological abnormalities, were unable to mediate significant mortality in the absence of serum factors. When cocultured with immune serum and complement, however, these cells killed +/- 26% of the larvae at a cell:target ratio of 5000:1. In contrast, granuloma-derived cell populations that were enriched for eosinophils (50-70% eosinophil content) showed only minimal cytotoxic potential. This may be related to observed structural changes in the eosinophil lysosomal granules, or perhaps to blocking of the cell-surface receptors by immune complexes. It is concluded that granuloma macrophages, activated by egg antigen-sensitised T lymphocytes, may serve as effector cells in immunity to schistosomules.     

Taenia solium: cell reactions to the larva (Cysticercus cellulosae) in naturally parasitized, immunized hogs

In hogs naturally infected with Taenia solium larvae (i.e., Cysticercus cellulosae), we studied the host response induced by antigens obtained from the larvae. Histopathological studies of cysticerci removed after 4 and 8 weeks of immunization showed an intense inflammatory reaction surrounding the larvae. The response was greater in the 8-week specimens. A dense layer of eosinophils was in close contact with the external membrane of the bladder wall and, in several cases, the eosinophils had infiltrated this tegument. Many eosinophils were seen in the spiral canal of larvae. This infiltration by eosinophils increased with time. Preparations from the 8-week samples showed many degenerated and disrupted eosinophils whose granules were found in close contact with the outer membrane of the larval tegument and, in some cases, had entered through the broken surface of this structure. More than 90% of the larvae were found in various stages of degeneration; the rest were completely destroyed and surrounded by a mass of eosinophils. After immunization, peripheral blood eosinophilia increased to 17%, whereas the eosinophilia of the control hog was 4% throughout the study. The larval worms removed from control hogs showed intact structures, with a low degree of infiltration by eosinophils and a discrete inflammatory reaction surrounding the bladder wall of the larvae.     

Experimental paracoccidioidomycosis of hamster inoculated in the cheek pouch

We compared the granuloma morphology and immune response of hamsters inoculated withParacoccidioides brasiliensis (Pb) into the cheek pouch, which lacks lymphatic drainage, and into the footpad, which is rich in lymphatics. Our objective was to better understand the modulation ofPb granuloma in an immunocompetent animal inoculated in an immunologically privileged site. The humoral immune response (ELISA) and cell mediated immunity (footpad test) became positive on days 7 and 14, respectively in animals inoculated into footpad and on days 35 and 60 in animals inoculated into the pouch. Typical epithelioid granulomas were observed at both sites on day 14. The number of fungi gradually decreased from the beginning of the experiment in footpad lesions, but only after day 35 in pouch granulomas, when cell mediated immunity was detectable. The results indicate that typical epithelioid paracoccidioidomycotic granulomas may develop in the absence of a detectable immune response; however, they are incapable of controlling fungal reproduction. Lack of lymphatic drainage delays the appearance of a detectable immune response, but with time fungi escape from the pouch, elicit an immune response and reach other organs. Our results further indicate the importance of the lymphatics in the pathogenesis of paracoccidioidomycosis.Abbreviations HCP hamster cheek pouch - Pb Paracoccidioides brasiliensis - Pbmycosis Paracoccidioidomycosis     

Long-term feeding a high-fat diet causes histological and parasitological effects on murine schistosomiasis mansoni outcome

This study investigated whether long-term feeding a high-fat diet (HFC) has an effect on schistosomiasis mansoni outcome compared to standard chow diet (SC). Swiss Webster female mice (3 wk old) fed each diet over 5 months, and then were infected with 50 Schistosoma mansoni cercariae. Their nutritional status was assessed by monitoring growth rates twice a week and measuring serum levels of lipoproteins. Mice were euthanised 63 days after infection. Parasitological and liver histological analyses were performed. The levels of TC, HDL-C and LDL-C, fecal and tissue schistosome eggs were statistically different (p<0.05) between groups. Livers from HFC mice showed exudative, exudative/exudative-productive, exudative-productive and productive granulomas, some degree of hepatic steatosis and focal necrosis. Mice fed normal-chow did not present productive granulomas and hepatic steatosis. The morphometric evaluation of hepatic granulomas did not reach statistical significance (p>0.05) between diets assayed. The high-fat diet for long-term produces effects on schistosomiasis mansoni outcome.     

Macrophage response to <Emphasis Type="Italic">Mycobacteriumtuberculosis</Emphasis> infection

The immune response to Mycobacterium tuberculosis (Mtb) infection is the formation of multicellular lesions, or granolomas, in the lung of the individual. However, the structure of the granulomas and the spatial distribution of the immune cells within is not well understood. In this paper we develop a mathematical model investigating the early and initial immune response to Mtb. The model consists of coupled reaction-diffusion-advection partial differential equations governing the dynamics of the relevant macrophage and bacteria populations and a bacteria-produced chemokine. Our novel application of mathematical concepts of internal states and internal velocity allows us to begin to study this unique immunological structure. Volume changes resulting from proliferation and death terms generate a velocity field by which all cells are transported within the forming granuloma. We present numerical results for two distinct infection outcomes: controlled and uncontrolled granuloma growth. Using a simplified model we are able to analytically determine conditions under which the bacteria population decreases, representing early clearance of infection, or grows, representing the initial stages of granuloma formation.     

Lipolytic enzymes in Mycobacterium tuberculosis

Mycobacterium tuberculosis is a bacterial pathogen that can persist for decades in an infected patient without causing a disease. In vivo, the tubercle bacillus present in the lungs store triacylglycerols in inclusion bodies. The same process can be observed in vitro when the bacteria infect adipose tissues. Indeed, before entering in the dormant state, bacteria accumulate lipids originating from the host cell membrane degradation and from de novo synthesis. During the reactivation phase, these lipids are hydrolysed and the infection process occurs. The degradation of both extra and intracellular lipids can be directly related to the presence of lipolytic enzymes in mycobacteria, which have been ignored during a long period particularly due to the difficulties to obtain a high expression level of these enzymes in M. tuberculosis. The completion of the M. tuberculosis genome offered new opportunity to this kind of study. The aim of this review is to focus on the recent results obtained in the field of mycobacterium lipolytic enzymes and although no experimental proof has been shown in vivo, it is tempting to speculate that these enzymes could be involved in the virulence and pathogenicity processes.     

Chemokines and tuberculosis

Mycobacterium tuberculosis is a respiratory pathogen responsible for tuberculosis. A primary pathologic feature of M. tuberculosis infection is the formation of a granuloma. Immune cells migrate to the lung and then through the lung to the site of infection to form a granuloma. This structure contains the infection, and is often maintained for a long period of time. The signals responsible for granuloma formation and maintenance are largely unknown. Since chemokines and chemokine receptors direct cells to specific sites within the tissues, it is plausible that these cells participate in granuloma formation. In this review, the current literature on chemokines and M. tuberculosis infection, as well as the specific role that tumor necrosis factor alpha (TNF-) plays in granuloma formation and chemokine expression are discussed.     

Immunomodulatory effects of IL-12 released from poly-N-acetyl glucosamine gel matrix during schistosomiasis infection

We have reported recently that Interleukin-12 (IL-12) released from poly-N-acetyl glucosamine gel matrix (F2 gel/IL-12) is more effective than free IL-12 to enhance vaccination of mice with Schistosoma soluble worm antigen preparation. The aim of this study is to evaluate the effect of F2 gel/IL-12 on the inflammatory responses in mice undergoing schistosomiasis infection in absence of vaccination. To achieve this, mice undergoing Schistosoma mansoni infection or cured from this infection, after treatment with praziquantil (PZQ), were treated with subcutaneous injection of IL-12 for 3 consecutive days or once with F2 gel loaded with IL-12 (F2 gel/IL-12). The treatment was started on day 35 days after infection. For infection, mice were infected with 100 cercariae of S. mansoni using tail immersion method. We found that treatment with F2 gel/IL-12 induced significant decreases in the egg burden with a moderate reduction in the size of granuloma and decrease in the cellular granulomatous reaction in the lung as compared to infected mice treated with IL-12. These effects of F2 gel/IL-12 were more pronounced in infected mice previously treated with the anti-schistosomal drug PZQ. The total numbers of white blood cells in all treated mice showed similar profile. Treatment with IL-12 or F2 gel/IL-12, however, showed significant reduction in the number of mononuclear cells when compared with non-treated infected mice. In conclusion, this study showed the ability of IL-12 released from F2 gel to lower the inflammatory response to Schistosoma infection even in absence of vaccination.     

Three-dimensional study of epithelioid cells by a quick-freezing and deep-etching method in muramyl dipeptide-induced granulomas

The three-dimensional ultrastructure of epithelioid cells was studied by the quick-freezing and deepetching (QF-DE), as well as the freeze-substitution (QF-FS) methods. The granulomas were induced in rats by injecting muramyl dipeptide (MDP) into the hind footpads. At 3 weeks after the injection, the footpads were perfused with a fixative, excised, and quickly frozen to prepare the replica membranes. Some unfixed footpads were also quickly frozen and freeze-substituted. Dense networks of intermediate filaments, connected with the nuclei, mitochondria and other vesicular cell organelles, were observed throughout the cytoplasm of epithelioid cells by the QF-DE method. A few actin filaments were located in filopodia and just beneath the cell membranes. Interdigitation of the cell membranes between adjacent cells was clearly demonstrated by the QF-FS method and clathrin-coated pits were identified at the base of interdigitating filopodia. In addition, the exact moment of fusion between endosomes and lysosomes was ascertained by the same method. These results suggest that the cytoskeletal organization of epithelioid cells resembles that of epithelial cells rather than actively motile macrophages.     

Schistosoma mansoni: peripheral and tissue eosinophilia in infected rats.

Peripheral eosinophilia is induced in Sprague-Dawley rats following infection with cercariae of Schistosoma mansoni. Beginning 3 weeks after infection, peripheral eosinophil levels rise above the baseline range; they reach peak values during the fifth week. Following a decline from peak values, peripheral eosinophil levels remain elevated and are observed to fluctuate for the next 5 months. The magnitudes of both the initial peak response at 5 weeks and the subsequent chronic level of peripheral eosinophils are dependent upon dose of cercariae. The initial peak response phase of peripheral eosinophilia coincides in time with the period of adult worm elimination (Weeks 4–6) in the schistosome-infected rat. Histological examination of the liver at 5 weeks after infection reveals eosinophil-rich inflammatory reactions associated with both live and dead worms residing in the portal blood vessels. Around live worms the inflammatory cells are localized in a perivascular arrangement; around dead worms these cells are in the vascular lumen in contact with destroyed worms. The chronic phase of peripheral eosinophilia is associated, in part, with inflammatory reactions surrounding eggs deposited in the liver by the few worm pairs which survive more than 6 weeks and remain within the liver. Histological examination during this period reveals granulomatous lesions within the liver surrounding eggs and dead worms. The granulomas are predominately monocytic (lymphocytes, macrophages) at 11 and 16 weeks. The initial peak response phase of peripheral eosinophilia appears to be a marker for tissue-localized reactions of eosinophils with worms. There are relationships between inflammatory reactions and survival of adult worms.