Immunoactivation and immunopathogeny during active visceral leishmaniasis

Visceral leishmaniasis is caused by protozoan parasites of the Leishmania donovani complex. During active disease in humans, high levels of IFN-γ and TNF-α detected in blood serum, and high expression of IFN-γ mRNA in samples of the lymphoid organs suggest that the immune system is highly activated. However, studies using peripheral blood mononuclear cells have found immunosuppression specific to Leishmania antigens; this poor immune response probably results from Leishmania antigen-engaged lymphocytes being trapped in the lymphoid organs. To allow the parasites to multiply, deactivating cytokines IL-10 and TGF-β may be acting on macrophages as well as anti-Leishmania antibodies that opsonize amastigotes and induce IL-10 production in macrophages. These high activation and deactivation processes are likely to occur mainly in the spleen and liver and can be confirmed through the examination of organ samples. However, an analysis of sequential data from studies of visceral leishmaniasis in hamsters suggests that factors outside of the immune system are responsible for the early inactivation of inducible nitric oxide synthase, which occurs before the expression of deactivating cytokines. In active visceral leishmaniasis, the immune system actively participates in non-lymphoid organ lesioning. While current views only consider immunocomplex deposition, macrophages, T cells, cytokines, and immunoglobulins by diverse mechanism also play important roles in the pathogenesis.

Low sensitivity of polymerase chain reaction for diagnosis of tuberculous meningitis in southeastern Brazil

Two polymerase chain reaction (PCR) protocols showed low sensitivity (36% and 53% for TB AMPLICOR and MPB64 nested PCR, respectively), when compared with classic microbiological methods (73% and 54% for Ziehl-Neelsen staining and culture, respectively), in the diagnosis of tuberculous meningitis in 91 patients in southeastern Brazil. Only three PCR-positive, microbiologically negative patients were found. Analysis of sequential cerebrospinal fluid samples by nested PCR detected Mycobacterium tuberculosis DNA up to 29 days after the introduction of antituberculosis chemotherapy.

Pancreatic lesions in acute experimental Chagas' disease

BACKGROUND: Chagas' disease is an endemic tropical affliction found from southern United States to Argentina. The acute phase of this disease is difficult to study in man because the symptoms are non-specific and most cases require no medical assistance. Experimental models have been developed for sequential studies, and intense parasitism in all organs and tissues, including the pancreas, have been detected in the acute phase. PURPOSE: To evaluate the involvement of the pancreas in acute experimental Chagas' disease in a mouse model by histopathological characterization. CASUISTIC AND METHODS: Ten BALBc mice, about 20 g, injected i.p. with 100 000 forms of the Y strain of Trypanosoma cruzi were used. The animals were sacrificed after 14 days of infection. Fragments of pancreas were processed by conventional paraffin embedding and hematoxylin-eosin staining. RESULTS: Ruptured pseudocysts and release of parasites to the extracellular medium caused by necrosis of acinar and duct cells and foci of fat were the most striking histopathological features of acute Chagasic pancreatitis. CONCLUSION: Parasitism is the main cause of acute pancreatitis in Chagas' disease.

Reduction in diastolic blood pressure and cardiovascular mortality in nondiabetic hypertensive patients. A reanalysis of the HOT study

OBJECTIVE: To use published Hypertension Optimal Treatment (HOT) Study data to evaluate changes in cardiovascular mortality in nondiabetic hypertensive patients according to the degree of reduction in their diastolic blood pressure. METHODS: In the HOT Study, 18,700 patients from various centers were allocated at random to groups having different objectives of for diastolic blood pressure: <=90 (n=6264); <=85 (n=6264); <=80mmHg (n=6262). Felodipine was the basic drug used. Other antihypertensive drugs were administered in a sequential manner, aiming at the objectives of diastolic blood pressure reduction. RESULTS: The group of nondiabetic hypertensive subjects with diastolic pressure<=80mmHg had a cardiovascular mortality ratio of 4.1/1000 patients/year, 35.5% higher than the group with diastolic pressure <=90mmHg (cardiovascular mortality ratio, 3.1/1000 patients/year). In contrast, diabetic patients allocated to the diastolic pressure objective group of <=80mmHg had a 66.7% reduction in cardiovascular mortality (3.7/1000 patients/year) when compared with the diastolic pressure group of <=90mmHg (cardiovascular mortality ratio, 11.1/1000 patients/year). CONCLUSION: The results indicate that in hypertensive diabetic patients reduction in diastolic blood pressure to levels <=80mmHg decreases the risk of fatal cardiovascular events. It remains necessary to define the level of diastolic blood pressure <=90mmHg at which maximal reduction in cardiovascular mortality is obtained for nondiabetics.

Assessment of splanchnic perfusion with gastric tonometry in the immediate postoperative period of cardiac surgery in children

OBJECTIVE - A prospective, nonrandomized clinical study to assess splanchnic perfusion based on intramucosal pH in the postoperative period of cardiac surgery and to check the evolution of patients during hospitalization. METHODS - We studied 10 children, during the immediate postoperative period after elective cardiac surgery. Sequential intramucosal pH measurements were taken, without dobutamine (T0) and with 5mcg/kg/min (T1) and 10 (T2) mcg/kg/min. In the pediatric intensive care unit, intramucosal pH measurements were made on admission and 4, 8, 12, and 24 hours thereafter. RESULTS - The patients had an increase in intramucosal pH values with dobutamine 10mcg/kg/min [7.19± 0.09 (T0), 7.16±0.13(T1), and 7.32±0.16(T2)], (p=0.103). During the hospitalization period, the intramucosal pH values were the following: 7.20±0.13 (upon admission), 7.27±0.16 (after 4 hours), 7.26±0.07 (after 8 hours), 7.32±0.12 (after 12 hours), and 7.38±0.08 (after 24 hours), (p=0.045). No deaths occurred, and none of the patients developed multiple organ and systems dysfunction. CONCLUSION - An increase in and normalization of intramucosal pH was observed after dobutamine use. Measurement of intramucosal pH is a type of monitoring that is easy to perform and free of complications in children during the postoperative period of cardiac surgery.

Effect of Propafenone on the Contractile Activity of Latissimus Dorsi Muscle Isolated in an Organ Chamber: Experimental Study in Rats

OBJECTIVE: To study the effect of propafenone on the contractile function of latissimus dorsi muscle isolated from rats in an organ chamber. METHODS: We studied 20 latissimus dorsi muscles of Wistar rats and divided them into 2 groups: group I (n=10), or control group - we studied the feasibility of muscle contractility; group II (n=10), in which the contralateral muscles were grouped - we analyzed the effect of propafenone on muscle contractility. After building a muscle ring, 8 periods of sequential 2-minute baths were performed, with intervals of preprogrammed electrical stimulation using a pacemaker of 50 stimuli/min. In group II, propafenone, at the concentration of 9.8 µg/mL, was added to the bath in period 2 and withdrawn in period 4. RESULTS: In group I, no significant depression in muscle contraction occurred up to period 5 (p>0.05). In group II, a significant depression occurred in all periods, except between the last 2 periods (p<0.05). Comparing groups I and II only in period 1, which was a standard period for both groups, we found no significant difference (p>0.05). CONCLUSION: Propafenone had a depressing effect on the contractile function of latissimus dorsi muscle isolated from rats and studied in an organ chamber.

Epidemiological study of congenital heart defects in children and adolescents: analysis of 4,538 cases

OBJECTIVE: To analyze the frequency and prevalence of congenital heart defects in a tertiary care center for children with heart diseases. METHODS: We carried out an epidemiological assessment of the first medical visit of 4,538 children in a pediatric hospital from January 1995 to December 1997. All patients with congenital heart defects had their diagnoses confirmed at least on echocardiography. The frequency and prevalence of the anomalies were computed according to the classification of sequential analysis. Age, weight, and sex were compared between the groups of healthy individuals and those with congenital heart defects after distribution according to the age group. RESULTS: Of all the children assessed, 2,017 (44.4%) were diagnosed with congenital heart disease, 201 (4.4%) with acquired heart disease, 52 (1.2%) with arrhythmias, and 2,268 (50%) were healthy children. Congenital heart diseases predominated in neonates and infants, corresponding to 71.5% of the cases. Weight and age were significantly lower in children with congenital heart defects. Ventricular septal defect was the most frequent acyanotic anomaly, and tetralogy of Fallot was the most frequent cyanotic anomaly. CONCLUSION: Children with congenital heart defects are mainly referred during the neonatal period and infancy with impairment in gaining weight. Ventricular septal defect is the most frequent heart defect.

A contribution to the study of acute schistosomiasis (an experimental trial)

In an attempt to establish an experimental model of acute schistosomiasis, sequential histological changes were investigated in the skin, lung, liver and spleen of mice infected with 30 or 100 cercariae of Schistosoma mansoni according to four sets of experiments: single infection, repeated infections, unisexual infection and infection in mice born from infected mothers. Animals were killed every other day from exposure up to 50 days after infection. Only mild, isolated, focal inflammatory changes were found before the appearance of mature eggs in the liver, even when repeated infections were made. Severe changes of reactive hepatitis and splenitis appeared suddenly when the first mature eggs were deposited, around the 37th to 42nd day after infection. The mature eggs induced lytic and coagulative necrosis of hepatocytes around them which was soon followed by dense infiltration of eosinophils. So, mature egg-induced lesions appeared as the major factors in the pathogenesis of acute schistosomiasis in mice. Mice born from infected mothers were apparently able to rapidly modulate the egg-lesions, forming early fibrotic granulomas. The murine model of acute schistosomiasis appeared adequate for the study of pathology and pathogenesis of acute schistosomiasis.

Treatment of acute experimental schistosomiasis

A model of acute schistosomiasis of the mouse was used to observe whether curative treatment would be followed by an enhancement of the hepatic and splenic lesions, as a consequence of the massive destruction of worms and eggs within the portal system. Mice infected with 50 cercariae of Schistosoma mansoni were treated with both oxamniquine and praziquantel on the 50th day of infection and submitted to a sequential histologic examination from the 2nd to the 45th day after treatment. Although severe focal lesions due to dead and disintegranting worms were present in the livers of the treated animals, no aggravation of the general changes (reative hepatitis and splenitis, or periovular granulomas) was seen in comparison with a control non-treated group. Of 50 animals treated during the acute phase of schistosomiasis only one died espontaneously, while 16 ou of 30 infected controls died before the end of the experiment. The present investigation indicates that curative treatment during the acute phase of schistosomiasis does not enhance previous lesions at first and results in progressive disappearance of the lesions starting six days following chemotherapy.

The role of egg antigens, cytokines in granuloma formation in murine schistosomiasis mansoni

The induction of granuloma formation by soluble egg antigens (SEA) of Schistosoma mansoni is accompanied by T cell-mediated lymphokine production that regulates the intensity of the response. In the present study we have examined the ability of SDS-PAGE fractioned SEA proteins to elicit granulomas and lymphokine production in infected and egg-immunized mice. At the acute stage of infection SEA fractions (<21, 25-30, 32-38, 60-66, 70-90, 93-125, and > 200 kD) that elicited pulmonary granulomas also elicited IL-2, IL-4 lymphokine production. At the chronic stage a diminished number of fractions (60-66, 70-90, 93-125, and > 200 kD) were able to elicit granulomas with an overall decrease in IL-2, IL-4 production. Granulomas were elicited by larval-egg crossreactive and egg-specific fractions at both the acute and chronic stage of the infection. Examination of lymphokine production from egg-immunized mice demonstrated that as early as 4 days IL-2 was produced by spleen cells stimulated with <21, 32-38, 40-46, 93-125, and >200 kD fractions. By 16 days, IL-2production was envoked by 8 of 9 fractions. IL-4 production at 4 days in response to all fractions was minimal while at 16 days IL-4 was elicited with the < 21, 25-30, 50-56, 93-125, and > 200 kD fractions. The present study reveals differences in the range of SEA fractions able to elicit granulomas and IL-2, IL-4 production between acute and chronic stages of infection. Additionally, this study demonstrates sequential (IL-2 followed by IL-4) lymphokine production during the primary egg antigen response.

Recent advances in immunity to human schistosomiasis

For many years the epidemiological significance of immunity in human schistosomiasis has been the subject of inconclusive debate. Recently, the results of studies from Brazil and Kenya, on Shistosoma mansoni and from Zimbabwe and The Gambia on S. haematobium have confirmed the importance of protective immunity. In communities in endemic areas the development of immunity to infection only occurs after many years of exposure. In part this due to the slow development of antibodies wich are protective but also to the earlier development of antibody isotypes which lack protective capacity and wich are capable of interfering with the functioning of protective antibodies. Protective antibodies appear to be of the IgE class but some IgG subclasses may be also be important. Initially, blocking antibodies were thought to be predominantly IgM and IgG2 but IgG4 also seems to posses blocking activity. The early production of blocking antibodies and late production of protective antibodies may be indicative of cytokine induced immunoglobulin class swiching caused by the sequential involvment of different lymphokines.

A modified assay for measuring thymocyte co-stimulatory activity

The observation that murine thymocytes increase their proliferation to interleukin 1 (IL-1) in the presence of phytohemagglutinin (PHA) when pre-incubated with interleukin 2 (IL-2) allowed the introduction of a modified assay for the measurement of IL-1 or the search of thymocyte-inducing proliferative activities in biological samples. Pre-incubation of thymocytes for 24 hr with 50 u/ml IL-2, followed by washings, elicited their maximal response to IL-1 in the usual lymphocyte activating factor (LAF) assay. This suggests that sequential events lead to thymocyte activation. The responsiveness is three to five fold greater than, and the total time of assay is the same as that of the LAF assay. Interestingly, pre-incubation with IL-2 renders thymocytes more sensitive than responsive to crude monocyte conditioned media. The use of the MTT colorimetric method for the assessment of thymocyte proliferation, and of the lectin jacalin as a co-mitogen are suggested as alternatives to be used in co-stimulatory assays.

An Experimental Approach to the Pathogenesis of "Pipestem" Fibrosis (Symmers' Fibrosis of the Liver)

Pathogenesis of schistosomal hepatic fibrosis ("pipestem" fibrosis of the liver) was investigated by means of the murine model. Although worm load appears as the main pathogenetic factor, alone it is not sufficient to produce that characteristic lesion. By comparing the findings in animals with heavy and prolonged Schistosoma mansoni infection, which developed or not" pipestem" fibrosis, it was observed that the lesion was more frequent in intact animals than in the splenectomized one. However, the size of the spleen, the number of recovered worms, the number of eggs per gram of liver tissue, the level of serum idiotype and anti-idiotype antibodies, the size and volume of periovular granulomas formed in the liver, all that failed to show statistically significant differences between the two groups. After analysing all these data, other factors, that apparently have been hitherto negleted, rested to explain the findings. Among them, the timing and sequence of the egg-induced intrahepatic vascular changes seemed crucial. The sequential development of intrahepatic portal vein obstruction, followed by the opening of periportal collateral veins and the continous arrival of schistosome eggs going to be lodged into the latter, appeared as essential steps in the pathogenesis of "pipestem" fibrosis

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-alpha 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.

Histopathologic features associated with susceptibility and resistance of biomphalaria snails to infection with Schistosoma mansoni

Resistance and susceptibility of Biomphalaria snails to Schistosoma mansoni sporocysts occur in different degrees. Histopathology reflects these diferences. In a state of tolerance numerous sporocysts in different stages of differentiation are seen in the absence of host tissue reaction. However extensive diffuse and focal proliferation of amebocytes with sequestration and destruction of many parasitic structures appear in resistant snails. Some snails are totally resistant and when exposed to infecting miracidia may never eliminate cercarie. Sequential histopathological examination has revealed that in such cases the infected miracidia are destroyed a few minutes to 24 hr after penetration in the snail. However, B. glabrata that were exposed to S. mansoni miracidia and three moths later failed to shed cercariae, exhibited focal and diffuse proliferation of amebocytes in many organs in the absence of pasitic structures. These lesions were similar to those observed in resistant snails that were still eliminating a few cercariae, with the difference that no recognizable sporocystic structures or remmants were present. Histological investigation carried out in similarly resistant B. tenagophila and B. straminea presented essentially normal histologic structures. Only occasionally a few focal proliferative (granulomatous) amebocytic reactions were seen in ovotestis and in the tubular portion of the kidney. Probably, there are two types of reactions to miracidium presented by totally resistant snails: one would implicate the immediate destruction of the miracidium leaving no traces in the tissues; the other involving late reactions that seem to completely destroy invading sporocysts and leave histological changes.