Experimental human infection with the dog hookworm, Ancylostoma caninum

Objective: To investigate possible routes for human infection by the dog hookworm (Ancylostoma caninum). Design, setting and participant. Relatively small numbers of infective larvae were administered orally and percutaneously to an informed healthy volunteer (J K L) under medical supervision, at intervals between May 1998 and May 1999. Main outcome measures: Symptoms; weekly blood eosinophil counts; faecal microscopy. Results: A marked blood eosinophilia followed a single oral exposure to 100 infective larvae, while faecal examination remained negative. Eosinophil counts then declined gradually, although a rapid, spontaneous rise several months later, at the beginning of spring, possibly indicated reactivation of dormant larvae. Blood eosinophil numbers did not rise significantly after percutaneous infection with 200 larvae. A subsequent, smaller, oral inoculum of 20 larvae provoked an eosinophil response similar to that of the first experiment. Conclusions: Our findings suggest that, following ingestion, some infective larvae of A. caninum develop directly into adult worms in the human gut (as they do in dogs). While the percutaneous route might be the most common means of human exposure to canine hookworm larvae, leading generally to subclinical infection, oral infection may be more likely to provoke symptomatic eosinophilic enteritis.

STUDIES ON THE USE OF A FORMIC-ACID PROPIONIC-ACID MIXTURE (BIO-ADD(TM)) TO CONTROL EXPERIMENTAL SALMONELLA INFECTION IN BROILER-CHICKENS

Experiments were carried out on the antibacterial effects of a commercial formic acid-propionic acid mixture (Bio-add(TM)) against different Salmonella serptj pes. The preparation exerted a strong antibacterial effect on S. typhimurium strain F98 in artificially contaminated feed. After 28 days storage, the bactericidal effect was still considerable. When chickens were reared on feed that had been treated with Bio-add(TM) and artificially contaminated with different serotypes, S. enteritidis, S. typhimurium and S. agona were not isolated from the caecal contents, but S. infantis was. No organisms of this strain were isolated when a lower feed-contamination rate of bacteria was used.

Hematological alterations during experimental canine infection by Trypanosoma cruzi

To confirm that Beagle dogs are a good experimental model for Chagas disease, we evaluated hematological alterations during the acute and chronic phases in Beagle dogs infected with the Y, Berenice-78 (Be-78) and ABC strains of Trypanosoma cruzi, correlating clinical signs with the parasitemia curve. We demonstrate that the acute phase of infection was marked by lethargy and loss of appetite. Simultaneously, we observed anemia, leukocytosis and lymphocytosis. Also,we describe hematological alterations and clinical signs that were positively correlated with the parasitemia during the experimental infection with the three strains of T cruzi, and demonstrate that experimental infection of Beagle is a trustworthy model for Chagas disease.

Comparison of the diagnostic significance of clinical, radiographic and ultrasonographic results after an experimental aerosol infection of pigs with Actinobacillus pleuropneumoniae

Scoring schemes for clinical, ultrasonographic and radiographic findings in pigs were developed based upon a standardized animal model for Actinobacillus pleuropneumoniae infection.The results of these methods were compared to each other as well as with the corresponding pathomorphological findings during necropsy. Altogether 69 pigs of different breeding lines (Hampshire, Pietrain and German Landrace were examined. Positive correlations were found between the results of all three methods as well as with the necropsy scores (p <0.0001). Different pathomorphological findings were detected either by radiographic or by ultrasonographic examination dependent upon the type of lung tissue alterations: Alterations of the pleura as well as sequestration of lung tissue on the lung surface could be clearly identified during the ultrasonographic examination while deep tissue alterations with no contact to the lung surface could be detected reliably by radiographic examination. Both methods complement each other, and the application of a combined ultrasonographic and radiographic examination of the thorax allows a comprehensive inspection of the lung condition. Particularly during the acute phase of the disease the extent of lung tissue damage can be estimated more precisely than by clinical examination alone.

Natural and experimental oral infection of nonhuman primates by bovine spongiform encephalopathy agents

Experimental lemurs either were infected orally with the agent of bovine spongiform encephalopathy (BSE) or were maintained as uninfected control animals. Immunohistochemical examination for proteinase-resistant protein (prion protein or PrP) was performed on tissues from two infected but still asymptomatic lemurs, killed 5 months after infection, and from three uninfected control lemurs. Control tissues showed no staining, whereas PrP was detected in the infected animals in tonsil, gastrointestinal tract and associated lymphatic tissues, and spleen. In addition, PrP was detected in ventral and dorsal roots of the cervical spinal cord, and within the spinal cord PrP could be traced in nerve tracts as far as the cerebral cortex. Similar patterns of PrP immunoreactivity were seen in two symptomatic and 18 apparently healthy lemurs in three different French primate centers, all of which had been fed diets supplemented with a beef protein product manufactured by a British company that has since ceased to include beef in its veterinary nutritional products. This study of BSE-infected lemurs early in their incubation period extends previous pathogenesis studies of the distribution of infectivity and PrP in natural and experimental scrapie. The similarity of neuropathology and PrP immunostaining patterns in experimentally infected animals to those observed in both symptomatic and asymptomatic animals in primate centers suggests that BSE contamination of zoo animals may have been more widespread than is generally appreciated.

Oral transmission of Chagas disease: importance of Trypanosoma cruzi biodeme in the intragastric experimental infection

Oral transmission of Trypanosoma cruzi has been suspected when epidemic episodes of acute infection were observed in areas devoid of domiciled insect vectors. Considering that the distribution of T. cruzi biodemes differs in sylvatic and domestic cycles, results of studies on biodemes can be of interest regarding oral transmission. The infectivity of T. cruzi strains of different biodemes was tested in mice subjected to infection by the digestive route (gavage). Swiss mice were infected either with the Peruvian strain (Biodeme Type I, Z2b) or the Colombian strain (Biodeme Type III, Z1, or T. cruzi I); for control, intraperitoneal inoculation was performed in a group of mice. The Colombian strain revealed a similar high infectivity and pathogenicity when either route of infection was used. However, the Peruvian strain showed contrasting levels of infectivity and pathogenicity, being high by intraperitoneal inoculation and low when the gastric route was used. The higher infectivity of the Colombian strain (Biodeme Type III) by gastric inoculation is in keeping with its role in the epidemic episodes of acute Chagas disease registered in the literature, since strains belonging to Biodeme III are most often found in sylvatic hosts.

Experimental infection of Rio Mamore hantavirus in Sigmodontinae rodents

This study shows an experimental spillover infection of Sigmodontinae rodents with Rio Mamore hantavirus (RIOMV). Necromys lasiurus and Akodon sp were infected with 103 RNA copies of RIOMV by intraperitoneal administration. The viral genome was detected in heart, lung, and kidney tissues 18 days after infection (ai), and viral excretion in urine and faeces began at four and six ai, respectively. These results reveal that urine and faeces of infected rodents contain the virus for at least 18 days. It is possible that inhaled aerosols of these excreta could transmit hantavirus to humans and other animals.

Experimental infection of Rio Mamore hantavirus in Sigmodontinae rodents

This study shows an experimental spillover infection of Sigmodontinae rodents with Rio Mamore hantavirus (RIOMV). Necromys lasiurus and Akodon sp were infected with 103 RNA copies of RIOMV by intraperitoneal administration. The viral genome was detected in heart, lung, and kidney tissues 18 days after infection (ai), and viral excretion in urine and faeces began at four and six ai, respectively. These results reveal that urine and faeces of infected rodents contain the virus for at least 18 days. It is possible that inhaled aerosols of these excreta could transmit hantavirus to humans and other animals.

Essential role of platelet-activating factor receptor in the pathogenesis of Dengue virus infection

Severe dengue infection in humans causes a disease characterized by thrombocytopenia, increased levels of cytokines, increased vascular permeability, hemorrhage, and shock. Treatment is supportive. Activation of platelet-activating factor (PAF) receptor (PAFR) on endothelial cells and leukocytes induces increase in vascular permeability, hypotension, and production of cytokines. We hypothesized that activation of PAFR could account for the major systemic manifestations of dengue infection. Inoculation of adult mice with an adapted strain of Dengue virus caused a systemic disease, with several features of the infection in humans. In PAFR(-/-) mice, there was decreased thrombocytopenia, hemoconcentration, decreased systemic levels of cytokines, and delay of lethality, when compared with WT infected mice. Treatment with UK-74,505, an orally active PAFR antagonist, prevented the above-mentioned manifestations, as well as hypotension and increased vascular permeability, and decreased lethality, even when started 5 days after virus inoculation. Similar results were obtained with a distinct PAFR antagonist, PCA-4246. Despite decreased disease manifestation, viral loads were similar (PAFR(-/-)) or lower (PAFR antagonist) than in WT mice. Thus, activation of PAFR plays a major role in the pathogenesis of experimental dengue infection, and its blockade prevents more severe disease manifestation after infection with no increase in systemic viral titers, suggesting that there is no interference in the ability of the murine host to deal with the infection. PAFR antagonists are disease-modifying agents in experimental dengue infection.

Natural Schistosoma mansoni infection in Nectomys squamipes: histopathological and morphometric analysis in comparison to experimentally infected N. squamipes and C3H/He mice

Histopathologic and morphometric (area, perimeter, major and minor diameters) analysis of hepatic granulomas isolated from twelve naturally infected Nectomys squamipes were compared to four experimentally infected ones and six C3H/He mice. Liver paraffin sections were stained for cells and extracellular matrix. Both groups of N. squamipes presented peculiar granulomas consisting predominantly of large macrophages, full of schistosome pigment, characterizing an exudative-macrophage granuloma type, smaller than the equivalent granuloma type in mouse. Naturally infected animals exhibited granulomas in different stages of development, including large number of involutional types. Morphometric analysis showed that all measurements were smaller in naturally infected animals than in other groups. The results demonstrated that both N. squamipes groups reproduced, with small variations, the hepatic granuloma aspects already described in cricetidium (Calomys callosus), showing a genetic tendency to set up strong macrophage responses and small granulomas. Unexpectedly, natural infection did not engender distinguished histopathological characteristics distinct from those derived from experimental single infection, showing changes predominantly secondary to the duration of infection. It appears that the variability of the inocula (and the number of infections?) interfere more with the quantity than with the quality of the pathological changes, denoting some morpho-functional determinism in the response to schistosomal infection dependent on the animal species.

Evidences of the cooperative role of the chemokines CCL3, CCL4 and CCL5 and its receptors CCR1+and CCR5+in RANKL+ cell migration throughout experimental periodontitis in mice

Periodontal disease (PD) is characterized by the inflammatory bone resorption in response to the bacterial challenge, in a host response that involves a series of chemokines supposed to control cell influx into periodontal tissues and determine disease outcome. In this study, we investigated the role of chemokines and its receptors in the immunoregulation of experimental PD in mice. Aggregatibacter actinomycetemcomitans-infected C57BI/6 (WT) mice developed an intense inflammatory reaction and severe alveolar bone resorption, associated with a high expression of CCL3 and the migration of CCR5+, CCR1+ and RANKL+ cells to periodontal tissues. However, CCL3KO-infected mice developed a similar disease phenotype than WT strain, characterized by the similar expression of cytokines (TNF-alpha, IFN-gamma and IL-10), osteoclastogenic factors (RANKL and OPG) and MMPs (MMP-1, MMP-2, MMP-3, TIMP-1 and TIMP-3), and similar patterns of CCR1+, CCR5+ and RANKL+ cell migration. The apparent lack of function for CCL3 is possible due the relative redundancy of chemokine system, since chemokines such as CCL4 and CCL5, which share the receptors CCR1 and CCR5 with CCL3, present a similar kinetics of expression than CCL3. Accordingly, CCL4 and CCL5 kinetics of expression after experimental periodontal infection remain unaltered regardless the presence/absence of CCL3. Conversely, the individual absence of CCR1 and CCR5 resulted in a decrease of leukocyte infiltration and alveolar bone loss. When CCR1 and CCR5 were simultaneously inhibited by met-RANTES treatment a significantly more effective attenuation of periodontitis progression was verified, associated with lower values of bone loss and decreased counts of leukocytes in periodontal tissues. Our results suggest that the absence of CCL3 does not affect the development of experimental PD in mice, probably due to the presence of homologous chemokines CCL4 and CCL5 that overcome the absence of this chemokine. In addition, our data demonstrate that the absence of chemokine receptors CCR1+ and CCR5+ attenuate of inflammatory bone resorption. Finally, our data shows data the simultaneous blockade of CCR1 and CCR5 with MetRANTEs presents a more pronounced effect in the arrest of disease progression, demonstrating the cooperative role of such receptors in the inflammatory bone resorption process throughout experimental PD. (C) 2009 Elsevier Inc. All rights reserved.

Influence of Th1/Th2 cytokines and nitric oxide in murine systemic infection induced by Sporothrix schenckii

In an attempt to elucidate the effects of Sporothrix schenckii infection on the immune response, our laboratory has developed a murine model of disseminated sporotrichosis. Helper T cells can be further subdivided into Th1 and Th2 phenotypes. The differentiation of two subsets of T lymphocytes is driven by IL-12 and IL-4 cytokines, respectively. Th1 cells produce IFN-gamma that activate macrophages and promote cell-mediated immunity. In addition, we found low levels of iNOS and NO production in the initial (1st and 2nd weeks) and final (9th and 10th weeks) periods of the infection, in contrast with the period of week 4 to 7 of elevated values. The determination of IFN-gamma and IL-12 are in agreement with NO/iNOS detection, showing the presence of cellular immune response throughout the infectious process. However, the production of IL-4 shows an increase in levels after the 5th and 6th weeks suggesting a participation of Th2 response in this period as well. Regarding these results, the study demonstrated that in experimental sporotrichosis infection the cellular immune response participated throughout the period analyzed as a nitric oxide dependent mechanism. In contrast, the presence of Th2 response began in the 5th week, suggesting the participation of humoral immune response in advanced stages of sporotrichosis.

Estudo clínico e imunopatológico da infecção experimental em cães com a amostra Jaboticabal de Ehrlichia canis na fase aguda e após o tratamento: expreção de citocinas no baço e sangue e de subpopulações de células imunes no baço

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The stereochemistry of the amino acid side chain influences the inflammatory potential of muramyl dipeptide in experimental meningitis

Intrathecal injections of 50 to 100 micro g of (N-acetylmuramyl-L-alanyl-D-isoglutamine) muramyl dipeptide (MDP)/rabbit dose-dependently triggered tumor necrosis factor alpha (TNF-alpha) secretion (12 to 40,000 pg/ml) preceding the influx of leukocytes in the subarachnoid space of rabbits. Intrathecal instillation of heat-killed unencapsulated R6 pneumococci produced a comparable leukocyte influx but only a minimal level of preceding TNF-alpha secretion. The stereochemistry of the first amino acid (L-alanine) of the MDP played a crucial role with regard to its inflammatory potential. Isomers harboring D-alanine in first position did not induce TNF-alpha secretion and influx of leukocytes. This stereospecificity of MDPs was also confirmed by measuring TNF-alpha release from human peripheral mononuclear blood cells stimulated in vitro. These data show that the inflammatory potential of MDPs depends on the stereochemistry of the first amino acid of the peptide side chain and suggest that intact pneumococci and MDPs induce inflammation by different pathways.