Brazilian avian metapneumovirus subtypes A and B: experimental infection of broilers and evaluation of vaccine efficacy

Avian metapneumovirus (aMPV) is a respiratory pathogen associated with the swollen head syndrome (SHS) in chickens. In Brazil, live aMPV vaccines are currently used, but subtypes A and, mainly subtype B (aMPV/A and aMPV/B) are still circulating. This study was conducted to characterize two Brazilian aMPV isolates (A and B subtypes) of chicken origin. A challenge trial to explore the replication ability of the Brazilian subtypes A and B in chickens was performed. Subsequently, virological protection provided from an aMPV/B vaccine against the same isolates was analyzed. Upon challenge experiment, it was shown by virus isolation and real time PCR that aMPV/B could be detected longer and in higher amounts than aMPV/A. For the protection study, 18 one-day-old chicks were vaccinated and challenged at 21 days of age. Using virus isolation and real time PCR, no aMPV/A was detected in the vaccinated chickens, whereas one vaccinated chicken challenged with the aMPV/B isolate was positive. The results showed that aMPV/B vaccine provided a complete heterologous virological protection, although homologous protection was not complete in one chicken. Although only one aMPV/B positive chicken was detected after homologous vaccination, replication in vaccinated animals might allow the emergence of escape mutants.

In silico phylogenetic and virulence gene profile analyses of avian pathogenic Escherichia coli genome sequences

Avian pathogenic Escherichia coli (APEC) infections are responsible for significant losses in the poultry industry worldwide. A zoonotic risk has been attributed to APEC strains because they present similarities to extraintestinal pathogenic E. coli (ExPEC) associated with illness in humans, mainly urinary tract infections and neonatal meningitis. Here, we present in silico analyses with pathogenic E. coli genome sequences, including recently available APEC genomes. The phylogenetic tree, based on multi-locus sequence typing (MLST) of seven housekeeping genes, revealed high diversity in the allelic composition. Nevertheless, despite this diversity, the phylogenetic tree was able to cluster the different pathotypes together. An in silico virulence gene profile was also determined for each of these strains, through the presence or absence of 83 well-known virulence genes/traits described in pathogenic E. coli strains. The MLST phylogeny and the virulence gene profiles demonstrated a certain genetic similarity between Brazilian APEC strains, APEC isolated in the United States, UPEC (uropathogenic E. coli) and diarrheagenic strains isolated from humans. This correlation corroborates and reinforces the zoonotic potential hypothesis proposed to APEC.

Analysis of hematologic and serum chemistry values of Spheniscus magellanicus with molecular detection of avian malarial parasites (Plasmodium spp.)

Magellanic penguins (Spheniscus magellanicus) routinely migrate from their breeding colonies to Southern Brazil often contracting diseases during this migration, notably avian malaria, which has been already reported in Brazil and throughout the world. Detection of Plasmodium spp. in blood smears is the routine diagnostic method of avian malaria, however it has a low sensitivity rate when compared to molecular methods. Considering the negative impact of avian malaria on penguins, the aim of this study was to detect the presence of Plasmodium spp. in Magellanic penguins using Polymerase Chain Reaction (PCR) and by verifying clinical, hematological, and biochemical alterations in blood samples as well as to verify the likely prognosis in response to infection. Blood samples were obtained from 75 penguins to determine packed cell volume (PCV), red blood cell (RBC) and white blood cell (WBC) counts, mean corpuscular volume (MCV), uric acid, total protein, albumin, globulin and aspartate aminotransferase (AST) activity levels. Whole blood samples were used for PCR assays. Plasmodium spp. was detected in 32.0% of the specimens using PCR and in 29.3% using microscopic analyses. Anorexia, diarrhea and neurological disorders were more frequent in penguins with malaria and a significant weight difference between infected and non-infected penguins was detected. PCV and MCV rates showed no significant difference. RBC and WBC counts were lower in animals with avian malaria and leukopenia was present in some penguins. Basophil and lymphocyte counts were lower in infected penguins along with high monocyte counts. There was no significant difference in AST activities between infected and non-infected animals. There was a significant increase in uric acid values, however a decrease in albumin values was observed in infected penguins. Based on this study, we concluded that Plasmodium spp. occurs in Magellanic penguins of rehabilitation centers in Southeastern Brazil, compromising the weight of infected animals with clinical alterations appearing in severe cases of this disease. It was also noted that, although the hematological abnormalities presented by these animals may not have been conclusive, leukopenia, monocytosis and the decrease of basophils and lymphocytes revealed an unfavorable prognosis, and Plasmodium spp. infections may progress with elevated uric acid concentration and low albumin levels.

Increased expression of Interleukin-6 related to nephritis in chickens challenged with an Avian infectious bronchitis virus variant

A Brazilian field isolate (IBV/Brazil/PR05) of avian infectious bronchitis virus (IBV), associated with development of nephritis in chickens, was previously genotyped as IBV variant after S1 gene sequencing. The aim of this study was to evaluate the levels of IL-6 in kidneys and trachea of birds vaccinated and challenged with IBV/Brazil/PR05 strain, correlating these results with scores of microscopic lesions, specific IBV antigen detection and viral load. The up-regulation of IL-6 and the increased levels of viral load on renal and tracheal samples were significantly correlated with scores of microscopic lesions. Reduced levels of viral load were detected in kidneys of birds previously vaccinated and challenged, compared to non-vaccinated challenged group, although markedly microscopic lesions were observed for both groups. The expression of IL-6, present both in the kidney and in the tracheas, was dependent on the load of the virus present in the tissue, and the development of lesions was related with IL-6 present in the tissues. These data suggest that variant IBV/Brazil/PR05 can induce the expression of proinflammatory cytokines in a manner correlated with viral load and increased IL-6 is involved in the tissue with the influx of inflammatory cells and subsequent nephritis. This may contribute with a model to the development of immunosuppressive agents of IL-6 to prevent acute inflammatory processes against infection with IBV and perhaps other coronaviruses, as well as contribute to the understanding of the immunopathogenesis of IBV nephropatogenic strains.

IFN-g in human Chagas' disease: protection or pathology?

An apparently paradoxical role for IFN-g in human Chagas' disease was observed when studying the pattern of cytokine production by peripheral blood mononuclear cells (PBMC) obtained from two groups of chagasic patients after specific stimulation with Trypanosoma cruzi-derived antigens. The groups studied were 1) patients treated with benznidazole during the acute phase of Trypanosoma cruzi infection and 2) chronically infected untreated patients. In the treated group, higher levels of IFN-g were produced by PBMC from individuals cured after treatment when compared to non-cured patients. In contrast, in the chronically infected group (not treated) higher levels of IFN-g were produced by PBMC from cardiac patients in comparison with asymptomatic (indeterminate) patients. This apparently paradoxical role for IFN-g in human Chagas' disease is discussed in terms of the possibility of a temporal difference in IFN-g production during the initial stages of the infection (acute phase) in the presence or absence of chemotherapy. The maintenance of an immune response with high levels of IFN-g production during the chronic phase of the infection may favor cure or influence the development of the cardiac form of the disease

Cytokine profile and pathology in human leishmaniasis

The clinical spectrum of leishmaniasis and control of the infection are influenced by the parasite-host relationship. The role of cellular immune responses of the Th1 type in the protection against disease in experimental and human leishmaniasis is well established. In humans, production of IFN-g is associated with the control of infection in children infected by Leishmania chagasi. In visceral leishmaniasis, an impairment in IFN-g production and high IL-4 and IL-10 levels (Th2 cytokines) are observed in antigen-stimulated peripheral blood mononuclear cells (PBMC). Moreover, IL-12 restores IFN-g production and enhances the cytotoxic response. IL-10 is the cytokine involved in down-regulation of IFN-g production, since anti-IL-10 monoclonal antibody (mAb) restores in vitro IFN-g production and lymphoproliferative responses, and IL-10 abrogates the effect of IL-12. In cutaneous and mucosal leishmaniasis, high levels of IFN-g are found in L. amazonensis-stimulated PBMC. However, low or absent IFN-g levels were observed in antigen-stimulated PBMC from 50% of subjects with less than 60 days of disease (24 ± 26 pg/ml). This response was restored by IL-12 (308 ± 342 pg/ml) and anti-IL-10 mAb (380 ± 245 pg/ml) (P<0.05). Later during the disease, high levels of IFN-g and TNF-a are produced both in cutaneous and mucosal leishmaniasis. After treatment there is a decrease in TNF-a levels (366 ± 224 pg/ml before treatment vs 142 ± 107 pg/ml after treatment, P = 0.02). Although production of IFN-g and TNF-a might be involved in the control of parasite multiplication in the early phases of Leishmania infection, these cytokines might also be involved in the tissue damage seen in tegumentary leishmaniasis

Cytokines as determinants of resistance and pathology in human Schistosoma mansoni infection

The role of different cytokines in the peripheral blood mononuclear cell (PBMC) proliferative response and in in vitro granuloma formation was evaluated in a cross-sectional study with patients with the different clinical forms and phases of Schistosoma mansoni infection, as well as a group of individuals "naturally" resistant to infection named normal endemic (NE). The blockage of IL-4 and IL-5 using anti-IL-4 and anti-IL-5 antibodies significantly reduced the PBMC proliferative response to soluble egg (SEA) and adult worm (SWAP) antigens in acute (ACT), chronic intestinal (INT) and hepatosplenic (HS) patients. Similar results were obtained in the in vitro granuloma formation. Blockage of IL-10 had no significant effect on either assay using PBMC from ACT or HS. In contrast, the addition of anti-IL-10 antibodies to PBMC cultures from INT patients significantly increased the proliferative response to SEA and SWAP as well as the in vitro granuloma formation. Interestingly, association of anti-IL-4 and anti-IL-10 antibodies did not increase the PBMC proliferative response of these patients, suggesting that IL-10 may act by modulating IL-4 and IL-5 secretion. Addition of recombinant IL-10 decreased the proliferative response to undetectable levels when PBMC from patients with the different clinical forms were used. Analysis of IFN-g in the supernatants showed that PBMC from INT patients secreted low levels of IFN-g upon antigenic stimulation. In contrast, PBMC from NE secreted high levels of IFN-g. These data suggest that IL-10 is an important cytokine in regulating the immune response and possibly controlling morbidity in human schistosomiasis mansoni, and that the production of IFN-g may be associated with resistance to infection.

The pharmacological effect of Bothrops neuwiedii pauloensis (jararaca-pintada) snake venom on avian neuromuscular transmission

The neuromuscular effects of Bothrops neuwiedii pauloensis (jararaca-pintada) venom were studied on isolated chick biventer cervicis nerve-muscle preparations. Venom concentrations of 5-50 µg/ml produced an initial inhibition and a secondary increase of indirectly evoked twitches followed by a progressive concentration-dependent and irreversible neuromuscular blockade. At venom concentrations of 1-20 µg/ml, the responses to 13.4 mM KCl were inhibited whereas those to 110 µM acetylcholine alone and cumulative concentrations of 1 µM to 10 mM were unaffected. At venom concentrations higher than 50 µg/ml, there was pronounced muscle contracture with inhibition of the responses to acetylcholine, KCl and direct stimulation. At 20-24ºC, the venom (50 µg/ml) produced only partial neuromuscular blockade (30.7 ± 8.0%, N = 3) after 120 min and the initial inhibition and the secondary increase of the twitch responses caused by the venom were prolonged and pronounced and the response to KCl was unchanged. These results indicate that B.n. pauloensis venom is neurotoxic, acting primarily at presynaptic sites, and that enzyme activity may be involved in this pharmacological action.

Cat Scratch Disease in kidney transplant receptors: is it a rare or underdiagnosed pathology?

Cat Scratch Disease (CSD) is an infectious disorder which appears after cat scratching particularly in children and adolescents. Bartonella henselae is the etiologic agent more frequently involved. There are only a few recent reports demonstrating the disease after transplantation, although the illness is not infrequent in immunologically competent people. Indeed CSD in transplant receptors has only been recently emphasized in the literature and it was concluded that fever and lymphadenopathy in patients who had been exposed to cats should prompt clinicians to maintain a suspicion for the infection. In this report CSD infecting a renal transplanted adolescent complaining of headache, blurred vision and fever, presenting a cat scratching lesion in the right arm, with a bilateral painful cervical lymphadenopathy was related. He also presented indirect immunofluorescency identifying that the two subtype's titles of Bartonella-henselae and quintana- were elevated. Treatment with doxicicline e rifampicin was introduced and the patient became asymptomatic in about 3 weeks.