The present study had the objective of evaluating the pathogenic potential of the genetically related strains of
Streptococcus agalactiae no. 80427 (human origin) and no. 87159 (bovine origin), and ...comparing the results with two other strains isolated from bovine mastitis (no. 87244) and invasive human infection (no. 90356), with no genetic or epidemiologic relationship between them or with the first 2 isolates. Virulence genes
hylB (hyaluronidase) and
lmb (laminin-binding protein) were detected in the 4 strains, and genes
bac (beta protein) and
bca (alpha protein) were only detected in human strains. The protein profile obtained using SDS-PAGE did not indicate any differences between the 4 strains. No significant difference was detected between human and bovine strains in the assays of adherence to and invasion of 16HBe cells, as well as in the resistance assay for intracellular bacterial survival in macrophages. However, the strain 87159 exhibited a greater survival in the killing test with whole human blood and was more virulent in newborn mice than the 80427 strain. The strain 87244 was not virulent in mice. These data suggest that isolates of human and bovine origins may express similar virulence attributes, leading to a possible, however limited, dissemination.
The complement of sialyloligosaccharides present on the surface of human tracheal epithelium has been implicated as an important factor in the selection of hemagglutinin receptor specificity of human ...influenza A virus. Human strains of influenza A virus preferentially recognize host cell receptors bearing SA alpha 2,6Gal sequences, a sequence which is found on the surface of ciliated tracheal epithelium. A fluorescently-labelled H3 human virus strain bound avidly to the apical surface of human tracheal epithelium, while a fluorescently-labelled receptor variant strain, which preferentially binds SA alpha 2,3Gal sequences, showed little binding to the epithelial surface and localized primarily to intracellular mucin droplets. Extracts of human bronchial mucin, which is known to contain sialic acid primarily in the SA alpha 2,3Gal linkage, was a potent inhibitor of the binding of the receptor variant strain to trachea sections, while the binding of the parent strain was unaffected by the presence of mucin. Human bronchial mucin also inhibited the binding of the receptor variant strains, but not the parent virus strains, to human erythrocytes derivatized to contain SA alpha 2,6Gal sequences. These results suggest that a combination of selection pressures present in the respiratory tract environment have resulted in the evolution of a hemagglutinin receptor specificity in human influenza A virus strains which optimizes recognition of, binding to and infection of host cells.
Asymptomatic influenza virus infections in pigs are frequent and the lack of measures for controlling viral spread facilitates the circulation of different virus strains between pigs. The goal of ...this study was to demonstrate the circulation of influenza A virus strains among asymptomatic piglets in an abattoir in Brazil and discuss the potential public health impacts. Tracheal samples (n = 330) were collected from asymptomatic animals by a veterinarian that also performed visual lung tissue examinations. No slaughtered animals presented with any noticeable macroscopic signs of influenza infection following examination of lung tissues. Samples were then analysed by reverse transcription-polymerase chain reaction that resulted in the identification of 30 (9%) influenza A positive samples. The presence of asymptomatic pig infections suggested that these animals could facilitate virus dissemination and act as a source of infection for the herd, thereby enabling the emergence of influenza outbreaks associated with significant economic losses. Furthermore, the continuous exposure of the farm and abattoir workers to the virus increases the risk for interspecies transmission. Monitoring measures of swine influenza virus infections and vaccination and monitoring of employees for influenza infection should also be considered. In addition regulatory agencies should consider the public health ramifications regarding the potential zoonotic viral transmission between humans and pigs.
In this work, we examined the neuromuscular blockade caused by venoms from four South-American coralsnakes (Micrurus altirostris – MA, M. corallinus – MC, M. spixii – MS, and M. dumerilii carinicauda ...– MDC) and the ability of varespladib (VPL), a phospholipase A2 (PLA2) inhibitor, to attenuate this blockade. PLA2 activity was determined using a colorimetric assay and a fixed amount of venom (10 μg). Neurotoxicity was assayed using a single concentration of venom (10 μg/ml) in mouse phrenic nerve-diaphragm (PND) preparations mounted for myographic recordings and then subjected to histological analysis. All venoms showed PLA2 activity, with MS and MA venoms having the highest (15.53 ± 1.9 A425 nm/min) and lowest (0.23 ± 0.14 A425 nm/min) activities, respectively. VPL (292 and 438 μM) inhibited the PLA2 activity of all venoms, although that of MA venom was least affected. All venoms caused neuromuscular blockade, with MS and MDC venoms causing the fastest and slowest 100% blockade in 40 ± 3 min and 120 ± 6 min (n = 4), respectively; MA and MC produced complete blockade within 90–100 min. Preincubation of venoms with 292 μM VPL attenuated the blockade to varying degrees: the greatest inhibition was seen with MDC venom and blockade by MS venom was unaffected by this inhibitor. These results indicate that PLA2 has a variable contribution to coralsnake venom-induced neuromuscular blockade in vitro, with the insensitivity of MS venom to VPL suggesting that blockade by this venom is mediated predominantly by post-synaptically-active α-neurotoxins.
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•Phospholipase A2 does not influence Micrurus spixii venom-induced neuromuscular blockade•Varespladib slightly delays the neuromuscular blockade by Micrurus altirostris and Micrurus corallinus venoms•Micrurus dumerilii carinicauda venom-induced neuromuscular blockade is partially mediated by phospholipase A2•Phospholipase A2 variably affects the neurotoxicity by South American coralsnakes venoms in vitro
The expression of sialoglycoconjugates in Fonsecaea pedrosoi conidia, mycelia, and sclerotic cells was analyzed using influenza A and C virus strains, sialidase treatment, and lectin binding. ...Conidium and mycelium whole cells were recognized by Limax flavus (LFA), Maackia amurensis (MAA), and Sambucus nigra (SNA) lectins, denoting the presence of surface sialoglycoconjugates containing alpha 2,3- and alpha 2,6-sialylgalactosyl sequences. Sialidase-treated conidia reacted more intensively with peanut agglutinin (PNA), confirming the occurrence of sialyl-galactosyl linkages. Conidial cells agglutinated in the presence of influenza A and C virus strains, which confirmed the results obtained from lectin-binding experiments and revealed the presence of sialoglycoconjugates bearing 9-O-acetyl-N-acetylneuraminic acid (Neu5,9Ac(2)) surface structures. Western blotting analysis with peroxidase-labeled LFA demonstrated the occurrence of sialylglycoproteins in protein extracts from conidia and mycelia, with molecular masses corresponding to 56 and 40 kDa. An additional band of 77 kDa was detected in conidial extracts, suggesting an association between sialic acid expression and morphogenesis. Synthesis of sialic acids was correlated with sialidase expression, since both conidial and mycelial morphological stages presented secreted and cell-associated enzyme activity. Sialoglycoconjugates were not detected in F. pedrosoi sclerotic cells from in vitro and in vivo sources, which also do not express sialidase activity. The surface sialyl residues in F. pedrosoi are apparently involved in the fungal interaction with immune effector cells, since sialidase-treated conidia were less resistant to phagocytosis by human neutrophils from healthy individuals. These findings suggest that sialic acid expression in F. pedrosoi varies according to the morphological transition and may protect infecting propagules against immune destruction by host cells.
Vaccinal and wild strains of Newcastle Disease virus (NDV) were
analyzed for cell receptor binding and fusogenic biological properties
associated with their HN (hemagglutimn-neuraminidase) and F ...(fusion
protein) surface structures respectively. The evaluation of the
biological activities of HN and F was carried out respectively by
deterntination of hemagglutinating titers and hemolysis percentages,
using erythrocytes from various animal origins at different pH values.
Significant differences in hemag- glutination titersfor some strains of
NDV were detected, when interacting with goose, sheep, guineapig and
human "O" group erythrocytes at neutral pH. Diversity of hemolysis
percentages was observed between different NDV strains at acid pH.
These analysis were developed to evaluate particular aspects of the
actual influence of the receptor specificity and pH on the receptor
binding and fusogenic processes of Newcastle Disease viruses.
Because of the extensive genetic variability of the influenza viruses, new virus mutants arise worldwide. In the human population, some strains may become potentially epidemic after evading the ...immune response of the host. At present, molecular methods have made it possible to identify these variants. However, if a large number of samples need to be analyzed the identification of randomly mutated nucleotides cannot be achieved by sequencing analysis or restriction fragment length polymorphism (RFLP). In order to improve this process, a denaturing gradient gel electrophoresis (DGGE) protocol capable of discriminating between reference strains representative of different influenza seasons, some mutant strains, and five clinical isolates was standardized Ribonudeic acid (RNA) was isolated and submitted to a one-step RT-PCR that amplified the region codifying for the globular domain of the Haemagglutinin (HA) molecule. The amplicons were analyzed by electrophoresis in 6% polyacrylamide gel at 60
°C/150 V for 8 h, using a 31–41% urea–formamide gradient. This method was able to distinguish between closely related nucleotide sequences, confirming its suitability as screening methodology for the analysis of influenza virus epidemiology, by allowing a faster and more extensive evaluation of a large number of the variant strains detected in a specific region of the world.
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