Essential oil from Brazilian Red Propolis exhibits anthelmintic activity against larvae of Toxocara cati.

Toxocara spp. are responsible for causing toxocariasis, a zoonotic disease of global importance, which is difficult to treat as the available drugs have moderate efficacy in the clinical resolution of the disease. A promising alternative to the existing drugs is Propolis, which is known for having biological and pharmacological properties such as antiparasitic, antioxidant, and antitumor activities. In this study, we report the in vitro anthelmintic activity of essential oil from Brazilian Red Propolis (EOP) against larvae of Toxocara cati. Approximately 100 larvae per well were cultivated in microplates containing RPMI-1640 medium and incubated in the presence of EOP (18.75, 37.5, 75, 150, 300 and 600 µg/mL) to determine the Minimum Inhibitory Concentration (MIC) and IC50 (concentration required to inhibit 50% of the population) values. Then, T. cati larvae treated with the MIC of EOP were inoculated in mice to evaluate their progression in vivo. A concentration of 600 µg/mL of EOP showed 100% larvicidal activity after exposure for 48 h, while 300 µg/mL represented the IC50 and CC50. The anthelmintic activity of EOP was confirmed by the inability of the treated T. cati larvae to infect the mice. Our findings demonstrate the potential of EOP as an anthelmintic.

Stable expression of Mycobacterium bovis antigen 85B in auxotrophic M. bovis bacillus Calmette-Guérin.

BACKGROUND: Bovine tuberculosis (TB) is a zoonotic disease caused by Mycobacterium bovis, responsible for causing major losses in livestock. A cost effective alternative to control the disease could be herd vaccination. The bacillus Calmette-Guérin (BCG) vaccine has a limited efficacy against bovine TB, but can improved by over-expression of protective antigens. The M. bovis antigen 85B demonstrates ability to induce protective immune response against bovine TB in animal models. However, current systems for the construction of recombinant BCG expressing multiple copies of the gene result in strains of low genetic stability that rapidly lose the plasmid in vivo. Employing antibiotic resistance as selective markers, these systems also compromise vaccine safety. We previously reported the construction of a stable BCG expression system using auxotrophic complementation as a selectable marker. OBJECTIVES: The fundamental aim of this study was to construct strains of M. bovis BCG Pasteur and the auxotrophic M. bovis BCG ΔleuD expressing Ag85B and determine their stability in vivo. METHODS: Employing the auxotrophic system, we constructed rBCG strains that expressed M. bovis Ag85B and compared their stability with a conventional BCG strain in mice. Stability was measured in terms of bacterial growth on the selective medium and retention of antigen expression. FINDINGS: The auxotrophic complementation system was highly stable after 18 weeks, even during in vivo growth, as the selective pressure and expression of antigen were maintained comparing to the conventional vector. MAIN CONCLUSION: The Ag85B continuous expression within the host may generate a stronger and long-lasting immune response compared to conventional systems.

Stable expression of Mycobacterium bovis antigen 85B in auxotrophic M. bovis bacillus Calmette-Guérin

BACKGROUND Bovine tuberculosis (TB) is a zoonotic disease caused by Mycobacterium bovis, responsible for causing major losses in livestock. A cost effective alternative to control the disease could be herd vaccination. The bacillus Calmette-Guérin (BCG) vaccine has a limited efficacy against bovine TB, but can improved by over-expression of protective antigens. The M. bovis antigen 85B demonstrates ability to induce protective immune response against bovine TB in animal models. However, current systems for the construction of recombinant BCG expressing multiple copies of the gene result in strains of low genetic stability that rapidly lose the plasmid in vivo. Employing antibiotic resistance as selective markers, these systems also compromise vaccine safety. We previously reported the construction of a stable BCG expression system using auxotrophic complementation as a selectable marker. OBJECTIVES The fundamental aim of this study was to construct strains of M. bovis BCG Pasteur and the auxotrophic M. bovis BCG ΔleuD expressing Ag85B and determine their stability in vivo. METHODS Employing the auxotrophic system, we constructed rBCG strains that expressed M. bovis Ag85B and compared their stability with a conventional BCG strain in mice. Stability was measured in terms of bacterial growth on the selective medium and retention of antigen expression. FINDINGS The auxotrophic complementation system was highly stable after 18 weeks, even during in vivo growth, as the selective pressure and expression of antigen were maintained comparing to the conventional vector. MAIN CONCLUSION The Ag85B continuous expression within the host may generate a stronger and long-lasting immune response compared to conventional systems.

In silico identification of Corynebacterium pseudotuberculosis antigenic targets and application in immunodiagnosis.

Caseous lymphadenitis (CLA) is a disease caused by Corynebacterium pseudotuberculosis. It affects mainly small ruminants and causes significant economic losses worldwide. Because symptoms are not immediately noticeable, CLA clinical diagnosis is not effective. Numerous serological tests are being developed to detect the disease in asymptomatic animals, but currently available immunoassays have problems with sensitivity. Current ELISA formats use native bacterial antigens, and recombinant proteins could be useful for improving the immunoassay parameters. The C. pseudotuberculosis proteins CP0126a, CP0369 and CP1957 were identified from 2097 candidate proteins by mature epitope density (MED) analysis, expressed in Escherichia coli and evaluated in an indirect immunoenzymic system. The CP0126a, CP0369 and CP1957 ELISAs showed 77.5 %, 92.5 % and 92.5 % specificity and 95 %, 90 % and 85 % sensitivity, respectively. Receiver operating characteristic (ROC) curve analysis showed an area under the curve of 0.874, 0.951 and 0.881, respectively. The proteins identified in silico were recognized by antibodies in the sera from infected animals without being recognized in negative samples. The ELISA assay using the rCP0369 protein as antigen had the greatest specificity and sensitivity values, followed by rCP1957. This is an interesting strategy for seroepidemiological investigations in sheep flocks due to its significant specificity and sensitivity.

Vaccination with a BCG strain overexpressing Ag85B protects cattle against Mycobacterium bovis challenge.

Mycobacterium bovis is the causative agent of tuberculosis in cattle but also infects other animals, including humans. Previous studies in cattle have demonstrated that the protection induced by BCG is not complete. In order to improve the protection efficacy of BCG, in this study we overexpressed Ag85B in a BCG Pasteur strain, by using an expression system based on the use of an auxotrophic strain for the leucine amino acid, and complementation with leuD. We found that vaccination of cattle with BCG overexpressing Ag85B induced higher production of IL-17 and IL-4 mRNA upon purified protein derivative (PPDB) stimulation of peripheral blood mononuclear cells (PBMCs) than vaccination with BCG. Moreover, the IL-17 mRNA expression after vaccination negatively correlated with disease severity resulting from a subsequent challenge with M. bovis, suggesting that this cytokine is a potential biomarker of cattle protection against bovine tuberculosis. Importantly, vaccination with the recombinant BCG vaccine protected cattle better than the wild-type BCG Pasteur.