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.