ABSTRACT
Here we present the design of a conditionally lethal mutant of Salmonella enterica serovar Typhimurium (S. Typhimurium) which growth depends on tetracycline (Tet). Four mutants of S. Typhimurium, with Tet-conditional growth, were created by inserting the tetRA cassette. Three of the mutants presented a conditional-lethal phenotype in vitro. One mutant in the yabB gene remained conditional inside cells and did not persisted after 24 h in cell cultures. The capacity of S. Typhimurium yabB::tetRA to invade deep organs was investigated in intraperitoneally (IP) infected mice fed with or without chlortetracycline (CTet), a Tet analog with lower antibiotic activity. The yabB::tetRA mutant was undetectable in liver or spleen of animals under normal diet, while in mice under diet including CTet, yabB::tetRA invaded at a level comparable to the WT in mice under normal diet. Moreover, yabB::tetRA produced a strong humoral-immunoresponse after one IP immunization with 10(6) bacteria, measured as serum reactivity against S. Typhimurium whole cell extract. By contrast, oral immunization with 10(6) bacteria was weaker and variable on inducing antibodies. Consistently, IP infected mice were fully protected in a challenge with 10(4) oral S. Typhimurium, while protection was partial in orally immunized mice. Our data indicate that S. Typhimurium yabB::tetRA is a conditionally attenuated strain capable of inducing a protective response in mice in non-permissive conditions.
Subject(s)
Bacterial Vaccines/administration & dosage , Bacterial Vaccines/microbiology , Salmonella Infections/immunology , Salmonella Infections/prevention & control , Salmonella typhimurium/genetics , Salmonella typhimurium/immunology , Administration, Oral , Animals , Female , Mice , Mice, Inbred BALB C , Mutation/genetics , Salmonella Infections/microbiology , Salmonella typhimurium/classification , Species SpecificityABSTRACT
New vaccine design techniques have allowed the development of effective vaccine strains against Salmonella infections inwhich the risks of reversion to the wild type and virulence is null. The mutant strain Salmonella Gallinarum ΔcobSΔcbiA was previously shown to be avirulent in chickens. In this study, this strain was tested as a vaccine against Salmonella Gallinarum (SG) and S. Enteritidis (SE) infections, and its protection levels, safety and possible risks of reversion to virulence after vaccination of layers were evaluated. Birds were vaccinated at five days of age or at five and 25 days of age. At 45 days of age, brown and white layers were challenged with SG and SE wild strains, respectively. Two assays to test the possibility of reversion to virulence were performed. Five successive bacterial passages in brown layers were carried out in the first assay. In the second assay, brown layers received a ten-fold concentrated inoculum of the SGΔcobSΔcbiA strain and were evaluated for clinical signs and mortality. In both experiments, no birds that received the inoculation of the attenuated strain died. Additionally, the use of the mutant strain as a vaccine provided good protection levels against both challenge strains.(AU)
Subject(s)
Animals , Poultry Diseases/immunology , Salmonella Infections/prevention & control , Chickens/microbiology , Salmonella Vaccines/pharmacology , Salmonella/immunology , Virulence FactorsABSTRACT
New vaccine design techniques have allowed the development of effective vaccine strains against Salmonella infections inwhich the risks of reversion to the wild type and virulence is null. The mutant strain Salmonella Gallinarum cobScbiA was previously shown to be avirulent in chickens. In this study, this strain was tested as a vaccine against Salmonella Gallinarum (SG) and S. Enteritidis (SE) infections, and its protection levels, safety and possible risks of reversion to virulence after vaccination of layers were evaluated. Birds were vaccinated at five days of age or at five and 25 days of age. At 45 days of age, brown and white layers were challenged with SG and SE wild strains, respectively. Two assays to test the possibility of reversion to virulence were performed. Five successive bacterial passages in brown layers were carried out in the first assay. In the second assay, brown layers received a ten-fold concentrated inoculum of the SGcobScbiA strain and were evaluated for clinical signs and mortality. In both experiments, no birds that received the inoculation of the attenuated strain died. Additionally, the use of the mutant strain as a vaccine provided good protection levels against both challenge strains.
ABSTRACT
A leptospirose é uma doença de importância global que acomete humanos e alguns animais, causada por bactérias do gênero Leptospira. No Brasil são notificados cerca de três mil casos da doença em humanos por ano e 10% chegam a óbito. A leptospirose é um problema sério especialmente nos grandes centros urbanos devido á quantidade de roedores que são reservatórios de leptospira. A melhor forma de controle da leptospirose seria a prevenção com medidas de saneamento básico e conscientização da população. O projeto para sequenciamento do genoma da Leptospira Interrogans sorovar Copenhageni coordenado por um grupo de pesquisadores do Instituto Butantan e projeto Genoma funcional para desenvolvimento da vacina contra leptospirose, no qual nosso trabalho se insere, foram incentivados para necessidade de uma vacina eficaz para humanos...
Leptospirosis is a disease of global importance that affects humans and animals, caused by bacteria of the genus Leptospira. In Brasil, about three thousands human cases are notified every year 10% of the patients die. Leptospirosis is a serious issue, especialy in urban centre, due to the amount of rodents that are reservoirs of leptospira. The best way to control leptospirosis prevention with better sanitation measures and public awereness. The project for sequencing the genome of Leptospira interrogans serovar Copenhageni, coordinated by a group of researchers from Instituto Butantan and the Funtional genome for vaccine development, in wich our work belong, were encouraged by the need of an effective vaccine for humans...