RESUMO
Here we further investigate the pharmacological and toxicological properties of a cholera vaccine based on inactivated whole cells presented in either enteric coated (COA) or uncoated (U/C) tablet formulation from Vibrio cholerae C7258 strain. Tablets were dispersed in 2mL drinking water and administered orally to Sprague Dawley rats distributed in five groups (I COA7, II U/C7 immunized at 0, 7, 69days and III COA14, IV U/C14 immunized at 0, 14, 69days and V control group). Serum vibriocidal antibody response was measured after the administration of two doses with an interval of 7-14days. To further investigate the toxicological aspects a third dose was applied 10 weeks after the initial one. Animals were observed daily and water and food consumption was measured every other day. Periodic blood extractions were performed for hematology, biochemistry, and the titer of serum vibriocidal antibodies was determined. Anatomopathological analysis was performed at days 3 or 14 after the third dose. Results from clinical observations, as well as from water and food consumption and body weigh indicated no toxicity of the vaccine product. Meanwhile, no biological differences were found among different groups in hematological, hemo-chemistry, and anatomopathological studies. Moreover, enteric coated and uncoated tablets against human cholera were found to induce an immune response in rats.
Assuntos
Vacinas contra Cólera/imunologia , Cólera/prevenção & controle , Administração Oral , Animais , Anticorpos Antibacterianos/sangue , Vacinas contra Cólera/toxicidade , Feminino , Imunização , Masculino , Modelos Animais , Ratos , Ratos Sprague-Dawley , Comprimidos , Vacinas de Produtos Inativados/imunologia , Vacinas de Produtos Inativados/toxicidade , Vibrio cholerae/imunologiaRESUMO
BACKGROUND AND AIMS: A live attenuated vaccine candidate against human cholera has been developed from the genetically modified Vibrio cholerae O1, biotype El Tor, serotype Ogawa, 638 strain. Previous single dose toxicity and local tolerance studies have demonstrated that the product is innocuous in Sprague Dawley rats by oral route and single dose. The present paper describes a repeated dose toxicity study using a further dose compared to the proposed clinical schedule. METHODS: Sprague Dawley rats (140-180g) were treated with two doses of the vaccine candidate with a dedicated placebo formulation or were not treated at all (controls). The test products were inoculated at a 21-day interval. Animals were observed daily, body weight was determined weekly and food and water intakes were measured every other day. Three and 14 days after the last inoculation, groups of rats were humanely sacrificed, bled and macroscopically examined. Blood samples were taken for hematology, serum biochemistry and to determine the vibriocide antibody titers. A comprehensive list of tissue and organ samples was taken for microscopic studies. RESULTS: There was no mortality and no animal showed any clinical symptoms. Food and water intake, body weight, and hematological and biochemical variables did not show differences of toxicological and/or statistical relevance among the experimental groups. Macroscopic examination did not demonstrate any alterations and there were no histological findings of toxicological significance. CONCLUSIONS: The vaccine was considered potentially safe for human use as indicated by the results in Sprague Dawley rats.
Assuntos
Vacinas contra Cólera/toxicidade , Cólera/prevenção & controle , Vacinas Atenuadas/toxicidade , Animais , Cólera/imunologia , Vacinas contra Cólera/imunologia , Relação Dose-Resposta a Droga , Feminino , Humanos , Masculino , Placebos , Gravidez , Distribuição Aleatória , Ratos , Ratos Sprague-Dawley , Vacinas Atenuadas/imunologiaRESUMO
The recent spread of El Tor cholera in Latin America highlights the need for a safe and economical vaccine. The main approach for developing live recombinant vaccines has been to disarm known pathogenic strains of cholera toxin leaving intact antigens involved in protection. These recombinant vaccine candidates do not cause severe diarrhea, but they are too reactogenic for wide scale usage. We describe here a test capable of determining the diarrheagenic potential of attenuated V. cholerae strains. The functional test consists in the simultaneous recording of net water movement, electrical potential difference and short-circuit current across the human intestine ex vivo. We found that human tissues incubated with supernatants from the attenuated 638, 413 and 251a V. cholerae strains caused no changes in the ion conductances and water absorption in ileal and colon tissues allowing them to be assayed in volunteers.
Assuntos
Vacinas contra Cólera/toxicidade , Diarreia/imunologia , Mucosa Intestinal/microbiologia , Vibrio cholerae/imunologia , Animais , Diarreia/metabolismo , Diarreia/microbiologia , Modelos Animais de Doenças , Humanos , Íleo/imunologia , Íleo/metabolismo , Íleo/microbiologia , Técnicas In Vitro , Mucosa Intestinal/imunologia , Mucosa Intestinal/metabolismo , Dose Letal Mediana , Camundongos , Coelhos , Vacinas Atenuadas/toxicidade , Vibrio cholerae/patogenicidadeRESUMO
A mutant cholera toxin B subunit containing a G33E substitution was constructed and expressed in V. cholerae. The G33E amino acid substitution did not affect the amount of recombinant CTB secreted to the culture medium. The overexpression of the mutant B subunits in wild-type toxigenic cholera vibrios led to an 80% decrease in production of active cholera toxin in vitro and in vivo. Overexpression of BG33E subunits could be instrumental in the increase of the biosafety of live attenuated cholera candidate vaccine strains.