RESUMO
Vibrio cholerae induces massive intestinal fluid secretion that continues for the life of the stimulated epithelial cells. Enhanced regional blood flow and peristalsis are required to adapt to this obligatory intestinal secretory challenge. Nitric oxide (NO) is a multifunctional molecule that modulates blood flow and peristalsis and possesses both cytotoxic and antibacterial activity. We demonstrate that, compared with those in asymptomatic control subjects, levels of stable NO metabolites (NO2-/NO3-) are significantly increased in sera from acutely ill Peruvian patients with natural cholera infection as well as from symptomatic volunteers from the United States infected experimentally with V. cholerae. In a rabbit ileal loop model in vivo, cholera toxin (CT) elicited fluid secretion and dose-dependent increases in levels of NO2-/NO3- in the fluid (P < 0.01). In contrast, lipopolysaccharide (LPS) elicited no such effects when applied to the intact mucosa. NO synthase (NOS) catalytic activity also increased in toxin-exposed tissues (P < 0.05), predominantly in epithelial cells. The CT-induced NOS activity was Ca2+ dependent and was not suppressed by dexamethasone. In conclusion, symptomatic V. cholerae infection induces NO production in humans. In the related animal model, CT, but not LPS, stimulated significant production of NO in association with increases in local Ca(2+)-dependent NOS activity in the tissues.
Assuntos
Cólera/metabolismo , Intestino Delgado/metabolismo , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico/biossíntese , Adulto , Idoso , Animais , Cólera/fisiopatologia , Toxina da Cólera/farmacologia , Diarreia/etiologia , Diarreia/fisiopatologia , Di-Hidrolipoamida Desidrogenase/análise , Inibidores Enzimáticos/farmacologia , Feminino , Humanos , Íleo/enzimologia , Intestino Delgado/efeitos dos fármacos , Masculino , Testes de Sensibilidade Microbiana , Pessoa de Meia-Idade , Molsidomina/análogos & derivados , Molsidomina/farmacologia , Músculo Liso/enzimologia , Nitritos/metabolismo , Peru , Coelhos , Valores de Referência , Fatores de Tempo , Estados Unidos , Vibrio cholerae/efeitos dos fármacosRESUMO
Cholera vaccine candidate Peru-15 was derived from a Vibrio cholerae O1 El Tor Inaba strain by deleting the cholera toxin genetic element, introducing the gene encoding cholera toxin B subunit into recA, and screening for nonmotility. In a controlled study, Peru-15 (2 x 10(8) cfu) was administered to 11 volunteers. No vaccinee developed diarrhea, and 10 of 11 had > 4-fold rises in vibriocidal antibody titers. One month later, 5 vaccinees and 5 control volunteers were challenged with wild type V. cholerae O1. Four of 5 controls developed diarrhea (mean, 1.9 L). Two Peru-15 vaccinees developed diarrhea, 1 with < 0.3 L and 1 with approximately 1.0 L; this latter volunteer had not developed a significant vibriocidal immune response to vaccination. Peru-15 shows promise as a single-dose, oral cholera vaccine that is safe, immunogenic, and protective.