Serum antitoxin antibodies mediate systemic and mucosal protection from Clostridium difficile disease in hamsters.

Clostridium difficile is the bacterial pathogen identified as the cause of pseudomembranous colitis and is principally responsible for nosocomial antibiotic-associated diarrhea and colitis. The pathologic findings associated with this infection are believed to be caused by two large (approximately 300-kDa) exotoxins, toxins A and B. Because of the mucosal nature of this infection, vaccination strategies aimed at providing prophylactic or therapeutic immune protection have included immunization by mucosal routes. Using the hamster model of C. difficile infection, we examined the protective efficacy of inactivated toxin (toxoid) vaccine formulations prepared as either culture filtrate or partially purified toxoid. We compared combination parenteral and mucosal vaccination regimens involving intranasal, intragastric, or rectal routes of immunization and found that rectal immunization in conjunction with intramuscular (i.m.) vaccination provided full protection of hamsters from death and diarrhea while the other mucosal routes did not. Protection was associated with high levels of toxin-neutralizing antibodies in serum. The requirement for adjuvants for protection was assessed by using sequential i.m. and rectal or i.m. vaccination regimens. Unexpectedly, i.m. immunization without adjuvant conferred the highest protection from death and diarrhea; this regimen elicited the highest serum anti-toxin B titers as well as toxin B neutralizing titers. Passive transfer of mouse antitoxin antibodies protected hamsters in a dose-dependent manner, demonstrating the principal role of circulating antitoxin antibodies in immunity from this toxin-mediated mucosal disease. These results suggest that prophylactic parenteral vaccination or intravenous immunotherapy could provide protection from C. difficile disease in humans.

A mutation in a new gene, bglJ, activates the bgl operon in Escherichia coli K-12.

A new mutation, bglJ4, has been characterized that results in the expression of the silent bgl operon. The bgl operon encodes proteins necessary for the transport and utilization of the aromatic beta-glucosides arbutin and salicin. A variety of mutations activate the operon and result in a Bgl+ phenotype. Activating mutations are located upstream of the bgl promoter and in genes located elsewhere on the chromosome. Mutations outside of the bgl operon occur in the genes encoding DNA gyrase and in the gene encoding the nucleoid associated protein H-NS. The mutation described here, bglJ4, has been mapped to a new locus at min 99 on the Escherichia coli K-12 genetic map. The putative protein encoded by the bglJ gene has homolgy to a family of transcriptional activators. Evidence is presented that increased expression of the bglJ product is needed for activation of the bgl operon.

Nuclease properties of two putative zinc finger peptides.

We studied the interaction of wheat germ 5S rRNA with synthetic polypeptides whose amino acid sequences were similar to that of the second zinc finger of Xenopus laevis transcriptional factor IIIA (TFIIIA). The results clearly show that in addition to weak 5S rRNA binding activity (data not shown), these two 30 amino acid long polypeptides hydrolyse some phosphodiester bonds of wheat germ 5S rRNA. The cleavage pattern of plant 5S rRNA is very specific and the cuts occur only after the pyrimidine residues. The same properties of these peptides were furthermore observed for E. coli tRNA(Phe). We found that the digestion specificity of both the zinc finger peptides is very similar to that of a pancreatic ribonuclease (RNase A).