ToxR regulates virulence gene expression in non-O1 strains of Vibrio cholerae that cause epidemic cholera

Abstract

Vibrio cholerae serogroup 01 has historically been thought to be the exclusive cause of epidemic cholera. 0139 is a novel serogroup of V. cholerae which emerged on the Indian subcontinent in the last few months of 1992 and is the first non-O1 serogroup of V. cholerae to cause epidemic cholera. We have investigated the expression of some of the known virulence factors of classical and El Tor 01 strains of V. cholerae in clinical isolates of 0139 strains. We show that, in contrast to other non-O1 strains, 0139 strains express TcpA, the major subunit of the toxin-coregulated pilus found in 01 strains. As in 01 strains, the expression of cholera toxin and TcpA is coordinately regulated by environmental parameters in 0139 strains. Derivatives of 0139 strains that contain a toxR null mutation were constructed and used to demonstrate that the expression of cholera toxin, TcpA, and the outer membrane protein OmpU in 0139 strains, as in 01 strains, is dependent on ToxR. Two kinds of evidence suggest that 0139 strains are closely related to El Tor strains of V. cholerae. First, both 0139 and El Tor strains share a restriction fragment length polymorphism for tcpA, which distinguishes El Tor from classical strains of V. cholerae. Second, cholera toxin production in 0139 strains is greatly enhanced by culture conditions that have been previously shown to promote production of cholera toxin in El Tor strains and not in classical strains of V. cholerae. Although 0139 is a novel serotype of V. chokrae, 0139 strains conform to a fundamental theme that has evolved from the study of 01 strains: ToxR mediates coordinate regulation of virulence gene expression.

TcpA pilin sequences and colonization requirements for O1 and O139 Vibrio cholerae

“…The new 0139 serotype strain has a tcpA gene identical to the El Tor biotype, suggesting that perhaps this strain is indeed an El Tor derivative. These results are consistent with a study that used the primers we developed from the El Tor sequence to demonstrate the presence of tcpA in an 0139 isolate (Hall et ai, 1993) and a study that determined that 0139 TCP expression is under control of ToxR {Waldor and Mekalanos, 1994). Therefore, there are not a large number of antigenic variants that might thwart the development of TCP component vaccine formulations directed against colonization by any recognized epidemic cholera strain.…”

Evaluation of different subcellular fractions of Vibrio cholerae O139 in protection to challenge in experimental cholera

“…The puri¢ed LPS of O139 were found to be di¡erent from the LPS of O1 strains as also reported elsewhere [12]. The LPS of O1 strains exhibited lipid A, core oligosaccharides and O antigen, whereas the O139 strains lacked the O side-chain.…”

Regulation, replication, and integration functions of the Vibrio cholerae CTXφ are encoded by region RS2

“…V. cholerae chromosomal DNA was prepared with the Invitrogen Easy DNA kit. Southern blotting with probes conjugated with horseradish peroxidase to enable hybridization to be detected using a chemiluminescent substrate (Amersham), was performed as described previously (Waldor and Mekalanos, 1994). The attRS probe was a gel-purified 328 bp polymerase chain reaction (PCR) fragment derived from the 2740-80 chromosome using the previously described attUp and attDown primers (Pearson et al, 1993).…”