pCD1pYV

pCD1pYV, commonly referred to as pCD1 or pYV, is a virulence plasmid found in pathogenic Yersinia species, including Yersinia pestis and Yersinia pseudotuberculosis. It is a circular extrachromosomal DNA molecule, typically about 70 kilobases in size, that carries the genetic determinants required for a functioning type III secretion system (T3SS) and associated virulence factors. The plasmid’s presence is a major determinant of the bacterium’s ability to cause disease in animal hosts.

A central feature of pCD1pYV is the Ysc-Yop type III secretion system gene cluster, which encodes the needle-like secretion apparatus and a set of secreted effector proteins, or Yops. These effectors, including YopE, YopH, YopJ, YopM, YopT, and others, disrupt host cell signaling to inhibit phagocytosis and modulate inflammatory responses. The plasmid also contains translocator components, chaperones (such as Syc proteins) that assist in effector delivery, and regulatory elements that coordinate expression in response to host contact. The Lcr region, including regulators and the LcrV (V antigen), helps control the secretion process and virulence.

The pCD1pYV plasmid is essential for full virulence in Yersinia infections; loss or curing of the plasmid markedly attenuates virulence in experimental models. While most notably associated with Y. pestis, it is also found in related pathogenic Yersinia species and has been a focal point in research on the mechanisms of type III secretion and bacterial pathogenesis.