Type III secretion system apparatus protein SsaV (SsaV)

Type III secretion system apparatus protein SsaV is a vital structural component of the Salmonella Pathogenicity Island 2 (SPI-2) Type III Secretion System (T3SS) in Salmonella enterica serovar Typhi (UniProt P0CP55). It belongs to the YscV/FlhA family of proteins and is essential for the formation of the secretion apparatus that translocates effector proteins into host cells (Hensel et al., 1997). These effectors are crucial for the bacterium's ability to survive and replicate within host macrophages, a key step in the pathogenesis of typhoid fever (Khan et al., 2003). In the ZH9 (M01ZH09) vaccine strain, the ssaV gene is specifically deleted to attenuate the pathogen, preventing it from causing systemic disease while maintaining its immunogenicity (Hindley et al., 2007). This attenuation allows the strain to serve as a live-attenuated immunogen that elicits both mucosal and systemic immune responses (Kirkpatrick et al., 2006). Consequently, SsaV is a central molecule in the strategy to create safe and effective vaccines against Salmonella infections by balancing virulence and immune recognition (Boyle et al., 2007). The ZH9 strain is administered orally, mimicking the natural route of infection to stimulate local intestinal immunity (World Health Organization, 2023).

Other names

SsaVType III secretion system protein SsaVSPI-2 T3SS apparatus proteinssaV gene productSalmonella enterica serovar Typhi ZH9M01ZH09

The ZH9 vaccine strain is attenuated by the deletion of the ssaV gene, which prevents the assembly of the SPI-2 Type III secretion system and the subsequent translocation of virulence effectors, thereby blocking systemic spread while inducing protective immunity (Khan et al., 2003; Hindley et al., 2007).