SPI1 and infection: However, infection with either SPI-1 or SPI-2 mutant abrogates the induction of Sirt1, whereas only SPI-2 mutants (∆ssaV and ∆steE) and not SPI-1 mutant infection caused reduction in Sirt3 transcript-level expression in the infected macrophages, implicating the role of SPI-1 and SPI-2 genes in triggering SIRT1 and SIRT3 in the infected macrophages (Figure 1I and J).