Salmonella SiiE prevents an efficient humoral immune memory by interfering with IgG+ plasma cell persistence in the bone marrow

Serum IgG, which is mainly generated from IgG- secreting plasma cellsin the bone marrow (BM), protects our body against various pathogens. We show here that the protein SiiE of Salmonellais both required and sufficient to prevent an efficient humoral immunememory against the pathogen by selectively reducing the number of IgG- secreting plasma cellsin the BM. Attenuated SiiE-deficient Salmonellainduces high and lasting titers of specific and protective Salmonella-specific IgG and qualifies as an efficient vaccine against Salmonella. A SiiE-derived peptide with homology to lamininβ1 is sufficient to ablate IgG- secreting plasma cellsfrom the BM, identifying lamininβ1 as a component of niches for IgG- secreting plasma cellsin the BM, and furthermore, qualifies it as a unique therapeutic option to selectively ablate IgG- secreting plasma cellsin autoimmune diseases and multiple myeloma.