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

Abstract

Serum IgG, which is mainly generated from IgG-secreting plasma cells in the bone marrow (BM), protects our body against various pathogens. We show here that the protein SiiE of <i>Salmonella</i> is both required and sufficient to prevent an efficient humoral immune memory against the pathogen by selectively reducing the number of IgG-secreting plasma cells in the BM. Attenuated SiiE-deficient <i>Salmonella</i> induces high and lasting titers of specific and protective <i>Salmonella</i>-specific IgG and qualifies as an efficient vaccine against <i>Salmonella</i> A SiiE-derived peptide with homology to laminin β1 is sufficient to ablate IgG-secreting plasma cells from the BM, identifying laminin β1 as a component of niches for IgG-secreting plasma cells in the BM, and furthermore, qualifies it as a unique therapeutic option to selectively ablate IgG-secreting plasma cells in autoimmune diseases and multiple myeloma.