Recombinant expression and studies on outer membrane protein from salmonella enterica typhimurium and their role in aberrant AID expression in B-cells

Abstract

Outer membrane proteins (OMPs) in gram-negative bacteria confer the ability to interact with the host, evade the immune system, and resist antibiotics. This study focused on YchP, a putative invasin protein of Salmonella enterica serovar Typhimurium, which allows the bacteria to adhere to and invade the host and potentially has a vital role in altering the host's immune response. We expressed, purified, and refolded YchP from a genetically modified Escherichia coli Rosetta strain. To explore how YchP affects the immune system, we introduced it to Raji human B-cells. We aimed to examine the effect of YchP in the production and expression of activation-induced cytidine deaminase (AID). This critical enzyme helps B-cells generate diverse antibodies through somatic hypermutation (SHM) and class-switch recombination (CSR). We evaluated the apparent change in protein AID levels and some regulatory genes of AID after stimulation with YchP based on the results of western blot from the stimulated Raji human B-cells. Our results suggested that AID protein levels decreased significantly. These results indicate that YchP may suppress AID activity, which could help bacteria evade the immune system by weakening antibody diversity. These experiments shed light on Salmonella's potential immune evasion strategy to protect itself. Further exploration is needed to understand how YchP triggers this response and what it means for bacterial infections and immune defense. Keywords: Salmonella enterica Typhimurium; YchP; Activation-induced cytidine deaminase (AID); Invasin.