Lindberg Samantha K, Willsey Graham G, Mantis Nicholas J
Department of Biomedical Sciences, University of Albany School of Public Health, Albany, New York, USA.
Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, New York, USA.
Infect Immun. 2025 May 13;93(5):e0057424. doi: 10.1128/iai.00574-24. Epub 2025 Apr 10.
The O5-specific monoclonal IgA antibody, Sal4, mediates the conversion of serovar Typhimurium (STm) from virulent, free-swimming cells to non-motile, multicellular biofilm-like aggregates within a matter of hours. We hypothesize that the rapid transition from an invasive to a non-invasive state is an adaptation of STm to Sal4 IgA exposure. In this report, we performed a genome-wide CRISPR interference (CRISPRi) screen to identify STm genes that influence multicellular aggregate formation in response to Sal4 IgA treatment. From a customized library of >36,000 spacers, ~1% (373) were enriched at the top of the culture supernatant after two consecutive rounds of Sal4 IgA treatment. The enriched spacers mapped to a diversity of targets, including genes involved in O-antigen modification, cyclic-di-GMP metabolism, outer membrane biosynthesis/signaling, and invasion/virulence, with the most frequently targeted gene being , which encodes a negative regulator of type 1 fimbriae (T1F) expression. Generation of a STm Δ strain confirmed that the loss of FimW activity results in a hyperfimbriated phenotype and evasion of Sal4 IgA-mediated agglutination in solution. Closer examination of the mutant revealed its propensity to form biofilms at the air-liquid interface in response to Sal4 exposure, suggesting that T1F "primes" STm to transition from a planktonic to a sessile state, possibly by facilitating bacterial attachment to abiotic surfaces. These findings shed light on the mechanism by which IgA antibodies influence STm virulence in the intestinal environment.
O5特异性单克隆IgA抗体Sal4可在数小时内介导鼠伤寒血清型沙门氏菌（STm）从具有毒性的自由游动细胞转变为无运动能力的多细胞生物膜样聚集体。我们推测，从侵袭性状态到非侵袭性状态的快速转变是STm对Sal4 IgA暴露的一种适应性反应。在本报告中，我们进行了全基因组CRISPR干扰（CRISPRi）筛选，以鉴定响应Sal4 IgA处理影响多细胞聚集体形成的STm基因。从一个包含超过36000个间隔序列的定制文库中，经过两轮连续的Sal4 IgA处理后，约1%（373个）间隔序列在培养上清液顶部富集。富集的间隔序列映射到多种靶点，包括参与O抗原修饰、环二鸟苷酸代谢、外膜生物合成/信号传导以及侵袭/毒力的基因，其中最常靶向的基因是 ，它编码1型菌毛（T1F）表达的负调控因子。STm Δ 菌株的产生证实，FimW活性的丧失导致菌毛过度表达的表型，并逃避了Sal4 IgA在溶液中介导的凝集作用。对 突变体的进一步检查发现，它在暴露于Sal4时倾向于在气液界面形成生物膜，这表明T1F可能通过促进细菌附着于非生物表面，使STm从浮游状态转变为固着状态。这些发现揭示了IgA抗体在肠道环境中影响STm毒力的机制。
