Abstract
The enteric pathogen, Salmonella enterica is a major cause of human gastroenteritis globally and with increasing bacterial resistance to antibiotics, alternative solutions are urgently needed. Single domain antibodies (sdAbs), the smallest antibody fragments that retain antigen binding specificity and affinity, are derived from variable heavy-chain only fragments (VHH) of camelid heavy-chain-only immunoglobulins. SdAbs typically contain a single disulfide bond simplifying recombinant protein production in microbial systems. These factors make sdAbs ideally suited for the development of effective anti-bacterial therapeutics. To this end, we generated an anti-Salmonella VHH library from which we screened for high affinity sdAbs. We present a novel sdAb (Abi-Se07) that targets the Salmonella virulence factor, FliC, required for bacterial motility and invasion of host cells. We demonstrate that Abi-Se07 bound FliC with a KD of 16.2 ± 0.1 nM. In addition, Abi-Se07 exhibited cross-serovar binding to whole cells of S. enterica serovar Typhimurium, Heidelberg, and Hadar. Abi-Se07 significantly inhibited bacterial motility and significantly reduced S. enterica colonization in a more native environment of chicken jejunum epithelium. Taken together, we have identified a novel anti-Salmonella sdAb and discuss future efforts toward therapeutic development.
Highlights
The Gram-negative bacterium, Salmonella enterica is a common contaminant in the food industry (Humphrey and Jørgensen, 2006; Crim et al, 2015)
SdAbs are derived from the camelid heavy chain antibodies (HcAbs) where each antigen binding arm is composed of a variable heavy-chain-only domain (VHH) with three complementarity determining regions (CDRs)
An anti-Salmonella library of single domain antibodies was created by immunizing alpacas with 10 different serovars of S. enterica
Summary
The Gram-negative bacterium, Salmonella enterica is a common contaminant in the food industry (Humphrey and Jørgensen, 2006; Crim et al, 2015). Production of sdAbs is easier and more cost effective than full length IgGs since sdAbs generally contain a single disulfide bond and can be expressed to high yields in either the periplasm or cytosol of microbial systems (Zarschler et al, 2013; Arbabi-Ghahroudi, 2017; Shriver-Lake et al, 2017; Liu and Huang, 2018; Suzuki et al, 2018). These factors are important considerations in the development and production of antibody treatments
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