Prophylactic Activity of Orally Administered FliD-Reactive Monoclonal SIgA Against Campylobacter Infection

Abstract

Campylobacter infection is one of the most common causes of bacterial gastroenteritis worldwide and a major global health threat due to the rapid development of antibiotic resistance. Currently, there are no vaccines approved to prevent campylobacteriosis, and rehydration is the main form of therapy. Secretory immunoglobulin A (SIgA) is the main antibody class found in mucous secretions, including human milk, and serves as the first line of defense for the gastrointestinal epithelium against enteric pathogens. In this study, we describe the prophylactic activity of orally delivered recombinant SIgA generated from two human monoclonal antibodies (CAA1 and CCG4) isolated for their reactivity against the flagellar-capping protein FliD, which is essential for bacteria motility and highly conserved across Campylobacter species associated with severe enteritis. In an immunocompetent weaned mouse model, a single oral administration of FliD-reactive SIgA CAA1 or CCG4 at 2 h before infection significantly enhances Campylobacter clearance at early stages post-infection, reducing the levels of inflammation markers associated with epithelial damage and polymorphonuclear (PMN) cells infiltration in the cecum lamina propria. Our data indicate that the prophylactic activity of CAA1 and CCG4 is not only dependent on the specificity to FliD but also on the use of the SIgA format, as the immunoglobulin G (IgG) versions of the same antibodies did not confer a comparable protective effect. Our work emphasizes the potential of FliD as a target for the development of vaccines and supports the concept that orally administered FliD-reactive SIgA can be developed to prevent or mitigate the severity of Campylobacter infections as well as the development of post-infection syndromes.

Recombinant Human Secretory IgA Induces Salmonella Typhimurium Agglutination and Limits Bacterial Invasion into Gut-Associated Lymphoid Tissues

“… 27 Other groups have expressed recombinant SIgA in transgenic plants, 57 but only recently have mammalian cell-based strategies proven fruitful. 29 , 30 , 37 Moreover, the structure of SIgA has been revealed through X-ray and cryo-EM techniques. 11 , 16 , 22 By all accounts, the recombinant human Sal4 SIgA produced in our study has potent biological activity in vitro and in vivo .…”

“…Sal4 mIgA, dIgA, and SIgA mAbs were generated as described previously. 29 In brief, Expi293 cells were transiently transfected with a construct containing the sequence for the Sal4 heavy chain variable domain (V H ) in a human IgA2 allotype m(2) alongside the corresponding Sal4 light chain (V L ). Sal4 dIgA and SIgA were cotransfected with a plasmid containing joining (J)-chain with Sal4 SIgA additionally expressed with a secretory component (SC).…”

The prospect of orally administered monoclonal secretory IgA (SIgA) antibodies to prevent enteric bacterial infections

“…48 The flagellar-capping protein FliD, also known as hook-associated protein 2 (HAP2), is a 70-kDa protein with high sequence conservation across the C. jejuni species, making it an appealing target for MAbs. 49,50 Perruzza and colleagues isolated FliD-reactive MAbs from IgA+ and IgG+ B memory cells from 50 human tonsillar samples. 50 B memory cells were immortalized and screened for clones expressing FliD-reactive antibodies, and the corresponding V H regions were cloned into human IgA1 or IgA2 vectors that were used to transiently co-transfect Expi293 cells in conjunction with vectors encoding V L , J-chain and SC.…”

“…49,50 Perruzza and colleagues isolated FliD-reactive MAbs from IgA+ and IgG+ B memory cells from 50 human tonsillar samples. 50 B memory cells were immortalized and screened for clones expressing FliD-reactive antibodies, and the corresponding V H regions were cloned into human IgA1 or IgA2 vectors that were used to transiently co-transfect Expi293 cells in conjunction with vectors encoding V L , J-chain and SC. Properly assembled SIgA was purified from cell supernatants by affinity and size exclusion chromatography.…”

“…The authors reported that 2 h pre-treatment of mice with IgG1 versions of CAA1 and CCG4 (200 μg each) had no demonstrable effect on C. jejuni colonization or campylobacter-induced inflammation, compared to the same amount of SIgA2. 50 Although the reasons why IgG1 failed to confer mucosal immunity against C. jejuni were not investigated, they did report that intestinal clearance ("half-life") of IgG1 was faster than SIgA.…”