Biology subjects

Mantis, N. J.

Publications and source records attributed to Mantis, N. J..

15 recordsLinked to original sources

bioRxiv2025

A Broadly Conserved Protective Epitope on the Lyme Disease Vaccine Antigen, OspA

Lyme disease, caused by the spirochete, Borreliella burgdorferi sensu latu (Bbsl), is a debilitating tickborne infection of increasing incidence in North America, Europe and Asia. While vaccines based on Outer surface protein A (OspA) have proven highly efficacious at blocking Bbsl tick-to-human transmission, the high degree of antigenic variability among the major OspA serotypes (ST) has made the development of a broadly cross protective vaccine difficult. Recent profiling of protective human monoclonal antibodies (mAbs) has suggested the existence of conserved epitopes situated within OspAs central {beta}-sheet (CBS), although direct comparisons of cross-serotype functionality has been hindered by biological differences among the major Bbsl genospecies. To address these issues, we developed a panel of isogenic B. burgdorferi viability reporter strains expressing the seven major OspA serotypes (ST1-7) and probed them with CBS-targeting mAbs to evaluate their complement-dependent borreliacidal activity. The mAbs segregated into three distinct classes with varying degrees of borreliacidal activity: class 1 mAbs exhibited potent killing against all seven OspA serotypes, while classes 2 and 3 had restricted or no activity against two of the seven serotypes. Structural analysis of Fabs derived from each class of mAbs in complex with OspA ST1 showed that they target overlapping epitopes spanning {beta}-strands 6-10 and involve contact with largely invariant residues. Further analysis of B. burgdorferi reporter strains expressing OspA variants from 17 additional Bbsl genospecies identified Lys-107 as a determinant of susceptibility for nearly all CBS mAbs. Taken together, these findings raise the prospect of structure-based design of a broadly protective monovalent Lyme disease vaccine. AUTHOR SUMMARYLyme disease, caused by the spirochete, Borreliella burgdorferi sensu latu (Bbsl), is a potentially debilitating tickborne infection of increasing incidence in North America, Europe and Asia. While vaccines based on Outer surface protein A (OspA) have proven highly efficacious at blocking Bbsl tick-to-human transmission, the genetic and serological heterogeneity of OspA across Borrelia genospecies has complicated matters. In this report, we use a collection of transmission-blocking human monoclonal antibodies to delineate a protective region (epitope) within the central core of OspA that is conserved across all major OspA serotypes. These results have important implications for engineering a broadly reactive Lyme disease vaccine.

immunology↗

bioRxiv2025

An Fc-silent OspA monoclonal antibody passively protects mice from tick and intradermal Borrelia burgdorferi challenge

The monoclonal antibody, LA-2, has played a pivotal role in the development of Outer surface protein A (OspA)-based vaccines for Lyme disease, a multisystem illness caused by the tick-borne spirochete, Borrelia burgdorferi sensu lato. Of particular significance was the demonstration more than three decades ago that LA-2 equivalent antibody titers, defined by a competitive-inhibition ELISA, serve as a reliable correlate of vaccine-induced protection across different species, including humans. In vitro characterization of LA-2 has identified both complement-dependent and -independent activities, although which of these attributes contribute to protection against B. burgdorferi remains unresolved. To address this issue, we generated and characterized an "Fc-silent" version of LA-2 IgG1 carrying so-called LALAPG substitutions (L234A, L235A, P329G). We demonstrate that LA-2 LALAPG retained OspA binding activity but was severely attenuated in in vitro complement deposition and complement-dependent borreliacidal assays. Nonetheless, LA-2 LALAPG was as effective as LA-2 at passively protecting C3H mice against nymphal tick-mediated B. burgdorferi challenge. LA-2 LALAPG was also equivalent to LA-2 in passively protecting BALB/c mice against intradermal B. burgdorferi challenge. In the intradermal challenge model, viable spirochetes were not recoverable 24 h after injection from skin biopsies of mice treated with LA-2 or LA-2 LALAPG, and an influx of pro-inflammatory cytokines and chemokines to the injection site was abrogated. Collectively, these results suggest that LA-2s primary mode of action involves direct physical interactions with the spirochete rather than complement-dependent killing. Elucidating these mechanisms may have implications for understanding the mechanistic correlates of OspA-based vaccine-induced immunity in humans.

immunology↗

bioRxiv2024

A Salmonella enterica serovar Typhimurium Genome-wide CRISPRi Screen Reveals a Role for Type 1 Fimbriae in Evasion of Antibody-Mediated Agglutination

The O5-specific monoclonal IgA antibody, Sal4, mediates the conversion of Salmonella enterica serovar Typhimurium (STm) from virulent, free-swimming cells to non-motile, multicellular aggregates in solution ("flocs") as well as biofilm-like associations at the air-liquid interface (ALI). We hypothesize that the rapid transition from an invasive to a non-invasive state reflects an adaptation of STm to Sal4 IgA exposure. In this report, we performed a genome-wide 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 ALI 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 fimW, which encodes a negative regulator of Type 1 Fimbriae (T1F) expression. Generation of a STm {Delta}fimW strain confirmed that the loss of FimW results in a hyperfimbriated phenotype and evasion of Sal4 IgA-mediated agglutination in solution. Closer examination of the fimW mutant revealed its propensity to form biofilms at the ALI specifically 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 protective secretory IgA antibodies influence STm virulence in the intestinal environment.

microbiology↗

bioRxiv2024

A Biparatopic Intrabody Renders Vero Cells Impervious to Ricin Intoxication

Expression of camelid-derived, single-domain antibodies (VHHs) within the cytoplasm of mammalian cells as "intrabodies" has opened-up novel avenues for medical countermeasures against fast-acting biothreat agents. In this report, we describe a heterodimeric intrabody that renders Vero cells virtually impervious to ricin toxin (RT), a potent Category B ribosome-inactivating protein (RIP). The intrabody consists of two structurally defined VHHs that target distinct epitopes on RTs enzymatic subunit (RTA): V9E1 targets RTAs P-stalk recruitment site, and V2A11 targets RTAs active site. Resistance to RT conferred by the biparatopic VHH construct far exceeded that of either of the VHHs alone and effectively inhibited all measurable RT-induced cytotoxicty in vitro. We propose that targeted delivery of bispecific intrabodies to lung tissues may represent a novel means to shield the airways from the effects of inhalational RT exposure.

immunology↗

bioRxiv2024

A refined human linear B cell epitope map of Outer surface protein C (OspC) from the Lyme disease spirochete, Borreliella burgdorferi

A detailed understanding of the human antibody response to Outer surface protein C (OspC) of Borrelellia burgdorferi has important implications for Lyme disease diagnostics and vaccines. In this report, a total of 13 peptides encompassing eight reported OspC linear B cell epitopes from OspC types A, B and K, including the conserved C-terminus (residues 193-210: peptide C10), were evaluated by multiplex immunoassay (MIA) for IgG reactivity with [~]700 human serum samples confirmed positive in a two-tiered Lyme disease diagnostic assay and [~]160 post-treatment Lyme disease (PTLD) serum samples. The VlsE C6-17 peptide was included as a positive control. Diagnostic serum IgG reacted with 11 of the 13 OspC-derived peptides, significantly more than controls, with the C10 peptide being the most reactive. In the PTLD serum samples, two OspC peptides including C10 were significantly more reactive than controls. Spearmans rank correlation matrices and hierarchical clustering indicated a strong correlation between C10 and VlsE C6-17 peptide reactivity but little demonstrable association between C10 and the other OspC peptides or recombinant OspC. OspC peptide reactivities (excluding C10) were strongly correlated with each other and were disproportionately influenced by a subset of pan-reactive samples. In the PTLD cohort, C10 clustered with the other OspC-derived peptides and was distinct from OspC and VlsE C6-17. The asynchronous serologic response to OspC, C10, and the OspC-derived peptides reveals the complexity of B cell responses to B. burgdorferi and confounds simple interpretation of antibody profiles associated with Lyme disease. IMPORTANCELyme disease is an emerging tick-borne infection caused by the spirochete, Borreliella burgdorferi. In humans, antibodies against spirochetal outer surface lipoproteins are proposed to play a role in disease resolution and in protection against reinfection. Some of those same antibodies also serve as diagnostic indicators of an active or history of Lyme disease. In this study, we sought to validate reported antibody binding sites on Outer surface protein C (OspC), a known target of both protective and diagnostic antibodies.

immunology↗

bioRxiv2024

Structure of a human monoclonal antibody in complex with Outer surface protein C (OspC) of the Lyme disease spirochete, Borreliella burgdorferi

Lyme disease is a tick-borne, multisystem infection caused by the spirochete, Borreliella burgdorferi. Although antibodies have been implicated in the resolution of Lyme disease, the specific B cell epitopes targeted during human infections remain largely unknown. In this study, we characterized and defined the structural epitope of a patient-derived bactericidal monoclonal IgG ("B11") against Outer surface protein C (OspC), a homodimeric lipoprotein necessary for B. burgdorferi tick-mediated transmission and early-stage colonization of vertebrate hosts. High-resolution epitope mapping was accomplished through hydrogen deuterium exchange-mass spectrometry (HDX-MS) and X-ray crystallography. Structural analysis of B11 Fab-OspCA complexes revealed the B11 Fabs associated in a 1:1 stoichiometry with the lateral faces of OspCA homodimers such that the antibodies are essentially positioned perpendicular to the spirochetes outer surface. B11s primary contacts reside within the membrane proximal regions of -helices 1 and 6 and adjacent loops 5 and 6 in one OspCA monomer. In addition, B11 spans the OspCA dimer interface, engaging opposing -helix 1, -helix 2, and loop 2-3 in the second OspCA monomer. The B11-OspCA structure is reminiscent of the recently solved mouse transmission blocking monoclonal IgG B5 in complex with OspCA, indicating a mode of engagement with OspC that is conserved across species. In conclusion, we provide the first detailed insight into the interaction between a functional human antibody and an immunodominant Lyme disease antigen long considered an important vaccine target.

immunology↗

bioRxiv2024

Single-domain antibodies reveal unique borreliacidal epitopes on the Lyme disease vaccine antigen, Outer surface protein A (OspA)

Camelid-derived, single-domain antibodies (VHHs) have proven to be extremely powerful tools in defining the antigenic landscape of immunologically heterogeneous surface proteins. In this report, we generated a phage-displayed VHH library directed against the candidate Lyme disease vaccine antigen, Outer surface protein A (OspA). Two alpacas were immunized with recombinant OspA serotype 1 (ST1) from Borrelia burgdorferi sensu stricto strain B31, in combination with the canine vaccine RECOMBITEK(R) Lyme containing lipidated OspA. The phage library was subjected to two rounds of affinity enrichment ("panning") against recombinant OspA, yielding 21 unique VHHs within two epitope bins, as determined through competition ELISAs with a panel of OspA-specific human monoclonal antibodies. Epitope refinement was conducted by hydrogen exchange-mass spectrometry (HX-MS). Six of the monovalent VHHs were expressed as human IgG1-Fc fusion proteins and shown to have functional properties associated with protective human monoclonal antibodies, including B. burgdorferi agglutination, outer membrane damage, and complement-dependent borreliacidal activity. The VHHs displayed unique reactivity profiles with the seven OspA serotypes associated with B. burgdorferi genospecies in the United States and Europe consistent with there being conserved epitopes across OspA serotypes that should be considered when designing and evaluating multivalent Lyme disease vaccines.

immunology↗

bioRxiv2023

Effects of aluminum-salt, CpG and emulsion adjuvants on the stability and immunogenicity of a virus-like particle displaying the SARS-CoV-2 receptor binding domain (RBD)

Second-generation COVID-19 vaccines with improved immunogenicity (e.g., breadth, duration) and availability (e.g., lower costs, refrigerator stable) are needed to enhance global coverage. In this work, we formulated a clinical-stage SARS-CoV-2 receptor binding domain (RBD) virus-like particle (VLP) vaccine candidate (IVX-411) with widely available adjuvants. Specifically, we assessed the in vitro storage stability and in vivo mouse immunogenicity of IVX-411 formulated with aluminum-salt adjuvants (Alhydrogel, AH and Adjuphos, AP), without or with the TLR-9 agonist CpG-1018 (CpG), and compared these profiles to IVX-411 adjuvanted with an oil-in-water nano-emulsion (AddaVax, AV). Although IVX-411 bound both AH and AP, lower binding strength of antigen to AP was observed by Langmuir binding isotherms. Interestingly, AH- and AP-adsorbed IVX-411 had similar storage stability profiles as measured by antigen binding assays (competitive ELISAs), but the latter displayed higher pseudovirus neutralizing titers (pNT) in mice, at levels comparable to titers elicited by AV-adjuvanted IVX-411. CpG addition to alum (AP or AH) resulted in a marginal trend of improved pNTs in stressed samples only, yet did not impact the storage stability profiles of IVX-411. In contrast, previous work with AH-formulations of a monomeric RBD antigen showed greatly improved immunogenicity and decreased stability upon CpG addition to alum. At elevated temperatures (25, 37{degrees}C), IVX-411 formulated with AH or AP displayed decreased in vitro stability compared to AV-formulated IVX-411and this rank-ordering correlated with in vivo performance (mouse pNT values). This case study highlights the importance of optimizing antigen-adjuvant interactions to develop low cost, aluminum-salt adjuvanted recombinant subunit vaccine candidates.

immunology↗

bioRxiv2023

mRNA delivery of dimeric human IgA protects mucosal tissues from bacterial infection

Monoclonal antibody (mAb) therapy is a promising infectious disease intervention strategy but is limited to IgG1 isotypes that have restricted access to mucosal sites. IgA is well-established as the predominant antibody isotype in mucosal secretions but is clinically underutilized. To enable development of IgA-based mAbs, we exploited mRNA platform technology and demonstrated expression of functional, antigen-specific IgA (IgAmRNA) that can limit bacterial invasion in the intestine and prevent colonization in the lung. Moreover, in vivo IgAmRNA had enhanced serum half-life and a greater degree of sialylation than a recombinantly produced IgA. The results underscore the potential of mRNA-based platforms to deliver protective human mAbs to mucosal surfaces and open new avenues to combat infectious diseases in the face of pervasive antibiotic resistance. One Sentence SummarymRNA-encoded human monoclonal IgA traffics to mucosal tissues and provides protection against bacterial challenge

immunology↗

bioRxiv2022

Structural Elucidation of a Protective B cell Epitope on Outer Surface Protein C (OspC) of the Lyme disease spirochete, Borreliella burgdorferi

Outer surface protein C (OspC) plays a pivotal role in mediating tick-to-host transmission and infectivity of the Lyme disease spirochete, Borreliella burgdorferi. OspC is a helical-rich homodimer that interacts with tick salivary proteins, as well as components of the mammalian immune system. Several decades ago, it was shown that the OspC-specific monoclonal antibody, B5, was able to passively protect mice from experimental tick-transmitted infection by B. burgdorferi strain B31. However, B5s epitope has never been elucidated, despite widespread interest in OspC as a possible Lyme disease vaccine antigen. Here we report the crystal structure of B5 antigen-binding fragments (Fabs) in complex with recombinant OspC type A (OspCA). Each OspC monomer within the homodimer was bound by a single B5 Fab in a side-on orientation, with contact points along OspCs -helix 1 and -helix 6, as well as interactions with the loop between a-helices 5 and 6. In addition, B5s complementarity-determining region (CDR) H3 bridged the OspC-OspC homodimer interface, revealing the quaternary nature of the protective epitope. To provide insight into the molecular basis of B5 serotype specificity, we solved the crystal structures of recombinant OspC types B and K and compared them to OspCA. This study represents the first structure of a protective B cell epitope on OspC and will aid in the rational design of OspC-based vaccines and therapeutics for Lyme disease. IMPORTANCEThe spirochete, Borreliella burgdorferi, is the causative agent of Lyme borreliosis, the most common tickborne disease in the United States. The spirochete is transmitted to humans during the course of a tick taking a bloodmeal. After B. burgdorferi is deposited into the skin of a human host, it replicates locally and spreads systemically, often resulting in clinical manifestations involving the central nervous system, joints, and/or heart. Antibodies directed against B. burgdorferis outer surface protein C (OspC) are known to block tick-to-host transmission, as well as dissemination of the spirochete within a mammalian host. In this report, we reveal the first atomic structure of one such antibody in complex with OspC. Our results have implications for the design of a Lyme disease vaccine capable to interfering with multiple stages in B. burgdorferi infection.

immunology↗

bioRxiv2022

The Flexible Linker of Decorin Binding Protein A from Borrelia burgdorferi is a Target of Antibodies in Lyme disease

Decorin binding protein A (DbpA) is a surface adhesin expressed by Borrelia burgdorferi, the causative agent of Lyme disease. While DbpA is one of the most immunogenic B. burgdorferi antigens in Lyme disease patients, the B cell epitopes recognized over the course of infection have not been defined. In this report we profiled [~]300 human serum samples from early, mid, and late-stage Lyme disease for IgM and IgG reactivity with DbpA and a tiled DbpA 18-mer peptide array derived from B.b. strains B31 and 297. Using ELISA and multiplex immunoassays (MIA), we identified 12 DbpA-derived peptides whose reactivity was elevated in Lyme disease patients as compared to healthy controls. The most reactive peptide ("A7") corresponds to the flexible loop between DbpAB31 -helix 1 and -helix 2, implicated in influencing DbpA binding to heparin and dermatan sulfate. An A7-like peptide is also reportedly a target of antibodies in Lyme neuroborreliosis patients. The remaining peptides, while highly reactive in serum samples across disease stages, likely represent non-native epitopes, as antibody reactivity to a subset of peptides in competition assays was unaffected by the addition of soluble DbpA. Moreover, peptide reactivity of any given patient sample rarely correlated with overall DbpA antibody levels, suggesting the antibodies were raised against DbpA degradation products. Insights into B cell epitopes on DbpA elicited during Lyme disease have important implications for understanding how B.burgdorferi persists in the face of an overwhelming antibody response. IMPORTANCEThe bacterium, Borrelia burgdorferi, is the causative agent of Lyme disease, the most reported tick-borne illness in the United States. In humans, clinical manifestations of Lyme disease are complex and can persist for months, even in the face of a robust antibody response directed against numerous B. burgdorferi surface proteins, including decorin binding protein A (DbpA), which is involved in early stages of infection. In this study we employed [~]300 serum samples from Lyme disease patients to better understand antibody reactivity with specific regions ("epitopes") of DbpA. We identified one epitope on DbpA recognized by antibodies from almost half of the serum samples tested and that, theoretically, should block DbpAs ability to function in promoting B. burgdorferi colonization of human hosts.

immunology↗

bioRxiv2021

Durable Immunity to Ricin Toxin Elicited by a Thermostable, Lyophilized Subunit Vaccine

The development of vaccines against biothreat toxins like ricin (RT) is considered an integral component of the United States national security efforts. RiVax(R) is a thermostable, lyophilized RT subunit vaccine adsorbed to aluminum salt adjuvant intended for use by military personnel and first responders. Phase 1 studies indicated that RiVax is safe and immunogenic, while a three dose, intramuscular vaccination regimen in non-human primates elicited protection against lethal dose RT challenge by aerosol. Here we investigated, in a mouse model, the durability of RiVax-induced antibody responses and corresponding immunity to lethal dose RT challenge. Groups of mice were subcutaneously administered 3 or 1 g of RiVax on days 0 and 21 and challenged with 10 x LD50 RT by injection at six different intervals over the course of twelve months. Serum antibody titers and epitope-specific competition assays were determined prior to each challenge. We report that the two-dose, 3 g regimen conferred near complete protection against RT challenge on day 35 and complete protection thereafter (challenge days 65, 95, 125, 245, and 365). The two-dose, 3 g regimen was superior to the 1 g regimen as revealed by slight differences in survival and morbidity scores (e.g., hypoglycemia, weight loss) on challenge days 35 and 365. In separate experiments, a single 3 g RiVax vaccination proved only marginally effective at eliciting protective immunity to RT, underscoring the necessity of a prime-boost regimen to achieve full and long-lasting protection against RT. IMPORTANCERicin toxin (RT) is a notorious biothreat, as exposure to even trace amounts via injection or inhalation can induce organ failure and death within a matter of hours. In this study, we advance the preclinical testing of a candidate RT vaccine known as RiVax(R). RiVax is a recombinant non-toxic derivative of RTs enzymatic subunit that has been evaluated for safety in Phase I clinical trials and efficacy in a variety of animal models. We demonstrate that two doses of RiVax is sufficient to protect mice from lethal dose RT challenge for up to one year. We describe kinetics and other immune parameters of the antibody response to RiVax and discuss how these immune factors may translate to humans.

immunology↗

bioRxiv2021

Mucoricin is a Ricin-Like Toxin that is Critical for the Pathogenesis of Mucormycosis

Fungi of the order Mucorales cause mucormycosis, a lethal infection with an incompletely understood pathogenesis. We now demonstrate that Mucorales fungi produce a toxin that plays a central role in virulence. Polyclonal antibodies against this toxin inhibit its ability to damage human cells in vitro, and prevent hypovolemic shock, organ necrosis, and death in mice with mucormycosis. RNAi inhibition of the toxin in Rhizopus delemar, compromises the ability of the fungus to damage host cells and attenuates virulence in mice. This 17 kDa toxin has structural and functional features of the plant toxin, ricin, including the ability to inhibit protein synthesis by its N-glycosylase activity, the existence of a motif that mediates vascular leak, and a lectin sequence. Antibodies against the toxin inhibit R. delemar- or toxin-mediated vascular permeability in vitro and cross-react with ricin. A monoclonal anti-ricin B chain antibody binds to the toxin and also inhibits its ability to cause vascular permeability. Therefore, we propose the name "mucoricin" for this toxin. Not only is mucoricin important in the pathogenesis of mucormycosis but our data suggest that a ricin- like toxin is produced by organisms beyond the plant and bacterial kingdoms. Importantly, mucoricin should be a promising therapeutic target.

microbiology↗

bioRxiv2020

Sites of Vulnerability on Ricin B Chain Revealed through Epitope Mapping of Toxin-Neutralizing Monoclonal Antibodies

Ricin toxins B subunit (RTB) is a multifunctional galactose (Gal)-/N-acetylgalactosamine (GalNac)-specific lectin that promotes efficient uptake and intracellular trafficking of ricins ribosome-inactivating subunit (RTA) into mammalian cells. Structurally, RTB consists of two globular domains (RTB-D1, RTB-D2), each divided into three homologous sub-domains (, {beta}, {gamma}). The two carbohydrate recognition domains (CRDs) are situated on opposite sides of RTB (sub-domains 1 and 2{gamma}) and function non-cooperatively. Previous studies have revealed two distinct classes of toxin-neutralizing, anti-RTB monoclonal antibodies (mAbs). Type I mAbs, exemplified by SylH3, inhibit ([~]90%) toxin attachment to cell surfaces, while type II mAbs, epitomized by 24B11, interfere with intracellular toxin transport between the plasma membrane and the trans-Golgi network (TGN). Localizing the epitopes recognized by these two classes of mAbs has proven difficult, in part because of RTBs duplicative structure. To circumvent this problem, full-length RTB or the two individual domains, RTB-D1 and RTB-D2, were expressed as pIII fusion proteins on the surface of filamentous phage M13 and subsequently used as "bait" in mAb capture assays. The results indicated that SylH3 captured RTB-D1, while 24B11 captured RTB-D2. Analysis of additional toxin-neutralizing and non-neutralizing mAbs along with single chain antibodies (VHHs) known to compete with SylH3 or 24B11 confirmed these domain assignments. These results not only indicate that so-called type I and type II mAbs segregate on the basis of domain specificity, but suggest that RTBs two domains may contribute to distinct steps in the intoxication pathway.

immunology↗

bioRxiv2019

Inhibition of Invasive Salmonella by Orally Administered IgA and IgG Monoclonal Antibodies

BackgroundNon-typhoidal Salmonella enterica strains, including serovar Typhimurium (STm), are an emerging cause of invasive disease among children and the immunocompromised, especially in regions of sub-Saharan Africa. STm invades the intestinal mucosa through Peyers patch tissues before disseminating systemically. While vaccine development efforts are ongoing, the emergence of multidrug resistant strains of STm affirms the need to seek alternative strategies to protect high-risk individuals from infection.\n\nMethodology/Principal FindingsIn this report we investigated the potential of an orally administered O5 serotype-specific IgA monoclonal antibody (mAb), called Sal4, to protect mice against invasive Salmonella enterica serovar Typhimurium (STm) infection. Sal4 IgA was delivered to mice prior to or concurrently with STm challenge. Infectivity was measured as bacterial burden in Peyers patch tissues one day after challenge. Using this model, we defined the minimal amount of Sal4 IgA required to significantly reduce STm uptake into Peyers patches. The relative efficacy of Sal4 in dimeric and secretory IgA (SIgA) forms was compared, as was a second lower avidity O5-specific IgA mAb that we produced from STm immunized mice. To assess the role of isotype in oral passive immunization, we engineered a recombinant IgG1 mAb carrying the Sal4 variable regions and evaluated its ability to block invasion of STm into epithelial cells in vitro and Peyers patch tissues.\n\nConclusions/SignificanceOur results demonstrate the potential of orally administered monoclonal IgA and SIgA, but not IgG, to passively immunize against invasive Salmonella. Nonethless, the prophylactic window of IgA/SIgA in the mouse was on the order of minutes, underscoring the need to develop formulations to protect mAbs in the gastric environment and to permit sustained release in the small intestine.\n\nAuthor SummaryThe bacterium Salmonella enterica is responsible for significant morbidity and mortality in the developed and developing worlds. While the pathogen is most renowed as the causative agent of typhoid fever, the emergence of invasive non-typhoid strains like S. enterica serovar Typhimurium (STm) are of great concern because of their propensity to cause severe disease in children under the age of five. In this report, we demonstrate in a mouse model that oral administration of a monoclonal antibody targeting the surface of STm is able to prevent the bacterium from infecting gastrointestinal tissues, the first step in the dissemination process. We show that IgA antibodies (which are normally found in the gut) were far superior than an equivalent IgG antibody (normally found in blood) at protecting the intestine from STm infection. These results lay the foundation for future studies aimed at the development of an orally administered antibody cocktail capable of providing temporary immunity to pathogens like S. enterica.

immunology↗