b2D6 is a dimeric monoclonal immunoglobulin A (IgA) specific for the nonreducing terminal residue of Ogawa O-polysaccharide (OPS) of Vibrio cholerae. It was previously demonstrated that 2D6 IgA is sufficient to passively protect suckling mice from oral challenge with virulent V. cholerae O395. In this study, we sought to define the mechanism by which 2D6 IgA antibody protects the intestinal epithelium from V. cholerae infection. In a mouse ligated-ileal-loop assay, 2D6 IgA promoted V. cholerae agglutination in the intestinal lumen and limited the ability of the bacteria to associate with the epithelium, particularly within the crypt regions. In vitro fluorescence digital video microscopy analysis of antibody-treated V. cholerae in liquid medium revealed that 2D6 IgA not only induced the rapid (5-to 10-min) onset of agglutination but was an equally potent inhibitor of bacterial motility. Scanning electron microscopy showed that 2D6 IgA promoted flagellum-flagellum cross-linking, as well as flagellar entanglement with bacterial bodies, suggesting that motility arrest may be a consequence of flagellar tethering. However, monovalent 2D6 Fab fragments also inhibited V. cholerae motility, demonstrating that antibody-mediated agglutination and motility arrest are separate phenomena. While 2D6 IgA is neither bactericidal nor bacteriostatic, exposure of V. cholerae to 2D6 IgA (or Fab fragments) resulted in a 5-fold increase in surface-associated blebs, as well an onset of a wrinkled surface morphotype. We propose that the protective immunity conferred by 2D6 IgA is the result of multifactorial effects on V. cholerae, including agglutination, motility arrest, and possibly outer membrane stress. C holera is a life-threatening disease that remains endemic in many parts of the world (1-3). The etiological agent of cholera, Vibrio cholerae, is a noninvasive, Gram-negative bacterium that is acquired by humans via the fecal-oral route. Following ingestion, V. cholerae colonizes the mucosal surfaces of the small intestines, a process that is facilitated by the bacterium's single polar flagellum (4-7). Adherence to the epithelial surface requires expression of the toxin-coregulated pilus (TCP), in addition to other virulence factors (8), most notably, a potent ADP-ribosylating toxin known as cholera toxin (CT). CT disrupts chloride secretion within intestinal epithelial cells, inducing profuse water and electrolyte secretion and ultimately resulting in the hallmark "rice water diarrhea" associated with cholera. Cholera outbreaks frequently occur when water sanitation is disrupted, either following natural disasters or seasonally in areas where V. cholerae is endemic (9). The recent cholera outbreak in Haiti following the 2010 earthquake highlighted the ongoing potential of V. cholerae to cause mass causalities, as it resulted in more than half a million infected individuals and more than 7,000 deaths (10). Due to the rapid onset of symptoms and limited treatment options, control of cholera in many parts of the globe, particularly...

Vibrio cholerae is the causative agent of cholera, an acute diarrheal disease that remains endemic in many parts of the world. The mechanisms underlying immunity to cholera remain poorly defined, though it is increasingly clear that protection is associated with antibodies against lipopolysaccharide (LPS). Here we report that ZAC-3, a monoclonal antibody against the core/lipid A region of V. cholerae LPS is a potent inhibitor of V. cholerae flagellum-based motility in viscous and liquid environments. ZAC-3 arrested motility of the classical Ogawa strain O395, as well as the El Tor Inaba strain C6706. In addition, we demonstrate, in the neonatal mouse model, that ZAC-3 IgG and Fab fragments significantly reduced the ability of both V. cholerae strains O395 and C6706 to colonize the intestinal epithelium, revealing the potential of antibodies against the core/lipid A to contribute to immunity across biotypes, possibly through a mechanism involving motility arrest.

USA) was notified of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in 3 Malayan tigers (Panthera tigris jacksoni) at a zoo in the state. Felids, including domestic cats and exotic big cats, have greater susceptibility to SARS-CoV-2 infection than other species (1-4). Infected domestic cats can transmit the virus to other cats via respiratory droplets or direct contact (4-6). However, the risk for cat-to-human transmission remains unclear. We investigated the SARS-CoV-2 outbreak in Tennessee to determine its source and provide recommendations to control the spread of infection. The StudyTiger 1, the index case, began showing clinical signs of coronavirus disease (COVID-19), including lethargy,

We have produced and characterized two chimeric IgG1 monoclonal antibodies that bind different immunodominant epitopes on Vibrio cholerae lipopolysaccharide (LPS). MAb 2D6 IgG1 recognizes Ogawa O-polysaccharide antigen, while mAb ZAC-3 IgG1 recognizes core/lipid A moiety of Ogawa and Inaba LPS. Both antibodies were expressed using a Nicotiana benthamiana-based rapid antibody-manufacturing platform (RAMP) and evaluated in vitro for activities associated with immunity to V. cholerae, including vibriocidal activity, bacterial agglutination and motility arrest.

Vibrio cholerae O1 is one of two serogroups responsible for epidemic cholera, a severe watery diarrhea that occurs after the bacterium colonizes the human small intestine and secretes a potent ADP-ribosylating toxin. Immunity to cholera is associated with intestinal anti-lipopolysaccharide (LPS) antibodies, which are known to inhibit V. cholerae motility and promote bacterial cell-cell crosslinking and aggregation. Here we report that V. cholerae O1 classical and El Tor biotypes produce an extracellular matrix (ECM) when forcibly immobilized and agglutinated by ZAC-3 IgG, an intestinally-derived monoclonal antibody (MAb) against the core/lipid A region of LPS. ECM secretion, as demonstrated by crystal violet staining and scanning electron microscopy, occurred within 30 minutes of antibody exposure and peaked by 3 hours. Non-motile mutants of V. cholerae did not secrete ECM following ZAC-3 IgG exposure, even though they were susceptible to agglutination. The ECM was enriched in O-specific polysaccharide (OSP) but not Vibrio polysaccharide (VPS). Finally, we demonstrate that ECM production by V. cholerae in response to ZAC-3 IgG was associated with bacterial resistant to a secondary complement-mediated attack. In summary, we propose that V. cholerae O1, upon encountering anti-LPS antibodies in the intestinal lumen, secretes an ECM (or O-antigen capsule) possibly as a strategy to shield itself from additional host immune factors and to exit an otherwise inhospitable host environment.

colonizes the gastrointestinal (GI) tract, resulting in either asymptomatic carriage or a spectrum of diarrheal illness. If clinical suspicion for is low, stool samples are often submitted for analysis by multiplex molecular assays capable of detecting multiple GI pathogens, and some institutions do not report this organism due to concerns for high false-positive rates. Since clinical disease correlates with organism burden and molecular assays yield quantitative data, we hypothesized that numerical cutoffs could be utilized to improve the specificity of the Luminex xTAG GI pathogen panel (GPP) for infection. Analysis of cotested liquid stool samples ( = 1,105) identified a GPP median fluorescence intensity (MFI) value cutoff of ≥1,200 to be predictive of two-step algorithm (2-SA; 96.4% concordance) and toxin enzyme immunoassay (EIA) positivity. Application of this cutoff to a second cotested data set ( = 1,428) yielded 96.5% concordance. To determine test performance characteristics, concordant results were deemed positive or negative, and discordant results were adjudicated via chart review. Test performance characteristics for the MFI cutoff of ≥150 (standard), MFI cutoff of ≥1,200, and 2-SA were as follows (respectively): concordance, 95, 96, and 97%; sensitivity, 93, 78, and 90%; specificity, 95, 98, and 98%; positive predictive value, 67, 82, and 81%;, and negative predictive value, 99, 98, and 99%. To capture the high sensitivity for organism detection (MFI of ≥150) and high specificity for active infection (MFI of ≥1,200), we developed and applied a reporting algorithm to interpret GPP data from patients ( = 563) with clinician orders only for syndromic panel testing, thus enabling accurate reporting of for 95% of samples (514 negative and 5 true positives) irrespective of initial clinical suspicion and without the need for additional testing.

SARS-CoV-2 seroprevalence was low (<1%) in this large population of healthcare workers (HCWs) across the state of Tennessee (n=11,787) in May-June 2020. Among those with PCR results, 81.5% of PCR and antibody test results were concordant. SARS-CoV-2 seroprevalence was higher among HCWs working in high-community-transmission regions and among younger workers.ImportanceThese results may be seen as a baseline assessment of SARS-CoV-2 seroprevalence among HCWs in the American South during a period of growth, but not yet saturation, of infections among susceptible populations. In fact, this period of May-June 2020 was marked by the extension of renewed and sustained community-wide transmission after mandatory quarantine periods expired in several more populous regions of Tennessee. Where community transmission remains low, HCWs may still be able to effectively mitigate SARS-CoV-2 transmission, preserving resources for populations at high risk of severe disease, and these sorts of data help highlight such strategies.

Following an episode of cholera, a rapidly dehydrating, watery diarrhea caused by the Gram-negative bacterium, Vibrio cholerae O1, humans mount a robust anti-lipopolysaccharide (LPS) antibody response that is associated with immunity to subsequent re-infection. In neonatal mouse and rabbit models of cholera, passively administered anti-LPS polyclonal and monoclonal (MAb) antibodies reduce V. cholerae colonization of the intestinal epithelia by inhibiting bacterial motility and promoting vibrio agglutination. Here we demonstrate that human anti-LPS IgG MAbs also arrest V. cholerae motility and induce bacterial paralysis. A subset of those MAbs also triggered V. cholerae to secrete an extracellular matrix (ECM). To identify changes in gene expression that accompany antibody exposure and that may account for motility arrest and ECM production, we subjected V. cholerae O1 El Tor to RNA-seq analysis after treatment with ZAC-3 IgG, a high affinity MAb directed against the core/lipid A region of LPS. We identified &gt; 160 genes whose expression was altered following ZAC-3 IgG treatment, although canonical outer membrane stress regulons were not among them. ompS (VCA1028), a porin associated with virulence and indirectly regulated by ToxT, and norR (VCA0182), a σ54-dependent transcription factor involved in late stages of infection, were two upregulated genes worth noting.