Matrixed CDR grafting: A neoclassical framework for antibody humanization and developability.

Discovery and optimization of a biotherapeutic monoclonal antibody requires a careful balance of target engagement and physicochemical developability properties. To take full advantage of the sequence diversity provided by different antibody discovery platforms, a rapid and reliable process for humanization of antibodies from nonhuman sources is required. Canonically, maximizing homology of the human variable region (V-region) to the original germline was believed to result in preservation of binding, often without much consideration for inherent molecular properties. We expand on this approach by grafting the complementary determining regions (CDRs) of a mouse anti-LAG3 antibody into an extensive matrix of human variable heavy chain (VH) and variable light chain (VL) framework regions with substantially broader sequence homology to assess the impact on complementary determining region-framework compatibility through progressive evaluation of expression, affinity, biophysical developability, and function. Specific VH and VL framework sequences were associated with major expression and purification phenotypes. Greater VL sequence conservation was correlated with retained or improved affinity. Analysis of grafts that bound the target demonstrated that initial developability criteria were significantly impacted by VH, but not VL. In contrast, cell binding and functional characteristics were significantly impacted by VL, but not VH. Principal component analysis of all factors identified multiple grafts that exhibited more favorable antibody properties, notably with nonoptimal sequence conservation. Overall, this study demonstrates that modern throughput systems enable a more thorough, customizable, and systematic analysis of graft-framework combinations, resulting in humanized antibodies with improved global properties that may progress through development more quickly and with a greater probability of success.

Development of an anti-Pseudomonas aeruginosa therapeutic monoclonal antibody WVDC-5244.

The rise of antimicrobial-resistant bacterial infections is a crucial health concern in the 21st century. In particular, antibiotic-resistant Pseudomonas aeruginosa causes difficult-to-treat infections associated with high morbidity and mortality. Unfortunately, the number of effective therapeutic interventions against antimicrobial-resistant P. aeruginosa infections continues to decline. Therefore, discovery and development of alternative treatments are necessary. Here, we present pre-clinical efficacy studies on an anti-P. aeruginosa therapeutic monoclonal antibody. Using hybridoma technology, we generated a monoclonal antibody and characterized its binding to P. aeruginosa in vitro using ELISA and fluorescence correlation spectroscopy. We also characterized its function in vitro and in vivo against P. aeruginosa. The anti-P. aeruginosa antibody (WVDC-5244) bound P. aeruginosa clinical strains of various serotypes in vitro, even in the presence of alginate exopolysaccharide. In addition, WVDC-5244 induced opsonophagocytic killing of P. aeruginosa in vitro in J774.1 murine macrophage, and complement-mediated killing. In a mouse model of acute pneumonia, prophylactic administration of WVDC-5244 resulted in an improvement of clinical disease manifestations and reduction of P. aeruginosa burden in the respiratory tract compared to the control groups. This study provides promising pre-clinical efficacy data on a new monoclonal antibody with therapeutic potential for P. aeruginosa infections.

Obesity and metabolic dysfunction drive sex-associated differential disease profiles in hACE2-mice challenged with SARS-CoV-2.

Severe outcomes from SARS-CoV-2 infection are highly associated with preexisting comorbid conditions like hypertension, diabetes, and obesity. We utilized the diet-induced obesity (DIO) model of metabolic dysfunction in K18-hACE2 transgenic mice to model obesity as a COVID-19 comorbidity. Female DIO, but not male DIO mice challenged with SARS-CoV-2 were observed to have shortened time to morbidity compared to controls. Increased susceptibility to SARS-CoV-2 in female DIO was associated with increased viral RNA burden and interferon production compared to males. Transcriptomic analysis of the lungs from all mouse cohorts revealed sex- and DIO-associated differential gene expression profiles. Male DIO mice after challenge had decreased expression of antibody-related genes compared to controls, suggesting antibody producing cell localization in the lung. Collectively, this study establishes a preclinical comorbidity model of COVID-19 in mice where we observed sex- and diet-specific responses that begin explaining the effects of obesity and metabolic disease on COVID-19 pathology.

SARS-CoV-2 Delta variant induces enhanced pathology and inflammatory responses in K18-hACE2 mice.

The COVID-19 pandemic has been fueled by SARS-CoV-2 novel variants of concern (VOC) that have increased transmissibility, receptor binding affinity, and other properties that enhance disease. The goal of this study is to characterize unique pathogenesis of the Delta VOC strain in the K18-hACE2-mouse challenge model. Challenge studies suggested that the lethal dose of Delta was higher than Alpha or Beta strains. To characterize the differences in the Delta strain's pathogenesis, a time-course experiment was performed to evaluate the overall host response to Alpha or Delta variant challenge. qRT-PCR analysis of Alpha- or Delta-challenged mice revealed no significant difference between viral RNA burden in the lung, nasal wash or brain. However, histopathological analysis revealed high lung tissue inflammation and cell infiltration following Delta- but not Alpha-challenge at day 6. Additionally, pro-inflammatory cytokines were highest at day 6 in Delta-challenged mice suggesting enhanced pneumonia. Total RNA-sequencing analysis of lungs comparing challenged to no challenge mice revealed that Alpha-challenged mice have more total genes differentially activated. Conversely, Delta-challenged mice have a higher magnitude of differential gene expression. Delta-challenged mice have increased interferon-dependent gene expression and IFN-γ production compared to Alpha. Analysis of TCR clonotypes suggested that Delta challenged mice have increased T-cell infiltration compared to Alpha challenged. Our data suggest that Delta has evolved to engage interferon responses in a manner that may enhance pathogenesis. The in vivo and in silico observations of this study underscore the need to conduct experiments with VOC strains to best model COVID-19 when evaluating therapeutics and vaccines.

Intranasal administration of BReC-CoV-2 COVID-19 vaccine protects K18-hACE2 mice against lethal SARS-CoV-2 challenge.

SARS-CoV-2 is a viral respiratory pathogen responsible for the current global pandemic and the disease that causes COVID-19. All current WHO approved COVID-19 vaccines are administered through the muscular route. We have developed a prototype two-dose vaccine (BReC-CoV-2) by combining the Receptor Binding Domain (RBD) antigen, via conjugation to Diphtheria toxoid (EcoCRM®). The vaccine is adjuvanted with Bacterial Enzymatic Combinatorial Chemistry (BECC), BECC470. Intranasal (IN) administration of BreC-CoV-2 in K18-hACE2 mice induced a strong systemic and localized immune response in the respiratory tissues which provided protection against the Washington strain of SARS-CoV-2. Protection provided after IN administration of BReC-CoV-2 was associated with decreased viral RNA copies in the lung, robust RBD IgA titers in the lung and nasal wash, and induction of broadly neutralizing antibodies in the serum. We also observed that BReC-CoV-2 vaccination administered using an intramuscular (IM) prime and IN boost protected mice from a lethal challenge dose of the Delta variant of SARS-CoV-2. IN administration of BReC-CoV-2 provided better protection than IM only administration to mice against lethal challenge dose of SARS-CoV-2. These data suggest that the IN route of vaccination induces localized immune responses that can better protect against SARS-CoV-2 than the IM route in the upper respiratory tract.

Long-Term Analysis of Pertussis Vaccine Immunity to Identify Potential Markers of Vaccine-Induced Memory Associated With Whole Cell But Not Acellular Pertussis Immunization in Mice.

Over two decades ago acellular pertussis vaccines (aP) replaced whole cell pertussis vaccines (wP) in several countries. Since then, a resurgence in pertussis has been observed, which is hypothesized to be linked, in part, to waning immunity. To better understand why waning immunity occurs, we developed a long-term outbred CD1 mouse model to conduct the longest murine pertussis vaccine studies to date, spanning out to 532 days post primary immunization. Vaccine-induced memory results from follicular responses and germinal center formation; therefore, cell populations and cytokines involved with memory were measured alongside protection from challenge. Both aP and wP immunization elicit protection from intranasal challenge by decreasing bacterial burden in both the upper and lower airways, and by generation of pertussis specific antibody responses in mice. Responses to wP vaccination were characterized by a significant increase in T follicular helper cells in the draining lymph nodes and CXCL13 levels in sera compared to aP mice. In addition, a population of B. pertussis+ memory B cells was found to be unique to wP vaccinated mice. This population peaked post-boost, and was measurable out to day 365 post-vaccination. Anti-B. pertussis and anti-pertussis toxoid antibody secreting cells increased one day after boost and remained high at day 532. The data suggest that follicular responses, and in particular CXCL13 levels in sera, could be monitored in pre-clinical and clinical studies for the development of the next-generation pertussis vaccines.

Evaluating Antibody Mediated Protection against Alpha, Beta, and Delta SARS-CoV-2 Variants of Concern in K18-hACE2 Transgenic Mice.

SARS-CoV-2 variants of concern (VoC) are impacting responses to the COVID-19 pandemic. Here, we utilized passive immunization using human convalescent plasma (HCP) obtained from a critically ill COVID-19 patient in the early pandemic to study the efficacy of polyclonal antibodies generated to ancestral SARS-CoV-2 against the Alpha, Beta, and Delta VoC in the K18 human angiotensin converting enzyme 2 (hACE2) transgenic mouse model. HCP protected mice from challenge with the original WA-1 SARS-CoV-2 strain; however, only partially protected mice challenged with the Alpha VoC (60% survival) and failed to save Beta challenged mice from succumbing to disease. HCP treatment groups had elevated receptor binding domain (RBD) and nucleocapsid IgG titers in the serum; however, Beta VoC viral RNA burden in the lung and brain was not decreased due to HCP treatment. While mice could be protected from WA-1 or Alpha challenge with a single dose of HCP, six doses of HCP could not decrease mortality of Delta challenged mice. Overall, these data demonstrate that VoC have enhanced immune evasion and this work underscores the need for in vivo models to evaluate future emerging strains. IMPORTANCE Emerging SARS-CoV-2 VoC are posing new problems regarding vaccine and monoclonal antibody efficacy. To better understand immune evasion tactics of the VoC, we utilized passive immunization to study the effect of early-pandemic SARS-CoV-2 HCP against, Alpha, Beta, and Delta VoC. We observed that HCP from a human infected with the original SARS-CoV-2 was unable to control lethality of Alpha, Beta, or Delta VoC in the K18-hACE2 transgenic mouse model of SARS-CoV-2 infection. Our findings demonstrate that passive immunization can be used as a model to evaluate immune evasion of emerging VoC strains.

Serological survey of SARS-CoV-2 incidence conducted at a rural West Virginia hospital.

The SARS-CoV-2 pandemic has affected all types of global communities. Differences in urban and rural environments have led to varying levels of transmission within these subsets of the population. To fully understand the prevalence and impact of SARS-CoV-2 it is critical to survey both types of community. This study establishes the prevalence of SARS-CoV-2 in a rural community: Montgomery, West Virginia. Approximately 10% of participants exhibited serological or PCR-based results indicating exposure to SARS-CoV-2 within 6 months of the sampling date. Quantitative analysis of IgG levels against SARS-CoV-2 receptor binding domain (RBD) was used to stratify individuals based on antibody response to SARS-CoV-2. A significant negative correlation between date of exposure and degree of anti-SARS-CoV-2 RBD IgG (R 2 = 0.9006) was discovered in addition to a correlation between neutralizing anti-SARS-CoV-2 antibodies (R 2 = 0.8880) and days post exposure. Participants were confirmed to have normal immunogenic profiles by determining serum reactivity B. pertussis antigens commonly used in standardized vaccines. No significant associations were determined between anti-SARS-CoV-2 RBD IgG and age or biological sex. Reporting of viral-like illness symptoms was similar in SARS-CoV-2 exposed participants greater than 30 years old (100% reporting symptoms 30-60 years old, 75% reporting symptoms >60 years old) in contrast to participants under 30 years old (25% reporting symptoms). Overall, this axnalysis of a rural population provides important information about the SARS-CoV-2 pandemic in small rural communities. The study also underscores the fact that prior infection with SARS-CoV-2 results in antibody responses that wane over time which highlights the need for vaccine mediated protection in the absence of lasting protection.

Reinvestigating the Coughing Rat Model of Pertussis To Understand Bordetella pertussis Pathogenesis.

Bordetella pertussis is a highly contagious bacterium that is the causative agent of whooping cough (pertussis). Currently, acellular pertussis vaccines (aP, DTaP, and Tdap) are used to prevent pertussis disease. However, it is clear that the aP vaccine efficacy quickly wanes, resulting in the reemergence of pertussis. Furthermore, recent work performed by the CDC suggest that current circulating strains are genetically distinct from strains of the past. The emergence of genetically diverging strains, combined with waning aP vaccine efficacy, calls for reevaluation of current animal models of pertussis. In this study, we used the rat model of pertussis to compare two genetically divergent strains Tohama 1 and D420. We intranasally challenged 7-week-old Sprague-Dawley rats with 108 viable Tohama 1 and D420 and measured the hallmark signs/symptoms of B. pertussis infection such as neutrophilia, pulmonary inflammation, and paroxysmal cough using whole-body plethysmography. Onset of cough occurred between 2 and 4 days after B. pertussis challenge, averaging five coughs per 15 min, with peak coughing occurring at day 8 postinfection, averaging upward of 13 coughs per 15 min. However, we observed an increase of coughs in rats infected with clinical isolate D420 through 12 days postchallenge. The rats exhibited increased bronchial restriction following B. pertussis infection. Histology of the lung and flow cytometry confirm both cellular infiltration and pulmonary inflammation. D420 infection induced higher production of anti-B. pertussis IgM antibodies compared to Tohama 1 infection. The coughing rat model provides a way of characterizing disease manifestation differences between B. pertussis strains.

SARS-CoV-2 B.1.1.7 and B.1.351 variants of concern induce lethal disease in K18-hACE2 transgenic mice despite convalescent plasma therapy.

SARS-CoV-2 variants of concern (VoCs) are impacting responses to the COVID-19 pandemic. Here we present a comparison of the SARS-CoV-2 USA-WA1/2020 (WA-1) strain with B.1.1.7 and B.1.351 VoCs and identify significant differences in viral propagation in vitro and pathogenicity in vivo using K18-hACE2 transgenic mice. Passive immunization with plasma from an early pandemic SARS-CoV-2 patient resulted in significant differences in the outcome of VoC-infected mice. WA-1-infected mice were protected by plasma, B.1.1.7-infected mice were partially protected, and B.1.351-infected mice were not protected. Serological correlates of disease were different between VoC-infected mice, with B.1.351 triggering significantly altered cytokine profiles than other strains. In this study, we defined infectivity and immune responses triggered by VoCs and observed that early 2020 SARS-CoV-2 human immune plasma was insufficient to protect against challenge with B.1.1.7 and B.1.351 in the mouse model.

Interplay of Antibody and Cytokine Production Reveals CXCL13 as a Potential Novel Biomarker of Lethal SARS-CoV-2 Infection.

The SARS-CoV-2 pandemic is impacting the global population. This study was designed to assess the interplay of antibodies with the cytokine response in SARS-CoV-2 patients. We demonstrate that significant levels of anti-SARS-CoV-2 antibody to receptor binding domain (RBD), nucleocapsid, and spike S1 subunit of SARS-CoV-2 develop over the first 10 to 20 days of infection. The majority of patients produced antibodies against all three antigens (219/255 SARS-CoV-2+ patient specimens, 86%), suggesting a broad response to viral proteins. Antibody levels to SARS-CoV-2 antigens were different based on patient mortality, sex, blood type, and age. Analyses of these findings may help explain variation in immunity between these populations. To better understand the systemic immune response, we analyzed the levels of 20 cytokines by SARS-CoV-2 patients throughout infection. Cytokine analysis of SARS-CoV-2+ patients exhibited increases in proinflammatory markers (interleukin 6 [IL-6], IL-8, IL-18, and gamma interferon [IFN-γ]) and chemotactic markers (IP-10 and eotaxin) relative to healthy individuals. Patients who succumbed to infection produced decreased IL-2, IL-4, IL-12, RANTES, tumor necrosis factor alpha (TNF-α), GRO-α, and MIP-1α relative to patients who survived infection. We also observed that the chemokine CXCL13 was particularly elevated in patients who succumbed to infection. CXCL13 is involved in B cell activation, germinal center development, and antibody maturation, and we observed that CXCL13 levels in blood trended with anti-SARS-CoV-2 antibody levels. Furthermore, patients who succumbed to infection produced high CXCL13 and had a higher ratio of nucleocapsid to RBD antibodies. This study provides insights into SARS-CoV-2 immunity implicating the magnitude and specificity of response in relation to patient outcomes.IMPORTANCE The SARS-CoV-2 pandemic is continuing to impact the global population, and knowledge of the immune response to COVID-19 is still developing. This study assesses the interplay of different parts of the immune system during COVID-19 disease. We demonstrate that COVID-19 patients produce antibodies to three proteins of the COVID-19 virus (SARS-CoV-2) and identify many other immunological proteins that are involved during infection. The data suggest that one of these proteins (CXCL13) may be a novel biomarker for severe COVID-19 that can be readily measured in blood. This information combined with our broad-scale analysis of immune activity during COVID-19 provides new information on the immunological response throughout the course of disease and identifies a novel potential marker for assessing disease severity.

Defining the Mechanistic Correlates of Protection Conferred by Whole-Cell Vaccination against Pseudomonas aeruginosa Acute Murine Pneumonia.

Pseudomonas aeruginosa is a Gram-negative pathogen that causes severe pulmonary infections associated with high morbidity and mortality in immunocompromised patients. The development of a vaccine against P. aeruginosa could help prevent infections caused by this highly antibiotic-resistant microorganism. We propose that identifying the vaccine-induced correlates of protection against P. aeruginosa will facilitate the development of a vaccine against this pathogen. In this study, we investigated the mechanistic correlates of protection of a curdlan-adjuvanted P. aeruginosa whole-cell vaccine (WCV) delivered intranasally. The WCV significantly decreased bacterial loads in the respiratory tract after intranasal P. aeruginosa challenge and raised antigen-specific antibody titers. To study the role of B and T cells during vaccination, anti-CD4, -CD8, and -CD20 depletions were performed prior to WCV vaccination and boosting. The depletion of CD4+, CD8+, or CD20+ cells had no impact on the bacterial burden in mock-vaccinated animals. However, depletion of CD20+ B cells, but not CD8+ or CD4+ T cells, led to the loss of vaccine-mediated bacterial clearance. Also, passive immunization with serum from WCV group mice alone protected naive mice against P. aeruginosa, supporting the role of antibodies in clearing P. aeruginosa We observed that in the absence of T cell-dependent antibody production, mice vaccinated with the WCV were still able to reduce bacterial loads. Our results collectively highlight the importance of the humoral immune response for protection against P. aeruginosa and suggest that the production of T cell-independent antibodies may be sufficient for bacterial clearance induced by whole-cell P. aeruginosa vaccination.

Human Liver Microsomes Immobilized on Magnetizable Beads: A Novel Approach to Study In Vitro Drug Metabolism.

Human liver microsomes (HLM) are a commonly used tool to study drug metabolism in vitro. Typical experiments conducted using suspensions of HLM can be challenging to separate from the incubation solution without lengthy ultracentrifugation steps. Magnetizable beads coated with silica (MGBS) were found to bind strongly to HLM, which could then be isolated and purified using a magnet. Binding of HLM to the MGBS (HLM-MGBS) was demonstrated to be mediated by strong interactions between microsomal phospholipids and MGBS, as artificially prepared phosphatidylcholine (PC) liposomes could be more efficiently captured by the MGBS. HLM-MGBS complexes retained functional cytochrome P450 and uridine-diphosphate-glucuronosyltransferase (UGT) activity as indicated by CYP2C8-mediated amodiaquine de-ethylation, CYP3A4-mediated midazolam 1'hydroxylation, UGT1A1-mediated glucuronidation of estradiol, UGT1A9-mediated glucuronidation of propofol, and UGT2B7-mediated glucuronidation of zidovudine. When comparing suspension HLM alone with HLM-MGBS complexes containing equivalent amounts of HLM, the intrinsic clearance (CLint) of CYP450 substrates was comparable; however, CLint of UGT1A1, UGT1A9, and UGT2B7 was increased in the HLM-MGBS system between 1.5- and 6-fold. HLM-MGBS used in an incubation could also be readily replaced with fresh HLM-MGBS to maintain the presence of active enzymes. Thus, HLM-MGBS demonstrate increased in vitro metabolic efficiency and manipulability, providing a new platform for determination of accurate metabolic parameters. SIGNIFICANCE STATEMENT: The following work describes the strong binding of HLM to magnetizable beads. In addition, the preservation of enzyme activity on the bound HLM provides a novel means to conduct preclinical metabolism studies.

Genomic and Phenotypic Diversity among Ten Laboratory Isolates of Pseudomonas aeruginosa PAO1.

Pseudomonas aeruginosa is an opportunistic pathogen found ubiquitously in the environment and commonly associated with airway infection in patients with cystic fibrosis. P. aeruginosa strain PAO1 is one of the most commonly used laboratory-adapted research strains and is a standard laboratory-adapted strain in multiple laboratories and strain banks worldwide. Due to potential isolate-to-isolate variability, we investigated the genomic and phenotypic diversity among 10 PAO1 strains (henceforth called sublines) obtained from multiple research laboratories and commercial sources. Genomic analysis predicted a total of 5,682 genes, with 5,434 (95.63%) being identical across all 10 strains. Phenotypic analyses revealed comparable growth phenotypes in rich media and biofilm formation profiles. Limited differences were observed in antibiotic susceptibility profiles and immunostimulatory potential, measured using heat-killed whole-cell preparations in four immortalized cell lines followed by quantification of interleukin-6 (IL-6) and IL-1ß secretion. However, variability was observed in the profiles of secreted molecular products, most notably, in rhamnolipid, pyoverdine, pyocyanin, Pseudomonas quinolone signal (PQS), extracellular DNA, exopolysaccharide, and outer membrane vesicle production. Many of the observed phenotypic differences did not correlate with subline-specific genetic changes, suggesting alterations in transcriptional and translational regulation. Taken together, these results suggest that individually maintained sublines of PAO1, even when acquired from the same parent subline, are continuously undergoing microevolution during culture and storage that results in alterations in phenotype, potentially affecting the outcomes of in vitro phenotypic analyses and in vivo pathogenesis studies.IMPORTANCE Laboratory-adapted strains of bacteria are used throughout the world for microbiology research. These prototype strains help keep research data consistent and comparable between laboratories. However, we have observed phenotypic variability when using different strains of Pseudomonas aeruginosa PAO1, one of the major laboratory-adopted research strains. Here, we describe the genomic and phenotypic differences among 10 PAO1 strains acquired from independent sources over 15 years to understand how individual maintenance affects strain characteristics. We observed limited genomic changes but variable phenotypic changes, which may have consequences for cross-comparison of data generated using different PAO1 strains. Our research highlights the importance of limiting practices that may promote the microevolution of model strains and calls for researchers to specify the strain origin to ensure reproducibility.

Reciprocal cross-species induction of outer membrane vesicle biogenesis via secreted factors.

Delivery of cargo to target cells is fundamental to bacterial competitiveness. One important but poorly understood system, ubiquitous among Gram-negative organisms, involves packaging cargo into outer membrane vesicles (OMVs). These biological nanoparticles are involved in processes ranging from toxin delivery to cell-cell communication. Despite this, we know comparatively little about how OMVs are formed. Building upon the discovery that the Pseudomonas Quinolone Signal (PQS) stimulates OMV biogenesis in Pseudomonas aeruginosa, we proposed a model where PQS interacts with the outer membrane to induce curvature and ultimately OMV formation. Though this model is well supported in P. aeruginosa, it remained unclear whether other organisms produce similar compounds. Here we describe the development of a tightly controlled experimental system to test the interaction of bacterially-produced factors with target cells. Using this system, we show that multiple species respond to PQS by increasing OMV formation, that PQS accumulates in the induced vesicles, and that other bacteria secrete OMV-promoting factors. Analysis of induced vesicles indicates that recipient-mediated mechanisms exist to control vesicle size and that relatedness to the producer organism can dictate susceptibility to OMV-inducing compounds. This work provides evidence that small molecule induced OMV biogenesis is a widely conserved process and that cross-talk between systems may influence OMV production in neighboring bacteria.

Neuron-specific regulation of superoxide dismutase amid pathogen-induced gut dysbiosis.

Superoxide dismutase, an enzyme that converts superoxide into less-toxic hydrogen peroxide and oxygen, has been shown to mediate behavioral response to pathogens. However, it remains largely unknown how superoxide dismutase is regulated in the nervous system amid pathogen-induced gut dysbiosis. Although there are five superoxide dismutases in C. elegans, our genetic analyses suggest that SOD-1 is the primary superoxide dismutase to mediate the pathogen avoidance response. When C. elegans are fed a P. aeruginosa diet, the lack of SOD-1 contributes to enhanced lethality. We found that guanylyl cyclases GCY-5 and GCY-22 and neuropeptide receptor NPR-1 act antagonistically to regulate SOD-1 expression in the gustatory neuron ASER. After C. elegans ingests a diet that contributes to high levels of oxidative stress, the temporal regulation of SOD-1 and the SOD-1-dependent response in the gustatory system demonstrates a sophisticated mechanism to fine-tune behavioral plasticity. Our results may provide the initial glimpse of a strategy by which a multicellular organism copes with oxidative stress amid gut dysbiosis.

Superoxide dismutase SOD-1 modulates C. elegans pathogen avoidance behavior.

The C. elegans nervous system mediates protective physiological and behavioral responses amid infection. However, it remains largely unknown how the nervous system responds to reactive oxygen species (ROS) activated by pathogenic microbes during infection. Here, we show superoxide dismutase-1 (SOD-1), an enzyme that converts superoxide into less toxic hydrogen peroxide and oxygen, functions in the gustatory neuron ASER to mediate C. elegans pathogen avoidance response. When C. elegans first encounters pathogenic bacteria P. aeruginosa, SOD-1 is induced in the ASER neuron. After prolonged P. aeruginosa exposure, ASER-specific SOD-1 expression is diminished. In turn, C. elegans starts to vacate the pathogenic bacteria lawn. Genetic knockdown experiments reveal that pathogen-induced ROS activate sod-1 dependent behavioral response non cell-autonomously. We postulate that the delayed aversive response to detrimental microbes may provide survival benefits by allowing C. elegans to temporarily utilize food that is tainted with pathogens as an additional energy source. Our data offer a mechanistic insight into how the nervous system mediates food-seeking behavior amid oxidative stress and suggest that the internal state of redox homeostasis could underlie the behavioral response to harmful microbial species.