Sex Differences Persist After Treatment With Ivacaftor in People With Cystic Fibrosis.

BACKGROUND: Historically, studies show that female patients with cystic fibrosis (CF) have worse pulmonary outcomes than male patients, including decreased life expectancy. It is unknown whether this disparity persists in the new era of highly effective modulator therapies. Ivacaftor has been available in the United States for > 10 years, allowing for the opportunity to understand the impact this therapy may have on sex disparities in CF. We hypothesized that female patients will continue to show worse outcomes because we suspect that the disparity is not driven solely by ion channel dysfunction. RESEARCH QUESTION: Does a difference in outcomes between male and female patients persist after the initiation of ivacaftor in people with CF? STUDY DESIGN AND METHODS: We conducted a retrospective cohort study using the CF Foundation Patient Registry comparing changes in pulmonary exacerbation rate, lung function (FEV1 % predicted), and presence of Pseudomonas aeruginosa among male patients vs female patients before and after initiation of treatment with the highly effective modulator ivacaftor. RESULTS: The cohort comprised 1,900 people with CF who were treated with ivacaftor between 2010 and 2017; 928 patients (48.84%) were male and 972 patients (51.16%) were female with a mean age of 33.09 years. Male patients showed a significant decrease in pulmonary exacerbations after ivacaftor treatment (from 0.38 to 0.34; adjusted rate ratio, 0.89; P = .028), whereas female patients did not (from 0.48 to 0.45; adjusted rate ratio, 0.95; P = .174). FEV1 % predicted similarly decreased in both male and female patients before vs after ivacaftor treatment. P aeruginosa prevalence decreased to a similar extent in both male and female patients after ivacaftor treatment. INTERPRETATION: Our findings demonstrate that sex disparities in CF persist in those treated with ivacaftor because of differences in pulmonary exacerbations. More research is needed to determine the specific pathophysiologic drivers of this disparity.

A Bispecific Monoclonal Antibody Targeting Psl and PcrV Enhances Neutrophil-Mediated Killing of Pseudomonas aeruginosa in Patients with Bronchiectasis.

Rationale: Pseudomonas aeruginosa infection is associated with worse outcomes in bronchiectasis. Impaired neutrophil antimicrobial responses contribute to bacterial persistence. Gremubamab is a bivalent, bispecific monoclonal antibody targeting Psl exopolysaccharide and the type 3 secretion system component PcrV. Objectives: This study evaluated the efficacy of gremubamab to enhance killing of P. aeruginosa by neutrophils from patients with bronchiectasis and to prevent P. aeruginosa-associated cytotoxicity. Methods: P. aeruginosa isolates from a global bronchiectasis cohort (n = 100) underwent whole-genome sequencing to determine target prevalence. Functional activity of gremubamab against selected isolates was tested in vitro and in vivo. Patients with bronchiectasis (n = 11) and control subjects (n = 10) were enrolled, and the effect of gremubamab in peripheral blood neutrophil opsonophagocytic killing (OPK) assays against P. aeruginosa was evaluated. Serum antibody titers to Psl and PcrV were determined (n = 30; 19 chronic P. aeruginosa infection, 11 no known P. aeruginosa infection), as was the effect of gremubamab treatment in OPK and anti-cytotoxic activity assays. Measurements and Main Results: Psl and PcrV were conserved in isolates from chronically infected patients with bronchiectasis. Seventy-three of 100 isolates had a full psl locus, and 99 of 100 contained the pcrV gene, with 20 distinct full-length PcrV protein subtypes identified. PcrV subtypes were successfully bound by gremubamab and the monoclonal antibody-mediated potent protective activity against tested isolates. Gremubamab increased bronchiectasis patient neutrophil-mediated OPK (+34.6 ± 8.1%) and phagocytosis (+70.0 ± 48.8%), similar to effects observed in neutrophils from control subjects (OPK, +30.1 ± 7.6%). No evidence of competition between gremubamab and endogenous antibodies was found, with protection against P. aeruginosa-induced cytotoxicity and enhanced OPK demonstrated with and without addition of patient serum. Conclusions: Gremubamab enhanced bronchiectasis patient neutrophil phagocytosis and killing of P. aeruginosa and reduced virulence.

Concentrations of dehydroepiandrosterone-sulphate (DHEA-S) in people with cystic fibrosis on and off elexacaftor-tezacaftor-ivacaftor.

BACKGROUND: Levels of sulfated Dehydroepiandrosterone (DHEA-S) are unknown in people with Cystic Fibrosis (pwCF). DHEA-S is reported to have an inverse association with inflammation and warrants evaluation in pwCF. METHODS: We compared differences in DHEA-S and other hormones between pwCF (n = 180) and without CF (n = 180) and DHEA-S association with percent predicted forced expiratory volume in one second (ppFEV1). We also evaluated DHEA-S levels in people with CF on elexacaftor-tezacaftor-ivacaftor (ETI) (n = 145). RESULTS: PwCF (not on ETI) had lower DHEA-S levels compared to healthy non-CF controls. DHEA-S levels in individuals with CF on ETI were similar to those without CF. Lower DHEA-S levels were associated with lower ppFEV1. CONCLUSIONS: PwCF (not on ETI) have lower levels of DHEA-S than people without CF or people with CF on ETI. Additional studies are needed to investigate the impact of DHEA-S on the health of pwCF and mechanisms involved.

Prioritizing sexual and reproductive health research and care for people with cystic fibrosis: A 2023 workshop report from the Cystic Fibrosis Foundation Sexual Health, Reproduction, and Gender (SHARING) Research Working Group.

BACKGROUND: To address sexual and reproductive health (SRH) concerns among people with cystic fibrosis(PwCF), the CF Foundation created the Sexual Health, Reproduction, and Gender Research (SHARING) Working Group. This report summarizes CF community SRH research priorities and workshop discussions/future study planning. METHODS: Pre-workshop, we distributed a community prioritization survey on CF SRH research/care. During the workshop, we used results and reviewed existing research to establish research priorities and design studies to address identified knowledge gaps. RESULTS: A total of 303 respondents (85 % PwCF, 15 % caregivers) completed the survey. Highly-rated SRH topics were: 1) effects of CF modulator therapy on sex hormones; 2) effects of sex hormones on CF; 3) fertility; 4) pregnancy; and 5) SRH/mental health. Twenty-four workshop participants established the need for further research on sex hormones and CF, optimizing SRH care provision, and fertility/ART. CONCLUSION: SRH is an important and emerging area in CF and thoughtful consideration of community perspectives can ensure that future research is relevant and responsive.

Sex differences in outcomes of people with cystic fibrosis treated with elexacaftor/tezacaftor/ivacaftor.

BACKGROUND: There is a well described sex-disparity in outcomes of individuals with cystic fibrosis (CF), with females faring worse than males. Given the dramatic improvement in overall health of people with CF using CF transmembrane conductance regulator (CFTR) modulator therapy, elexacaftor/tezacaftor/ivacaftor (ETI), the sex-disparity in CF warrants re-examination. METHODS: We evaluated the effects of ETI use by sex prior to versus after initiation of ETI by pulmonary exacerbations (PEx), percent predicted forced expiratory volume in one second (ppFEV1), presence of Pseudomonas aeruginosa in sputum cultures, and body mass index (BMI). We used univariate and multivariable longitudinal regression adjusting for key confounders, such as age, race, CFTR modulator taken prior to ETI and baseline ppFEV1. RESULTS: We included 251 individuals started on ETI between January 2014 to September 2022. We collected data for a mean of 5.45 years pre-ETI and 2.38 years post-ETI. We found the adjusted presence of PEx decreased more in males than females pre- to post-ETI with the odds of having a PEx in males being 0.57 (43% reduction) versus females 0.75 (25% reduction) (p = 0.049). We found no statistical difference by sex for ppFEV1, presence of Pseudomonas aeruginosa or BMI pre- to post-ETI by sex. CONCLUSION: After treatment with ETI, there was a greater decline in PEx in males versus females. Long-term impact of ETI by sex is still unknown, but we will need to seek ways to effectively tailor care for individuals with CF and consider pharmacokinetic studies of ETI comparing males to females.

A protein-free vaccine stimulates innate immunity and protects against nosocomial pathogens.

Traditional vaccines are difficult to deploy against the diverse antimicrobial-resistant, nosocomial pathogens that cause health care-associated infections. We developed a protein-free vaccine composed of aluminum hydroxide, monophosphoryl lipid A, and fungal mannan that improved survival and reduced bacterial burden of mice with invasive blood or lung infections caused by methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, extended-spectrum beta-lactamase-expressing Escherichia coli, and carbapenem-resistant strains of Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The vaccine also conferred protection against the fungi Rhizopus delemar and Candida albicans. Efficacy was apparent by 24 hours and lasted for up to 28 days after a single vaccine dose, with a second dose restoring efficacy. The vaccine acted through stimulation of the innate, rather than the adaptive, immune system, as demonstrated by efficacy in the absence of lymphocytes that were abrogated by macrophage depletion. A role for macrophages was further supported by the finding that vaccination induced macrophage epigenetic alterations that modulated phagocytosis and the inflammatory response to infection. Together, these data show that this protein-free vaccine is a promising strategy to prevent deadly antimicrobial-resistant health care-associated infections.

Association between unplanned pregnancies and maternal exacerbations in cystic fibrosis.

INTRODUCTION: Following availability of the highly effective cystic fibrosis (CF) transmembrane conductance regulator modulator, elexacaftor/tezacaftor/ivacaftor, there was a near doubling of pregnancies reported in the United States (US) in people with CF. We sought to determine health impacts of planned (PP) versus unplanned pregnancies (UP). METHODS: We collected retrospective pregnancy data from January 2010-December 2020 from 11 US CF centers. After adjusting for potential confounding effects, we conducted multivariable, multilevel longitudinal regression analysis using mixed effect modeling to assess whether changes in percent predicted forced expiratory volume in one second (ppFEV1), body mass index (BMI), and pulmonary exacerbations (PEx) 1-year-pre- to 1-year-post-pregnancy were associated with pregnancy planning. RESULTS: Our analysis included 163 people with 226 pregnancies; the cohort had a mean age at conception of 29.6 years, mean pre-pregnancy ppFEV1 of 75.4 and BMI of 22.5 kg/m2. PpFEV1 declined in both PP (adjusted decline of -2.5 (95% CI: -3.8, -1.2)) and UP (adjusted decline of -3.0 (95% CI: -4.6, -1.4)) groups, they did not differ from each other (p = 0.625). We observed a difference in change in the annual number of PEx pre- to post-pregnancy (PP: 0.8 (0.7, 1.1); UP: 1.3 (1.0, 1.7); interaction effect p = 0.029). In a subset of people with available infant data, infants resulting from UP had more preterm births, lower APGAR scores, and more intensive care unit stays. CONCLUSIONS: Following UP, there is an increased trajectory for PEx and potentially for infant complications compared to PP. Clinicians should consider increased surveillance in the setting of UP.

Evaluation of an association between RANKL and OPG with bone disease in people with cystic fibrosis.

BACKGROUND: As people with Cystic Fibrosis (CF) live longer, extra-pulmonary complications such as CF-related bone disease (CFBD) are becoming increasingly important. The etiology of CFBD is poorly understood but is likely multifactorial. Bones undergo continuous remodeling via pathways including RANK (receptor activator of NF-κB)/sRANKL (soluble ligand)/OPG (osteoprotegerin). We sought to examine the association between sRANKL (stimulant of osteoclastogenesis) and OPG levels (inhibitor of osteoclast formation) and CFBD to investigate their potential utility as biomarkers of bone turnover in people with CF. METHODS: We evaluated sRANKL and OPG in plasma from people with CF and healthy controls (HC) and compared levels in those with CF to bone mineral density results. We used univariable and multivariable analysis to account for factors that may impact sRANKL and OPG. RESULTS: We found a higher median [IQR] sRANKL 10,896pg/mL [5,781-24,243] CF; 2,406pg.mL [659.50-5,042] HC; p= 0.0009), lower OPG 56.68pg/mL [36.28-124.70] CF; 583.20pg/mL [421.30-675.10] HC; p < 0.0001), and higher RANKL/OPG in people with CF no BD than in HC (p < 0.0001). Furthermore, we found a higher RANKL/OPG ratio 407.50pg/mL [214.40-602.60] CFBD; 177.70pg/mL [131.50-239.70] CF no BD; p = 0.007) in people with CFBD versus CF without bone disease. This difference persisted after adjusting for variables thought to impact bone health. CONCLUSIONS: The current screening recommendations of imaging for CFBD may miss important markers of bone turnover such as the RANKL/OPG ratio. These findings support the investigation of therapies that modulate the RANK/RANKL/OPG pathway as potential therapeutic targets for bone disease in CF.

Prospectively evaluating maternal and fetal outcomes in the era of CFTR modulators: the MAYFLOWERS observational clinical trial study design.

INTRODUCTION: Therapeutic advances have markedly increased life expectancy for those with cystic fibrosis (CF), resulting in a median predicted survival over 50 years. Consequently, people with CF (pwCF) are living through their reproductive years and the rate of pregnancy is rapidly rising. Despite the increased relevance of this topic, multicentre studies investigating the association between maternal health and choices made during pregnancy on maternal and fetal outcomes do not exist. Furthermore, there are very limited data on the outcomes following CF transmembrane conductance regulator (CFTR) modulator use during pregnancy and lactation. METHODS AND ANALYSIS: Maternal and Fetal Outcomes in the Era of Modulators (MAYFLOWERS) is a prospective, multicentre observational clinical trial which will enrol approximately 285 pregnant pwCF including those who are modulator ineligible and those who choose to continue or discontinue CFTR modulator therapy during pregnancy and lactation. The primary aim of this 35-month study is to assess whether lung function changes during pregnancy differ based on the continued use of modulators or other factors such as pre-existing comorbid conditions. Secondary objectives include evaluation of pregnancy related and obstetrical complications and changes in mental health. ETHICS AND DISSEMINATION: The design of this study required special consideration of study burden on pregnant and lactating people with chronic illness in the setting of a substantial number of unanswered questions under these conditions. MAYFLOWERS is the first prospective clinical trial examining pregnancy in CF; the outcomes will guide providers on pregnancy management in pwCF and others with chronic respiratory disease.

PD-L1+ neutrophils contribute to injury-induced infection susceptibility.

The underlying mechanisms contributing to injury-induced infection susceptibility remain poorly understood. Here, we describe a rapid increase in neutrophil cell numbers in the lungs following induction of thermal injury. These neutrophils expressed elevated levels of programmed death ligand 1 (PD-L1) and exhibited altered gene expression profiles indicative of a reparative population. Upon injury, neutrophils migrate from the bone marrow to the skin but transiently arrest in the lung vasculature. Arrested neutrophils interact with programmed cell death protein 1 (PD-1) on lung endothelial cells. A period of susceptibility to infection is linked to PD-L1+ neutrophil accumulation in the lung. Systemic treatment of injured animals with an anti-PD-L1 antibody prevented neutrophil accumulation in the lung and reduced susceptibility to infection but augmented skin healing, resulting in increased epidermal growth. This work provides evidence that injury promotes changes to neutrophils that are important for wound healing but contribute to infection susceptibility.

A Prospective Study of the Effects of Sex Hormones on Lung Function and Inflammation in Women with Cystic Fibrosis.

Rationale: Epidemiologic studies demonstrate worse outcomes in women with cystic fibrosis (CF) than men. Women are colonized earlier with respiratory pathogens and have increased rates of pulmonary exacerbations after puberty and near ovulation. The etiology of this disparity is unclear, but sex hormones may contribute to these differences.Objectives: We sought to explore whether natural hormonal fluctuations and hormonal contraception associate with changes in lung function, respiratory symptoms, or inflammatory markers.Methods: We prospectively followed women with CF who were not on hormonal contraceptives and reported regular menstrual cycles. We captured study visits at points that corresponded with menses, ovulation, and the luteal phase. A subset of subjects were subsequently placed on a standard oral estrogen/progesterone combination contraceptive pill, ethinyl estradiol/norethindrone (loestrin), and reevaluated. Measurements included lung function, symptom questionnaires, sweat tests, blood for hormone concentrations, and sputum for inflammatory markers, bacterial density, and cytology.Results: Twenty-three women participated in this study. Hormone concentrations were as expected on and off hormonal contraception. At times of peak estrogen (ovulation), there was a significant increase in sputum proinflammatory cytokines (neutrophil-free elastase) and a corresponding pattern of decrease in lung function. Proinflammatory cytokines (IL-8, TNF-α, and neutrophil-free elastase) improved when placed on hormone contraception.Conclusions: Our results show that there are potentially important fluctuations in inflammatory biomarkers in the lungs that correlate with changes in lung function in women with CF. Larger studies evaluating the impact of sex hormones on airway inflammation and immune response are necessary to better understand the clinical impact of these responses.

Patrolling Alveolar Macrophages Conceal Bacteria from the Immune System to Maintain Homeostasis.

During respiration, humans breathe in more than 10,000 liters of non-sterile air daily, allowing some pathogens access to alveoli. Interestingly, alveoli outnumber alveolar macrophages (AMs), which favors alveoli devoid of AMs. If AMs, like most tissue macrophages, are sessile, then this numerical advantage would be exploited by pathogens unless neutrophils from the blood stream intervened. However, this would translate to omnipresent persistent inflammation. Developing in vivo real-time intravital imaging of alveoli revealed AMs crawling in and between alveoli using the pores of Kohn. Importantly, these macrophages sensed, chemotaxed, and, with high efficiency, phagocytosed inhaled bacterial pathogens such as P. aeruginosa and S. aureus, cloaking the bacteria from neutrophils. Impairing AM chemotaxis toward bacteria induced superfluous neutrophil recruitment, leading to inappropriate inflammation and injury. In a disease context, influenza A virus infection impaired AM crawling via the type II interferon signaling pathway, and this greatly increased secondary bacterial co-infection.

Neutrophil Extracellular Traps Confine Pseudomonas aeruginosa Ocular Biofilms and Restrict Brain Invasion.

Bacterial biofilm infections are difficult to eradicate because of antibiotic insusceptibility and high recurrence rates. Biofilm formation by Pseudomonas aeruginosa, a leading cause of bacterial keratitis, is facilitated by the bacterial Psl exopolysaccharide and associated with heightened virulence. Using intravital microscopy, we observed that neutrophilic recruitment to corneal infections limits P. aeruginosa biofilms to the outer eye surface, preventing bacterial dissemination. Neutrophils moved to the base of forming biofilms, where they underwent neutrophil extracellular trap formation (NETosis) in response to high expression of the bacterial type-3 secretion system (T3SS). NETs formed a barrier "dead zone," confining bacteria to the external corneal environment and inhibiting bacterial dissemination into the brain. Once formed, ocular biofilms were resistant to antibiotics and neutrophil killing, advancing eye pathology. However, blocking both Psl and T3SS together with antibiotic treatment broke down the biofilm and reversed keratitis, suggesting future therapeutic strategies for this intractable infection.

Multidrug-resistant Pseudomonas aeruginosa from sputum of patients with cystic fibrosis demonstrates a high rate of susceptibility to ceftazidime-avibactam.

PURPOSE: Ceftazidime-avibactam is a novel antimicrobial combining a third-generation cephalosporin with a non-ß-lactam ß-lactamase inhibitor that was recently approved to treat Gram-negative hospital- and ventilator-acquired pneumonia. The use of ceftazidime-avibactam to treat Pseudomonas aeruginosa respiratory infections in patients with cystic fibrosis (CF) has not been evaluated. In this study, we assessed the ceftazidime-avibactam susceptibility of multidrug-resistant (MDR) P. aeruginosa sputum isolates from adults with CF. METHODS: Sputum was collected from individuals with CF, aged ≥18 years, known to be colonized with MDR P. aeruginosa, and tested for susceptibility to 11 different antipseudomonal antimicrobial agents. Isolates were included in the analysis if they were resistant to both ceftazidime and at least one agent in ≥3 different antimicrobial categories routinely used to treat P. aeruginosa. Subject demographics and clinical characteristics were collected. Ceftazidime-avibactam-resistant isolates were screened for the presence of ß-lactam-resistant mechanisms. RESULTS: Thirty-two P. aeruginosa isolates were analyzed, of which 23 isolates were sensitive to ceftazidime-avibactam (71.9%). Ten of the isolates were mucoid and 22 isolates were nonmucoid, both demonstrating >70% susceptibility to ceftazidime-avibactam. The most notable difference in the subjects with resistant strains was an older age and lower body mass index (BMI). Ceftazidime-avibactam-resistant strains showed elevated AmpC expression in >60% of the strains and loss of OprD detection in >70% of the strains. CONCLUSION: Ceftazidime-avibactam demonstrated a significant in vitro activity against highly resistant P. aeruginosa sputum isolates from individuals with CF. Further evaluation of the cause of resistance and clinical impact of ceftazidime-avibactam in CF patients with MDR P. aeruginosa is warranted.

Disparities in Mortality of Hispanic Patients with Cystic Fibrosis in the United States. A National and Regional Cohort Study.

RATIONALE: Patients of Hispanic origin with cystic fibrosis (CF) are the largest growing minority, representing 8.5% of patients with CF in the United States. No national survival analysis of this group has ever been undertaken. OBJECTIVES: We aimed to determine whether Hispanic ethnicity within the CF population is associated with worse outcomes and whether any geographic differences exist. METHODS: Using U.S. Cystic Fibrosis Foundation Patient Registry data from 2010 to 2014, we performed a retrospective cohort analysis comparing survival rates between Hispanics and non-Hispanics using Kaplan-Meier and Cox regression analysis. A subject's residence was categorized into geographic regions based on U.S. Census Bureau data: Northeast, Midwest, West, and South. MEASUREMENTS AND MAIN RESULTS: A total of 29,637 patients were included in the study; 2,493 identified themselves as Hispanic. Hispanics had a lower survival probability overall, with a mean age of death of 22.4 ± 9.9 years compared with non-Hispanics of 28.1 ± 10.0 years (P < 0.0001). Multivariate Cox proportional hazards modeling revealed that Hispanic patients with CF had a 1.27 times higher rate of death compared with non-Hispanics (95% confidence interval, 1.05-1.53) after adjusting for covariates including age, sex, genetic mutations, bacterial cultures, lung function, body mass index, use of CF respiratory therapies, low socioeconomic status, pancreatic enzyme use, and CF-related diabetes. When analyzed by region, Hispanics in the Midwest, Northeast, and West had shorter median survivals compared with non-Hispanics, which was not demonstrated in the South. CONCLUSIONS: Patients with CF of Hispanic origin have a higher mortality rate than non-Hispanic patients with CF. This pattern was seen in the Midwest, Northeast, and West but not in the South.

An engineered bispecific DNA-encoded IgG antibody protects against Pseudomonas aeruginosa in a pneumonia challenge model.

The impact of broad-spectrum antibiotics on antimicrobial resistance and disruption of the beneficial microbiome compels the urgent investigation of bacteria-specific approaches such as antibody-based strategies. Among these, DNA-delivered monoclonal antibodies (DMAbs), produced by muscle cells in vivo, potentially allow the prevention or treatment of bacterial infections circumventing some of the hurdles of protein IgG delivery. Here, we optimize DNA-delivered monoclonal antibodies consisting of two potent human IgG clones, including a non-natural bispecific IgG1 candidate, targeting Pseudomonas aeruginosa. The DNA-delivered monoclonal antibodies exhibit indistinguishable potency compared to bioprocessed IgG and protect against lethal pneumonia in mice. The DNA-delivered monoclonal antibodies decrease bacterial colonization of organs and exhibit enhanced adjunctive activity in combination with antibiotics. These studies support DNA-delivered monoclonal antibodies delivery as a potential strategy to augment the host immune response to prevent serious bacterial infections, and represent a significant advancement toward broader practical delivery of monoclonal antibody immunotherapeutics for additional infectious pathogens.DNA-delivered monoclonal antibodies (DMAbs) can be produced by muscle cells in vivo, potentially allowing prevention or treatment of infectious diseases. Here, the authors show that two DMAbs targeting Pseudomonas aeruginosa proteins confer protection against lethal pneumonia in mice.

Bispecific antibody targets multiple Pseudomonas aeruginosa evasion mechanisms in the lung vasculature.

Pseudomonas aeruginosa is a major cause of severe infections that lead to bacteremia and high patient mortality. P. aeruginosa has evolved numerous evasion and subversion mechanisms that work in concert to overcome immune recognition and effector functions in hospitalized and immunosuppressed individuals. Here, we have used multilaser spinning-disk intravital microscopy to monitor the blood-borne stage in a murine bacteremic model of P. aeruginosa infection. P. aeruginosa adhered avidly to lung vasculature, where patrolling neutrophils and other immune cells were virtually blind to the pathogen's presence. This cloaking phenomenon was attributed to expression of Psl exopolysaccharide. Although an anti-Psl mAb activated complement and enhanced neutrophil recognition of P. aeruginosa, neutrophil-mediated clearance of the pathogen was suboptimal owing to a second subversion mechanism, namely the type 3 secretion (T3S) injectisome. Indeed, T3S prevented phagosome acidification and resisted killing inside these compartments. Antibody-mediated inhibition of the T3S protein PcrV did not enhance bacterial phagocytosis but did enhance killing of the few bacteria ingested by neutrophils. A bispecific mAb targeting both Psl and PcrV enhanced neutrophil uptake of P. aeruginosa and also greatly increased inhibition of T3S function, allowing for phagosome acidification and bacterial killing. These data highlight the need to block multiple evasion and subversion mechanisms in tandem to kill P. aeruginosa.

Staphylococcus aureus α toxin potentiates opportunistic bacterial lung infections.

Broad-spectrum antibiotic use may adversely affect a patient's beneficial microbiome and fuel cross-species spread of drug resistance. Although alternative pathogen-specific approaches are rationally justified, a major concern for this precision medicine strategy is that co-colonizing or co-infecting opportunistic bacteria may still cause serious disease. In a mixed-pathogen lung infection model, we find that the Staphylococcus aureus virulence factor α toxin potentiates Gram-negative bacterial proliferation, systemic spread, and lethality by preventing acidification of bacteria-containing macrophage phagosomes, thereby reducing effective killing of both S. aureus and Gram-negative bacteria. Prophylaxis or early treatment with a single α toxin neutralizing monoclonal antibody prevented proliferation of co-infecting Gram-negative pathogens and lethality while also promoting S. aureus clearance. These studies suggest that some pathogen-specific, antibody-based approaches may also work to reduce infection risk in patients colonized or co-infected with S. aureus and disparate drug-resistant Gram-negative bacterial opportunists.