Nutrition and the gut-brain axis in neonatal brain injury and development.

Early nutritional exposures, including during embryogenesis and the immediate postnatal period, affect offspring outcomes in both the short- and long-term. Alterations of these modifiable exposures shape the developing gut microbiome, intestinal development, and even neurodevelopmental outcomes. A gut-brain axis exists, and it is intricately connected to early life feeding and nutritional exposures. Here, we seek to discuss the (1) origins of the gut-brain access and relationship with neurodevelopment, (2) components of human milk (HM) beyond nutrition and their role in the developing newborn, and (3) clinical application of nutritional practices, including fluid management and feeding on the development of the gut-brain axis, and long-term neurodevelopmental outcomes. We conclude with a discussion on future directions and unanswered questions that are critical to provide further understanding and insight into how clinicians and healthcare providers can optimize early nutritional practices to ensure children not only survive, but thrive, free of neurodevelopmental impairment.

Contemporary definitions of infant growth failure and neurodevelopmental and behavioral outcomes in extremely premature infants at two years of age.

BACKGROUND: Associations of 2-year neurodevelopmental and behavioral outcomes with growth trajectories of preterm infants are unknown. METHODS: This secondary analysis of a preterm cohort examined in-hospital and discharge to 2-year changes in anthropometric z-scores. Two-year follow-up included Bayley Scales of Infant Development (BSID-III) and Child Behavior Checklist. RESULTS: Among 590 infants, adjusted in-hospital growth was not associated with any BSID-III subscale. Occipitofrontal circumference (OFC) growth failure (GF) in-hospital was associated with increased adjusted odds of attention problems (aOR 1.65 [1.03, 2.65]), aggressive behavior (aOR 2.34 [1.12, 4.89]), and attention-deficit-hyperactivity symptoms (aOR 1.86 [1.05, 3.30]). Infants with OFC GF at 2 years had lower adjusted BSID-III language scores (-4.0 [-8.0, -0.1]), increased odds of attention problems (aOR 2.29 [1.11, 4.74]), aggressive behavior (aOR 3.09 [1.00, 9.56]), and externalizing problems (aOR 3.01 [1.07, 8.45]) compared to normal OFC growth cohort. CONCLUSION: Infants with OFC GF are at risk for neurodevelopmental and behavioral impairment. CLINICAL TRIAL REGISTRATION: This study is a secondary analysis of pre-existing data from the PENUT Trial Registration: NCT01378273.

Maternal COVID-19 Infection Associated with Fetal Systemic Inflammatory Complications in COVID-19-Negative Neonates: A Case-Series.

OBJECTIVE: This study aimed to examine fetal and neonatal inflammatory and neurologic complications associated with maternal coronavirus disease 2019 (COVID-19) infection. STUDY DESIGN: Case-series using a convenience sample of neonates cared for in a large referral-based children's hospital neonatal intensive care unit between September 2021 and May 2022. RESULTS: We identified seven neonates with exposure to maternal severe acute respiratory syndrome related coronavirus 2 (SARS-CoV-2) and a presentation consistent with inflammatory complications. All had some degree of neurologic injury with neuroimaging findings including restricted diffusion indicating injury in the white matter, cortex, deep gray structures, and splenium of the corpus callosum as well as intracranial hemorrhage. In addition, many infants had cytopenia and abnormal coagulation studies. Placental pathology, when available, revealed inflammation, clot with calcifications, and hematomas with associated infarcts. CONCLUSION: Neonates born to mothers with SARS-CoV-2, even when negative for the virus themselves, may have complications consistent with a systemic inflammatory syndrome. Placental pathology as well as neurologic imaging in infants with neurologic findings may help to support this diagnosis. KEY POINTS: · A systemic inflammatory response may cause illness in babies born to mothers with a history of COVID-19.. · Inflammatory markers and placental pathology are helpful in supporting this diagnosis.. · Consider neuroimaging in infants of mothers with a history of COVID-19 with neurologic findings..

Contemporary Definitions of Infant Growth Failure and Neurodevelopmental and Behavioral Outcomes in Extremely Premature Infants at Two Years of Age.

Introduction: The association of 2-year neurodevelopmental and behavioral outcomes with in-hospital or post-discharge growth failure (GF) using contemporary definitions for preterm infants is unknown. Methods: In a secondary analysis of a preterm cohort, changes in anthropometric z-scores were examined between birth and hospital discharge, and from discharge to 2 years. The 2-year evaluation included Bayley Scales of Infant Development (BSID-III) and Child Behavior Checklist (CBCL). Results: Among 629 infants, accelerated linear growth from birth to discharge was associated with higher BSID-III cognitive scores (+ 3.2 points [IQR 0.02, 6.4]) while in-hospital GF was not associated with any outcomes. Infants with weight GF after discharge had lower BSID-III motor scores (-3.1 points [-5.9, -0.2]). Infants with accelerated weight growth after discharge had increased odds of behavioral problems on the CBCL (aOR 1.9 [1.03, 3.5]). Discussion: In-hospital and post-hospitalization growth metrics are modestly associated with neurodevelopmental outcomes with length gains apparently most beneficial.

An Alternative Oat-Containing, Ready-To-Use, Therapeutic Food Does Not Alter Intestinal Permeability or the 16S Ribosomal RNA Fecal Microbiome Configuration Among Children With Severe Malnutrition in Sierra Leone: A Randomized Controlled Trial.

BACKGROUND: Previously, a novel oat ready-to-use therapeutic food (o-RUTF) resulted in improved recovery from severe acute malnutrition (SAM) when compared to a standard RUTF (s-RUTF). The o-RUTF contained 18% oat, while the s-RUTF has no cereal ingredients. OBJECTIVES: We determined the effects of o-RUTF on intestinal permeability, as measured by lactulose permeability, and the 16S ribosomal RNA (rRNA) fecal microbiome configuration of children with SAM. METHODS: This was a prospective, randomized, double-blinded, controlled clinical trial. Sierra Leonean children aged 6-59 mo with SAM, defined by a midupper arm circumference < 11.5 cm, were randomized to receive o-RUTF or s-RUTF. All children received 7 d of amoxicillin per guidelines. Lactulose permeability testing and fecal 16S rRNA sequencing were performed at baseline and after 4 wk of therapy. The change in lactulose permeability was the primary outcome, while the fecal 16S rRNA configuration at 4 wk was a secondary outcome. RESULTS: Of the 129 children enrolled, lactulose permeability testing was completed by 100 at baseline and 82 at week 4. After 4 wk of therapeutic feeding, there were no differences in lactulose permeability between the o-RUTF and s-RUTF groups (P = 0.84), and over half of children had increased lactulose permeability (50% s-RUTF compared with 58% o-RUTF, mean difference = -7.5%; 95% CI: -29.2, 15.2; P = 0.50). After 4 wk of feeding, there were no differences in the 16S rRNA configurations between the o-RUTF and s-RUTF groups (Permanova, 999 permutations; P = 0.648; pseudo-F = 0.581), nor were there differences in α or ß diversity. CONCLUSIONS: Despite remarkably different compositions of o-RUTF and s-RUTF, no differences were identified in lactulose permeability or the fecal 16S rRNA configuration among children with SAM receiving these foods. These results suggest that the o-RUTF exerts its beneficial effects through mechanisms other than reducing intestinal permeability or altering the fecal 16S configuration. This trial was registered at clinicaltrials.gov as NCT04334538.

Newborn Mid-Upper Arm Circumference Identifies Low-Birth Weight and Vulnerable Infants: A Secondary Analysis.

Background: Low birth weight (LBW) infants are at increased risk of morbidity and mortality. Identification of LBW may not occur in settings where access to reliable scales is limited. Mid-upper arm circumference (MUAC) may be an accessible, low-cost measure to identify LBW and vulnerable infants. Objectives: We explored the validity of newborn MUAC in identifying LBW and vulnerable newborns in rural Sierra Leone. Methods: This study was a secondary analysis of infant data from a randomized controlled clinical trial of supplementary food and anti-infective therapies compared with standard care for undernourished pregnant women. Data for singleton liveborn infants with birth measurement and 6-mo survival data were included in this analysis. The primary outcome was validity of MUAC in identifying low-birth weight (LBW) neonates. Secondary outcomes included validity of MUAC and head circumference (HC) in identifying weight-for-length z-score (WLZ) <-2, length-for-age z-score (LAZ) <-2, neonatal mortality, and mortality within the first 6 mo of life. Results: The study population included 1167 infants, 229 (19.6%) with LBW. Birth MUAC (r = 0.817) and HC (r = 0.752) were highly correlated with birth weight. MUAC (AUC: 0.905; 95% CI: 0.884, 0.925) performed superiorly to HC (AUC: 0.88; 95% CI: 0.856, 0.904) in identifying LBW. The MUAC for identifying LBW was 9.6 cm (sensitivity: 0.86; specificity: 0.78). Neither MUAC nor HC reliably identified newborns with WLZ <-2 or LAZ <-2. MUAC ≤9.0 cm was the ideal cutoff for neonatal mortality (sensitivity: 53.3%; specificity: 89.7%; HR: 9.57; 95% CI: 1.86, 49.30). Birth anthropometrics did not reliably identify infants at risk of death in the first 6 mo of life. Conclusions: MUAC was used successfully to identify LBW infants and infants at risk of neonatal mortality in Sierra Leone. Further evidence is needed to support increased use of newborn MUAC measurement to identify LBW infants and infants at risk of neonatal mortality in community settings where scales are not available. Primary trial was registered at clinicaltrials.gov as NCT03079388. Lay Summary: Mid-upper arm circumference (MUAC) can be used to identify infants with low birth weight and infants at risk for neonatal mortality, with an MUAC ≤9.0 cm indicating the highest risk.

Assessing infant cognition in field settings using eye-tracking: a pilot cohort trial in Sierra Leone.

OBJECTIVES: To investigate the feasibility of eye-tracking-based testing of the speed of visual orienting in malnourished young children at rural clinics in Sierra Leone. DESIGN: Prospective dual cohort study nested in a cluster-randomised trial. SETTING: 8 sites participating in a cluster-randomised trial of supplementary feeding for moderate acute malnutrition (MAM). PARTICIPANTS: For the MAM cohort, all infants aged 7-11 months at the eight sites were enrolled, 138 altogether. For controls, a convenience sample of all non-malnourished infants aged 7-11 months at the same sites were eligible, 60 altogether. A sample of 30 adults at the sites also underwent eye-tracking tests as a further control. INTERVENTIONS: Infants with MAM were provided with supplementary feeding. OUTCOME MEASURES: The primary outcomes were feasibility and reliability of eye-tracking-based testing of saccadic reaction time (SRT). Feasibility was assessed by the percent of successful tests in the infants. Reliability was measured with intraclass correlation coefficients (ICCs). Secondary outcomes were mean SRT based on nutritional state as well as and changes in mean SRT after supplementary feeding of MAM children. RESULTS: Infants exhibited consistent orienting to targets on a computer screen (>95% of valid trials). Mean SRTs had moderate stability within visits (ICCs 0.60-0.69) and across the 4-week test-retest interval (0.53) in infants; the adult control group had greater SRT stability (within visit ICC=0.92). MAM infants had a trend toward higher adjusted SRT at baseline (difference=12.4 ms, 95% CI -2 to 26.9, p=0.09) and improvement in SRT 4 weeks thereafter (difference=-14 ms, 95% CI -26.2 to -1.7, p=0.025) compared with age-matched controls. CONCLUSIONS: The results demonstrate the feasibility of eye-tracking-based testing in a resource-poor field setting and suggest eye-tracking measures have utility in the detection of group level effects of supplementary feeding.

An Optimized Dose of Therapeutic Feeding Results in Noninferior Growth in Midupper Arm Circumference Compared with a Standard Dose in Children in Sierra Leone Recovering from Acute Malnutrition.

BACKGROUND: Ready-to-use therapeutic food (RUTF) given at 175 kcal/kg per day throughout severe acute malnutrition (SAM) treatment is recommended. Some treatment programs have diverged from this paradigm in 2 ways: reducing the supplemental food dose to 75 kcal/kg per day when midupper arm circumference (MUAC) is >11.4 cm or simplifying to a fixed-dose regimen. OBJECTIVE: The objective was to determine if transitioning to an optimized, fixed-dose supplementary feeding regimen during SAM treatment when MUAC is >11.4 cm would result in noninferior gain in MUAC compared with standard treatment. METHODS: Using data from 2 clinical trials conducted in Sierra Leone, a retrospective dual-cohort study was performed. The 2 cohorts included children with SAM who had improved to meet criteria for moderate acute malnutrition (MAM). The standard dose cohort continued to receive weight-based RUTF at 175 kcal/kg per day, while the optimized dose cohort received fixed-dose, 500 kcal/d of supplementary feeding. The primary outcome was a noninferiority margin of 1 mm of MUAC after 4 wk of treatment, while secondary outcomes included rate of anthropometric changes as well as time-to-relapse to SAM or death. RESULTS: MUAC after 4 wk was noninferior (Δ: -0.1 mm; 95% CI: -0.05, 0.03; inferiority rejected P = 0.008). Rates of weight gain and MUAC gain were the same in the optimized-dose and standard-dose groups, whereas the rate of length gain was slower in the optimized-dose cohort. Time-to-relapse to SAM or death was not different (HR: 1.05; P = 0.71). CONCLUSIONS: This study supports the practice of treating children with SAM who have recovered to meet criteria for MAM with a reduced and fixed-dose regimen of RUTF. The results also raise the question of whether this strategy might adversely impact linear growth during SAM treatment.

Association of Intrapartum Risk Factors and Infant Clinical Indicators with Culture Confirmed Early Onset Neonatal Sepsis in a Secondary Care Rural Hospital in India.

OBJECTIVE: The aim of this study is to determine the association of intrapartum risk factors and infant clinical indicators using the National Institute for Health and Care Excellence (NICE) criteria with culture-positive early-onset neonatal sepsis (EONS) from a rural secondary healthcare facility where intrapartum prophylactic antibiotics are routinely administered to high-risk mothers. METHODS: A single-center prospective observational study was conducted between July 2017 and September 2018. All intramural neonates with at least one NICE criteria at less than 72 h of life, were included. Univariate logistic regression and multivariable logistic backward elimination analyses were conducted to investigate individual risk factors and predictive models for culture proven EONS. RESULTS: Of 236 newborns who were at risk for EONS by NICE criteria, 32 (13.8%) had positive blood cultures. Klebsiella species (n = 13, 39.4%) and Acinetobacter species (n = 11, 33.3%) were the most common isolated bacteria. In univariate analysis, the number of infant clinical indicators were associated with culture positive EONS (OR 1.36; 95% CI 1.01-1.81), but not the number of intrapartum risk factors (OR 0.76; 95% CI 0.4-1.29). The multivariate logistic regression with backward elimination procedure suggested that a model including absolute neutrophil count [adjusted OR (aOR) 0.81; 95% CI 0.72-0.92], C-reactive protein (aOR 1.24; 95% CI 1.08-1.43) and the number of clinical indicators (aOR 1.29; 95% CI 0.93-1.80) could be useful to predict culture positive EONS in our setting. CONCLUSION: In this maternal and neonatal cohort, infant clinical indicators rather than intrapartum risk factors were associated with culture confirmed EONS.

Development of Acute Malnutrition Despite Nutritional Supplementation in Malawi.

Malnutrition in children is most often attributed to inadequate nutrient intake. Utilizing data from 2 prospective, randomized controlled trials of complimentary feeding with supplemental legumes (n = 693, ages 6-24 months) in 2 Malawian villages, Masenjere, and Limera, we document a high rate 70/693 (10.1%) of acute malnutrition (AM). Risks for AM in this setting, as determined by Cox regression analysis, include study village (hazard ratio [HR] 3.0), prior malnutrition (HR 4.12), stunting (HR 2.87), and a marker of food insecurity (HR 1.89). Comparison of Masenjere to Limera demonstrate adequate and similar nutritional intake yet an increased rate of AM in Masenjere, 56 of 400 (14.0%) versus 14 of 293 (4.8%), and stunting, 140 of 400 (35%) versus 80 of 293 (27%), environmental enteric dysfunction 246 of 400 (71%) versus 181/293 (67%), and infectious symptoms (cough and diarrhea). Masenjere did have cleaner water and less food insecurity 200 of 399 (50.5%) versus 204 of 293 (69.6%). These findings suggest adequate complementary nutrient intake does not protect young children against AM.

Use of a novel supplementary food and measures to control inflammation in malnourished pregnant women in Sierra Leone to improve birth outcomes: study protocol for a prospective, randomized, controlled clinical effectiveness trial.

BACKGROUND: The negative synergy between poor nutritional status and infectious diseases is doubly detrimental in pregnancy. In Sierra Leone, maternal malnutrition is amongst the highest in the world, while maternal mortality is high at 1320/100,000 live births and stunting in under-five is 37.9%, ranked 110/132 worldwide. Maternal malnutrition has been associated with preterm birth, small-for-gestational age infants, and poor maternal outcomes. Infants born prematurely or small-for-gestational age experience higher mortality and are at risk for stunting and decreased cognitive performance. Nutritional interventions alone during pregnancy may not be as effective in the setting of increased inflammation from repeated infections. Interventions are needed to improve maternal outcomes and reduce stunting in this population. METHODS/DESIGN: This will be a prospective, randomized, controlled clinical effectiveness trial of an improved supplementary food plus anti-infective therapies compared to standard therapy in malnourished pregnant women. Pregnant women will be randomized to receive a low water activity, ready-to-use supplementary food plus five anti-infective interventions or the standard of care which is 3.5 kg corn/ soy blended flour with 350 mL vegetable oil every two weeks. The five anti-infective interventions are 1) insecticide-treated mosquito net at the time of enrollment into the study, 2) sulfadoxine-pyrimethamine given every 4 weeks, beginning at enrollment or at 13 weeks' gestation, whichever is later, 3)azithromycin at a dose of 1 g given once at enrollment (after first trimester)and again during 28-34 weeks of gestation, 4)single dose 400 mg albendazole given in second trimester, and 5) testing and treatment for bacterial vaginosis at enrollment and again at 28-34 weeks of gestation. Treatment will be provided for the duration of the pregnancy. The primary outcome measure will be birth length. Secondary outcomes in the mothers will include rates of maternal weight gain and increase in mid-upper arm circumference, and time to maternal anthropometric recovery. Secondary outcomes in the infants will include birth weight, birth head circumference, and linear and ponderal growth. DISCUSSION: Malnutrition remains a major problem in the developing world with lasting maternal and infant consequences. Maternal malnutrition has been associated with intrauterine growth retardation, low birth weight (LBW), pre-term delivery and poor cognitive development. Nutritional interventions alone have not been successful in reducing stunting. By bundling nutritional and anti-infective interventions, we aim to reduce intrauterine growth restriction and low birth weight in moderately malnourished pregnant women in Sierra Leone. If successful, this bundle can easily be implemented by governments or non-governmental organizations. TRIAL REGISTRATION: Clinicaltrials.gov NCT03079388; Date: March 5, 2017.

Human milk lactoferrin is a serine protease that cleaves Haemophilus surface proteins at arginine-rich sites.

Lactoferrin is a member of the lactotransferrin family of non-haem, iron-binding glycoproteins and is found at high concentrations in all human secretions, where it plays a major role in mucosal defence. In recent work, we observed that lactoferrin has proteolytic activity and attenuates the pathogenic potential of Haemophilus influenzae by cleaving and removing two putative colonization factors, namely the IgA1 protease protein and the Hap adhesin. Experiments with protease inhibitors further suggested that lactoferrin may belong to a serine protease family. In the present study we explored the mechanism of lactoferrin protease activity and discovered that mutation of either Ser259 or Lys73 results in a dramatic decrease in proteolysis. Examination of the crystal structure revealed that these two residues are located in the N-terminal lobe of the protein, adjacent to a 12-15 A cleft that separates the N-lobe and the C-lobe and that can readily accommodate large polypeptide substrates. In additional work, we found that lactoferrin cleaves IgA1 protease at an arginine-rich region defined by amino acids 1379-1386 (RRSRRSVR) and digests Hap at an arginine-rich sequence between amino acids 1016 and 1023 (VRSRRAAR). Based on our results, we conclude that lactoferrin is a serine protease capable of cleaving arginine-rich sequences. We speculate that Ser259 and Lys73 form a catalytic dyad, reminiscent of a number of bacterial serine proteases. In addition, we speculate that lactoferrin may cleave arginine-rich sequences in a variety of microbial virulence proteins, contributing to its long-recognized antimicrobial properties.

Transposon mutagenesis of Campylobacter jejuni identifies a bipartite energy taxis system required for motility.

Campylobacter jejuni constitutes the leading cause of bacterial gastroenteritis in the United States and a major cause of diarrhoea worldwide. Little is known about virulence mechanisms in this organism because of the scarcity of suitable genetic tools. We have developed an efficient system of in vitro transposon mutagenesis using a mariner-based transposon and purified mariner transposase. Through in vitro transposition of C. jejuni chromosomal DNA followed by natural transformation of the transposed DNA, large random transposon mutant libraries consisting of approximately 16 000 individual mutants were generated. The first genetic screen of C. jejuni using a transposon-generated mutant library identified 28 mutants defective for flagellar motility, one of the few known virulence determinants of this pathogen. We developed a second genetic system, which allows for the construction of defined chromosomal deletions in C. jejuni, and demonstrated the requirement of sigma28 and sigma54 for motility. In addition, we show that sigma28 is involved in the transcription of flaA and that sigma54 is required for transcription of three other flagellar genes, flaB and flgDE. We also identified two previously uncharacterized genes required for motility encoding proteins that we call CetA and CetB, which mediate energy taxis responses. Through our analysis of the Cet proteins, we propose a unique mechanism for sensing energy levels and mediating energy taxis in C. jejuni.

Secretion of virulence determinants by the general secretory pathway in gram-negative pathogens: an evolving story.

Secretion of proteins by the general secretory pathway (GSP) is a two-step process requiring the Sec translocase in the inner membrane and a separate substrate-specific secretion apparatus for translocation across the outer membrane. Gram-negative bacteria with pathogenic potential use the GSP to deliver virulence factors into the extracellular environment for interaction with the host. Well-studied examples of virulence determinants using the GSP for secretion include extracellular toxins, pili, curli, autotransporters, and crystaline S-layers. This article reviews our current understanding of the GSP and discusses examples of terminal branches of the GSP which are utilized by factors implicated in bacterial virulence.

Molecular determinants of the pathogenesis of disease due to non-typable Haemophilus influenzae.

Non-typable Haemophilus influenzae is a common commensal organism in the human upper respiratory tract and an important cause of localized respiratory tract disease. The pathogenesis of disease begins with bacterial colonization of the nasopharynx, a process that involves establishment on the mucosal surface and evasion of local immune mechanisms. Under the proper circumstances, the organism spreads contiguously to the middle ear, the sinuses, or the lungs, and then stimulates a brisk inflammatory response, producing symptomatic infection. In this review, we summarize our present understanding of the molecular determinants of this sequence of events. Continued investigation of the molecular mechanism of non-typable H. influenzae pathogenicity should facilitate development of novel approaches to the treatment and prevention of H. influenzae disease.

Human milk lactoferrin inactivates two putative colonization factors expressed by Haemophilus influenzae.

Haemophilus influenzae is a major cause of otitis media and other respiratory tract disease in children. The pathogenesis of disease begins with colonization of the upper respiratory mucosa, a process that involves evasion of local immune mechanisms and adherence to epithelial cells. Several studies have demonstrated that human milk is protective against H. influenzae colonization and disease. In the present study, we examined the effect of human milk on the H. influenzae IgA1 protease and Hap adhesin, two autotransported proteins that are presumed to facilitate colonization. Our results demonstrated that human milk lactoferrin efficiently extracted the IgA1 protease preprotein from the bacterial outer membrane. In addition, lactoferrin specifically degraded the Hap adhesin and abolished Hap-mediated adherence. Extraction of IgA1 protease and degradation of Hap were localized to the N-lobe of the bilobed lactoferrin molecule and were inhibited by serine protease inhibitors, suggesting that the lactoferrin N-lobe may contain serine protease activity. Additional experiments revealed no effect of lactoferrin on the H. influenzae P2, P5, and P6 outer-membrane proteins, which are distinguished from IgA1 protease and Hap by the lack of an N-terminal passenger domain or an extracellular linker region. These results suggest that human milk lactoferrin may attenuate the pathogenic potential of H. influenzae by selectively inactivating IgA1 protease and Hap, thereby interfering with colonization. Future studies should examine the therapeutic potential of lactoferrin, perhaps as a supplement in infant formulas.

The Haemophilus influenzae Hap serine protease promotes adherence and microcolony formation, potentiated by a soluble host protein.

Haemophilus influenzae initiates infection by colonizing the upper respiratory mucosa. The process of colonization involves adherence to epithelium and evasion of host immunity. In this study, we examined the H. influenzae Hap adhesin, which has serine protease activity and undergoes autoproteolytic cleavage and extracellular release in broth. We found that the uncleaved cell-associated form of Hap mediates adherence to cultured epithelial cells and promotes bacterial aggregation and microcolony formation. Adherence and aggregation are augmented by secretory leukocyte protease inhibitor, a natural component of respiratory secretions that inhibits Hap autoproteolysis. These observations suggest a novel paradigm in host-pathogen relations, in which a soluble host protein whose primary function is to protect host epithelium potentiates properties that facilitate bacterial colonization.