Abstract CT026: The effect of intrinsic subtype on inhibition of tumor growth by anastrozole vs. fulvestrant vs. the combination: Results from the Alliance neoadjuvant endocrine therapy (NET) ALTERNATE trial

Introduction: The ALTERNATE trial randomized postmenopausal women with ER Allred 6-8 HER2- breast cancer to 6 months of NET with anastrozole (A), fulvestrant (F) or the combination (A+F). Biopsies were taken preNET and after 4-weeks(wks). Patients with Ki67 values >10% at 4-wks were offered triage to neoadjuvant chemotherapy. Patients with on-treatment Ki67 ≤ 10% who completed NET underwent surgery and Ki67 was reassessed. The primary endpoint was endocrine-sensitive disease rate (ESDR). ESD is defined as pCR or PEPI-0 residual disease (pT1-2, pN0, Ki67 ≤ 2.7%). We previously reported that the ESDR difference between the F-containing arms and the A arm was not >10% (ASCO 2020) and that baseline RNA-seq-based intrinsic subtypes predicted outcomes overall (SABCS 2021). Herein we describe relationships between PAM50 intrinsic subtype and Ki67 values by treatment arm because comparative drug effectiveness in adjuvant endocrine therapy studies in ER+ HER2- breast cancer can be predicted by the degree of Ki67 suppression (PMC3518447).

Methods: 743 of the 1297 eligible patients (A: 264; F: 231; A+F: 248) had RNA extracted from preNET frozen tumor biopsies with >50% tumor content and subjected to RNA seq. Intrinsic subtypes were then assigned as LumA, LumB, and NonLum (Basal or HER2-E) using open-source PAM50-based informatics. Differences in the proportion with wk4 Ki67 > 10%, % change in wk4 ki67, and surgical CCCA (Ki67 ≤ 2.7%) rate (sxCCCA) between treatments and by intrinsic subtype was assessed using stratified logistic regression, Wilcoxon rank sum test, and Fisher’s exact test, respectively. Analysis of sxCCCA excluded those who failed to complete NET for reasons other than disease progression or early Ki67 >10%.

Results: Amongst the 358 LumA cases there were no significant differences in Ki67-based endpoints between treatments. Among the 292 LumB cases, the wk4 ki67 > 10% rate was lower with A+F (19.4%) than A (43%) (P=0.0002) and was somewhat lower in F (31%) versus A (P=0.076). The % change in wk4 Ki67 in LumB cases, adjusted for baseline Ki67, showed markedly superior suppression for A+F versus A (-90% vs. -77%; P=<0.0001) and versus F (-90% vs. -80%; P=0.0026). Furthermore sxCCCA rates were significantly higher with A+F than A (53% vs. 25% P = <0.0001) and somewhat higher for F (37%) than A (p=0.068), indicating that superior antiproliferative effects for A+F persist after 6 months on therapy. Lack of Ki67 suppression in response to treatment was observed in the majority of 43 NonLum samples regardless of treatment.

Conclusion: The combination of A+F was significantly more effective than either drug alone for the control of LumB breast cancer cell proliferation. This suggests that A+F may be a more effective adjuvant endocrine therapy than A alone in LumB disease. The lower Ki67 suppression with A alone also suggests that poorer outcome in some LumB tumors may be due to insufficient ER targeting rather than ER-independent tumor growth

Support: U10CA180821, U10CA180882, U24CA196171, UG1CA189856, U10CA180868 (NRG), NCI BIQSFP, BCRF, Genentech, AstraZeneca. https://acknowledgments.alliancefound.org. (MJE) CPRIT RR140033, P50-CA186784, P50-CA58223, U01-CA214125, U24-CA210954, Gift from Ralph and Lisa Eads, McNair Scholarship.

ClinicalTrials.gov Identifier: NCT01953588

Citation Format: Matthew J. Ellis, Meenakshi Anurag, Jeremy Hoog, Aranzazu Fernandez-Martinez, Cheng Fan, Richard Gibbs, Souzan Sanati, Kiran Vij, Mark Watson, Travis Dockter, Olwen Hahn, Joseph Guenther, Abigail Caudle, Erica Crouch, Amy Tiersten, Monica Mita, Wajeeha Razaq, Tina J. Hieken, Yang Wang, A. Marilyn Leitch, Gary W. Unzeitig, Eric Winer, Anna Weiss, Kelly Hunt, Ann H. Partridge, Charles M. Perou, Vera Suman, Cynthia X. Ma, Lisa A. Carey. The effect of intrinsic subtype on inhibition of tumor growth by anastrozole vs. fulvestrant vs. the combination: Results from the Alliance neoadjuvant endocrine therapy (NET) ALTERNATE trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT026.

COVID-19: Seroprevalence and Vaccine Responses in UK Dental Care Professionals

Dental care professionals (DCPs) are thought to be at enhanced risk of occupational exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, robust data to support this from large-scale seroepidemiological studies are lacking. We report a longitudinal seroprevalence analysis of antibodies to SARS-CoV-2 spike glycoprotein, with baseline sampling prior to large-scale practice reopening in July 2020 and follow-up postimplementation of new public health guidance on infection prevention control (IPC) and enhanced personal protective equipment (PPE). In total, 1,507 West Midlands DCPs were recruited into this study in June 2020. Baseline seroprevalence was determined using a combined IgGAM enzyme-linked immunosorbent assay and the cohort followed longitudinally for 6 mo until January/February 2021 through the second wave of the coronavirus disease 2019 pandemic in the United Kingdom and vaccination commencement. Baseline seroprevalence was 16.3%, compared to estimates in the regional population of 6% to 7%. Seropositivity was retained in over 70% of participants at 3- and 6-mo follow-up and conferred a 75% reduced risk of infection. Nonwhite ethnicity and living in areas of greater deprivation were associated with increased baseline seroprevalence. During follow-up, no polymerase chain reaction-proven infections occurred in individuals with a baseline anti-SARS-CoV-2 IgG level greater than 147.6 IU/ml with respect to the World Health Organization international standard 20-136. After vaccination, antibody responses were more rapid and of higher magnitude in those individuals who were seropositive at baseline. Natural infection with SARS-CoV-2 prior to enhanced PPE was significantly higher in DCPs than the regional population. Natural infection leads to a serological response that remains detectable in over 70% of individuals 6 mo after initial sampling and 9 mo from the peak of the first wave of the pandemic. This response is associated with protection from future infection. Even if serological responses wane, a single dose of the Pfizer-BioNTech 162b vaccine is associated with an antibody response indicative of immunological memory.

Examining the association between adverse childhood experiences and smoking-exacerbated illnesses

OBJECTIVES

Adults who smoke increase their likelihood of death from smoking-exacerbated illnesses. The presence of illnesses exacerbated by smoking can be a powerful incentive to quit smoking. However, having a smoking-exacerbated illness does not stop all patients from smoking. Understanding that smoking may be a coping mechanism for stress, this study examined the association between the experiences of adverse events in childhood with continued smoking in adulthood among individuals and a smoking-exacerbated illness.

STUDY DESIGN

This retrospective observational study used 2014-2015 data from the South Carolina Behavioral Risk Factor Surveillance System survey.

METHODS

We used multivariable logistic regression to examine the impact of adverse childhood experience (ACE) exposure on current smoking status.

RESULTS

A total of 6321 respondents reported having a smoking-exacerbated illness. The most frequently reported categories of smoking-exacerbated illnesses were current asthma (63.9%), previous asthma (13.0%), and diabetes (12.3%). Overall, 62.4% of respondents had at least one ACE, with 20.3% of respondents having four or more ACEs. Respondents with one to three ACEs (adjusted odds ratio [aOR] 1.38; 95% confidence interval [CI] 1.37-1.40) and four or more ACEs (aOR 2.89; CI 2.86-2.92) were both significantly more likely to smoke than respondents with no ACEs, even in the presence of illnesses exacerbated by smoking.

CONCLUSIONS

Results suggest that ACE exposure may influence risky health behaviors in adulthood, such as continued smoking even in the presence of illnesses that are exacerbated by smoking. Given that smoking has been found to be a coping mechanism for adversity, anti-smoking efforts might benefit from designing interventions and treatment plans that address ACE exposure.

Abstract OT2-6-12: A randomized pacebo-controlled phase II trial evaluating the effect of hedgehog inhibitor LDE225 on bone marrow disseminated tumor cells in women with early stage estrogen receptor negative and HER2 negative breast cancer

Background: 20% of invasive breast cancers are triple negative (TN). Chemotherapy improves the outcome for a subset of these patients. Recurrence rates of 40-50% have been reported in those patients who do not achieve a complete pathological response to neoadjuvant therapy. Currently, there are no targeted therapies to TN cancers. Data suggest that micrometastases or disseminated tumor cells (DTCs) that persist despite chemotherapy are enriched with cells that have stem cell-like features. The Hedgehog (Hh) signaling pathway, which is involved in modulating epithelial-mesenchymal transition and maintenance of breast cancer stem cells, is an attractive therapeutic target for patients with TN tumors. In preclinical models, we have shown that Hh inhibition reduced breast cancer growth and metastasis.

Trial Design: This is a placebo-controlled, double blinded, randomized phase II trial in early stage TN breast cancer patients with detectable DTCs in their bone marrow (BM) at the completion of all therapy. LDE225 is administered at 400 mg orally daily for a 28 day cycle for 20 cycles. After 6 cycles, BM will be collected for analysis.

Specific Aims: The primary endpoint is the elimination of DTCs after 6 cycles of LDE225. Additional endpoints include: 2-year disease-free survival (DFS) and overall survival (OS), effect on BM Ptch1 gene expression, toxicity profile of LDE225, DFS and OS in patients with no DTCs at screening versus DTC-positive patients in the placebo arm.

Eligibility: Patients with ER-/Her2- stage I-III invasive breast cancers who have completed all therapy and have detectable DTCs, as defined by a molecular based assay for DTCs performed in a CLIA-licensed facility are eligible.

Statistical Methods: Based on preliminary data, 60% of patients in the LDE225 arm are expected to be Ptch1 positive, and 50% of these patients are expected eliminate DTCs after 6 cycles of treatment. The expected clearance rate in the remaining 40% of the LDE225 arm is 5% with an overall clearance rate of 32%. In the placebo arm, the expected clearance rate is 5% regardless of Ptch1 status. A sample of 68 patients, 34 in each treatment arm, will have power ∼ 0.8 at a 0.05 significance level, after adjusting for one interim analysis, to detect a difference in DTC clearance rate of 32% in the LDE225 arm versus 5% in the placebo arm. Assuming that 40% of patients screened have detectable DTCs, approximately 170 patients will be screened to identify 68 with detectable DTCs.

Enrollment will be suspended for 3 months after the first 6 patients have been randomized to LDE225 therapy to allow time to document toxicity and adverse events. One interim analysis will be conducted after 50% of the patients have completed 6 months on study. The proportion of patients who are DTC-positive at 6 months will be estimated. The power of the study power to achieve its primary goal will be calculated conditional on results obtained to that point. The significance level of the final analysis will be adjusted to 0.048 in order to maintain an overall 0.05 significance level.

Accrual: Accrual is anticipated to begin August 2013. Target = 34 per arm. NCT01757327.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT2-6-12.

Activity of DNA polymerase alpha in aging human fibroblasts

During the past decade intense investigation has focused on cellular aging with the expectation of discovering factors that regulate the replication complex and contribute to the onset and progression of cellular aging. The most striking feature of cellular aging is the failure of sensing diploid cells to enter or complete S phase of the cell cycle. The G1/S phase transition is an initial critical step in the regulation of proliferation in eukaryotic cells, and significant advances have been made toward understanding the basic mechanisms of aging by identifying components of the macromolecular assemblies participating in the G1/S transition. These studies have identified multiple DNA polymerases and their accessory factors, and have provided important strategies for investigating the molecular events that contribute to aging processes. DNA replication, repair and recombination in eukaryotic cells require the action of a variety of DNA polymerases, at least six of which are known, alpha, beta, gamma, delta, epsilon, and zeta. Among them the highly conserved DNA polymerase alpha-primase (pol alpha-primase) is the only enzyme capable of initiating DNA replication at chromosomal origin sites and at sites of initiation of discontinuous synthesis of Okazaki fragments on the lagging side of the replication fork. Numerous protein factors that play strategic roles in DNA replication have been identified and the understanding of their regulation has been an important step for identifying the elements that are involved in, and possibly necessary for, governing cellular senescence and aging. In this review we summarize the current information regarding DNA pol alpha modulation during aging. We focus in particular on the coordinated actions of DNA pol alpha in the presence of other cellular proteins involved in the replication complex in the hope that understanding pol alpha interactions with components of the replication complex may provide insight into the mechanisms by which aging and age-related diseases occur.

Retinoblastoma protein complexes with C/EBP proteins and activates C/EBP-mediated transcription

The retinoblastoma protein (RB) recruits histone deacetylase (HDAC) to repress E2F-mediated transactivation that plays a critical role in cell cycle regulation. RB is also involved in activation of expression of a number of tissue specific- and differentiation-related genes. In this study, we examined the mechanism by which RB stimulated the expression of a differentiation-related gene, the surfactant protein D (SP-D), which plays important roles in innate host defense and the regulation of surfactant homeostasis. We demonstrated that RB specifically stimulated the activity of human SP-D gene promoter. The RB family member, p107 but not p130, also increased SP-D promoter activity. Activation by RB was mediated through a NF-IL6 (C/EBP beta) binding motif in the human SP-D promoter, and this sequence specifically bound to C/EBP alpha, C/EBP beta, and C/EBP delta. RB formed stable complexes with all three C/EBP family members. RB small pocket (amino acid residues 379-792), but not the C-pocket (amino acid residues 792-928), was necessary and sufficient for its interaction with C/EBP proteins. Furthermore, we demonstrated that the complexes containing RB and C/EBP proteins directly interacted with C-EBP binding site on DNA. These findings indicate that RB plays a positive, selective, and direct role in the C/EBP-dependent transcriptional regulation of human SP-D expression.

Increased antiviral and opsonic activity of a highly multimerized collectin chimera

Altering the carbohydrate binding properties of surfactant protein D (SP-D) [e.g., by replacing its carbohydrate recognition domain (CRD) with that of either mannose binding lectin (MBL) or conglutinin] can increase its activity against influenza A virus (IAV). The current study demonstrates that the degree of multimerization of SP-D is another independent determinant of antiviral activity. A chimeric collectin containing the N-terminus and collagen domain of human SP-D and the CRD of MBL formed high-molecular-weight multimers similar to those previously described for human SP-D. Using several complementary assays, and diverse viral strains, the chimeric multimers showed greater anti-IAV activity than similarly multimerized preparations of SP-D or incompletely oligomerized preparations of the chimera. More highly multimerized preparations of the chimera also caused greater increases in uptake of IAV by neutrophils. These studies may have implications for development of collectins as therapeutic agents and understanding of natural variations in susceptibility to IAV infection.

Surfactant protein D-coated Klebsiella pneumoniae stimulates cytokine production in mononuclear phagocytes

Encapsulated Klebsiella pneumoniae strains K21a, K10, and K50, all of which contain dimannose sequences in their capsular polysaccharides that are recognized by the mannose receptor of macrophages, stimulated interleukin secretion and cytokine mRNA expression by human monocyte-derived macrophages. By contrast, the corresponding unencapsulated phase variants and the K2 strain, which lack the dimannose sequence, did not. Coating of unencapsulated phase variants of Klebsiella strains with surfactant protein (SP)-D resulted in marked stimulation of cytokine mRNA accumulation. The induction of cytokine mRNA via the mannose receptor occurred only in monocyte-derived macrophages, whereas that caused by SP-D-coated Klebsiella strains occurred in both macrophages and peripheral-blood monocytes. The results suggested that innate immunity against pulmonary pathogens might be mediated by SP-D, which acts as an opsonin to enhance the interaction of macrophages with unencapsulated phase variants originating from the upper respiratory tract, and by macrophage mannose receptors, which recognize encapsulated variants expressing capsular dimannose residues.

Surfactant proteins a and d and pulmonary host defense

The lung collectins, SP-A and SP-D, are important components of the innate immune response to microbial challenge and participate in other aspects of immune and inflammatory regulation within the lung. Both proteins bind to surface structures expressed by a wide variety of microorganisms and have the capacity to modulate multiple leukocyte functions, including the enhanced internalization and killing of certain microorganisms in vitro. In addition, transgenic mice with deficiencies in SP-A and SP-D show defective or altered responses to challenge with bacterial, fungal, and viral microorganisms and to bacterial lipopolysaccharides in vivo. Thus collectins could play particularly important roles in settings of inadequate or impaired specific immunity, and acquired alterations in the levels of active collectins within the airspaces and distal airways may increase susceptibility to infection.

The amino-terminal heptad repeats of the coiled-coil neck domain of pulmonary surfactant protein d are necessary for the assembly of trimeric subunits and dodecamers

Pulmonary surfactant protein D (SP-D), a lung host defense protein, is assembled as multimers of trimeric subunits. Trimerization of SP-D monomers is required for high affinity saccharide binding, and the oligomerization of trimers is required for many of its functions. A peptide containing the alpha-helical neck region can spontaneously trimerize in vitro. However, it is not known whether this sequence is necessary for the complete cellular assembly of disulfide-cross-linked, trimeric subunits and dodecamers. For the present studies, we synthesized mutant cDNAs with deletions or site-directed substitutions in the neck domain of rat SP-D, and examined the assembly of the newly synthesized proteins after transfection of CHO-K1 cells. The neck domain contains three "classical" heptad repeat motifs with leucine residues at the "d position," and a distinctive C-terminal repeat previously suggested to drive trimeric chain association. Deletion of the highly conserved core of the latter repeat (FSRYLKK) did not interfere with the secretion of dodecamers with lectin activity. By contrast, deletion of the entire neck domain or deletion of one or two amino-terminal repeats resulted in defective molecular assembly. The secreted proteins eluted in the position of monomers by gel filtration under nondenaturing conditions. In addition, the neck + carbohydrate recognition domain of SP-D was necessary and sufficient for the trimerization of a heterologous collagen sequence located amino-terminal to the trimeric coiled-coil. These studies provide strong evidence that the amino-terminal heptad repeats of the neck domain are necessary for the intracellular, trimeric association of SP-D monomers and for the assembly and secretion of functional dodecamers.

Deficiencies in lung surfactant proteins A and D are associated with lung infection in very premature neonatal baboons

Surfactant proteins A (SP-A) and D (SP-D) are important in the innate host defense against pathogenic microorganisms. A deficit in these proteins in premature infants, either because of immaturity or as a consequence of superimposed chronic lung disease (CLD), could increase their susceptibility to infection. The study reported here examined infection in CLD in the premature newborn baboon, and correlated it with the amounts of SP-A and SP-D in lung tissue and lavage fluid. Two groups of baboons were delivered prematurely, at 125 d gestational age (g.a.), and differed principally in whether they developed naturally acquired pulmonary infections and sepsis. Group I animals were ventilated with clinically appropriate oxygen for 6 d and 14 d without clinical incident. Group II animals were ventilated for 5 to 71 d, but differed from those in Group I in that most developed pulmonary infection and/or sepsis. In Group I animals, tissue pools of both SP-A and SP-D were equal to or exceeded those in adults, and lavage pools of SP-A increased progressively with the time of ventilation to about 35% of adult levels after 14 d. In contrast, most Group II animals had concentrations of lavage SP-A that were less than 20% of that in adult animals. A low concentration of lavage SP-A correlated with the release of interleukin-8, and with a high "infection index" based on histopathology, microbiologic cultures, and clinical indications of sepsis. Our data suggest that the amounts of SP-A and SP-D in lavage fluid are indicators of the risk of infection in the evolution of neonatal CLD. Deficits in the amount of lavage SP-A, even after 60 d of ventilation, may have inhibited the resolution of infection and thereby contributed to the developing injury among our Group II animals.

Surfactant protein D enhances phagocytosis and killing of unencapsulated phase variants of Klebsiella pneumoniae

Pulmonary surfactant protein D (SP-D) is a collagenous C-type lectin (collectin) that is secreted into the alveoli and distal airways of the lung. We have studied the interactions of SP-D and alveolar macrophages with Klebsiella pneumoniae, a common cause of nosocomial pneumonia. SP-D does not agglutinate encapsulated K. pneumoniae but selectively agglutinates spontaneous, unencapsulated phase variants, such as Klebsiella strain K50-3OF, through interactions with their lipopolysaccharides (LPS). These effects are calcium dependent and inhibited with maltose but not lactose, consistent with involvement of the SP-D carbohydrate recognition domain. Precoating of K50-3OF with SP-D enhances the phagocytosis and killing of these organisms by rat alveolar macrophages in cell culture and stimulates the production of nitric oxide by the NR-8383 rat alveolar macrophage cell line. SP-D similarly enhances the NO response to K50-3OF LPS adsorbed to Latex beads under conditions where soluble LPS or SP-D, or soluble complexes of SP-D and LPS, do not stimulate NO production. Our studies demonstrate that interactions of SP-D with exposed arrays of Klebsiella LPS on a particulate surface can enhance the host defense activities of alveolar macrophages and suggest that activation of macrophages by SP-D requires binding to microorganisms or other particulate ligands. Because unencapsulated phase variants are likely to be responsible for the initial stages of tissue invasion and infection, we speculate that SP-D-mediated agglutination and/or opsonization of K. pneumoniae is an important defense mechanism for this respiratory pathogen in otherwise healthy individuals.

Enhanced antiviral and opsonic activity of a human mannose-binding lectin and surfactant protein D chimera

The carbohydrate recognition domains (CRDs) of human serum mannose-binding lectin (MBL) and pulmonary surfactant protein D (SP-D) have distinctive monosaccharide-binding properties, and their N-terminal and collagen domains have very different quaternary structures. We produced a chimeric protein containing the N terminus and collagen domain of human SP-D and the neck region and CRD of human MBL (SP-D/MBLneck+CRD) to create a novel human collectin. The chimera bound to influenza A virus (IAV), inhibited IAV hemagglutination activity and infectivity, and induced aggregation of viral particles to a much greater extent than MBL. Furthermore, SP-D/MBLneck+CRD caused much greater increases in neutrophil uptake of, and respiratory burst responses to, IAV than MBL. These results indicate that pathogen interactions mediated by the MBL CRD are strongly influenced by the N-terminal and collagen-domain backbone to which it is attached. The presence of the CRD of MBL in the chimera resulted in altered monosaccharide binding properties compared with SP-D. As a result, the chimera caused greater aggregation and neutralization of IAV than SP-D. Distinctive functional properties of collectin collagenous domains and CRDs can be exploited to generate novel human collectins with potential for therapy of influenza.

Transgenic expression of cyclin D1 in thymic epithelial precursors promotes epithelial and T cell development

We previously reported that precursors within the keratin (K) 8+5+ thymic epithelial cell (TEC) subset generate the major cortical K8+5- TEC population in a process dependent on T lineage commitment. This report demonstrates that expression of a cyclin D1 transgene in K8+5+ TECs expands this subset and promotes TEC and thymocyte development. Cyclin D1 transgene expression is not sufficient to induce TEC differentiation in the absence of T lineage-committed thymocytes because TECs from both hCD3epsilon transgenic and hCD3epsilon/cyclin D1 double transgenic mice remain blocked at the K8+5+ maturation stage. However, enforced cyclin D1 expression does expand the developmental window during which K8+5+ cells can differentiate in response to normal hemopoietic precursors. Thus, enhancement of thymic function may be achieved by manipulating the growth and/or survival of TEC precursors within the K8+5+ subset.

Collectins and pulmonary innate immunity

The surfactant-associated proteins SP-A and SP-D are members of a family of host defense lectins, designated collectins. There is increasing evidence that these pulmonary, epithelial-derived proteins are important components of the innate immune response to microbial challenge and participate in other aspects of immune and inflammatory regulation within the lung. Both proteins bind to glycoconjugates and/or lipid moieties expressed by a wide variety of microorganisms, and to certain organic particles, such as pollens. SP-A and SP-D have the capacity to modulate leukocyte function and, in some circumstances; to opsonize and enhance the killing of microorganisms. The biologic activity of cell wall components, such as Gram-negative bacterial polysaccharides, or viral glycoproteins, such as the hemagglutinin of influenza viruses, may be altered by interactions with collectins. In addition, complementary or cooperative interactions between SP-A, SP-D and other host defense lectins could contribute to the efficiency of this defense system. Collectins could play particularly important roles in settings of inadequate or impaired specific immunity, and acquired alterations in the levels of active collectins within the airspaces and distal airways may increase susceptibility to infection.

Microfibril-associated protein 4 is present in lung washings and binds to the collagen region of lung surfactant protein D

We have purified a glycoprotein from bovine lung washings using affinity chromatography on a maltose-affinity column. On SDS-polyacrylamide gel electrophoresis the protein showed a molecular mass of 36 kDa in the reduced state and 66 kDa in the unreduced state. On gel permeation chromatography the apparent molecular mass was 250 kDa. N-terminal sequencing showed homology to the human matrix protein microfibril-associated protein (hMFAP4), and the glycoprotein was designated bovine MFAP4 (bMFAP4). Lung surfactant protein D (SP-D) was also purified from lung washings, and calcium-dependent binding was demonstrated between bMFAP4 and SP-D. hMFAP4 was cloned, and recombinant hMFAP4 showed the same binding pattern to SP-D as bMFAP4. No binding was seen to recombinant SP-D composed of the neck region and carbohydrate recognition domain of SP-D, indicating that the interaction between MFAP4 and SP-D is mediated via the collagen region of SP-D. MFAP4 also showed calcium-dependent binding to mannan, which was partially inhibited by maltose. Our findings indicate that MFAP4 has two binding specificities, one for collagen and one for carbohydrate, and we suggest that MFAP4 may fix the collectins in the extracellular compartment during inflammation.

Surfactant proteins A and D in premature baboons with chronic lung injury (Bronchopulmonary dysplasia). Evidence for an inhibition of secretion

Surfactant proteins A and D (SP-A and SP-D) are believed to participate in the pulmonary host defense and the response to lung injury. In order to understand the effects of prematurity and lung injury on these proteins, we measured the amounts of SP-A and SP-D and their mRNAs in three groups of animals: (1) nonventilated premature baboon fetuses; (2) neonatal baboons delivered prematurely at 140 d gestation age (ga) and ventilated with PRN O(2); (3) animals of the same age ventilated with 100% O(2) to induce chronic lung injury. In nonventilated fetuses, tissue and lavage SP-A were barely detectable in baboons of 125 and 140 d ga, but they equaled or exceeded adult SP-A concentrations (g/g lung dry wt) at 175 d (term gestation, 185 d). In contrast, SP-D was readily detectable in tissue and lavage at 125 and 140 d ga. When the baboons of 140 d ga were ventilated for 10 d with 100% oxygen to produce chronic lung injury, the tissue concentration of SP-A was five times greater than that of normal adults; SP-D 16-times greater. Despite the sizable tissue pools of SP-A and SP-D, however, lavage SP-A was only 7% of that of normal adults and lavage SP-D just equaled the amount in normal adults. Nevertheless, because SP-D is normally in much lower concentration than is SP-A, their total comprised less than 12% of the SP-A and SP-D found in the lavage of a healthy adult. The results indicate that in chronic lung injury, SP-A is significantly reduced in the alveolar space. SP-D concentration in lavage is about equal to that in normal adults, possibly because of the 16-fold excess in tissue, but the total collectin pool in lavage is still significantly reduced. Because these collectins may bind and opsonize bacteria and viruses, decrements in their amounts may present additional risk to those premature infants who require prolonged periods of ventilatory support.

Influenza A virus accelerates neutrophil apoptosis and markedly potentiates apoptotic effects of bacteria

Neutrophils are recruited into the airway in the early phase of uncomplicated influenza A virus (IAV) infection and during the bacterial superinfections that are a significant cause of morbidity and mortality in IAV-infected subjects. In this report, we show that IAV accelerates neutrophil apoptosis. Unopsonized Escherichia coli had similar effects, although apoptotic effects of opsonized E coli were greater. When neutrophils were treated with both IAV and unopsonized E coli, a marked enhancement of the rate and extent of neutrophil apoptosis occurred as compared with that caused by either pathogen alone. Treatment of neutrophils with IAV markedly increased phagocytosis of E coli. Simultaneous treatment of neutrophils with IAV and E coli also elicited greater hydrogen peroxide production than did either pathogen alone. IAV increased neutrophil expression of Fas antigen and Fas ligand, and it also increased release of Fas ligand into the cell supernatant. These findings may have relevance to the understanding of inflammatory responses to IAV in vivo and of bacterial superinfection of IAV-infected subjects.

Palinopsia with bacterial brain abscess and Noonan syndrome

Though positive visual symptoms can be psychological in nature, or can result from a perceptive or anxious patients recognizing optical principals in the eye itself, this case illustrates how a thorough history is required to delineate those rarer signs which accompany serious macular or neuro-ophthalmic pathology.

Interdependence of cortical thymic epithelial cell differentiation and T-lineage commitment

Thymocyte and thymic epithelial cell (TEC) development are interdependent processes. Although lineage relationships among progressively maturing thymocyte subsets have been characterized, the developmental relationships among TEC subsets are obscure. Because epithelial cells express distinct keratin (K) species as a function of differentiation stage and proliferative status, we used K expression patterns to identify mouse TEC subsets and determine their lineage relationships. As expected, cortical and medullary TEC subsets express distinct K expression patterns in the normal thymus. However, we detected two distinct cortical TEC subsets, a major K8(+)K5(-) subset and a minor K8(+)K5(+) subset, which is highly represented at the cortico-medullary junction. Both cortical TEC subsets are also present in recombination activating gene 1 (RAG-1(-/-)) and TCRbetaxdelta-/- thymi in which T-cell development is blocked at the CD4(-)CD8(-)CD25(+)CD44(-) pre-T cell stage. In contrast, K8(+)K5(+) TECs predominate in the thymi of human CD3epsilon transgenic mice in which thymocyte development is blocked at an earlier CD4(-)CD8(-)CD25(-)CD44(+) stage. Transplantation of newborn human CD3epsilon transgenic thymi under the kidney capsule of RAG-1(-/-) mice results in the emergence of K8(+)K5(-) TECs concomitant with the appearance of CD25(+) thymocytes. Together, the data suggest that cortical TEC development proceeds from a K8(+)K5(+) precursor subset to a K8(+)K5(-) stage in a differentiation process concomitant with T-cell lineage commitment.

Pulmonary surfactant proteins A and D enhance neutrophil uptake of bacteria

The collectins are a class of collagenous lectin proteins present in serum and pulmonary secretions [pulmonary surfactant protein (SP) A and SP-D] that are believed to participate in innate immune responses to various pathogens. With the use of flow cytometric and fluorescent-microscopic assays, SP-A and SP-D were shown to increase calcium-dependent neutrophil uptake of Escherichia coli, Streptococcus pneumoniae, and Staphylococcus aureus. Evidence is provided that the collectins enhanced bacterial uptake through a mechanism that involved both bacterial aggregation and direct actions on neutrophils. The degree of multimerization of SP-D preparations was a critical determinant of both aggregating activity and potency in enhancing bacterial uptake. The mechanisms of opsonizing activity of SP-D and SP-A differed in important respects from those of opsonizing antibodies. These results provide the first evidence that surfactant collectins may promote neutrophil-mediated clearance of bacteria in the lung independently of opsonizing antibody.

A DNA polymerase alpha accessory protein exhibits structural and functional similarities to SV40 large tumor antigen

Untransformed cells have been proposed to require a protein homologous to SV40 large tumor antigen (TAg) which functions as a component of the replicase complex during the initiation of DNA synthesis. By definition, this should be a phosphoprotein which interacts with the retinoblastoma protein (pRb) in G0 or early G1, and is capable of binding to and potentiating the activity of DNA polymerase alpha (pol alpha). This protein should also be an ATP-dependent helicase which interacts with the single-stranded DNA (ssDNA) binding protein, RP-A. Because of these requirements, a TAg homologous protein could be expected to contain epitopes with amino acid sequences similar to those of TAg at critical functional sites, such as ATP, pRb and pol alpha binding sites. TAg and a putative cellular homolog of TAg, DNA pol alpha accessory protein (alpha AP), were compared for pRb and pol alpha interaction, and for immunological identity. The analyses utilized immunoaffinity-purified TAg and pRb from a baculovirus expression system, and DNA pol alpha/primase and alpha AP chromatographically isolated from a mouse lymphocytic leukemia cell line. Monoclonal antibodies specific for the pol alpha or pRb binding sites on TAg interacted with alpha AP strongly enough to be employed for immunoaffinity purification of alpha AP. Anti-pRb and anti-TAg reciprocally coimmunoprecipitated pRb bound to TAg and pRb bound to alpha AP. The functional consequences of pol alpha interaction with TAg or alpha AP in the presence or absence of pRb was determined using pol alpha nucleotide incorporation assays. alpha AP exhibited the capacity to stimulate pol alpha activity, a capacity which was diminished in the presence of pRb. Lastly, TAg and alpha AP independently co-purified with pol alpha through a multi-step chromatographic protocol. These data indicate that a pol alpha accessory protein, alpha AP, exhibits functional and immunological similarities to SV40 TAg, suggest that alpha AP is involved in regulation of the initiation of DNA synthesis, and support the proposal that alpha AP may be a normal cell protein homologous to SV40 large T antigen.

Interactions of recombinant human pulmonary surfactant protein D and SP-D multimers with influenza A

To further study the structure and function of surfactant protein D (SP-D), recombinant human SP-D (rhSP-D) was isolated from the culture medium of Chinese hamster ovary (CHO)-K1 cells stably transfected with a full-length hSP-D cDNA. Although a significant fraction of the secreted rhSP-D was recovered as dodecamers similar to recombinant rat SP-D (rrSP-D), a major fraction accumulated as multimers of dodecamers indistinguishable from human proteinosis SP-D. As previously shown for the rat protein, rhSP-D agglutinated specific strains of influenza A virus (IAV), inhibited viral hemagglutinin activity, and protected neutrophils (PMN) from deactivation by IAV. However, the potency of rhSP-D multimers was severalfold greater than for purified dodecamers, comparable to natural, proteinosis hSP-D. Although rhSP-D multimers were also more potent than the serum collectins in mediating viral aggregation and protection of PMN, they were less potent than conglutinin in inhibiting infectivity in vitro. These studies establish that the propensity of hSP-D to form multimers of dodecamers is determined by its primary structure and demonstrate carbohydrate recognition domain valency-dependent interactions of SP-D with IAV.

Neutrophil deactivation by influenza A viruses: mechanisms of protection after viral opsonization with collectins and hemagglutination-inhibiting antibodies

Bacterial superinfections are a major cause of morbidity and mortality during influenza A virus (IAV) epidemics. Depression of phagocyte functions resulting from attachment of the IAV hemagglutinin (HA) to cell surface sialo-glycoproteins is a likely contributory cause of these infections. We have proposed that the group of collagenous lectins (termed collectins) present in blood and pulmonary surfactant play a role in initial host defense against IAV. We used here several recombinant human surfactant protein D (RhSP-D) preparations to determine the mechanism through which opsonization of IAV with collectins protects neutrophils against the deactivating effects of IAV on cellular respiratory burst responses in vitro. RhSP-D was markedly more potent than antibodies that inhibited viral hemagglutination activity (anti-HA antibodies) at protecting neutrophils in this assay. Unlike the anti-HA antibodies, RhSP-D was protective at concentrations that minimally inhibited viral hemagglutination activity. Two related features of SP-D--the degree of multimerization and the ability to cause aggregation of IAV particles--were critical determinants of the ability of SP-D to protect neutrophils against deactivation. Similarly SP-D-induced viral aggregate formation resulted in enhanced IAV binding to neutrophils and potentiated the ability of the virus itself to trigger neutrophil respiratory burst responses. In contrast to the case of IAV-antibody complexes, SP-D-IAV complexes attached to and activated neutrophils through a neuraminidase-sensitive mechanism (ie, similar to unopsonized IAV). These results indicate that collectin-mediated viral aggregation per se may be an important host defense mechanism not only by virtue of reducing the number of infectious viral particles, but also by promoting phagocyte responsiveness.

Localization of type I procollagen gene expression in silica-induced granulomatous lung disease and implication of transforming growth factor-beta as a mediator of fibrosis

We have used the silica-induced model of pulmonary injury in the rat to study the pattern of collagen expression in granulomatous lung inflammation. A single intratracheal instillation of silica into adult rats resulted in granulomatous inflammation leading to fibrosis and alveolar proteinosis. The development of disease in these animals was characterized over a 27-day period after treatment by means of histological, biochemical, and molecular analyses. Biochemical analyses indicated that significant increases in the weights of silicotic lungs were due to elevated amounts of DNA and total protein. Analysis of hydroxyproline content showed a 15-fold increase in this amino acid in silicotic lungs, confirming the development of a fibrotic reaction. In situ hybridization for type I procollagen mRNA displayed increased gene expression in the parenchyma, conducting airways, and vasculature of silicotic rats. Within the parenchyma, type I procollagen was expressed uniquely within granulomatous lesions. Immunohistochemistry indicated type I procollagen was being expressed by an alpha-smooth muscle actin-negative population of cells. Immunolocalization of extra-cellular transforming growth factor-beta showed coincident temporal and spatial overlap with type I procollagen expression, implicating this cytokine as a mediator of collagen gene expression in this model.

Increased elastin production in experimental granulomatous lung disease

In the normal, healthy lung, elastin production is restricted to periods of development and growth. However, elastin expression in the adult lung has been observed in some forms of pulmonary injury, including pulmonary fibrosis. Here, we report that elastin production is significantly increased within precise interstitial compartments of the lung in an experimental model of granulomatous lung disease. An increase in the number and volume of elastic fibers within the alveolar walls was apparent on histological examination of Verhoeff-van Gieson-stained sections of silicotic rat lungs. Quantitation of mature elastin cross-links indicated that silicosis was accompanied by a 17-fold increase in lung elastin content when compared with values from saline-treated controls. In situ hybridization for tropoelastin mRNA revealed that elastin production was absent from granulomatous lesions yet was prominent at nonfibrotic alveolar septal tips, where a high density of elastic fibers is seen in the normal lung. Immunohistochemistry indicated tropoelastin was being expressed by alpha-smooth muscle actin-containing cells. Transforming growth factor-beta was immunolocalized to granulomatous regions of the silicotic lung but was absent from regions showing increased tropoelastin expression. These data indicate that the reinitiation of tropoelastin gene expression is associated with granulomatous lung disease, and this expression leads to the aberrant accumulation of mature elastin in the lung.

Molecular structure of pulmonary surfactant protein D (SP-D)

Previous studies have shown that pulmonary surfactant protein D (SP-D) is composed of a 43-kDa polypeptide with a short NH2-terminal domain, a collagen sequence, and a COOH-terminal C-type lectin domain. In the present studies, ultrastructural and biochemical techniques were used to examine the quaternary structure of native rat SP-D (rSP-D). Electron microscopy of freeze-dried preparations demonstrated a highly homogeneous population of molecules with four identical rod-like arms (46 nm in length), each with an 8-9-nm diameter globular terminal expansion. The arms, which are similar in diameter to the type I collagen helix (approximately 4 nm), emanate from the central "hub" in two pairs that closely parallel each other for their first 10 nm. This structure is consistent with hydrodynamic studies that predict an highly asymmetric and extended molecule (f/f0 = 3.26) with a large Stokes radius (Rs = 18 nm). Pepsin digestion gave glycosylated, trimeric collagenous fragments (43 +/- 4 nm, 17 kDa/chain). Trimeric subunits containing intact triple helical domains were also liberated from SP-D dodecamers by sulfhydryl reduction under non-denaturing conditions. Digestion of rSP-D with bacterial collagenase generated a COOH-terminal carbohydrate binding fragment and a smaller peptide (approximately 12 kDa, unreduced) that contains interchain disulfide bonds. Electron microscopy also demonstrated higher orders of multimerization, with as many as 8 molecules associated at the hub. These studies demonstrate that SP-D is assembled as homopolymers of four identical trimeric subunits, that interactions between the amino-terminal domains of the trimers are stabilized by interchain disulfide bonds, and that SP-D molecules can associate to form complex multimolecular assemblies.

Recombinant pulmonary surfactant protein D. Post-translational modification and molecular assembly

Pulmonary surfactant protein D (SP-D) is a member of a family of collagenous C-type lectins that includes the serum mannose binding proteins and surfactant protein A. Recent studies have shown that rat SP-D (rSP-D) molecules are assembled as tetramers of trimeric subunits (12 mers) and that dodecamers can participate in higher orders of molecular assembly involving interactions of the amino-terminal peptide domains. In order to further study the assembly of SP-D in vitro, Chinese hamster ovary K1 cells were transfected with a full-length rat SP-D cDNA, and stable transfectants with high levels of SP-D production (approximately 6 x 10(6) dodecamers/cell/24 h) were obtained using a glutamine synthetase selection system. The secreted molecules (RrSP-D), which were purified by affinity chromatography on maltosyl-agarose, comigrated with rSP-D on SDS-polyacrylamide gel electrophoresis in the presence and absence of reduction, and coeluted with rSP-D dodecamers from 4% agarose. The major bacterial collagenase-resistant peptide showed a decreased mobility on reduction consistent with the formation of intrachain disulfide bonds. A 17-kDa pepsin-resistant fragment was isolated following overnight digestion with pepsin at 27 degrees C, confirming the formation of a triple helical domain comparable in size and thermal stability to that of natural SP-D. The expressed protein contained sialylated endoglycosidase F-sensitive carbohydrate; amino acid analysis of acid and alkaline hydrolysates demonstrated essentially normal levels of hydroxyproline, hydroxylysine, and hydroxylysine-glycosides. Electron microscopic studies showed a molecular structure indistinguishable from lung SP-D, with a similar small subpopulation of molecules showing higher orders of multimerization. Solid-phase neoglycoprotein binding assays gave the same saccharide inhibition profile as natural rat SP-D, and both proteins showed efficient saccharide-dependent agglutination of Escherichia coli. These studies demonstrate that a single genetically distinct chain type can account for the various and complex molecular assemblies of SP-D, and further verify the potential physiologic significance of the disulfide-bonded multimers and higher aggregates isolated from rat, bovine, and human lung lavage.

Lectin-mediated interactions of surfactant protein D with alveolar macrophages

Surfactant protein D (SP-D) is a calcium-dependent carbohydrate-binding protein that is secreted into the pulmonary airspaces by type II epithelial and Clara cells. Previous studies have shown that SP-D can bind to specific surfactant phospholipids and to glycoconjugates associated with the surface of various microorganisms, consistent with possible roles in surfactant metabolism and pulmonary host defense. We now describe specific saccharide-mediated interactions of SP-D with alveolar macrophages in lung tissue and in vitro. Biotinylated rat SP-D showed specific binding to alveolar macrophages in sections of rat lung; this labeling was inhibited by competing saccharides or EDTA. In addition, the binding of 125I-SP-D to isolated alveolar macrophages in the presence of calcium was time-dependent, saturable, and reversible and was preferentially inhibited by known monosaccharide and disaccharide ligands for SP-D. Scatchard analysis gave an apparent single class of binding sites with a Kd = 1.4 x 10(-6) M. We speculate that the multivalent structure of SP-D mediates bridging interactions between microbial glycoconjugates or surfactant phospholipids and specific glycosylated ligands expressed on the surface of phagocytic cells.

Modulation of surfactant protein D expression by glucocorticoids in fetal rat lung

The production of pulmonary surfactant protein D (SP-D) increases abruptly during late gestation, and the accumulation of this protein in lung tissue is increased following the exposure of fetal rats to glucocorticoids in utero. To examine the regulation of these events, we administered dexamethasone (Dex; 1 mg/kg/day intramuscularly for 3 days), or saline, to timed-pregnant rats and harvested the lungs on days 19 to 21 of gestation. Samples of pooled fetal lungs were analyzed for SP-D protein, mRNA, and gene transcription by immunoblot, Northern hybridization, and nuclear run-off transcription assays. Lungs from 19 day controls showed barely detectable levels of SP-D gene transcription and negligible accumulation of SP-D message. However, SP-D transcription and the accumulation of SP-D mRNA and protein were readily detected in lungs from 19 day Dex-treated rats. Dexamethasone also caused dose- and time-dependent increases in SP-D protein and mRNA accumulation in 19 day fetal lung explants. Immunohistochemistry of control 19 day lung using antibodies to rat SP-D showed only weak labeling of a small number of airway epithelial cells. By contrast, Dex-exposed rats showed strong staining of columnar and cuboidal epithelial cells lining airways and epithelial tubules and cuboidal cells lining primitive air sacs. In situ hybridization assays showed similar alterations in the number, intensity, and distribution of labeled epithelial cells in 19 day Dex-exposed lungs and demonstrated labeling of alveolar type II and nonciliated columnar cells in adult lung. These data indicate that the accelerated lung maturation accompanying glucocorticoid exposure in utero is associated with a precocious increase in SP-D gene transcription and protein production by pulmonary epithelial cells.

Genomic organization of human surfactant protein D (SP-D). SP-D is encoded on chromosome 10q22.2-23.1

Surfactant protein D (SP-D) is a member of the family of mammalian C-type lectins. SP-D is secreted into the pulmonary airspaces by lung epithelial cells and is believed to contribute to the lung's defense against inhaled microorganisms. We have previously characterized cDNAs specific for human SP-D (hSP-D). We now describe the partial characterization of genomic clones for hSP-D and present evidence for an SP-D gene with coding sequences spanning > 11 kilobases on the long arm of chromosome 10. Genomic sequencing demonstrated that the signal peptide/amino-terminal domain, the carbohydrate recognition domain, and the linking sequence between the collagen domain, and carbohydrate recognition domain are each encoded by a single exon, as for surfactant protein A and the mannose-binding protein C. However, sequencing also demonstrated a unique intron-exon structure for the collagen domain which is encoded on five exons, including four tandem exons of 117 bp. The latter exons show marked conservation in the predicted distribution of hydrophilic amino acids, consistent with tandem replication of this collagen gene sequence during evolution. Segregation analysis of HindIII digests of genomic DNA using specific cDNA probes demonstrated selective hybridization of radiolabeled hSP-D cDNA to chromosome 10- and 10q-containing human/hamster somatic hybrids. The presence of SP-D gene sequences was confirmed by DNA amplification using oligomers specific for sequences within the collagen domain of the hSP-D gene. Fluorescence in situ hybridization of metaphase chromosomes using genomic probes gave selective labeling of 10q22.2-23.1. We speculate that SP-D is encoded at a locus on 10q that includes the genes for surfactant protein A.

Accumulation of surfactant protein D in human pulmonary alveolar proteinosis

Surfactant protein D (SP-D) is a collagenous calcium-dependent carbohydrate-binding protein that is structurally related to the serum mannose-binding proteins and pulmonary surfactant protein A. SP-D was initially characterized as a biosynthetic product of freshly isolated rat type II cells and first purified in chemical amounts from bronchoalveolar lavage of rats with silica-induced alveolar lipoproteinosis. The present studies describe the characterization of human SP-D isolated from therapeutic bronchoalveolar lavage of patients with pulmonary alveolar proteinosis. Human proteinosis SP-D was extracted from the 10,000 x g pellet of bronchoalveolar lavage with 100 mmol/L glucose or ethylenediamine tetraacetic acid, and specifically bound to and eluted from maltosyl-agarose. The protein cross-reacted with monospecific antibodies to rat SP-D by enzyme-linked immunosorbent assay and immunoblot and eluted near the position of rat SP-D on reverse-phase high performance liquid chromatography. When chromatographed on 4% agarose (A-15M) in the presence of ethylenediamine tetraacetic acid, the solubilized human proteinosis SP-D eluted near the void volume and earlier than rat SP-D dodecamers or human SP-D multimers in the lavage supernatant. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting of proteins in the lavage pellet with antibodies to the carbohydrate-binding domain of proteinosis human SP-D demonstrated covalently cross-linked multimers of SP-D monomers (43 kd, reduced) and multimers of trimeric components stabilized by disulfide and non-disulfide bonds. These studies describe the isolation and biochemical characterization of human SP-D and demonstrate the abnormal accumulation of this protein in the air spaces of patients with alveolar proteinosis.

Velocity of mammalian skeletal muscle contraction as a function of fiber type, activation, initial length and temperature

Multiple stepwise regression analyses techniques were applied to develop modifications of the Hill force-velocity equation. Specifically, predictive models of the Hill a coefficient, the Hill b coefficient, and isometric strength P0 were developed for the following set of variables: the fraction of slow-twitch fibers (X), the recruitment magnitude (A), the initial muscle length (L), and the muscle temperature (T). Results indicate that the Hill a and Hill b coefficients and isometric strength P0 can be predicted with a high degree of accuracy. The utility of the equation is that it would allow development of a computer program to control the velocity of contraction of muscles with differing fiber compositions and lengths such as are found in the leg.

Surfactant protein D: subcellular localization in nonciliated bronchiolar epithelial cells

Surfactant protein D (SP-D, CP4) is a collagenous surfactant-associated carbohydrate binding protein that was initially characterized as a biosynthetic product of type II pneumocytes. Immunoperoxidase studies of formaldehyde solution-fixed and paraffin-embedded rat lung demonstrated staining for SP-D in the cytoplasm of a subpopulation of bronchiolar epithelial cells as well as type II cells. Accordingly, immunogold-labeling techniques were used to further examine the cellular distribution and subcellular localization of SP-D in the small airways. Lung tissues were fixed with 0.5% glutaraldehyde-3% paraformaldehyde and embedded in LR White resin. Sections were reacted with affinity purified polyclonal antibodies to SP-D, and sites of antibody binding were demonstrated using a biotinylated secondary antibody-streptavidin-gold detection system. Anti-SP-D selectively decorated secretory compartments of nonciliated bronchiolar cells (Clara cells) with strong and specific labeling of apical electron-dense secretory granules. Almost all of the granules in nonciliated columnar cells were labeled; however, labeling was typically nonuniform, with preferential decoration of the periphery of the granule. The largest numbers of immunoreactive epithelial cells were observed in the distal membranous bronchioles, with progressively smaller numbers of cells in more proximal bronchioles. There was no detectable labeling of cells lining the large cartilagenous airways or trachea. These studies provide evidence that SP-D is a secretory product of nonciliated bronchiolar cells. We suggest that Clara cell-derived SP-D is a component of bronchiolar lining material, consistent with our hypothesis that SP-D contributes to surfactant metabolism and/or host defense within small airways.

Interactions of surfactant protein D with bacterial lipopolysaccharides. Surfactant protein D is an Escherichia coli-binding protein in bronchoalveolar lavage

Surfactant protein D (SP-D) is a collagenous glycoprotein that is secreted into the pulmonary airspaces by alveolar type II and nonciliated bronchiolar cells. SP-D exhibits Ca(++)-dependent carbohydrate binding in vitro and is structurally related to the collagenous C-type lectins, including serum conglutinin, serum mannose-binding proteins, and surfactant protein A. Preliminary studies showed calcium- and saccharide-dependent binding of fluorescein-conjugated or radioiodinated SP-D to a variety of microorganisms, including Gram-negative bacteria and fungi. A laboratory strain of Escherichia coli (Y1088) was chosen to further examine the mechanism(s) of binding. Binding of SP-D to Y1088 was time dependent, saturable, and inhibited by cold SP-D or competing saccharides; Scatchard analysis gave a Kd of 2 x 10(-11) M. At higher concentrations, SP-D also caused Ca(++)-dependent agglutination of Y1088 that was inhibited by alpha-glucosyl-containing saccharides, antisera to the carbohydrate-binding domain of SP-D, or Y1088 LPS. Lectin blots showed specific binding of 125I-SP-D to Y1088 LPS, as well as LPS from other several strains of enteric Gram-negative bacteria. Immunogold studies demonstrated strong and uniform surface labeling of the bacteria. Rat and human bronchoalveolar lavage (BAL) caused Ca(++)-dependent agglutination of E. coli that was dose dependent and inhibited by competing saccharides or anti-SP-D. SP-D was selectively and efficiently adsorbed from rat BAL by incubation with E. coli, and incubation of E. coli with radiolabeled rat type II cell medium revealed that SP-D is the major E. coli-binding protein secreted by freshly isolated cells in culture. We suggest that SP-D plays important roles in the lung's defense against Gram-negative bacteria.