Isoforms of Neuropilin-2 Denote Unique Tumor-Associated Macrophages in Breast Cancer

Tumor-associated macrophages (TAMs) exert profound influence over breast cancer progression, promoting immunosuppression, angiogenesis, and metastasis. Neuropilin-2 (NRP2), consisting of the NRP2a and NRP2b isoforms, is a co-receptor for heparin-binding growth factors including VEGF-C and Class 3 Semaphorins. Selective upregulation in response to environmental stimuli and independent signaling pathways endow the NRP2 isoforms with unique functionality, with NRP2b promoting increased Akt signaling via receptor tyrosine kinases including VEGFRs, MET, and PDGFR. Although NRP2 has been shown to regulate macrophage/TAM biology, the role of the individual NRP2a/NRP2b isoforms in TAMs has yet to be evaluated. Using transcriptional profiling and spectral flow cytometry, we show that NRP2 isoform expression was significantly higher in TAMs from murine mammary tumors. NRP2a/NRP2b levels in human breast cancer metastasis were dependent upon the anatomic location of the tumor and significantly correlated with TAM infiltration in both primary and metastatic breast cancers. We define distinct phenotypes of NRP2 isoform-expressing TAMs in mouse models of breast cancer and within malignant pleural effusions from breast cancer patients which were exclusive of neuropilin-1 expression. Genetic depletion of either NRP2 isoform in macrophages resulted in a dramatic reduction of LPS-induced IL-10 production, defects in phagosomal processing of apoptotic breast cancer cells, and increase in cancer cell migration following co-culture. By contrast, depletion of NRP2b, but not NRP2a, inhibited production of IL-6. These results suggest that NRP2 isoforms regulate both shared and unique functionality in macrophages and are associated with distinct TAM subsets in breast cancer.

680 Isoforms of neuropilin-2 regulate distinct macrophage functions and are associated with unique tumor-associated macrophages in murine and human breast cancer

Background

Tumor-associated macrophages (TAMs) exert profound influence over breast cancer progression, promoting immunosuppression, angiogenesis, and metastasis.1 Neuropilin-2 (NRP2), consisting of NRP2a and NRP2b isoforms, is a co-receptor for heparin-binding growth factors including VEGF-C and Class 3 Semaphorins. Selective upregulation in response to environmental stimuli and independent signaling pathways endow the NRP2 isoforms with unique functionality.2 3 We have shown that the two isoforms of NRP2 endow opposing functionality to tumor cells due to distinct signaling pathways, with NRP2b promoting metastatic behavior.3 Although NRPs have been shown to regulate macrophage/TAM biology, the role of NRP2 isoforms in TAM functionality has yet to be evaluated.

Methods

To assess the contribution of NRP2 isoforms to macrophage biology, conditional NRP2a and NRP2b knockout mice and stable shRNA knockdown of NRP2a or NRP2b in Raw264.7 macrophages were generated. Phagocytosis, lysosomal processing of phagocytosed cargo, cytokine production, and influence on tumor cell migration were assessed in vitro using NRP2 isoform knockdown macrophages. NRP2 isoform expression was evaluated on TAMs from murine 4T1 and EO771 mammary carcinoma models using spectral cytometry and single-cell qPCR. NRP2 isoforms and approximated immune composition were evaluated in paired primary tumors and distant metastasis using RNAseq in a cohort of 99 breast cancer patients. High-dimensional myeloid phenotyping was performed on malignant pleural effusions (MPEs) from breast cancer patients or effusions of benign origin using 33-color spectral cytometry and unbiased computational analysis.

Results

NRP2 isoform expression was significantly increased in TAMs from murine tumors compared to macrophages from healthy mammary glands. NRP2 isoforms in human primary and metastatic breast cancer were strongly correlated with one another and positively correlated with increased TAMs. Distinct phenotypes of NRP2 isoform-expressing TAMs in were present in 4T1 and EO771 mouse breast cancers and within MPEs from breast cancer patients which were associated with high levels of activation and potential response to a hypoxic tumor niche. Genetic depletion of either NRP2 isoform resulted in dramatic reduction of LPS-induced IL-10 production, defects in phagosomal processing of apoptotic breast cancer cells, and increase in cancer cell migration following co-culture. By contrast, inhibition of IL-6 production was specific in NRP2b knockdown cells while phagocytic uptake of labeled particulates was inhibited only by NPR2a knockdown.

Conclusions

These results demonstrate that NRP2 isoforms regulate both shared and distinct functionality in macrophages and that NRP2 isoform expression identifies unique TAM subsets in breast cancer.

Acknowledgements

This work was supported by awards from the Susan G. Komen Foundation (CCR15329745), U.S. Department of Defense (W81XWH1910650), and American Lung Association/Thoracic Surgery Foundation to ACS. RD was supported by funding from a Department of Veteran's Affairs Career Development Award (CX001771-01A2) and the University of Pittsburgh's Dean Faculty Advancement Award. ESY was supported by the NCI of the NIH under R03 CA245774. MTL was supported by the NCI of the NIH under awards R01CA181450 and R01CA206012 as well as ITTC/UPMCE. RD and ACS were further supported by funding from the Department of Cardiothoracic Surgery.

References

Williams CB, Yeh ES, Soloff AC. Tumor-associated macrophages: unwitting accomplices in breast cancer malignancy. Npj Breast Cancer [Internet]. Breast Cancer Research Foundation/Macmillan Publishers Limited; 2016;2:15025. Available from: http://dx.doi.org/10.1038/npjbcancer.2015.252.

Nasarre P, Gemmill RM, Potiron VA, Roche J, Lu X, Barón AE, et al. Neuropilin-2 is upregulated in lung cancer cells during TGF-β1–Induced epithelial–mesenchymal transition. Cancer Res [Internet] 2013;73:7111 LP–7121. Available from: http://cancerres.aacrjournals.org/content/73/23/7111.abstract3.

Gemmill RM, Nasarre P, Nair-Menon J, Cappuzzo F, Landi L, D'Incecco A, et al. The neuropilin 2 isoform NRP2b uniquely supports TGFβ-mediated progression in lung cancer. Sci Signal [Internet] 2017;10. Available from: http://stke.sciencemag.org/content/10/462/eaag0528.abstract

Ethics Approval

The study was approved by the University of Pittsburgh's Institutional Review Board approval number CR19120172-005.

Newly Identified Chemicals Preserve Mitochondrial Capacity and Decelerate Loss of Photoreceptor Cells in Murine Retinal Degeneration Models

Purpose: Metabolic stress and associated mitochondrial dysfunction are implicated in retinal degeneration irrespective of the underlying cause. We identified seven unique chemicals from a Chembridge DiverSET screen and tested their protection against photoreceptor cell death in cell- and animal-based approaches. Methods: Calcium overload (A23187) was triggered in 661W murine photoreceptor-derived cells, and changes in redox potential and real-time changes in cellular metabolism were assessed using the MTT and Seahorse Biosciences XF assay, respectively. Cheminformatics to compare structures, and biodistribution in the living pig eye aided in selection of the lead compound. In-situ, retinal organ cultures of rd1 mouse and S334ter-line-3 rat were tested, in-vivo the light-induced retinal degeneration in albino Balb/c mice was used, assessing photoreceptor cell numbers histologically. Results: Of the seven chemicals, six were protective against A23187- and IBMX-induced loss of mitochondrial capacity, as measured by viability and respirometry in 661W cells. Cheminformatic analyses identified a unique pharmacophore with 6 physico-chemical features based on two compounds (CB11 and CB12). The protective efficacy of CB11 was further shown by reducing photoreceptor cell loss in retinal explants from two retinitis pigmentosa rodent models. Using eye drops, CB11 targeting to the pig retina was confirmed. The same eye drops decreased photoreceptor cell loss in light-stressed Balb/c mice. Conclusions: New chemicals were identified that protect from mitochondrial damage and lead to improved mitochondrial function. Using ex-vivo and in-vivo models, CB11 decreased the loss of photoreceptor cells in murine models of retinal degeneration and may be effective as treatment for different retinal dystrophies.

Abstract 2994: Inhibition of the NRP2b:GSK3β binding interaction with peptides and macrocycles exerts anticancer effects in lung cancer

Introduction: Neuropilin-2b (NRP2b) expression is associated with pro-tumorigenic properties of NSCLCs. We previously reported that NRP2b promotes metastasis and drug resistance, while the canonical NRP2a isoform is inhibitory. Our recent work indicates that the NRP2b cytoplasmic domain recruits GSK3β to phosphorylate and promote degradation of co-recruited PTEN, thereby enhancing AKT activity leading to enhanced survival, migration and drug resistance. We identified a 15-amino acid motif near the NRP2b C-terminus required for interaction with GSK3β. Herein, we describe the anticancer effect of peptides and drug-like macrocycles designed to disrupt this interaction.

Methods: We used the cytoplasmic sequence of NRP2b for decoy peptides designed to disrupt the interaction with GSK3β. Control peptides were synthesized with alanine replacements for three amino acids suggested as crucial for GSK3β recruitment. All peptides were N-terminally myristoylated to promote association with and flipping to the inner leaflet of the plasma membrane. A library of over 42,000 drug-like macrocycles was screened in silico for compounds predicted to fit and compete with the NRP2b:GSK3β binding interface. Decoy peptides and macrocycles were assessed for anti-NRP2b activity using assays for migration and drug-tolerant persister cells. Transwell migration assays were performed using a Neuro Probe Reusable Multiwell Chemotaxis Chamber. Persister cell assays were performed with EGFR mutant PC9 and HCC827 cells in the presence of EGFR inhibitors (gefitinib or osimertinib), followed by drug withdrawal and colony formation assays.

Results: As previously reported, knockdown of NRP2b inhibited, while knockdown of NRP2a enhanced, migration of lung cancer cell lines. Importantly, emergence of drug-tolerant persister cells was similarly inhibited by knockdown of NRP2b and enhanced by knockdown of NRP2a. Wild type, but not control, peptides abrogated the pro-tumorigenic effects of NRP2a knockdown on both migration and persister cell formation with IC50s of ~250 nM. The most effective macrocycles, M3 and M7, inhibited NRP2b-dependent migration with IC50s of 1-3 µM. Both macrocycles also inhibited generation of persister cell colonies from shNRP2a-PC-9 cells. However, only M3 was effective at blocking persisters from shNRP2a-HCC827 cells.

Conclusions: NRP2b:GSK3β interaction is a therapeutic target in NSCLC affecting migration/invasion and persister colony formation associated with the emergence of resistance to EGFR inhibitors. This work justifies further development of these peptides and drug-like macrocycles as therapeutic modalities in lung cancer.

Citation Format: Cecile Nasarre, Yuri K. Peterson, Patrick Nasarre, Anastasios Dimou, Kent E. Armeson, Harry A. Drabkin, Nancy Demore, Chadrick E. Denlinger, Robert M. Gemmill. Inhibition of the NRP2b:GSK3β binding interaction with peptides and macrocycles exerts anticancer effects in lung cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2994.

Neuropilin-2b facilitates resistance to tyrosine kinase inhibitors in non-small cell lung cancer

OBJECTIVE

Innate and acquired resistance is the principle factor limiting the efficacy of tyrosine kinase inhibitors in lung cancer. We have observed a dramatic upregulation of the cell surface co-receptor neuropilin-2b in lung cancers clinically treated with tyrosine kinase inhibitors correlating with acquired resistance. We hypothesize that neuropilin-2b plays a functional role in acquired tyrosine kinase inhibitor resistance.

METHODS

Non-small cell lung cancer proliferation and survival were determined during chronic tyrosine kinase inhibitor exposure in the presence or absence of neuropilin-2b knock-down. Interactions of neuropilin-2a and neuropilin-2b isoforms with PTEN and GSK3β were assessed by immunoprecipitation. Neuropilin-2a and neuropilin-2b mutants deleted for their cytoplasmic domains were used to identify regions responsible for neuropilin-2b-GSK3β interaction. Because GSK3β is known to phosphorylate and degrade PTEN, phospho-PTEN and total PTEN levels were assessed after transfection of neuropilin-2a and neuropilin-2b wild-type and mutant constructs.

RESULTS

Non-small cell lung cancer cells chronically treated with gefitinib or osimertinib developed drug resistance and exhibited logarithmic growth in the presence of endothelial growth factor receptor tyrosine kinase inhibitors. However, neuropilin-2b knockdown cells remained sensitive to gefitinib. Likewise, neuropilin-2b knockdown suppressed and neuropilin-2a knockdown enhanced cellular migration. Acquired drug resistance and cell migration correlated with neuropilin-2b-dependent AKT activation with the intermediate step of GSK3β-dependent PTEN degradation. A specific binding site for GSK3β on the cytoplasmic domain of neuropilin-2b was identified with truncated protein constructs and computer modeling.

CONCLUSIONS

Neuropilin-2b facilitates non-small cell lung cancer resistance to tyrosine kinase inhibitors, and this biological effect relates to AKT activation. Neuropilin-2b GSK3β interactions appear to be essential for PTEN degradation and AKT activation in lung cancer cells. Disruption of the neuropilin-2b GSK3β interaction may represent a novel treatment strategy to preserve sensitivity to tyrosine kinase inhibitors in non-small cell lung cancer.

Abstract 2624: NRP2b promotes migration, drug resistance and AKT activation in lung cancers by recruiting GSK3â to phosphorylate and destabilize PTEN

Background: Neuropilins (NRPs) are cell surface co-receptors known to enhance signaling from multiple ligands, including growth factors and their cognate receptors, such as HGF/MET. We have previously shown that the novel “b” isoform of NRP2 (NRP2b) is specifically associated with aggressive NSCLC and is required for TGFβ-induced EMT. We also found that NRP2b promotes AKT activation, drug resistance and metastatic spread, while the canonical NRP2a isoform inhibits these processes. However, the mechanisms supporting these differential functions remain obscure.

Results: Live cell imaging revealed that NRP2b expression led to slow internalization/rapid surface recycling of HGF-bound MET compared to NRP2a, which promoted rapid internalization and little/no recycling. Co-immunoprecipitation experiments showed that GSK3β interacted robustly with NRP2b, but only weakly with NRP2a. Our previous work demonstrated analogous differential recruitment of PTEN, but with reversed preferences; i.e., robust binding to NRP2a, but weak binding to NRP2b. Importantly, GSK3β inhibition blocked HGF-dependent migration of lung cancer cells expressing NRP2b, but not in cells expressing NRP2a. Given that PTEN is an established target of GSK3β, and that modification by GSK3β leads to its proteasome-mediated degradation, PTEN levels were examined in cells expressing individual NRP2 isoforms. PTEN was significantly reduced by expression of NRP2b, but not by NRP2a. The reduction of PTEN in the presence of NRP2b was blocked by inhibition of GSK3β, and by proteasome inhibition with MG132. Despite lower PTEN levels, phosphorylation of the GSK3β target site on Thr366 was specifically increased by NRP2b. Co-immunoprecipitation of GSK3β with NRP2b deletion mutants identified a C-terminal 15 amino acid peptide as the site of interaction. Mutants without this sequence failed to recruit GSK3β and failed to reduce PTEN levels. In silico modeling of this peptide suggested an amphipathic alpha-helical structure with a high affinity docking site (ΔG = -45 kcal) on the atomic structure of GSK3β.

Conclusion: Our results suggest that NRP2b promotes receptor signaling to AKT by differential endosomal trafficking and by recruitment of GSK3β. This kinase will phosphorylate and destabilize active PTEN recruited into the complex by NRP2a, which heterodimerizes with NRP2b. Increased AKT signaling following PTEN loss is likely responsible for the pro-tumorigenic properties of NRP2b, including resistance to targeted agents and metastatic spread. This novel mechanism for NRP2b function suggests that targeting its interaction with GSK3β might be a fruitful therapeutic strategy to reduce drug resistance and/or metastatic spread in lung cancer.

Citation Format: Anastasios Dimou, Cecile Nasarre, Monika Gooz, Rose Pagano, Yuri Peterson, Kent Armeson, Harry A. Drabkin, Patrick Nasarre, Chadrick E. Denlinger, Robert M. Gemmill. NRP2b promotes migration, drug resistance and AKT activation in lung cancers by recruiting GSK3â to phosphorylate and destabilize PTEN [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2624.

Neuropilin-2 Isoforms Regulate Distinct Functions of Tumor-associated Macrophages in Breast Cancer

Introduction

Neuropilins are neural guidance molecules which contribute to tissue development. We have shown that the two isoforms of neuropilin-2 endow opposing functionality to tumor cells due to distinct signaling pathways, with Nrp2b promoting metastatic behavior. Due to the role of macrophages (Mθ) in organogenesis and metastasis, we examine the role of Nrp2 isoforms in these cells.

Methods

Stable shRNA knockdown of Nrp2a or Nrp2b in Raw264.7 Mθ were generated. Phagocytosis, cytokine production, and migration were assessed in knockdowns in response to stimuli (TGFβ, HGF, VEGF, IL-10, IFNγ, LPS, β-glucan). Nrp2 isoforms in Mθ from mouse mammary tissue or EO771-induced mammary tumors were measured by FACS and RT-PCR. Mθ were phenotyped via FACS for wound-healing or inflammatory markers. Single-cell (sc)qPCR for a 96 gene panel examining components of signaling pathways, autophagy, metabolism, and pro/anti-tumor responses was performed on 576 CD11b+F4/80+ TAMs FACS-sorted from EO771 tumors.

Results

Nrp2b expression was significantly upregulated in TAMs compared to Mθ of the blood, spleen, or mammary tissues. 56% of the scqPCR transcripts analyzed were significantly altered in Nrp2bHigh vs. Nrp2bLow TAMs, and computation analysis (PCA/tSNE) revealed two distinct TAM subsets enriched for Nrp2b. Nrp2b+ Raw264.7 cells showed decreased ability to phagocytose tumor cells, but increased rates of division and migration in response to growth factors compared to Nrp2a+ counterparts.

Conclusions

We demonstrate, for the first time, that the principle neuropilin-2 isoforms are present in Mθ, regulate unique functionality, and that Nrp2b+ TAMs are both upregulated in mammary tumors and represent a phenotypically unique subtype.

Delivery of CR2-fH Using AAV Vector Therapy as Treatment Strategy in the Mouse Model of Choroidal Neovascularization

Complement activation plays a significant role in age-related macular degeneration (AMD) pathogenesis, and polymorphisms interfering with factor H (fH) function, a complement alternative pathway (AP) inhibitor, are associated with increased AMD risk. We have previously validated an AP inhibitor, a fusion protein consisting of a complement receptor 2 fragment linked to the inhibitory domain of fH (CR2-fH) as an efficacious treatment for choroidal neovascularization (CNV) when delivered intravenously. Here we tested an alternative approach of AAV-mediated delivery (AAV5-VMD2-CR2-fH or AAV5-VMD2-mCherry) using subretinal delivery in C57BL/6J mice. Secretion of CR2-fH was confirmed in polarized retinal pigment epithelium (RPE) cells. A safe concentration of AAV5-VMD2-CR2-fH was identified using electroretinography, optical coherence tomography (OCT), RPE morphology, and antibody profiling. One month after gene delivery, CNV was induced using argon laser photocoagulation. OCT assessment demonstrated reduced CNV with AAV5-VMD2-CR2-fH administration. Bioavailability studies revealed that gene-therapy delivered similar levels of CR2-fH to the RPE/choroid as treatment by intravenous injections, and C3a ELISA verified reduced CNV-associated ocular C3a production. These results contribute to existing data illustrating the importance of the AP of complement in CNV development and its potential role in AMD treatment. Demonstration of AAV-vector efficacy opens new avenues for the development of treatment strategies.

Small Molecules that Protect Mitochondrial Function from Metabolic Stress Decelerate Loss of Photoreceptor Cells in Murine Retinal Degeneration Models

One feature common to many of the pathways implicated in retinal degeneration is increased metabolic stress leading to impaired mitochondrial function. We found that exposure of cells to calcium ionophores or oxidants as metabolic stressors diminish maximal mitochondrial capacity. A library of 50,000 structurally diverse "drug-like" molecules was screened for protection against loss of calcium-induced loss of mitochondrial capacity in 661W rod-derived cells and C6 glioblastomas. Initial protective hits were then tested for protection against IBMX-induced loss of mitochondrial capacity as measured via respirometry. Molecules that protected mitochondria were then evaluated for protection of rod photoreceptor cells in retinal explants from rd1 mice. Two of the molecules attenuated loss of photoreceptor cells in the rd1 model. In the 661W cells, exposure to calcium ionophore or tert-butylhydroperoxide caused mitochondrial fragmentation that was blocked with the both compounds. Our studies have identified molecules that protect mitochondria and attenuate loss of photoreceptors in models of retinal degeneration suggesting that they could be good leads for development of therapeutic drugs for treatment of a wide variety of retinal dystrophies.

Functional interaction between matrix metalloproteinase-3 and semaphorin-3C during cortical axonal growth and guidance

In the developing cortex, axons and dendrites extend progressively in response to environmental cues attracting or repelling growing processes. Recent evidence suggests the existence of a functional link between guidance molecules and metalloproteinases. Here, we analyzed the putative functional interaction of matrix metalloproteinases (MMPs) with guidance cues of the semaphorin family during growth and guidance of cortical axons. Our results demonstrate that the expression pattern and the proteolytic activity of MMP-3 are consistent with a role of this particular MMP during cortical axon outgrowth. We found that MMP-3 is required for an optimal axon extension and is involved in the Sema3C-dependent chemoattraction of cortical axons by modulating both the growth capacity and the orientation of growth. Interestingly, the inhibitory Sema3A decreased both the expression and activity of MMP-3. Taken together, our results reveal a molecular interaction between MMPs and semaphorins providing new insight into the molecular mechanism allowing axonal growth cone to respond to environmental guidance cues in the context of cortical development.

Mécanismes cellulaires et moléculaires de la croissance axonale

INTRODUCTION

During embryonic and post-natal development, numerous axonal connections are formed establishing a functional nervous system. Knowledge of the underlying molecular and cellular mechanisms controlling this phenomenon is improving.

STATE OF THE ART

In this review, we present the general principles of axon guidance together with the major families of guidance signals. This includes the tyrosine kinase receptors Eph and their ligands Ephrins, the netrins, the semaphorins, the slits and other major components of the extracellular matrix. These types of guidance signals share common functional properties leading to actin cytoskeleton remodelling. The direct or indirect interactions between the receptors of these guidance cues and actin modulators is the final step of the signalling cascade constituting the fundamental mechanism defining the orientation and extension of the axonal growth cone. These factors are involved in the formation of many, if not all, axonal projections for which they act as repulsive (inhibitory) or attractive (promoting) signals.

PERSPECTIVES

the knowledge of these mechanisms is particularly interesting since the inhibition of axonal outgrowth is considered to be one of the major obstacles to nerve regeneration in the central nervous system. Indeed, most of the guidance signals expressed during brain development are up-regulated in lesion sites where they contribute to the lack of nerve re-growth. Here, we present the nature of the mechanical barrier, the so called glial scar, and we describe the major inhibitory molecules preventing axonal extension.

CONCLUSION

the comprehension of the molecular mechanisms involved in axon growth and guidance represents a major advance towards the definition of novel therapeutic strategies improving nerve regeneration. The path to the clinical application of these molecular factors remains long. Nevertheless, the next decade will undoubtedly provide challenging data that will modify the current therapeutic approaches.

The influence of climate on the epidemiology of bartonellosis in Ancash, Peru

The aim of this study was to evaluate the association between bartonellosis and selected climatic factors during the time periods 1983-1988 and 1995-99, which included two events of the El Niño phenomenon (1986-88, 1997-98), and to identify a reliable climate parameter to be used as an alert indicator for bartonellosis outbreaks in Ancash. The study site was Ancash and its province Carhuaz, Peru. Time-series cross-correlation analysis was used to assess the association between bartonellosis and climate parameters. A higher, almost 4-fold, monthly bartonellosis incidence risk in Ancash department was observed during the El Niño events of 1986-88 and 1997-98. At a regional (Ancash department) and local level (Carhuaz, Ancash), the best correlation was observed between bartonellosis and sea-surface temperature (SST). The results indicate that SST would be the best climate parameter to be used as an alert indicator for bartonellosis outbreaks in Ancash.

Granulomatous inflammatory response to recombinant filarial proteins of Brugia species

The lymphatic inflammatory response in Brugia-infected jirds peaks early during primary infections and then decreases in severity as judged by the numbers of lymph thrombi present within these vessels. Antigen-specific hypersensitivity reactions in these animals was measured by a pulmonary granulomatous inflammatory response (PGRN) induced by somatic adult worm antigen (SAWA)-coated beads, and by cellular proliferative responses of renal lymph node cells. The kinetics of these responses temporally correspond to lymphatic lesion formation. The importance of any single antigen to the induction of this inflammatory response has not been elucidated. In this study, the PGRN was used to measure the cellular immune response to four recombinant filarial proteins during the course of a primary B. pahangi infection. These proteins were BpL4, glycoprotein (glutathione peroxidase) gp29, heat shock protein (hsp) 70, and filarial chitinase. All were fusion proteins of maltose-binding protein (MBP). Control beads included those coated with diethanolamine (DEA), SAWA, or MBP. The measurements of PRGN were made at 14, 28, 56, and > 150 days postinfection (PI) in infected jirds, in jirds sensitized with SAWA, and in uninfected jirds. The secretory homolog of glutathione peroxidase gp29 was the only recombinant protein tested that induced a significantly greater PGRN (P < 0.05) than controls. This was seen at 28 days PI. These observations indicate that gp29 may be part of the worm antigen complex that induces an early inflammatory response, a response similar to that observed with SAWA. These studies indicate that this approach is useful in investigating the functional ability of specific proteins in the induction and down-regulation of immune-mediated inflammatory responses elicited by filarial parasites. Absence of a granulomatous response to the other recombinant proteins used may be related to the nature and sensitivity of the assay used or the character of recombinant proteins tested.

Down regulation of macrophage activation in Brugia pahangi-infected jirds (Meriones unguiculatus)

The macrophage is a major component of the inflammatory response induced by lymphatic tissue-dwelling filariae. Intraperitoneal (i.p.) infections with Brugia pahangi in Mongolian gerbils, or jirds (Meriones unguiculatus), induce a peritoneal inflammatory response characterized by accumulation of numerous macrophages and fewer eosinophils. This inflammatory response is associated with the release of microfilariae by female worms. The aim of this study was to investigate the activation state of the peritoneal macrophages during the course of i.p. infections with either male or female worms. Activation was determined by a toxoplasmacidal assay and assays which measured the production of tumor necrosis factor (TNF)-like activity and nitric oxide (NO) production. The development of these assays with jirds was initially conducted in parallel with the mouse system, which served as a positive control. Jird macrophages became activated to kill Toxoplasma gondii by in vivo immunization with Mycobacterium bovis BCG in a pattern similar to that of mouse macrophages. However, unlike the mouse system, supernatants from purified protein derivative- or concanavalin A-stimulated jird splenocytes plus lipopolysaccharide failed to activate jird macrophages in vitro or induce NO production. These results indicate that factors involved in jird macrophage activation may differ from those demonstrated in the mouse system and other systems. i.p. infections of 15 days in duration with either male or female worms induced macrophage activation as measured by Toxoplasma killing and TNF production. These responses decreased as the infection progressed to the chronic period on a time course that parallels the down regulation of experimental B. pahangi granulomas. There was no evidence of NO production by activated jird macrophages. These data indicate that macrophage function is down modulated during filarial infection and suggest that mechanisms involved in macrophage deactivation are related to those that induce down modulation of the systemic granulomatous inflammatory response in the jird. This response is not dependent on the microfilarial stage of the parasite and is also independent of mechanisms which induce peritoneal accumulations of macrophages.

Effect of gamma radiation on Brugia L3 development in vivo and the kinetics of granulomatous inflammation induced by these parasites

Previous studies have shown that the downregulation of parasite-specific cellular immune response in Brugia-infected jirds requires viable worms but is not dependent on microfilariae (MF) for either induction or maintenance of this phenomenon. To clarify further which life cycle stages induce filarial hyporesponsiveness, jirds were infected intraperitoneally with third stage larvae (L3) exposed to 0, 15, 25, 35, 45, or 90 krad of gamma radiation to differentially alter L3 development. Necropsies were performed at 7, 14, 28, and 118 days postinoculation (DPI). The degree of parasite development, intraperitoneal inflammation, and pulmonary granulomatous inflammation (PGRN) to parasite antigen-coated beads embolized in the lungs were monitored at the time of necropsy. Parasite survival and worm lengths were inversely related to the irradiation dose. Gamma radiation at 35, 45, or 90 krad prevented larval molt to the adult stage. Some parasites irradiated with 15 or 25 krad developed beyond fourth stage larvae (L4) to infertile adult females. The PGRN peaked at 14 DPI in all infected groups. Downregulation of the PGRN occurred after 14 DPI in groups that received nonirradiated L3 or L3 irradiated with 15 krad. No significant decrease of the PGRN occurred in groups that received parasites irradiated with more than 15 krad. Significant peritoneal inflammation as indicated by an increase in macrophages occurred only in jirds that received nonirradiated L3. These data demonstrate the importance of the adult stages in inducing downmodulation in the absence of MF and suggest that the L4 may also play a role in the induction of this phenomenon. An alternate conclusion is that parasite burden and not developmental stage is important in the induction of this hyporesponsive state.

Brugia pahangi: differential induction and regulation of jird inflammatory responses by life-cycle stages

It has been hypothesized that different life-cycle stages of filarial nematodes induce different host responses. This concept was examined in the Brugia pahangi-jird model of lymphatic filariasis by measuring the kinetics of inflammatory responses to parasite antigens following intraperitoneal inoculation of different life-cycle stages. For this purpose, viable female or male worms, L3, L4, or microfilarial stage, were used. Dead worms served as controls. Worm and microfilarial burdens, pulmonary granulomatous inflammation (PGRN) to soluble adult worm antigen (SAWA)-coated beads, and peritoneal eosinophil and macrophage numbers were assessed at different days post-inoculation. All jirds inoculated with any of these life-cycle stages developed an early PGRN to SAWA which was later significantly reduced. Only viable worms induced down-regulation of the PGRN response. These results indicate that the hyporesponsive state is induced and maintained by all life-cycle stages. Also, the degree of granulomatous response was influenced by worm burden, with larger worm burdens inducing lower initial levels of PGRN to SAWA. Peritoneal inflammatory responses differed from the systemic response in that numbers of macrophages increased with time and microfilarial accumulation. No correlation was observed between peritoneal inflammatory responses measured by eosinophil and macrophage numbers and PGRN to SAWA.

Cellular immune responses of jirds to extracts of life cycle stages and adult excretory secretory products during the early development of Brugia pahangi

The Brugia-jird model of lymphatic filariasis was used to examine the induction of cellular immune responses during the early premicrofilaremic phases of the infection. The intensity of the pulmonary granulomatous inflammatory response (PGRN) was determined by measuring granuloma areas around Sepharose beads coated with parasite extracts which were embolized in the lungs of jirds prior to necropsy. Necropsies were performed at 7, 14, 28, 56, and 150 days postinfection (DPI). These time points correspond to specific developmental changes in the life cycle. Lymphocyte blastogenesis assays were performed using cells from draining renal lymph nodes and splenocytes at 14 and 150 DPI. Soluble extracts of third stage larvae (L3), fourth stage larvae (L4), adult females, adult males, microfilariae (MF), and excretory secretory products (ES) of males and females were used in both measurements of cellular responsiveness. A marked granulomatous response to parasite extracts peaked at 7 DPI or 14 DPI followed by a gradual decrease to a hyporesponsive state at 120 DPI. The response of renal lymph node cells also was significantly elevated at 14 DPI and significantly decreased at > 150 DPI. The splenocyte responses were erratic and did not follow this pattern. Significant differences in PGRN responses to somatic extract preparations were not seen during the early stages of the infection (7, 14, 28 DPI), but those to MF and L3 were significantly less at 56 and 120 DPI. Although PGRN responses to ES followed a similar pattern, these were less than those to the somatic extract. The data indicated that a rapid, intense cell-mediated inflammatory response is induced early during a primary infection and that this response is rapidly downregulated. This downregulation begins prior to the maturation of adult parasites and microfilarial production. The early phase of the cellular response appears to be compartmentalized in that this response was consistently observed in the renal lymph nodes but not in the spleen. Soluble protein components of the parasites responsible for these responses are likely multiple and shared by all life cycle stages.

Malignant retroperitoneal paraganglioma in a horse

A large primary retroperitoneal sublumbar neoplasm in a horse, with disseminated neoplastic foci in the brain, lung, kidney and spleen is described. The diagnosis was based on light microscopical studies and positive immunostaining for neuron-specific enolase. Because of the location of the primary tumour mass, the aortico-sympathetic ganglion (organ of Zukerkandl) is proposed as the origin.