Vaccination induces rapid protection against bacterial pneumonia via training alveolar macrophage in mice

Vaccination strategies for rapid protection against multidrug-resistant bacterial infection are very important, especially for hospitalized patients who have high risk of exposure to these bacteria. However, few such vaccination strategies exist due to a shortage of knowledge supporting their rapid effect. Here, we demonstrated that a single intranasal immunization of inactivated whole cell of Acinetobacter baumannii elicits rapid protection against broad A. baumannii-infected pneumonia via training of innate immune response in Rag1-/- mice. Immunization-trained alveolar macrophages (AMs) showed enhanced TNF-α production upon restimulation. Adoptive transfer of immunization-trained AMs into naive mice mediated rapid protection against infection. Elevated TLR4 expression on vaccination-trained AMs contributed to rapid protection. Moreover, immunization-induced rapid protection was also seen in Pseudomonas aeruginosa and Klebsiella pneumoniae pneumonia models, but not in Staphylococcus aureus and Streptococcus pneumoniae model. Our data reveal that a single intranasal immunization induces rapid and efficient protection against certain Gram-negative bacterial pneumonia via training AMs response, which highlights the importance and the possibility of harnessing trained immunity of AMs to design rapid-effecting vaccine.

Sirtuin 2 enhances allergic asthmatic inflammation

Allergic eosinophilic asthma is a chronic condition causing airway remodeling resulting in lung dysfunction. We observed that expression of sirtuin 2 (Sirt2), a histone deacetylase, regulates the recruitment of eosinophils after sensitization and challenge with a triple antigen: dust mite, ragweed, and Aspergillus fumigatus (DRA). Our data demonstrate that IL-4 regulates the expression of Sirt2 isoform 3/5. Pharmacological inhibition of Sirt2 by AGK2 resulted in diminished cellular recruitment, decreased CCL17/TARC, and reduced goblet cell hyperplasia. YM1 and Fizz1 expression was reduced in AGK2-treated, IL-4-stimulated lung macrophages in vitro as well as in lung macrophages from AGK2-DRA-challenged mice. Conversely, overexpression of Sirt2 resulted in increased cellular recruitment, CCL17 production, and goblet cell hyperplasia following DRA challenge. Sirt2 isoform 3/5 was upregulated in primary human alveolar macrophages following IL-4 and AGK2 treatment, which resulted in reduced CCL17 and markers of alternative activation. These gain-of-function and loss-of-function studies indicate that Sirt2 could be developed as a treatment for eosinophilic asthma.

IL-36γ Protects against Severe Influenza Infection by Promoting Lung Alveolar Macrophage Survival and Limiting Viral Replication

Although influenza virus infection remains a concerning disease for public health, the roles of individual cytokines during the immune response to influenza infection are not fully understood. We have identified IL-36γ as a key mediator of immune protection during both high- and low-pathogenesis influenza infection. Il36g mRNA is upregulated in the lung following influenza infection, and mice lacking IL-36γ have greatly increased morbidity and mortality upon infection with either H1N1 or H3N2 influenza. The increased severity of influenza infection in IL-36γ-knockout (KO) mice is associated with increased viral titers, higher levels of proinflammatory cytokines early in infection, and more diffuse pathologic conditions late in the disease course. Interestingly, the increased severity of disease in IL-36γ-KO mice correlates with a rapid loss of alveolar macrophages following infection. We find that the alveolar macrophages from naive IL-36γ-KO mice have higher expression of M2-like surface markers compared with wild-type (WT) mice and show increased apoptosis within 24 h of infection. Finally, transfer of WT alveolar macrophages to IL-36γ-KO mice restores protection against lethal influenza challenge to levels observed in WT mice. Together, these data identify a critical role for IL-36γ in immunity against influenza virus and demonstrate the importance of IL-36γ signaling for alveolar macrophage survival during infection.

Functionalized synchrotron in-line phase-contrast computed tomography: a novel approach for simultaneous quantification of structural alterations and localization of barium-labelled alveolar macrophages within mouse lung samples

Functionalized computed tomography (CT) in combination with labelled cells is virtually non-existent due to the limited sensitivity of X-ray-absorption-based imaging, but would be highly desirable to realise cell tracking studies in entire organisms. In this study we applied in-line free propagation X-ray phase-contrast CT (XPCT) in an allergic asthma mouse model to assess structural changes as well as the biodistribution of barium-labelled macrophages in lung tissue. Alveolar macrophages that were barium-sulfate-loaded and fluorescent-labelled were instilled intratracheally into asthmatic and control mice. Mice were sacrificed after 24 h, lungs were kept in situ, inflated with air and scanned utilizing XPCT at the SYRMEP beamline (Elettra Synchrotron Light Source, Italy). Single-distance phase retrieval was used to generate data sets with ten times greater contrast-to-noise ratio than absorption-based CT (in our setup), thus allowing to depict and quantify structural hallmarks of asthmatic lungs such as reduced air volume, obstruction of airways and increased soft-tissue content. Furthermore, we found a higher concentration as well as a specific accumulation of the barium-labelled macrophages in asthmatic lung tissue. It is believe that XPCT will be beneficial in preclinical asthma research for both the assessment of therapeutic response as well as the analysis of the role of the recruitment of macrophages to inflammatory sites.

A novel approach to restore lung immunity during systemic immunosuppression

Systemic immunosuppression accounts for significant morbidity and mortality worldwide. Pulmonary infections represent the most common cause of death in these patients. The resident inflammatory cell in the lung is the alveolar macrophage (AM) and its function is markedly diminished by immunosuppression. We hypothesized that AMs from normal mice with or without gene transfer of the gamma interferon gene inside the macrophages, can restore alveolar immunity in immunosuppressed mice with severe combined immunodeficiency syndrome (SCID). To test this hypothesis we intratracheally instilled normal and IFN-gamma activated macrophages to the lungs of SCID mice. We demonstrated that airway delivery of macrophages results in widespread alveolar distribution, improved phagocytic function and ability to clear opportunistic infections such as Pneumocystis carinii. Airway delivery of IFN-gamma expressing macrophages further increased the function of alveolar macrophages. Reconstitution of the lungs of immunosuppressed mice with normal or activated AMs can restore alveolar immunity despite ongoing systemic immunosuppression.

Adoptive transfer of alveolar macrophages abrogates bronchial hyperresponsiveness

Increasing evidence suggests that alveolar macrophages (AM) are involved in asthma pathogenesis. To better understand the role that these cells play, we investigated the capacity of AM from allergy-resistant rat, Sprague Dawley (SD), to modulate airway hyperresponsiveness of allergy-susceptible rat, Brown Norway (BN). AM of ovalbumin (OVA)-sensitized BN rats were eliminated by intratracheal instillation of liposomes containing clodronate. AM from OVA-sensitized SD rats were transferred into AM-depleted BN rats 24 h before allergen challenge. Airway responsiveness to methacholine was measured the following day. Instillation of liposomes containing clodronate in BN rats eliminated 85% AM after 3 d compared with saline liposomes. Methacholine concentration needed to increase lung resistance by 200% (EC200RL) was significantly lower in OVA-challenged BN rats (27.9 +/- 2.8 mg/ml) compared with SD rats (63.9 +/- 8.6 mg/ml). However, when AM from SD rats were transferred into AM-depleted BN rats, airway responsiveness (64.0 +/- 11.3 mg/ml) was reduced to the level of naïve rats (54.4 +/- 3.7 mg/ml) in a dose-dependent manner. Interestingly, transfer of AM from BN rats into SD rats did not modulate airway responsiveness. To our knowledge, this is the first direct evidence showing that AM may protect against the development of airway hyperresponsiveness.

Defective Phagocytosis and Clearance ofPseudomonas aeruginosain the Lung Following Bone Marrow Transplantation

Bone marrow transplantation (BMT) is an important therapeutic option for a variety of malignant and nonmalignant disorders. Unfortunately, BMT recipients are at increased risk of infection, and in particular, pulmonary complications occur frequently. Although the risk of infection is greatest during the neutropenic period immediately following transplant, patients are still vulnerable to pulmonary infections even after neutrophil engraftment. We evaluated the risk of infection in this postengraftment period by using a well-established mouse BMT model. Seven days after syngeneic BMT, B6D2F(1) mice are no longer neutropenic, and by 3 wk, they demonstrate complete reconstitution of the peripheral blood. However, these mice remain more susceptible throughout 8 wk to infection after intratracheal administration of Pseudomonas aeruginosa; increased mortality in the P. aeruginosa-infected BMT mice correlates with increased bacterial burden in the lungs as well as increased systemic dissemination. This heightened susceptibility to infection was not secondary to a defect in inflammatory cell recruitment to the lung. The inability to clear P. aeruginosa in the lung correlated with reduced phagocytosis of the bacteria by alveolar macrophages (AMs), but not neutrophils, decreased production of TNF-alpha by AMs, and decreased levels of TNF-alpha and IFN-gamma in the bronchoalveolar lavage fluid following infection. Expression of the beta(2) integrins CD11a and CD11c was reduced on AMs from BMT mice compared with wild-type mice. Thus, despite restoration of peripheral blood count, phagocytic defects in the AMs of BMT mice persist and may contribute to the increased risk of infection seen in the postengraftment period.

Morphologic detection and functional assessment of reconstituted normal alveolar macrophages in the lungs of SCID mice

Alveolar macrophages (AMs) from immunocompetent animals were isolated from bronchoalveolar lavage and labeled with the fluorescent marker 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI). These AMs were administered intratracheally into mechanically ventilated SCID mice. From 1 to 28 days later, the recipient mice underwent bronchoalveolar lavage to isolate their AMs. To determine whether reconstituted AMs were still immunocompetent, the recovered AMs were assayed for their ability to phagocytose fluorescein-labeled zymosan-coated beads. After incubation with the beads, samples were assayed using a fluorescent-activated cell sorter to identify DiI-labeled reconstituted AMs, unlabeled resident AMs, and the proportion of these two groups undergoing phagocytosis. DiI-labeled AMs accounted for approximately 50% of all returned AMs. Additionally, the reconstituted AMs from normal BALB/c mice retained phagocytic activity compared with AMs from immunodeficient SCID mice. Reconstituted AMs demonstrated enhanced phagocytic activity compared with resident SCID AMs for up to 28 days following reconstitution. These results indicate that immunocompetent AMs can be successfully reconstituted into an immunodeficient host to partially restore alveolar host defense.

Early chimerism of macrophages and lymphocytes in lung transplant recipients is predictive of graft tolerance

BACKGROUND

The persistence of donor cells derived from the graft (chimerism) has been documented in various tissues after organ transplantation. It was suggested that stable chimerism might reflect a state of donor-specific tolerance. Chimerism of macrophages and lymphocytes were studied over time after lung transplantation as well as its impact on graft tolerance.

MATERIAL AND METHODS

Macrophages and lymphocytes were purified from bronchoalveolar lavage sequentially obtained from 24 patients between 1 and 41 months posttransplantation (20, 22, 24, and 17 patients at, respectively, 1, 3, 6, and 12 months). DNA was extracted from these cells and their recipient-donor origin was evaluated by PCR amplification of highly polymorphic DNA regions (minisatellites).

RESULTS

We show that the remaining donor cells over the first month vary from 10 up to 50% and 5 up to 55% for lymphocytes and macrophages respectively (+/-2 SD). All patients presented some chimerism up to the 6th postoperative month. Good correlation was observed between the residual amount of donor lymphocytes and macrophages during the first 3 months (P<0.001). Patients with at least 30% donor lymphocytes at 1 month after transplantation had less rejections (> or =stage II) in the follow up (P=0.0007). The same observation is true for donor macrophages although to lower extend (P=0.02). The chimerism lost its predictive value beyond 3 months.

CONCLUSIONS

These data demonstrate that a level of chimerism above 30% of either donor lymphocytes or macrophages at 1 month is related to a better state of graft tolerance. However, chimerism decreases markedly beyond 3 months and has then no predictive value.

Macrophages transfected with adenovirus to express IL-4 reduce inflammation in experimental glomerulonephritis

Nephrotoxic nephritis (NTN) is characterized by acute macrophage-dependent inflammation and serves as a model of human glomerulonephritis. In this study we have transfected rat macrophages with recombinant adenovirus expressing IL-4 (Ad-IL4) and demonstrated that these transfected macrophages develop fixed properties as a result of transfection, as shown by reduced NO production in response to IFN-gamma and TNF. Ad-IL4-transfected macrophages localized with enhanced efficiency to inflamed glomeruli after renal artery injection in rats with NTN compared with adenovirus expressing beta-galactosidase (Ad-beta gal)-transfected macrophages and produced elevated levels of the cytokine in glomeruli in vivo for up to 4 days. The delivery of IL-4-expressing macrophages produced a marked reduction in the severity of albuminuria (day 2 albuminuria, 61 +/- 15 mg/24 h) compared with unmodified NTN (day 2 albuminuria, 286 +/- 40 mg/24 h; p < 0.01), and this was matched by a reduction in the number of ED1-positive macrophages infiltrating the glomeruli. Interestingly, the injection of IL-4-expressing macrophages into single kidney produced a marked reduction in the numbers of ED1-positive macrophages in the contralateral noninjected kidney, an effect that could not be mimicked by systemic delivery of IL-4-expressing macrophages. This implies that the presence of IL-4-expressing macrophages in a single kidney can alter the systemic development of the inflammatory response. Macrophage transfection and delivery provide a valuable system to study and modulate inflammatory disease and highlight the feasibility of macrophage-based gene therapy.

Th type 1-stimulating activity of lung macrophages inhibits Th2-mediated allergic airway inflammation by an IFN-gamma-dependent mechanism

In the mucosal immune system, resident dendritic cells are specialized for priming Th2-polarized immunity, whereas the Ag-presenting activity of macrophages has been linked with the development of Th1 phenotype. As an immune switch toward Th1 can protect against Th2-mediated allergic response, this study investigated the capacity of lung macrophages to stimulate Th1 responses during the secondary exposure to inhaled allergen, thereby suppressing Th2-mediated allergic airway inflammation in a murine model of allergic asthma. Following airway macrophage depletion in OVA-sensitized mice, lung T cells defaulted to a phenotype that produced less Th1 (IFN-gamma) and more Th2 (IL-4 and IL-5) cytokines, leading to more severe airway hyperreactivity and inflammation after intranasal Ag challenge. After OVA pulsing and adoptive transfer, lung macrophages selectively promoted a Th1 response in Ag-sensitized recipients and did not induce pulmonary eosinophilia. By contrast, OVA pulsing and adoptive transfer of a lung cell preparation, consisting of dendritic cells, B cells, and macrophages, promoted a Th2 response with an associated inflammatory response that was suppressed when macrophages were present and pretreated with IFN-gamma, but exacerbated when macrophages were depleted before IFN-gamma treatment. In addition, Th1-promoting activity of lung macrophages was not related to the autocrine production of IL-12p40. These results suggest that the Th1-promoting APC activity may be an inherent property of the lung macrophage population, and may play an important role, upon stimulation by IFN-gamma, in antagonizing an ongoing Th2 immunity and Th2-dependent allergic responses.

Adoptive transfer of acute lung injury

In this study, we describe a novel adoptive transfer protocol to study acute lung injury in the rat. We show that bronchoalveolar lavage (BAL) cells isolated from rats 5 h after intratracheal administration of lipopolysaccharide (LPS) induce a lung injury when transferred to normal control recipient rats. This lung injury is characterized by increased alveolar-arterial oxygen difference and extravasation of Evans blue dye (EBD) into lungs of recipient rats. Recipient rats receiving similar numbers of donor cells isolated from healthy rats do not show adverse changes in the alveolar-arterial oxygen difference or in extravasation of EBD. The adoptive transfer-induced lung injury is associated with increased numbers of neutrophils in the BAL, the levels of which are similar to the numbers observed in BAL cells isolated from rats treated for 5 h with LPS. As an indicator of BAL cell activation, donor BAL cell inducible nitric oxide synthase (iNOS) expression was compared with BAL cell iNOS expression 48 h after adoptive transfer. BAL cells isolated 5 h after LPS administration expressed iNOS immediately after isolation. In contrast, BAL cells isolated 48 h after adoptive transfer did not express iNOS immediately after isolation but expressed iNOS following a 24-h ex vivo culture. These findings indicate that the activation state of donor BAL cells differs from BAL cells isolated 48 h after adoptive transfer, suggesting that donor BAL cells may stimulate migration of new inflammatory cells into the recipient rats lungs.

[A treatment method for patients with a local suppurative infection]

To treat patients with the post-injection abscess and mastitis, suspension of alveolar porcine macrophages was periodically introduced via a drainage tube into the cavity formed after sparing opening of an abscess and removal of necrotic tissues. Local use of the substance permitted to shorten by 30-50% the duration of hospital stay of the patients as compared to that in use of conventional methods.

The origin of alveolar macrophages in the transplanted lung: a longitudinal microsatellite-based study of donor and recipient DNA

Transplanted lungs are initially populated by donor pulmonary alveolar macrophages (PAMs). These will form major antigen presenters for the recipient's suppressed immune system. They may be expected to be replaced by recipient major histocompatibility complex-compatible cells, with time. We have isolated CD14+ PAMs from bronchoalveolar lavage specimens for 6 months after transplantation and identified their origin by using microsatellite analysis. This DNA-based technology permits the reliable identification of the origin of cells from different individuals. We show that replacement of donor PAMs occurs with individual dynamics in each case. Recipient PAMs usually appeared within 2 weeks, whereas donor cells could be retained for as long as 6 months. In this limited series, there was no obvious correlation between the dynamics of this process and the occurrence of rejection episodes or infections.

Pulmonary immunity to Listeria is enhanced by elimination of alveolar macrophages

To determine how resident alveolar macrophages (AM) regulate the antigen-presenting-cell (APC) activities of pulmonary dendritic cells (DC) in the response to particulate antigen, we pretreated Lewis rats intratracheally with liposomes containing clodronate (LIP-CLOD), which eliminated AM in vivo. Controls received saline encapsulated in liposomes (LIP-SAL) or saline alone intratracheally. At Day 3, rats were injected intratracheally with 1 x 10(7) heat-killed Listeria (HKL) and DC purified from lung were examined for their ability to stimulate HKL-immune T cells without added HKL. Only DC from LIP-CLOD-treated rats displayed enhanced APC activities for HKL. A second intratracheal HKL challenge at Day 14 yielded lymphocytic cuffing of the microvasculature in LIP-CLOD-treated lungs only. Intratracheal adoptive transfer of normal syngeneic AM into LIP-CLOD-treated rats suppressed APC activities of DC in vitro and the lymphocytic response in vivo. Bronchoalveolar macrophages from rats treated with LIP-CLOD and HKL showed decreased production of nitric oxide (NO), a potent suppressor of DC and T-helper 1 lymphocyte activities as compared with those of controls. We conclude that eliminating AM in vivo reduces local production of NO and promotes pulmonary cell-mediated immunity to HKL.

In vitro and in vivo enhancement of canine pulmonary alveolar macrophage cytotoxic activity against canine osteosarcoma cells

The combination of chemotherapy with immunotherapy may offer an advantage over either therapy alone and provide a greater potential for total tumor eradication. Monocyte/macrophage-mediated tumor cell killing is a major mechanism of the host's defense against primary and/or metastatic neoplasia. We evaluated the tumoricidal activity against canine osteosarcoma cells of canine pulmonary alveolar macrophages (PAM) exposed in vitro to two recombinant canine (rc) cytokines (rcTNF alpha and rcIFN gamma). We also evaluated the in vivo tumoricidal activity of PAM from dogs treated with the macrophage activator, liposome-encapsulated muramyl tripeptide-phosphatidyl-ethanolamine (L-MTP-PE) alone or in combination with doxorubicin (DOX). This study demonstrated that rcTNF alpha and rcIFN gamma significantly enhance in vitro canine PAM cytotoxicity against canine osteosarcoma cells, and that PAM from dogs treated with DOX + L-MTP-PE have enhanced cytotoxic activity against osteosarcoma cells when compared to dogs treated with DOX or L-MTP-PE alone. These findings support the rationale for combining a chemotherapy agent with an immunotherapy agent for the treatment of metastatic disease, and suggest a role for TNF alpha and IFN gamma as agents for stimulating the antitumor activity of macrophages.

Selective expansion of alveolar macrophages in vivo by adenovirus-mediated transfer of the murine granulocyte-macrophage colony-stimulating factor cDNA

Based on the hypothesis that genetic modification of freshly isolated alveolar macrophages (AM) with the granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA would induce AM to proliferate, this study focuses on the ability of adenoviral (Ad) vectors to transfer and efficiently express the murine (m) GM-CSF cDNA in murine AM with consequent expansion in the number of AM in vitro and in vivo. To demonstrate that an Ad vector can effectively transfer and express genes in AM, murine AM recovered by bronchoalveolar lavage from the lung of Balb/c mice were infected with an Ad vector coding for green fluorescent protein (GFP) in vitro and expressed GFP in a dose-dependent fashion. Infection of AM with an Ad vector containing an expression cassette coding for mGM-CSF led to GM-CSF expression and to AM proliferation in vitro. When AM infected with AdGFP were returned to the respiratory tract of syngeneic recipient mice, GFP-expressing cells could still be recovered by bronchoalveolar lavage 2 weeks later. In vitro infection of AM with AdmGM-CSF and subsequent transplantation of the genetically modified AM to the lungs of syngeneic recipients led to GM-CSF expression in vivo. Strikingly, the AM recovered by lavage 5 weeks after transplantation demonstrated an increased rate of proliferation, and the total number of alveolar macrophages was 1. 9-fold greater than controls. Importantly, the increase in the numbers of AM was selective (ie, other inflammatory cell numbers were unchanged), and there was no modification to the lung architecture. Thus, it is feasible to genetically modify AM with Ad vectors and to use this strategy to modify the behavior of AM in vivo. Based on the importance of AM in the primary defense of the respiratory epithelial surface, this strategy may be useful in enhancing pulmonary defenses in immunodeficiency states.

Instillation of allogeneic lung macrophages and dendritic cells cause differential effects on local IFN-gamma production, lymphocytic bronchitis, and vasculitis in recipient murine lungs

Lung allograft rejection is believed to be initiated by donor lung accessory cells, namely macrophages and dendritic cells, interacting with recipient lymphocytes leading to up-regulated Th1 type (IFN-gamma) cellular immunity culminating in graft destruction. The purpose of this study was to determine the individual role of donor lung macrophages and dendritic cells in the rejection response. Utilizing a murine model that reproduces the immunology and histology of acute rejection, C57BL/6 mouse (I-a(b), H-2(b)) lung dendritic cells (DC-enriched lung cells), purified alveolar macrophages (I-a-negative macrophages), or various ratios of I-a-negative macrophages/DC were instilled into BALB/c mouse (I-a(d), H-2(d)) lungs followed by an assessment of local IFN-gamma production and grading of rejection pathology. The data show that DC, and not I-a-negative macrophages, induced IFN-gamma production in recipient lungs. However, the local production of IFN-gamma was not always associated with histological changes characteristic of rejection pathology. In contrast to either cell type alone, instillation of C57BL/6 I-a-negative macrophages and DC, together, were required to induce rejection pathology in BALB/c lungs. In addition, the rejection response was dependent on interactions between donor I-a-negative macrophages and DC.