Effect of MMR Vaccination to Mitigate Severe Sequelae Associated With COVID-19: Challenges and Lessons Learned

Mortality in COVID-19 cases was strongly associated with progressive lung inflammation and eventual sepsis. There is mounting evidence that live attenuated vaccines commonly administered during childhood, also provide beneficial non-specific immune effects, including reduced mortality and hospitalization due to unrelated infections. It has been proposed that live attenuated vaccine-associated non-specific effects are a result of inducing trained innate immunity to function more effectively against broader infections. In support of this, our laboratory has reported that immunization with a live attenuated fungal strain induces a novel form of trained innate immunity which provides protection against various inducers of sepsis in mice via myeloid-derived suppressor cells. Accordingly, we initiated a randomized control clinical trial with the live attenuated Measles, Mumps, Rubella (MMR) vaccine in healthcare workers in the greater New Orleans area aimed at preventing/reducing severe lung inflammation/sepsis associated with COVID-19 (ClinicalTrials.gov Identifier: NCT04475081). Included was an outcome to evaluate the myeloid-derived suppressor cell populations in blood between those administered the MMR vaccine vs placebo. The unanticipated emergency approval of several COVID-19 vaccines in the midst of the MMR clinical trials eliminated the ability to examine effects of the MMR vaccine on COVID-19-related health status. Unfortunately, we were also unable to show any impact of the MMR vaccine on peripheral blood myeloid-derived suppressor cells due to several inherent limitations (low percentages of blood leukocytes, small sample size), that also included a collaboration with a similar trial (CROWN CORONATION; ClinicalTrials.gov Identifier: NCT04333732) in St. Louis, MO. In contrast, monitoring the COVID-19 vaccine response in trial participants revealed that high COVID-19 antibody titers occurred more often in those who received the MMR vaccine vs placebo. While the trial was largely inconclusive, lessons learned from addressing several trial-associated challenges may aid future studies that test the non-specific beneficial immune effects of live attenuated vaccines.

ISGylation is increased in the peripheral blood mononuclear cells derived from symptomatic COVID-19 patients

Cytokine-driven hyper inflammation has been identified as a critical factor behind poor outcomes in patients severely infected with SARS-CoV-2 virus. Notably, protein ISGylation, a protein conjugated form of Type 1 IFN-inducible ubiquitin-like protein ISG15 (Interferon-Stimulated Gene 15), induces cytokine storm (CS) and augments colonic inflammation in colitis-associated colon cancers in mouse models. However, whether ISGylation is increased and causally responsible for CS and hyper inflammation in symptomatic COVID-19 patients is unknown. Here, we measured ISGylation levels in peripheral blood mononuclear cells (PBMCs) from 10 symptomatic (SARS-CoV-2-positive with symptoms) and asymptomatic (SARS-CoV-2-positive with no symptoms) COVID-19 patients, and 4 uninfected individuals (SARS-CoV-2-negative), using Wes^Tm assay. Strikingly, we note significant increases in protein ISGylation and MX-1 (myxovirus-resistance protein-1) protein levels, both induced by type-I IFN, in symptomatic but not in asymptomatic patients and uninfected individuals. Knowing that ISGylation augments CS and intestinal inflammation in colon cancers, we propose that increased ISGylation may be an underlying cause of CS and inflammation in symptomatic patients.

Treatment with intranasal iloprost reduces disease manifestations in a murine model of previously established COPD

Pulmonary endothelial prostacyclin appears to be involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). The effect of treatment with a prostacyclin analog in animal models of previously established COPD is unknown. We evaluated the short- and long-term effect of iloprost on inflammation and airway hyperresponsiveness (AHR) in a murine model of COPD. Nineteen mice were exposed to LPS/elastase, followed by either three doses of intranasal iloprost or saline. In the long-term treatment experiment, 18 mice were exposed to LPS/elastase and then received 6 wk of iloprost or were left untreated as controls. In the short-term experiment, iloprost did not change AHR but significantly reduced serum IL-5 and IFN-γ. Long-term treatment with iloprost for both 2 and 6 wk significantly improved AHR. After 6 wk of iloprost, there was a reduction in bronchoalveolar lavage (BALF) neutrophils, serum IL-1β (30.0 ± 9.2 vs. 64.8 ± 7.4 pg/ml, P = 0.045), IL-2 (36.5 ± 10.6 vs. 83.8 ± 0.4 pg/ml, P = 0.01), IL-10 (75.7 ± 9.3 vs. 96.5 ± 3.5 pg/ml, P = 0.02), and nitrite (15.1 ± 5.4 vs. 30.5 ± 10.7 μmol, P = 0.01). Smooth muscle actin (SMA) in the lung homogenate was also significantly reduced after iloprost treatment (P = 0.02), and SMA thickness was reduced in the small and medium blood vessels after iloprost (P < 0.001). In summary, short- and long-term treatment with intranasal iloprost significantly reduced systemic inflammation in an LPS/elastase COPD model. Long-term iloprost treatment also reduced AHR, serum nitrite, SMA, and BALF neutrophilia. These data encourage future investigations of prostanoid therapy as a novel treatment for COPD patients.

Flagellin has differential and route-dependent adjuvant effects when encoded in heterologous systemic or mucosal gene-based prime-boost vaccines (VAC4P.1107)

Flagellin has been tested as a protein-based adjuvant, with most studies focused on antibody responses. In this study, we have evaluated the adjuvant activity of flagellin for cellular and humoral immune responses in gene-based immunizations. DNA and adenovirus (Ad) vectors were constructed to encode mycobacterial Ag85B and/or flagellin (FliC) of S. typhimurium. DNA-encoded flagellin given to mice via the IM route enhanced antigen-specific splenic CD4+ and CD8+ T cell responses. Boosting either IM or intranasally (IN) with Ad vectors expressing Ag85B without flagellin enhanced antigen-specific antibody and CD4+ and CD8+ T cell responses in both spleen and pulmonary tissues, correlating with improved protection against pulmonary challenge with Mtb. However, inclusion of flagellin in both DNA prime and Ad boosting vaccines induced localized pulmonary inflammation and transient weight loss, along with route-dependent effects on vaccine-induced T cell immunity. The latter included marked reductions in mucosal CD4+ and CD8+ T cell responses following IM DNA / IN Ad prime-boosting, although antibody responses were not diminished. These findings suggest that flagellin has differential and route-dependent adjuvant activity when included in systemic or mucosal gene-based prime-boost immunization. Adjuvant activity for both T and B cell responses and safety were optimal when flagellin was included only in the DNA vaccine priming phase of systemic or mucosal DNA/Ad prime-boosting.

Mediastinal pleomorphic sarcoma in an immunodeficient patient: case report and review of the literature

Pleomorphic sarcoma, widely known as malignant fibrous histiocytoma (MFH), is a soft tissue sarcoma. The occurrence of this malignancy in the mediastinum is rare. To our knowledge, only 13 cases of MFH of the mediastinum have been previously reported. Furthermore, only three cases of MFH in patients infected with human immunodeficiency virus (HIV) have been previously described. Here we present a 44-year-old African-American male who complained of epigastric pain radiating to the right chest. On admission, a chest radiograph revealed a widened mediastinum, and chest computerized tomography (CT) identified a large mass in the posterior mediastinum. Histologic diagnosis revealed a high-grade MFH. He was also incidentally diagnosed with HIV infection. The rarity of this malignancy and uncommon site of presentation in association with an immunodeficient state makes this case unique. This is the first report in the literature of an HIV-infected patient presenting with this uncommon tumor in the mediastinum.

CD4+ lymphocyte responses to pulmonary infection with Mycobacterium tuberculosis in naïve and vaccinated BALB/c mice

The Biostack experiments I and II were flown on board the Apollo 16 and 17 command modules in order to obtain information on the biological damage produced by the bombardment of heavy high-energy (HZE) particles of cosmic radiation during spaceflight. Such data are required for estimating radiation hazards in manned spaceflight. Seven biological systems in resting state (Bacillus subtilis spores, Colpoda cucullus cysts, Arabidopsis thaliana seeds, and eggs of Artemia salina, Tribolium castaneum and of Carausius morosus) were accommodated in the two Biostacks. By using a special sandwich construction of visual track detectors and layers of biological objects, identification of each hit biological object was achieved and the possible biological damage correlated with the physical features of the responsible HZE-particle. In the different systems the degree of damage depended on whether the hit cell was replaceable or not. A high sensitivity to HZE-particle bombardment was observed on Artemia salina eggs; 90% of the embryos, which were induced to develop from hit eggs, died at different developmental stages. Malformations of the abdomen or the extremities of the nauplius were frequently induced. In contrast, the growth of hit Vicia faba radiculae and the germination of hit Arabidopsis thaliana seeds and hit Bacillus subtilis spores were not influenced remarkably. But there was an increase in multicaulous plants and a reduction in the outgrowth of the bacteria] spores. In addition, information was obtained on the fluence of the HZE-particles, on their spectrum of charge and energy loss, and on the absorption by the Apollo spacecraft and the Biostack material itself. This will help to improve knowledge concerning radiation conditions inside of spacecrafts, necessary to secure a The Biostack experiments I and II were flown on board the Apollo 16 and 17 command modules in order to obtain information on the biological damage produced by the bombardment of heavy high-energy (HZE) particles of cosmic radiation during spaceflight. Such data are required for estimating radiation hazards in manned spaceflight. Seven biological systems in resting state (Bacillus subtilis spores, Colpoda cucullus cysts, Arabidopsis thaliana seeds, and eggs of Artemia salina, Tribolium castaneum and of Carausius morosus) were accommodated in the two Biostacks. By using a special sandwich construction of visual track detectors and layers of biological objects, identification of each hit biological object was achieved and the possible biological damage correlated with the physical features of the responsible HZE-particle. In the different systems the degree of damage depended on whether the hit cell was replaceable or not. A high sensitivity to HZE-particle bombardment was observed on Artemia salina eggs; 90% of the embryos, which were induced to develop from hit eggs, died at different developmental stages. Malformations of the abdomen or the extremities of the nauplius were frequently induced. In contrast, the growth of hit Vicia faba radiculae and the germination of hit Arabidopsis thaliana seeds and hit Bacillus subtilis spores were not influenced remarkably. But there was an increase in multicaulous plants and a reduction in the outgrowth of the bacteria] spores. In addition, information was obtained on the fluence of the HZE-particles, on their spectrum of charge and energy loss, and on the absorption by the Apollo spacecraft and the Biostack material itself. This will help to improve knowledge concerning radiation conditions inside of spacecrafts, necessary to secure a The Biostack experiments I and II were flown on board the Apollo 16 and 17 command modules in order to obtain information on the biological damage produced by the bombardment of heavy high-energy (HZE) particles of cosmic radiation during spaceflight. Such data are required for estimating radiation hazards in manned spaceflight. Seven biological systems in resting state (Bacillus subtilis spores, Colpoda cucullus cysts, Arabidopsis thaliana seeds, and eggs of Artemia salina, Tribolium castaneum and of Carausius morosus) were accommodated in the two Biostacks. By using a special sandwich construction of visual track detectors and layers of biological objects, identification of each hit biological object was achieved and the possible biological damage correlated with the physical features of the responsible HZE-particle. In the different systems the degree of damage depended on whether the hit cell was replaceable or not. A high sensitivity to HZE-particle bombardment was observed on Artemia salina eggs; 90% of the embryos, which were induced to develop from hit eggs, died at different developmental stages. Malformations of the abdomen or the extremities of the nauplius were frequently induced. In contrast, the growth of hit Vicia faba radiculae and the germination of hit Arabidopsis thaliana seeds and hit Bacillus subtilis spores were not influenced remarkably. But there was an increase in multicaulous plants and a reduction in the outgrowth of the bacteria] spores. In addition, information was obtained on the fluence of the HZE-particles, on their spectrum of charge and energy loss, and on the absorption by the Apollo spacecraft and the Biostack material itself. This will help to improve knowledge concerning radiation conditions inside of spacecrafts, necessary to secure a maximum possible protection to the astronauts.

Pulmonary hypertension associated with HIV infection

Pulmonary hypertension occurs with increased frequency among patients with human immunodeficiency virus (HIV) infection. Although the pathogenesis of HIV-associated pulmonary hypertension remains unknown, it appears to occur independently of other risk factors associated with pulmonary vasculopathy, such as chronic hepatitis C infection and intravenous drug use. Signs and symptoms are typical of those immunocompetent patients with primary pulmonary hypertension, but because many HIV-infected patients are receiving intensive medical supervision, the diagnosis of pulmonary hypertension is often made at an earlier stage. Acute responses to epoprostenol are similar to those among non-HIV-infected individuals, but the benefits of long-term, intravenous treatment with epoprostenol in HIV-infected patients is unknown. Future investigations should define the true incidence of pulmonary hypertension and the long-term effects of epoprostenol on survival among HIV-infected individuals. Physicians should be alert to possible pulmonary hypertension in persons infected with HIV.

Phase 1 safety trial of Filgrastim (r-metHuG-CSF) in non-neutropenic patients with severe community-acquired pneumonia

The objectives of the present study were to: (1) evaluate the safety of Filgrastim therapy in non-neutropenic patients with severe community-acquired pneumonia; (2) determine the absolute neutrophil count (ANC) response to various dosages of Filgrastim in non-neutropenic patients with active infection; and (3) describe the impact of therapy with Filgrastim in combination with antibiotics on selected pneumonia-related clinical parameters. The study design was an open-label, dose-ranging, clinical trial, set in the General Clinical Research Unit of a large, public community hospital. The study population consisted of 30 patients who had presented to the Emergency Department with severe, community-acquired pneumonia. One of five dosages (75, 150, 300, 450 or 600 micrograms day-1) of Filgrastim (r-metHuG-CSF) was given subcutaneously daily for 10 days, until discharge or until the absolute neutrophil count > 75 x 10(9) l(-1), whichever was earlier. Vital signs, pulse oximetry, arterial blood gases, daily complete blood counts with differential, serum chemistries, coagulation profiles, electrocardiograms, chest radiographs, plasma G-CSF concentrations and duration of hospitalization were measured. There was no evidence of Filgrastim-related lung injury or evidence of extra-pulmonary toxicity. There was no apparent dose-response effect of Filgrastim on pneumonia-related clinical variables. Dosages of Filgrastim between 150 and 600 micrograms day-1 had similar effects on increasing the ANC. Filgrastim appeared to be safe in non-neutropenic patients with severe, community-acquired pneumonia when given in dosages of 75-600 micrograms day-1 in combination with appropriate antibiotic therapy. Further study is needed to determine the effect of Filgrastim on morbidity, mortality and duration of symptoms in this patient population.

Exacerbation of murine Pneumocystis carinii infection by adenoviral-mediated gene transfer of a TNF inhibitor

The role of mononuclear phagocytes and their cytokine products in host defense against Pneumocystis carinii (PC) remains unclear. The cytokine tumor necrosis factor (TNF) has been proposed as critical for host defense against this pathogen. To investigate the role of this cytokine in PC infection, we treated immunocompetent mice (CD4+) or mice depleted of CD4 lymphocytes (CD4-) with a recombinant adenovirus encoding a TNF inhibitor gene (AdTNF-R). AdTNF-R treated CD4+ animals displayed delayed clearance of PC after intratracheal inoculation, whereas AdTNF-R treated CD4 animals developed more severe chronic infection. Moreover, AdTNF-R treated CD4- animals, in contrast to control CD4- mice, failed to show any interleukin-6 (IL-6) gene induction in the lung after PC challenge. The results firmly implicate TNF in host defense against PC, and support a role for TNF in orchestrating the intrapulmonary cytokine cascade in PC infection.

Update: HIV infection and pulmonary host defenses

Infection with the human immunodeficiency virus (HIV) produces profound alterations in host defense mechanisms throughout the respiratory tract. The extent of alteration of specific defenses varies with the stage or duration of HIV infection in the host. In the upper respiratory tract, HIV-infected individuals have decreased concentrations of salivary immunoglobulin A, which may predispose to colonization of the oropharynx with pathogenic microorganisms. In the lower respiratory tract, host defenses are provided by alveolar macrophages, lymphocytes, and polymorphonuclear leukocytes. Alveolar macrophages can be chronically infected with HIV, and demonstrate a number of compromised host defense functions. The HIV-infected host has a limited capacity to generate soluble signals necessary for activation of alveolar macrophages for microbial killing. CD4 lymphocytes, which are quantitatively depleted during HIV infection, also demonstrate qualitative defects. Proliferation of CD8 lymphocytes, directed against HIV-infected cells in the lung, is associated with the noninfectious pulmonary complications of acquired immunodeficiency syndrome. B lymphocytes from HIV-infected persons show deficient production of opsonizing antibodies, which may predispose to bacterial pneumonias. Defective responses of polymorphonuclear leukocytes in the lung are also likely to contribute to impaired host responses. Collectively, these multiple defects in the defense mechanisms of the respiratory tract explain the unique susceptibility of the HIV-infected host for opportunistic pulmonary infections.

Alveolar macrophage release of tumor necrosis factor during murine Pneumocystis carinii pneumonia

Tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine produced principally by mononuclear cells, is released in response to a variety of pulmonary pathogens. We hypothesized that release of TNF in the lung is a normal part of the host response to intratracheal challenge with Pneumocystis carinii. To test this hypothesis, we measured TNF in bronchoalveolar lavage fluid (BALF) in normal and CD4-depleted mice at various intervals in acute and chronically infected animals. To assess the cell of origin and the control of TNF release in the lung, we measured mRNA for TNF by a competitive polymerase chain reaction and assessed the capacity of adherence-enriched cells to produce TNF in vitro in response to lipopolysaccharide. Our data demonstrate that TNF peaks at 3 h in both control and CD4-depleted mice after acute challenge with P. carinii and this increase in TNF precedes the influx of inflammatory cells into the lung. TNF levels in BALF return to undetectable levels by day 3. In chronically infected animals, there is a 5-fold increase in mRNA for TNF in adherent cells which is associated with an increased capacity to release TNF in vitro. These data suggest that TNF is a normal host response to P. carinii infection; however, there is no difference in acute TNF release between control animals that clear their infection and CD4-depleted animals that develop chronic infection. TNF is upregulated in chronically infected animals, but CD4 depletion results in the loss of additional host factors essential for resolution of this infection.

Elevated 1,25-dihydroxyvitamin D levels in patients with chronic obstructive pulmonary disease treated with prednisone

Glucocorticoid administration is a well established cause of osteopenia. Mechanisms underlying the deleterious effect of glucocorticoids on bone may include direct inhibition of bone formation as well as indirect effects through changes in intestinal calcium absorption, renal calcium excretion, and/or levels of the calciotropic hormones. To further examine the potential role of the calciotropic hormones we measured serum levels of PTH and 1,25 dihydroxyvitamin D [1,25(OH)2D], as well as serum and urine levels of calcium and vertebral bone density in patients with chronic obstructive pulmonary disease being managed with or without prednisone. Patients treated with prednisone had lower spinal bone density (53 vs. 106 mg/cm3) and higher serum calcium (2.40 vs. 2.33 mmol/l), urine calcium (6.9 vs. 2.7 mmol/24h), and 1,25(OH)2D levels (147 vs. 95 pmol/L). Compared to the patients not treated with glucocorticoids. PTH levels also tended to be higher (33 vs. 26 microliters-eq/ml), but the difference was not significant. Serum and urine calcium levels correlated positively with 1,25(OH)2D levels, but none of these measurements correlated with PTH levels. Our results suggest that prednisone treatment alters the regulation of 1,25(OH)2D production, and this may contribute to the loss of bone mineral induced by prednisone.

Ethanol relaxes pulmonary artery by release of prostaglandin and nitric oxide

Acute-intake of ethanol is associated with vasodilation of vascular smooth muscle (VSM). Relaxation of VSM is dependent, in part, on the actions of nitric oxide (NO) and prostaglandin (PG) produced by endothelial cells (EC) lining the VSM. We examined the effects of endothelium rubbing and inhibition of EC synthesis of NO and PG on ethanol-induced relaxation of bovine pulmonary artery (BPA) and pulmonary vein (BPV) in vitro. Rings of isolated BPA and BPV were mounted in muscle chambers for the isometric recording of force development. Blood vessels were precontracted with an EC50 concentration of the thromboxane receptor mimetic U46619. Ethanol (0.01, 0.02, 0.04, 0.08, 0.16, 0.32, 0.64, and 1.28% (w/v) produced concentration-dependent relaxation of BPA and BPV. Ethanol-induced relaxation was attenuated in BPA with rubbed EC and by the NO synthase inhibitors, L-NG monomethylarginine (LNMMA, 50 microM) and L-nitroarginine (NOLA, 10 microM), and the prostaglandin cyclooxygenase inhibitor, ibuprofen (10 microM). In contrast, ethanol-induced relaxation of BPV was not affected by endothelium rubbing or by NOLA or LNMMA, but was partially attenuated by ibuprofen. Nitric oxide was measured with the chemiluminescence technique. Ethanol increased the content of NO released under basal conditions by the BPA but did not effect basal NO release from BPV. However, ethanol enhanced bradykinin-induced release of NO from BPA and BPV and, at low concentrations, augmented bradykinin-induced relaxation of both BPA and BPV.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pyocyanine, a pigment of Pseudomonas aeruginosa, on production of reactive nitrogen intermediates by murine alveolar macrophages

In this study we investigated the effect of pyocyanine, a pigment produced by Pseudomonas aeruginosa, on production of reactive nitrogen intermediates by macrophages. We found that addition of pyocyanine to cultures of murine alveolar macrophages inhibited the capacity of these cells to produce reactive nitrogen intermediates (measured as nitrite) in a dose-dependent manner without altering cell viability, cytokine-induced Ia expression, or production of tumor necrosis factor.

Lymphocytic interstitial pneumonitis presenting as recurrent pneumothoraces

A 34-year-old woman seronegative for the human immunodeficiency virus presented with recurrent, bilateral pneumothoraces. She also had bibasilar interstitial and alveolar infiltrates, and histologic examination was consistent with lymphocytic interstitial pneumonitis. To our knowledge, this is the first documented case of lymphocytic interstitial pneumonitis presenting with recurrent pneumothoraces.

The effects of ethanol, tumor necrosis factor, and granulocyte colony-stimulating factor on lung antibacterial defenses

In summary, evidence is emerging indicating that alcohol-abusing hosts are seriously undermined by profound disturbances in cytokine production and activity. These alterations likely play a critical role in the development and clinical sequelae of their immunosuppressed status. Recombinant technology currently provides the clinician with the potential to immunologically reconstitute and restore host defenses in these hosts. While the ultimate role of these agents in patients will require extensive clinical investigations into their multiple biologic effects and interactions, cytokines, when properly employed, will likely have a major impact on the prevention and treatment of many life-threatening diseases. For the first time, we possess the potential to regulate essential functions of the host defense system which may prevent the development and mitigate the severity of infections in these and other immunocompromised hosts.

Chronic oral administration of dexamethasone to rats increases cytotoxicity, but not interleukin-1 elaboration, by alveolar macrophages

Chronic administration of corticosteroids has been used to induce pulmonary infection in animals. but the specific mechanisms by which corticosteroids modulate pulmonary host defence have not been clarified. Specifically, little is known about how corticosteroids influence the function of lung cells, such as alveolar macrophages. Cytotoxicity and interleukin-1 elaboration are two important mechanisms of macrophage defence against pathogens. To determine whether chronic administration of dexamethasone alters cytotoxicity and interleukin-1 elaboration by alveolar macrophages, we studied alveolar macrophages from rats treated with oral doses of dexamethasone for 2 weeks. We found that unstimulated alveolar macrophages from dexamethasone-treated rats exhibited increased cytotoxicity compared with alveolar macrophages from control rats. Moreover, alveolar macrophages from both groups of rats showed enhanced cytotoxicity after in vitro interferon-gamma and lipopolysaccharide treatment, in a dose-dependent manner. Although no spontaneous interleukin-1 elaboration was detected from alveolar macrophages from either group of rats, lipopolysaccharide increased interleukin-1 elaboration by alveolar macrophages from both groups of rats equivalently. These results indicate that chronic oral administration of dexamethasone to rats increases cytotoxicity, and does not alter the capacity of alveolar macrophages to elaborate interleukin-1. Therefore, chronic corticosteroid administration appears to produce selective alterations in these defence mechanisms of alveolar macrophages.

A new model of Pneumocystis carinii infection in mice selectively depleted of helper T lymphocytes

Pulmonary infections with Pneumocystis carinii are an important cause of morbidity and mortality in patients with AIDS. P. carinii infections are seen in patients with decreased numbers of helper T lymphocytes, suggesting that these cells are important in preventing infection. To test this hypothesis, we sought to establish experimental infection with P. carinii in mice selectively depleted of helper T lymphocytes. Weekly injections of a monoclonal anti-CD4 antibody produced sustained depletion of helper T lymphocytes from blood and lymphoid organs. To establish pulmonary infection, lymphocyte-depleted mice were then given intratracheal inoculations of P. carinii organisms derived from the lungs of chronically infected athymic mice. Pulmonary infection with P. carinii was demonstrable in the antibody-treated mice and was centered around the conducting airways. Infection was persistent for up to 3 mo with continued antibody treatments, and yet could be cleared from the lungs if antibody treatments were discontinued. This experimental model of P. carinii infection permits the study of infection associated with a specific immune defect and implicates the helper T lymphocyte as a critical cell in host defense against this pathogen.

Altered release of eicosanoids by rat alveolar macrophages during granulomatous pulmonary inflammation

Release of arachidonic acid metabolites (eicosanoids) by alveolar macrophages may be important in regulating pulmonary inflammatory reactions. The purpose of this study was to characterize eicosanoids released by rat alveolar macrophages during the evolution of experimentally induced pulmonary inflammation. Immunization with subcutaneous bacillus Calmette-Guerin (BCG) followed 2 wk later by intravenous BCG challenge resulted in mild granulomatous pulmonary inflammation for up to 30 days. At serial intervals, alveolar macrophages were lavaged from the BCG-treated rats as well as from control normal rats. Lavaged macrophages were cultured in vitro, and culture supernatants were assayed by radioimmunoassay for release of prostaglandin E2 (PGE2), Leukotriene B4 (LTB4), and thromboxane B2 (TXB2). Cells were cultured alone, or with added LPS or calcium ionophore A23187 to stimulate eicosanoid release. During BCG-induced inflammation, spontaneous release of PGE2 and LTB4 was unchanged, while spontaneous release of TXB2 was depressed acutely and then returned to control levels. The capacity of alveolar macrophages to release specific eicosanoids in response to an in vitro stimulus was dramatically altered during the course of BCG-induced inflammation. Stimulated release of PGE2 was transiently increased during acute lung injury, but stimulated release of LTB4 was significantly decreased at all stages of inflammation. Stimulated release of TXB2 was unchanged. These results indicate that during the course of granulomatous pulmonary inflammation there are dynamic changes in the profile of eicosanoids released by alveolar macrophages, both spontaneously and in response to in vitro stimulation. This alteration in the release of eicosanoids by alveolar macrophages may be an important factor in the resolution of pulmonary inflammation.

Effects of human immunodeficiency virus on pulmonary host defenses

The ability of a microorganism to establish pulmonary infection depends not only upon its pathogenicity, but also on its ability to overcome host defense mechanisms. The frequency of pulmonary infections in patients with the acquired immunodeficiency syndrome (AIDS) suggests that pulmonary host defenses are compromised. The defense capabilities of the upper and lower airways, which prevent the majority of infectious organisms from reaching the lungs in healthy individuals, are not well characterized in AIDS. In the lower respiratory tract, direct infection of pulmonary alveolar macrophages by the human immunodeficiency virus may alter clearance of microorganisms. It is also likely that soluble signals required to activate alveolar macrophages are deficient in AIDS. Peripheral T and B lymphocytes from AIDS patients do not respond to antigen normally, and the resultant defects in cellular and humoral immunity may impair defenses against a variety of pulmonary pathogens. The defective microbicidal function of polymorphonuclear leukocytes from AIDS patients, and reduced migration of blood leukocytes into the lungs, may result in an insufficient cellular response to an infectious challenge. As the multiple defects in pulmonary host defenses associated with AIDS become characterized more fully, effective interventions for prevention and treatment of AIDS-related pulmonary infections can be developed.

Acquisition of peroxidase activity by rat alveolar macrophages during pulmonary inflammation

The authors investigated the ability of rat alveolar macrophages to acquire peroxidase activity in the course of pulmonary inflammation. Granulomatous pulmonary inflammation was induced in bacille Calmette-Guérin (BCG)-immunized rats by intravenous injection of BCG in mineral oil. In contrast to normal alveolar macrophages, which are peroxidase-negative, alveolar macrophages lavaged from the BCG-treated rats showed significant peroxidase activity in large cytoplasmic inclusions compatible with internalized exogenous material. Alveolar macrophage uptake of intact peroxidase-positive neutrophils was also observed. Maximal numbers of peroxidase-positive alveolar macrophages were observed after the initial influx of neutrophils into the lungs, and peroxidase activity could be demonstrated in cell-free lavage fluid during the acute phase of lung injury. Normal alveolar macrophages acquired peroxidase activity after incubation with peritoneal exudate neutrophils, with purified soluble human myeloperoxidase, and with opsonized erythrocytes. It is concluded that alveolar macrophages acquire peroxidase activity from multiple sources during pulmonary inflammation. Internalization of peroxidase by the alveolar macrophage may serve to clear a potentially toxic enzyme(s) from the alveolar space and contribute to the resolution of pulmonary inflammation.

Endogenous peroxidase activity as a marker of macrophage renewal during BCG-induced inflammation in the rat lung

To determine whether the cytochemical localization of peroxidase activity could be used as a marker of monocyte influx into the lung during an inflammatory response, the authors studied the peroxidase phenotypes of lavaged alveolar macrophages from rats with bacille Calmette-Guérin (BCG)-induced pulmonary inflammation. Rats were immunized subcutaneously and 2 weeks later intravenously with BCG. During the early phase of pulmonary inflammation, an increase was observed in the numbers of alveolar macrophages with no peroxidase activity in the endoplasmic reticulum. These cells appeared to reflect monocyte influx into the injured lung. The later stages of inflammation were characterized by increased numbers of alveolar macrophages with peroxidase-positive endoplasmic reticulum, probably due to activation of enzymatic activity in situ. During the early phase, peroxidase activity was also observed within macrophage cytoplasmic inclusions, probably representing both primary monocyte lysosomes and internalized myeloperoxidase from inflammatory neutrophils. Serial observations indicated that the peroxidase-positive cytoplasmic inclusions became negative with time. It is concluded that inflammation-induced modulation of peroxidase activity in the endoplasmic reticulum and in cytoplasmic inclusions makes the alveolar macrophage peroxidase phenotype no more than a rough marker of monocyte influx into the inflamed lung.

Heterogeneity of immunologic function among subfractions of normal rat alveolar macrophages. II. Activation as a determinant of functional activity

Previous studies have demonstrated differences in immunologic function among density-fractionated alveolar macrophages. The present study was undertaken to correlate these functional differences among alveolar macrophage density fractions with parameters of macrophage activation. Alveolar macrophages were lavaged from normal rats and separated into 5 density fractions by density gradient centrifugation. Cells from each density fraction were analyzed for parameters of macrophage activation: in vitro cytotoxic function directed against cultured neoplastic cells, ectoenzyme activities, and surface expression of Ia-like determinants. Lavaged alveolar macrophages with in vitro cytotoxic function were concentrated among cells from higher density fractions, and cytotoxic function among the density fractions correlated inversely with ectoenzyme activities. Although the percentage of Ia-positive cells varied among the density fractions, surface expression of Ia-like determinants did not correlate positively with in vitro cytotoxic function. The results show that there is a variable distribution of cytotoxic function among alveolar macrophage density fractions that correlates with enzymatic markers of activation. Thus, we conclude that differential macrophage activation is a potential determinant of the functional heterogeneity observed in rat alveolar macrophages.

Heterogeneity of immunologic function among subfractions of normal rat alveolar macrophages

Rat alveolar macrophages were examined for the presence of subpopulations with different capacities for modulation of mitogen-induced lymphocyte proliferation and production of the monokine, Interleukin-1 (IL-1). Alveolar macrophages lavaged from normal rats were separated into 5 density fractions by centrifugation through a continuous gradient of isosmotic colloidal silica (Percoll). Measurement of cell size and endogenous peroxidase suggested that the cells fractionated by density represented alveolar macrophages at different levels of cell maturation. Alveolar macrophages from each of the density fractions were cultured with whole lymph node cells and the mitogens, concanavalin-A and phytohemagglutinin. Functional heterogeneity was demonstrated among the fractionated cells with respect to suppression of lymphocyte mitogenesis. Alveolar macrophages from intermediate density fractions suppressed mitogenesis in a dose-dependent manner, whereas alveolar macrophages from both the lowest and the highest density fractions had minimal effect on lymphocyte proliferation. When adherence-depleted lymph node cells were used in the mitogenesis assay, rat alveolar macrophages functioned poorly in support of lymphocyte proliferation, and no uniquely supportive alveolar macrophage subfractions were identified. Functional heterogeneity was also demonstrated for production of IL-1. Maximal IL-1 production was associated with the most dense alveolar macrophages, with progressively less IL-1 produced by lower density alveolar macrophage subfractions. The results confirm functional subpopulations of rat alveolar macrophages with respect to the suppression of lymphocyte mitogenesis and the production of Interleukin-1. Such functional subpopulations of alveolar macrophages may reflect the presence of cells at varying levels of cell maturation.

Immune functions of murine alveolar macrophages: binding of lymphocytes and support of lymphocyte proliferation

Interactions between alveolar macrophages and lymphocytes may be important in the generation of pulmonary immune responses or in the induction of immunologic lung disease. We compared the relative abilities of normal murine alveolar macrophages and peritoneal macrophages to bind primed lymphocytes and to support antigen-induced lymphocyte proliferation. Alveolar macrophages were obtained by lung lavage and peritoneal macrophages by peritoneal lavage of normal mice. Lymph-node cells were harvested from draining lymph nodes of mice immunized with the peptide antigen (T,G)-A-L. Lymph-node cells were depleted of macrophages by passage through columns of Sephadex G-10 and nylon wool. To study the binding of lymphocytes to macrophages, lymph-node cells were layered over antigen-pulsed alveolar and peritoneal macrophage monolayers and the number of lymphocytes bound to the macrophages counted microscopically after incubation for 1-20 hr. Macrophage support of antigen-induced lymphocyte proliferation was studied by 3H-thymidine uptake of macrophage-depleted primed lymph-node cells cultured in the presence of soluble antigen. Cultures were repleted with graded percentages of alveolar or peritoneal macrophages. The results showed that alveolar macrophages bound significantly fewer lymphocytes than peritoneal macrophages both in a nonspecific and an antigen-specific manner. The difference in lymphocyte-binding affinity between the two macrophage types could not be attributed to factors present in lung lavage fluid. Results of the lymphocyte proliferation studies showed that while alveolar macrophages were able to support lymphocyte proliferation in response to antigen, they did so less effectively than an equal number of peritoneal macrophages. We conclude that alveolar macrophages differ significantly from peritoneal macrophages in their ability to interact with lymphocytes, both with respect to lymphocyte binding and in support of lymphocyte proliferative responses.

Flow cytometry analysis of lung cells from normal and acid-treated rabbits

Lavaged lung cells from normal rabbits and rabbits given hydrochloric acid intratracheally were analyzed using flow cytometry techniques. The rabbit alveolar macrophage was characterized as a cell with relatively high light scatter and high intrinsic autofluorescence compared with the lung neutrophil with its lower light scatter and autofluorescence. The flow cytometry characteristics of these 2 cell populations were confirmed with light microscopy after cell sorting. A flow cytometry analysis of alveolar macrophage phagocytosis using fluorescent latex particles was applied to normal rabbit alveolar macrophages. These studies showed that flow cytometry can be used to study the morphologic features and function of rabbit lavage lung cell populations and may be ultimately useful in the analysis of human lung cells.

The effect of experimental acid aspiration on alveolar macrophage function in rabbits

The effect of aspirated hydrochloric acid (HCl) on alveolar macrophage function was investigated in a rabbit model. Lung cells were obtained by bronchoalveolar lavage 4 h after an intratracheal injection of HCl. The intratracheal administration of HCl significantly increased (p < 0.005) the number of neutrophils recovered at lavage. Alveolar marcophage adherence to glass was significantly decreased (p < 0.001) in the HCl-treated animals compared with that of the control animals. Alveolar macrophage phagocytosis was not altered, and there was no effect on macrophage migration through micropore filters. In vitro studies showed that incubation of alveolar macrophages from normal rabbits in cell-free supernatants from HCl-treated rabbit lavage significantly decreased (p < 0.01) alveolar macrophage adherence to glass. In vitro incubation of alveolar macrophages from normal rabbits with rabbit peritoneal neutrophils significantly decreased (p < 0.05) adherence to glass. To investigate the effects of corticosteroid treatment, acid-injured rabbits were given 0.5 mg/kg of dexamethasone intravenously within 5 min. Alveolar macrophages from the steroid-treated animals showed a partial, but significant (p < 0.005), reversal of the acid-induced adherence defect. We concluded that acid aspiration is associated with an influx of neutrophils into the alveolar space, and decreased alveolar macrophage adherence to glass. The adherence defect was related to a factor or factors present in lavage fluid and to the presence of activated neutrophils. Corticosteriod treatment partially reversed the adherence defect.