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.

Cross sectional analysis of the effect of alcohol on pulmonary function in a cohort of men and women living with HIV.

People living with HIV (PLWH) are at increased risk for noncommunicable diseases such as lung disease in part due to opportunistic infections including pneumonia. HIV infection is associated with increased prevalence of impaired lung function and abnormal gas exchange. Alcohol use disorder (AUD) is exceedingly common in PLWH and is associated with higher risk of pneumonia in PLWH. Alcohol use may lead to lung damage through several mechanisms. Data on the long-term effect of AUD on pulmonary function in PLWH are sparse and conflicting. To evaluate this relationship, we conducted a cross-sectional analysis of adult PLWH in care in Louisiana. We hypothesized that chronic alcohol use would be associated with subsequent pulmonary dysfunction in a dose-dependent fashion. All participants performed standardized spirometry on study entry. In total, 350 participants with acceptable spirometry were included in this analysis. Thirty-one percent of participants were female. Women reported less lifetime alcohol use and less smoking; however, they reported more chronic respiratory symptoms. In adjusted models, total lifetime alcohol use was not associated with spirometry measures of pulmonary function. HIV-related variables (CD4 count and viral load) were also not associated with measures of pulmonary function. We then conducted sex-stratified analyses to eliminate residual confounding of sex and similarly found no association of total lifetime alcohol use and pulmonary function. We found no association of AUDIT score or early life alcohol use and pulmonary function. In latent class factor analysis, current heavy alcohol use was associated with lower measures of pulmonary function as compared to former heavy alcohol use. In summary, in this cohort of New Orleanian men and women living with HIV with robust measures of alcohol use, though total lifetime alcohol use and early life alcohol use were not associated with pulmonary function, current heavy alcohol use was associated with impaired pulmonary function.

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 WesTm 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.

Host innate and adaptive immunity shapes the gut microbiota biogeography.

The gut microbiota has a fundamental role in the development and the maturation of the host immune system. Both innate and adaptive immune cells have critical functions in microbial pathogen containment and clearance, but the regulation of the commensal microbiome ecosystem in the gastrointestinal tract by these major immune cell populations is incompletely defined. The role of specific innate and adaptive immune cell in the regulation of the microbiota in the intestinal tract biogeographically was investigated. Dendritic cells, macrophages, CD4+ T-cells, CD8+ T-cells, and B-cells were depleted using monoclonal antibodies and clodronate liposomes, and the microbial communities were determined by 16S rRNA gene sequencing. With specific immune cell depletion, distinct microbiota changes were observed. In general, immune cell depleted mice had higher microbiota richness and evenness at all gut anatomical sites. At each gut segment, samples from immune cell-depleted animals clustered away from the isotype/liposome control mice. This was especially dramatic for the small intestinal microbiota. Specifically, Enterobacteriaceae, Bacteroides acidifaciens, and Mucispirillum schaedleri were highly enriched in the mucosa and lumen of the small intestine in immune cell-deficient animals. Further, the mucosal microbiota had higher microbiota evenness compared with luminal microbiota at all gut segments, and the UniFrac distance between B cell depleted and isotype control mice was the largest in the duodenum followed by the ileum and colon. Taken together, the data suggest that innate and adaptive immune cells specifically contribute to the regulation of the gut microbiota's biogeographical distribution along the gastrointestinal tract, and microbiota in the duodenum mucosa are more responsive to host immune changes compared with other anatomical sites.

Pulmonary immune cell trafficking promotes host defense against alcohol-associated Klebsiella pneumonia.

The intestinal microbiota generates many different metabolites which are critical for the regulation of host signaling pathways. In fact, a wide-range of diseases are associated with increased levels of local or systemic microbe-derived metabolites. In contrast, certain bacterial metabolites, such as tryptophan metabolites, are known to contribute to both local and systemic homeostasis. Chronic alcohol consumption is accompanied by alterations to intestinal microbial communities, and their functional capacities. However, little is known about the role of alcohol-associated dysbiosis on host defense against bacterial pneumonia. Our previous work using fecal transplantation demonstrated that alcohol-associated intestinal dysbiosis, independent of ethanol consumption, increased susceptibility to Klebsiella pneumonia. Here, we demonstrate that intestinal microbiota treatments mitigate the increased risk of alcohol-associated pneumonia. Treatment with the microbial metabolite indole or with probiotics reduced pulmonary and extrapulmonary bacterial burden, restored immune responses, and improved cellular trafficking required for host defense. Protective effects were, in part, mediated by aryl hydrocarbon receptors (AhR), as inhibition of AhR diminished the protective effects. Thus, alcohol appears to impair the production/processing of tryptophan catabolites resulting in immune dysregulation and impaired cellular trafficking. These data support microbiota therapeutics as novel strategies to mitigate the increased risk for alcohol-associated bacterial pneumonia.

Alcohol-associated intestinal dysbiosis alters mucosal-associated invariant T-cell phenotype and function.

BACKGROUND: Chronic alcohol consumption is associated with a compromised innate and adaptive immune responses to infectious disease. Mucosa-associated invariant T (MAIT) cells play a critical role in antibacterial host defense. However, whether alcohol-associated deficits in innate and adaptive immune responses are mediated by alterations in MAIT cells remains unclear. METHODS: To investigate the impact of alcohol on MAIT cells, mice were treated with binge-on-chronic alcohol for 10 days and sacrificed at day 11. MAIT cells in the barrier organs (lung, liver, and intestine) were characterized by flow cytometry. Two additional sets of animals were used to examine the involvement of gut microbiota on alcohol-induced MAIT cell changes: (1) Cecal microbiota from alcohol-fed (AF) mice were adoptive transferred into antibiotic-pretreated mice and (2) AF mice were treated with antibiotics during the experiment. MAIT cells in the barrier organs were measured via flow cytometry. RESULTS: Binge-on-chronic alcohol feeding led to a significant reduction in the abundance of MAIT cells in the barrier tissues. However, CD69 expression on tissue-associated MAIT cells was increased in AF mice compared with pair-fed (PF) mice. The expression of Th1 cytokines and the corresponding transcriptional factor was tissue specific, showing downregulation in the intestine and increases in the lung and liver in AF animals. Transplantation of fecal microbiota from AF mice resulted in a MAIT cell profile aligned to that of AF mouse donor. Antibiotic treatment abolished the MAIT cell differences between AF and PF animals. CONCLUSION: MAIT cells in the intestine, liver, and lung are perturbed by alcohol use and these changes are partially attributable to alcohol-associated dysbiosis. MAIT cell dysfunction may contribute to alcohol-induced innate and adaptive immunity and consequently end-organ pathophysiology.

Acute effect of inhaled iloprost on exercise dynamic hyperinflation in COPD patients: A randomized crossover study.

BACKGROUND AND OBJECTIVE: We tested whether the prostacyclin analog inhaled iloprost modulates dead space, dynamic hyperinflation (DH), and systemic inflammation/oxidative stress during maximal exercise in subjects with chronic obstructive pulmonary disease (COPD) who were not selected based on pulmonary hypertension (PH). METHODS: Twenty-four COPD patients with moderate-severe obstruction (age 59 ± 7 years, FEV1 53 ± 13% predicted) participated in a randomized, double-blind, placebo-controlled crossover trial. Each subject received a single nebulized dose of 5.0 µg iloprost or placebo on non-consecutive days followed by maximal cardiopulmonary exercise tests. The primary outcome was DH quantified by end-expiratory lung volume/total lung capacity ratio (EELV/TLC) at metabolic isotime. RESULTS: Inhaled iloprost was well-tolerated and reduced submaximal alveolar dead-space fraction but did not significantly reduce DH (0.70 ± 0.09 vs 0.69 ± 0.07 following placebo and iloprost, respectively, p = 0.38). Maximal exercise time (9.1 ± 2.3 vs 9.3 ± 2.2 min, p = 0.31) and peak oxygen uptake (17.4 ± 6.3 vs 17.9 ± 6.9 mL/kg/min, p = 0.30) were not significantly different following placebo versus iloprost. CONCLUSIONS: A single dose of inhaled iloprost was safe and reduced alveolar dead space fraction; however, it was not efficacious in modulating DH or improving exercise capacity in COPD patients who were not selected for the presence of PH.

Intestinal Microbial Products From Alcohol-Fed Mice Contribute to Intestinal Permeability and Peripheral Immune Activation.

BACKGROUND: Alcohol use causes significant disruption of intestinal microbial communities, yet exactly how these dysbiotic communities interact with the host is unclear. We sought to understand the role of microbial products associated with alcohol dysbiosis in mice on intestinal permeability and immune activation in an in vitro model system. METHODS: Microbiota samples from binge-on-chronic alcohol-fed and pair-fed male and female mice were cultured in Gifu Anaerobic Broth for 24 hours under anaerobic conditions. Live/whole organisms were removed, and microbial products were collected and added to human peripheral blood mononuclear cells (PBMCs) or polarized C2BBe1 intestinal epithelial monolayers. Following stimulation, transepithelial electrical resistance (TEER) was measured using a volt/ohm meter and immune activation of PBMC was assessed via flow cytometry. RESULTS: Microbial products from male and female alcohol-fed mice significantly decreased TEER (mean percentage change from baseline alcohol-fed 0.86 Ω/cm2 vs. pair-fed 1.10 Ω/cm2 ) compared to microbial products from control mice. Following ex vivo stimulation, immune activation of PBMC was assessed via flow cytometry. We found that microbial products from alcohol-fed mice significantly increased the percentage of CD38+ CD4+ (mean alcohol-fed 17.32% ± 0.683% standard deviation (SD) vs. mean pair-fed 14.2% ± 1.21% SD, p < 0.05) and CD8+ (mean alcohol-fed 20.28% ± 0.88% SD vs. mean pair-fed 12.58% ± 3.59% SD, p < 0.05) T cells. CONCLUSIONS: Collectively, these data suggest that microbial products contribute to immune activation and intestinal permeability associated with alcohol dysbiosis. Further, utilization of these ex vivo microbial product assays will allow us to rapidly assess the impact of microbial products on intestinal permeability and immune activation and to identify probiotic therapies to ameliorate these defects.

Alcohol consumption increases susceptibility to pneumococcal pneumonia in a humanized murine HIV model mediated by intestinal dysbiosis.

Alcohol use in persons living with HIV (PLWH) worsens the severity of bacterial pneumonia. However, the exact mechanism(s) by which this occurs remain ill-defined. We hypothesized that alcohol in the setting of HIV infection decreases Streptococcus pneumoniae clearance from the lung through mechanisms mediated by the gut microbiota. Humanized BLT (bone marrow, liver, thymus) mice were infected with 1 × 104 TCID50 of HIV (BAL and JRCSF strains) via intraperitoneal (i.p.) injection. One week post-HIV infection, animals were switched to a Lieber-DeCarli 5% ethanol diet or an isocaloric control diet for 10 days. Alcohol-fed animals were also given two binges of 2 g/kg ethanol on days 5 and 10. Feces were also collected, banked, and the community structures were analyzed. Mice were then infected with 1 × 105 CFU (colony-forming units) of S. pneumoniae and were sacrificed 48 h later. HIV-infected mice had viral loads of ∼2 × 104 copies/mL of blood 1 week post-infection, and exhibited an ∼57% decrease in the number of circulating CD4+ T cells at the time of sacrifice. Fecal microbial community structure was significantly different in each of the feeding groups, as well as with HIV infection. Alcohol-fed mice had a significantly higher burden of S. pneumoniae 48 h post-infection, regardless of HIV status. In follow-up experiments, female C57BL/6 mice were treated with a cocktail of antibiotics daily for 2 weeks and recolonized by gavage with intestinal microbiota from HIV+ ethanol-fed, HIV+ pair-fed, HIV- ethanol-fed, or HIV- pair-fed mice. Recolonized mice were then infected with S. pneumoniae and were sacrificed 48 h later. The intestinal microbiota from alcohol-fed mice (regardless of HIV status) significantly impaired clearance of S. pneumoniae. Collectively, these data indicate that alcohol feeding, as well as alcohol-associated intestinal dysbiosis, compromise pulmonary host defenses against pneumococcal pneumonia. Determining whether HIV infection acts synergistically with alcohol use in impairing pulmonary host defenses will require additional study.

The respiratory tract microbial biogeography in alcohol use disorder.

Individuals with alcohol use disorders (AUDs) are at an increased risk of pneumonia and acute respiratory distress syndrome. Data of the lung microbiome in the setting of AUDs are lacking. The objective of this study was to determine the microbial biogeography of the upper and lower respiratory tract in individuals with AUDs compared with non-AUD subjects. Gargle, protected bronchial brush, and bronchoalveolar lavage specimens were collected during research bronchoscopies. Bacterial 16S gene sequencing and phylogenetic analysis was performed, and the alterations to the respiratory tract microbiota and changes in microbial biogeography were determined. The microbial structure of the upper and lower respiratory tract was significantly altered in subjects with AUDs compared with controls. Subjects with AUD have greater microbial diversity [ P < 0.0001, effect size = 16 ± 1.7 observed taxa] and changes in microbial species relative abundances. Furthermore, microbial communities in the upper and lower respiratory tract displayed greater similarity in subjects with AUDs. Alcohol use is associated with an altered composition of the respiratory tract microbiota. Subjects with AUDs demonstrate convergence of the microbial phylogeny and taxonomic communities between distinct biogeographical sites within the respiratory tract. These results support a mechanistic pathway potentially explaining the increased incidence of pneumonia and lung diseases in patients with AUDs.

Alcohol-associated intestinal dysbiosis impairs pulmonary host defense against Klebsiella pneumoniae.

Chronic alcohol consumption perturbs the normal intestinal microbial communities (dysbiosis). To investigate the relationship between alcohol-mediated dysbiosis and pulmonary host defense we developed a fecal adoptive transfer model, which allows us to investigate the impact of alcohol-induced gut dysbiosis on host immune response to an infectious challenge at a distal organ, independent of prevailing alcohol use. Male C57BL/6 mice were treated with a cocktail of antibiotics (ampicillin, gentamicin, neomycin, vancomycin, and metronidazole) via daily gavage for two weeks. A separate group of animals was fed a chronic alcohol (or isocaloric dextrose pair-fed controls) liquid diet for 10 days. Microbiota-depleted mice were recolonized with intestinal microbiota from alcohol-fed or pair-fed (control) animals. Following recolonization groups of mice were sacrificed prior to and 48 hrs. post respiratory infection with Klebsiella pneumoniae. Klebsiella lung burden, lung immunology and inflammation, as well as intestinal immunology, inflammation, and barrier damage were examined. Results showed that alcohol-associated susceptibility to K. pneumoniae is, in part, mediated by gut dysbiosis, as alcohol-naïve animals recolonized with a microbiota isolated from alcohol-fed mice had an increased respiratory burden of K. pneumoniae compared to mice recolonized with a control microbiota. The increased susceptibility in alcohol-dysbiosis recolonized animals was associated with an increase in pulmonary inflammatory cytokines, and a decrease in the number of CD4+ and CD8+ T-cells in the lung following Klebsiella infection but an increase in T-cell counts in the intestinal tract following Klebsiella infection, suggesting intestinal T-cell sequestration as a factor in impaired lung host defense. Mice recolonized with an alcohol-dysbiotic microbiota also had increased intestinal damage as measured by increased levels of serum intestinal fatty acid binding protein. Collectively, these results suggest that alterations in the intestinal immune response as a consequence of alcohol-induced dysbiosis contribute to increased host susceptibility to Klebsiella pneumonia.

B cell and antibody responses in mice induced by a putative cell surface peptidase of Pneumocystis murina protect against experimental infection.

RATIONALE: Pneumocystis pneumonia is a major cause of morbidity and mortality in HIV-infected subjects, cancer patients undergoing chemotherapy and solid organ transplant recipients. No vaccine is currently available. By chemical labeling coupled with proteomic approach, we have identified a putative surface protein (SPD1, Broad Institute gene accession number PNEG_01848) derived from single suspended P. murina cysts. SPD1 was expressed in an insect cell line and tested for vaccine development. METHODS: Mice were immunized with SPD1 plus adjuvant MF-59 by subcutaneous injection. Three weeks after the last immunization, CD4+ cells were depleted with anti-CD4 antibody GK1.5. The mice were then challenged with 2×105Pneumocystis organisms. Mice were sacrificed at 4 and 6weeks after PC challenge. Spleen/lung cells and serum were harvested. B cells and memory B cells were assessed via flow cytometry. Specific Pneumocystis IgG antibody was measured by ELISA before and after challenge. Infection burden was measured as real-time PCR for P. murina rRNA. RESULTS: Normal mice infected with Pneumocystis mounted a serum IgG antibody response to SPD1. Serum from rhesus macaques exposed to Pneumocystis showed a similar serum IgG response to purified SPD1. SPD1 immunization increased B cell and memory B cell absolute cell counts in CD4-depleted Balb/c mice post Pneumocystis challenge in spleen and lung. Immunization with SPD1 significantly increased specific Pneumocystis IgG antibody production before and after challenge. Mice immunized with SPD1 showed significantly decreased P. murina copy number compared with mice that did not receive SPD1 at 6weeks after challenge. CONCLUSION: Immunization with SPD1 provides protective efficacy against P. murina infection. SPD1 protection against Pneumocystis challenge is associated with enhanced memory B cell production and higher anti-Pneumocystis IgG antibody production. SPD1 is a potential vaccine candidate to prevent or treat pulmonary infection with Pneumocystis.

Analysis of the intestinal microbial community and inferred functional capacities during the host response to Pneumocystis pneumonia.

BACKGROUND: Pneumocystis pneumonia is a major cause of morbidity and mortality in patients infected with HIV/AIDS. In this study, we evaluated the intestinal microbial communities associated with the development of experimental Pneumocystis pneumonia, as there is growing evidence that the intestinal microbiota is critical for host defense against fungal pathogens. METHODS: C57BL/6 mice were infected with live Pneumocystis murina (P. murina) via intratracheal inoculation and sacrificed 7 and 14 days postinfection for microbiota analysis. In addition, we evaluated the intestinal microbiota from CD4+ T cell depleted mice infected with P. murina. RESULTS: We found that the diversity of the intestinal microbial community was significantly altered by respiratory infection with P. murina. Specifically, mice infected with P. murina had altered microbial populations, as judged by changes in diversity metrics and relative taxa abundances. We also found that CD4+ T cell depleted mice infected with P. murina exhibited significantly altered intestinal microbiota that was distinct from immunocompetent mice infected with P. murina, suggesting that loss of CD4+ T cells may also affects the intestinal microbiota in the setting of Pneumocystis pneumonia. Finally, we employed a predictive metagenomics approach to evaluate various microbial features. We found that Pneumocystis pneumonia significantly alters the intestinal microbiota's inferred functional potential for carbohydrate, energy, and xenobiotic metabolism, as well as signal transduction pathways. CONCLUSIONS: Our study provides insight into specific-microbial clades and inferred microbial functional pathways associated with Pneumocystis pneumonia. Our data also suggest a role for the gut-lung axis in host defense in the lung.

Gene-based neonatal immune priming potentiates a mucosal adenoviral vaccine encoding mycobacterial Ag85B.

Tuberculosis remains a major public health hazard worldwide, with neonates and young infants potentially more susceptible to infection than adults. BCG, the only vaccine currently available, provides some protection against tuberculous meningitis in children but variable efficacy in adults, and is not safe to use in immune compromised individuals. A safe and effective vaccine that could be given early in life, and that could also potentiate subsequent booster immunization, would represent a significant advance. To test this proposition, we have generated gene-based vaccine vectors expressing Ag85B from Mycobacterium tuberculosis (Mtb) and designed experiments to test their immunogenicity and protective efficacy particularly when given in heterologous prime-boost combination, with the initial DNA vaccine component given soon after birth. Intradermal delivery of DNA vaccines elicited Th1-based immune responses against Ag85B in neonatal mice but did not protect them from subsequent aerosol challenge with virulent Mtb H37Rv. Recombinant adenovirus vectors encoding Ag85B, given via the intranasal route at six weeks of age, generated moderate immune responses and were poorly protective. However, neonatal DNA priming following by mucosal boosting with recombinant adenovirus generated strong immune responses, as evidenced by strong Ag85B-specific CD4+ and CD8+ T cell responses, both in the lung-associated lymph nodes and the spleen, by the quality of these responding cells (assessed by their capacity to secrete multiple antimicrobial factors), and by improved protection, as indicated by reduced bacterial burden in the lungs following pulmonary TB challenge. These results suggest that neonatal immunization with gene-based vaccines may create a favorable immunological environment that potentiates the pulmonary mucosal boosting effects of a subsequent heterologous vector vaccine encoding the same antigen. Our data indicate that immunization early in life with mycobacterial antigens in an appropriate vaccine setting can prime for protective immunity against Mtb.

CD4(+) T-Cell-Independent Secondary Immune Responses to Pneumocystis Pneumonia.

Pneumocystis pneumonia is a major cause of morbidity and mortality among immunocompromised patients, especially in the context of HIV/AIDS. In the murine model of Pneumocystis pneumonia, CD4(+) T-cells are required for clearance of a primary infection of Pneumocystis, but not the memory recall response. We hypothesized that the memory recall response in the absence of CD4(+) T-cells is mediated by a robust memory humoral response, CD8(+) T-cells, and IgG-mediated phagocytosis by alveolar macrophages. To investigate the role of CD8(+) T-cells and alveolar macrophages in the immune memory response to Pneumocystis, mice previously challenged with Pneumocystis were depleted of CD8(+) T-cells or alveolar macrophages prior to re-infection. Mice depleted of CD4(+) T-cells prior to secondary challenge cleared Pneumocystis infection within 48 h identical to immunocompetent mice during a secondary memory recall response. However, loss of CD8(+) T-cells or macrophages prior to the memory recall response significantly impaired Pneumocystis clearance. Specifically, mice depleted of CD8(+) T-cells or alveolar macrophages had significantly higher fungal burden in the lungs. Furthermore, loss of alveolar macrophages significantly skewed the lung CD8(+) T-cell response toward a terminally differentiated effector memory population and increased the percentage of IFN-γ(+) CD8(+) T-cells. Finally, Pneumocystis-infected animals produced significantly more bone marrow plasma cells and Pneumocystis-specific IgG significantly increased macrophage-mediated killing of Pneumocystis in vitro. These data suggest that secondary immune memory responses to Pneumocystis are mediated, in part, by CD8(+) T-cells, alveolar macrophages, and the production of Pneumocystis-specific IgG.

Human Immunodeficiency Virus Infection and Host Defense in the Lungs.

Immunosuppression associated with human immunodeficiency virus (HIV) infection impacts all components of host defense against pulmonary infection. Cells within the lung have altered immune function and are important reservoirs for HIV infection. The host immune response to infected lung cells further compromises responses to a secondary pathogenic insult. In the upper respiratory tract, mucociliary function is impaired and there are decreased levels of salivary immunoglobulin A. Host defenses in the lower respiratory tract are controlled by alveolar macrophages, lymphocytes, and polymorphonuclear leukocytes. As HIV infection progresses, lung CD4 T cells are reduced in number causing a lack of activation signals from CD4 T cells and impaired defense by macrophages. CD8 T cells, on the other hand, are increased in number and cause lymphocytic alveolitis. Specific antibody responses by B-lymphocytes are decreased and opsonization of microorganisms is impaired. These observed defects in host defense of the respiratory tract explain the susceptibility of HIV-infected persons for oropharyngeal candidiasis, bacterial pneumonia, Pneumocystis pneumonia, and other opportunistic infections.

Oral Immunization of Mice with Live Pneumocystis murina Protects against Pneumocystis Pneumonia.

Pneumocystis pneumonia is a major cause of morbidity and mortality in immunocompromised patients, particularly those infected with HIV. In this study, we evaluated the potential of oral immunization with live Pneumocystis to elicit protection against respiratory infection with Pneumocystis murina. C57BL/6 mice vaccinated with live P. murina using a prime-boost vaccination strategy were protected from a subsequent lung challenge with P. murina at 2, 7, 14, and 28 d postinfection even after CD4(+) T cell depletion. Specifically, vaccinated immunocompetent mice had significantly faster clearance than unvaccinated immunocompetent mice and unvaccinated CD4-depleted mice remained persistently infected with P. murina. Vaccination also increased numbers of CD4(+) T cells, CD8(+) T cells, CD19(+) B cells, and CD11b(+) macrophages in the lungs following respiratory infection. In addition, levels of lung, serum, and fecal P. murina-specific IgG and IgA were increased in vaccinated animals. Furthermore, administration of serum from vaccinated mice significantly reduced Pneumocystis lung burden in infected animals compared with control serum. We also found that the diversity of the intestinal microbial community was altered by oral immunization with P. murina. To our knowledge, our data demonstrate for the first time that an oral vaccination strategy prevents Pneumocystis infection.

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-1ß (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 Encoded in Gene-Based Vector Vaccines Is a Route-Dependent Immune Adjuvant.

Flagellin has been tested as a protein-based vaccine adjuvant, with the majority of studies focused on antibody responses. Here, we evaluated the adjuvant activity of flagellin for both cellular and humoral immune responses in BALB/c mice in the setting of gene-based immunization, and have made several novel observations. DNA vaccines and adenovirus (Ad) vectors were engineered to encode mycobacterial protein Ag85B, with or without flagellin of Salmonella typhimurium (FliC). DNA-encoded flagellin given IM enhanced splenic CD4+ and CD8+ T cell responses to co-expressed vaccine antigen, including memory responses. Boosting either IM or intranasally with Ad vectors expressing Ag85B without flagellin led to durable enhancement of Ag85B-specific antibody and CD4+ and CD8+ T cell responses in both spleen and pulmonary tissues, correlating with significantly improved protection against challenge with pathogenic aerosolized M. tuberculosis. However, inclusion of flagellin in both DNA prime and Ad booster vaccines induced localized pulmonary inflammation and transient weight loss, with route-dependent effects on vaccine-induced T cell immunity. The latter included marked reductions in levels of mucosal CD4+ and CD8+ T cell responses following IM DNA/IN Ad mucosal prime-boosting, although antibody responses were not diminished. These findings indicate that flagellin has differential and route-dependent adjuvant activity when included as a component of systemic or mucosally-delivered gene-based prime-boost immunization. Clear adjuvant activity for both T and B cell responses was observed when flagellin was included in the DNA priming vaccine, but side effects occurred when given in an Ad boosting vector, particularly via the pulmonary route.

Regulation of lung immunity and host defense by the intestinal microbiota.

Every year in the United States approximately 200,000 people die from pulmonary infections, such as influenza and pneumonia, or from lung disease that is exacerbated by pulmonary infection. In addition, respiratory diseases such as, asthma, affect 300 million people worldwide. Therefore, understanding the mechanistic basis for host defense against infection and regulation of immune processes involved in asthma are crucial for the development of novel therapeutic strategies. The identification, characterization, and manipulation of immune regulatory networks in the lung represents one of the biggest challenges in treatment of lung associated disease. Recent evidence suggests that the gastrointestinal (GI) microbiota plays a key role in immune adaptation and initiation in the GI tract as well as at other distal mucosal sites, such as the lung. This review explores the current research describing the role of the GI microbiota in the regulation of pulmonary immune responses. Specific focus is given to understanding how intestinal "dysbiosis" affects lung health.