Depletion of CD8+ T cells exacerbates CD4+ Th cell-associated inflammatory lesions during murine mycoplasma respiratory disease

Clinical characteristics and serum inflammatory markers of community-acquired mycoplasma pneumonia in children

BACKGROUND

To compare the demographic and clinical features, laboratory and imaging findings in mycoplasma pneumoniae pneumonia (MPP) children with non-MPP (NMPP) children and general MPP (GMPP) children with refractory MPP (RMPP) children and analysis the relationship with the severity of disease.

METHODS

The study included 265 children with MPP and 230 children with NMPP in the Affiliated Changzhou No. 2 People's Hospital of Nanjing Medical University from 2020 to 2021. The children with MPP included RMPP (n = 85) and GMPP (n = 180). Demographic and clinical characteristics, laboratory and imaging findings of all children were measured as baseline data within 24 h after admission and the differences between MPP and NMPP, RMPP and GMPP patients were compared. ROC curves were used to evaluate the diagnostic and predictive value of different indicators for RMPP.

RESULTS

Fever duration and hospital stay in children with MPP were longer than those with NMPP. The number of patients with imaging features of pleural effusion, lung consolidation and bronchopneumonia in MPP group was significantly higher than that in NMPP group. Compared with NMPP group, the levels of C-reactive protein (CRP), procalcitonin (PCT), serum amyloid A (SAA), erythrocyte sedimentation rate (ESR), lactic dehydrogenase (LDH), prothrombin time (PT), fibrinogen (FIB) and D-dimer and inflammatory cytokines (interleukin [IL]-6, IL-8, IL-10 and IL-1β) in MPP group were significantly higher (P < 0.05). The clinical symptoms and pulmonary imaging findings were more severe in RMPP group. The levels of white blood cell (WBC), CRP, PCT, SAA, ESR, alanine aminotransferase (ALT), LDH, ferritin, PT, FIB, D-dimer and inflammatory cytokines in RMPP group were higher than those in GMPP group. There was no significant difference in the level of lymphocyte subsets between the RMPP and GMPP group. IL-6, IL-10, LDH, PT, D-dimer and lung consolidation were independent risk factors for RMPP. IL-6 levels and LDH activity were good predictors of RMPP.

CONCLUSION

In conclusion, there were differences in clinical characteristics and serum inflammatory markers between MPP group and NMPP group, RMPP group and GMPP group. IL-6, IL-10, LDH, PT and D-dimer can be used as predictive indicators for RMPP.

Pneumocystis Pneumonia With Multiple Centrilobular Pulmonary Nodules and Lack of Ground-Glass Attenuation on High-Resolution Computed Tomography

Pneumocystis jirovecii pneumonia (PCP) typically presents with diffuse ground-glass attenuation (GGA) in both lungs on high-resolution CT (HRCT). While other radiological features, including cysts and air-space consolidation, may be found, the absence of GGA has a high negative predictive value for PCP in patients with AIDS. We report a case of PCP in a male patient who visited our hospital with a subacute, non-productive cough. He had never been diagnosed with an HIV infection. Although his HRCT scan revealed multiple centrilobular nodules without GGA, Pneumocystis jirovecii was detected in the bronchoalveolar lavage (BAL), and no other additional pathogens were identified. The patient was diagnosed with PCP associated with AIDS after a high plasma HIV-RNA titer and low CD4+ cell count were confirmed. Physicians need to be aware of this atypical radiological presentation of PCP associated with AIDS.

Different local, innate and adaptive immune responses are induced by two commercial Mycoplasma hyopneumoniae bacterins and an adjuvant alone

Introduction

Enzootic pneumonia still causes major economic losses to the intensive pig production. Vaccination against its primary pathogen, Mycoplasma hyopneumoniae, is carried out worldwide to control the disease and minimize clinical signs and performance losses. Nonetheless, the effects of both infection with, and vaccination against Mycoplasma hyopneumoniae on the innate and adaptive immune responses remain largely unknown. Therefore, we conducted a study in which piglets were injected once with a commercial bacterin V1 or V2, or the adjuvant of V1 (A) to investigate their effect on local, innate and adaptive immune responses.

Methods

Three weeks after vaccination, piglets were challenge infected with M. hyopneumoniae and euthanized four weeks later to assess vaccine efficacy via macroscopic and microscopic evaluation of lung lesions. Blood and broncho-alveolar lavage fluid (BAL) samples were collected to measure antibody responses, cellular immunity, BAL cytokine levels and BAL M. hyopneumoniae DNA load as well as cytokine secretion by monocytes.

Results

After vaccination, proliferation of antigen-specific CD3⁺ T cells and a higher percentage of TNF-α⁺ CD8⁺, and TNF-α⁺ and TNF-α⁺IFN-γ⁺ CD4⁺CD8⁺ T cells was seen in V1, while proliferation of or a significant increase in cytokine production by different T cell subsets could not be observed for animals from V2. Interestingly, LPS-stimulated blood monocytes from V1 and A secreted less IL-10 on D7. After challenge, higher levels of IgA, more IL-10 and less IL-1β was detected in BAL from V1, which was not observed in V2. Animals from A had significantly more IL-17A in BAL. The macroscopic lung lesion score and the M. hyopneumoniae DNA load at euthanasia was lower in V1, but the microscopic lung lesion score was lower in both vaccinated groups.

Discussion

In conclusion, these results indicate that the two commercial bacterins induced different local and adaptive immune responses, that the adjuvant alone can reduce anti-inflammatory innate immune responses, and that both vaccines had a different efficacy to reduce Mycoplasma-like lung lesions and M. hyopneumoniae DNA load in the lung.

B cells oppose Mycoplasma pneumoniae vaccine enhanced disease and limit bacterial colonization of the lungs

Development of an effective vaccine for Mycoplasma pneumoniae has been hindered by reports of Vaccine Enhanced Disease (VED) in test subjects vaccinated and challenged in studies conducted in the 1960s. The exact mechanism of disease exacerbation has yet to be fully described, but host immune responses to Lipid-Associated Membrane Proteins (LAMPs) lipoprotein lipid moieties have been implicated. LAMPs-induced exacerbation appears to involve helper T cell recall responses, due in part to their influence on neutrophil recruitment and subsequent inflammatory responses in the lung. Herein, we characterized the functions of host B cell responses to M. pneumoniae LAMPs and delipidated-LAMPs (dLAMPs) by conducting passive transfer and B cell depletion studies to assess their contribution to disease exacerbation or protection using a BALB/c mouse model. We found that antibody responses to M. pneumoniae LAMPs and dLAMPs differ in magnitude, but not in isotype or subclass. Passive transfer, dLAMP denaturation, and monoclonal antibody studies indicate that antibodies do not cause VED, but do appear to contribute to control of bacterial loads in the lungs. Depletion of B cells prior to LAMPs-vaccination results in significantly enhanced pathology in comparison to B cell competent controls, suggesting a possible regulatory role of B cells distinct from antibody secretion. Taken together, our findings suggest that B cell antibody responses to M. pneumoniae contribute to, but are insufficient for protection against challenge on their own, and that other functional properties of B cells are necessary to limit exacerbation of disease in LAMPs-vaccinated mice after infection.

A Recombinant MVA-Based RSV Vaccine Induces T-Cell and Antibody Responses That Cooperate in the Protection Against RSV Infection

Respiratory syncytial virus (RSV) causes a respiratory disease with a potentially fatal outcome especially in infants and elderly individuals. Several vaccines failed in pivotal clinical trials, and to date, no vaccine against RSV has been licensed. We have developed an RSV vaccine based on the recombinant Modified Vaccinia Virus Ankara-BN^® (MVA-RSV), containing five RSV-specific antigens that induced antibody and T-cell responses, which is currently tested in clinical trials. Here, the immunological mechanisms of protection were evaluated to determine viral loads in lungs upon vaccination of mice with MVA-RSV followed by intranasal RSV challenge. Depletion of CD4 or CD8 T cells, serum transfer, and the use of genetically engineered mice lacking the ability to generate either RSV-specific antibodies (T11µMT), the IgA isotype (IgA knockout), or CD8 T cells (β2M knockout) revealed that complete protection from RSV challenge is dependent on CD4 and CD8 T cells as well as antibodies, including IgA. Thus, MVA-RSV vaccination optimally protects against RSV infection by employing multiple arms of the adaptive immune system.

Mycoplasma pneumonia Infection Is Associated With an Increased Risk of Systemic Lupus Erythematosus: A Nationwide, Retrospective Cohort Study

Background

Infections may play a role in the development of systemic lupus erythematosus (SLE).

Objective

To assess the link between Mycoplasma pneumonia (M. pneumonia) infection and the incidence of SLE.

Method

We conducted a retrospective cohort study, which identified 116,043 hospitalized patients with M. pneumoniae between 2000 and 2012 from the Taiwan National Health Insurance Research Database and compared them with 447,839 matched inpatients who had never been diagnosed with M. pneumonia infection (at a 1:4 ratio, matched by age, gender, and index year). Their comparative risk of developing SLE was evaluated. The follow-up period was defined as the time from the initial diagnosis of M. pneumonia infection to the date of SLE diagnosis, or December 31, 2013. The incidence rates of SLE were assessed in people with and without M. pneumoniae infection. Cox proportional hazard models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs), with the uninfected group used as the reference.

Results

The adjusted HR of SLE for the M. pneumoniae group was 2.97 with 95% CI = 2.18–4.05 compared with the uninfected group. The risk was most significantly higher within 0.5 years after the M. pneumoniae infection with an adjusted HR of 6.18 (95% CI = 3.82–9.97, p < 0.01). The adjusted HR for SLE from 0.5 to 2 years and from 2 to 5 years after M. pneumoniae infection was 1.59 (95% CI = 0.70–3.59, p = 0.27) and 2.42 (95% CI = 1.22–4.81, p = 0.01), respectively.

Conclusion

The incidence of SLE was significantly higher in subjects infected with M. pneumoniae.

Immune responses to bacterial lung infections and their implications for vaccination

The pulmonary immune system plays a vital role in protecting the delicate structures of gaseous exchange against invasion from bacterial pathogens. With antimicrobial resistance becoming an increasing concern, finding novel strategies to develop vaccines against bacterial lung diseases remains a top priority. In order to do so, a continued expansion of our understanding of the pulmonary immune response is warranted. Whilst some aspects are well characterised, emerging paradigms such as the importance of innate cells and inducible immune structures in mediating protection provide avenues of potential to rethink our approach to vaccine development. In this review, we aim to provide a broad overview of both the innate and adaptive immune mechanisms in place to protect the pulmonary tissue from invading bacterial organisms. We use specific examples from several infection models and human studies to depict the varying functions of the pulmonary immune system that may be manipulated in future vaccine development. Particular emphasis has been placed on emerging themes that are less reviewed and underappreciated in vaccine development studies.

Long-Residence Pneumonia Vaccine Developed Using PEG-Grafted Hybrid Nanovesicles from Cell Membrane Fusion of Mycoplasma and IFN-γ-Primed Macrophages

CD8⁺ T cell responses play a critical regulatory role in protection against mycoplasma infection-related respiratory diseases. Nanovesicles derived from cell membranes have been shown to induce CD8⁺ T cell responses. Moreover, the short residence time of mycoplasma membrane-related vaccines in local lymph nodes limits the efficacy of current mycoplasma vaccines. Here, a long-residence pneumonia vaccine is developed using nanovesicles prepared by cell membrane fusion of Mycoplasma hyopneumoniae and interferon-γ (IFN-γ   )-primed macrophages, which are grafted with polyethylene glycol to increase residence time in the lymph nodes. Upregulation of intercellular adhesion molecule-1 (ICAM-1) on the membrane of IFN-γ-primed macrophages increases the targeting of the hybrid nanovesicle vaccine to the local lymph nodes, with increased CD8⁺ T cell activation. A mechanistic study reveals that CD8⁺ T cell activation is achieved via a pathway involving upregulation of C-C motif chemokine ligand 2/3 expression by E26 transformation-specific sequences, followed by increased immune-stimulatory activity of dendritic cells. In vivo, prophylactic testing reveals that the hybrid nanovesicle vaccine triggers a long-term immune response, as evidenced by a memory CD8⁺ T cell response against mycoplasma infection. The current study provides a new design strategy for mycoplasma vaccines that involves a hybrid method using biological sources and artificial modification.

Effects of immunosuppression on the efficacy of vaccination against Mycoplasma gallisepticum infection in chickens

Immunosuppression can increase the susceptibility of chickens to other disease-causing pathogens and interfere with the efficacy of vaccination against those pathogens. Chicken anaemia virus (CAV) and infectious bursal disease virus (IBDV) are common causes of immunosuppression in chickens. Immunosuppression was induced by experimental infection with either CAV or IBDV to assess the effect of immunosuppression on the efficacy of vaccination with Mycoplasma gallisepticum strain ts-304 against infection with virulent M. gallisepticum, a common bacterial pathogen of chickens worldwide. Birds were experimentally infected with either CAV or IBDV at 1 week of age, before vaccination and challenge with M. gallisepticum to examine the effect of immunosuppression at the time of vaccination, or at 6 weeks of age, after vaccination against M. gallisepticum but before challenge with virulent M. gallisepticum, to investigate the effect of immunosuppression at the time of challenge. All birds were vaccinated with a single dose of the ts-304 vaccine at 3 weeks of age and experimentally challenged with the virulent M. gallisepticum strain Ap3AS at 8 weeks of age. In immunosuppressed chickens there was a reduction in protection offered by the ts-304 vaccine at two weeks after challenge, as measured by tracheal mucosal thicknesses, serum antibody levels against M. gallisepticum, air sac lesion scores and virulent M. gallisepticum load in the trachea. Immunosuppressed birds with detectable serum antibodies against M. gallisepticum were less likely to have tracheal lesions. This study has shown that immunosuppression caused by infection with CAV or IBDV can interfere with vaccination against mycoplasmosis in chickens.

A Previously Unrecognized Granulomatous Variant of Gamma-Delta T-Cell Lymphoma

Primary cutaneous γδ T-cell lymphoma (PCGD-TCL) is an extremely rare and aggressive T-cell neoplasm with complex heterogeneity. We present a series of two patients who presented with firm, subcutaneous nodules and were diagnosed with PCGD-TCL. In both cases, biopsies demonstrated a both superficial and deep adnexotropic infiltrate comprised of angiocentric, medium- to large-sized atypical lymphocytes. The infiltrate extended into the panniculus. Immuno–histochemical stains highlighted atypical lymphocytes that expressed CD3, CD8 and CD56 but were negative for EBV ISH. A brisk histiocytic response with focal aggregation into granulomas was highlighted with a PG-M1 stain. The atypical lymphocytes were positive for gene rearrangements on a TCR delta stain and negative for βF-1. CT and PET scan in one of the two patients demonstrated diffuse, subcutaneous, ground-glass foci; hypermetabolic soft tissue nodules; and lymphadenopathy in the lungs, as well as splenomegaly. A diagnosis of histiocyte-rich PCGD-TCL was rendered. A histiocyte-rich, granulomatous variant of γδ T-cell lymphoma is extremely rare. Its potentially misleading resemblance to inflammatory granulomatous conditions could pose a diagnostic pitfall in this already challenging condition. This variant may resemble granulomatous mycosis fungoides and granulomatous slack skin syndrome, but it has a distinct, aggressive clinical outcome.

Biological functions of IL-17-producing cells in mycoplasma respiratory infection

Mycoplasmas are the smallest and simplest bacteria that lack a cell wall but have the capability of self-replication. Among them, Mycoplasma pneumoniae is one of the most common causes of community-acquired pneumonia. The hallmark of mycoplasma respiratory diseases is the persistence of lung inflammation that involves both innate and adaptive immune responses. In recent years, a growing body of evidence demonstrates that IL-17 plays an important role in respiratory mycoplasma infection, and associates with the pathologic outcomes of infection, such as pneumonitis and asthma. Numerous studies have shown that a variety of cells, in particular Th17 cells, in the lung can secrete IL-17 during respiratory mycoplasma infection. In this article, we review the biological functions of distinct IL-17-producing cells in mycoplasma respiratory infection with a focus on the effect of IL-17 on the outcomes of infection.

Pathological and Immunohistochemical Studies of Experimental Mycoplasma pneumoniae in Gerbils (Meriones unguiculatus)

Mycoplasma pneumoniae (Mp) is a leading cause of human community-acquired pneumonia. To investigate the pathogenesis of the infection, 36 gerbils were intranasally inoculated with Mp culture (30 animals) or sterile mycoplasma broth (6 animals) and euthanized from 1 to 5 weeks post infection. A morphological and immunohistochemical study was carried out in all animals to determine the cellular populations present in lung parenchyma. Polyclonal and monoclonal antibodies were used to detect antigens of Mp and CD3, CD4, CD8 and CD79 lymphocytes, as well as cells containing S100 and major histocompatibility complex class II (MHC-II) antigens. There was progressive infiltration of mononuclear cells in the lamina propria of bronchi and bronchioles, and hyperplasia of the bronchus-associated lymphoid tissue (BALT) in the infected animals. BALT contained dendritic cells immunopositive to S100 and MHC-II and numerous CD3, CD4 and CD79 lymphocytes. The immunohistochemical results showed that T lymphocytes, particularly CD4 and CD79 cells, may play a role in the immune response of gerbils against Mp. This experimental model is valuable for investigation of the pathogenesis of Mp infection and may assist in the development of therapeutic strategies.

Contagious Bovine Pleuropneumonia: A Comprehensive Overview

Contagious bovine pleuropneumonia (CBPP) is a respiratory disease of cattle that is listed as notifiable by the World Organization for Animal Health. It is endemic in sub-Saharan Africa and causes important productivity losses due to the high mortality and morbidity rates. CBPP is caused by Mycoplasma mycoides subsp. mycoides (Mmm) and is characterized by severe fibrinous bronchopneumonia and pleural effusion during the acute to subacute stages and by pulmonary sequestra in chronic cases. Additional lesions can be detected in the kidneys and in the carpal and tarsal joints of calves. Mmm infection occurs through the inhalation of infected aerosol droplets. After the colonization of bronchioles and alveoli, Mmm invades blood and lymphatic vessels and causes vasculitis. Moreover, Mmm can be occasionally demonstrated in blood and in a variety of other tissues. In the lung, Mmm antigen is commonly detected on bronchiolar and alveolar epithelial cells, in lung phagocytic cells, within the wall of blood and lymphatic vessels, inside necrotic areas, and within tertiary lymphoid follicles. Mmm antigen can also be present in the cytoplasm of macrophages within lymph node sinuses, in the germinal center of lymphoid follicles, in glomerular endothelial cells, and in renal tubules. A complete pathological examination is of great value for a rapid presumptive diagnosis, but laboratory investigations are mandatory for definitive diagnosis. The purpose of this review is to describe the main features of CBPP including the causative agent, history, geographic distribution, epidemiology, clinical course, diagnosis, and control. A special focus is placed on gross and microscopic lesions in order to familiarize veterinarians with the pathology and pathogenesis of CBPP.

Proteases as Secreted Exoproteins in Mycoplasmas from Ruminant Lungs and Their Impact on Surface-Exposed Proteins

Many mycoplasma species are isolated from the ruminant lungs as either saprophytes or true pathogens. These wall-less bacteria possess a minimal genome and reduced metabolic capabilities. Accordingly, they rely heavily on their hosts for the supply of essential metabolites and, notably, peptides. Seven of 13 ruminant lung-associated Mycoplasma (sub)species were shown to possess caseinolytic activity when grown in rich media and assessed with a quantitative fluorescence test. For some species, this activity was detected in spent medium, an indication that proteases were secreted outside the mycoplasma cells. To identify these proteases, we incubated concentrated washed cell pellets in a defined medium and analyzed the supernatants by tandem mass spectrometry. Secreted-protease activity was detected mostly in the species belonging to the Mycoplasma mycoides cluster (MMC) and, to a lesser extent, in Mycoplasma bovirhinis Analyzing a Mycoplasma mycoides subsp. capri strain, chosen as a model, we identified 35 expressed proteases among 55 predicted coding genes, of which 5 were preferentially found in the supernatant. Serine protease S41, acquired by horizontal gene transfer, was responsible for the caseinolytic activity, as demonstrated by zymography and mutant analysis. In an M. capricolum mutant, inactivation of the S41 protease resulted in marked modification of the expression or secretion of 17 predicted surface-exposed proteins. This is an indication that the S41 protease could have a role in posttranslational cleavage of surface-exposed proteins and ectodomain shedding, whose physiological impacts still need to be explored.IMPORTANCE Few studies pertaining to proteases in ruminant mycoplasmas have been reported. Here, we focus on proteases that are secreted outside the mycoplasma cell using a mass spectrometry approach. The most striking result is the identification, within the Mycoplasma mycoides cluster, of a serine protease that is exclusively detected outside the mycoplasma cells and is responsible for casein digestion. This protease may also be involved in the posttranslational processing of surface proteins, as suggested by analysis of mutants showing a marked reduction in the secretion of extracellular proteins. By analogy, this finding may help increase understanding of the mechanisms underlying this ectodomain shedding in other mycoplasma species. The gene encoding this protease is likely to have been acquired via horizontal gene transfer from Gram-positive bacteria and sortase-associated surface proteases. Whether this protease and the associated ectodomain shedding are related to virulence has yet to be ascertained.

Efficacy of three innovative bacterin vaccines against experimental infection with Mycoplasma hyopneumoniae

New vaccine formulations that include novel strains of Mycoplasma hyopneumoniae and innovative adjuvants designed to induce cellular immunity could improve vaccine efficacy against this pathogen. The aim of this experimental study was to assess the efficacy of three experimental bacterin formulations based on M. hyopneumoniae field strain F7.2C which were able to induce cellular immunity. The formulations included a cationic liposome formulation with the Mincle receptor ligand trehalose 6,6-dibehenate (Lipo_DDA:TDB), a squalene-in-water emulsion with Toll-like receptor (TLR) ligands targeting TLR1/2, TLR7/8 and TLR9 (SWE_TLR), and a poly(lactic-co-glycolic acid) micro-particle formulation with the same TLR ligands (PLGA_TLR). Four groups of 12 M. hyopneumoniae-free piglets were primo- (day (D) 0; 39 days of age) and booster vaccinated (D14) intramuscularly with either one of the three experimental bacterin formulations or PBS. The pigs were endotracheally inoculated with a highly and low virulent M. hyopneumoniae strain on D28 and D29, respectively, and euthanized on D56. The main efficacy parameters were: respiratory disease score (RDS; daily), macroscopic lung lesion score (D56) and log copies M. hyopneumoniae DNA determined with qPCR on bronchoalveolar lavage (BAL) fluid (D42, D56). All formulations were able to reduce clinical symptoms, lung lesions and the M. hyopneumoniae DNA load in the lung, with formulation SWE_TLR being the most effective (RDS_D28–D56 −61.90%, macroscopic lung lesions −88.38%, M. hyopneumoniae DNA load in BAL fluid (D42) −67.28%). Further experiments raised under field conditions are needed to confirm these results and to assess the effect of the vaccines on performance parameters.

[Value of absolute counts of lymphocyte subsets in the early prediction of refractory Mycoplasma pneumoniae pneumonia in children]

OBJECTIVE

To study the value of absolute counts of lymphocyte subsets in the early prediction of refractory Mycoplasma pneumoniae pneumonia (RMPP) in children.

METHODS

A retrospective analysis was performed for the clinical data of 244 children with Mycoplasma pneumoniae pneumonia (MPP). Among these children, 166 had MPP, and 58 had RMPP. The two groups were compared in terms of clinical features and laboratory markers such as lymphocyte subsets, lactate dehydrogenase, C-reactive protein, procalcitonin and immunoglobulin E (IgE). The receiver operating characteristic (ROC) curve was used to evaluate the specific indices for predicting RMMP.

RESULTS

There were significant differences between the two groups in the absolute counts of CD3⁺, CD4⁺, CD19⁺, and CD56⁺ lymphocytes and the serum levels of lactate dehydrogenase, C-reactive protein, and IgE (P<0.05). The ROC curve analysis showed that the absolute counts of CD3⁺, CD4⁺ and CD19⁺ lymphocytes had an area under the ROC curve (AUC) of 0.866, 0.900 and 0.842 respectively in the differential diagnosis of RMPP and MPP, with a sensitivity of 86%, 90% and 82% respectively and a specificity of 75%, 70% and 80% respectively.

CONCLUSIONS

The absolute counts of CD3⁺, CD4⁺ and CD19⁺ lymphocytes can be used to predict RMPP in children.

Systems Immunology Characterization of Novel Vaccine Formulations for Mycoplasma hyopneumoniae Bacterins

We characterized five different vaccine candidates and a commercial vaccine in terms of safety, immunogenicity and using a systems vaccinology approach, with the aim to select novel vaccine candidates against Mycoplasma hyopneumoniae. Seven groups of six M. hyopneumoniae-free piglets were primo- and booster vaccinated with the different experimental bacterin formulations, the commercial vaccine Hyogen® as a positive control or PBS as a negative control. The experimental bacterin was formulated with cationic liposomes + c-di-AMP (Lipo_AMP), cationic liposomes + Toll-like receptor (TLR) 2/1, TLR7, and TLR9 ligands (TLR ligands; Lipo_TLR), micro-particles + TLR ligands (PLGA_TLR), squalene-in-water emulsion + TLR ligands (SWE_TLR), or DDA:TDB liposomes (Lipo_DDA:TDB). Lipo_DDA:TDB and Lipo_AMP were the most potent in terms of serum antibody induction, and Lipo_DDA:TDB, Lipo_AMP, and SWE_TLR significantly induced Th1 cytokine-secreting T-cells. Only PLGA_TLR appeared to induce Th17 cells, but was unable to induce serum antibodies. The transcriptomic analyses demonstrated that the induction of inflammatory and myeloid cell blood transcriptional modules (BTM) in the first 24 h after vaccination correlated well with serum antibodies, while negative correlations with the same modules were found 7 days post-vaccination. Furthermore, many cell cycle and T-cell BTM upregulated at day seven correlated positively with adaptive immune responses. When comparing the delivery of the identical TLR ligands with the three formulations, we found SWE_TLR to be more potent in the induction of an early innate immune response, while the liposomal formulation more strongly promoted late cell cycle and T-cell BTM. For the PLGA formulation we found signs of a delayed and weak perturbation of these BTM. Lipo_AMP was found to be the most potent vaccine at inducing a BTM profile similar to that correlating with adaptive immune response in this and other studies. Taken together, we identified four promising vaccine candidates able to induce M. hyopneumoniae-specific antibody and T-cell responses. In addition, we have adapted a systems vaccinology approach developed for human to pigs and demonstrated its capacity in identifying early immune signatures in the blood relating to adaptive immune responses. This approach represents an important step in a more rational design of efficacious vaccines for pigs.

Intra-Species and Inter-Species Differences in Cytokine Production by Porcine Antigen-Presenting Cells Stimulated by Mycoplasma hyopneumoniae, M. hyorhinis, and M. flocculare

Mycoplasma hyorhinis and M. flocculare are commonly co-isolated with M. hyopneumoniae (primary agent of swine enzootic pneumonia) in gross pneumonia-like lesions, but their involvement in the disease process remains unknown. T cells play an immuno-pathological role during mycoplasmal infections. Dendritic cells (DCs) are major antigen-presenting cells involved in T cell activation and differentiation. In this study, we investigated cytokine (IL-6, IL-8, IL-10, IL-12, and TNF-α) production by porcine bone-marrow-derived DCs (BM-DCs) stimulated by M. hyopneumoniae, M. hyorhinis, and/or M. flocculare. Results showed that cytokine production levels were relatively homogenous for all evaluated M. hyopneumoniae strains in contrast to M. hyorhinis and M. flocculare strains. The most noteworthy inter-species differences were the overall (i) lower IL-12 production capacity of M. hyopneumoniae, and (ii) higher TNF-α production capacity of M. flocculare. Co-stimulation of BM-DCs showed that M. hyorhinis dominated the IL-12 production independently of its association with M. hyopneumoniae or M. flocculare. In addition, a decreased BM-DC production of TNF-α was generally observed in the presence of mycoplasma associations. Lastly, M. flocculare association with M. hyopneumoniae increased BM-DC ability to secrete IL-10. A higher cytotoxicity level in BM-DCs stimulated by M. hyorhinis was also observed. Overall, this study demonstrated that the combination of M. hyorhinis or M. flocculare with M. hyopneumoniae may participate to the modulation of the immune response that might affect the final disease outcome.

Interleukin-17A Exacerbates Disease Severity in BALB/c Mice Susceptible to Lung Infection with Mycoplasma pulmonis

Mycoplasmas are atypical bacteria that disrupt the immune response to promote respiratory tract infections and secondary complications. However, not every immunologic response that protects or damages the host during mycoplasma infection is known. Interleukin-17A (IL-17A) is elevated in individuals infected with mycoplasmas, but how IL-17A and its cellular sources dictate disease outcome remains unclear. Here, IL-17A is hypothesized to worsen disease in individuals susceptible to mycoplasma infection. Thus, monoclonal anti-IL-17A antibodies were given to disease-susceptible BALB/c mice and disease-resistant C57BL/6 mice infected with Mycoplasma pulmonis Neutralizing the function of IL-17A using anti-IL-17A antibodies reduced disease severity during M. pulmonis infection in BALB/c, but not C57BL/6, mice. Neutralizing IL-17A also reduced the incidence of neutrophilic lung lesions during infection in BALB/c mice. Reduced pathology occurred without impacting the bacterial burden, demonstrating that IL-17A is not required for mycoplasma clearance. The main source of IL-17A throughout infection in BALB/c mice was CD4⁺ T cells, and neutralizing IL-17A after infiltration of the lungs by T cells reduced disease severity, identifying the Th17 response as a herald of late mycoplasma pathology in susceptible mice. Neutralizing IL-17A did not further reduce disease during M. pulmonis infection in BALB/c mice depleted of neutrophils, suggesting that IL-17A requires the presence of pulmonary neutrophils to worsen respiratory pathology. IL-17A is a pathological element of murine respiratory mycoplasma infection. Using monoclonal antibodies to neutralize IL-17A could reduce disease severity during mycoplasma infection in humans and domesticated animals.

Transcriptome Analysis of Bronchoalveolar Lavage Fluid From Children With Mycoplasma pneumoniae Pneumonia Reveals Natural Killer and T Cell-Proliferation Responses

Background

Mycoplasma pneumoniae pneumonia (MPP) is one of the most common community-acquired pneumonia; this study is to explore the immune-pathogenesis of children MPP.

Methods

Next-generation transcriptome sequencing was performed on the bronchoalveolar lavage fluid cells from six children with MPP and three children with foreign body aspiration as control. Some of the results had been validated by quantitative real-time PCR in an expanded group of children.

Results

Results revealed 810 differentially expressed genes in MPP group comparing to control group, of which 412 genes including RLTPR, CARD11 and RASAL3 were upregulated. These upregulated genes were mainly enriched in mononuclear cell proliferation and signaling biological processes. Kyoto encyclopedia of genes and genomes pathway analysis revealed that hematopoietic cell linage pathway, natural killer cell-mediated cytotoxicity pathway, and T cell receptor signaling pathway were significantly upregulated in MPP children. In addition, significant alternative splicing events were found in GNLY and SLC11A1 genes, which may cause the differential expressions of these genes.

Conclusion

Our results suggest that NK and CD8+ T cells are over activated and proliferated in MPP children; the upregulated IFNγ, PRF1, GZMB, FASL, and GNLY may play important roles in the pathogenesis of children MPP.

Autoimmune-Disease-Prone NOD Mice Help To Reveal a New Genetic Locus for Reducing Pulmonary Disease Caused by Mycoplasma pulmonis

Mycoplasmas are bacterial pathogens of a range of animals, including humans, and are a common cause of respiratory disease. However, the host genetic factors that affect resistance to infection or regulate the resulting pulmonary inflammation are not well defined. We and others have previously demonstrated that nonobese diabetic (NOD) mice can be used to investigate disease loci that affect bacterial infection and autoimmune diabetes. Here we show that NOD mice are more susceptible than C57BL/6 (B6) mice to infection with Mycoplasma pulmonis, a natural model of pulmonary mycoplasmosis. The lungs of infected NOD mice had higher loads of M. pulmonis and more severe inflammatory lesions. Moreover, congenic NOD mice that harbored different B6-derived chromosomal intervals enabled identification and localization of a new mycoplasmosis locus, termed Mpr2, on chromosome 13. These congenic NOD mice demonstrated that the B6 allele for Mpr2 reduced the severity of pulmonary inflammation caused by infection with M. pulmonis and that this was associated with altered cytokine and chemokine concentrations in the infected lungs. Mpr2 also colocalizes to the same genomic interval as Listr2 and Idd14, genetic loci linked to listeriosis resistance and autoimmune diabetes susceptibility, respectively, suggesting that allelic variation within these loci may affect the development of both infectious and autoimmune disease.

Antibody-dependent fragmentation is a newly identified mechanism of cell killing in vivo

The prevailing view is that therapeutic antibodies deplete cells through opsonization and subsequent phagocytosis, complement-dependent lysis or antibody-dependent cellular-cytotoxicity. We used high resolution in vivo imaging to identify a new antibody-dependent cell death pathway where Kupffer cells ripped large fragments off crawling antibody-coated iNKT cells. This antibody-dependent fragmentation process resulted in lethality and depletion of crawling iNKT cells in the liver sinusoids and lung capillaries. iNKT cell depletion was Fcy-receptor dependent and required iNKT cell crawling. Blood, spleen or joint iNKT cells that did not crawl were not depleted. The antibody required high glycosylation for sufficiently strong binding of the iNKT cells to the Fc Receptors on Kupffer cells. Using an acetaminophen overdose model, this approach functionally depleted hepatic iNKT cells and affected the severity of liver injury. This study reveals a new mechanism of antibody-dependent killing in vivo and raises implications for the design of new antibodies for cancer and auto-reactive immune cells.

Ureaplasma urealyticum and U. parvum in sexually active women attending public health clinics in Brazil

Ureaplasma urealyticum and U. parvum have been associated with genital infections. The purpose of this study was to detect the presence of ureaplasmas and other sexually transmitted infections in sexually active women from Brazil and relate these data to demographic and sexual health, and cytokines IL-6 and IL-1β. Samples of cervical swab of 302 women were examined at the Family Health Units in Vitória da Conquista. The frequency of detection by conventional PCR was 76·2% for Mollicutes. In qPCR, the frequency found was 16·6% for U. urealyticum and 60·6% U. parvum and the bacterial load of these microorganisms was not significantly associated with signs and symptoms of genital infection. The frequency found for Trichomonas vaginalis, Neisseria gonorrhoeae, Gardnerella vaginalis and Chlamydia trachomatis was 3·0%, 21·5%, 42·4% and 1·7%, respectively. Higher levels of IL-1β were associated with control women colonized by U. urealyticum and U. parvum. Increased levels of IL-6 were associated with women who exhibited U. parvum. Sexually active women, with more than one sexual partner in the last 3 months, living in a rural area were associated with increased odds of certain U. parvum serovar infection.

Effects of mycoplasmal pneumonia of swine (MPS) lung lesion-selected Landrace pigs on MPS resistance and immune competence in three-way crossbred pigs

To clarify the genetic influence of mycoplasmal pneumonia of swine (MPS) lesion-selected Landrace (La) on MPS resistance and immune characteristics in three-way crossbred pigs (LaWaDa), the LaWaDa pigs were compared with the non-selected crossbred (LbWbDb) and purebred (La) pigs. The MPS lesion score in the three lines was as follows: La line < LaWaDa line < LbWbDb line, with significant differences among the lines. The proportions of myeloid cells and T cells were lower and higher, respectively, in the LaWaDa pigs compared with those in the other two lines. Messenger RNA (mRNA) expression of interleukin (IL)-6, IL-10, transforming growth factor-β, and interferon-γ in peripheral blood was significantly increased after vaccination in the La and LaWaDa lines. IL-4 mRNA expression in the LaWaDa line was intermediate to the La and LbWbDb lines. Furthermore, principal component analysis for immune traits and MPS lesions was executed to clarify the characteristics of each pig line. These findings suggest that the immune responses in the three pig lines are genetically distinct and that MPS resistance and some immunity characteristics from the La line were transmitted to the three-way crossbred pigs.

Regulatory CD4+CD25+ T Cells Dampen Inflammatory Disease in Murine Mycoplasma Pneumonia and Promote IL-17 and IFN-γ Responses

Mycoplasmas cause respiratory diseases characterized by persistent infection and chronic airway inflammation. Mycoplasma lung disease is immunopathologic, with CD4⁺ Th cells determining both disease severity and resistance to infection. Th2 cell responses promote immunopathology, while Th1 cells confer resistance to infection. However, regulatory CD4⁺ T cells may also have a role in the pathogenesis of mycoplasma respiratory diseases. We hypothesized Treg cells control the severity of the inflammatory lesions and may also promote persistence of infection. To examine this, BALB/c mice were depleted of CD25⁺ cells, and had increased disease severity due to Mycoplasma pulmonis infection. Increases in mycoplasma antibody responses and lymphocyte infiltration into lungs also occurred after CD25⁺ cell depletion. CD4⁺CD25⁺ regulatory T cells promoted IFN-γ and IL-17 mycoplasma-specific CD4⁺ T cell responses in vitro and in vivo, while dampening IL-13⁺ Th responses. Neither IL-10 nor TGF-ß expression was detected in CD4⁺CD25⁺ T cells from lymph nodes. Thus, a regulatory T cell population plays an important role in controlling damaging immune responses in mycoplasma respiratory disease but does not contribute to persistence of infection. It appears that a regulatory T cell population preferentially dampens Th2 cell-mediated inflammatory responses to mycoplasma through a mechanism independent of IL-10 or TGF-ß characteristic of “classic” Treg cells.

Neither classical nor alternative macrophage activation is required for Pneumocystis clearance during immune reconstitution inflammatory syndrome

Pneumocystis is a respiratory fungal pathogen that causes pneumonia (Pneumocystis pneumonia [PcP]) in immunocompromised patients. Alveolar macrophages are critical effectors for CD4(+) T cell-dependent clearance of Pneumocystis, and previous studies found that alternative macrophage activation accelerates fungal clearance during PcP-related immune reconstitution inflammatory syndrome (IRIS). However, the requirement for either classically or alternatively activated macrophages for Pneumocystis clearance has not been determined. Therefore, RAG2(-/-) mice lacking either the interferon gamma (IFN-γ) receptor (IFN-γR) or interleukin 4 receptor alpha (IL-4Rα) were infected with Pneumocystis. These mice were then immune reconstituted with wild-type lymphocytes to preserve the normal T helper response while preventing downstream effects of Th1 or Th2 effector cytokines on macrophage polarization. As expected, RAG2(-/-) mice developed severe disease but effectively cleared Pneumocystis and resolved IRIS. Neither RAG/IFN-γR(-/-) nor RAG/IL-4Rα(-/-) mice displayed impaired Pneumocystis clearance. However, RAG/IFN-γR(-/-) mice developed a dysregulated immune response, with exacerbated IRIS and greater pulmonary function deficits than those in RAG2 and RAG/IL-4Rα(-/-) mice. RAG/IFN-γR(-/-) mice had elevated numbers of lung CD4(+) T cells, neutrophils, eosinophils, and NK cells but severely depressed numbers of lung CD8(+) T suppressor cells. Impaired lung CD8(+) T cell responses in RAG/IFN-γR(-/-) mice were associated with elevated lung IFN-γ levels, and neutralization of IFN-γ restored the CD8 response. These data demonstrate that restricting the ability of macrophages to polarize in response to Th1 or Th2 cytokines does not impair Pneumocystis clearance. However, a cell type-specific IFN-γ/IFN-γR-dependent mechanism regulates CD8(+) T suppressor cell recruitment, limits immunopathogenesis, preserves lung function, and enhances the resolution of PcP-related IRIS.

Immunogenic properties and mycoplasmal pneumonia of swine (MPS) lung lesions in Large White pigs selected for higher peripheral blood immune capacity

Immunogenic properties and mycoplasmal pneumonia of swine (MPS) lung lesions were compared between the immunity-selected Large White line and the non-selected Large White line. The selected Large White line showed a higher level of pulmonary MPS lesions compared with the non-selected Large White line. Subsequent to vaccination, the percentage of natural killer cells and T cells (CD3(+) CD4(+) CD8(-) and CD3(+) CD4(-) CD8(+) T cells) were significantly increased in the non-selected line but remained unchanged in the immunity-selected Large White line. Secretion of Mycoplasma hyopneumoniae vaccine-specific immunoblogulin G and phagocyte activity in peripheral blood were significantly higher in the immunity-selected Large White line than in the non-selected line. Expression of interleukin (IL)-4 and IL-6 messenger RNA in hilar lymph nodes was significantly lower in the immunity-selected Large White line than in the non-selected line. However, expression of IL-10 in all immune tissues was significantly higher in the immunity-selected Large White line. These results suggest that the selection for high immunity was not effective in increasing resistance to MPS lung lesions.

Immunogenic properties of Landrace pigs selected for resistance to mycoplasma pneumonia of swine

Mycoplasma pneumonia of swine (MPS) lung lesions and immunogenic properties were compared between a Landrace line that was genetically selected for reduced incidence of pulmonary MPS lesions, and a non‐selected Landrace line. The MPS‐selected Landrace line showed significantly lower degrees of pulmonary MPS lesions compared with the non‐selected Landrace line. When changes in immunity before and after vaccination were compared, the percentage of B cells in the peripheral blood of the MPS‐selected Landrace line was significantly lower than that of the non‐selected line. Furthermore, the concentration of growth hormone and the mitogen activity of peripheral blood mononuclear cells in the MPS‐selected Landrace line showed significantly (P < 0.05) lower increases after vaccination than the non‐selected line. Conversely, the concentration of peripheral blood interferon (IFN)‐γ and salivary immunoglobulin A (IgA) after Mycoplasma hyopneumoniae vaccination was significantly higher in the MPS‐selected Landrace line than in the non‐selected line. Gene expression of toll‐like receptor (TLR)2 and TLR4 was significantly higher in the MPS‐selected Landrace line in immune tissues, with the exception of the hilar lymph nodes. The present results suggest that peripheral blood IFN‐γ, salivary IgA TLR2, and TLR4 are important immunological factors influencing the development of MPS lesions.

Antigen-pulsed bone marrow-derived and pulmonary dendritic cells promote Th2 cell responses and immunopathology in lungs during the pathogenesis of murine Mycoplasma pneumonia

Mycoplasmas are a common cause of pneumonia in humans and animals, and attempts to create vaccines have not only failed to generate protective host responses, but they have exacerbated the disease. Mycoplasma pulmonis causes a chronic inflammatory lung disease resulting from a persistent infection, similar to other mycoplasma respiratory diseases. Using this model, Th1 subsets promote resistance to mycoplasma disease and infection, whereas Th2 responses contribute to immunopathology. The purpose of the present study was to evaluate the capacity of cytokine-differentiated dendritic cell (DC) populations to influence the generation of protective and/or pathologic immune responses during M. pulmonis respiratory disease in BALB/c mice. We hypothesized that intratracheal inoculation of mycoplasma Ag-pulsed bone marrow-derived DCs could result in the generation of protective T cell responses during mycoplasma infection. However, intratracheal inoculation (priming) of mice with Ag-pulsed DCs resulted in enhanced pathology in the recipient mice when challenged with mycoplasma. Inoculation of immunodeficient SCID mice with Ag-pulsed DCs demonstrated that this effect was dependent on lymphocyte responses. Similar results were observed when mice were primed with Ag-pulsed pulmonary, but not splenic, DCs. Lymphocytes generated in uninfected mice after the transfer of either Ag-pulsed bone marrow-derived DCs or pulmonary DCs were shown to be IL-13(+) Th2 cells, known to be associated with immunopathology. Thus, resident pulmonary DCs most likely promote the development of immunopathology in mycoplasma disease through the generation of mycoplasma-specific Th2 responses. Vaccination strategies that disrupt or bypass this process could potentially result in a more effective vaccination.

Interleukin-23 (IL-23) deficiency disrupts Th17 and Th1-related defenses against Streptococcus pneumoniae infection

Resolution of acute of infection caused by capsular Streptococcus pneumoniae infection in the absence of effective antibiotic therapy requires tight regulation of immune and inflammatory responses. To provide new mechanistic insight of the requirements needed for innate host defenses against acute S. pneumoniae infection, we examined how IL-23 deficiency mediated acute pulmonary resistance. We found that IL-23 deficient mice were more susceptible to bacterial colonization in the lungs corresponding with greater bacterial dissemination. The lack of IL-23 was found to decrease IL-6 and IL-12p70 cytokine levels in bronchiolar lavage within the initial day after infection. Pulmonary leukocytes isolated from infected IL-23 deficient mice demonstrated a dramatic decrease in IL-17A and IFN-γ in response to heat-killed organisms. These findings corresponded with significant abrogation of neutrophilic infiltrate in the lungs compared to IL-23 competent mice. Whereas previous studies have shown opposing influences of IL-12/IL-23 regulation, our findings suggest a concordant dependency of IL-23 expression on Th1 and Th17-related responses.

Dendritic cells are the major antigen presenting cells in inflammatory lesions of murine Mycoplasma respiratory disease

Mycoplasmas cause chronic respiratory diseases in animals and humans, and to date, development of vaccines have been problematic. Using a murine model of mycoplasma pneumonia, lymphocyte responses, specifically T cells, were shown to confer protection as well as promote immunopathology in mycoplasma disease. Because T cells play such a critical role, it is important to define the role of antigen presenting cells (APC) as these cells may influence either exacerbation of mycoplasma disease pathogenesis or enhancement of protective immunity. The roles of APC, such as dendritic cells and/or macrophages, and their ability to modulate adaptive immunity in mycoplasma disease are currently unknown. Therefore, the purpose of this study was to identify individual pulmonary APC populations that may contribute to the activation of T cell responses during mycoplasma disease pathogenesis. The present study indeed demonstrates increasing numbers of CD11c⁻ F4/80⁺ cells, which contain macrophages, and more mature/activated CD11c⁺ F4/80⁻ cells, containing DC, in the lungs after infection. CD11c⁻ F4/80⁺ macrophage-enriched cells and CD11c⁺ F4/80⁻ dendritic cell-enriched populations showed different patterns of cytokine mRNA expression, supporting the idea that these cells have different impacts on immunity in response to infection. In fact, DC containing CD11c⁺ F4/80⁻ cell populations from the lungs of infected mice were most capable of stimulating mycoplasma-specific CD4⁺ Th cell responses in vitro. In vivo, these CD11c⁺F4/80⁻ cells were co-localized with CD4⁺ Th cells in inflammatory infiltrates in the lungs of mycoplasma-infected mice. Thus, CD11c⁺F4/80⁻ dendritic cells appear to be the major APC population responsible for pulmonary T cell stimulation in mycoplasma-infected mice, and these dendritic cells likely contribute to responses impacting disease pathogenesis.

Oral inoculation of young dairy calves with Mycoplasma bovis results in colonization of tonsils, development of otitis media and local immunity

Because M. bovis otitis media is an economically important problem, there is a need to understand the pathogenesis of disease, not only to improve our understanding of the factors contributing to the development of this disease but also to inform the development of improved diagnostic tests and therapy. Oral ingestion of M. bovis-contaminated milk is linked, but not definitively proven, to development of otitis media. In the current study, we demonstrate that oral ingestion of M. bovis infected colostrum can result in an ascending infection and development of otitis media. Importantly, M. bovis was found to have a previously unrecognized tendency for colonization of the tonsils of calves, which most likely contributed to the subsequent development of otitis media. In contrast, transtracheal inoculation failed to produce clinically significant upper respiratory tract disease, although did induce lower respiratory tract disease. The upper respiratory tract was the major site of M. bovis-specific B cell and mucosal IgA responses in calves inoculated by the oral route. The oral inoculation route of infection presented here is particularly suited to the study of host-pathogen interactions during initial colonization of the tonsils, expansion of infection and dissemination to the lower respiratory tract and middle ear. In addition, it could be used to investigate potential new preventative or control strategies, especially those aimed at limiting colonization of the tonsils and/or spread to the middle ear.

CD8+ T cells and risk for bacterial pneumonia and all-cause mortality among HIV-infected women

BACKGROUND

Bacterial pneumonia risk is disproportionately high among those infected with HIV. This risk is present across all CD4(+) T-cell levels (TCLs), suggesting that additional factors govern susceptibility. This study examines CD8(+) TCLs and risk for HIV-associated bacterial pneumonia and all-cause mortality.

METHODS

Demographic, clinical, and laboratory data were obtained for 885 HIV-infected women enrolled in the HIV Epidemiologic Research Study (HERS). Bacterial pneumonia cases were identified using clinical, microbiological, and radiographic criteria. CD8(+) TCLs were assessed at 6-month intervals. Statistical methods included Cox proportional hazards regression modeling and covariate-adjusted survival estimates.

RESULTS

Relative to a referent CD8(+) TCL of 401-800 cells per cubic millimeter, risk for bacterial pneumonia was significantly higher when CD8(+) TCLs were <400 (hazard ratio 1.65, P = 0.017, 95% confidence interval 1.10 to 2.49), after adjusting for age, CD4(+) TCL, viral load, and antiretroviral use. There was also a significantly higher risk of death when CD8(+) TCLs were ≤400 cells per cubic millimeter (hazard ratio 1.45, P = 0.04, 95% confidence interval 1.02 to 2.06). Covariate-adjusted survival estimates revealed shorter time to pneumonia and death in this CD8(+) TCL category, and the overall associations of the categorized CD8(+) TCL with bacterial pneumonia and all-cause mortality were each statistically significant (P = 0.017 and P < 0.0001, respectively).

CONCLUSIONS

CD8(+) TCL ≤400 cells per cubic millimeter was associated with increased risk for pneumonia and all-cause mortality in HIV-infected women in the HERS cohort, suggesting that CD8(+) TCL could serve as an adjunctive biomarker of pneumonia risk and mortality in HIV-infected individuals.

Corticotropin-releasing hormone receptor-1 and 2 activity produces divergent resistance against stress-induced pulmonary Streptococcus pneumoniae infection

Utilizing a murine model of S. pneumoniae infection and restraint stress, we determined how corticotropin releasing hormone (CRH-R) receptors impacts disease. CRH-R1 (antalarmin) and CRH-R2 (astressin2B) antagonists were administered intraperitoneally prior to restraint stress followed by pulmonary S. pneumoniae infection. CRH-R1 inhibition is not protective against pneumococcal disease induced by stress. Conversely, CRH-R2 inhibition attenuates stress-induced bacterial growth and significantly prevented severe sepsis. Neutrophillic responses were associated with CRH receptor-specific disease outcome providing a potential cellular target for stress-induced susceptibility to the development of severe pneumococcal disease. CRH receptor-mediated effects on immune responses could prove valuable for novel therapeutics.

CD8+ cells enhance resistance to pulmonary serotype 3 Streptococcus pneumoniae infection in mice

Despite the success of the pneumococcal conjugate vaccine, pneumococcal pneumonia remains a significant clinical problem, and there is still much to learn about natural resistance and cellular immunity to pneumococcus. We investigated the role of T lymphocytes in resistance to serotype (ST) 3 Streptococcus pneumoniae in an intranasal infection model in C57BL/6 (wild-type [Wt]) and CD8(+) (CD8(-/-))- and CD4(+) (MHC class II(-/-))-deficient mice. CD8(-/-) mice exhibited significantly more bacterial dissemination and lung inflammation and a significantly more lethal phenotype than Wt mice. However, there was no difference in the bacterial dissemination, lung inflammation, or survival of Wt and MHC class II(-/-) mice. Perforin (Pfn)(-/-) and IFN-γ(-/-) mice, which were used to dissect the role of CD8(+) T cells in our model, also exhibited a more lethal survival phenotype than Wt mice. Comparison of lung chemokine/cytokine levels by Luminex and cellular recruitment by FACS in Wt mice and knockout strains revealed that CD8(-/-) and IFN-γ(-/-) mice, which had the most lethal survival phenotype, had more CD4(+)IL-17(+) T (Th17) cells, IL-17, neutrophil chemoattractants, and lung neutrophils, and fewer regulatory T cells than Wt mice. CD4(+) T cell depletion improved the survival of ST-infected CD8(-/-) mice, and survival studies in Th17-deficient mice revealed that the Th17 response was dispensable for ST3 resistance in our model. Taken together, these findings demonstrate that CD8(+) cells are required, but CD4(+) T cells are dispensable for resistance to ST3 pneumonia in mice and suggest a previously unsuspected role for CD8(+) cells in modulating the inflammatory response to ST3.

Host adaptive immunity deficiency in severe pandemic influenza

Introduction

Pandemic A/H1N1/2009 influenza causes severe lower respiratory complications in rare cases. The association between host immune responses and clinical outcome in severe cases is unknown.

Methods

We utilized gene expression, cytokine profiles and generation of antibody responses following hospitalization in 19 critically ill patients with primary pandemic A/H1N1/2009 influenza pneumonia for identifying host immune responses associated with clinical outcome. Ingenuity pathway analysis 8.5 (IPA) (Ingenuity Systems, Redwood City, CA) was used to select, annotate and visualize genes by function and pathway (gene ontology). IPA analysis identified those canonical pathways differentially expressed (P < 0.05) between comparison groups. Hierarchical clustering of those genes differentially expressed between groups by IPA analysis was performed using BRB-Array Tools v.3.8.1.

Results

The majority of patients were characterized by the presence of comorbidities and the absence of immunosuppressive conditions. pH1N1 specific antibody production was observed around day 9 from disease onset and defined an early period of innate immune response and a late period of adaptive immune response to the virus. The most severe patients (n = 12) showed persistence of viral secretion. Seven of the most severe patients died. During the late phase, the most severe patient group had impaired expression of a number of genes participating in adaptive immune responses when compared to less severe patients. These genes were involved in antigen presentation, B-cell development, T-helper cell differentiation, CD28, granzyme B signaling, apoptosis and protein ubiquitination. Patients with the poorest outcomes were characterized by proinflammatory hypercytokinemia, along with elevated levels of immunosuppressory cytokines (interleukin (IL)-10 and IL-1ra) in serum.

Conclusions

Our findings suggest an impaired development of adaptive immunity in the most severe cases of pandemic influenza, leading to an unremitting cycle of viral replication and innate cytokine-chemokine release. Interruption of this deleterious cycle may improve disease outcome.

Interferon gamma and interleukin 4 have contrasting effects on immunopathology and the development of protective adaptive immunity against mycoplasma respiratory disease

For vaccine development, it is critical to understand the regulatory mechanisms determining resistance and immunopathology against mycoplasma respiratory diseases. The present study evaluated the contribution of the polarizing cytokines interferon gamma (IFN-gamma) and interleukin 4 (IL-4) in the regulation of mycoplasma-specific immunity. The absence of a single cytokine (either IFN-gamma or IL-4) uniquely altered the expression of multiple chemokines and cytokines in the lungs of uninfected mice and influenced responses to mycoplasma infection. Most importantly, prior nasal-pulmonary immunization of IFN-gamma(-/-) mice led to exacerbated mycoplasma disease, whereas immunized IL-4(-/-) mice were dramatically more resistant than wild-type mice. Helper T cell type 2 responses in IFN-gamma(-/-) mice corresponded to immunopathologic reactions that developed after mycoplasma infection or immunization. Thus, adaptive immunity clearly can independently promote either protection or immunopathology against mycoplasma infection, and optimal vaccination appears to be dependent on promoting protective IFN-gamma-dependent networks (perhaps helper T cell type 1 responses) while minimizing the effect of IL-4-mediated responses, which dampen the generation of protective immunity.

Role of 4-1BB receptor in the control played by CD8(+) T cells on IFN-gamma production by Mycobacterium tuberculosis antigen-specific CD4(+) T Cells

Background

Antigen-specific IFN-γ producing CD4⁺ T cells are the main mediators of protection against Mycobacterium tuberculosis infection both under natural conditions and following vaccination. However these cells are responsible for lung damage and poor vaccine efficacy when not tightly controlled. Discovering new tools to control nonprotective antigen-specific IFN-γ production without affecting protective IFN-γ is a challenge in tuberculosis research.

Methods and Findings

Immunization with DNA encoding Ag85B, a candidate vaccine antigen of Mycobacterium tuberculosis, elicited in mice a low but protective CD4⁺ T cell-mediated IFN-γ response, while in mice primed with DNA and boosted with Ag85B protein a massive increase in IFN-γ response was associated with loss of protection. Both protective and non-protective Ag85B-immunization generated antigen-specific CD8⁺ T cells which suppressed IFN-γ-secreting CD4⁺ T cells. However, ex vivo ligation of 4-1BB, a member of TNF-receptor super-family, reduced the massive, non-protective IFN-γ responses by CD4⁺ T cells in protein-boosted mice without affecting the low protective IFN-γ-secretion in mice immunized with DNA. This selective inhibition was due to the induction of 4-1BB exclusively on CD8⁺ T cells of DNA-primed and protein-boosted mice following Ag85B protein stimulation. The 4-1BB-mediated IFN-γ inhibition did not require soluble IL-10, TGF-β, XCL-1 and MIP-1β. In vivo Ag85B stimulation induced 4-1BB expression on CD8⁺ T cells and in vivo 4-1BB ligation reduced the activation, IFN-γ production and expansion of Ag85B-specific CD4⁺ T cells of DNA-primed and protein-boosted mice.

Conclusion/Significance

Antigen-specific suppressor CD8⁺ T cells are elicited through immunization with the mycobacterial antigen Ag85B. Ligation of 4-1BB receptor further enhanced their suppressive activity on IFN-γ-secreting CD4⁺ T cells. The selective expression of 4-1BB only on CD8⁺ T cells in mice developing a massive, non-protective IFN-γ response opens novel strategies for intervention in tuberculosis pathology and vaccination through T-cell co-stimulatory-based molecular targeting.

Toll-like receptor 2 (TLR2) plays a major role in innate resistance in the lung against murine Mycoplasma

Mycoplasma lipoproteins are recognized by Toll-like receptors (TLR), but TLRs' role in responses to infection are unknown. Mycoplasma pulmonis is a naturally occurring respiratory pathogen in mice. In the current study, we used TLR-transfected HEK cells and TLR2(-/-) bone marrow-derived dendritic cells to demonstrate TLR2-mediated events are important in the initial host-mycoplasma interactions promoting cytokine responses. As we found alveolar macrophages expressed TLR1, TLR2 and TLR6 mRNAs, a role for TLR2 in innate immune clearance in lungs was examined. Three days post-infection, TLR2(-/-) mice had higher M. pulmonis numbers in lungs, but not in nasal passages. However, TLR2(-/-) mice had higher lung cytokine levels, indicating TLR2-independent mechanisms are also involved in host responses. Thus, TLR2 plays a critical role in the ability of innate immunity to determine M. pulmonis numbers in the lung, and it is likely that early after respiratory infection that TLR2 recognition of M. pulmonis triggers initial cytokine responses of host cells.

A murine model of stress controllability attenuates Th2-dominant airway inflammatory responses

Epidemiological and experimental studies suggest a positive correlation between chronic respiratory inflammatory disease and the ability to cope with adverse stress. Interactions between neuroendocrine and immune systems are believed to provide insight toward the biological mechanisms of action. The utility of an experimental murine model was employed to investigate the immunological consequences of stress-controllability and ovalbumin-induced airway inflammation. Pre-conditioned uncontrollable stress exacerbated OVA-induced lung histopathological changes that were typical of Th2-predominant inflammatory response along respiratory tissues. Importantly, mice given the ability to exert control over aversive stress attenuated inflammatory responses and reduced lung pathology. This model represents a means of investigating the neuro-immune axis in defining mechanisms of stress and respiratory disease.

Role of CD4+ and CD8+ T cells in clearance of primary pulmonary infection with Coxiella burnetii

The mechanisms of the primary adaptive immune response to Coxiella burnetii are not well known. Following inoculation of the lungs with C. burnetii Nine Mile phase I (NMI), SCID mice developed pneumonia and splenomegaly and succumbed to infection, whereas wild-type mice cleared the infection by 24 days. SCID mice reconstituted with either CD4+ T cells or CD8+ T cells alone were able to control the infection, indicating that the presence of either type of T cells was sufficient to control infection, and B cells were not necessary for primary immunity. Similarly, wild-type mice depleted of either CD4+ T cells or CD8+ T cells controlled infections in their lungs, but these mice were highly susceptible if they were depleted of both types of T cells. However, compared to CD4+ T-cell-dependent protection, CD8+ T-cell-dependent protection resulted in less inflammation in the lungs and less growth of bacteria in the spleens.

NK cells interfere with the generation of resistance against mycoplasma respiratory infection following nasal-pulmonary immunization

The purpose of the present study was to determine the impact of NK cells on the development of protective adaptive immunity in response to nasal-pulmonary immunization against mycoplasma. Depletion of NK cells before nasal-pulmonary immunization enhanced resistance to mycoplasma respiratory infection. The effect of NK cells on the generation of protective immunity in lungs was dependent on lymphoid cells, as immunization of either SCID mice or immunocompetent mice depleted of CD4(+) T cells did not demonstrate any increased resistance in the presence or absence of NK cells. The presence of NK cells at the time of nasal-pulmonary immunization modulated mycoplasma-specific cytokine responses in lungs and lower respiratory nodes. In particular, NK cells skewed the mycoplasma-specific T cell cytokine responses in the draining lymph nodes to higher IL-4, IL-13, and IL-17 while lowering IFN-gamma responses. Adoptive transfer of total lung lymphocytes isolated from immunized mice into naive mice led to a significant reduction in the mycoplasma numbers in lungs, and the resistance was greater if cells were obtained from immunized mice that were depleted of NK cells. Similar results were obtained if purified B cells, T cells, or CD4(+) T cells were used. Interestingly, this is the first time that a favorable role of functional CD4(+) T cells in mediating protection in mycoplasma respiratory disease was demonstrated. Thus, NK cells can influence the responses of multiple lymphocyte populations capable of mediating resistance to mycoplasma infection.

The impact of steroids given with macrolide therapy on experimental Mycoplasma pneumoniae respiratory infection

BACKGROUND

Systemic steroids have been advocated in addition to antimicrobial therapy for severe Mycoplasma pneumoniae pneumonia. We evaluated the efficacy of clarithromycin, dexamethasone, and combination therapy for M. pneumoniae respiratory infection.

METHODS

Mice infected with M. pneumoniae were treated with clarithromycin, dexamethasone, combined clarithromycin/dexamethasone, or placebo daily; mice were evaluated at baseline and after 1, 3, and 6 days of therapy. Outcome variables included M. pneumoniae culture, lung histopathologic score (HPS), and bronchoalveolar lavage cytokine, chemokine, and growth factor concentrations.

RESULTS

Clarithromycin monotherapy resulted in the greatest reductions in M. pneumoniae concentrations. After 3 days of treatment, combination therapy significantly reduced lung HPS compared with placebo, clarithromycin, and dexamethasone alone, whereas, after 6 days of therapy, clarithromycin alone and combination therapy significantly reduced lung HPS compared with placebo. Concentrations of interleukin (IL)-12 p40, RANTES, macrophage chemotactic protein-1, and cytokine-induced neutrophil chemoattractant were significantly lower in mice treated with clarithromycin alone and/or combination therapy compared with dexamethasone alone and/or placebo; combination therapy resulted in a significantly greater reduction than clarithromycin alone for IL-12 p40 and RANTES.

CONCLUSIONS

Although monotherapy with clarithromycin had the greatest effect on reducing concentrations of M. pneumoniae, combination therapy had the greatest effect on decreasing levels of cytokines and chemokines as well as pulmonary histologic inflammation.

B cells moderate inflammatory progression and enhance bacterial containment upon pulmonary challenge with Mycobacterium tuberculosis

Though much is known about the function of T lymphocytes in the adaptive immune response against Mycobacterium tuberculosis, comparably little is understood regarding the corresponding role of B lymphocytes. Indicating B cells as components of lymphoid neogenesis during pulmonary tuberculosis, we have identified ectopic germinal centers (GCs) in the lungs of infected mice. B cells in these pulmonary lymphoid aggregates express peanut agglutinin and GL7, two markers of GC B cells, as well as CXCR5, and migrate in response to the lymphoid-associated chemokine CXCL13 ex vivo. CXCL13 is negatively regulated by the presence of B cells, as its production is elevated in lungs of B cell-deficient (B cell(-/-)) mice. Upon aerosol with 100 CFU of M. tuberculosis Erdman, B cell(-/-) mice have exacerbated immunopathology corresponding with elevated pulmonary recruitment of neutrophils. Infected B cell(-/-) mice show increased production of IL-10 in the lungs, whereas IFN-gamma, TNF-alpha, and IL-10R remain unchanged from wild type. B cell(-/-) mice have enhanced susceptibility to infection when aerogenically challenged with 300 CFU of M. tuberculosis corresponding with elevated bacterial burden in the lungs but not in the spleen or liver. Adoptive transfer of B cells complements the phenotypes of B cell(-/-) mice, confirming a role for B cells in both modulation of the host response and optimal containment of the tubercle bacillus. As components of ectopic GCs, moderators of inflammatory progression, and enhancers of local immunity against bacterial challenge, B cells may have a greater role in the host defense against M. tuberculosis than previously thought.

The Ag85B protein of Mycobacterium tuberculosis may turn a protective immune response induced by Ag85B-DNA vaccine into a potent but non-protective Th1immune response in mice

Clarifying how an initial protective immune response to tuberculosis may later loose its efficacy is essential to understand tuberculosis pathology and to develop novel vaccines. In mice, a primary vaccination with Ag85B-encoding plasmid DNA (DNA-85B) was protective against Mycobacterium tuberculosis (MTB) infection and associated with Ag85B-specific CD4+ T cells producing IFN-gamma and controlling intramacrophagic MTB growth. Surprisingly, this protection was eliminated by Ag85B protein boosting. Loss of protection was associated with a overwhelming CD4+ T cell proliferation and IFN-gamma production in response to Ag85B protein, despite restraint of Th1 response by CD8+ T cell-dependent mechanisms and activation of CD4+ T cell-dependent IL-10 secretion. Importantly, these Ag85B-responding CD4+ T cells lost the ability to produce IFN-gamma and control MTB intramacrophagic growth in coculture with MTB-infected macrophages, suggesting that the protein-dependent expansion of non-protective CD4+ T cells determined dilution or loss of the protective Ag85B-specific CD4+ induced by DNA-85B vaccination. These data emphasize the need of exerting some caution in adopting aggressive DNA-priming, protein-booster schedules for MTB vaccines. They also suggest that Ag85B protein secreted during MTB infection could be involved in the instability of protective anti-tuberculosis immune response, and actually concur to disease progression.

Cytokine and chemokine transcription profile during Mycoplasma pulmonis infection in susceptible and resistant strains of mice: macrophage inflammatory protein 1beta (CCL4) and monocyte chemoattractant protein 2 (CCL8) and accumulation of CCR5+ Th cells

The progression of murine mycoplasma pneumonia is dependent on T cells and other immune cells. The role of cytokines in immunity are complex, and identifying the network of cytokines produced after infection of mice is essential in dissecting the key cytokine cascades involved mycoplasma disease pathogenesis. In the present study, mRNA expression of 143 different cytokines, chemokines, or receptors were evaluated in lung tissues from both susceptible (BALB/c and C3H/HeN) and resistant (C57BL/6) mice after Mycoplasma pulmonis infection. To accomplish this, membrane-based cDNA microarrays were used to monitor changes mRNA expression in lungs. There was a clear association with disease susceptibility and development of cytokine mRNA expression. In addition to proinflammatory cytokines, mRNA expression of an anti-inflammatory cytokine, interleukin-10, increased with disease severity, suggesting an attempt to moderate the severity of the inflammatory response. Furthermore, it is clear that an array of chemokines produced in susceptible mice could contribute to the recruitment and maintenance of inflammatory cells at the site of disease. In support of this, there was an increase in macrophage inflammatory protein 1beta (MIP-1beta; CCL4) and monocyte chemoattractant protein 2 (MCP-2; CCL8) mRNA levels from mycoplasma-infected mice and a corresponding accumulation of CD4+ Th cells expressing the MIP-1beta/MCP-2 receptor, CCR5, in the lungs of mice. Furthermore, MIP-1beta- and MCP-2-producing cells and CD4+ T cells were found to be in close association in pulmonary lesions. Thus, there was a significant cytokine response associated with disease pathogenesis, and these studies provide important leads and insights into ongoing cytokine- and chemokine-mediated processes in this persistent inflammatory disease.

Respiratory tract infection with Mycoplasma pneumoniae in interleukin-12 knockout mice results in improved bacterial clearance and reduced pulmonary inflammation

Mycoplasma pneumoniae is a leading cause of pneumonia and is associated with asthma. Evidence links M. pneumoniae respiratory disease severity with interleukin-12 (IL-12) concentration in respiratory secretions. We evaluated the microbiologic, inflammatory, and pulmonary function indices of M. pneumoniae pneumonia in IL-12 (p35) knockout (KO) mice and wild-type (WT) mice to determine the role of IL-12 in M. pneumoniae respiratory disease. Eight-week-old wild-type BALB/c mice and 8-week-old IL-12 (p35) KO BALB/c mice were inoculated once intranasally with 10(7) CFU of M. pneumoniae. Mice were evaluated at days 2, 4, and 7 after inoculation. Outcome variables included quantitative bronchoalveolar lavage (BAL) M. pneumoniae culture, lung histopathologic scores (HPS), BAL cytokine concentrations determined by enzyme-linked immunosorbent assay (tumor necrosis factor alpha [TNF-alpha], gamma interferon [IFN-gamma], IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-10, and granulocyte-macrophage colony-stimulating factor) and plethysmography, before and after methacholine, to assess airway obstruction (AO) and airway hyperreactivity (AHR). IL-12 (p35) KO mice infected with M. pneumoniae were found to have significantly lower BAL M. pneumoniae concentrations compared with M. pneumoniae-infected WT mice. Lung HPS and the parenchymal pneumonia subscores (neutrophilic alveolar infiltrate), as well as AO, were significantly lower in infected KO mice. No difference was found for AHR. Infected KO mice had significantly lower BAL concentrations of IFN-gamma than WT mice; a trend toward lower BAL concentrations was observed for IL-10 (P = 0.065) and TNF-alpha (P = 0.078). No differences were found for IL-1beta, IL-2, IL-4, IL-5, or IL-6. The lack of IL-12 in experimental M. pneumoniae pneumonia was associated with less severe pulmonary disease and more rapid microbiologic and histologic resolution.

Immunogenetics of severe respiratory infections: models for the development of new therapeutic strategies

Innate and adaptive immunity plays a critical role in the defence of the lung and other mucosal surfaces exposed to micro-organisms. Anti-microbial peptides and proteins, cytokines and chemokines are important immune weapons as they build up the protective front for the respiratory tract. The notion that susceptibility to infectious diseases may be inherited is widely accepted and, as it is the failure to activate adaptive immunity that may allow infection to become established and progress toward invasion and dissemination, the recognition of specific gene defects affecting the ability of the immune system to overcome invading pathogens may shed light upon those mechanisms of immune regulation that are playing the most critical roles. The aim of the present review is to discuss some of the advances in infection immunogenetics that may lead to identify new strategies in the development of new anti-infectious and anti-inflammatory drugs.

T-bet deficiency facilitates airway colonization by Mycoplasma pulmonis in a murine model of asthma

Epidemiological and clinical evidence suggest a correlation between asthma and infection with atypical bacterial respiratory pathogens. However, the cellular and molecular underpinnings of this correlation remain unclear. Using the T-bet-deficient (T-bet(-/-)) murine model of asthma and the natural murine pathogen Mycoplasma pulmonis, we provide a mechanistic explanation for this correlation. In this study, we demonstrate the capacity of asthmatic airways to facilitate colonization by M. pulmonis and the capacity of M. pulmonis to exacerbate symptoms associated with acute and chronic asthma. This mutual synergism results from an inability of T-bet(-/-) mice to mount an effective immune defense against respiratory infection through release of IFN-gamma and the ability of M. pulmonis to trigger the production of Th2-type cytokines (e.g., IL-4 and IL-5), and Abs (e.g., IgG1, IgE, and IgA), eosinophilia, airway remodeling, and hyperresponsiveness; all pathophysiological hallmarks of asthma. The capacity of respiratory pathogens such as Mycoplasma spp. to dramatically augment the pathological changes associated with asthma likely explains their association with acute asthmatic episodes in juvenile patients and with adult chronic asthmatics, >50% of whom are found to be PCR positive for M. pneumoniae. In conclusion, our study demonstrates that in mice genetically predisposed to asthma, M. pulmonis infection elicits an inflammatory milieu in the lungs that skews the immune response toward the Th2-type, thus exacerbating the pathophysiological changes associated with asthma. For its part, airways exhibiting an asthmatic phenotype provide a fertile environment that promotes colonization by Mycoplasma spp. and one which is ill-equipped to kill and clear respiratory pathogens.