Specific and nonspecific antibody responses in different segments of the respiratory tract in rats infected with Mycoplasma pulmonis

The Use of Bacteriophages and Immunological Monitoring for the Treatment of a Case of Chronic Septicemic Cutaneous Ulcerative Disease in a Loggerhead Sea Turtle Caretta caretta

In this case study, phage therapy was applied to treat a multidrug-resistant case of septicemic cutaneous ulcerative disease (SCUD) caused by Citrobacter freundii in a loggerhead sea turtle Caretta caretta. Phages were applied topically, intravenously, into the carapace, and into the exhibit water using various phage cocktails specific to the causative agent over an 8-month period. This was performed in conjunction with antimicrobial therapy. The animal was monitored through weekly cultures, photographs, and complete blood cell counts, as well as immune assays (phagocytosis, plasma lysozyme and superoxide dismutase activity, and plasma electrophoresis profiles). The animal, in comparison to an untreated, unaffected control, had elevated antibody titers to the administered phages, which persisted for at least 35 weeks. Although cultures were clear of C. freundii after phage treatment, the infection did return over time and immune assays confirmed deficiencies when compared to a healthy loggerhead sea turtle. Immune parameters with statistically significant changes over the study period included the following: decreased phagocytosis, increased alpha- and gamma-globulin protein components, and an increased albumin : globulin ratio. When C. freundii appeared again, the multidrug-resistant status had reverted back to normal susceptibility patterns. Although not completely known whether it was another subspecies of bacteria, the therapy did resolve the multidrug-resistant challenge. Phage therapy in combination with antimicrobial agents may be an effective treatment for sea turtles with normally functioning immune systems or less-severe infections. Additional research is needed to better understand and quantify sea turtle immunology.

The Role of B Cells in Carriage and Clearance of Mycoplasma pneumoniae From the Respiratory Tract of Mice

Background

Carriage of Mycoplasma pneumoniae (Mp) in the nasopharynx is considered a prerequisite for pulmonary infection. It is interesting to note that Mp carriage is also detected after infection. Although B cells are known to be involved in pulmonary Mp clearance, their role in Mp carriage is unknown.

Methods

In this study, we show in a mouse model that Mp persists in the nose after pulmonary infection, similar to humans.

Results

Infection of mice enhanced Mp-specific immunoglobulin (Ig) M and IgG levels in serum and bronchoalveolar lavage fluid. However, nasal washes only contained elevated Mp-specific IgA. These differences in Ig compartmentalization correlated with differences in Mp-specific B cell responses between nose- and lung-draining lymphoid tissues. Moreover, transferred Mp-specific serum Igs had no effect on nasal carriage in B cell-deficient μMT mice, whereas this enabled μMT mice to clear pulmonary Mp infection.

Conclusions

We report the first evidence that humoral immunity is limited in clearing Mp from the upper respiratory tract.

THE MULTIFACETED ROLE OF T CELL-MEDIATED IMMUNITY IN PATHOGENESIS AND RESISTANCE TO MYCOPLASMA RESPIRATORY DISEASE

Mycoplasma respiratory diseases have a significant impact on the economy, health and wildlife. The hallmark of these diseases is the persistence of the mycoplasma infections and chronic inflammatory responses associated with the airways. There is still much that needs to be understood about the immune mechanisms involved in mycoplasma disease and resistance from infection. It is clear that immune responses can contribute to the generation of inflammatory lesions in mycoplasma respiratory disease, as well as provide protection from infection and extrapulmonary dissemination of the organisms. The evolution of this lung disease is under the control innate immune mechanisms and the contrasting effects of different T cell populations. The mechanisms of immunity involved in mycoplasma diseases are multifaceted, and a fascinating story of its complexity is being uncovered. Research in mycoplasma respiratory diseases have underscored the idea that immunity along the respiratory tract against infectious agents is a dynamic process and involves a network of cellular and cytokine signals that determine the type of responses generated, and ultimately, the outcome of infection. The aim of this article is to present on overview of our work on mycoplasma disease and immunity, focusing on the interactions and regulation of T cell responses that influence disease pathogenesis. We will first provide an overview of immune mechanisms involved in controlling infection and participate in the generation of T cell responses, and the role of T cell populations in generating protection and contributing to lesion development will be discussed.

Lung and splenic B cells facilitate diverse effects on in vitro measures of antitumor immune responses

In vitro measures of immune responsiveness toward tumors provide relevant information regarding the prevention and metastatic potential of cancer. In addition, the compartmentalization of immune responses is likely to be an important factor in dictating host antitumor immune responses. We have previously demonstrated that injection of antibody against B cells diminished pulmonary antitumor defenses. In the current study, we determined the effect of B cells on antitumor cellular responses against a lung metastatic tumor, MADB106. Lung B cells displayed sustained surface expression of CD80 and CD86, as compared to spleen B cells, in the presence of MADB106 tumor. Removal of B cells from lung lymphocyte cultures resulted in diminished IFN-gamma secretion and tumor lysis, whereas removal of B cells from spleen lymphocytes exposed to tumor resulted in elevated IFN-gamma and increased tumor lysis. Furthermore, a correlative increase in CD80 and CD86 co-stimulatory molecule expression by lung B cells was observed in mice subjected to MADB106 tumor. These findings provide additional evidence of the importance of pulmonary B cell responses in tumor defenses.

The complex mechanism of antibody-mediated clearance of Bordetella from the lungs requires TLR4

Although the antibacterial effects of Abs are well studied in in vitro systems, the in vivo effects of Abs cannot always be accurately predicted. Complicated cross-talk between different effector functions of Abs and various arms of the immune system can affect their activities in vivo. Using the mouse respiratory pathogen Bordetella bronchiseptica, we examined the mechanisms of Ab-mediated clearance of bacteria from the respiratory tract. Interestingly, although TLR4 was not necessary for protective immunity following infection, it was required for rapid bacterial clearance in mice that were vaccinated or adoptively transferred Abs. TLR4 was important for the rapid recruitment of neutrophils that are necessary for Ab-mediated bacterial clearance via a mechanism that requires both FcgammaR and CR3. These data are consistent with a model in which TLR4-mediated inflammatory responses aid in the recruitment of neutrophils, which phagocytose Ab- and complement-opsonized bacteria via FcgammaRs and CR3. Although pattern recognition receptors are known to be involved in innate immunity and the generation of adaptive immunity, their contributions to specific adaptive immune functions should be considered in ongoing efforts to improve vaccine-induced protective immunity.

The upper and lower respiratory tracts differ in their requirement of IFN-gamma and IL-4 in controlling respiratory mycoplasma infection and disease

The purpose of this study is to evaluate the significance of IFN-gamma and IL-4 production in controlling mycoplasma infection and the pathogenesis of disease in the upper and lower respiratory tract. By using IFN-gamma knockout and IL-4 knockout BALB/c mice, we were able to study the contribution of these cytokines in the development of pathogenesis and/or protection in response to mycoplasma respiratory infection, in both the upper and lower respiratory tracts. The loss of either IFN-gamma or IL-4 does not affect disease pathogenesis or mycoplasma organism numbers in the upper respiratory tract. However, in the absence of IL-4, the nasal passages developed a compensatory immune response, characterized by higher numbers of macrophages and CD8(+) T cells, which may be masking detrimental effects due to IL-4 deficiency. This is in contrast to the lower respiratory tract, where the loss of IFN-gamma, but not IL-4, leads to higher mycoplasma numbers and increased disease severity. The loss of IFN-gamma impacted the innate immune system's ability to effectively clear mycoplasma, as the number of organisms was higher by day 3 postinfection. This higher organism burden most likely impacted disease pathogenesis; however, the development of Th2 cell-mediated adaptive immune response most likely contributed to lesion severity at later time points during infection. Our studies demonstrate that the upper and lower respiratory tracts are separate and distinct in their cytokine requirements for generating immunity against mycoplasma infection.

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

Mycoplasma infection is a leading cause of pneumonia worldwide and can lead to other respiratory complications. A component of mycoplasma respiratory diseases is immunopathologic, suggesting that lymphocyte activation is a key event in the progression of these chronic inflammatory diseases. The present study delineates the changes in T cell populations and their activation after mycoplasma infection and determines their association with the pathogenesis of murine Mycoplasma respiratory disease, due to Mycoplasma pulmonis infection. Increases in T cell population numbers in lungs and lower respiratory lymph nodes were associated with the development of mycoplasma respiratory disease. Although both pulmonary Th and CD8(+) T cells increased after mycoplasma infection, there was a preferential expansion of Th cells. Mycoplasma-specific Th2 responses were dominant in lower respiratory lymph nodes, while Th1 responses predominated in spleen. However, both mycoplasma-specific Th1 and Th2 cytokine (IL-4 and IFN-gamma) responses were present in the lungs, with Th1 cell activation as a major component of the pulmonary Th cell response. Although a smaller component of the T cell response, mycoplasma-specific CD8(+) T cells were also a significant component of pulmonary lymphoid responses. In vivo depletion of CD8(+) T cells resulted in dramatically more severe pulmonary disease, while depletion of CD4(+) T cells reduced its severity, but there was no change in mycoplasma numbers in lungs after cell depletion. Thus, mycoplasma-specific Th1 and CD8(+) T cell activation in the lung plays a critical regulatory role in development of immunopathologic reactions in Mycoplasma respiratory disease.

The pulmonary environment promotes Th2 cell responses after nasal-pulmonary immunization with antigen alone, but Th1 responses are induced during instances of intense immune stimulation

The purpose of this study was to determine the nature of the CD4(+) Th cell responses induced after nasal-pulmonary immunization, especially those coinciding with previously described pulmonary inflammation associated with the use of the mucosal adjuvant, cholera toxin (CT). The major T cell population in the lungs of naive mice was CD4(+), and these cells were shown to be predominantly of Th2 type as in vitro polyclonal stimulation resulted in IL-4, but not IFN-gamma, production. After nasal immunization with influenza Ag alone, Th2 cytokine mRNA (IL-4 and IL-5) levels were increased, whereas there was no change in Th1 cytokine (IL-2 and IFN-gamma) mRNA expression. The use of the mucosal adjuvant, CT, markedly enhanced pulmonary Th2-type responses; however, there was also a Th1 component to the T cell response. Using in vitro Ag stimulation of pulmonary lymphocytes, influenza virus-specific cytokine production correlated with the mRNA cytokine results. Furthermore, there was a large increase in CD4(+) Th cell numbers in lungs after nasal immunization using CT, correlating with the pulmonary inflammatory infiltrate previously described. Coincidentally, both macrophage-inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta mRNA expression increased in the lungs after immunization with Ag plus CT, while only MIP-1beta expression increased when mice were given influenza Ag alone. Our study suggests a mechanism to foster Th1 cell recruitment into the lung, which may impact on pulmonary immune responses. Thus, while Th2 cell responses may be prevalent in modulating mucosal immunity in the lungs, Th1 cell responses contribute to pulmonary defenses during instances of intense immune stimulation.

Immunoglobulin A (IgA) responses and IgE-associated inflammation along the respiratory tract after mucosal but not systemic immunization

The purpose of the present study was to determine the extent of immunologic responses, particularly immunopathologic responses, within the upper and lower respiratory tracts after intranasal immunization using the mucosal adjuvant cholera toxin (CT). BALB/c mice were nasally immunized with influenza virus vaccine combined with CT. The inclusion of the mucosal adjuvant CT clearly enhanced generation of antibody responses in both the nasal passages and lungs. After nasal immunization, antigen-specific immunoglobulin A (IgA) antibody-forming cells dominated antibody responses throughout the respiratory tract. However, IgG responses were significant in lungs but not in nasal passages. Furthermore, parenteral immunization did not enhance humoral immunity in the upper respiratory tract even after a nasal challenge, whereas extrapulmonary lymphoid responses enhanced responses in the lung. After nasal immunization, inflammatory reactions, characterized by mononuclear cell infiltration, developed within the lungs of mice but not in nasal passages. Lowering dosages of CT reduced, but did not eliminate, these adverse reactions without compromising adjuvancy. Serum IgE responses were also enhanced in a dose-dependent manner by inclusion of CT. In summary, there are differences in the generation of humoral immunity between the upper respiratory tract and the lung. As the upper respiratory tract is in a separate compartment of the immune system from that stimulated by parenteral immunization, nasal immunization is an optimal approach to generate immunity throughout the respiratory tract. Despite the promise of nasal immunization, there is also the potential to develop adverse immunopathologic reactions characterized by pulmonary airway inflammation and IgE production.

Gene rearrangements in the vsa locus of Mycoplasma pulmonis

The vsa genes of Mycoplasma pulmonis encode the V-1 lipoproteins. Most V-1 proteins contain repetitive domains and are thought to be involved in mycoplasma-host cell interactions. Previously, we have reported the isolation and characterization of six vsa genes comprising a 10-kb region of the genome of M. pulmonis strain KD735-15. In the current study, vsa-specific probes were used to clone several fragments from a genomic library of KD735-15 DNA and assemble a single 20-kb contig containing 11 vsa genes. The middle region of the vsa locus contains a large open reading frame (ORF) that is not a vsa gene and has undergone an internal deletion in some strains. The ORF is predicted to encode a membrane protein that may have a role in disease pathogenesis. To examine vsa genes in a strain of M. pulmonis that is unrelated to KD735-15, strain CT was studied. Through Southern hybridization and genomic cloning analyses, CT was found to possess homologs of the KD735-15 vsaA, -C, -E, and -F genes and two unique genes (vsaG and vsaH) that were not found in KD735-15. High-frequency, site-specific DNA inversions serve to regulate the phase-variable production of individual V-1 proteins. As a result of the sequence analysis of vsa recombination products, a model in which DNA inversion arises from strand exchange involving at least six nucleotides of the vrs box is proposed.

Pathogenicity of cilia-associated respiratory (CAR) bacillus isolates for F344, LEW, and SD rats

We conducted experiments to test whether rats of F344, LEW, and SD strains differ in susceptibility to mycoplasma-free isolates of cilia-associated respiratory (CAR) bacillus, whether Mycoplasma pulmonis can affect expression of CAR bacillus disease, and whether isolates of CAR bacillus differ in virulence for rats. In the first experiment, 24 rats of each strain were inoculated intranasally with 10(7) bacilli of CAR bacillus X1428D/AS, and 24 rats of each strain were inoculated with sterile medium (controls). Eight weeks later, eight inoculated rats and eight control rats of each strain were euthanatized, eight inoculated and eight control rats were given 10(6.5) colony-forming units of M. pulmonis X1428D, and eight inoculated rats and eight control rats were sham inoculated. Four rats of each group were euthanatized 4 or 8 weeks after the second inoculation. Severity of lesions in nasal passages, middle ear, trachea, and lungs was assessed by scoring. Rats of all three strains given CAR bacillus had typical lesions of similar severity; M. pulmonis X1428D was avirulent and did not exacerbate CAR bacillus disease. In the second experiment, groups of eight rats of F344 and SD strains were given 10(5) or 10(7) CAR bacillus X1328E, X1428D/AS, or X2450D and euthanatized 8 or 16 weeks later. Isolates X1428D/AS and X2450D caused similar lesions in rats of both strains and at both doses, but CAR bacillus X1328E was avirulent. Rats of the tested strains are similarly susceptible to CAR bacillus disease, but CAR bacillus isolates differ in virulence.

Restricted B-cell responses to microbial challenge of the respiratory tract

The local B-cell response in the respiratory tract to infectious challenge has been analyzed in pigs and calves using two techniques: flow cytometry and antibody secreting cell (ASC) probes. Pneumonia in pigs caused by experimental infection with Mycoplasma hyopneumoniae resulted in a 25-fold increase in the B-cell population in BAL and lung parenchyma 28 days post infection. ASC probes revealed that the B-cell response of immune pigs to a large challenge infection was localized to lung parenchyma and tracheobronchal lymph nodes. Naive calves infected with Pasteurella multocida had a 5-fold increase in the B-cell blast population in lung parenchyma and BAL, and a greater than 60-fold increase in the draining lymph node at 9 days post infection. The ASC probes prepared post challenge from immune calves showed the response to be localized to the draining lymph nodes, with little response in lung parenchyma. A major finding was that ASC probes prepared from lung parenchyma and from pulmonary lymph nodes of both calves and pigs recognized a restricted range of bacterial antigens, particularly compared to the range of antigens recognized by concurrently circulating sera. The use of ASC probes demonstrates that there is a restricted B-cell repertoire in the respiratory tract.

Isotype-specific antibody responses to acute Mycoplasma pneumoniae infection

BACKGROUND

Mycoplasma pneumoniae-induced respiratory infections affect millions of patients and have been implicated in exacerbation of bronchial asthma. IgE may be involved in such exacerbations. While specific IgG and IgM responses to Mycoplasma pneumoniae are well described, the response of other isotypes is less known.

PURPOSE

To determine whether specific IgE and what subclasses of IgG are formed in response to Mycoplasma pneumoniae infection.

METHODS

We studied 20 patients with acute Mycoplasma pneumoniae infection, in whom the diagnosis was confirmed by a 16-fold increase in complement fixation titer between acute and convalescent serum samples. We developed an enzyme-linked immunosorbent assay (ELISA) for the determination of IgG, IgA, and IgM antibodies specific for Mycoplasma pneumoniae protein antigens. We used Western blotting to confirm the results of the ELISA and to detect Mycoplasma-specific IgG subclasses and IgE.

RESULTS

Changes in Mycoplasma pneumoniae-specific IgG, IgA, and IgM were significant. Western blots of Mycoplasma pneumoniae antigens in 13 convalescent sera showed specific IgG in all, IgM in 11, IgA in 6, and IgE in 10. The IgG response consisted mainly of IgG1 and IgG3, and to a lesser degree of IgG2 and IgG4.

CONCLUSIONS

We conclude that Mycoplasma pneumoniae infection is associated with a significant specific IgA and IgE response, in addition to the well-known responses of IgG and IgM. As IgE is involved in allergic reactions, the production of Mycoplasma pneumoniae-specific IgE may have a role in exacerbation of bronchial asthma.

Number of specific antibody-secreting cells in the peripheral blood among children with mycoplasma pneumonia

Mycoplasma pneumoniae-specific antibody-secreting cells (ASCs) in the peripheral blood were enumerated with an enzyme-linked immunospot assay in 12 children with mycoplasma pneumonia. Those cells were detected in the acute phases and declined in number in the convalescent stage. The maximum numbers of M. pneumoniae-specific ASCs ranged from 0 to 478 for immunoglobulin G (IgG), 13 to 1,992 for IgM, and 0 to 53 for IgA per 106 peripheral blood mononuclear cells, whereas the total numbers (i.e., including both specific and nonspecific) of immunoglobulin-secreting cells (IgSCs) were as high as 4,000 for both IgG and IgM and 1,000 for IgA per 106 peripheral blood mononuclear cells. Such a great increase in the numbers of total IgSCs in comparison with that in M. pneumoniae-specific ASCs suggests that the majority of the IgSC increase in the course of mycoplasmal infection was nonspecific to M. pneumoniae. The serum level of M. pneumoniae antibody measured by enzyme-linked immunosorbent assay remained high in the convalescent phase, while the number of specific ASCs decreased. Whereas this observation may be explained by declined degeneration or consumption of the antibody in the convalescent phase, it may be suggestive of the source of M. pneumoniae antibody other than ASCs in the peripheral blood.

Chronic pulmonary infection caused by Mycoplasma pneumoniae leading to pulmonary arteriole remodeling and pulmonary hypertension in rats

The pulmonary arteriole remodeling in Wistar rats with respiratory infection induced by mycoplasma pneumoniae was observed using light microscopy and morphometry. The pulmonary artery pressure (PAP) and index of right ventricular hypertrophy (RVHI) were measured. The intimal and medial hypertrophy can be seen in the pulmonary arterioles, leading to vessel wall thickening and narrowing of the lumina. The total number of the pulmonary arterioles decreased (P < 0.01), and both pulmonary hypertension (Ppa 4.11 +/- 0.19 kPa) and right ventricular hypertrophy (RVHI = 34.96 +/- 3.91%) occurred. In addition, an interstitial pulmonary fibrosis (IPF) was found, in which the content of collagen in the lung tissue changed, i. e., type I collagen increased whereas type III one decreased, and the ratio of type I collagen to type III one increased. It suggested that respiratory infection induced by repeated MP may result in remodeling of pulmonary arterioles and are closely related to pulmonary hypertension.

Intratracheal gene delivery with adenoviral vector induces elevated systemic IgG and mucosal IgA antibodies to adenovirus and beta-galactosidase

One major concern about using adenoviral vectors for repetitive gene delivery to lung epithelial cells is the induction of an immune response to the vector, thus, impeding effective gene transduction. To assess the immune response to the adenoviral vector, repetitive intratracheal (i.t.) gene dosing was performed in CD-1 mice using the replication-deficient adenovirus 5 (Ade5) vector carrying the lacZ gene, and compared to the antibody responses induced by conventional intranasal (i.n.) and intraperitoneal (i.p.) routes of immunization. Kinetics of serum IgG, IgA, and IgM antibody responses to the adenoviral vector and to beta-galactosidase (beta-Gal) were evaluated. Two or three adenoviral vector doses given by i.t., i.n., or i.p. routes resulted in serum IgG titers in excess of 1:200,000, whereas serum IgM and IgA were moderately induced. Analysis of the predominant murine IgG subclass was determined to be IgG2b and IgG2a. To determine the localization of this antibody response, the ELISPOT assay was employed. Lymphocytes were isolated from the lung, the lower respiratory lymph nodes (LRLN), the nasal passages (NP), and the spleen. For i.t- and i.n.-administered mice, the highest IgA spot-forming cell (SFC) response to Ade5 and beta-Gal was located in the NP and in the lung. Both the lung and the LRLN showed elevated numbers of IgG SFCs (4- to 12-fold greater than splenic IgG SFC response) for Ade5 and beta-Gal. This evidence suggests that the lung and associated lymphoid tissues were the source for serum antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)