Profiling of cellular immune responses to Mycoplasma pulmonis infection in C57BL/6 and DBA/2 mice

Impact of intravenous/intranasal polyinosinic-polycytidylic acid administration on the mediastinal fat-associated lymphoid clusters and lung tissue in healthy mice

BACKGROUND

Polyinosinic-polycytidylic acid (pIC) is a synthetic analog of double-stranded RNA. It is used as a synthetic adjuvant to induce an adaptive immune response. However, the effect of pIC on the development of mediastinal fat-associated lymphoid clusters (MFALCs) that regulate intrathoracic hemostasis has remained unidentified.

METHODS

We investigated the impact of intranasal (i.n.) administration (pIC i.n. group) and intravenous (i.v.) administration (pIC i.v. group) of pIC on both MFALCs and lung tissue.

RESULTS

Compared with the control phosphate-buffered saline (PBS) groups, both pIC-administered groups displayed a significant increase in the MFALC size (particularly in the pIC i.n. group), area of MFALC high endothelial venules (HEVs), area of lymphatic vessels (LVs), number of proliferating cells (particularly in the pIC i.v. group), and number of immune cells (B220+ B-lymphocytes, CD3+ T-lymphocytes, Iba1+ macrophages, and Gr-1+ granulocytes) in both MFALCs and lung tissues. In addition, a positive correlation was detected between MFALC size and proliferating cells, immune cell population, LVs, and HEVs within MFALCs in both groups. Except for the proliferating cell and B-lymphocyte populations in the i.n. administered group and granulocyte populations in both i.n. and i.v. administered routes, such correlations were significant.

CONCLUSION

In all, our data indicate that local or systemic administration of pIC induces the development of MFALCs and can be used as an immunostimulant therapeutic strategy.

The adjuvant effect of polymuramil, a NOD1 and NOD2 agonist, differs when immunizing mice of different inbred lines with nonstructural hepatitis C virus (Flaviviridae: Hepacivirus)proteins and is synergistically enhanced in combination with pyrogenalum, a TLR4 agonist

INTRODUCTION

Hepatitis C is a liver disease with high chronicity, the cause of cirrhosis and hepatocarcinoma. The main obstacle to controlling hepatitis C is the lack of vaccines. The aim of the work was to compare the immunogenic activity of nonstructural recombinant proteins NS3, NS4 and NS5B of hepatitis C virus (HCV) as components of a subunit candidate vaccine and to analyze the adjuvant properties of two available commercial drugs, polymuramil and pyrogenalum.

MATERIALS AND METHODS

BALB/c, DBA/2J and C57BL/6 mice were immunized with nonstructural proteins without adjuvants or with polymuramyl (NOD1 and NOD2 agonist) and pyrogenalum (TLR-4 agonist). The activity of antibodies was determined in ELISA, the cellular response - by antigen-specific lymphocyte proliferation and by production of IFN-γ in vitro.

RESULTS

Recombinant proteins showed different immunogenicity. NS4 induced antibodies more efficiently than NS3 and NS5B. Significant differences were found in the immune response of three inbred lines mice: the level of IFN-γ in BALB/c and DBA/2J mice induced by NS5B protein was 30 times higher than in C57Bl/6 mice. In contrast, the induction of antibodies in BALB/c mice was lower than in C57Bl/6 and DBA/2J. Polymuramil did not increase the humoral response to NS5B and enhanced the cellular response only in C57BL/6 mice. The combined use of polymuramil with pyrogenalum significantly increased both the humoral and cellular response of mice to all recombinant HCV proteins.

CONCLUSION

Different immunogenic properties and different functions of recombinant non-structural HCV proteins indicate the feasibility of their combined inclusion in subunit vaccines. It was established for the first time that immunization with HCV proteins with a complex adjuvant (polymuramyl + pyrogenalum) has a synergistic effect, significantly exceeding the effect of each of them separately.

Microenvironmental Changes in Mediastinal Fat-associated Lymphoid Clusters and Lungs in Early and Late Stages of Metastatic Lung Cancer Induction

The prognosis of metastatic lung melanoma (MLM) has been reported to be poor. An increasing number of studies have reported the function of several immune cells in cancer regression. Although the function of mediastinal fat-associated lymphoid clusters (MFALCs) in the progression of inflammatory lung lesions has been previously reported, the association between MLM progression and MFALCs development has remained unexplored. Herein, we compared the microenvironmental changes in the lungs and MFALCs among phosphate-buffered saline (PBS) and cancer groups at early (1 week) and late (2 weeks) stages following the intravenous injection of B16-F10 melanoma cells into C57BL/6 mice. Except for lung CD4+ helper T-cells and Iba1+ macrophage populations of early stage, we observed a significant increase in the proliferating and immune cell (CD20+ B-lymphocytes, CD3+ T-lymphocytes, CD8+ cytotoxic T-cells, CD16+ natural killer (NK) cells populations, area of high endothelial venules, and lung lymphatic vessels in cancer groups at both the stages as compared with the PBS groups. Furthermore, a significant positive correlation was observed between immune cell populations in MFALCs and the lungs (B- and T-lymphocytes, and NK cells in both stages). Collectively, our findings suggest a promising cancer therapeutic strategy via targeting immune cells in MFALCs.

Histopathological Impact of Bleomycin on Lung Injury and Development of Mediastinal Fat-Associated Lymphoid Clusters in the Lymphoproliferative Mouse Model

The purpose of this study is to elucidate the impact of bleomycin on the degree of lung injury and development of mediastinal fat-associated lymphoid clusters (MFALCs) in the lymphoproliferative mouse model (MRL/MpJ-Faslpr/lpr “Lpr”) and its control strain (MRL/MpJ “MpJ”). We analyzed immune cells, the degree of proliferation, lymphatic vessels (LVs), and high endothelial venules (HEVs) in lungs and MFALCs in Lpr and MpJ mice on the 7th and 21st days following intranasal instillation of either bleomycin (BLM group) or PBS (PBS group). The BLM group showed a significant increase in the size of MFALCs, lung injury score, and positive area ratios of LVs, HEVs, and immune cells (especially macrophages, B- and T-lymphocytes) on both days 7 and 21. Interestingly, the lungs in the BLM group on day 21 showed higher collagen deposition and cellular infiltration in MpJ and Lpr, respectively. Moreover, significant positive correlations were observed between the size of MFALCs and lung injury. In conclusion, BLM could exert lung fibrosis or lymphoproliferative infiltration in chronic stages in MpJ and Lpr, respectively, and this varied effect could be due to the variations in the degree of immune cell proliferation and the development of LVs and HEVs among the studied strains.

Beware of Mycoplasma Anti-immunoglobulin Strategies

Mycoplasmas are small, genome-reduced bacteria. They are obligate parasites that can be found in a wide range of host species, including the majority of livestock animals and humans. Colonization of the host can result in a wide spectrum of outcomes. In many cases, these successful parasites are considered commensal, as they are found in the microbiota of asymptomatic carriers. Conversely, mycoplasmas can also be pathogenic, as they are associated with a range of both acute and chronic inflammatory diseases which are problematic in veterinary and human medicine. The chronicity of mycoplasma infections and the ability of these bacteria to infect even recently vaccinated individuals clearly indicate that they are able to successfully evade their host’s humoral immune response. Over the years, multiple strategies of immune evasion have been identified in mycoplasmas, with a number of them aimed at generating important antigenic diversity. More recently, mycoplasma-specific anti-immunoglobulin strategies have also been characterized. Through the expression of the immunoglobulin-binding proteins protein M or mycoplasma immunoglobulin binding (MIB), mycoplasmas have the ability to target the host’s antibodies and to prevent them from interacting with their cognate antigens. In this review, we discuss how these discoveries shed new light on the relationship between mycoplasmas and their host’s immune system. We also propose that these strategies should be taken into consideration for future studies, as they are key to our understanding of mycoplasma diseases' chronic and inflammatory nature and are probably a contributing factor to reduce vaccine efficacy.

Possible Crosstalk of the Immune Cells within the Lung and Mediastinal Fat-Associated Lymphoid Clusters in the Acute Inflammatory Lung Asthma-Like Mouse Model

Recently, we clarified the function of mediastinal fat-associated lymphoid clusters (MFALCs) in the progression of several respiratory diseases. However, their role has not yet been identified in the lung asthmatic condition. Hence, we compared the immune cells in lung and MFALCs of C57BL/6N mice on days 3 and 7 following intranasal instillation of either papain (papain group "PG") or phosphate buffer saline (PBS) (vehicle group "VG"). The PG showed significantly prominent MFALCs, numerous goblet cells (GCs), and higher index ratios of different immune cells (macrophages, natural helper cells (NHC), B- and T-lymphocytes) within the MFALCs and lung than in the VG on both days 3 and 7. Interestingly, a tendency of decreased size of MFALCs and a significant reduction in the number of GCs and immune cells were observed within the MFALCs and lung in the PG on day 7 than on day 3. Furthermore, the quantitative parameters of these immune cells in MFALCs were significantly and positively correlated with the size of MFALCs and immune cells in the lung. This suggested that the possible crosstalk between immune cells within MFALCs and the lung could play a critical role in the progression and recovery of the acute inflammatory lung asthma.

The response of adipose tissues to Mycoplasma pulmonis and Sendai virus infection in C57BL/6 and DBA/2 mice

Adipose tissues in mammals are categorized into white and brown adipose tissues in which cellular morphology, cell functions, and tissue distribution are different. White adipose tissue (WAT) plays a major role in energy reservation, while brown adipose tissue (BAT) mainly relates to the thermoregulation of the body. One interesting function of adipose tissue is the response to the infection, especially the pathogens that cause pneumonia. We have previously reported that DBA/2 (D2) mice are susceptible to pathogens causing pneumonia, Mycoplasma (M.) pulmonis and Sendai virus (SeV), whereas C57BL/6 (B6) mice are resistant to them. Furthermore, morphological alteration of mediastinal fat tissue (MFT) was seen after infection of M. pulmonis in D2 mice but not in B6 mice. In this study, we aimed to exhibit the difference in adipose tissue response in other areas, including interscapular brown adipose tissue (iBAT), inguinal white adipose tissue (ingWAT), and perigonadal WAT (perigoWAT) between resistant strain, B6 and susceptible strain, D2 after challenging them with M. pulmonis and SeV. Compared with B6 mice, D2 mice showed an increase in fat-associated lymphoid cluster in MFT, an increase in BAT in both iBAT and ingWAT after M. pulmonis and SeV infection. The results of this study indicate that pneumonia caused by M. pulmonis and SeV infection induces browning of adipocyte, suggesting that BAT plays a role in pathogen infection and inflammation.

Pathological Alternations of Mediastinal Fat-Associated Lymphoid Cluster and Lung in a Streptozotocin-Induced Diabetic Mouse Model

Diabetes is a devastating global health problem and is considered a predisposing factor for lung injury progression. Furthermore, previous reports of the authors revealed the role of mediastinal fat-associated lymphoid clusters (MFALCs) in advancing respiratory diseases. However, no reports concerning the role of MFALCs on the development of lung injury in diabetes have been published. Therefore, this study aimed to examine the correlations between diabetes and the development of MFALCs and the progression of lung injury in a streptozotocin-induced diabetic mouse model. Furthermore, immunohistochemical analysis for immune cells (CD3+ T-lymphocytes, B220+ B-lymphocytes, Iba1+ macrophages, and Gr1+ granulocytes), vessels markers (CD31+ endothelial cells and LYVE-1+ lymphatic vessels "LVs"), and inflammatory markers (TNF-α and IL-5) was performed. In comparison to the control group, the diabetic group showed lung injury development with a significant increase in MFALC size, immune cells, LVs, and inflammatory marker, and a considerable decrease of CD31+ endothelial cells in both lung and MFALCs was observed. Furthermore, the blood glucose level showed significant positive correlations with MFALCs size, lung injury, immune cells, inflammatory markers, and LYVE-1+ LVs in lungs and MFALCs. Thus, we suggest that the development of MFALCs and LVs could contribute to lung injury progression in diabetic conditions.