Molecular Immunology

Both knock-down and overexpression of Rap2a small GTPase in macrophages result in impairment of NF-κB activity and inflammatory gene expression Publication date: May 2019 Source: Molecular Immunology, Volume 109 Author(s): Brener C. Carvalho, Leonardo C. Oliveira, Carolina D. Rocha, Heliana B. Fernandes, Isadora M. Oliveira, Felipe B. Leão, Thalita M. Valverde, Igor M.G. Rego, Sankar Ghosh, Aristóbolo M. Silva Abstract Small Ras GTPases are key molecules that regulate a variety of cellular responses in different cell types. Rap1 plays important functions in the regulation of macrophage biology during inflammation triggered by toll-like receptors (TLRs). However, despite sharing a relatively high degree of similarity with Rap1, no studies concerning Rap2 in macrophages and innate immunity have been reported yet. In this work, we show that either way alterations in the levels of Rap2a hampers proper macrophages response to TLR stimulation. Rap2a is activated by LPS in macrophages, and although putative activator TLR-inducible Ras guanine exchange factor RasGEF1b was sufficient to induce, it was not fully required for Rap2a activation. Silencing of Rap2a impaired LPS-induced production of IL-6 cytokine and KC/Cxcl1 chemokine, and also NF-κB activity as measured by reporter gene studies. Surprisingly, overexpression of Rap2a did also lead to marked inhibition of NF-κB activation induced by LPS, Pam3CSK4 and downstream TLR signaling molecules. We also found that Rap2a can inhibit the LPS-induced phosphorylation of the NF-κB subunit p65 at serine 536. Collectively, our data suggest that expression levels of Rap2a in macrophages might be tightly regulated to avoid unbalanced immune response. Our results implicate Rap2a in TLR-mediated responses by contributing to balanced NF-κB activity status in macrophages.

PD-1-expressing B cells suppress CD4+ and CD8+ T cells via PD-1/PD-L1-dependent pathway Publication date: May 2019 Source: Molecular Immunology, Volume 109 Author(s): Xufu Wang, Guoqiang Wang, Zenghua Wang, Bin Liu, Na Han, Jiao Li, Chenghui Lu, Xinfeng Liu, Qin Zhang, Qingbo Yang, Guoming Wang Abstract B cell-mediated regulatory function is instrumental to the maintenance of tolerance, but may also contribute to immune dysfunction during infectious diseases and malignancies. In this study, we investigated a subset of B cells characterized by PD-1 expression. Data showed that these PD-1+ B cells were rare in peripheral blood, but were significantly upregulated in differentiated thyroid tumors. The PD-1+ B cells also expressed significantly higher level of PD-L1. Continuous, but not short-term, anti-Ig/CD40 L stimulation could upregulate the expression of PD-1 and PD-L1 in B cells. In in vitro experiments, PD-1+ B cells significantly suppressed the proliferation of CD4+ and CD8+ T cells and reduced their viability upon CD3/CD28 stimulation, thus suggesting that these PD-1+ B cells presented regulatory functions. However, unlike other IL-10-secreting Breg cell subsets, the PD-1+B cells did not express high level of IL-10. Instead, it seemed that PD-L1 was instrumental to the suppressive effects mediated by PD-1+ B cells, since the blockade of PD-L1 significantly increased the proliferation and viability of T cells in the coculture. Interestingly, compared to untreated patients with differentiated thyroid tumor, the thyroidectomy and 131I-treated patients presented significantly lower frequencies of PD-1+ B cells. Together, our investigation demonstrated that the PD-1+ B cells possessed regulatory capacity toward T cell responses, and although rare in peripheral blood, they were significantly enriched in thyroid tumors.

Dust mite-derived Der f 3 activates a pro-inflammatory program in airway epithelial cells via PAR-1 and PAR-2 Publication date: May 2019 Source: Molecular Immunology, Volume 109 Author(s): Bizhou Li, Zehong Zou, Fanmei Meng, Eyal Raz, Yuye Huang, Ailin Tao, Yuncan Ai Abstract Protease activity of allergens has been suggested to be involved in the pathogenesis of allergic diseases. The major allergen Der f 3 from Dermatophagoides farinae harbors serine protease activity, but its immunopathogenesis remains unclear. This study aims to explore the effect of Der f 3 on the airway epithelial barrier and on the molecular pathways by which Der f 3 induces inflammation. RNA-seq was performed to identify differentially expressed genes in bronchial airway epithelial cells (AEC) between native Der f 3 and heat-inactivated (H) Der f 3, coupled with real-time PCR (RT-PCR) and ELISA for validation. Unlike other protease allergens such as that induce Th2-promoting alarmins (IL-25, IL-33, TSLP) in AECs, Der f 3 induced pro-inflammatory cytokines and chemokines including IL-6, IL-8 and GM-CSF, which are known to promote Th17 response. These pro-inflammatory mediators were induced by Der f 3 via the MAPK and NF-κB pathways as well as the store-operated calcium signaling. Gene silencing with small interfering RNA in A549 and BEAS-2B cells indicated that activation of AECs by Der f 3 was mainly dependent on protease-activated receptor 2 (PAR-2), while PAR-1 was also required for the full activation of AECs. Double knock-down of PAR-1 and PAR-2 largely impaired Der f 3-inducecd IL-8 production and subsequent signaling pathways. Our data suggest that Der f 3 induces pro-inflammatory mediators in human epithelial cell lines via the PARs-MAPK-NF-κB axis. Our results provide a molecular mechanism by which Der f 3 may trigger the Th17-skewed allergic response toward house dust mites.

Nanobody against the E7 oncoprotein of human papillomavirus 16 Publication date: May 2019 Source: Molecular Immunology, Volume 109 Author(s): Shufeng Li, Wei Zhang, Kunpeng Jiang, Haitao Shan, Minke Shi, Baojun Chen, Zichun Hua Abstract The persistent infection of high-risk human papillomavirus (HPV) is one of the most common causes of cervical cancer. It is well documented that expression of two oncogenes (E6/E7) plays a key role in tumor progression. HPV16E7 -targeting via nanobody (Nb) therefore could be beneficial for HPV16-associated cancer diagnosis and therapy. In this work, phage-display approach was employed to select the high affinity HPV16E7-specific Nb. Firstly; a high-quality immune library was constructed. After three round of biopanning, high-affinity HPV16 E7-specific nanobodies were retrieved. By phage ELISA and sequencing, four different sequences of anti- HPV16E7 nanobodies were selected. Then recombinant nanobody Nb2 was cloned and expressed in E. coli, and the specificity and thermal stability of purified Nb2 was evaluated. To examine the potential of Nb2 as an inhibitor of E7 function, Nb2 was expressed within HPV16 positive cells. Proliferation assay showed that the intracellular expressed Nb2 as an intrabody can decrease the growth of HPV16-positive cells. The results indicate that Nb2 as an intracellular antibody directed towards HPV oncoprotein E7 has great promise in applications for the therapy of HPV16-associated disease.

Fli-1 transcription factor regulates the expression of caspase-1 in lung pericytes Publication date: April 2019 Source: Molecular Immunology, Volume 108 Author(s): Pengfei Li, Andrew J. Goodwin, James A. Cook, Perry V. Halushka, Xian K. Zhang, Hongkuan Fan Abstract Our previous data demonstrated that Friend leukemia virus integration 1 (Fli-1), an ETS transcription factor, governs pericyte loss and vascular dysfunction in cecal ligation and puncture-induced murine sepsis by regulating essential pyroptosis markers including caspase-1. However, whether Fli-1 regulates caspase-1 expression levels in vitro and how Fli-1 regulates caspase-1 remain unknown. Our present work further demonstrated that overexpressed Fli-1 significantly increased caspase-1 and IL-18 expression levels in cultured mouse lung pericytes. Bacterial outer membrane vesicles (OMVs) have been found to induce cell pyroptosis through transferring LPS intracellularly. Using OMVs to induce an in vitro model of pyroptosis, we observed that OMVs significantly increased protein levels of Fli-1 in mouse lung pericytes. Furthermore, knockdown of Fli-1 by siRNA blocked OMVs-induced caspase-1, caspase-11 and IL-18 expression levels. As caspase-1 was predicted as a potential target of Fli-1, we cloned murine caspase-1 promoter into a luciferase construct. Our data demonstrate for the first time that Fli-1 regulates caspase-1 expression by directly binding to its promoter regions measured by chromatin immunoprecipitation (ChIP) assay and luciferase reporter system. In summary, our findings demonstrated a novel role and mechanism of Fli-1 in regulating caspase-1 expression in lung pericytes.

The ficolin response to LPS challenge in mice Publication date: April 2019 Source: Molecular Immunology, Volume 108 Author(s): Ida Jarlhelt, Ninette Genster, Nikolaj Kirketerp-Møller, Mikkel-Ole Skjoedt, Peter Garred Abstract The ficolins belong to an important family of pattern recognition molecules, which contributes to complement activation via the lectin pathway. How the ficolins respond to inflammatory stimuli remains only partly understood. In the present study, we investigated the ficolin A and ficolin B expression and protein distribution patterns in a mouse model of LPS-induced inflammation. The time- and tissue-specific expression of ficolin A and B was determined by real time PCR. Furthermore, ficolin protein levels in serum and bone marrow extracts from LPS challenged mice were determined by novel in-house developed sandwich ELISAs. Ficolin A was mainly expressed in liver and spleen. However, our data also suggested that ficolin A is expressed in bone marrow, which is the main site of ficolin B expression. The level of ficolin A and B expression was increased after stimulation with LPS in the investigated tissues. This was followed by a downregulation of expression, causing mRNA levels to return to baseline 24 h post LPS challenge. Protein levels appeared to follow the same pattern as the expression profiles, with an exception of ficolin B levels in serum, which kept increasing for 24 h. Ficolin A was likewise significantly increased in bronchoalveolar lavage fluid from mice infected with the fungi A. fumigatus, pointing towards a similar effect of the ficolins in non-sterile mouse models of inflammation. The results demonstrate that LPS-induced inflammation can induce a significant ficolin response, suggesting that the murine ficolins are acute phase reactants with increase in both mRNA expression and protein levels during systemic inflammation.

Modified DCs and MSCs with HPV E7 antigen and small Hsps: Which one is the most potent strategy for eradication of tumors? Publication date: April 2019 Source: Molecular Immunology, Volume 108 Author(s): Azam Bolhassani, Sepideh Shahbazi, Elnaz Agi, Nooshin Haghighipour, Amin Hadi, Fatemeh Asgari Abstract Immunotherapy with DCs as antigen-presenting vehicles have already improved patients' outcome against a variety of tumors. Moreover, MSCs were recently used to develop anti-cancer therapeutic or anti-microbial prophylactic vaccines. The current study evaluated immune responses and anti-tumor effects generated by DCs and MSCs derived from mouse bone marrow which were modified with small heat shock proteins 27 and 20 (sHsp27 and sHsp20) and also E7 oncoprotein in tumor mouse model. Two vaccination strategies were utilized including homologous DC or MSC prime/ DC or MSC boost, and heterologous MSC or DC prime/ protein boost vaccinations. Our data revealed that DCs pulsed with E7+Hsp27 and/or E7+Hsp20 in homologous and heterologous prime/ boost vaccinations could stimulate high levels of IgG2a, IgG2b, IFN-γ and IL-10 directed toward Th1 responses. Moreover, these regimens induced an increased level of Granzyme B, and displayed complete protection more than 60 days after treatment. On the other hand, MSCs transfected with E7+Hsp27 DNA in homologous and heterologous prime/ boost vaccinations could significantly enhance the E7-specific T-cell responses and suppress tumor growth in mice. However, MSCs transfected with E7+Hsp20 DNA did not induce a complete protection against TC-1 tumor compared to DCs pulsed with E7+Hsp20 protein complexes. These results indicated that DC- and MSC-based vaccinations with specific modalities will be a useful approach for immunotherapy and protection against HPV-associated cancers.

Modulation of antiviral immunity by the ichnovirus HdIV in Spodoptera frugiperda Publication date: April 2019 Source: Molecular Immunology, Volume 108 Author(s): Vincent Visconti, Magali Eychenne, Isabelle Darboux Abstract Polydnaviruses (PDVs) are obligatory symbionts found in thousands of endoparasitoid species and essential for successful parasitism. The two genera of PDVs, ichnovirus (IV) and bracovirus (BV), use different sets of virulence factors to ensure successful parasitization of the host. Previous studies have shown that PDVs target apoptosis, one of the innate antiviral responses in many host organisms. However, IV and BV have been shown to have opposite effects on this process. BV induces apoptosis in host cells, whereas some IV proteins have been shown to have anti-apoptotic activity. The different biological contexts in which the assays were performed may account for this difference. In this study, we evaluated the interplay between apoptosis and the ichnovirus HdIV from the parasitoid Hyposoter didymator, in the HdIV-infected hemocytes and fat bodies of S. frugiperda larvae, and in the Sf9 insect cell line challenged with HdIV. We found that HdIV induced cell death in hemocytes and fat bodies, whereas anti-apoptotic activity was observed in HdIV-infected Sf9 cells, with and without stimulation with viral PAMPs or chemical inducers. We also used an RT-qPCR approach to determine the expression profiles of a set of genes known to encode key components of the other main antiviral immune pathways described in insects. The analysis of immune gene transcription highlighted differences in antiviral responses to HdIV as a function of host cell type. However, all these antiviral pathways appeared to be neutralized by low levels of expression for the genes encoding the key components of these pathways, in all biological contexts. Finally, we investigated the effect of HdIV on the general antiviral defenses of the lepidopteran larvae in more detail, by studying the survival of S. frugiperda co-infected with HdIV and the entomopathogenic densovirus JcDV. Coinfected S. frugiperda larvae have increased resistance to JcDV at an early phase of infection, whereas HdIV effects enhance the virulence of the virus at later stages of infection. Overall, these results reveal complex interactions between HdIV and its cellular environment.

Phenylethanoid glycosides of Phlomis younghusbandii Mukerjee ameliorate acute hypobaric hypoxia-induced brain impairment in rats Publication date: April 2019 Source: Molecular Immunology, Volume 108 Author(s): Fei Luan, Maoxing Li, Keqing Han, Qiang Ma, Jian Wang, Yan Qiu, Linhong Yu, Xirui He, Daoheng Liu, Haizhen Lv Abstract High altitude cerebral edema (HACE), whose development process is associated with oxidative stress and inflammatory response, is a life-threatening condition caused by rapid ascent speed to high altitudes. Phenylethanoid glycosides (PhGCs) are primary active constituents isolated from Phlomis younghusbandii Mukerjee that reportedly exhibit potent anti-oxidant and anti-inflammatory activities. The present study aims to investigate the protective effect of phenylethanoid glycosides (PhGCs) from P. younghusbandii in acute hypobaric hypoxia (AHH) – stimulated HACE rats and its underlying mechanisms. The expression of pro-inflammatory cytokine levels (IL-1β, TNF-α, and IL-6) was detected by RT-PCR and ELISA at mRNA and protein levels in brain tissues. Western blotting was carried out to measure the major protein levels (IL-1β, TNF-α, and NF-κB) in brain tissues. The oxidative stress biomarkers (MDA, SOD, and GSH) were evaluated using kits. Results demonstrate that PhGCs significantly improved pathological changes in brain tissues, reduced the brain's water content, and attenuated the production and mRNA expression of pro-inflammatory cytokines. Furthermore, the increased oxidative stress and the decrease in anti-oxidant stress system under the AHH condition were also abrogated reversely through PhGCs treatment by elevating the levels of SOD and GSH and suppressing the accumulation of MDA. Simultaneously, there was also a significant reduction in NF-κB, IL-1β, and TNF-α protein expression levels in brain tissues, suggesting that blocking the NF-κB signaling pathway activation prevented the production of pro-inflammatory cytokines. Taken together, these findings indicate that PhGCs may afford a protectively intervene in HACE through the suppression of oxidative stress and inflammatory response via the inhibition of the NF-κB signaling pathway, indicating that PhGCs are promising agents for the treatment of acute HACE.

Tumor suppressor p53 inhibits porcine epidemic diarrhea virus infection via interferon-mediated antiviral immunity Publication date: April 2019 Source: Molecular Immunology, Volume 108 Author(s): Zhichao Hao, Fang Fu, Liyan Cao, Longjun Guo, Jianbo Liu, Mei Xue, Li Feng Abstract p53 is a tumor suppressor gene that can be activated in many contexts, such as DNA damage or stressful conditions. p53 has also been shown to be important for responses to certain viral infections. Porcine epidemic diarrhea virus (PEDV) is a major enteric pathogen of the coronavirus family that causes extensive mortality among piglets. The involvement of p53 during PEDV infection has not previously been investigated. In this study, we detected p53 upregulation in response to PEDV infection. Treatment with a p53 specific activator or p53 overexpression markedly decreased viral replication, and we showed that there was more viral progeny produced in p53 knock-out cells than in p53 wild-type cells. Finally, we demonstrated that inhibition of viral infection by p53 was mediated via p53-dependent IFN signaling, leading to IFN-stimulated response element (ISRE) activation, as well as the upregulation of IFN-stimulated genes (ISGs) and IFN-β released from infected cells. These findings demonstrate that p53 suppresses PEDV infection, offering a novel therapeutic strategy for combatting this deadly disease in piglets.