ABSTRACT Antigen-specific CD4 + T cells are essential for effective virus-specific host responses, with recent human challenge studies (in volunteers) establishing their importance for influenza A virus (IAV)-specific immunity. However, while many IAV CD4 + T cell epitopes have been identified, few are known to stimulate immunodominant CD4 + T cell responses. Moreover, much remains unclear concerning the major antigen(s) responded to by the human CD4 + T cells and the extents and magnitudes of these responses. We initiated a systematic screen of immunodominant CD4 + T cell responses to IAV in healthy individuals. Using in vitro expanded-multispecificity IAV-specific T cell lines and individual IAV protein antigens produced by recombinant vaccinia viruses, we found that the internal matrix protein 1 (M1) and nucleoprotein (NP) were the immunodominant targets of CD4 + T cell responses. Ten epitopes derived from M1 and NP were definitively characterized. Furthermore, epitope sequence conservation analysis established that immunodominance correlated with an increased frequency of mutations, reflecting the fact that these prominent epitopes are under greater selective pressure. Such evidence that particular CD4 + T cells are important for protection/recovery is of value for the development of novel IAV vaccines and for our understanding of different profiles of susceptibility to these major pathogens. IMPORTANCE Influenza virus causes half a million deaths annually. CD4 + T cell responses have been shown to be important for protection against influenza and for recovery. CD4 + T cell responses are also critical for efficient CD8 + T cell response and antibody response. As immunodominant T cells generally play a more important role, characterizing these immunodominant responses is critical for influenza vaccine development. We show here that the internal matrix protein 1 (M1) and nucleoprotein (NP), rather than the surface proteins reported previously, are the immunodominant targets of CD4 + T cell responses. Interestingly, these immunodominant epitope regions accumulated many mutations over time, which likely indicates increased immune pressure. These findings have significant implications for the design of T cell-based influenza vaccines.
CD8 T-cell (T(CD8+)) responses elicited by viral infection demonstrate the phenomenon of immunodominance: the numbers of T(CD8+) responding to different viral peptides vary over a wide range in a reproducible manner for individuals with the same major histocompatibility complex class I alleles. To better understand immunodominance, we examined T(CD8+) responses to multiple defined viral peptides following infection of mice with influenza virus. The immunodominance hierarchy of influenza virus-specific T(CD8+) was not greatly perturbed by the absence of either perforin or T-helper cells or by interference with B7 (CD80)-mediated signaling. These findings indicate that costimulation by antigen-presenting cells (APCs) or killing of APCs by T(CD8+) plays only a minor role in establishing the immunodominance hierarchy of antiviral T(CD8+) in this system. This points to intrinsic features of the T(CD8+) repertoire as major contributors to immunodominance.
// Jianxin Chen 1,* , Mubing Duan 2,* , Yaqin Zhao 1,4 , Fangfang Ling 1 , Kun Xiao 2 , Qian Li 2 , Bin Li 2,3 , Chunni Lu 2 , Wenbao Qi 1 , Zhenling Zeng 1 , Ming Liao 1 , Yahong Liu 1 and Weisan Chen 2 1 Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, China 2 Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia 3 National Engineering Research Center of Immunological Products, Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University, Chongqing, China 4 Present address: Xinjiang Institute of Chinese Materia Medica and Ethnic Materia Medica, Urumqi, Xinjiang, China * These authors have contributed equally to this work as first authors Correspondence to: Jianxin Chen, email: // Weisan Chen, email: // Keywords : Saikosaponin A, anti-inflammatory agent, influenza A virus, PR8, X-31, Immunology and Microbiology Section, Immune response, Immunity Received : July 05, 2015 Accepted : November 22, 2015 Published : December 02, 2015 Abstract Fatal influenza outcomes result from a combination of rapid virus replication and collateral lung tissue damage caused by exaggerated pro-inflammatory host immune cell responses. There are few therapeutic agents that target both biological processes for the attenuation of influenza-induced lung pathology. We show that Saikosaponin A, a bioactive triterpene saponin with previouslyestablished anti-inflammatory effects, demonstrates both in vitro and in vivo anti-viral activity against influenza A virus infections. Saikosaponin A attenuated the replication of three different influenza A virus strains, including a highly pathogenic H5N1 strain, in human alveolar epithelial A549 cells. This anti-viral activity occurred through both downregulation of NF-κB signaling and caspase 3-dependent virus ribonucleoprotein nuclear export as demonstrated by NF-κB subunit p65 and influenza virus nucleoprotein nuclear translocation studies in influenza virus infected A549 cells. Critically, Saikosaponin A also attenuated viral replication, aberrant pro-inflammatory cytokine production and lung histopathology in the widely established H1N1 PR8 model of influenza A virus lethality in C57BL/6 mice. Flow cytometry studies of mouse bronchoalveolar lavage cells revealed that SSa exerted immunomodulatory effects through a selective attenuation of lung neutrophil and monocyte recruitment during the early peak of the innate immune response to PR8 infection. Altogether, our results indicate that Saikosaponin A possesses novel therapeutic potential for the treatment of pathological influenza virus infections.
<p>Figure S1. NK cell and T cell numbers in the peripheral blood, non-tumor and tumor tissues of GC patients. Figure S2. Expression of activating and inhibitory receptors on NK cells in the peripheral blood, non-tumor and tumor tissues of GC patients. Figure S3. Expression of CD56 and CD16 on NK cells in the peripheral blood, non-tumor and tumor tissues of GC patients. Figure S4. The expression of HLA-DR on tissue-associated monocytes/macrophages in GC patients. Figure S5. The expression of CD48, PD-L1 and PD-L2 on tissue-associated monocytes/macrophages in GC patients. Figure S6. Co-expression of CD68 and TGF-beta1 in tumors of GC patients. Figure S7. Surface expression levels of TGF-beta1 on tumor-associated monocytes/macrophages in GC patients. Table S1. Clinical characteristics of 65 GC patients. Table S2. Fluorochrome-conjugated antibodies used in flow cytometry. Table S3. Univariate and multivariate analyses of factors associated with survival.</p>
<div>Abstract<p>Actin cytoskeleton dynamic rearrangement is required for tumor cell metastasis and is a key characteristic of <i>Helicobacter pylori</i> (<i>H. pylori</i>)-infected host cells. Actin cytoskeleton modulation is coordinated by multiple actin-binding proteins (ABP). Through Kyoto encyclopedia of gene and genomes database, GEPIA website, and real-time PCR data, we found that <i>H. pylori</i> infection significantly induced L-plastin, a key ABP, in gastric cancer cells. We further explored the regulation and function of L-plastin in <i>H. pylori</i>–associated gastric cancer and found that, mechanistically, <i>H. pylori</i> infection induced gastric cancer cells to express L-plastin via <i>cagA</i>-activated ERK signaling pathway to mediate SP1 binding to L-plastin promoter. Moreover, this increased L-plastin promoted gastric cancer cell proliferation and migration <i>in vitro</i> and facilitated the growth and metastasis of gastric cancer <i>in vivo</i>. Finally, we detected the expression pattern of L-plastin in gastric cancer tissues, and found that L-plastin was increased in gastric cancer tissues and that this increase of L-plastin positively correlated with <i>cagA</i><sup>+</sup> <i>H. pylori</i> infection status. Overall, our results elucidate a novel mechanism of L-plastin expression induced by <i>H. pylori</i>, and a new function of L-plastin–facilitated growth and metastasis of gastric cancer, and thereby implicating L-plastin as a potential therapeutic target against gastric cancer.</p>Implications:<p>Our results elucidate a novel mechanism of L-plastin expression induced by <i>H. pylori</i> in gastric cancer, and a new function of L-plastin–facilitated gastric cancer growth and metastasis, implicating L-plastin as a potential therapeutic target against gastric cancer.</p></div>
Abstract Immunodominant T cell responses are important for virus clearance. However, the identification of immunodominant T cell peptide+HLA glycoprotein epitopes has been hindered by the extent of HLA polymorphism and the limitations of predictive algorithms. A simple, systematic approach has been used here to screen for new, immunodominant CD8+ T cell epitopes. The analysis targeted healthy HLA-A2+ and HLA-A2- donors. While M158A2 was consistently detected in all individual samples in our study, the response to this epitope was only immunodominant in three out of eight while, for the other five, prominent CD8+ T cell responses tended to focus on various peptides from the influenza nucleoprotein (NP) that were not presented by HLA-A2. In all the tested 7 A2- individuals, immunodominant responses all focused on NP. Importantly, most novel, immunodominant T cell epitopes identified by our study would not have been predicted by the current prediction programs as they are either too long or lacking typical HLA binding motifs. Our data stress the importance of systematic analysis for discovering HLA-dependent, immunodominant CD8+ T cell epitopes derived from viruses and tumors. Focusing on HLA-A2 and predictive algorithms may be too limiting as we seek to develop targeted immunotherapy and vaccine strategies that depend on T cell-mediated immunity.
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