Skin tumor immunity: Site does matter for antigen presentation by DCs

The immune system has the ability to specifically identify and eliminate tumors, but the underlying mechanisms responsible for this phenomenon are not fully understood. A study published in this issue of the European Journal of Immunology now provides new insights into this important problem. Joncker et al. [Eur. J. Immunol. 2016. 46: 609‐618] show that the timely mobilization of tumor antigen‐bearing dendritic cells (DCs) from the periphery to the lymph nodes is critical for effective antitumor T‐cell immunity, and that DCs present tumor antigens much more efficiently when encountered in the skin rather than in the subcutaneous tissues.     

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

In the thymus, a T‐cell repertoire able to confer protection against infectious and noninfectious agents in a peptide‐dependent, self‐MHC‐restricted manner is selected. Direct detection of Ag‐specific thymocytes, and analysis of the impact of the expression of the MHC‐restricting allele on their frequency or function has never been studied in humans because of the extremely low precursor frequency. Here, we used a tetramer‐based enrichment protocol to analyze the ex vivo frequency and activation‐phenotype of human thymocytes specific for self, viral and tumor‐antigens presented by HLA‐A*0201 (A2) in individuals expressing or not this allele. Ag‐specific thymocytes were quantified within both CD4CD8 double or single‐positive compartments in every donor. Our data indicate that the maturation efficiency of Ag‐specific thymocytes is poorly affected by HLA‐A2 expression, in terms of frequencies. Nevertheless, A2‐restricted T‐cell lines from A2⁺ donors reacted to A2⁺ cell lines in a highly peptide‐specific fashion, whereas their alloreactive counterparts showed off‐target activity. This first ex vivo analysis of human antigen‐specific thymocytes at different stages of human T‐cell development should open new perspectives in the understanding of the human thymic selection process.     

Microenvironmental stresses induce HLA‐E/Qa‐1 surface expression and thereby reduce CD8+ T‐cell recognition of stressed cells

Hypoxia and glucose deprivation are often observed in the microenvironment surrounding solid tumors in vivo. However, how they interfere with MHC class I antigen processing and CD8⁺ T‐cell responses remains unclear. In this study, we analyzed the production of antigenic peptides presented by classical MHC class I in mice, and showed that it is quantitatively decreased in the cells exposed to either hypoxia or glucose deprivation. In addition, we unexpectedly found increased surface expression of HLA‐E in human and Qa‐1 in mouse tumor cells exposed to combined oxygen and glucose deprivation. The induced Qa‐1 on the stressed tumor model interacted with an inhibitory NKG2/CD94 receptor on activated CD8⁺ T cells and attenuated their specific response to the antigen. Our results thus suggest that microenvironmental stresses modulate not only classical but also nonclassical MHC class I presentation, and confer the stressed cells the capability to escape from the CD8⁺ T‐cell recognition.     

TAP‐mediated processing of exoerythrocytic antigens is essential for protection induced with radiation‐attenuated Plasmodium sporozoites

MHC class I dependent CD8⁺ T cells are essential for protection induced by radiation‐attenuated Plasmodium sporozoites (RAS) in murine malaria models. Apart from the mechanism of activation of CD8⁺ T cells specific for the circumsporozoite protein, the major sporozoite antigen (Ag), CD8⁺ T cells specific for other exoerythrocytic Ags that have been shown to mediate protection have not been thoroughly investigated. Specifically, mechanisms of processing and presentation of exoerythrocytic Ags, which includes liver stage (LS) Ags, remain poorly understood. We hypothesize that as exogenous proteins, LS Ags are processed by mechanisms involving either the TAP‐dependent phagosomal‐to‐cytosol or TAP‐independent vacuolar pathway of cross‐presentation. We used TAP‐deficient mice to investigate whether LS Ag mediated induction of naïve CD8⁺ T cells and their recall during sporozoite challenge occur by the TAP‐dependent or TAP‐independent pathways. On the basis of functional attributes, CD8⁺ T cells were activated via the TAP‐independent pathway during immunizations with Plasmodium berghei RAS; however, IFN‐γ⁺CD8⁺ T cells previously induced by P. berghei RAS in TAP‐deficient mice failed to be recalled against sporozoite challenge and the mice became parasitemic. On the basis of these observations, we propose that TAP‐associated Ag processing is indispensable for sterile protection induced with P. berghei RAS.     

S1P1 downregulation tailors CD8+ T‐cell residence time in lymph nodes to the strength of the antigenic stimulation

T cells are sequestered for several days in lymph nodes following antigen recognition but the precise mechanism regulating their timing of egress is not fully understood. In particular, whether interactions with antigen‐presenting cells (APCs) and/or strength of the TCR stimulation shape T‐cell residence time is unclear. We report here that the probability of T‐cell egress decreases upon stimulation with high affinity TCR ligands. In contrast, low affinity peptides favor early egress, a phenomenon that could be reversed by sustaining antigen availability. The delayed egress of high affinity T cells could not be accounted by physical sequestration by APCs. Instead, we found that the sphingosine‐1‐phosphate receptor (S1P₁) downregulation mirrors the strength and persistence of the TCR stimulation, limiting egress of high affinity T cells. We propose that S1P₁ acts as a rheostat to tailor T‐cell residence time in the lymph node to the local availability of antigen and to optimize the expansion of high affinity T cells.     

Clinical Evaluation of Rapid Diagnostic Test Kit Using the Polysaccharide as a Genus-Specific Diagnostic Antigen for Leptospirosis in Korea,Bulgaria, and Argentina

Leptospirosis, a zoonotic disease that is caused by many serovars which are more than 200 in the world, is an emerging worldwide disease. Accurate and rapid diagnostic tests for leptospirosis are a critical step to diagnose the disease. There are some commercial kits available for diagnosis of leptospirosis, but the obscurity of a species- or genus-specific antigen of pathogenic Leptospira interrogans causes the reduced sensitivity and specificity. In this study, the polysaccharide derived from lipopolysaccharide (LPS) of nonpathogenic Leptospira biflexa serovar patoc was prepared, and the antigenicity was confirmed by immunoblot and enzyme linked immunosorbent assay (ELISA). The performance of the rapid diagnostic test (RDT) kit using the polysaccharide as a diagnostic antigen was evaluated in Korea, Bulgaria and Argentina. The sensitivity was 93.9%, 100%, and 81.0% and the specificity was 97.9%, 100%, and 95.4% in Korea (which is a rare region occurring with 2 serovars mostly), Bulgaria (epidemic region with 3 serovars chiefly) and Argentina (endemic region with 19 serovars mainly) respectively. These results indicate that this RDT is applicable for global diagnosis of leptospirosis. This rapid and effective diagnosis will be helpful for diagnosis and manage of leptospirosis to use and the polysaccharide of Leptospira may be called as genus specific antigen for diagnosis.     

蓝氏贾第鞭毛虫抗原快速检测与多重PCR检测的比较

目的比较蓝氏贾第鞭毛虫抗原快速检测法与多重PCR检测法检测结果间的相关性,为蓝氏贾第鞭毛虫快速筛查提供依据。方法采用抗原快速检测法与多重PCR检测法同时测定102例具有相关症状体征病人的粪便标本,确定病人蓝氏贾第鞭毛虫感染状况。结果共检测腹泻患者粪便标本102例,抗原快速检测法检测阳性81例,阴性21例,多重PCR检测阳性标本83例,阴性19例。抗原快速检测阳性而多重PCR检测确认阴性的标本0例;抗原快速检测阴性而多重PCR检测阳性的标本2例。抗原快速检测对蓝氏贾第鞭毛虫的阳性预示值为100.0%,阴性预示值为90.5%,诊断灵敏度是97.6%,诊断特异性是100.0%。结论采用抗原快速检测法检测蓝氏贾第鞭毛虫抗原,15 min内可筛查标本中的病原体,利于疾病的早期预防、诊断和治疗,防止社区/区域流行。     

Major inter-laboratory variations in PSA testing practices: results from national surveys in Ireland in 2006 and 2007

Background  Ireland had the highest prostate cancer incidence in Europe in 2006. In that year, the National Cancer Forum (NCF) recommended against prostate specific antigen (PSA) testing for population-based screening. Aims  To investigate (1) PSA services and (2) impact of the NCF recommendation. Methods  Questionnaires were dispatched to biochemistry laboratories nationwide in 2006 and 2007. Results  All 55 laboratories responded in 2006; 33/36 (89%) responded in 2007. 36 laboratories measured total PSA (tPSA); 14 measured free PSA (fPSA). Laboratories with higher tPSA workload were more likely to measure fPSA (P = 0.024). A total of 15 laboratories used age-specific PSA ranges. In 2006, there were >382,000 tPSA and >48,000 fPSA tests costing an estimated €4,900,000. During 2006–2007 tPSA tests increased by 11%; fPSA tests decreased by 36%. Conclusions  There is considerable inter-laboratory variation in PSA testing practices. Because of the potential clinical consequences, standardisation should be considered. Testing practice was unaffected by the NCF recommendation.     

Nanotechnology in vaccine delivery

With very few adjuvants currently being used in marketed human vaccines, a critical need exists for novel immunopotentiators and delivery vehicles capable of eliciting humoral, cellular and mucosal immunity. Such crucial vaccine components could facilitate the development of novel vaccines for viral and parasitic infections, such as hepatitis, HIV, malaria, cancer, etc. In this review, we discuss clinical trial results for various vaccine adjuvants and delivery vehicles being developed that are approximately nanoscale (< 1000 nm) in size. Humoral immune responses have been observed for most adjuvants and delivery platforms while only viral vectors, ISCOMs and Montanide™ ISA 51 and 720 have shown cytotoxic T cell responses in the clinic. MF59 and MPL® have elicited Th1 responses, and virus-like particles, non-degradable nanoparticles and liposomes have also generated cellular immunity. Such vaccine components have also been evaluated for alternative routes of administration with clinical successes reported for intranasal delivery of viral vectors and proteosomes and oral delivery of a VLP vaccine.     

盐酸抗原修复Brdu免疫组化检测在脑组织中的应用

目的探索简单有效的Brdu免疫组织化学染色抗原修复方法,提高实验成功率和改善实验结果。方法通过实验对三种抗原修复方法:1水浴锅煮沸修复法,2微波修复法,3Hcl酸化破膜法,采集图像进行比较,探索出Brdu免疫组织化学DAB染色最有效方法。结果 1水浴锅煮沸修复法:组织抗原暴露不全,背景较深,不能很好的显示Brdu的阳性结果。2微波修复法:组织中Brdu暴露不全,增加加热时间会使组织切片脱落严重,加热时间少则背景深,Brdu不能很好的与抗体结合,实验多数为阴性。3Hcl酸修复法:组织背景色较浅,Brdu阳性与背景色对比明显,同时能完全检测Brdu在细胞中的位置。结论 Hcl酸化修复法能很好的显示细胞核DNA镶嵌的Brdu,抗体容易进入细胞核中与之结合,显色效果明显,操作简单易行,同时无热源,安全性较好,是一种较为理想的检测方法。