New strategies for efficient typing of HLA class-II loci DQB1 and DRB1 by using Pyrosequencing

Radical hemithorax radiotherapy induces an increase in circulating PD-1+ T lymphocytes and in the soluble levels of PD-L1 in malignant pleural mesothelioma patients: a possible synergy with PD-1/PD-L1 targeting treatment?

Malignant Pleural Mesothelioma (MPM) is an aggressive tumor associated with asbestos exposure, characterized by a poor prognosis, managed with surgery, chemotherapy and radiotherapy. Recently, immunotherapy gives a survival advantage compared to chemotherapy, but limited to the non-epithelioid histotype, the rarest type. Radical hemithorax radiotherapy (RHRT) improves the Overall Survival (OS) of MPM patients, irrespective of histotype, and is able to induce immunomodulatory effects. In this study we aim to investigate changes in circulating T lymphocytes phenotype and activity, in MPM patients undergoing RHRT, to evaluate a possible therapeutic space for immunotherapy in this setting. To assess immunomodulatory effects of RHRT we evaluate peripheral blood samples of 35 MPM patients collected before treatment, at the end of RT, and 1 month later. We first notice that higher Lymphocyte-to-Monocyte Ratio (LMR) levels, before RT, are associated with an improved OS. The immune monitoring performed by ELISA assays reveals a significant increase in the serum levels of soluble PD-L1 (sPD-L1) and IFN-γ at the end of RHRT. Furthermore, the percentage of PD-1+ cells, evaluated by flow cytometry, significantly raise after RHRT in T cells, both CD4+ and CD8+. Also the proportion of proliferative cells is significantly expanded after RHRT in all T cell subtypes. After treatment we observe a significant increase in the number of patients showing WT-1 specific CD4+ T cells, measured by intracellular staining. The TCR repertoire analysis, investigated by Next Generation Sequencing, reveals an increased number of expanded T-cell clones after RHRT, and an association between TCR clonality and the percentage of proliferating cytotoxic T lymphocytes. The comparison of TCR sequences obtained in our cohort with those described in a literature cohort of MPM patients, reveals common entries, specific for MPM-associated antigens including WT-1. In this setting, pre-treatment levels of LMR seem to have a positive prognostic role, and RHRT would appear to induce immunomodulating effects, potential biomarkers for immunotherapy eligibility: i.e. increased PD-1+ T lymphocytes, proliferating T cells, expanded T cell clones and augmented levels of sPD-L1. These data suggest the design of a prospective study evaluating a maintenance immunotherapy after RHRT in MPM, even in the epithelioid histotype.

Local High-Dose Radiotherapy Induces Systemic Immunomodulating Effects of Potential Therapeutic Relevance in Oligometastatic Breast Cancer

Local irradiation of cancer through radiotherapy can induce spontaneous regression of non-directly irradiated lesions, suggesting the involvement of systemic antitumor immune responses. In oligometastatic breast cancer (BC) patients, the use of stereotactic body radiotherapy (SBRT) favors the local control of treated lesions and may contribute to break local tolerance and release tumor-associated antigens (TAAs), improving host antitumor immunity. We performed a detailed immunomonitoring of BC patients undergoing SBRT to verify its ability to “switch on” the anti-tumor immunity both systemically, in peripheral blood, and locally, employing in vitro BC models. Twenty-one BC patients with ≤6 metastases were treated with 3 daily doses of 10 Gy with SBRT. Blood samples for immune profiling were collected before and after treatment. One month after treatment a third of patients displayed the boosting or even the de novo appearance of polyfunctional CD4⁺ and CD8⁺ T cell responses against known BC TAAs (survivin, mammaglobin-A, HER2), through intracellular staining in flow cytometry. Half of patients showed increased numbers of activated natural killer (NK) cells, measured with multispectral flow cytometry, immediately after the first dose of SBRT. Interestingly, high levels of activated NK cells at diagnosis correlated with a longer progression-free survival. BC in vitro models, treated with the same SBRT modality, showed enhanced expression of MHC class-I and class-II, major histocompatibility complex class I-related chain A/B, and Fas molecules, and increased release of pro-inflammatory cytokines, such as IL-1β and TNF-α. Consistently, we noticed enhanced production of perforin by CD4⁺ T cells when patients’ lymphocytes were cultured in the presence of irradiated BC cell line, compared to untreated targets. Besides immunogenic effects, SBRT also enhanced the percentages of circulating regulatory T cells, and increased indoleamine 2,3 dioxygenase and PD-L1 expression in BC in vitro models. These results suggest that SBRT may boost host antitumor immune responses also in an advanced disease setting such as oligometastatic BC, by inducing immunomodulating effects both locally and systemically. However, the concomitant induction of immunosuppressive pathways suggests that a combination with immunotherapy could further enhance the in situ vaccination ability of radiotherapy, possibly further improving the curative potential of SBRT in this subset of patients.

Rapid high-throughput human leukocyte antigen typing by massively parallel pyrosequencing for high-resolution allele identification

Transplantation and, notably, hematopoietic stem cell transplantation require high-resolution human leukocyte antigen (HLA) typing and, because of the heterozygous genomic DNA samples, are dependent on clonal analytical methods. High-resolution HLA typing is a necessity for accomplishing the best possible histocompatibility match between donor and recipient, because mismatches strongly increase the risk of severe acute graft-versus-host disease. We describe the development and first application in a clinical setting of a novel, HLA sequence-based typing method by exploring the next-generation sequencing technology as provided by the Genome Sequencer FLX system (Roche/454 Life Sciences, Branford, CT). The developed system allows for ambiguity-free, high-throughput, high-resolution HLA-A and -B typing with the potential for automation. Primers and Genome Sequencer FLX specific adapters were lengthened with donor-identifying barcode sequences to identify each of eight Caucasian reference donors within one single multiplex sequencing run. Compared with normal SBT HLA typing, results indicate that every patient was identified correctly with an average of 1000 reads per amplicon. Furthermore, current investments for increased read lengths and fully automated molecular diagnostic software tools, using original GS-FLX data file formats, will enhance this novel HLA typing strategy in the near future.

Multiplex HLA-typing by pyrosequencing

Class I and II loci of the human leukocyte antigens (HLA) represent the most polymorphic region of the genome. Evolutionary pressure has resulted in a large number of allelic variants of these loci ensuring the high frequency of heterozygous genotypes observed in human populations. Molecular techniques, including sequencing, are capable of precisely defining HLA alleles. Sequencing by synthesis methodology employed by pyrosequencing represents a complementary approach to other molecular methods of HLA genotyping. Out-of-phase sequencing of HLA alleles by pyrosequencing can resolve certain cis/trans ambiguities that would otherwise require the sequencing of cloned DNA. Genotyping of HLA loci for the presence of specific amino acid variants is beneficial for proper matching of organ donor to recipient, the monitoring of HLA associated genetic risk to autoimmune diseases, population genetic studies, as well as evaluation of the genetics of human host-human pathogen interaction.

The association between type 1 diabetes and the ITPR3 gene polymorphism due to linkage disequilibrium with HLA class II

A fine mapping study of the MHC region in a Swedish case-control population sample reported a novel type 1 diabetes (T1D) association from the inositol 1-, 4-, 5-trisphosphate receptor type 3 gene (ITPR3) in a case-control study, reportedly independent of the HLA class II effect. We attempted to replicate this novel association in a family-based study of 1120 T1D families with at least one affected child, an approach immune to population stratification. We found association of the ITPR3 single nucleotide polymorphisms (SNPs) rs2296336 with T1D but in a direction opposite to that reported. Moreover, rs2296336 was in linkage disequilibrium (LD) with specific alleles of the HLA DQB1 gene. Conditional regression showed that all of the ITPR3 SNP T1D association could be accounted for by the DQB1 effect. Therefore, our findings do not support an obvious role of genetic variation of the ITPR3 gene in T1D risk.

Genetic control of alternative splicing in the TAP2 gene: possible implication in the genetics of type 1 diabetes

The transporter 2, ATP-binding cassette, subfamily B (TAP2) is involved in the transport of antigenic peptides to HLA molecules. Coding TAP2 polymorphisms shows a strong association with type 1 diabetes, but it is not clear whether this association may be entirely due to linkage disequilibrium with HLA DR and DQ. Functionally, rat Tap2 nonsynonymous single-nucleotide polymorphisms (nsSNPs) confer differential selectivity for antigenic peptides, but this was not shown to be the case for human TAP2 nsSNPs. In the human, differential peptide selectivity is rather conferred by two splicing isoforms with alternative carboxy terminals. Here, we tested the hypothesis that alleles at the coding SNPs favor different splicing isoforms, thus determining peptide selectivity indirectly. This may be the basis for independent contribution to the type 1 diabetes association. In RNA from heterozygous lymphoblastoid lines, we measured the relative abundance of each SNP haplotype in each isoform. In isoform NM_000544, the G (Ala) allele at 665 Thr>Ala (rs241447) is more than twice as abundant as A (Thr) (GA = 2.2 +/- 0.4, P = 1.5 x 10(-4)), while isoform NM_018833 is derived almost exclusively from chromosomes carrying A (AG = 18.1 +/- 5.6, P = 2.04 x 10(-7)). In 889 Canadian children with type 1 diabetes, differential transmission of parental TAP2 alleles persisted (P = 0.011) when analysis was confined to chromosomes carrying only DQ*02 alleles, which mark a conserved DR-DQ haplotype, thus eliminating most of the variation at DR-DQ. Thus, we present evidence of TAP2 association with type 1 diabetes that is independent of HLA DR-DQ and describe a plausible functional mechanism based on allele dependence of splicing into isoforms known to have differential peptide selectivities.

Emerging technologies in DNA sequencing

Demand for DNA sequence information has never been greater, yet current Sanger technology is too costly, time consuming, and labor intensive to meet this ongoing demand. Applications span numerous research interests, including sequence variation studies, comparative genomics and evolution, forensics, and diagnostic and applied therapeutics. Several emerging technologies show promise of delivering next-generation solutions for fast and affordable genome sequencing. In this review article, the DNA polymerase-dependent strategies of Sanger sequencing, single nucleotide addition, and cyclic reversible termination are discussed to highlight recent advances and potential challenges these technologies face in their development for ultrafast DNA sequencing.

HLA and eye disease: a synopsis

Human leukocyte antigen (HLA) gene products have been implicated in the pathogenesis of an increasing number of eye diseases, mainly inflammatory in nature. This perspective reviews the current hypotheses for why HLA polymorphisms are associated with specific eye diseases. Statistical problems in studies involving HLA associations are discussed, and possible solutions outlined. The relevance of HLA testing in routine ophthalmic practice, its practical and cost implications is also assessed.