Novel immune check point inhibiting antibodies in cancer therapy-Opportunities and challenges.

Drug resistance of tumor cells to chemotherapy is limiting the therapeutic efficacy of most anticancer drugs and represents a major obstacle in medical oncology. However, treatment of various human malignancies with biologics, mostly monoclonal antibodies (mAbs), is not limited by such chemoresistance mechanisms. However, other resistance or evasion mechanisms limit the efficacy to anticancer therapeutic mAbs that engage tumor-associated antigens on the surface of the malignant cells. Immune checkpoint blocking monoclonal antibodies are heralded as a promising therapeutic approach in clinical oncology. These mAbs do not directly attack the malignant cells as most anticancer mAbs; rather, they enhance the anti-tumor response of the immune system by targeting immune regulatory pathways. Three mAbs targeting immune checkpoint molecules are currently used in the clinic and new mAbs that target other potential inhibitory targets are being actively investigated. This therapeutic approach, while proving as highly beneficial for many patients, is prone to toxicities and side effects of an autoimmune nature. Defining suitable management algorithms and biomarkers that predict therapeutic effects and adverse toxicity are required to provide survival benefit for larger numbers of cancer patients. Overcoming these challenges, along with opportunities for new agents and combinatorial strategies are the main focus of immune checkpoint blockade research today.

Inhibitory 2B4 contributes to NK cell education and immunological derangements in XLP1 patients.

X-linked lymphoproliferative disease 1 (XLP1) is an inherited immunodeficiency, caused by mutations in SH2D1A encoding Signaling Lymphocyte Activation Molecule (SLAM)-associated protein (SAP). In XLP1, 2B4, upon engagement with CD48, has inhibitory instead of activating function. This causes a selective inability of cytotoxic effectors to kill EBV-infected cells, with dramatic clinical sequelae. Here, we investigated the NK cell education in XLP1, upon characterization of killer Ig-like receptor (KIR)/KIR-L genotype and phenotypic repertoire of self-HLA class I specific inhibitory NK receptors (self-iNKRs). We also analyzed NK-cell cytotoxicity against CD48+ or CD48- KIR-ligand matched or autologous hematopoietic cells in XLP1 patients and healthy controls. XLP1 NK cells may show a defective phenotypic repertoire with substantial proportion of cells lacking self-iNKR. These NK cells are cytotoxic and the inhibitory 2B4/CD48 pathway plays a major role to prevent killing of CD48+ EBV-transformed B cells and M1 macrophages. Importantly, self-iNKR defective NK cells kill CD48- targets, such as mature DCs. Self-iNKR- NK cells in XLP1 patients are functional even in resting conditions, suggesting a role of the inhibitory 2B4/CD48 pathway in the education process during NK-cell maturation. Killing of autologous mature DC by self-iNKR defective XLP1 NK cells may impair adaptive responses, further exacerbating the patients' immune defect.

CD8+ T cells stimulate Na-Cl co-transporter NCC in distal convoluted tubules leading to salt-sensitive hypertension.

Recent studies suggest a role for T lymphocytes in hypertension. However, whether T cells contribute to renal sodium retention and salt-sensitive hypertension is unknown. Here we demonstrate that T cells infiltrate into the kidney of salt-sensitive hypertensive animals. In particular, CD8+ T cells directly contact the distal convoluted tubule (DCT) in the kidneys of DOCA-salt mice and CD8+ T cell-injected mice, leading to up-regulation of the Na-Cl co-transporter NCC, p-NCC and the development of salt-sensitive hypertension. Co-culture with CD8+ T cells upregulates NCC in mouse DCT cells via ROS-induced activation of Src kinase, up-regulation of the K+ channel Kir4.1, and stimulation of the Cl- channel ClC-K. The last event increases chloride efflux, leading to compensatory chloride influx via NCC activation at the cost of increasing sodium retention. Collectively, these findings provide a mechanism for adaptive immunity involvement in the kidney defect in sodium handling and the pathogenesis of salt-sensitive hypertension.

Kir7.1 immunoreactivity in canine choroid plexus tumors.

Choroid plexus neoplasms are uncommon brain tumors in dogs. Choroid plexus carcinomas often spread diffusely throughout the ventricular system and subarachnoid space and, in aggressive forms, can mimic histologic patterns of other carcinomas, including being embedded in a desmoplastic reaction. Although choroid plexus tumors (CPTs) heterogeneously express pan-cytokeratin, little is known about other markers to identify choroid plexus and their associated tumors. Kir7.1, an inward-rectifier potassium channel, is reported to have high diagnostic utility in human neuropathology to distinguish CPTs from other primary brain tumors and cerebral metastases. To determine Kir7.1 expression in the dog brain, we analyzed the immunoreactivity of Kir7.1 in normal brain, gliomas, ependymomas, CPTs, meningiomas, and carcinomas. In normal brain tissue, the immunostaining was restricted to the choroid plexus where there was robust membrane immunoreactivity along the apical border of the cells with less intense cytoplasmic staining. Similar strong immunoreactivity was detected in 12 of 12 CPTs, whereas 5 of 5 gliomas, 4 of 5 ependymomas, 5 of 5 meningiomas, and 5 of 6 carcinomas had no immunoreactivity. One ependymoma and 1 nasal carcinoma with squamous metaplasia were up to 75% immunopositive, with moderate cytoplasmic and membranous immunoreactivity, but lacking the robust apical immunoreactivity pattern. Analysis for immunoreactivity in a tissue microarray failed to yield any other locations in which immunoreactivity was detected. These results, including the distinctive pattern of immunostaining in CPTs, suggest that Kir7.1 is an excellent marker for CPTs in the dog.

Choroid plexus papilloma in a beluga whale (Delphinapterus leucas).

We report herein a choroid plexus papilloma in a beluga whale (Delphinapterus leucas). This case was positive for choroid plexus tumor marker Kir7.1 on immunohistochemistry. These results and the high conservation of Kir7.1 across species at the amino acid sequence level strongly suggest that antibodies directed against Kir7.1 not only can be employed for the diagnosis of choroid plexus tumors in cetaceans, but are also likely to be diagnostically useful in other animal species.

Humoral Responses to Diverse Autoimmune Disease-Associated Antigens in Multiple Sclerosis.

UNLABELLED: To compare frequencies of autoreactive antibody responses to endogenous disease-associated antigens in healthy controls (HC), relapsing and progressive MS and to assess their associations with clinical and MRI measures of MS disease progression. METHODS: The study analyzed 969 serum samples from 315 HC, 411 relapsing remitting MS (RR-MS), 128 secondary progressive MS (SP-MS), 33 primary progressive MS (PP-MS) and 82 patients with other neurological diseases for autoantibodies against two putative MS antigens CSF114(Glc) and KIR4.1a and KIR4.1b and against 24 key endogenous antigens linked to diseases such as vasculitis, systemic sclerosis, rheumatoid arthritis, Sjogren's syndrome, systemic lupus erythematosus, polymyositis, scleroderma, polymyositis, dermatomyositis, mixed connective tissue disease and primary biliary cirrhosis. Associations with disability and MRI measures of lesional injury and neurodegeneration were assessed. RESULTS: The frequencies of anti-KIR4.1a and anti-KIR4.1b peptide IgG positivity were 9.8% and 11.4% in HC compared to 4.9% and 7.5% in RR-MS, 8.6% for both peptides in SP-MS and 6.1% for both peptides in PP-MS (p = 0.13 for KIR4.1a and p = 0.34 for KIR4.1b), respectively. Antibodies against CSF114(Glc), KIR4.1a and KIR4.1b peptides were not associated with MS compared to HC, or with MS disease progression. HLA DRB1*15:01 positivity and anti-Epstein Barr virus antibodies, which are MS risk factors, were not associated with these putative MS antibodies. CONCLUSIONS: Antibody responses to KIR4.1a and KIR4.1b peptides are not increased in MS compared to HC nor associated with MS disease progression. The frequencies of the diverse autoreactive antibodies investigated are similar in MS and HC.

Immunogenetics of HIV disease.

Host genetic factors are a major contributing factor to the inter-individual variation observed in response to human immunodeficiency virus (HIV) infection and are linked to resistance to HIV infection among exposed individuals, as well as rate of disease progression and the likelihood of viral transmission. Of the genetic variants that have been shown to affect the natural history of HIV infection, the human leukocyte antigen (HLA) class I genes exhibit the strongest and most consistent association, underscoring a central role for CD8(+) T cells in resistance to the virus. HLA proteins play important roles in T-cell-mediated adaptive immunity by presenting immunodominant HIV epitopes to cytotoxic T lymphocytes (CTLs) and CD4(+) T cells. Genetic and functional data also indicate a function for HLA in natural killer cell-mediated innate immunity against HIV by interacting with killer cell immunoglobulin-like receptors (KIR). We review the HLA and KIR associations with HIV disease and discuss the mechanisms underlying these associations.

Immunolocalization of mitoKATP subunits in human osteoblast-like cells.

The mitochondrial ATP-dependent K channel (mitoKATP) has been shown to play a role in cellular protection against apoptosis, or programmed cell death. This channel has been identified and characterized in a number of cell and tissue types but to date the possible existence of mitoKATP in osteoblastic cells has not been investigated. The aim of this investigation was to establish whether the mitochondria of human osteosarcoma-derived osteoblasts (SaOS-2 cells) contain the putative mitoKATP subunits Kir6.1 and Kir6.2. Ultrathin sections of SaOS-2 cells were prepared for transmission electron microscopy using an adaptation of the Tokuyasu method, and immunolabelled using goat anti-Kir6.1 or anti-Kir6.2 antisera as the primary label, and a 10nm colloidal gold-conjugated donkey anti-goat secondary antibody. The suitability of the antisera and the immunostaining protocol were confirmed by using a sample of rat cardiac muscle as a positive control. Ultrastructural analysis revealed that SaOS-2 cells contain Kir6.2 but not Kir6.1, and that Kir6.2 is present in the mitochondria, but in extremely low abundance. These findings suggest that human osteoblast-like cells might contain mitoKATP channels in which Kir6.2 is the pore-forming subunit, although it appears that these channels are likely to be present in extremely low abundance.

From sequence to antibody: genetic immunisation is suitable to generate antibodies against a rare plant membrane protein, the KAT 1 channel.

Monoclonal antibodies against the K(+) channel KAT1 of Arabidopsis thaliana, a low abundance, plant plasma membrane protein, were generated by genetic immunisation to avoid the time and labour consuming purification of native or recombinant proteins and peptides usually necessary for conventional immunisation techniques. The resulting polyclonal and monoclonal antibody sera recognised a single protein band in a microsomal fraction of wild-type A. thaliana leaves and in membrane fractions of transgenic yeast cells and tobacco plants expressing the KAT1 protein. Therefore, genetic immunisation is suitable for generating monoclonal antibodies against plant proteins and particularly, against plant membrane proteins of low abundance.