Biotherapy Institute of Japan

Abstract Human leukocyte antigen (HLA)-G is a non-classical HLA class I immunomodulatory molecule with restricted expression in the placenta, thymus and regulatory T cells. The spliced isoforms of HLA-G include an α2 domain-deleted isoform, HLA-G2, which specifically binds to the immune checkpoint leukocyte immunoglobulin-like receptor B2 (LILRB2), to suppress immune responses in myelomonocytic cells. We previously reported the structural and receptor binding characteristics of recombinant HLA-G2 protein and its immunosuppressive effects on inflammation in mouse models. However, the function and the mechanism of action of HLA-G2 on human immune cells have not been elucidated.In the present study, we demonstrate the immunosuppressive effect of HLA-G2 on human CD14-positive monocytic cells. HLA-G2 induced the production of the immunosuppressive cytokine, IL-10, and stimulated IL-6/STAT3/indoleamine-2,3-dioxygenase signaling by binding to LILRB2. HLA-G2 binding to LILRB2 also down-regulated cell surface expression of HLA-DR and CD86. Unexpectedly, HLA-G2 up-regulated cell surface expression of PD-L1 in both CD14-positive monocytic cells and interferon-induced dendritic cells (IFN-DCs). This observation suggests HLA-G2/LILRB2 signaling promotes PD-L1 expression. Furthermore, HLA-G2 treatment of IFN-DCs suppressed T cell proliferation in mixed lymphocyte reactions. These findings provide novel insights into the modulation of human immune responses of tolerogenic myelomonocytic cells induced by HLA-G2 binding to LILRB2, and suggest that targeting the HLA-G2-LILRB2 interaction could be a novel approach for immune checkpoint therapy.Significance statementDuring pregnancy, HLA-G isoforms are expressed by fetal trophoblasts to suppress maternal immune responses. Among various HLA-G isoforms, the HLA-G2 homodimer has been expected as an immunosuppressive biologic targeting myelomonocytic antigen-presenting cells via leukocyte immunoglobulin-like receptor B2. We previously reported significant immunosuppressive effects of HLA-G2 in autoimmune mouse models. Here, we first demonstrate that HLA-G2 isoform induces tolerogenic phenotypes of human peripheral immune cells by significantly upregulating an immune checkpoint molecule, PD-L1. Monocyte-derived dendritic cells stimulated by HLA-G2 suppressed T cell proliferation in mixed lymphocyte reactions. These results suggest that HLA-G2 can be a novel candidate for immune checkpoint therapy.

In recent years, tumor immunotherapy has produced remarkable results in tumor treatment. Nevertheless, its effects are severely limited in patients with low or absent pre-existing T cell immunity. Accordingly, metastasis remains the major cause of tumor-associated death. On the other hand, natural killer (NK) cells have the unique ability to recognize and rapidly act against tumor cells and surveil tumor cell dissemination. The role of NK cells in metastasis prevention is undisputable as an increase in the number of these cells mostly leads to a favorable prognosis. Hence, it is reasonable to consider that successful metastasis involves evasion of NK-cell-mediated immunosurveillance. Therefore, harnessing NK cells to control metastasis is promising. Circulating tumor cells (CTCs) are the seeds for distant metastasis, and the number of CTCs detected in the blood of patients with tumor is associated with a worse prognosis, whereas NK cells can eliminate highly motile CTCs especially in the blood. Here, we review the role of NK cells during metastasis, particularly the specific interactions of NK cells with CTCs, which may provide essential clues on how to harness the power of NK cells against tumor metastasis. As a result, a new way to prevent or treat metastatic tumor may be developed.

Advanced gall bladder cancer generally has a poor prognosis and also shows decreased response to conventional therapies like chemotherapy and radiotherapy. Though surgical resection is the most common approach followed, the 1-year survival rate is only 10%. Herein, we report the outcome of administration of autologous natural killer cell and activated T lymphocyte-based autologous immune enhancement therapy (AIET) in a case of gall bladder cancer stage IV which was progressing in spite of surgical resection and several sittings of chemotherapy. There were no adverse reactions after AIET. After three infusions of AIET, an improvement of the quality of life and general condition which is sustaining for more than 6 months and a substantial decrease in the CA 19-9 marker levels from 2938.22 U/mL before AIET to 511 U/mL, 5 months after AIET, in our experience make us recommend AIET along with other conventional treatments in similar cases.

TRIM5alpha is one of the factors contributing to intracellular defense mechanisms against HIV-1 infection. We investigated the association of TRIM5alpha sequence variations with the susceptibility to HIV-1 infection in Japanese and Indian. Sequence variations in TRIM5alpha were investigated in HIV-1-infected patients and ethnic-matched controls. Functional alterations caused by rare variants were analyzed. : We sequenced TRIM5alpha-exon 2 in both Japanese (94 HIV-1-infected patients and 487 controls) and Indian (101 HIV-1-infected patients and 99 controls). Frequency of variants and haplotypes were compared between the HIV-1-infected patients and controls. Functional analyses were performed for two rare variants, Gly110Arg and G176del. The frequency of 43Tyr-allele in the Indian HIV-1-infected patients was significantly lower than that in the ethnic-matched controls (odds ratio = 0.52, 95% confidence interval = 0.31-0.89, P = 0.015). A similar tendency was observed in Japanese sample, although it was not statistically significant (odds ratio = 0.67, 95% confidence interval = 0.43-1.05, P = 0.095). On the other hand, haplotype analyses revealed that the haplotype carrying the 43Tyr-allele was significantly associated with the reduced susceptibility to HIV-1 infection in both ethnic groups. Functional analysis revealed that Gly110Arg variant weakened the anti-HIV-1 and anti-HIV-2 activities of human TRIM5alpha, whereas the truncated G176del-TRIM5 enhanced the antiviral activity of coexpressed TRIM5alpha. Epidemiological data were consistent in that Gly110Arg and G176del were associated with the susceptibility to and protection from HIV-1 infection, respectively. Both common and rare variants of TRIM5alpha are associated with the susceptibility to HIV-1 infection.