Yoshie Kametani

Functional human humoral immunity remains one of the greatest challenges in humanized mouse research. Although numerous humanized mouse models have been developed, reproducing efficient antigen-specific antibody responses remains difficult. This review proposes a conceptual framework for evaluating humanized mouse models based on the reconstruction of functional humoral immune modules rather than the presence of individual immune cell populations. Functional humoral immunity depends on the coordinated reconstruction of functional modules established through productive cognate interactions between immune cells within spatially organized lymphoid microenvironments. Comparative analyses of representative humanized mouse models demonstrated that these functional modules were only partially reconstructed and differed substantially among currently available models. Moreover, the duration of the humoral immunity window, during which the functional modules required for humoral immunity remain sufficiently coordinated to support productive cognate interactions and effective antigen-specific antibody responses, is limited in current humanized mouse models. Therefore, we propose a spatiotemporal framework for the design, evaluation, and application of next-generation humanized mouse models.

Functional human humoral immunity remains one of the greatest challenges in humanized mouse research. Although numerous humanized mouse models have been developed, efficient antigen-specific antibody responses remain difficult to reproduce. This review proposes a conceptual framework for evaluating humanized mouse models based on the reconstruction of functional humoral immune modules rather than the presence of individual immune-cell populations. Functional humoral immunity depends on the coordinated reconstruction of functional modules established through productive cognate interactions among immune cells within spatially organized lymphoid microenvironments. Comparative analyses of representative humanized mouse models demonstrate that these functional modules are only partially reconstructed and differ substantially among currently available models. Moreover, the duration of the humoral immunity window—the period during which the functional modules required for humoral immunity remain sufficiently coordinated to support productive cognate interactions and effective antigen-specific antibody responses—is limited in current humanized mouse models. We therefore propose a spatiotemporal framework for the design, evaluation, and fit-for-purpose application of next-generation humanized mouse models.

Cancer peptide vaccines harness the host immune system to generate tumor‐specific immune responses, offering potential for treating metastatic cancers and preventing recurrence. However, the limited immunogenicity of peptide antigens restricts their clinical efficacy, necessitating strategies to enhance their potency. One promising approach involves the conjugation of antigens with adjuvants to elicit antigen‐specific immune responses, thereby creating self‐adjuvanting vaccines. In this study, we developed an improved platform for such vaccines. Specifically, the antigenic CH401 peptide was conjugated with the adjuvant (Pam ₃ CSK ₄ ) and formulated into cationic lipid nanoparticles (LNPs) smaller than 100 nm to facilitate uptake by immune cells, with supplemental adjuvants incorporated to modulate immune responses. Notably, the microflow device iLiNP enabled precise, size‐controlled LNP formulation from various components, supporting the systematic evolution of the self‐adjuvanting vaccine platform. These vaccine candidates demonstrated enhanced immunogenicity, enabling precise modulation of immune responses in an antigen‐specific manner. Notably, these vaccines elicited potent immune responses in humanized mouse models. Overall, this strategy represents a next‐generation self‐adjuvanting vaccine platform, capable of both enhancing and fine‐tuning antigen‐specific immune responses, holding great promise for innovative vaccine development.

Immune-humanized mouse models are indispensable tools for evaluating human immune responses and testing immune-based therapies; however, the induction of robust human antigen-specific immunoglobulin G (IgG) production remains limited due to species-specific incompatibilities. To investigate how human interleukin-4 (IL-4) promotes antibody responses, we employed NOG-hIL-4 transgenic mice (NOG-hIL-4-Tg), which constitutively express human IL-4, and transplanted them with human peripheral blood mononuclear cells (PBMCs). Flow cytometry, histological analysis, and next-generation sequencing were used to assess human lymphocyte maintenance, receptor repertoire diversity, class switching, and antigen-specific responses following immunization with peptide antigens. Sustained human B cell maintenance correlated with defined supraphysiological ranges of plasma hIL-4 concentrations. T and B cell receptor repertoire analyses demonstrated stable clonal diversity for one month after engraftment, followed by contraction by three months. Immunoglobulin repertoire profiling revealed IL-4–dependent class switching to IgG, with early predominance of IgG3 that declined over time and a gradual increase in IgG1, though subclass distribution varied among donors. Immunization induced antigen-reactive IgG, although many clones displayed low-affinity or cross-reactive binding, consistent with limited affinity maturation. Histological examination revealed tertiary lymphoid structure–like accumulations of human B and T cells within the spleen, without fully developed germinal centers. These findings demonstrate that human IL-4 expression in NOG-hIL-4-Tg mice supports human B cell survival, class switching, and partial IgG maturation, providing a relevant platform for studying human humoral immunity and evaluating antibody-based immunotherapies.

Immune-related drug delivery systems (DDSs) in humanized mouse models are at the forefront of cancer research and serve as bridges between preclinical studies and clinical applications. These systems offer unique platforms for exploring new therapies and understanding their interactions with human cells and the immune system. Here, we focus on a DDS and a peripheral blood mononuclear cell (PBMC)-engrafted humanized mouse model that we recently developed, and consider some of the key components, challenges, and applications to advance these systems towards better cancer treatment on the basis of a better understanding of the immune response. Our DDS is unique and has a dual function, an anticancer effect and a capacity to fine-tune the immune reaction. The PBL-NOG-hIL-4-Tg mouse system is superior to other available humanized mouse systems for the development of such multifunctional DDSs because it supports the rapid reconstruction of an individual donor’s immunity and avoids the onset of graft-versus-host disease.

Previously, we found that a greater dissimilarity in swine leukocyte antigen (SLA) class I and class II alleles between mating partners resulted in increased farrowing rates in a highly inbred population of Microminipigs (MMPs). In this follow-up study, we have analyzed the effects of dissimilarity in SLA alleles between mating partners for seven different reproductive traits, including litter size and the number of stillborn and live or dead weaned piglets. We determined the relationships among reproductive traits within each mating event and the amino acid distances of SLA alleles as markers of diversity between mating partners. Our results indicate that mating partners with greater amino acid pairwise genetic distances in the SLA-1 class I gene or DQB1 class II gene alleles were associated with significantly larger litter sizes and higher numbers of live piglets at birth and weaning. Also, partners with greater pairwise distances in the SLA-2 class I gene alleles exhibited fewer pre-weaning deaths. These findings suggest that the dissimilarity in SLA class I and class II alleles between mating partners may affect not only farrowing rates but also other key reproductive traits such as litter size and improved piglet survival rates. Consequently, SLA alleles could serve as valuable genetic markers for selecting mating partners in breeding programs and for conducting epistatic studies on various reproductive traits in MMPs.

Coccomyxa subellipsoidea KJ (C-KJ) is a green alga with unique immunoregulatory characteristics. Here, we investigated the mechanism underlying the modification of T cell function by C-KJ components. The water-soluble extract of C-KJ was fractionated into protein (P) and sugar (S) fractions acidic (AS), basic (BS), and neutral (NS). These fractions were used for the treatment of peripheral blood mononuclear cells stimulated with toxic shock syndrome toxin-1. Transcriptome analysis revealed that both P and AS enhanced the expression of the genes encoding metallothionein (MT) family proteins, inflammatory factors, and T helper (Th) 17 cytokine and suppressed that of those encoding Th2 cytokines in stimulated T cells. The kinetics of MT1 and MT2A gene expression showed a transient increase in MT1 and maintenance of MT2A mRNA after T cell stimulation in the presence of AS. The kinetics of Th17-related cytokine secretion in the early period were comparable to those of MT2A mRNA. Furthermore, our findings revealed that static, a STAT-3 inhibitor, significantly suppressed MT2A gene expression. These findings suggest that the expression of MTs is involved in the immune regulatory function of C-KJ components, which is partially regulated by Th17 responses, and may help develop innovative immunoregulatory drugs or functional foods.

Immune checkpoint inhibitors highlight the importance of anticancer immunity. However, their clinical utility and safety are limited by the low response rates and adverse effects. We focused on progesterone (P4), a hormone produced by the placenta during pregnancy, because it has multiple biological activities related to anticancer and immune regulation effects. P4 has a reversible immune regulatory function distinct from that of the stress hormone cortisol, which may drive irreversible immune suppression that promotes T cell exhaustion and apoptosis in patients with cancer. Because the anticancer effect of P4 is induced at higher than physiological concentrations, we aimed to develop a new anticancer drug by encapsulating P4 in liposomes. In this study, we prepared liposome-encapsulated anti-programmed death ligand 1 (PD-L1) antibody-conjugated P4 (Lipo-anti-PD-L1-P4) and evaluated the effects on the growth of MDA-MB-231 cells, a PD-L1-expressing triple-negative breast cancer cell line, in vitro and in NOG-hIL-4-Tg mice transplanted with human peripheral blood mononuclear cells (humanized mice). Lipo-anti-PD-L1-P4 at physiological concentrations reduced T cell exhaustion and proliferation of MDA-MB-231 in vitro. Humanized mice bearing MDA-MB-231 cells expressing PD-L1 showed suppressed tumor growth and peripheral tissue inflammation. The proportion of B cells and CD4+ T cells decreased, whereas the proportion of CD8+ T cells increased in Lipo-anti-PD-L1-P4-administrated mice spleens and tumor-infiltrated lymphocytes. Our results suggested that Lipo-anti-PD-L1-P4 establishes a systemic anticancer immune environment with minimal toxicity. Thus, the use of P4 as an anticancer drug may represent a new strategy for cancer treatment.

We have previously reported specific swine leukocyte antigen (SLA) haplotype associations with significant effects on several reproduction performance traits in a highly inbred miniature pig population of Microminipigs (MMPs). In this study, to clarify the effects on farrowing rates of SLA similarity between mating partners in the MMP population, we compared the farrowing rates as a measure of reproductive success after 1063-cumulative matings among the following three groups of mating partners: (1) completely sharing SLA class I or class II haplotypes or alleles between partners (CS), (2) only one sharing the haplotypes or alleles (OS), and (3) non-sharing the haplotypes or alleles (NS). Average farrowing rates in CS groups consisting of completely sharing SLA class II haplotypes or DRBI and DQB1 alleles were lowest in the three groups. Moreover, lower farrowing rates were indicated in mating pairs with smaller amino acid pairwise genetic distances of SLA-1, SLA-3, DRB1 and DQB1 alleles between the pairs. These results suggested that the dissimilarity of SLA class I and class II alleles between mating partners markedly improved reproductive performance; therefore, SLA alleles or haplotypes are potentially useful genetic markers for the selection of mating pairs in breeding programs and epistatic studies of reproductive traits of MMPs.