A new therapy strategy for relapsing patients who have received trastuzumab treatment urgently needs to be explored. HER2-specific chimeric antigen receptor (CAR)-expressing NK cells are being rapidly developed for solid tumor therapy, as they have many advantages over HER2-CAR-T cells. Endogenous soluble PD-1 (sPD-1) from the PD-1 extracellular domain blocks PD-1/PD-L1 interaction to promote cancer immunology. Herein, we engineered a new HER2-CAR-NK cell that co-expresses sPD-1 (designed as sPD-1-CAR-NK cells) and assessed its cytotoxic activities toward various cancer cells, activation of immunity and sPD-1 release in vitro and in mouse models bearing breast cancer cells with high HER2 expression, with or without trastuzumab resistance. We demonstrated that sPD-1-CAR-NK cells were able to release bioactive sPD-1, thereby enhancing the cytolytic activities of HER2-CAR-NK cells against HER2 and PD-L1 highly expressing target cells accompanied by increases in the secretion of perforin, granzyme B and IFN-γ. In vivo, sPD-1-CAR-NK cells had superior immunological anticancer efficacy compared to HER2-CAR-NK cells, and they had advantages over HER2-CAR-NK cells in the intraperitoneal injection of sPD-1. Moreover, the infiltration and activation of NK and T cells into tumor tissue were increased in mice with sPD-1-CAR-NK cells. There was no significant change in the body temperature, organ tissue and body weight in all groups except for the group with the PD-1 injection. Together, these data indicate that HER2-specific sPD-1-CAR-NK cells can transport sPD-1 into cancer tissues with high HER2 expression, further improving the efficacy of HER-CAR-NK cells without obvious side effects. sPD-1-CAR-NK is a promising cytotherapeutic agent for patients bearing HER2-positive breast cancer, including those with trastuzumab resistance.

Zinc finger ZRANB2 proteins are widespread in animals, but their functions and mechanisms remain poorly defined. Here we clearly demonstrate that ZRANB2 is a newly identified LPS-binding protein present abundantly in the eggs/embryos of zebrafish. We also show that recombinant ZRANB2 (rZRANB2) acts as a pattern recognition receptor capable of identifying the bacterial signature molecule LPS as well as binding the Gram-negative bacteria Escherichia coli, Vibrio anguilarum, and Aeromonas hydrophila and functions as an antibacterial effector molecule capable of directly killing the bacteria. Furthermore, we reveal that N-terminal residues 11–37 consisting of the first ZnF_RBZ domain are indispensable for ZRANB2 antimicrobial activity. Importantly, microinjection of rZRANB2 into early embryos significantly enhanced the resistance of the embryos against pathogenic A. hydrophila challenge, and this enhanced bacterial resistance was markedly reduced by co-injection of anti-ZRANB2 antibody. Moreover, precipitation of ZRANB2 in the embryo extracts by preincubation with anti-ZRANB2 antibody caused a marked decrease in the antibacterial activity of the extracts against the bacteria tested. In addition, the N-terminal peptide Z_1/37 or Z_11/37 with in vitro antibacterial activity also promoted the resistance of embryos against A. hydrophila, but the peptide Z_38/198 without in vitro antibacterial activity did not. Collectively, these results indicate that ZRANB2 is a maternal LPS-binding protein that can protect the early embryos of zebrafish against pathogenic attacks, a novel role ever assigned to ZRANB2 proteins. This work also provides new insights into the immunological function of the zinc finger proteins that are widely distributed in various animals.

Bone morphogenetic protein (BMP) is a kind of classical multi-functional growth factor that plays a vital role in the formation and maintenance of bone, cartilage, muscle, blood vessels, and the regulation of adipogenesis and thermogenesis. However, understanding of the role of BMPs in antiviral immunity is still limited. Here we demonstrate that Bmp8a is a newly-identified positive regulator for antiviral immune responses. Thebmp8a^−/−zebrafish, when infected with viruses, show reduced antiviral immunity and increased viral load and mortality. We also show for the first time that Bmp8a interacts with Alk6a, which promotes the phosphorylation of Tbk1 and Irf3 through p38 MAPK pathway, and induces the production of type I interferons (IFNs) in response to viral infection. Our study uncovers a previously unrecognized role of Bmp8a in regulation of antiviral immune responses and provides a target for controlling viral infection.