Expression and bioactivity of human α-fetoprotein in a Bac-to-Bac system

The role of alpha-fetoprotein in the tumor microenvironment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a prevalent malignant cancer worldwide, characterized by high morbidity and mortality rates. Alpha-fetoprotein (AFP) is a glycoprotein synthesized by the liver and yolk sac during fetal development. However, the serum levels of AFP exhibit a significant correlation with the onset and progression of HCC in adults. Extensive research has demonstrated that the tumor microenvironment (TME) plays a crucial role in the malignant transformation of HCC, and AFP is a key factor in the TME, promoting HCC development. The objective of this review was to analyze the existing knowledge regarding the role of AFP in the TME. Specifically, this review focused on the effect of AFP on various cells in the TME, tumor immune evasion, and clinical application of AFP in the diagnosis and treatment of HCC. These findings offer valuable insights into the clinical treatment of HCC.

α-Fetoprotein fragment synergizes with sorafenib to inhibit hepatoma cell growth and migration and promote the apoptosis

Alpha fetoprotein (AFP) is associated with hepatocellular carcinoma (HCC) by stimulating the proliferation, metastasis and drug resistance. The application of AFP fragments to inhibit the malignant behaviours induced by AFP is a new strategy for the treatment of HCC. In an effort to design, screen and discover drugs, we attempted to express different human AFP fragments (AFP^220-609 , AFP^390-609 and AFP^460-609 ) in a Bac-to-Bac system. We found that the AFP^390-609 fragment was highly expressed in the system. Then, we assessed the bioactivity of the fragment in the human liver cancer cell line Bel7402, and the results indicated that the AFP fragment synergized with sorafenib to inhibit the hepatoma cell growth and migration and promote the apoptosis. This study provides a method to produce significant AFP fragments to screen AFP inhibitors for use in HCC therapy.

Characterization of virus-like particles assembled by co-expression of BmCPV capsid shell protein and large protrusion protein

Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is a typical single-layer capsid dsRNA virus belonging to the Reoviridae family of the Cypovirus genus. Previous studies have shown that the BmCPV major capsid shell protein (CSP) has the ability to self-assemble into virus-like particles (VLPs), and cryo-electron microscopy of the BmCPV virions has revealed a tight mutual binding region between CSP and another capsid protein known as the Large Protrusion Protein (LPP), which further stabilizes the capsid shell. In this study, the multi-gene baculovirus expression system, Ac-MultiBac, was used to produce both solely CSP-based and CSP-LPP co-assembled VLPs. Transmission electron microscopy (TEM) results showed that addition of LPP did not affect the assembly of VLPs resulting in almost identical structure in both cases. However, ex vivo administration of VLPs to silkworm midgut tissue showed that CSP-based VLPs did not induce a significant transcriptional response in the innate immunity and RNAi gene cascades, compared to the co-assembled CSP-LPP based VLPs and the natural BmCPV virions isolated from polyhedra. The experimental results indicate that CSP and LPP attach tightly ("Plug and Display" model with CSP acting as "catcher" and LPP as "tag") to form VLPs that have a structure similar to that of the native CPV virions. Moreover, our results showed that the formation of VLPs with the two BmCPV capsid proteins is feasible, which can form the basis for the production of BmCPV-based VLPs as a new type of biological material to display exogenous proteins.

Generation and Evaluation of Recombinant Baculovirus Coexpressing GP5 and M Proteins of Porcine Reproductive and Respiratory Syndrome Virus Type 1

Porcine reproductive and respiratory syndrome virus (PRRSV) is the pathogen of the porcine reproductive and respiratory syndrome, which is one of the most economically devastating diseases of the swine industry. However, whether the inactivated vaccine and modified live attenuated vaccines are effective in disease control is still controversial. Although several groups developed PRRSV virus-like particles (VLPs) as a vaccine against PRRSV, all these VLP-based vaccines targeted PRRSV-2, but not PRRSV-1 or both. Therefore, it is urgent to produce VLPs against PRRSV-1. In this study, we rescued recombinant baculovirus expressing GP5 and M proteins of PRRSV-1 through the Bac-to-Bac^® baculovirus expression system. Thereafter, PRRSV VLP was obtained efficiently in the recombinant baculovirus-infected High Five insect cells. Moreover, the PRRSV VLP and PRRSV VLP+A5 could efficiently trigger specific humoral immune responses and B cellular immune responses through intranasal immunization. The combination of PRRSV VLP and A5 adjuvant could improve the level of the immune response. The PRRSV-1 VLPs generated in this study have greater potential for vaccine development to control PRRSV-1 infection.

Effect of mutations in capsid shell protein on the assembly of BmCPV virus-like particles

Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is a typical single-layer capsid dsRNA virus belonging to the genus Cypovirus in the family Reoviridae. The results of cryo-electron microscopy showed that the BmCPV capsid consists of 60 asymmetric units, and each asymmetric unit contains one turret protein (TP), two large protrusion proteins (LPP) and two capsid shell proteins (CSP). CSP has the ability to self-assemble into virus-like particles (VLPs), and the small protrusion domain (SPD) in CSP may play an essential role in the assembly of viral capsids. In this study, three critical amino acid sites, D828, S829 and V945, in the SPD were efficiently mutated (point mutation) based on the principle of PCR circular mutagenesis. Moreover, a multi-gene expression system, Ac-MultiBac baculovirus, was used to produce eight different recombinant VLPs in vitro. Transmission electron microscopy showed that the single site and double site mutations had little effect on the efficiency and morphology of the assembly of VLPs. Still, the simultaneous mutation of the three sites had a significant impact. The experimental results demonstrate that the SPD of CSP plays an essential role in assembly of the viral capsid, which lays the foundation for further analysis of the molecular and structural mechanism of BmCPV capsid assembly.

Purification and characterization of a bioactive alpha-fetoprotein produced by HEK-293 cells

Alpha-fetoprotein (AFP) is a biomarker that is used to diagnose hepatocellular carcinoma (HCC) and can promote malignancy in HCC. AFP is an important target in the treatment of liver cancer. To obtain enough AFP to screen for AFP inhibitors, we expressed and purified AFP in HEK-293 cells. In the present study, we produced AFP in the cells and harvested highly pure rAFP (or recombinant expression AFP in HEK-293 cells). We also analysed the bioactivity of rAFP and found that rAFP promoted growth of the human HCC cells, antagonize paclitaxel inhibition of HCC cell proliferation, suppress expression of active caspase-3, and promote expression of Ras and survivin. This study provides a method to produce significant amounts of AFP for use in biochemical assays and functional studies and to screen AFP inhibitors for use in HCC therapy.