A novel conserved B-cell epitope in pB602L of African swine fever virus.

African swine fever virus (ASFV) is a complex DNA virus and the only member of the Asfarviridae family. It causes high mortality and severe economic losses in pigs. The ASFV pB602L protein plays a key role in virus assembly and functions as a molecular chaperone of the major capsid protein p72. In addition, pB602L is an important target for the development of diagnostic tools for African swine fever (ASF) because it is a highly immunogenic antigen against ASFV. In this study, we expressed and purified ASFV pB602L and validated its immunogenicity in serum from naturally infected pigs with ASFV. Furthermore, we successfully generated an IgG2a κ subclass monoclonal antibody (mAb 7E7) against pB602L using hybridoma technology. Using western blot and immunofluorescence assays, mAb 7E7 specifically recognized the ASFV Pig/HLJ/2018/strain and eukaryotic recombinant ASFV pB602L protein in vitro. The 474SKENLTPDE482 epitope in the ASFV pB602L C-terminus was identified as the minimal linear epitope for mAb 7E7 binding, with dozens of truncated pB602l fragments characterized by western blot assay. We also showed that this antigenic epitope sequence has a high conservation and antigenic index. Our study contributes to improved vaccine and antiviral development and provides new insights into the serologic diagnosis of ASF. KEY POINTS: • We developed a monoclonal antibody against ASFV pB602L, which can specifically recognize the ASFV Pig/HLJ/2018/ strain. • This study found one novel conserved B-cell epitope 474SKENLTPDE482. • In the 3D structure, 474SKENLTPDE482 is exposed on the surface of ASFV pB602L, forming a curved linear structure.

Identification of a novel linear B-cell epitope on the p30 protein of African swine fever virus using monoclonal antibodies.

The outbreak of African Swine Fever (ASF) has caused huge economic losses to the pig industry. There are no safe and effective vaccines or diagnostics available. The p30 protein serves as a key target for the detection of ASFV antibodies and is an essential antigenic protein for early serological diagnosis. Here, the p30 protein was purified after being expressed in E. coli and its immunogenicity was verified in sera from pigs naturally infected with ASFV. Furthermore, a monoclonal antibody (McAb) designated as McAb 1B4G2-4 (subtype IgG1/kappa-type) was produced and it was verified to specifically recognize the ASFV Pig/HLJ/2018/strain and eukaryotic recombinant ASFV p30 protein. The epitope identified by McAb 1B4G2-4, defining the unique B-cell epitope 164HNFIQTI170, was located using peptide scanning. Comparing amino acid (aa) sequence revealed that this epitope is conserved in all reference ASFV strains from different regions of China, including the highly pathogenic strain Georgia 2007/1 (NC_044959.2) that is widely distributed. It is also exposed to the surface of the p30 protein, suggesting that it could be an important B-cell epitope. Our study may serve as a basis for the development of serological diagnostic methods and subunit vaccines.

A candidate nanoparticle vaccine comprised of multiple epitopes of the African swine fever virus elicits a robust immune response.

The African swine fever (ASF) pandemics pose a significant threat to the global swine industry, and the development of safe and effective vaccines is a daunting but necessary challenge. The level and persistence of immunity are very important for the effectiveness of the vaccine. Targeting antigens to antigen presenting cells (APCs) can greatly enhance immunogenicity. In this study, we developed a self-assembled nano-ASFV vaccine candidate (NanoFVax) targeting DCs, by covalently coupling the self-assembled 24-mer ferritin with the dominant B and T cell epitopes of the highly immunogenic ASFV antigen (p72, CD2v, pB602L and p30) and fused with the chemokine receptor XCL1 (a DC targeting molecule) through the SpyTag/SpyCatcher protein ligase system. Compared to monomeric protein, the nanoparticle vaccines can induce a more robust T-cell response, and the high-level antibody response against ASFV can last for more than 231 days. Therefore, the NanoFVax is a novel and promising vaccine candidate for ASFV.

Establishment of a Dual-Antigen Indirect ELISA Based on p30 and pB602L to Detect Antibodies against African Swine Fever Virus.

African swine fever (ASF) is an acute, virulent, and highly fatal infectious disease caused by the African swine fever virus (ASFV). There is no effective vaccine or diagnostic method to prevent and control this disease currently, which highlights the significance of ASF early detection. In this study, we chose an early antigen and a late-expressed antigen to co-detect the target antibody, which not only helps in early detection but also improves accuracy and sensitivity. CP204L and B602L were successfully expressed as soluble proteins in an Escherichia coli vector system. By optimizing various conditions, a dual-antigen indirect ELISA for ASFV antibodies was established. The assay was non-cross-reactive with antibodies against the porcine reproductive and respiratory syndrome virus, classical swine fever virus, porcine circovirus type 2, and pseudorabies virus. The maximum serum dilution for detection of ASFV-positive sera was 1:1600. The intra-batch reproducibility coefficient of variation was <5% and the inter-batch reproducibility coefficient of variation was <10%. Compared with commercial kits, the dual-antigen indirect ELISA had good detection performance. In conclusion, we established a detection method with low cost, streamlined production process, and fewer instruments. It provides a new method for the serological diagnosis of ASF.

Nomogram for predicting survival in patients with advanced hepatocellular carcinoma treated with PD-1 inhibitors: incorporating pre-treatment and post-treatment clinical parameters.

BACKGROUND: Immunotherapy has transformed cancer treatment patterns for advanced hepatocellular carcinoma (aHCC) in recent years. Therefore, the identification of predictive biomarkers has important clinical implications. METHODS: We collected medical records from 117 aHCC patients treated with anti-PD-1 antibody. Kaplan-Meier analysis and Cox proportional hazard regression were used to evaluate the association between peripheral blood biomarkers and overall survival (OS) and progression-free survival (PFS). Finally, the prognostic nomogram was constructed. RESULTS: The mPFS and mOS were 7.0 months and 18.7 months, respectively. According to Kaplan-Meier analysis and Cox regression analysis, we regarded the treatment regimen (p = 0.020), hemoglobin (Hb) at 6-week (p = 0.042), neutrophil-to-lymphocyte ratio (NLR) at 6-week (p < 0.001), system immune inflammation index (SII) at 6-week (p = 0.125) as predictors of PFS, and alpha fetoprotein (AFP) (p = 0.035), platelet-to-lymphocyte ratio (PLR) (p = 0.012), Hb at 6-week (p = 0.010) and NLR at 6-week (p = 0.020) as predictors of OS. Furthermore, the results suggest that the OS and PFS nomogram model were in agreement with actual observations. CONCLUSION: Biomarkers in peripheral blood can predict the prognosis of patients with aHCC treated with anti-PD-1 antibody. The development of nomogram models can help us to screen potential patients who can benefit from immunotherapy.

Immune checkpoint inhibitors alone or in combination with chemotherapy for treatment of advanced non-small cell lung cancer after first-line platinum-based chemotherapy: A propensity score matching analysis.

Background: Immune checkpoint inhibitors (ICIs) have changed the treatment landscape of several cancer types. However, data are lacking with regard to the clinical responsiveness of ICIs in patients with advanced non-small cell lung cancer (NSCLC) after standard first-line chemotherapy. Therefore, we aimed to evaluate the clinical efficacy of ICI alone or in combination with chemotherapy for patients with advanced NSCLC after first-line platinum-based chemotherapy. Methods: We retrospectively collected patients with confirmed advanced NSCLC who underwent ICI monotherapy or ICI plus chemotherapy after first-line platinum-based chemotherapy between January 2018 and December 2020. A propensity score matching analysis was used to balance baseline characteristics between the two treatment groups. Kaplan-Meier methods and multivariable Cox regressions were used for survival analyses. Results: Among 832 eligible patients, 222 received ICI monotherapy and 610 received ICI plus chemotherapy. The median overall survival (OS) of patients who received ICI plus chemotherapy was 16.0 months compared with 13.1 months in patients who received ICI monotherapy (HR: 0.64, 95% CI: 0.49-0.85, P = 0.002). After 1:1 propensity score matching, all baseline characteristics were well-balanced between the two treatment groups. Patients who received ICI plus chemotherapy had significantly longer OS than those who received ICI monotherapy (NR vs. 13.1 months, HR: 0.50, 95% CI: 0.34-0.71, P < 0.001). Meanwhile, the median time to treatment discontinuation was 4.4 months in the ICI-chemo group and 3.5 months in the ICI-mono group (HR: 0.72, 95% CI: 0.58-0.89, P = 0.002). The multivariate analysis indicated that treatment regimen was an independent prognostic factor for OS (HR: 0.488, 95% CI: 0.337-0.707, P < 0.001). Moreover, a nomogram that integrated both treatment regimens and clinicopathological factors was created for survival prediction. Conclusion: Our study indicated that patients with advanced NSCLC who received ICI plus chemotherapy after first-line platinum-based chemotherapy tended to have longer OS than those who received ICI monotherapy. The multivariate analysis showed that treatment regimen was an independent prognostic factor for OS. Future prospective studies are needed to confirm these findings.