Rapid Generation of Recombinant Flaviviruses Using Circular Polymerase Extension Reaction.

The genus Flavivirus is a group of arthropod-borne single-stranded RNA viruses, which includes important human and animal pathogens such as Japanese encephalitis virus (JEV), Zika virus (ZIKV), Dengue virus (DENV), yellow fever virus (YFV), West Nile virus (WNV), and Tick-borne encephalitis virus (TBEV). Reverse genetics has been a useful tool for understanding biological properties and the pathogenesis of flaviviruses. However, the conventional construction of full-length infectious clones for flavivirus is time-consuming and difficult due to the toxicity of the flavivirus genome to E. coli. Herein, we applied a simple, rapid, and bacterium-free circular polymerase extension reaction (CPER) method to synthesize recombinant flaviviruses in vertebrate cells as well as insect cells. We started with the de novo synthesis of the JEV vaccine strain SA-14-14-2 in Vero cells using CPER, and then modified the CPER method to recover insect-specific flaviviruses (ISFs) in mosquito C6/36 cells. Chimeric Zika virus (ChinZIKV) based on the Chaoyang virus (CYV) backbone and the Culex flavivirus reporter virus expressing green fluorescent protein (CxFV-GFP) were subsequently rescued in C6/36 cells. CPER is a simple method for the rapid generation of flaviviruses and other potential RNA viruses. A CPER-based recovery system for flaviviruses of different host ranges was established, which would facilitate the development of countermeasures against flavivirus outbreaks in the future.

Evaluation of Zika virus DNA vaccines based on NS1 and domain III of E.

BACKGROUND: A large-scale outbreak of Zika virus (ZIKV) has occurred in Brazil and other South American countries, and has rapidly spread to 60 countries and regions worldwide since 2015, but no approved anti-ZIKV vaccines are available as of 2021. METHODS: We developed four types of anti-ZIKV DNA vaccine candidates: VPC-NS1, VPC-prME, VPC-prME-NS1, and VPC-EIII-NS1. They were developed against the structural proteins prM and E, and non-structural protein 1 (NS1) of ZIKV using the mammalian cell expression vector pcDNA3.1(+) as the backbone. For immunization, we intramuscularly injected mice with each vaccine candidate (n = 12 to 15 per group) on day 0 and day 14, with mice injected with phosphate-buffered saline (PBS) and pcDNA3.1(+) backbone vector as controls. On day 7, 21, and 35 after initial immunization, the effect of DNA vaccines was evaluated by ZIKV-specific humoral immunity determined by enzyme-linked immunosorbent assay (ELISA), ZIKV-specific T cell immunity determined by intracellular cytokine staining by flow cytometry and serum neutralization capacity determined by plaque reduction neutralization test (PRNT50) assay. RESULTS: The sequencing results showed that DNA vaccine vectors were successfully constructed. Western blotting and immunofluorescence results demonstrated the successful expression of immunogens carried by the DNA vaccines. On day 21 and 35 after the initial immunization, the levels of serum total immunoglobulin (Ig)G in all vaccine-given groups were slightly higher (approximately 1.5- to 2-fold) than those in the control groups. By contrast, ZIKV-specific IgG levels of all vaccine-given groups were significantly higher (approximately 10- to 1000- fold) than those of the control groups. The PRNT50 assay showed that the average serum dilution factors for neutralizing half ZIKV virions from vaccine-given groups were at least 32-fold (highest, 93-fold), while the sera from control group showed no protection. For cellular immunity, the proportions of CD11b+ myeloid cells, CD19+ B lymphocytes and CD3+ T lymphocytes in the mouse spleens as well as the percentages of CD4+ and CD8+ subsets of T cell were not changed 35 days after initial immunization. By contrast, the proportions of ZIKV-specific CD4+T cell and CD8+T cell in all vaccine-given groups were 2- to 10-folds and 2- to 30-fold than those in the control groups, respectively. CONCLUSION: All four DNA vaccines designed for the ZIKV induced neutralizing IgGs and cellular immune responses against ZIKV. Particularly, VPC-EIII-NS1 induced high level of humoral response comparable to the vaccine candidate containing prM, E and NS1 polyprotein, suggesting a potent reduced ADE effect and reserved neutralizing activity. Our findings may provide guidance for improving safety of anti-ZIKV vaccines in the future.

Increased yield of AP-3 by inactivation of asm25 in Actinosynnema pretiosum ssp. auranticum ATCC 31565.

Asamitocins are maytansinoids produced by Actinosynnema pretiosum ssp. auranticum ATCC 31565 (A. pretiosum ATCC 31565), which have a structure similar to that of maytansine, therefore serving as a precursor of maytansine in the development of antibody-drug conjugates (ADCs). Currently, there are more than 20 known derivatives of ansamitocins, among which ansamitocin P-3 (AP-3) exhibits the highest antitumor activity. Despite its importance, the application of AP-3 is restricted by low yield, likely due to a substrate competition mechanism underlying the synthesis pathways of AP-3 and its byproducts. Given that N-demethylansamitocin P-3, the precursor of AP-3, is regulated by asm25 and asm10 to synthesize AGP-3 and AP-3, respectively, asm25 is predicted to be an inhibitory gene for AP-3 production. In this study, we inactivated asm25 in A. pretiosum ATCC 31565 by CRISPR-Cas9-guided gene editing. asm25 depletion resulted in a more than 2-fold increase in AP-3 yield. Surprisingly, the addition of isobutanol further improved AP-3 yield in the asm25 knockout strain by more than 6 times; in contrast, only a 1.53-fold increase was found in the WT strain under the parallel condition. Thus, we uncovered an unknown function of asm25 in AP-3 yield and identified asm25 as a promising target to enhance the large-scale industrial production of AP-3.

[Effect of comprehensive intervention of schistosomiasis control in construction workers in Poyang Lake region].

After the implementation of the comprehensive schistosomiasis control measures centering on health education for 3 years, the awareness rate of schistosomiasis control increased by 96.56% in construction workers of Dechang highway construction engineering projects in Poyang Lake region, the number of workers adopting preventive measures increased significantly, and no schistosome infection occurred. It is suggested that the comprehensive measures focusing on health education, combined with environment depollution and public administration can prevent schistosome infection effectively among construction workers.