Screening and identification of B cell epitope of the nucleocapsid protein in SARS-CoV-2 using the monoclonal antibodies.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes the coronavirus disease (COVID-19). It is confirmed that nucleocapsid (N) protein is closely related to viral pathogenesis, modulation of host immune response, RNA transcription, and replication and virus packaging. Therefore, the N protein is a preponderant antigen target for virus detection. The codon-optimized N gene was designed according to the encoding characteristics of insect cells and inserted into pFastBacTM1 vector with 6 × His-tag-fused N protein for expression in insect sf21 cells. Six anti-N mAbs (4G3, 5B3, 12B6, 18C7-A2, 21H10-A3, 21H10-E9) were prepared by recombinant N protein. The mAbs showed high titers, antibody affinity, and reactivity with the SARS-CoV-2 N protein. Then, fourteen overlapped peptides that covered the intact N protein were synthesized (N1-N14). Peptide N14 was identified as the main linear B-cell epitope region via peptide-ELISA and dot-blot assay, and this region was truncated gradually until mapping the peptide 401-DFSKQLQQ-408. Simultaneously, compared with the sequence of variants of concern (VOCs) and variants of interest (VOIs) strains among the several countries, epitope 401-DFSKQLQQ-408 is very conservative among them. The findings provide new guidance for the design and detection of COVID-19 targets. KEY POINTS: • The N protein was optimized according to the insect cell codon preference and was highly expressed. • The monoclonal antibodies prepared in this study were shown high antibody titers and high affinity. • Monoclonal antibodies were used to map the epitope 401-408 amino acids of N protein for the first time in this study.

Primary antibiotic resistance in Helicobacter pylori in China: a systematic review and meta-analysis.

OBJECTIVES: The incidence of Helicobacter pylori (HP) is 25-50% in developed countries and 80% in developing countries, including 56.2% in China. However, antibiotic resistance of HP is a threat to HP control. The purpose of this study was to comprehensively evaluate primary drug resistance of HP in China. METHODS: The full text of reports of the primary antibiotic resistance prevalence of HP was obtained from multiple databases (PubMed, Web of Science, Evimed, Cochrane Library, and China National Knowledge Internet). Review Manager 5.2 was adopted for meta-analysis, sensitivity analysis, and bias analysis. The Newcastle-Ottawa Scale was used to assess the article quality. RESULTS: In total, 38804 HP samples from 22 trials were extracted. The results suggested that the overall prevalence of amoxicillin, clarithromycin, metronidazole, and levofloxacin resistance among HP in adults was as follows: mean difference (MD) = 1.35%, 95% confidence interval (CI) [1.03%, 1.68%]; MD = 23.76%, 95% CI [20.23%, 27.3%]; MD = 69.32%, 95% CI [64.85%, 73.8%]; and MD = 29.45%, 95% CI [4.90, 176.96], respectively. From the results of sensitivity and publication bias, we find that these results are robust and had little publication bias. CONCLUSION: Our research showed that in China, the prevalence of HP resistance to primary antibiotics warrants attention, especially with regard to metronidazole, levofloxacin, and clarithromycin.

Identification of a novel bluetongue virus 1 specific B cell epitope using monoclonal antibodies against the VP2 protein.

Bluetongue (BT) is a non-contact infectious disease caused by Bluetongue virus (BTV), which can be transmitted by vector insects such as Culicoides and Aedes mosquitoes. The BTV VP2 protein encoded by the L2 gene is located at the outermost layer of the virus particle, plays a key role on mediating the adsorption and entry of virus, and it is also a main antigenic protein widely used for vaccine development. In this study, the BTV1 VP2 gene was cloned into pFastBac™Dual vector, and expressed in insect Sf21 cells. Immunized mice with purified recombinant VP2 protein can induce higher levels of antibodies. Three anti BTV1 VP2 monoclonal antibodies (mAbs) were generated (17E9C6, 17E9C8, 17E9H12), and showed high specific reactivity with recombinant VP2 protein and inactivated BTV1 virus. Finally, a novel linear B-cell epitope 296-KEPAD-300 on recombinant VP2 protein was identified by using three mAbs react with a series of continue-truncated peptides. The results of this study may provide new information on the structure and function of BTV1 VP2 protein and lay a foundation for the development of BTV1 diagnostic and prophylactic methods.