AIM: To purify and refold the inclusion body of a human anti-HBsAg scFv with a 6?His tag, and to determine the affinity constant of the purified recombinant product.METHODS: Solubilizing in buffers containing urea or guanidine hydrochloride (GuHCl), the inclusion body was purified by IMAC, and then refolded by dialysis against urea or GuHCl, at the same time, Ni 2+ charged chelate column was utilized for in situ refolding. The affinity constant of the refolded scFv, polished by immune-affinity chromatography, was determined by non-competitive ELISA. RESULTS: The refolded scFv with highest specific bioactivity was produced by dialysis against GuHCl. Under this condition, the recovery of target protein reached (61.08?1 45)%. The affinity constant of the polished scFv was confirmed to be(2.30?0.32) ?10 7 L/mol. CONCLUSION: The inclusion body studied in this paper can be refolded efficiently under optimal dialysis condition in vitro . The antigen-binding property of this recombinant scFv is not affected by the purification tag fused to the N terminal of the protein.

Objective:In general, patients with seropositive rheumatoid arthritis (RA) are considered to show an aggressive disease course. However, the relationship between the two subgroups in disease severity is controversial. Our study is aimed to compare the clinical characteristics and prognosis of double-seropositive and seronegative RA in China through a real-world large scale study.Methods:RA patients who met the 1987 American College of Rheumatology (ACR) classification criteria or the 2010 ACR/European Anti-Rheumatism Alliance RA classification criteria, and who attended the 10 hospitals across the country from September 2015 to January 2020, were enrolled. According to the serological status, patients were divided into 4 subgroups [rheumatoid factor (RF)(-) anti-cyclic citrullinated peptide (CCP) antibody (-), RF(+), RF(+) anti-CCP antibody(+), anti-CCP antibody(+)] and compared the disease characteristics and treatment response. One-way analysis of variance was used for measurement data that conformed to normal distribution, Kruskal-Wallis H test was used for measurement data that did not conform to normal distribution; paired t test was used for comparison before and after treatment within the group if the data was normally distributed else paired rank sum test was used; χ2 test was used for count data. Results:① A total of 2 461 patients were included, including 1 813 RF(+) anti-CCP antibody(+) patients (73.67%), 129 RF(+) patients (5.24%), 245 RF(-) anti-CCP antibody(-) patients (9.96%), 74 anti-CCP antibody(+) patients (11.13%). ② Regardless of the CCP status, RF(+) patients had an early age of onset [RF(-) anti-CCP antibody(-) (51±14) years old, anti-CCP antibody(+) (50±15) years old, RF(+) anti-CCP antibody(+) (48±14) years old, RF(+)(48±13) years old, F=3.003, P=0.029], longer disease duration [RF(-) anti-CCP antibody(-) 50 (20, 126) months, anti-CCP antibody(+) 60(24, 150) months, RF(+) anti-CCP antibody(+) 89(35, 179) months, RF(+) 83(25, 160) months, H=22.001, P<0.01], more joint swelling counts (SJC) [RF(-) anti-CCP antibody(-) 2(0, 6), Anti-CCP antibody(+) 2(0, 5), RF(+) anti-CCP antibody(+) 2(0, 7), RF(+) 2(0, 6), H=8.939, P=0.03] and tender joint counts (TJC) [RF(-) anti-CCP antibody(-) 3(0, 8), anti-CCP antibody(+) 2(0, 6), RF(+) anti-CCP antibody(+) 3(1, 9), RF(+) 2(0, 8), H=11.341, P=0.01] and the morning stiff time was longer [RF(-) anti-CCP antibody(-) 30(0, 60) min, anti-CCP antibody(+) 20(0, 60) min, RF(+) anti-CCP antibody(+) 30(10, 60) min, RF(+) 30(10, 60) min, H=13.32, P<0.01]; ESR [RF(-) anti-CCP antibody(-) 17(9, 38) mm/1 h, anti-CCP antibody(+) 20(10, 35) mm/1 h, RF(+) anti-CCP antibody(+) 26(14, 45) mm/1 h, RF(+) 28(14, 50) mm/1 h, H=37.084, P<0.01] and CRP [RF(-) anti-CCP antibody(-) 2.3 (0.8, 15.9) mm/L, Anti-CCP antibody(+) 2.7(0.7, 12.1) mm/L, RF(+) anti-CCP antibody(+) 5.2(1.3, 17.2) mm/L, RF (+) 5.2(0.9, 16.2) mm/L, H=22.141, P<0.01] of the RF(+)patients were significantly higher than RF(-) patients, and RF(+) patients had higher disease severity(DAS28-ESR) [RF(-) anti-CCP antibody(-) (4.0±1.8), anti-CCP antibody(+) (3.8±1.6), RF(+) anti-CCP antibody(+) (4.3±1.8), RF(+) (4.1±1.7), F=7.269, P<0.01]. ③ The RF(+) anti-CCP antibody(+) patients were divided into 4 subgroups, and it was found that RF-H anti-CCP antibody-L patients had higher disease severity [RF-H anti-CCP antibody-H 4.3(2.9, 5.6), RF-L anti-CCP antibody-L 4.5(3.0, 5.7), RF-H anti-CCP antibody-L 4.9(3.1, 6.2), RF-L anti-CCP antibody-H 2.8(1.8, 3.9), H=20.374, P<0.01]. ④ After 3-month follow up, the clinical characteristics of the four groups were improved, but there was no significant difference in the improvement of the four groups, indicating that the RF and anti-CCP antibody status did not affect the remission within 3 months. Conclusion:Among RA patients, the disease activity of RA patients is closely related to RF and the RF(+) patients have more severe disease than RF(-) patients. Patients with higher RF titer also have more severe disease than that of patients with low RF titer. After 3 months of medication treatment, the antibody status does not affect the disease remission rate.