Objective:To investigate the value of bone marrow plasma cell morphology in the diagnosis and prognosis of plasma cell myeloma (PCM).Method:Observational study.Collect the bone marrow morphology image reports and corresponding monoclonal protein (M protein) identification results of 1071 patients [629 males and 442 females, Median age 62 (29, 93) years] diagnosed with PCM in the outpatient and inpatient departments of Beijing Chaoyang Hospital affiliated to Capital Medical University from January 1, 2017 to February 28, 2022. Combined with Durie‐Salmon(DS) and International Staging System (ISS) of 427 patients diagnosed with PCM and overall survival time (OS) of 436, summarize the relevant plasma cell morphological characteristics. Statistical methods include chi-square test, Kruskal-Walls test, Spearman correlation analysis and Kaplan-Meier survival analysis.Result:The bone marrow morphology reports showed that the typical morphological features of peripheral blood in 573 patients with PCM included plasma cells (40.84%), immature granulocytes (30.89%), rouleaux formation in erythrocytes (68.94%) and nucleated red blood cells (8.55%). The types of bone marrow plasma cells in 1 071 patients diagnosed with PCM included 372 (34.73%) plasmablasts, 674 (62.93%)immature plasma cells, and 25 (2.34%) mature plasma cells. There is a significant positive correlation between the number of bone marrow plasma cells (proportion of nuclear cells) and the concentration of IgG and IgA type, from M protein identification( r=0.55, r=0.60, P<0.01). The proportions of M protein types in 1 071 patients with PCM from high to low were IgG (45.75%), IgA (23.53%), light chain (19.61%), IgD (4.76%), non-secretory (4.3%), biclonal (1.78%), IgE (0.19%), IgM (0.08%). The typical characteristics of the bone marrow plasma cells in various M protein types included clustered distribution, different cell body sizes, inclusions in the cytoplasm, binuclear, polynuclear, and abnormal nuclear. The proportion of plasmablasts in DSⅢ stage was 44.81% (164/366), higher than 21.57% (11/51) in DSⅡstage, and the difference was statistically significant(χ 2=10.2, P<0.05). There was a significant positive correlation between the number of bone marrow plasma cells and DS and ISS stages( r=0. 0.23, r=0.30, P<0.01). The median OS of the PCM patients in the plasmablasts group was significantly shorter than that in the immature plasma cells group [56.0 (23.0, 101.8) months vs 75.9(31.6, 121.5) months, HR=1.42,95% CI 1.05-1.91, P=0.02]. The median OS of the PCM patients in the group of tumor plasma cells burden≥37.5% was shorter than that of the tumor plasma cells burden<37.5% [75.9 (21.4, 122.6)months vs 81.3 (36.6, 108) months, HR=1.54,95% CI 1.14-2.07, P<0.05]. Conclusion:The morphology and tumor burden of bone marrow plasma cells provide an important basis for the diagnosis of PCM and can be used as a prognostic indicator for patients with PCM.

Objective: To investigate the genetic stability of virus seed H₂M₂₀K₇ (K7) of live attenuated Hepatitis A virus H2 strain (HAV, H2 strain) for production of hepatitis A (Live) vaccine, lyophilized after continuous passages. Methods: The virus seed K7 of H2 strain was proliferated and passaged in KMB₁₇ cells in cell factories. Viruses of different passages were harvested after continuous passages. Virus RNA was extracted and the complete genomes of different virus passages (K7, K10, K11, K13, K15, K18) were sequenced by using next-generation deep sequencing. The mutation rates of different passages were compared. The infectivity titers of different virus passages of H2 strain were tested by ELISA. Results: The mutation rates of complete genomes of different passages were low after continuous passages of master virus seed. The structure of gene was stable and non-synonymous mutation rate was lower than 0.57%. The mutation rate of 5 ’non-coding regions was lower than 0.1%. There was no significant mutation in VP1/2 A and 2C virulence site. The infectious titers of H2 strains of different passages were within 7.76-8.50 lgCCID₅₀/ml. No statistically significant difference was found in this study. Conclusions The gene structure of the master virus seed, working seed and different passages of H₂M₂₀K₇ after subculture was stable and the mutation rate was low. No significant mutation was found in 5’non-coding regions, and the critical virulence sites such as VP1/2 A, 2B and 2C showed attenuated characteristics with low mutation rate. Virulence of the virus did not changed. The H2 strain maintained stable viral infectivity and genetic stability and comply with the requirements as virus seed for vaccine manufacturing.