Objective:To screen broadly neutralizing antibodies in human immunodeficiency virus-1（HIV-1）chronically infected individuals and characterize their molecular features and to provide new strategies for rational vaccine development and antibody-based therapeutics.Methods:A total of 34 treatment-na?ve individuals with chronic HIV-1 infection were enrolled. Plasma antibody binding levels were measured against two HIV-1 envelope proteins. Single antigen-specific memory B cells were sorted from high-binding samples，and antibody variable region genes were amplified by PCR for paired expression. The monoclonal antibodies were evaluated for neutralizing activity using pseudovirus assays，and their structural features were analyzed by integrating AlphaFold 3 prediction with Discovery Studio molecular docking.Results:Plasma samples showed strong binding to DU422-GP140 and BG505-GP140. Eight monoclonal antibodies were isolated from two donors. Among them，antibodies 0919-A4，0919-A9 and 0808-A2 could cross-react with GP140 from HIV-1 subtypes AE，BC and B. The monoclonal antibody 0919-A9 demonstrated potent neutralizing activity against SF162（Tier 1）and CH181（Tier 2）pseudoviruses，with somatic hypermutation rates of 13.27%（heavy chain）and 15.58%（light chain）. Structural modeling revealed its specific targeting of the V1V2 region on GP120.Conclusion:The isolated antibody 0919-A9 effectively neutralizes Tier 2 pseudoviruses. Its high somatic mutation frequency and V1V2-targeting property underlie its neutralizing activity，providing both a promising candidate and mechanistic insights for HIV vaccine development and antibody-based therapeutic strategies.

Objective:To screen broadly neutralizing antibodies in human immunodeficiency virus-1（HIV-1）chronically infected individuals and characterize their molecular features and to provide new strategies for rational vaccine development and antibody-based therapeutics.Methods:A total of 34 treatment-na?ve individuals with chronic HIV-1 infection were enrolled. Plasma antibody binding levels were measured against two HIV-1 envelope proteins. Single antigen-specific memory B cells were sorted from high-binding samples，and antibody variable region genes were amplified by PCR for paired expression. The monoclonal antibodies were evaluated for neutralizing activity using pseudovirus assays，and their structural features were analyzed by integrating AlphaFold 3 prediction with Discovery Studio molecular docking.Results:Plasma samples showed strong binding to DU422-GP140 and BG505-GP140. Eight monoclonal antibodies were isolated from two donors. Among them，antibodies 0919-A4，0919-A9 and 0808-A2 could cross-react with GP140 from HIV-1 subtypes AE，BC and B. The monoclonal antibody 0919-A9 demonstrated potent neutralizing activity against SF162（Tier 1）and CH181（Tier 2）pseudoviruses，with somatic hypermutation rates of 13.27%（heavy chain）and 15.58%（light chain）. Structural modeling revealed its specific targeting of the V1V2 region on GP120.Conclusion:The isolated antibody 0919-A9 effectively neutralizes Tier 2 pseudoviruses. Its high somatic mutation frequency and V1V2-targeting property underlie its neutralizing activity，providing both a promising candidate and mechanistic insights for HIV vaccine development and antibody-based therapeutic strategies.

AIM: Given the biofilm formation abili- ty of different ST-type Klebsiella pneumoniae, our study was aimed at exploring the inhibitory and clearance of azithromycin combined with levofloxacin on the biofilm of Klebsiella pneumoniae of different ST-types and providing a new strategy for the prevention of biofilm formation in the treatment of post-infectious Klebsiella pneumoniae. METHODS: 9 strains of Klebsiella pneumoniae from all susceptibility groups, 19 strains of Klebsiella pneumoniae producing extended-spectrum β - lactamases (ESBLs), and 37 strains of Carbapenem-resistant Klebsiella pneumoniae (CRKP) were randomly collected from the samples of patients hospitalized in the First Affiliated Hospital of Wannan Medical College from August 2019 to November 2021. The isolates were identified using VITEK MS IVD KB V3.2 and VITEK 2-Compact 60. Multilocus sequence typing (MLST) was performed to analyze the homology of each strain; crystal violet staining was used for semi -quantitative detection of biofilm to compare the differences in biofilm formation ability between different ST-type Klebsiella pneumoniae. Different ST-type strains were selected, and the partial inhibitory concentration index (FICI) was calculated by micro broth dilution method to judge the combination effect and select the optimal combination concentration; crystalline violet staining method was used to investigate the inhibition and clearance effect of azithromycin combined with levofloxacin on the biofilm of different ST-type Klebsiella pneumoniae; laser scanning confocal fluorescence microscopy was used to observe the structural changes of the biofilm of Klebsiella pneumoniae before and after the effect of the antibacterial drugs. RESULTS: MLST typing results showed that the sensitive group of Klebsiella pneumoniae strains had 8 sequences such as ST86, ST727, etc., the ESBLs group strains belonged to 14 sequence types such as ST15, ST37, ST11, etc., of which ST15 accounted for 26.32% (5 / 19). The CRKP group strains belonged to 9 sequence types such as ST11, ST15, ST656, etc., of which ST11 accounted for 48.65% (18/37), ST15 accounted for 27.03% (10/37); ST15 (ESBLs), ST11 (CRKP), ST15 (CRKP) type Klebsiella pneumoniae biofilms all reached maturity on the 5th day, the ST15 (ESBLs) group had a stronger ability to produce material to be membranous than the ST15 (CRKP) group. The ST11 (CRKP) group had a stronger ability to produce material to be membranous than the ST15 (CRKP) group (P<0.01); the results of azithromycin combined with levofloxacin drug sensitivity showed that it had an additive effect on different ST-type Klebsiella pneumoniae bacteria; in the inhibition of biofilm formation and clearance test, the 2×MIC azithromycin group and the combined concentration group had a stronger inhibition of biofilm formation of different ST-type Klebsiella pneumoniae bacteria, and the inhibitory ability of the combined group was better than that of the single-drug group, and the highest inhibition rate could reach 89.93%; the clearance effects were all combined drug group>azithromycin>levofloxacin, and the highest clearance rate was 44.79%. CONCLUSION: There are differences in biofilm formation ability between different ST-type Klebsiella pneumoniae, and azithromycin combined with levofloxacin has a better inhibitory effect on different ST-type Klebsiella pneumoniae biofilm, conbined application can be used in the treatment of biofilm infections early stage.