Objective:To construct the rpoN gene knockout strain (Δ rpoN) and the complemented strain (CΔ rpoN) of Vibrio vulnificus ( V. vulnificus), and investigate the role of the rpoN gene in regulating bacterial motility and biofilm formation. Methods:The Δ rpoN strain of V. vulnificus was constructed using homologous recombination. Bacterial motility was assessed via swimming assays, and flagellar morphology was observed by transmission electron microscopy. Biofilm formation capacity was evaluated using crystal violet and Congo red staining assays, as well as colony morphology analysis. Real-time quantitative RT-PCR (qRT-PCR) was used to detect mRNA levels of target genes associated with flagellar synthesis and biofilm formation in Δ rpoN and the wild-type strains. Results:The V. vulnificus genome harbored a single rpoN gene, encoding a protein with high amino acid sequence similarity to RpoN homologs in other bacterial species. The Δ rpoN strain was successfully constructed. Compared with the wild-type strain, the Δ rpoN strain exhibited complete loss of motility on soft agar plates, absence of flagellar, and downregulated mRNA levels of flagellar synthesis-related genes. Conclusions:In V. vulnificus, RpoN regulates flagellar assembly by modulating the expression of flagellar synthesis genes, thereby controlling bacterial motility and biofilm formation.

Objective:To investigate the genomic characteristics of a clinical strain of respiratory syncytial virus (RSV) causing a severe pneumonia outbreak in a maternity center in a city in northern China in 2021.Methods:The whole genome sequence of RSV from a clinical sample obtained from a child with respiratory failure and heart failure was determined and analyzed using Sanger sequencing method. Sequence splicing and alignment were performed using bioinformatics software such as Sequencher 5.0, MEGA 7.0, and BioEdit 7.0. Besides, its phylogenetic relationship with the representative strains of RSV-B genotype, amino acid variations, and glycosylation sites were analyzed.Results:The genome of the clinical strain (named RSV/SY/2021) was 15 242 bp in length, consisting of 10 genes encoding 11 proteins, and possessed all the structural features of RSV. Phylogenetic analysis showed that the RSV/SY/2021 strain belonged to BA9 genotype and had the closest genetic relationship with the 2018 Netherlands epidemic strain MZ515558/Netherlands/2018. The termination codon mutation at the end of its attachment glycoprotein (G) gene resulted in the elongation of seven amino acids "Q-R-L-Q-S-Y-A" and the introduction of two additional O-glycosylation sites.Conclusions:This study suggests that RSV BA9 genotype may cause severe clinical symptoms, and clarifies the genome-wide characteristics and nucleotide/amino acid variation patterns of the RSV/SY/2021 strain. These findings enrich both national and global genome databases of RSV, and provide crucial etiological data for tracking RSV transmission, nucleic acid testing, and the development and evaluation of vaccines, antibodies and drugs against RSV.

Objective:To obtain fucose-free anti-West Nile virus nonstructural protein 1 (NS1) antibody and evaluate its antibody-dependent cell-mediated cytotoxicity (ADCC).Methods:The guanosine diphosphate-fucose transporter SLC35C1 in CHO cells was knocked out using CRISPR/Cas9 gene editing technology to obtain the fucose-free cell line CHO SLC35C1 -/-. CHO SLC35C1 -/- cells were used to produce fucose-free anti-West Nile virus NS1 antibodies. The binding abilities of the antibodies to the target antigen of West Nile virus NS1 protein and the human high-affinity IgG Fc receptor hFcγRⅠ (hCD64) were detected by ELISA and flow cytometry, respectively. The ADCC activity of the antibodies was detected by ADCC reporter gene assay. One-way analysis of variance was used for statistical analysis. Results:CHO SLC35C1 -/- cells expressed green fluorescent protein but not Lens culinaris agglutinin. The anti-West Nile virus NS1 antibodies produced by CHO SLC35C1 -/- cells with a fucose content of 0.22% could bind to West Nile virus NS1 protein in a concentration-dependent manner. Compared with the wild-type antibodies, the fucose-free anti-West Nile virus NS1 antibodies showed a stronger binding ability to hFcγRⅠ(hCD64), as indicated by a significant increase in fluorescence intensity. The ADCC reporter gene assay showed that the fucose-free anti-West Nile virus NS1 antibodies had increased activity as compared with the wild-type antibodies ( P<0.001). Conclusion:The fucose-free anti-West Nile virus NS1 antibodies may be used to protect against West Nile virus infection.

Objective:To investigate the effect of co-colonization with Helicobacter hepaticus ( Hh) and Citrobacter rodentium ( Cr) on CD4 + T cell differentiation. Methods:A HH7-2tg mouse model was employed in this study. Approaches including antibiotic treatment, bacterial colonization, and dextran sulfate sodium (DSS)-induced inflammation were combined to study the impact of specific microbiota on CD4 + T cell differentiation. Flow cytometry was used to analyze the changes in CD4 + T cell subsets in mouse intestinal tissues. Differences between groups were analyzed using the unpaired Mann-Whitney U test (two-tailed). Results:Compared with mice with antibiotic-depleted gut microbiota, co-colonization with Hh and the gut microbiota significantly increased both the proportion and the absolute number of intestinal RORγt + T-bet + Foxp3 + CD4 + T cells (both P<0.01). Co-colonization with Hh and Cr induced significantly higher proportion and absolute number of RORγt + T-bet + Foxp3 + CD4 + T cells as compared with colonization with either Hh or Cr alone following antibiotic treatment (all P<0.05). Under DSS-induced inflammatory conditions, Hh failed to effectively induce RORγt + T-bet + Foxp3 + CD4 + T cells, suggesting that Cr metabolites or inflammatory signals were essential for the induction of this specific cell population. Recombinant Cr strains expressing Hh antigen did not exhibit the induction effect of co-colonization with both wild-type strains in terms of induction efficiency. The induction of this specific T cell population was asynchronous with that of other CD4 + T cell subsets, suggesting the uniqueness of their regulatory mechanism. Conclusion:Co-colonization with Hh and Cr induces RORγt + T-bet + Foxp3 + CD4 + T cells, and thus can serve as a viable in vivo induction model for studying RORγt + T-bet + Foxp3 + CD4 + T cells. This study provides reference for further research into the immune functions and regulatory mechanisms of this unique CD4 + T cell subset.

Objective:To investigate the role of the CD38/p53/ME1 axis in regulating T cell mitochondrial function and senescence during HIV infection.Methods:The expression of CD38 on T cells was examined in HIV-infected individuals receiving antiretroviral therapy(ART), untreated HIV-infected individuals, and HIV-negative healthy controls. Flow cytometry was used to compare senescence markers and mitochondrial function between CD38 + and CD38 - T cells. Malic enzyme 1(ME1) mRNA levels were measured by qRT-PCR in T cells treated with the CD38 inhibitor 78c. Mitochondrial function and senescence were assessed in T cells treated with an ME1 inhibitor. The regulatory mechanism of CD38-mediated ME1 downregulation was further explored. Results:Compared to healthy controls, T cells from HIV-infected individuals exhibited significantly elevated CD38 expression, which persisted despite ART. CD38 + T cells showed increased senescence (CD28 -CD57 + subset) and mitochondrial dysfunction[depolarization and reactive oxygen species(ROS) accumulation]. CD38 inhibition upregulated ME1 mRNA level ( P<0.05). ME1 suppression led to mitochondrial impairment (reduced membrane potential and elevated ROS) and senescence in T cells. Mechanistically, CD38 depletion increased NAD + levels and SIRT1 activity, while SIRT1/p53 inhibition rescued ME1 expression, suggesting CD38 regulates ME1 via the NAD + /SIRT1/p53 axis. Conclusions:The CD38/p53/ME1 axis drives T cell senescence in HIV infection by disrupting mitochondrial function. Targeting this pathway may ameliorate CD38-associated T cell dysfunction and immune aging.

Objective:To analyze the epidemiological and clinical characteristics of Mycoplasma pneumoniae ( Mp) infection among hospitalized children with acute respiratory tract infections (ARTIs) in a single center in Beijing and provide reference for the prevention and treatment of Mp infection. Methods:Nasopharyngeal aspirate (NPA) samples of hospitalized children with ARTIs were collected from Beijing Friendship Hospital during two periods: from April 2018 to March 2019 and from September 2020 to August 2022. qPCR was used to detect Mp nucleic acids, and for Mp-positive samples, the mixed infections with 15 common respiratory viruses were detected. Statistical analysis was conducted using Chi-square test, Fisher′s exact test, and independent samples t-test. Results:From April 2018 to March 2019, 1 572 NPA samples were collected, with 104 positive for Mp (6.62%). From September 2020 to August 2022, 622 samples were collected, with 22 Mp-positive samples (3.54%). There was statistically significant difference in the positive rates between the two time periods ( P<0.05). From April 2018 to March 2019, the positive rate of Mp was higher in children aged ≥5 years than in those <5 years [13.03% (46/353) vs 4.76% (58/1 219), P<0.05]; the positive rates in summer (9.54%, 35/367) and autumn (7.93%, 33/416) were higher than those in spring (3.03%, 11/363) and winter (5.87%, 25/426), with statistically significant differences ( P<0.05); co-infections with other respiratory viruses were detected in 42 out of the 104 Mp-positive cases (40.38%), primarily with human rhinovirus (35.71%, 15/42) or human coronavirus NL63 (19.05%, 8/42). From September 2020 to August 2022, Mp infections mainly occurred in children aged ≥5 years [72.73% (16/22)], and co-infections with other respiratory viruses were detected in four cases (18.18%, 4/22). The Mp-infected children were mainly diagnosed with pneumonia, and there was no significant difference in clinical symptoms between Mp-infected patients with or without viral coinfection. Conclusions:The positive rate of Mp among hospitalized children with ARTIs in Beijing from September 2020 to August 2022 is significantly lower than that observed from April 2018 to March 2019. Mp is an important cause of ARTIs in children, especially in patients aged ≥5 years. Mp infection is often accompanied by viral co-infections, with high incidence in summer and autumn.

Objective:To investigate the clinical data, drug resistance and treatment prognosis of Cryptococcus neoformans isolated from patients with acquired immunodeficiency syndrome(AIDS) in a hospital in Shanghai. Methods:The clinical data of AIDS patients with Cryptococcus neoformans infection in Shanghai Public Health Clinical Center from January 2014 to December 2023, and the drug sensitivity to 5 antifungal drugs in vitro, treatment and prognosis were retrospectively analyzed. Results:From January 2014 to December 2023, there were 295 AIDS patients with Cryptococcus neoformans infection in our hospital, with 255 males and 40 females. CD4 + T lymphocyte counts ≤100 cells/μl were detected in 251 patients. A total of 384 strains of Cryptococcus neoformans were isolated from the 295 patients, with the highest detection rate in cerebrospinal fluid samples (65.9%, 253/384), followed by blood samples (29.4%, 113/384). The sensitivity of 384 strains of Cryptococcus neoformans to 5-fluorocytosine was the highest (98.5%, 379/384), followed by fluconazole (95.6%, 367/384) and amphotericin B (95.3%, 366/384). After treatment against cryptococcal infection, 252 patients (86.0%, 252/293) were discharged and 20 patients (6.8%, 20/293) died. The other 2 cases were not treated for cryptococcal infection. Conclusions:As Cryptococcus neoformans is an important pathogen of AIDS patients, clinicians should actively carry out laboratory examination of Cryptococcus and rational drug use according to the results of drug sensitivity test, while alert to the occurrence of drug resistance.

Objective:To identify and trace the origin of the Francisella tularensis subsp. novicida strain SJCS-979 isolated from the blood of a patient, so as to provide a reference for the traceability investigation of such infection events. Methods:Hot spring water samples that the patient had recently bathed in were collected to culture the causative agent, combined with the pathogenic characteristics and the patient′s activity before the bloodstream infection. The water samples were concentrated, acid-treated, and then the isolation of the causative agent was performed, following the method for Legionella detection in circulating cooling water. Suspected strains detected from the hot spring water were subjected to classical phenotypic identification, API ZYM and API NH strips tests, drug sensitivity testing, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) identification, and the obtained data were compared with those of strain SJCS-979 isolated from the patient′s blood. A phylogenetic tree was constructed based on genomic analysis to determine the taxonomic status of strain SJCS-979 and related strains. Epidemiological data of Francisella tularensis subsp. novicida were collected and analyzed by integrating the global genetic and genomic data on GenBank database. Core single nucleotide polymorphism(SNP) comparisons were obtained using Snippy 3.2 software, and then an evolutionary tree was built to determine its population structure based on BAPS analysis. Results:Strain CC-2, isolated from the hot spring water, shared the same biochemical and drug sensitivity phenotype, and had a nearly consistent mass spectrometric profile with strain SJCS-979 isolated from the blood of a patient. Genomic phylogenetic tree analysis based on 120 core protein sequences showed that strains SJCS-979 and CC-2 fell on the same branch with known Francisella tularensis subsp. novicida strains. Bayesian genotyping showed that the global Francisella tularensis subsp. novicida strains with genomic data could be divided into six different sequence clusters. Strains SJCS-979 and CC-2 were located in the same taxonomic group with only 4 SNP differences, indicating that they might be the same clone. Conclusions:This study reports a case of bacteremia caused by Francisella tularensis subsp. novicida, and natural hot spring water may be the environmental source of this infection event.

Objective:To construct a VP8-mRNA vaccine using human rotavirus spike protein VP8 domain as the immunogen and analyze its immunogenicity in mice.Methods:The VP8-mRNA sequence was designed, optimized, and synthesized. The VP8 gene of rotavirus G1P[8] type was used to construct the plasmid pUC57-VP8-Kan-SapⅠ, which was then sequenced. The plasmid confirmed by sequencing was subjected to large-scale amplification and extraction, followed by linearization, in vitro transcription, and capping. The purified capped products were encapsulated with lipid nanoparticles using a microfluidic control apparatus. The encapsulated VP8-mRNA vaccine was administered intramuscularly to mice at 10, 15, and 20 μg. Serum samples were collected for antibody detection by ELISA. Cellular immune responses were detected by flow cytometry and ELISPOT. Statistical analysis was performed using one-way or two-way analysis of variance and Tukey-Kramer test. Results:The encapsulated VP8-mRNA vaccine was rounded and spherical, with a particle size of about 100 nm, a polymer dispersion index of 0.088, and an encapsulation rate of 92.3%. Two doses of VP8-mRNA vaccine immunization could induce a good immune response in mice. The level of IgG antibody induced after immunization in the 15 μg group was comparable to that of the 20 μg group, and there was no statistical difference ( P>0.05), but the antibody levels in the two groups were significantly higher than that in the 10 μg group ( P<0.000 1). VP8-mRNA vaccine could induce neutralizing antibodies against rotavirus G1 and G9 types. The highest level of neutralizing antibodies against rotavirus type G1 was observed in the 15 μg group, which was significantly higher than that in the 10 μg group ( P<0.05). All immunization groups exhibited good neutralizing ability against rotavirus G9 type. The results of ELISPOT showed that lymphocytes from mice in each vaccine group were able to secrete IFN-γ when stimulated with VP8 peptide. Flow cytometry showed that the proportions of CD8 + T cell subsets in the vaccine groups were higher than that in the control group. Conclusion:The VP8-mRNA vaccine has good immunogenicity in mice and can induce good humoral and T-cell immune responses.

Objective:To investigate the prevalence and genotype distribution of human papillomavirus (HPV) infection in the anorectal region among human immunodeficiency virus (HIV)-positive men who have sex with men (MSM) in Shenzhen, and explore the differences between HIV-positive and HIV-negative MSM populations, providing scientific evidence for HPV screening, vaccination, and related disease prevention.Methods:A total of 100 MSM recruited from the Department of Dermatovenerology of the Third People′s Hospital of Shenzhen between 2023 and 2024 were included. Questionnaire collected sociodemographic and clinical characteristics. Anorectal exfoliated cells were analyzed for HPV genotyping, and blood samples were tested for HIV antibodies and T lymphocyte subsets. Chi-square test was used to assess associations between qualitative variables. Results:Among 100 MSM, 58 were HIV-positive and 42 HIV-negative. The overall HPV infection rate was 93.10% (54/58) in HIV-positive MSM, with high-risk HPV at 79.31% (46/58) and low-risk HPV at 75.86% (44/58). The predominant genotypes were HPV6, 11, 16, 52, 18, 59, and 68. In HIV-negative MSM, HPV infection rate was 95.24% (40/42), with high-risk HPV at 57.14% (24/42) and low-risk HPV at 92.50% (37/40), dominated by HPV6, 11, 16, 51 and 52. HIV-positive MSM showed significantly higher infection rates of high-risk HPV16/18 ( P=0.032), HPV58 ( P=0.020), HPV59 ( P=0.031), and HPV68 ( P=0.007) compared to HIV-negative MSM. The maximum number of concurrent HPV infections was 12 in HIV-positive MSM versus 4 in HIV-negative MSM. Multivariate analysis revealed that HIV-positive MSM with CD4/CD8 ratio≤0.9 had significantly higher HPV positivity ( P<0.05). Conclusions:HIV-positive MSM exhibit elevated rates of high-risk and multiple HPV infections, closely associated with immune dysfunction. Strengthened HPV screening, vaccination, and immune status management are critical for preventing HPV-related malignancies in the population.