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ObjectivePrevious research has shown that human identical sequences of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) promote coronavirus disease 2019 (COVID-19) progression by upregulating hyaluronic acid (HA). However, the association of HA with mortality and long COVID in SARS-CoV-2 reinfection and first infection is unclear.MethodsPatients with COVID-19 at Beijing Ditan Hospital from September 2023 to November 2023 were consecutively enrolled. SARS-CoV-2 reinfections were matched 1:2 with first infections using a nearest neighbor propensity score matching algorithm. We compared the hospital outcomes between patients with COVID-19 reinfection and first infection. The association between HA levels and mortality and long COVID in the matched cohort was analyzed.ResultsThe reinfection rate among COVID-19 hospitalized patients was 25.4% (62 cases). After propensity score matching, we found that reinfection was associated with a better clinical course and prognosis, including lower levels of C-reactive protein and erythrocyte sedimentation rate, fewer cases of bilateral lung infiltration and respiratory failure, and shorter viral clearance time and duration of symptoms (p 0.05).ConclusionSerum HA may serve as a novel biomarker for predicting COVID-19 mortality in patients with SARS-CoV-2 reinfection and first infection. However, HA levels may not be associated with long COVID.

IntroductionSeasonal influenza A H3N2 viruses are constantly changing, reducing the effectiveness of existing vaccines. As a result, the World Health Organization (WHO) needs to frequently update the vaccine strains to match the antigenicity of emerged H3N2 variants. Traditional assessments of antigenicity rely on serological methods, which are both labor-intensive and time-consuming. Although numerous computational models aim to simplify antigenicity determination, they either lack a robust quantitative linkage between antigenicity and viral sequences or focus restrictively on selected features.MethodsHere, we propose a novel computational method to predict antigenic distances using multiple features, including not only viral sequence attributes but also integrating four distinct categories of features that significantly affect viral antigenicity in sequences.ResultsThis method exhibits low error in virus antigenicity prediction and achieves superior accuracy in discerning antigenic drift. Utilizing this method, we investigated the evolution process of the H3N2 influenza viruses and identified a total of 21 major antigenic clusters from 1968 to 2022.DiscussionInterestingly, our predicted antigenic map aligns closely with the antigenic map generated with serological data. Thus, our method is a promising tool for detecting antigenic variants and guiding the selection of vaccine candidates.

To explore the relationship between the changes in the physiological period and the fecal microbial population of female rhesus monkeys by measuring microbial composition of fecal samples and the serum hormones. Blood and fecal samples were collected from six female adult rhesus monkeys during the menstrual period (MP), ovulation period (OP), and Luteal period (LP). Serum estradiol (E2) and progesterone (P) levels were determined by the chemiluminescence method and the stool samples were subjected to high-throughput 16S rRNA sequencing. The highest level of E2 and P secretions were during the MP, and LP, respectively. Stool samples produced valid sequences and the number of operational taxonomic unit/OTU was: 810056/3756 (MP), 845242/4159 (OP), 881560/3970 (LP). At the phylum level, the three groups of Firmicutes and Bacteroides accounted for > 95%. The dominant flora at the LP was Bacteroides (53.85%), the dominant flora at the MP and OP was Firmicutes, 64.08 and 56.53%, respectively. At the genus level, the dominant genus at the LP was Prevotella, the dominant genera at the MP were Prevotella, Oncococcus, Streptococcus, and Kurtella. The dominant genera at OP were Prevotella and Nocococcus. At the phylum level, P levels were negatively correlated to Firmicutes, Actinomycetes Actinobacteria, and Fibrobacteres, but positively correlated to Bacteroidetes. Likewise, E2 was positively correlated to Proteobacteria but negatively correlated to Euryarchaeota. At the genus level, P hormone showed a significant correlation with 16 bacterial species, and E2 was significantly correlated to seven bacterial species. Function prediction analysis revealed a high similarity between the MP and OP with six differentially functional genes (DFGs) between them and 11 DFGs between OP and LP (P < 0.05). Fecal microbiota types of female rhesus monkeys varied with different stages of the menstrual cycle, possibly related to changes in hormone levels.

Pseudomonas plecoglossicida is a facultative fish pathogen that possesses three distinct type VI secretion systems (named T6SS-1, T6SS-2, and T6SS-3). Our previous work indicated that only T6SS-2 of P. plecoglossicida mediates interbacterial competition. However, the antibacterial T6SS effectors and their functions are unclear. Here, we reported two T6SS effectors that mediate antibacterial activity. We first identified four putative antibacterial effectors (denoted as Txe1, Txe2, Txe3, and Txe4) and their cognate immunity proteins encoded in P. plecoglossicida strain XSDHY-P by analyzing the regions downstream of three vgrG genes. We showed that the growth of Escherichia coli cells expressing Txe1, Txe2, and Txe4 was inhibited, and these three effectors exhibited nuclease activity in vivo. The interbacterial competition assays with single- or multi-effector deletion mutants as attackers revealed that Txe1 was the predominant T6SS toxin of P. plecoglossicida strain XSDHY-P mediating the interbacterial killing. This work contributes to our understanding of bacterial effectors involved in the interbacterial competition.

Cronobacter sakazakii is an opportunistic Gram-negative pathogen that could cause meningitis and necrotizing enterocolitis. Several Gram-negative bacteria use the PmrA/PmrB system to sense and adapt to environmental change by resistance to cationic antimicrobial peptides of host immune systems. The PmrA/PmrB two-component system regulates several genes to modify LPS structure in the bacterial outer membrane. The role of PmrA/PmrB of C. sakazakii has been studied within the current study. The results suggest that PmrA/PmrB plays a crucial role in modifying LPS structure, cationic antimicrobial peptide susceptibility, cell membrane permeability and hydrophobicity, and invading macrophage.

Staphylococcus aureus (S. aureus) is an extremely halotolerant pathogenic bacterium with high osmotic stress tolerance, and it is frequently encountered in aquatic production and preservation. However, the mechanism underlying the extremely high osmotic stress tolerance of S. aureus remains unclear. In this study, the isobaric tags for relative and absolute quantification (iTRAQ) method was used to identify the differentially expressed proteins (DEPs) under different sodium chloride (NaCl) concentrations. Compared with the control group (0% NaCl), the 10 and 20% NaCl groups had 484 DEPs and 750 DEPs, respectively. Compared with the 10% NaCl group, the 20% NaCl group had 361 DEPs. Among the DEPs, proteins involved in fatty acid synthesis, proline/glycine betaine biosynthesis and transportation, stress tolerance, cell wall biosynthesis and the TCA cycle were upregulated, whereas proteins associated with biofilm formation and pathogenic infections were downregulated. The results obtained in this study indicate that under extremely high osmotic stress, modification of the cell membrane structure, increased biosynthesis and transportation of osmotic protectants, and redistribution of energy metabolism contribute to the osmotic stress tolerance of S. aureus, and the infectious ability of the bacteria may be limited. The aim of this study was to provide new insight into how S. aureus tolerates the high-salt conditions involved in aquatic production and preservation.

Staphylococcus aureus is one of the representative foodborne pathogens which forms biofilm. Antibiotics are widely applied in livestock husbandry to maintain animal health and productivity, thus contribute to the dissemination of antimicrobial resistant livestock and human pathogens, and pose a significant public health threat. Effect of antibiotic pressure on S. aureus biofilm formation, as well as the mechanism, remains unclear. In this study, the regulatory mechanism of low concentration of ampicillin on S. aureus biofilm formation was elucidated. The viability and biomass of biofilm with and without 1/4 MIC ampicillin treatment for 8 h were determined by XTT and crystal violet straining assays, respectively. Transcriptomics analysis on ampicillin-induced and non-ampicillin-induced biofilms were performed by RNA-sequencing, differentially expressed genes identification and annotation, GO functional and KEGG pathway enrichment. The viability and biomass of ampicillin-induced biofilm showed dramatical increase compared to the non-ampicillin-induced biofilm. A total of 530 differentially expressed genes (DEGs) with 167 and 363 genes showing up- and down-regulation, respectively, were obtained. Upon GO functional enrichment, 183, 252, and 21 specific GO terms in biological process, molecular function and cellular component were identified, respectively. Eight KEGG pathways including “Microbial metabolism in diverse environments”, “S. aureus infection”, and “Monobactam biosynthesis” were significantly enriched. In addition, “beta-lactam resistance” pathway was also highly enriched. In ampicillin-induced biofilm, the significant up-regulation of genes encoding multidrug resistance efflux pump AbcA, penicillin binding proteins PBP1, PBP1a/2, and PBP3, and antimicrobial resistance proteins VraF, VraG, Dlt, and Aur indicated the positive response of S. aureus to ampicillin. The up-regulation of genes encoding surface proteins ClfB, IsdA, and SasG and genes (cap5B and cap5C) which promote the adhesion of S. aureus in ampicillin induced biofilm might explain the enhanced biofilm viability and biomass.

Lactobacillus brevis is a major hop-resistance bacterium which poses significant challenge for the brewing industry, mainly due to the difficulty or incapability in detection by routine culturing methodology and its beer spoilage ability.This study aimed at investigating the VBNC state of a hop-resistance strain, L. brevis BM-LB13908. The culturable, total and viable numbers of L. brevis cells were calculated by MRS agar plate counting, acridine orange direct count (AODC) method and Live/Dead BacLight bacterial viability kit with fluorescence microscope. VBNC formation was induced by 189 ± 5.7 days under low-temperature storage or 27 ± 1.2 subcultures by continuous passage in beer, and VBNC cells induced by both strategies were recovered by adding catalase. In addition, insignificant difference in beer-spoilage ability was found in 3 states of L. brevis, including logarithmic growing, VBNC and recovered cells. This is the first study on the formation of VBNC state for L. brevis and beer-spoilage ability of both VBNC and recovered cells, which indicate L. brevis strain could cause beer spoilage without being detected by routine methodologies. The results derived from this study may support further study on L. brevis and other hop-resistance bacteria, and guidance on beer spoilage prevention and control, such as improvement for brewers on the microbiological quality control by using the improved culture method with catalase supplementation.

Multiple lines of evidence suggest that the gut microbiota plays vital roles in metabolic diseases such as hyperlipidemia. Previous studies have confirmed that krill oil can alleviate hyperlipidemia, but the underlying mechanism remains unclear. To discern whether krill oil changes the structure of the gut microbiota during the hyperlipidemia treatment, 72 mice were acclimatized with a standard chow diet for 2 weeks and then randomly allocated to receive a standard chow diet (control group, n = 12) or a high-sugar-high-fat (HSHF) diet supplemented with a low (100 μg/g·d, HSHF+LD group, n = 12), moderate (200 μg/g·d, HSHF+MD group, n = 12) or high dosage of krill oil (600 μg/g·d, HSHF+HD group, n = 12), simvastatin (HSHF+S group, n = 12) or saline (HSHF group, n = 12) continuously for 12 weeks. The resulting weight gains were attenuated, the liver index and the low-density lipoprotein, total cholesterol and triglyceride concentrations showed a stepwise reduction in the treated groups compared with those of the control group. A dose-dependent modulation of the gut microbiota was observed after treatment with krill oil. Low- and moderate- doses of krill oil increased the similarity between the composition of the HSHF diet-induced gut microbiota and that of the control, whereas the mice fed the high-dose exhibited a unique gut microbiota structure that was different from that of the control and HSHF groups. Sixty-five key operational taxonomic units (OTUs) that responded to the krill oil treatment were identified using redundancy analysis, of which 26 OTUs were increased and 39 OTUs were decreased compared with those of the HSHF group. In conclusion, the results obtained in this study suggest that the structural alterations in the gut microbiota induced by krill oil treatment were dose-dependent and associated with the alleviation of hyperlipidemia. Additionally, the high-dose krill oil treatment showed combined effects on the alleviation of hyperlipidemia and obesity.

BackgroundGut microbiome dysbiosis has been implicated in various gastrointestinal and extra-gastrointestinal diseases, but evidence on the efficacy and safety of fecal microbiota transplantation (FMT) for therapeutic indications remains unclear.MethodsThe gutMDisorder database was used to summarize the associations between gut microbiome dysbiosis and diseases. We performed an umbrella review of published meta-analyses to determine the evidence synthesis on the efficacy and safety of FMT in treating various diseases. Our study was registered in PROSPERO (CRD42022301226).ResultsGut microbiome dysbiosis was associated with 117 gastrointestinal and extra-gastrointestinal. Colorectal cancer was associated with 92 dysbiosis. Dysbiosis involving Firmicutes (phylum) was associated with 34 diseases. We identified 62 published meta-analyses of FMT. FMT was found to be effective for 13 diseases, with a 95.56% cure rate (95% CI: 93.88–97.05%) for recurrent Chloridoids difficile infection (rCDI). Evidence was high quality for rCDI and moderate to high quality for ulcerative colitis and Crohn’s disease but low to very low quality for other diseases.ConclusionGut microbiome dysbiosis may be implicated in numerous diseases. Substantial evidence suggests FMT improves clinical outcomes for certain indications, but evidence quality varies greatly depending on the specific indication, route of administration, frequency of instillation, fecal preparation, and donor type. This variability should inform clinical, policy, and implementation decisions regarding FMT.

The optimal therapy for severe infections caused by vancomycin-resistant Enterococcus faecium (VREfm) remains unclear, but the combination of linezolid and fosfomycin may be a good choice. The 24-h static-concentration time-kill study (SCTK) was used to preliminarily explore the pharmacodynamics of linezolid combined with fosfomycin against three clinical isolates. Subsequently, a hollow-fibre infection model (HFIM) was used for the first time to further investigate the pharmacodynamic activity of the co-administration regimen against selected isolates over 72 h. To further quantify the relationship between fosfomycin resistance and bacterial virulence in VREfm, the Galleria mellonella infection model and virulence genes expression experiments were also performed. The results of SCTK showed that the combination of linezolid and fosfomycin had additive effect on all strains. In the HFIM, the dosage regimen of linezolid (12 mg/L, steady-state concentration) combined with fosfomycin (8 g administered intravenously every 8 h as a 1 h infusion) not only produced a sustained bactericidal effect of 3∼4 log10 CFU/mL over 72 h, but also completely eradicated the resistant subpopulations. The expression of virulence genes was down-regulated to at least 0.222-fold in fosfomycin-resistant strains compared with baseline isolate, while survival rates of G. mellonella was increased (G. mellonella survival ≥45% at 72 h). For severe infections caused by VREfm, neither linezolid nor fosfomycin monotherapy regimens inhibited amplification of the resistant subpopulations, and the development of fosfomycin resistance was at the expense of the virulence of VREfm. The combination of linezolid with fosfomycin produced a sustained bactericidal effect and completely eradicated the resistant subpopulations. Linezolid plus Fosfomycin is a promising combination for therapy of severe infections caused by VREfm.

Objectives: The objective was to describe the changes of severe fever with thrombocytopenia syndrome virus (SFTSV) and antibody in the disease course and explore the relationship between antibody titers and patients’ prognosis.Methods: The levels of SFTSV, virus-specific immunoglobulin M (IgM), immunoglobulin G (IgG) titers, and cytokines in 37 patients with severe fever with thrombocytopenia syndrome (SFTS) were measured dynamically by real-time PCR and ELISA during the disease course; IgG titers were followed up in 53 cases. The correlation analysis of antibody titers with individual serum cytokines was calculated using the Spearman test.Results: The average time of SFTSV duration in individual serum was 22.45 ± 7.6 days from onset. We found SFTSV turned negative within the 10th day from the onset in two patients. SFTSV-specific IgM seroconversion occurred as early as within 3 days from the onset, increased gradually within the first 2 months, decreased gradually 3 months later, and disappeared after 6 months in all the patients. The average time of SFTSV-specific IgG antibody seroconversion was at 17 days from onset in the patients; the time was later in severe cases than in mild cases (23 ± 1.4 vs. 14.3 ± 1.0 days, p < 0.0001). IgG titers were maintained at the peak levels during the periods from 6 months to 1 year and decreased from the second year gradually. Severe cases had higher IgG levels than mild cases and also had a slower decreasing trend. During follow-up, only one lost IgG antibody 7 years later; no chronic infection and sequela were found among the 53 patients. None of the patients had SFTSV reinfection even if they were bitten by ticks again. The correlation analysis showed a positive relationship between inflammatory factors and IgG antibody levels.Conclusion: IgM antibody has important value in early diagnosis of SFTS. A moderate inflammatory response is beneficial for production and duration of IgG antibodies.

Enterococci, the main pathogens associated with nosocomial infections, are resistant to many common antibacterial drugs including β-lactams, aminoglycosides, etc. Combination therapy is considered an effective way to prevent bacterial resistance. Preliminary studies in our group have shown that linezolid combined with fosfomycin has synergistic or additive antibacterial activity against enterococci, while the ability of the combination to prevent resistance remains unknown. In this study, we determined mutant prevention concentration (MPC) and mutant selection window (MSW) of linezolid, fosfomycin alone and in combination including different proportions for five clinical isolates of Enterococcus and characterized the resistance mechanism for resistant mutants. The results indicated that different proportions of linezolid combined with fosfomycin had presented different MPCs and MSWs. Compared with linezolid or fosfomycin alone, the combination can restrict the enrichment of resistant mutants at a lower concentration. A rough positive correlation between the selection index (SI) of the two agents in combination and the fractional inhibitory concentration index (FICI) of the combination displayed that the smaller FICI of linezolid and fosfomycin, the more probable their MSWs were to close each other. Mutations in ribosomal proteins (L3 and L4) were the mechanisms for linezolid resistant mutants. Among the fosfomycin-resistant mutants, only two strains have detected the MurA gene mutation related to fosfomycin resistance. In conclusion, the synergistic combination of linezolid and fosfomycin closing each other’s MSW could effectively suppress the selection of enterococcus resistant mutants, suggesting that the combination may be an alternative for preventing enterococcal resistance. In this study, the resistance mechanism of fosfomycin remains to be further studied.

Phanerochaete chrysosporium is a white rot fungus naturally isolated from hardwoods and widely used in environmental pollution control because it produces extracellular peroxidases. It forms chlamydospores during nitrogen starvation, which naturally occurs in the habitat of P. chrysosporium. Chlamydospores protect fungi against many stresses; the molecular basis underlying chlamydospore formation in basidiomycetes is poorly explored. Chlamydospores in P. chrysosporium have a different cell wall compared with hyphae, as confirmed by cell wall digestion and microscopy. Furthermore, this study investigated the transcriptome of P. chrysosporium in different life stages, including conidium, hypha, and chlamydospore formation, through RNA sequencing. A total of 2215 differentially expressed genes were identified during these processes. The expression patterns of genes involved in several molecular events critical for chlamydospore formation, including starch and sucrose metabolism, phosphatase and kinase, and transcription factors, were determined. This study serves as a basis for further investigating the function of chlamydospore formation in the biotechnologically relevant fungus P. chrysosporium.

ObjectiveThe aims of this study were to describe azithromycin (AZM) susceptibility patterns among Shigella isolates in Anhui, China and identify predictors of resistance with mobile element-mediated genes.MethodsA total of 517 non-duplicate Shigella isolates (449 S. flexneri and 68 S. sonnei) were collected in the Anhui Province of China from September 2011–September 2015, and screened for the plasmid-mediated genes of decreased susceptibility to AZM (DSA), using polymerase chain reaction amplification and sequencing. Conjugation experiments and pulsed-field gel electrophoresis were conducted for all mphA-positive DSA isolates.ResultsThe DSA rate for 449 S. flexneri isolates was 33.6%, compared with 39.7% for 68 S. sonnei isolates. Among 161 DSA S. flexneri isolates, 93 (57.8%) carried the mphA gene. Among 27 DSA S. sonnei isolates, 11 (40.7%) carried the mphA gene. However, other plasmid-mediated DSA genes were not found in these isolates. A total of 89 transconjugants (95.7%) were obtained from 93 mphA-positive S. flexneri isolates through conjugation, and 10 transconjugants (90.9%) were obtained from 11 mphA-positive S. sonnei isolates. Furthermore, the minimum inhibitory concentrations (MICs) of AZM among 89 S. flexneri transconjugants ranged from 4 to 128 μg/mL, with an MIC50 of 8 μg/mL and MIC90 of 32 μg/mL. The MICs of AZM among 10 S. sonnei transconjugants ranged from 4 to 256 μg/mL, with an MIC50 of 8 μg/mL and MIC90 of 64 μg/mL. Thirteen clusters were found for mphA-positive S. flexneri, and five clusters were found for mphA-positive S. sonnei. Furthermore, 10 homologous isolates among 13 mphA-positive S. flexneri isolates with high-level DSA were from Sixian county and were multidrug-resistant strains. Of the 10 homologous S. flexneri isolates, eight were from children (≤5 years old), and two from the elderly (>60 years old).ConclusionOur study demonstrates that the DSA for Shigella isolates was severe, and the plasmid-mediated mphA gene was the most common macrolide resistance gene detected in Shigella isolates collected in Anhui, China. The mphA-positive S. flexneri isolates with high-level DSA facilitated clonal spread in children and the elderly. This finding is noteworthy and warrants further study.

In recent decades, the incidence of Cryptococcus neoformans infection, which causes cryptococcosis, has consistently increased. Fluconazole (FLU) is frequently used in the treatment of this disease, mainly in the immunocompromised population, and long-term therapy usually produces drug resistance. Research on antifungal sensitizers has gained attention as a possible means of overcoming this drug resistance. Minocycline (MINO) has an inhibitory effect in vitro on FLU-resistant Candida albicans, and the combination of MINO and FLU has a synergistic effect on FLU-resistant C. albicans. A synergistic effect of MINO/FLU has been reported against C. neoformans, but this effect has not been evaluated on FLU-resistant isolates. This study aimed to investigate the interaction of MINO and FLU against FLU-resistant C. neoformans both in vitro and in vivo. We found that the combination of MINO and FLU had a synergistic effect on FLU-resistant C. neoformans in vitro. For all FLU-resistant strains, the minimum inhibitory concentration (MIC) of FLU decreased significantly when used in combination with MINO, dropping from >128 μg/ml down to 4–8 μg/ml. Additionally, MINO and FLU had a synergistic effect on both susceptible and resistant C. neoformans biofilms, in which the MIC of FLU decreased from >256 μg/ml down to 4–16 μg/ml. Compared with FLU alone, the combination of MINO with FLU prolonged the survival rate of Galleria mellonella larvae infected with FLU-resistant C. neoformans, and also significantly decreased the fungal burden of infected larvae and reduced the tissue damage and destruction caused by FLU-resistant C. neoformans. These findings will contribute to the discovery of antifungal agents and may yield a new approach for the treatment of cryptococcosis caused by FLU-resistant C. neoformans.

Synthetic dyes are widely used in many industries, but they cause serious environmental problems due to their carcinogenic and mutagenic properties. In contrast to traditional physical and chemical treatments, biodegradation is generally considered an environmental-friendly, efficient, and inexpensive way to eliminate dye contaminants. Here, a novel laccase-like enzyme Lac1326 was cloned from a marine metagenomic library. It showed a maximum activity at 60°C, and it retained more than 40% of its maximal activity at 10°C and more than 50% at 20–70°C. Interestingly, the laccase behaved stably below 50°C, even in commonly used water-miscible organic solvents. The enzyme decolorized all tested dyes with high decolorization efficiency. This thermostable enzyme with high decolorization activity and excellent tolerance of organic solvents and salt has remarkable potential for bioremediation of dye wastewater. It is thus proposed as an industrial enzyme.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease caused by SFTS virus, and the number of SFTS cases increased year by year in China. Previous studies had indicated that gut microbiome closely associated with human health and diseases, including infection diseases, liver diseases, gastrointestinal diseases and metabolic diseases. The aim of this study is to investigate the alterations and involvements of gut microbial in SFTS patients. We compared the gut microbiome of 26 SFTS patients between 20 health controls using the Illumina MiSeq sequencing platform. Reduced gut microbiota diversity and dramatic shifts of fecal microbial composition in SFTS patients were observed compared with health controls. In the intestinal microbial of SFTS patients, the Lachnospiraceae and Ruminococcaceae which could produce short-chain fatty acids were clearly dropped compared with health people, meanwhile, Sutterella which have anti-inflammation properties were reduced too. On the contrary, some common opportunistic pathogens like Enterococcus and Streptococcus and endotoxin-producing bacteria Escherichia which could rise the risk of infections were increased in SFTS patients than healthy people, in addition lactate-producing bacteria Lactobacillaceae also significantly increased in SFTS patients. In addition, research findings on the correlation between gut microbiota and biochemical data found that the changes of gut microbiota of SFTS patients were closely associated with clinical symptoms, key serum enzymes, infection and mortality. These alterations of gut microbiome in SFTS patients suggest the potential contributions of gut microbial to the pathogenesis of SFTS.

Accumulating data have identified the important roles of PA protein in replication and pathogenicity of influenza A virus (IAV). Identification of host factors that interact with the PA protein may accelerate our understanding of IAV pathogenesis. In this study, using immunoprecipitation assay combined with liquid chromatography-tandem mass spectrometry, we identified 278 human cellular proteins that might interact with PA of H5N1 IAV. Gene Ontology annotation revealed that the identified proteins are highly associated with viral translation and replication. Further KEGG pathway analysis of the interactome profile highlighted cellular pathways associated with translation, infectious disease, and signal transduction. In addition, Diseases and Functions analysis suggested that these cellular proteins are highly related with Organismal Injury and Abnormalities and Cell Death and Survival. Moreover, two cellular proteins (nucleolin and eukaryotic translation elongation factor 1-alpha 1) identified both in this study and others were further validated to interact with PA using co-immunoprecipitation and co-localization assays. Therefore, this study presented the interactome data of H5N1 IAV PA protein in human cells which may provide novel cellular target proteins for elucidating the potential molecular functions of PA in regulating the lifecycle of IAV in human cells.