Medical Microbiology and Immunology最新文献

Dengue virus (DENV) is a global health threat, with approximately 390 million infections annually, ranging from mild dengue fever to severe dengue hemorrhagic fever and shock syndrome. MicroRNA (miRNA) are crucial post-transcriptional regulators which may regulate host resistance to DENV infection. This study aimed to identify miRNAs involved in natural resistance to DENV infection. Individuals from a dengue-endemic area were classified as susceptible (SD) or resistant (RD) according to their anti-DENV antibody status. RD individuals were seronegative despite high local DENV infection prevalence. Monocytes susceptibility to DENV infection was assessed in vitro. The miRNome profiles of the monocytes from 7 individuals per group were assessed upon mock or DENV-2 infection. The antiviral effect of differentially expressed miRNAs was analyzed using miRNA mimics in HeLa cells followed by infection with DENV-1, DENV-2, DENV-3, and DENV-4 serotypes. We performed RNA-seq on miRNA mimic-transfected cells to identify miRNA-targeted genes interacting with DENV proteins. Monocytes from RD individuals exhibit lower DENV-2 production in vitro. The miRNAs miR-155, miR-132-3p, miR-576-5p were overexpressed in monocytes from RD group upon DENV-2 infection. The transfection of miR-155-5p mimic reduced DENV infection and viral production in HeLa cells, regulating 18 genes interacting with DENV proteins and downregulating target genes involved in interferon response, TP53 regulation, apoptosis, and vesicle trafficking (e.g. HSD17B12, ANXA2). Therefore, we show that monocytes from RD individuals show a distinct miRNA expression profile and reduced viral production. In vitro miR-155-5p upregulation induces an antiviral state, revealing potential therapeutic targets to treat dengue.

Leptospirosis is a major cause of acute febrile illness, often presenting with non-specific symptoms that can lead to misdiagnosis. Early laboratory diagnosis is essential for confirmation to avoid misdiagnosis and ensure appropriate management. This study aimed to identify and produce a recombinant protein, approximately 25 kDa, with high antigenicity for diagnostic applications. The 25 kDa protein from Leptospira interrogans was identified as electron transfer flavoprotein beta subunits (Etfβ) and exhibited 98% nucleotide and 99% amino acid homology to the reference strain. Lateral flow assays (LFAs) using recombinant Etfβ (rEtfβ) as antigens were developed to detect specific antibodies, namely rEtfβ-IgM and rEtfβ-IgG, and evaluated their performance against the standard microscopic agglutination test (MAT). Testing 33 paired serum samples from confirmed leptospirosis cases and 24 controls revealed sensitivities of 69.7% for IgM and 57.6% for IgG. However, the combined assays yielded enhanced diagnostic accuracy, achieving a sensitivity of 94.0%, specificity of 95.8%, positive predictive value of 96.9%, negative predictive value of 92.0%, and percent agreement of 94.7% (kappa value of 0.89). Also, the combined LFAs demonstrated 66.7% in initial serum samples whose MAT results were negative, enhancing the capacity for early diagnosis. In conclusion, the developed rapid tests demonstrated strong diagnostic capability, particularly in early-phase leptospirosis, distinguishing between initial and recurrent infections. Importantly, rEtfβ-IgG identified a subset of patients lacking detectable IgM. Thus, integrating rEtfβ-IgM and rEtfβ-IgG is recommended to improve sensitivity and accuracy in endemic populations. The rEtfβ is a promising target for future antigen-based diagnostic strategies for leptospirosis. The rEtfβ antigen shows promise as a target for future development of antigen-based diagnostic strategies for leptospirosis.

It is now widely accepted that lungs are colonized by diverse microbes. Dysbiosis of the lung microbiota has been found to affect the progression of lung cancer. Fungi are a major component of the lung microbiota. However, the causal links between the mycobiome or specific species and lung cancer remain unclear. To address this, we conducted a study examining the composition of lung mycobiota in Non-Small-Cell Lung Cancer (NSCLC) patients using shotgun metagenomics. The differential taxa between NSCLC patients and non-cancer controls were defined by the Wilcoxon rank-sum test. Nested PCR was used to measure the abundance of specific fungal species. Metabolomics analysis was performed to investigate the metabolic reprogramming of macrophages triggered by intracellular infection of specific fungal species. In vitro and in vivo assays were conducted to examine the effect of the specific fungus on cancer cell growth. Our findings showed that Ascomycota, Microsporidia and Mucoromycota were the dominant fungal taxa in the lungs. Talaromyces marneffei (T.marneffei) was the most significantly differential fungus between lung cancer patients and non-cancer controls, with its abundance positively correlated with lung cancer. The lung cancer animal model demonstrated that T.marneffei promotes lung cancer growth. Our study also demonstrated that T.marneffei promotes lung cancer cell growth by inducing dose-dependent M2 macrophage polarization through arginine-ornithine-cycle activation. Furthermore, inhibition of arginase can reduce M2 polarization of macrophages and the survival of T. marneffei inside macrophages. In summary, our study reveals that the increased abundance of T. marneffei in the lungs affects lung cancer cell growth by triggering arginine-induced M2 polarization of macrophages. These findings provide potential drug targets for the development of therapies aimed at targeting the survival of fungi inside macrophages in the fight against cancer.

Heat-labile toxin (LT) from enterotoxigenic Escherichia coli (ETEC) is an important pathogenic protein. Anti-LT antibodies (Abs) induced by vaccination can neutralize the toxin and potentially prevent diarrheal secretion from ~ 60% of ETEC strains expressing LT. However, only superficial investigation of the anti-toxin response is usually conducted in clinical trials. Here, we utilized human serum samples from two clinical trials performed to assess safety, immunogenicity and protection in a controlled human infection model with a LT + ST + CFA/I + H10407 ETEC strain. These Phase 1 and Phase 2b clinical trials explored a prototype ETEC adhesin (CfaE) and a chimeric adhesin-toxoid protein (dscCfaE-CTA2/LTB5) delivered intradermally or transcutaneously with a mutated form of LT (mLT) as an adjuvant. Serum samples were tested for antigen-specific IgG or IgA Abs by immunoblot, enzyme-linked immunosorbent assay (ELISA), or functional neutralizing Abs using LT holotoxin, LTA or LTB subunits. Abs to both LT subunits were present, but the response to each was altered by vaccine formulation, dose, and delivery routes as well as subject. The anti-LT IgG response correlated best to neutralizing antibodies and protection from H10407 controlled challenge when compared to other measures including serum IgA or anti-fimbriae (CfaE) Abs. In addition, our results helped to explain cohort attack rate differences in naïve unvaccinated participants and we found higher anti-LTA IgG post-challenge significantly related to ETEC severity score. Thus, strategies generating and measuring immunity to the complete AB₅ structure of LT and subunits are better determinant of assessing protective immunity against LT + or LT + ST + ETEC diarrheal secretion in humans.

In this paper we report a human ex vivo model of Aspergillus fumigatus and Candida albicans infection of the cornea. We demonstrate the ability to monitor fungal growth on the cornea through optical and immunofluorescence microscopy. Additionally, we establish a method for collection of fungal antigens in polyethersulfone (PES) membrane-based sample collectors from the surface of fungal inoculated corneas. Immunofluorescence microscopy was performed directly on both corneal tissue and PES membrane sample collectors. For the latter case, we devised an original ad-hoc method by attaching the membranes used for the collection on standard glass slides, which we call glass slide KIT. This enabled easy handling and improved efficiency for specifically recognizing the corresponding fungal infections by simple immunoassay protocols. As a result, we firstly observe the ability to monitor fungi in corneal tissue, and secondly demonstrate the adsorption of fungal antigens onto PES membranes. Thus, we report for the first time the specific detection of fungal corneal infections in easy to use PES membrane based glass slide KITs through simple immunofluorescence, as an alternative to microbiological culture.

Aspiration pneumonia is a serious respiratory condition, which is particularly prevalent in patients with dysphagia, neurological disorders, or those undergoing surgical interventions. The formation of multispecies biofilms in the oral cavity, involving the bacterial periodontopathogen Porphyromonas gingivalis and the opportunistic pathogenic fungus Candida albicans, may also be related to the development of this serious disease, contributing also to the resistance to standard antimicrobial treatment. Therefore, this research aimed to evaluate the efficacy of selected antibiotics‒levofloxacin, metronidazole, meropenem, vancomycin‒and antifungal agents‒amphotericin B, caspofungin, and fluconazole‒on these mixed biofilms in the aspiration pneumonia model. While metronidazole and levofloxacin effectively inhibited bacterial viability in the mixed biofilms, lower doses increased release of bacterial proteases. In the conditions of mixed biofilms meropenem and vancomycin showed reduced efficacy, requiring significantly higher doses to achieve similar effect in mixed biofilms as in single bacterial cultures. Treatment with antifungals revealed that amphotericin B significantly impacted fungal cell viability within mixed biofilms, and this effect was enhanced when the antifungal drug was applied in the presence of P. gingivalis. Caspofungin and fluconazole showed variable efficacy, with caspofungin being more effective against C. albicans cells within biofilm.These findings indicated that due to the mutual microbial protection in the mixed-species biofilm, P. gingivalis retained its virulence despite increasing antibiotic doses. However, no excessive benefit of mixed biofilms was observed for C. albicans in the presence of antifungals, indicating the minor importance of yeasts in aspiration pneumonia development and their protective role for other pathogens in mixed-species infection.

Cytolethal distending toxins (CDTs), encoded by cdtABC genes, have DNase activity leading to cellular and nuclear distention, resulting in actin remodeling, irreversible cell cycle arrest and apoptosis of target cells. PCR cdt-positive Escherichia coli strains have been isolated from children with diarrhea worldwide. However, toxin production and biological activity of cdt⁺ strains are rarely confirmed. Here, we characterized the biological activity of cdt⁺ E. coli of clinical isolates from Mexican children with severe diarrhea and its relationship with the harbored cdt type. Ten isolates from seven patients containing cdt⁺ E. coli, one isolate from a patient containing cdt^- E. coli, and a prototype CDT-producing E. coli were used to determine the harbored cdt-type, cell distention, actin remodeling and cell cycle arrest on epithelial cells. Three isolates harbored cdt type I, one type II, two type III, two type IV and two simultaneously type II and III. Lysates from eight cdt⁺ E. coli isolates caused cell distention, actin cytoskeletal remodeling and cell cycle arrest but two isolates from the same patient harboring simultaneously cdt type II/III did not. The cdt genes were necessary and enough to cause the cytolethal distending pathology. Mutants in cdtAB_IC (O86:H34 strain; cdt-I) and cdtAB_IIC (isolate; cdt-II) were complemented by cdtAB_IIC genes and both recovered the CDT-induced phenotypes. Transformation of E. coli BL21 by cdtAB_IIC genes caused this cytolethal distending pathology. These data indicate that cdt + E. coli isolates are potentially dangerous bacteria to cause serious epithelial cell damage and cell death to aggravate childhood diarrhea.

nKlebsiella pneumoniae is a common pathogen of healthcare-associated infections expressing a plethora of antimicrobial resistance loci, including ADP-ribosyltransferase coding genes (arr), able to mediate rifampicin resistance. The latter has activity against a broad range of microorganisms by inhibiting DNA-dependent RNA polymerases. This study aims to characterise the arr distribution and genetic context in 138 clinical isolates of K. pneumoniae and correlate these with rifampicin resistance. All isolates were subjected to whole-genome sequencing for species identification, typing and AMR genes identification, along with the determination of the minimum inhibitory concentration (MIC) of rifampicin. Molecular detection of arr genes and class 1 integrons was performed for rifampicin-resistant isolates. Efflux activity was investigated as a possible determinant of rifampicin resistance in isolates devoid of known genetic determinants. Twelve isolates exhibited high rifampicin MICs (≥ 64 mg/L), 124 showed intermediate MICs (16-32 mg/L) and two displayed low (8 mg/L) MICs. Two arr allelic variants, arr-2 and arr-3, were found across one and nine K. pneumoniae isolates, respectively, all within class 1 integrons, including a newly described integron, and all associated with high rifampicin MICs  (≥ 64 mg/L). Elevated resistance levels were additionally linked to increased arr-2/3 expression and closer proximity to the promoter. No arr gene or rpoB mutations were found across the remaining two isolates and no correlation between efflux activity and high-level rifampicin resistance was found for both isolates. In conclusion, this study demonstrates that arr genes confer high levels of rifampicin resistance in K. pneumoniae highlighting its widespread dissemination within class 1 integrons.

Toxoplasma gondii infects approximately 30% of the population, and there is currently no approved vaccine. Identifying immunogenic peptides with high affinity to different HLA molecules is a promising vaccine strategy. This study used an in silico approach using artificial neural networks to identify T. gondii peptides restricted to HLA-A*02, HLA-A*24, and HLA-B*35 alleles. Proteomes from seven T. gondii strains and transcriptomic data of overexpressed genes from T. gondii-RH in human PBMC were also used. Parasite protein sequences were analyzed with R 'Epitope Prediction' library. Peptide candidates were evaluated in the artificial neural networks based on the probabilities of output neurons (p > 0.5). The IFN-γ responses in PBMC from T. gondii seronegative and seropositive individuals were evaluated by ELISpot. Peptides with higher IFN-γ induction were evaluated to identify cytotoxic response in CD8⁺ T cells (CD107a). In silico analysis identified 36 peptides from T. gondii proteins with predicted affinity to HLA-A*02, A*24, and B*35 alleles. Experiments with PBMCs revealed that a peptide restricted to HLA-A02 (P1: FLFAWITYV) induced a significant increase in IFN-γ-producing cells (p = 0.004). For HLA-A24, a peptide (P8: VFAFAFAFFLI) also induced a significant IFN-γ response (p = 0.004), while for the HLA-B*35 allele, the P6 peptide (YPIAPSFAM) induced a response that differed significantly from the control (p = 0.05). These peptides induced also a significant percentage of central memory CD8 + T cells expressing the degranulation marker CD107a (p < 0.05). Finally, we identified three T. gondii peptides that induced IFN-γ response, and a cytotoxic response measured by CD107a expression on CD45RAneg-CD8 cells. These peptides could be considered part of a multi-epitope vaccine against toxoplasmosis in humans.

Introduction: While the general immune response to Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) is well-understood, the long-term effects of Human Immunodeficiency Virus-1/Severe Acute Respiratory Syndrome-Coronavirus-2 (HIV-1/SARS-CoV-2) co-infection on the immune system remain unclear. This study investigates the immune response in people with HIV-1 (PWH) co-infected with SARS-CoV-2 to understand its long-term health consequences.

Methods: A retrospective longitudinal study of PWH with suppressed viral load and SARS-CoV-2 infection was conducted. Cryopreserved peripheral blood mononuclear cells and plasma samples were collected at three time-points: HIV-1/pre-SARS-CoV-2 (n = 18), HIV-1/SARS-CoV-2 (n = 46), and HIV-1/post-SARS-CoV-2 (n = 36). Plasma levels of 25 soluble cytokines and chemokines, and anti-S/anti-N-IgG-SARS-CoV-2 antibodies were measured. Immunophenotyping of innate and adaptive immune components and HIV-1 and SARS-CoV-2-specific T/B-cell responses were assessed by flow cytometry.

Results: HIV-1/SARS-CoV-2 co-infection was associated with long-lasting immune dysfunction, characterized by elevated levels of pro-inflammatory cytokines and a decrease in the MIG-IP10-ITAC chemokine axis at the HIV/SARS-CoV-2 time-point, which persisted one year later. Additionally, alterations in the distribution of subsets and increased activation (NKG2D/NKG2C) and maturation (TIM3) markers of NK and dendritic cells were observed at the HIV-1/SARS-CoV-2 time-point, persisting throughout the study. Effector memory CD4 T-cell subsets were decreased, while exhaustion/senescence (PD1/TIM3/CD57) markers were elevated at all three time-points. SARS-CoV-2-specific T/B-cell responses remained stable throughout the study, while HIV-1-specific T-cell responses decreased at the HIV-1/SARS-CoV-2 time-point and remained so.

Conclusions: Persistent immune dysfunction in HIV-1/SARS-CoV-2 co-infection increases the risk of future complications, even in PWH with mild symptoms. Exacerbated inflammation and alterations in immune cells may contribute to reduce vaccine efficacy and potential reinfections.