A Multiepitope Peptide, rOmp22, Encapsulated in Chitosan-PLGA Nanoparticles as a Candidate Vaccine Against Acinetobacter baumannii Infection.

BACKGROUND: The development of vaccines is a promising and cost-effective strategy to prevent emerging multidrug-resistant (MDR) Acinetobacter baumannii (A. baumannii) infections. The purpose of this study was to prepare a multiepitope peptide nanovaccine and evaluate its immunogenicity and protective effect in BALB/c mice. METHODS: The B-cell and T-cell epitopes of Omp22 from A. baumannii were predicted using bioinformatics methods and identified by immunological experiments. The optimal epitopes were conjugated in series by 6-aminocaproic acid and chemically synthesized multiepitope polypeptide rOmp22. Then, rOmp22 was encapsulated by chitosan (CS) and poly (lactic-co-glycolic) acid (PLGA) to prepare CS-PLGA-rOmp22 nanoparticles (NPs). The immunogenicity and immunoprotective efficacy of the vaccine were evaluated in BALB/c mice. RESULTS: CS-PLGA-rOmp22 NPs were small (mean size of 272.83 nm) with apparently spherical structures, positively charged (4.39 mV) and nontoxic to A549 cells. A high encapsulation efficiency (54.94%) and a continuous slow release pattern were achieved. Compared with nonencapsulated rOmp22, CS-PLGA-rOmp22 immunized BALB/c mice induced higher levels of rOmp22-specific IgG in serum and IFN-γ in splenocyte supernatant. Additionally, lung injury and bacterial burdens in the lung and blood were suppressed, and potent protection (57.14%-83.3%) against acute lethal intratracheal A. baumannii challenge was observed in BALB/c mice vaccinated with CS-PLGA-rOmp22. CONCLUSION: CS-PLGA-rOmp22 NPs elicited specific IgG antibodies, Th1 cellular immunity and protection against acute lethal intratracheal A. baumannii challenge. Our results indicate that this nanovaccine is a desirable candidate for preventing A. baumannii infection.

Rv2346c enhances mycobacterial survival within macrophages by inhibiting TNF-α and IL-6 production via the p38/miRNA/NF-κB pathway.

The intracellular survival of Mycobacterium tuberculosis (Mtb) has a central role in the pathogenesis of tuberculosis. Mtb Rv2346c is a member of 6-kDa early secreted antigenic target family of proteins, which are known to inhibit the host immune responses to promote bacillary persistence in macrophages. However, the mechanism through which Rv2346c participates in Mtb pathogenesis is unclear. In the present study, recombinant Rv2346c protein was synthesized and used to treat Bacillus Calmette-Guérin (BCG)-infected macrophages. The results showed that Rv2346c inhibited the proliferation of BCG-infected macrophages and enhanced the survival of BCG in macrophages. Tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 were upregulated during BCG infection but downregulated by Rv2346c. Additional experiments showed that nuclear transcription factor-κB (NF-κB) in BCG-infected macrophages induced the production of TNF-α and IL-6. In addition, miR-155 and miR-99b had a suppressive effect on NF-κB, and the expression of these miRNAs was promoted by p38. Furthermore, Rv2346c was shown to decrease the activation of NF-κB, whereas it enhanced the phosphorylation of p38 and the expression of miR-155 and miR-99b. The function of Rv2346c was also verified in Mtb-infected mice. The results showed that Rv2346c increased the observed bacterial load and lung injury and downregulated TNF-α and IL-6 in vivo. Overall, our results reveal that Rv2346c enhances mycobacterial survival in macrophages via inhibiting the production of TNF-α and IL-6 in a p38/miRNA/NF-κB pathway-dependent manner, suggesting that Rv2346c acts as a crucial virulence factor in Mtb infection and has potential use as a target for anti-tuberculosis therapy.

Comparison of the influence on renal function between cefepime and cefpirome.

Although known for their broad spectrum and curative efficacy on drug-resistant pathogens and as nephrotoxicity-free, impairments were observed on renal function during clinical treatment of the two most commonly used fourth-generation cephalosporins: Cefpirome and cefepime. The present study aimed to further explore the exact influences of them on renal function. In vitro, the cell viability of renal cells cultured in drug-combined medium was tested for six dilutions. In vivo, a clinical cohort study was carried out to detect the influence of cefpirome and cefepime on the serum creatinine (SCr) level of patients. Cefpirome had an inhibition rate with half maximal inhibitory concentration (IC50) of 143.5 µmol/l on renal mesangial cells, which was greater compared to the IC50 of 7.702 µmol/l for cefepime. The clinical cohort study data revealed that cefpirome treatment could lead to a greater increase of the average SCr level compared to cefepime on days 3 and 7 during therapy, and in addition, a greater incidence of SCr >445 µmol/l, an indicator of clinical renal failure. Furthermore, patients with an average age >65 years were observed as more susceptible to an SCr rise caused by either cefpirome or cefepime, with a larger augment in the average SCr, as well as a higher incidence of SCr >445 µmol/l compared to patients aged <65 years. In conclusion, cefpirome may have more potential to cause renal impairment compared to cefepime, therefore, more caution and comprehensive analysis of patient conditions is required during the clinical choice of fourth-generation cephalosporins.

Chrysin alleviates allergic inflammation and airway remodeling in a murine model of chronic asthma.

Asthma is a chronic airway inflammatory disorder and progresses mainly due to airway remodeling. Chrysin, a natural flavonoid, has been reported to possess multiple biologic activities, including anti-inflammation, anti-oxidation and anti-proliferation. The present study aimed to investigate whether chrysin could relieve allergic airway inflammation and remodeling in a murine model of chronic asthma and the mechanism involved. The female BALB/c mice sensitized and challenged with ovalbumin (OVA) successfully developed airway hyperresponsiveness (AHR), inflammation and remodeling. The experimental data showed that chrysin could alleviate OVA-induced AHR. Chrysin could also reduce OVA-induced increases in the number of inflammatory cells, especially eosinophils, interleukin (IL) -4, and IL-13 in bronchoalveolar lavage fluid (BALF) and total IgE in serum. The decreased interferon-γ (IFN-γ) level in BALF was also upregulated by chrysin. In addition, inflammatory cell infiltration, goblet cell hyperplasia and the expression of α-smooth muscle actin (α-SMA) around bronchioles were suppressed by chrysin. Furthermore, the phosphorylation levels of Akt and extracellular signal-regulated kinase (ERK) could be decreased by chrysin, which are associated with airway smooth muscle cell (ASMC) proliferation. These results indicate the promising therapeutic effect of chrysin on chronic asthma, especially the progression of airway remodeling.

Protective effect of DNA vaccine encoding pseudomonas exotoxin A and PcrV against acute pulmonary P. aeruginosa Infection.

Infections with Pseudomonas aeruginosa have been a long-standing challenge for clinical therapy because of complex pathogenesis and resistance to antibiotics, thus attaching importance to explore effective vaccines for prevention and treatment. In the present study, we constructed a novel DNA vaccine by inserting mutated gene toxAm encoding Pseudomonas Exotoxin A and gene pcrV encoding tip protein of the type III secretion system into respective sites of a eukaryotic plasmid pIRES, named pIRES-toxAm-pcrV, and next evaluated the efficacy of the vaccine in murine acute Pseudomonas pneumonia models. Compared to DNA vaccines encoding single antigen, mice vaccinated with pIRES-toxAm-pcrV elicited higher levels of antigen-specific serum immunoglobulin G (IgG), enhanced splenic cell proliferation and cytokine secretion in response to Pseudomonas aeruginosa antigens, additionally PAO1 challenge in mice airway resulted in reduced bacteria burden and milder pathologic changes in lungs. Besides, it was observed that immunogenicity and protection could be promoted by the CpG ODN 1826 adjuvant. Taken together, it's revealed that recombinant DNA vaccine pIRES-toxAm-pcrV was a potential candidate for immunotherapy of Pseudomonas aeruginosa infection and the CpG ODN 1826 a potent stimulatory adjuvant for DNA vaccination.