In-Silico and In-Vitro Evaluation of Antibacterial, Cytotoxic, and Apoptotic Activity and Structure of Modified CM11 Peptide

Intranasal and intraperitoneal immunization against Brucella infection using niosome and mannosylated niosomes containing Brucella recombinant trigger factor/Bp26/Omp31 chimeric protein in a mouse model

Purpose

Brucellosis, a zoonotic infectious disease, is a worldwide health issue affecting animals and humans. No effective human vaccine and the complications caused by the use of animal vaccines are among the factors that have prevented the eradication of the disease worldwide. However, bio-engineering technologies have paved the way for designing new targeted and highly efficacious vaccines. In this regard, the study aimed to evaluate immunity induced by mannosylated niosome containing Brucella recombinant trigger factor/Bp26/Omp31 (rTBO) chimeric protein in a mouse model.

Materials and Methods

rTBO as chimeric antigen (Ag) was expressed in Escherichia coli BL21 (DE3) and, after purification, loaded on niosome and mannosylated niosome. The characteristics of the nanoparticles were assessed. The mice were immunized using rTBO, niosome, and mannosylated niosome-rTBO in intranasal and intraperitoneal routes. Serum antibodies (immunoglobulin [Ig]A, IgG, IgG1, and IgG2a) and splenocyte cytokines (interferon-gamma, interleukin [IL]-4, and IL-12) were evaluated in immunized mice. Finally, immunized mice were challenged by B. melitensis and B. abortus. A high antibody level was produced by niosomal antigen (Nio-Ag) and mannosylated noisomal antigen (Nio-Man-Ag) compared to the control after 10, 24, and 38 days of immunization. The IgG2a/IgG1 titer ratio for Nio-Man-Ag was 1.2 and 1.1 in intraperitoneal and intranasal methods and lower than one in free Ag and Nio-Ag. Cytokine production was significantly higher in the immunized animal with Ag-loaded nanoparticles than in the negative control group (p<0.05). Moreover, cytokine and antibody levels were significantly higher in the injection than in the inhalation method (p<0.05).

Results

The combination of mannosylated noisome and rTBO chimeric proteins stimulate the cellular and humoral immune response and produce cytokines, playing a role in developing the protective acquired immune response in the Brucella infectious model. Also, the intraperitoneal route resulted in a successful enhancement of cytokines production more than intranasal administration.

Conclusion

Designing an effective vaccine candidate against Brucella that selectively induces cellular and humoral immune response can be done by selecting a suitable nanoniosome formulation as an immunoadjuvant and recombinant protein as an immune response-stimulating Ag.

Molecular Docking, Anti-Biofilm & Antibacterial Activities and Therapeutic Index of mCM11 Peptide on Acinetobacter baumannii Strains

Despite the huge efforts of microbiologists, infectious diseases have yet remained one of the leading causes of death in humans, further highlighting the research priority for controlling opportunistic pathogens. Many researchers have used antibacterial peptides to solve the problem of antibiotic resistance. This research is thus conducted to investigate the antibacterial and anti-biofilm activity of a novel modified cecropin-melittin 11-peptide with improved therapeutic properties and lower side effects. After synthesis and purification of mCM11 (NH2-WRLFRRILRVL-NH2) by solid-phase synthesis and HPLC methods, respectively, the antibacterial and biofilm inhibitory activities were explored in vitro. TMHMM was used to confirm the reaction of mCM11 on the plasma membrane of the prokaryotic cells. The interaction between mCM11 on Acinetobacter baumannii strains was investigated by molecular docking using ClusPro2.0. Hemolysis and therapeutic indexes were also calculated to quantify the relative safety and adverse effects of mCM11. According to the results, mCM11 has a high inhibitory and lethal effect on A. baumannii strains due to its cationic properties and new specific sequence. Molecular docking revealed the release of a significant amount of energy when mCM11 binds to the surface of A. baumannii in an appropriate site. The findings indicated that mCM11 IC50 (4 μg/mL) lysed 2.78% of RBCs; moreover, 8 strains of Acinetobacter baumannii showed a favorable therapeutic index. The mCM11 exhibits strong antibacterial and antibiofilm activities against A. baumannii strains, suggesting its potential therapeutic role in infections caused by these strains. Similar to its impact on A. baumannii, mCM11 could be a suitable alternative to antibiotics in combat against antibiotic-resistant bacteria in the in vivo experiments.

Evaluation of the antileishmanial effect of polyclonal antibodies and cationic antimicrobial peptides

Leishmaniasis is one of the tropical and subtropical diseases which, according to WHO, has the priority of control. The list of anti-leishmanial drugs is limited and requires side effects, high costs, and long-term treatments. Various species, parasite resistance, and simultaneous diseases are among the factors that affect the effectiveness of treatment. Due to these problems and based on satisfactory records of previous studies using antimicrobial peptides (AMPs) against infectious diseases, this study aimed to evaluate the antileishmanial effect of Leishmania-infected macrophage polyclonal antibody (LIMPA) with or without different concentrations (2, 4, 6, 8, 10, 20, 40, 60, and 100 µg/ml) of CM11 and (40, 80, and 100 µg/ml) BufIIIb, two AMPs, in vitro and their therapeutic effects against CL of Balb/c mice. Results showed that LIMPA induced an anti-proliferative effect on Leishmania major growth in macrophages in vitro and intramacrophage-amastigotes in vivo. CM11 with IC50 of 8.73 and 10.10 μg/ml at 48 hours, and BufIIIb with IC50 of 66.83 and 80.26 μg/ml, at 24 hours showed the most significant inhibition of L. major promastigotes and amastigotes. In addition, the CM11 and BufIIIb, with a CC50 of 9.7 μg/ml and 40.34 μg/ml, showed the most significant inhibition effect on the J774.A1 cell line at 48 hours, respectively. In addition, in vivo experiments using LIMPA with a 0.01 mg/kg dosage showed a significant difference (p < 0.001) in the last week of the measurement compared to the control. The results of this study may be a promising prospect for further investigations.