Optimization of the heterologous expression and purification of Plasmodium falciparum generative cell specific 1 in Escherichia coli

MAM7 from Vibrio parahaemolyticus: Expression, purification and effects on RAW264.7 cells

V. parahaemolyticus is a Gram-negative bacterium that causes gastroenteritis. Within the realm of bacterial interactions with the gut, the outer membrane protein MAM7 plays a key role. However, the precise function of MAM7 in intestinal inflammation, particularly its interactions with macrophages, remains unclear. In this study, we successfully expressed and purified recombinant MAM7. After optimization of the MAM7 expression condition, it was found that the optimal concentration and temperature were 0.75 mM and 15 °C, respectively, resulting in a 27-fold increase in its yield. Furthermore, RAW264.7 cytotoxicity assay was conducted. The CCK-8 results revealed that MAM7 substantially stimulated the proliferation of RAW264.7 cells, with its optimal concentration determined to be 7.5 μg/mL. Following this, the NO concentration of MAM7 was tested, revealing a significant increase (p < 0.05) in NO levels. Additionally, the relative mRNA levels of IL-1β, IL-6, and TNF-α in RAW264.7 cells were measured by qRT-PCR, showing a remarkable elevation (p < 0.05). Moreover, ELISA results demonstrated that MAM7 effectively stimulated the secretion of IL-6 and TNF-α by RAW264.7 cells. In summary, these findings strongly suggest that MAM7 serves as a proinflammatory adhesion factor with the capacity to modulate immune responses.

Optimized Refolding Buffers Oriented Humoral Immune Responses Versus PfGCS1 Self-Assembled Peptide Nanoparticle

Developing a novel class of vaccine is pivotal for eliminating and eradicating malaria. Preceding investigations demonstrated partial blocking activity in malaria transmission against recombinant vaccine PfHAP2-GCS1 and conserved region of the cd loop. The effectiveness of immune response varies with the size and shape of the self-assembly of peptide nanoparticles (SAPNs) displaying antigen, affected by different components in refolding buffers. Plasmodium falciparum Generative Cell Specific 1 (PfGCS1), a promising malaria transmission-blocking vaccine (TBV) candidate, was expressed, purified, and followed by a four-step refolding process to form nanoparticles (PfGCS1-SAPNs). The influence of buffer components on the size and shape of SAPNs was investigated by DLS and FESEM. Furthermore, the immunogenicity of nanostructures was assessed in different mouse groups. The results showed that PfGCS1-SAPN was immunogenic and its administration with Poly (I:C), stimulated humoral and cellular responses in the mouse model. In the immunized mice groups, the level of IgG antibodies against PfGCS1-SAPN was significantly increased in different time points (second and third boost) and heterogeneous boosters. The various IgG-subclasses profile shifted to Th1, Th2, or Th1/Th2 mix responses in mice immunized with PfGCS1-SAPN refolded in different buffers, indicating a prerequisite for further investigations to optimize vaccine formulation to enhance and modulate Th1/cellular responses. Such studies pave the way to improve biophysical features related to the nanoparticles' size, shape, and conformational epitopes of candidate antigens and T- and B-cells presented on the superficial structure to elicit robust immune responses.

Optimizing recombinant antibody fragment production: A comparison of artificial intelligence and statistical modeling

Maximizing the recombinant protein yield necessitates optimizing the production medium. This can be done using a variety of methods, including the conventional "one-factor-at-a-time" approach and more recent statistical and mathematical methods such as artificial neural network (ANN), genetic algorithm, etc. Every approach has advantages and disadvantages of its own, yet even when a technique has flaws, it is nevertheless used to get the best results. Here, one categorical variable and four numerical parameters, including post-induction time, inducer concentration, post-induction temperature, and pre-induction cell density, were optimized using the 232 experimental assays of the central composite design. The direct and indirect effects of factors on the yield of anti-epithelial cell adhesion molecule extracellular domain fragment antibody were examined using statistical methods. The analysis of variance results indicate that the response surface methodology (RSM) model is effective in predicting the amount of produced single-chain fragment variable (p-value = 0.0001 and R2 = 0.905). For ANN modeling, the evaluation using normalized root mean square error (NRMSE) and R2 values shows a good fit (R2 = 0.942) and accurate predictions (NRMSE = 0.145). The analysis of error parameters and R2 of a dataset, which contained 30 data points randomly selected from the complete dataset, showed that the ANN model had a higher R2 value (0.968) compared to the RSM model (0.932). Furthermore, the ANN model demonstrated stronger predictive ability with a lower NRMSE (0.048 vs. 0.064). Induction at the cell density of 0.7 and an isopropyl β-D-1-thiogalactopyranoside concentration of 0.6 mM for 32 h at 30°C in BW25113 was the ideal culture condition leading to the protein yield of 259.51 mg/L. Under the optimum conditions, the output values predicted by the ANN model (259.83 mg/L) were more in line with the experimental data (259.51 mg/L) than the RSM (276.13 mg/L) expected value. This outcome demonstrated that the ANN model outperforms the RSM in terms of prediction accuracy.

Design and development of a self-assembling protein nanoparticle displaying PfHAP2 antigenic determinants recognized by natural acquired antibodies

Backgrounds

In order to move towards the elimination and eradication of malaria in the world, the development of vaccines is inevitable. Many modern vaccines are based on recombinant technology; however, they may not provide a fully protective, long-lasting immune response. One of the strategies to improve recombinant vaccines is designing the nanovaccines such as self-assembling protein nanoparticles (SAPNs). Hence, the presentation of epitopes in a repeat array and correct conformation should be considered. P. falciparum generative cell-specific 1 (PfGCS1) is a main transmission-blocking vaccine candidate with two highly conserved fragments, HAP2-GCS1 and cd loop, inducing partial malaria transmission inhibitory antibodies. Therefore, to design an effective malaria vaccine, we used cd loop and HAP2-GCS1 fragments at the amino and carboxy terminuses of the SAPN-forming amino acid sequence, respectively.

Methodology/Principal findings

The SAPN monomer (PfGCS1-SAPN) sequence was designed, and the three-dimensional (3D) structure was predicted. The result of this prediction ensured the presence of antigens on the SAPN surface. Then the accuracy of the predicted 3D structure and its stability were confirmed by 100 ns molecular dynamics (MD) simulation. The designed SAPN substructure sequence was synthesized, cloned, and expressed in Escherichia coli. With a gradual decrease in urea concentration in dialysis solutions, the purified proteins progressed to the final desired structure of the SAPN, which then was confirmed by Dynamic Light Scattering (DLS) and Field Emission Scanning Electron Microscopy (FESEM) tests. According to the Enzyme-Linked Immunosorbent Assay (ELISA), antigenic determinants were presented on the SAPN surface and interacted with antibodies in the serum of malaria patients.

Conclusions/Significance

Our results show that the SAPN formed by PfGCS1-SAPN has produced the correct shape and size, and the antigenic determinants are presented on the surface of the SAPN, which indicates that the designed SAPN has great potential to be used in the future as a malaria vaccine.