An Overview of Repurposed Drugs for Potential COVID-19 Treatment.

The COVID-19 pandemic caused by SARS-CoV-2 has placed severe constraints on healthcare systems around the globe. The SARS-CoV-2 virus has caused upheaval in the healthcare and economic sectors worldwide. On the 20th of May 2020, the World Health Organisation declared COVID-19 a global pandemic due to the unprecedented number of cases reported around the globe. As of the 4th of November 2022, there were 637,117,429 coronavirus cases reported globally by Worldometer stats, with 6,602,572 related deaths. In South Africa, there were approximately 4,029,496 coronavirus cases and 102,311 associated deaths. As such, there is a need for efficacious therapeutic regimes. There has been a paucity of knowledge encompassing the use of effective and specific antiviral drug therapies for treating COVID-19 since the outbreak. In this review, we provide valuable insights into the repurposing of current drugs for COVID-19. Drug repurposing provides a suitable option for the discovery of efficacious drugs for COVID-19, thereby decreasing the costs and turnaround times of drug development strategies. This review provides an overview of ten drugs, including antimalarial, antiparasitic, anti-inflammatory, nucleoside analogue, monoclonal-antibody drugs, that were repurposed for the potential treatment of COVID-19.

Detection of Insect-Specific Flaviviruses in Mosquitoes (Diptera: Culicidae) in Northeastern Regions of South Africa.

Mosquitoes in the Aedes and Culex genera are considered the main vectors of pathogenic flaviviruses worldwide. Entomological surveillance using universal flavivirus sets of primers in mosquitoes can detect not only pathogenic viruses but also insect-specific ones. It is hypothesized that insect-specific flaviviruses, which naturally infect these mosquitoes, may influence their vector competence for zoonotic arboviruses. Here, entomological surveillance was performed between January 2014 and May 2018 in five different provinces in the northeastern parts of South Africa, with the aim of identifying circulating flaviviruses. Mosquitoes were sampled using different carbon dioxide trap types. Overall, 64,603 adult mosquitoes were collected, which were screened by RT-PCR and sequencing. In total, 17 pools were found positive for insect-specific Flaviviruses in the mosquito genera Aedes (12/17, 70.59%) and Anopheles (5/17, 29.41%). No insect-specific viruses were detected in Culex species. Cell-fusing agent viruses were detected in Aedes aegypti and Aedes caballus. A range of anopheline mosquitoes, including Anopheles coustani, An. squamosus and An. maculipalpis, were positive for Culex flavivirus-like and Anopheles flaviviruses. These results confirm the presence of insect-specific flaviviruses in mosquito populations in South Africa, expands their geographical range and indicates potential mosquito species as vector species.

Potential of brain mast cells for therapeutic application in the immune response to bacterial and viral infections.

A wide range of microorganisms can infect the central nervous system (CNS). The immune response of the CNS provides limited protection against microbes penetrating the blood-brain barrier. This results in a neurological deficit and sometimes leads to high morbidity and mortality rates despite advanced therapies. For the last two decades, different studies have expanded our understanding of the molecular basis of human neuroinfectious diseases, especially concerning the contributions of mast cell interactions with other central nervous system compartments. Brain mast cells are multifunctional cells derived from the bone marrow and reside in the brain. Their proximity to blood vessels, their role as "first responders" their unique receptors systems and their ability to rapidly release pathogen responsive mediators enable them to exert a crucial defensive role in the host-defense system. This review describes key biological and physiological functions of mast cells, concerning their ability to recognize pathogens via various receptor systems, followed by a coordinated and selective mediator release upon specific interactions with pathogenic stimulating factors. The goal of this review is to direct attention to the possibilities for therapeutic applications of mast cells against bacterial and viral related infections. We also focus on opportunities for future research activating mast cells via adjuvants.

The development of a sub/supercritical fluid chromatography based purification method for peptides.

Peptide drugs are essential components of the pharmaceutical industry with a multiplicity of therapeutic properties, such as being anti-hypertensive, anti-microbial, anti-diabetic, and having anti-cancer potential. These molecules are similar in physiological structure and function to the body's endogenous signalling molecules and are therefore ideal candidates for the development of the next-generation of drugs. However, the purification of these peptides can be problematic due to poor solubility and stability, which often results in low peptide yields. Peptides are traditionally purified via RP-HPLC methods, which are tedious and employ harsh solvents that generate harmful waste to the environment. There is a growing need for more cost-effective and sustainable purification methods of these biologics. SFC can provide a greener peptide purification approach with more environmentally friendly mobile phases such as CO2 and methanol, which can easily be recycled with minimal environmental impact. Currently, there is limited knowledge regarding the SFC purification of peptides. Herein, this study investigated SFC methods to purify a tetrapeptide (LYLV), octapeptide (DRVYIHPF), and nonapeptide (LYLVCGERG) on commercially available columns at an analytical scale. The 2-ethyl pyridine column proved to be optimal based on its reproducibility, peak shapes, efficient separations, and retention factors with peptide recoveries ranging from 80 to 102%. The run times were reduced to 13 min, as opposed to the traditional RP-HPLC methods of 50 min, thus making this SFC method an efficient, greener, and more cost-effective approach for the purification of these peptides.

Sub/supercritical fluid chromatography employing water-rich modifier enables the purification of biosynthesized human insulin.

There is a paucity of knowledge surrounding the SFC purification of human insulin. The current conventional method of insulin purification involves traditional RP-HPLC that utilises copious amounts of toxic solvents. In this study, we envisaged the development of an environmentally friendly SFC method for biosynthesized human insulin purification. Various commercially available SFC columns derived with silica, 2'ethyl pyridine, diol-HILIC, and the PFP functionalities were evaluated to determine the optimal stationary phase for purification. The PFP column gave the best results with respect to efficiencies of this important biologic that yielded average recoveries of 84%. LC-MS was used to initially detect and quantify the SFC purified standard sample of insulin (purchased) as well as the biosynthesized version. Protein sequencing was employed to verify the amino acid sequencing of the insulins; as such, the standard had a 90% probability to human insulin from the database, whereas the biosynthesized version had a 96% probability. The biological activities of both versions of the SFC purified proteins were assessed in vitro using a MTT assay. The results indicated that the biological activities of both samples were retained subsequent to SFC purification. This study successfully proposes a greener and more efficient method for the purification of insulin derivatives.

A novel and more efficient biosynthesis approach for human insulin production in Escherichia coli (E. coli).

Insulin has captured researchers' attention worldwide. There is a rapid global rise in the number of diabetic patients, which increases the demand for insulin. Current methods of insulin production are expensive and time-consuming. A PCR-based strategy was employed for the cloning and verification of human insulin. The human insulin protein was then overexpressed in E. coli on a laboratory scale. Thereafter, optimisation of human insulin expression was conducted. The yield of human insulin produced was approximately 520.92 (mg/L), located in the intracellular fraction. Human insulin was detected using the MALDI-TOF-MS and LC-MS methods. The crude biosynthesised protein sequence was verified using protein sequencing, which had a 100% similarity to the human insulin sequence. The biological activity of human insulin was tested in vitro using a MTT assay, which revealed that the crude biosynthesised human insulin displayed a similar degree of efficacy to the standard human insulin. This study eliminated the use of affinity tags since an untagged pET21b expression vector was employed. Tedious protein renaturation, inclusion body recovery steps, and the expensive enzymatic cleavage of the C-peptide of insulin were eliminated, thereby making this method of biosynthesising human insulin a novel and more efficient method.