The use of Toxoplasma gondii tachyzoites produced in HeLa cells adhered to Cytodex 1 microcarriers as antigen in serological assays: an application of microcarrier technology

Anti-parasitic activity of a chimeric peptide Cecropin A (2-8)-Melittin (6-9) (CM11) against tachyzoites of Toxoplasma gondii and the BALB/c mouse model of acute toxoplasmosis

Toxoplasmosis is a zoonotic disease that infects most animals, including humans. Pyrimethamine/sulfadiazine is the standard treatment for toxoplasmosis. Although this treatment has been successful, it is often associated with side effects that cannot be tolerated. Therefore, various compounds have been proposed as alternative treatments for toxoplasmosis. Antimicrobial peptides (AMPs) act on various pathogens, from viruses to protozoa. The purpose of the present study was to evaluate the effects of CM11 on in vitro and in vivo Toxoplasma gondii infection. For in vitro experiments, VERO cells were treated with different concentrations of CM11 (1-128 μg/ml) compared to sulfadiazine (SDZ) (0.78-100 μg/ml). MTT and lactate dehydrogenase (LDH) assays evaluated the cell viability and plasma membrane integrity. Then, the inhibitory concentration (IC50) values were determined for treating tachyzoites of T. gondii before or on cells previously infected. Annexin V-FITC/propidium iodide (PI) staining was used to distinguish viable and apoptotic cells. The effect of CM11, SDZ, and a combination of CM11 and SDZ was evaluated in the BALB/c mouse model of acute toxoplasmosis. CM11 was effective on tachyzoites of T. gondii and had a time and dose-dependent manner. The results of the MTT assay showed that the CC50 values of CM11 and SDZ were estimated at 17.4 µg/ml and 62.3 µg/ml after 24-h, respectively. The inhibitory concentration (IC50) of CM11 and SDZ on infected cells was estimated at 1.9 µg/ml and 1.4 µg/ml after 24-h, respectively. The highest rate of apoptosis (early and late) in high concentrations of SDZ and CM11 was determined for tachyzoites (2.13 % and 13.88 %), non-infected VERO cells (6.1 % and 19.76 %), and infected VERO cells (7.45 % and 29.9 %), respectively. Treating infected mice with CM11 and a combination of CM11 and SDZ had increased survival time. Based on the mentioned results, it can be concluded that CM11 has a beneficial effect on tachyzoites of T. gondii in vitro. The result of the mouse model suggests that CM11, either alone or in combination with other chemotherapeutic agents, could be a potential therapeutic for toxoplasmosis. Hence, antimicrobial peptides could be applied as promising anti-toxoplasma agents for treating toxoplasmosis.

Thermo/redox-responsive dissolvable gelatin-based microsphere for efficient cell harvesting during 3D cell culturing

The use of microspheres for culturing adherent cells has been proven as an important method, allowing for obtaining adequate number of cells in limited space and volume of medium for the intended cell-based medical applications. However, the use of proteolytic enzymes for cell harvesting from the microsphere resulted in cell damage and loss of functionality. Therefore, in this study, we developed a novel redox/thermo-responsive dissolvable gelatin-based microsphere for successful cell proliferation and harvesting adequate high-quality cells using non-enzymatic cell detachment methods. Initially, a redox-induced dissolvable gelatin-based microsphere was successfully prepared using disulfide bonds as crosslinking agent, firmly stabilizing gelatin networks and forming a stable microsphere at physiological temperature. The optimized concentration of the crosslinking agent was 1.2 mM, which kept the microsphere stable for >120 h. The microsphere was then coated with PNIPAm-ALA copolymer via physical or chemical means, resulting in a positively charged thermosensitive surface. The positive charge derived from ALA in PNIPAm-ALA copolymer enhanced cell attachment, while the thermosensitive property of the copolymer enabled for temperature induced cell harvesting. When the temperature dropped below the LCST value of PNIPAm-ALA₅ (33.4°C), the copolymer swelled and became more hydrophilic, allowing cells to be readily separated. The addition of reducing agents such as GSH, DTT and L-cysteine resulted in further cleavage of the disulfide bond in the microsphere and dissolution of the microsphere for complete cell detachment. Interestingly, cell attachment and proliferation were enhanced on microspheres coated with PNIPAm-ALA₅ using diselenide as a crosslinking agent, and complete cell detachment was occurred within 15 min after adding 25 mM DTT followed by lowering the temperature (4°C). Therefore, the microsphere fabricated in this study was worthwhile for non-enzymatic cell detachment and has the potential to be used for cell expansion and harvesting adequate live cells of high quality and functionality for tissue engineering or cell therapy.

The Truman Show for protozoan parasites: A review of in vitro cultivation platforms

Protozoan parasites are responsible for severe disease and suffering in humans worldwide. Apart from disease transmission via insect vectors and contaminated soil, food, or water, transmission may occur congenitally or by way of blood transfusion and organ transplantation. Several recent outbreaks associated with fresh produce and potable water emphasize the need for vigilance and monitoring of protozoan parasites that cause severe disease in humans globally. Apart from the tropical parasite Plasmodium spp., other protozoa causing debilitating and fatal diseases such as Trypanosoma spp. and Naegleria fowleri need to be studied in more detail. Climate change and socioeconomic issues such as migration continue to be major drivers for the spread of these neglected tropical diseases beyond endemic zones. Due to the complex life cycles of protozoa involving multiple hosts, vectors, and stringent growth conditions, studying these parasites has been challenging. While in vivo models may provide insights into host–parasite interaction, the ethical aspects of laboratory animal use and the challenge of ready availability of parasite life stages underline the need for in vitro models as valid alternatives for culturing and maintaining protozoan parasites. To our knowledge, this review is the first of its kind to highlight available in vitro models for protozoa causing highly infectious diseases. In recent years, several research efforts using new technologies such as 3D organoid and spheroid systems for protozoan parasites have been introduced that provide valuable tools to advance complex culturing models and offer new opportunities toward the advancement of parasite in vitro studies. In vitro models aid scientists and healthcare providers in gaining insights into parasite infection biology, ultimately enabling the use of novel strategies for preventing and treating these diseases.

In light of the far-reaching social and economic repercussions of communicable, zoonotic parasitic diseases on human health, it is imperative to continue to strive toward developing in vitro models for in-depth scrutiny and understanding of pathogenicity, as well as for innovations toward combating these infections. This review, to our knowledge, is the first to offer a qualitative summary of the existing models for culturing protozoan parasites with major relevance to human health in vitro. The present work aims to provide a reference guide on the current state of in vitro culture of these protozoan parasites and offers a foundation to facilitate exchange of expertise among researchers, clinicians, and healthcare workers. This comprehensive review would aid in enabling discussions on new intervention approaches to fill in the knowledge gaps in the field of parasitic diseases affecting the global population.