Marius Belmondo Tincho

The absence of novel, safe, and effective bactericide is an urgent concern worldwide and remains a challenge in scientific communities. The unique proprieties of silver nanoparticles (SNPs) synthesized from plant extracts make them a suitable candidate to overcome these limitations. Herein, we synthesized SNPs from Bersama engleriana fruit (BEfr) extracts and determined their potential antibacterial activity and mode of action. SNPs were synthesized from BEfr methanolic fruit extracts at 25 and 70 °C, and the antibacterial effectiveness of SNPs against bacterial strains was investigated. The surface plasmon resonance peaked at 430.18 and 434.08 nm, respectively, for SNPs synthesized at 25 and 70 °C, confirming SNPs synthesis. BEfr-SNPs had minimum inhibitory concentrations (MIC) range of 0.234 to >50 µg/mL, which was 30-fold greater than extract alone (MIC of 500 µg/mL). BEfr-SNPs-25 °C was potent against six bacterial strains (S. aureus, S. enterica, MRS. aureus, K. pneumonia, and S. pyogenes), with MIC range of 0.339 to 6.25 µg/mL. The mode of action of BEfr-SNPs-25 °C was achieved by an MRSA bacteria strain outer membrane and DNA nucleotide linkage. These results suggest that our synthesized SNPs, especially BEfr-SNPs-25 °C, demonstrated an enhanced antibacterial effect and could be potential candidates for bacterial infection treatment.

In South Africa, high exposure to SARS-CoV-2 occurs primarily in densely populated, low-income communities, which are additionally burdened by highly prevalent Human Immunodeficiency Virus (HIV). With the aim to assess SARS-CoV-2 seroprevalence and its association with HIV-related clinical parameters in non-hospitalized patients likely to be highly exposed to SARS-CoV-2, this observational cross-sectional study was conducted at the Gugulethu Community Health Centre Antiretroviral clinic between October 2020 and June 2021, after the first COVID-19 wave in South Africa and during the second and beginning of the third wave. A total of 150 adult (median age 39 years [range 20–65 years]) HIV-infected patients (69% female; 31% male) were recruited. 95.3% of the cohort was on antiretroviral therapy (ART), had a median CD4 count of 220 cells/µL (range 17–604 cells/µL) and a median HIV viral load (VL) of 49 copies/mL (range 1–1,050,867 copies/mL). Furthermore, 106 patients (70.7%) were SARS-CoV-2 seropositive, and 0% were vaccinated. When stratified for HIV VL, patients with uncontrolled HIV viremia (HIV VL > 1000 copies/mL) had significantly higher odds of SARS-CoV-2 seropositivity than patients with HIV VL < 1000 copies/mL, after adjusting for age, sex and ART status (p = 0.035, adjusted OR 2.961 [95% CI: 1.078–8.133]). Although the cause–effect relationship could not be determined due to the cross-sectional study design, these results point towards a higher risk of SARS-CoV-2 susceptibility among viremic HIV patients, or impaired HIV viral control due to previous co-infection with SARS-CoV-2.

Cervical cancer is one of the most life-threatening malignancies worldwide, despite intensive research for more efficacious chemotherapeutic agents. Recent efforts geared towards eradicating the scourge of cancer have embodied a major surge of interest in natural products as promising lead molecules in pharmaceutical development and therapeutic translation. Consequently, this study aimed to assess the cytotoxicity of a previously identified plant Fraction (F3) from Bersama engleriana against cervical cancer (HeLa) cells and non-cancerous normal human foreskin fibroblasts (HFF cells). Flow cytometric analysis via Annexin V/PI in HeLa cells was carried out to assess apoptosis induction. We report here the 50% Inhibitory Concentration (IC₅₀) of fraction F3 to be 96.15 µg/mL and a 50% Cytotoxic Concentration (CC₅₀) of 527.4 µg/mL, as well as a Selectivity Index (SI) of 5.48, thus confirming that fraction F3 is relatively non-toxic to the normal cells compared to the cancer cells evaluated. In addition, microscopic observations showed a higher reduction of cells, aggregated with dark color in HeLa cells treated with fraction F3 compared to control (cells only). The Annexin V/PI analysis showed the percentages of apoptotic cells were 4.6±0.05, 7.9±0.9 and 7.6±0.15, respectively, for the control and treatments of cells with 120 and 150 µg/mL fraction F3 in early apoptosis (Annexin V+/PI-) 48 h post-treatment. Percentages of apoptotic cells were 2.1±0.1, 8.9±0.2 and 7.7±0.2, respectively, for control, 120 and 150 µg/mL fraction F3 treatments in late apoptosis (Annexin V+/PI+) after 48 h posttreatment. Nevertheless, a comparison of the lowest percentage inhibition of apoptosis with the highest number of reduced cells observed with fluorescence microscopy suggests that fraction F3 may exert its growth inhibitory action on HeLa cells via another mechanism. The results established that fraction F3 from B. engleriana is a promising source for exploring antitumor activity.

SARS-CoV-2 variants that escape neutralization and potentially affect vaccine efficacy have emerged. T cell responses play a role in protection from reinfection and severe disease, but the potential for spike mutations to affect T cell immunity is incompletely understood. We assessed neutralizing antibody and T cell responses in 44 South African COVID-19 patients either infected with the Beta variant (dominant from November 2020 to May 2021) or infected before its emergence (first wave, Wuhan strain) to provide an overall measure of immune evasion. We show that robust spike-specific CD4 and CD8 T cell responses were detectable in Beta-infected patients, similar to first-wave patients. Using peptides spanning the Beta-mutated regions, we identified CD4 T cell responses targeting the wild-type peptides in 12 of 22 first-wave patients, all of whom failed to recognize corresponding Beta-mutated peptides. However, responses to mutated regions formed only a small proportion (15.7%) of the overall CD4 response, and few patients (3 of 44) mounted CD8 responses that targeted the mutated regions. Among the spike epitopes tested, we identified three epitopes containing the D215, L18, or D80 residues that were specifically recognized by CD4 T cells, and their mutated versions were associated with a loss of response. This study shows that despite loss of recognition of immunogenic CD4 epitopes, CD4 and CD8 T cell responses to Beta are preserved overall. These observations may explain why several vaccines have retained the ability to protect against severe COVID-19 even with substantial loss of neutralizing antibody activity against Beta.

The SARS-CoV-2 Omicron variant (B.1.1.529) has multiple spike protein mutations^1,2 that contribute to viral escape from antibody neutralization^3–6 and reduce vaccine protection from infection^7,8. The extent to which other components of the adaptive response such as T cells may still target Omicron and contribute to protection from severe outcomes is unknown. Here we assessed the ability of T cells to react to Omicron spike protein in participants who were vaccinated with Ad26.CoV2.S or BNT162b2, or unvaccinated convalescent COVID-19 patients (n = 70). Between 70% and 80% of the CD4⁺ and CD8⁺ T cell response to spike was maintained across study groups. Moreover, the magnitude of Omicron cross-reactive T cells was similar for Beta (B.1.351) and Delta (B.1.617.2) variants, despite Omicron harbouring considerably more mutations. In patients who were hospitalized with Omicron infections (n = 19), there were comparable T cell responses to ancestral spike, nucleocapsid and membrane proteins to those in patients hospitalized in previous waves dominated by the ancestral, Beta or Delta variants (n = 49). Thus, despite extensive mutations and reduced susceptibility to neutralizing antibodies of Omicron, the majority of T cell responses induced by vaccination or infection cross-recognize the variant. It remains to be determined whether well-preserved T cell immunity to Omicron contributes to protection from severe COVID-19 and is linked to early clinical observations from South Africa and elsewhere^9–12.

Scientists have demonstrated the potential of plant materials as ‘green’ reducing and stabilizing agents for the synthesis of gold nanoparticles (AuNPs) and opened new ecofriendly horizons to develop effective and less harmful treatment strategies. The current study demonstrated the use of Terminalia mantaly (TM) extracts to synthesize AuNPs with enhanced cytotoxic effects. The TM-AuNPs were synthesized at 25 and 70 °C using water (_WTM) and methanolic (_MTM) extracts of the leaf, root and stem/bark parts of the plant. The TM-AuNPs were characterized using UV–visible spectrophotometry, dynamic light scattering (DLS), transmission electron microscopy, energy dispersive X-ray (EDX), selection area electron diffraction (SAED) and Fourier transform infrared (FTIR) spectroscopy. Majority of the TM-AuNPs were spherical with a mean diameter between 22.5 and 43 nm and were also crystalline in nature. The cytotoxic effects of TM-AuNPs were investigated in cancer (Caco-2, MCF-7 and HepG2) and non-cancer (KMST-6) cell lines using the MTT assay. While the plant extracts showed some cytotoxicity towards the cancer cells, some of the TM-AuNPs were even more toxic to the cells. The IC₅₀ values (concentrations of the AuNPs that inhibited 50% cell growth) as low as 0.18 µg/mL were found for TM-AuNPs synthesized using the root extract of the plant. Moreover, some of the TM-AuNPs demonstrated selective toxicity towards specific cancer cell types. The study demonstrates the potential of TM extracts to produce AuNPs and describe the optimal conditions for AuNPs using TM extracts. The toxicity of some the TM-AuNPs can possibly be explored in the future as an antitumor treatment.

Endophytic fungi are potential sources of novel bioactive metabolites from a natural product drug discovery perspective. This study reports the bioactivity-directed fractionation of the secondary metabolites of the ethyl acetate extract of a fermentation culture of endophytic fungi from Terminalia catappa which were then evaluated for their cytotoxicity against human cervical cancer (HeLa) cells and human foreskin fibroblast (HFF) cells. Furthermore, apoptosis was determined using the Annexin V/propidium iodide (PI) flow cytometry assay. Endophyte extracts N2, N7, N8, N97, N169, and N233 were obtained from Trichoderma sp, Phoma sp, Phomopsis phyllanticola, Fusarium oxyporum, Collectotrichum sp, and Cryptococcus flavescens, respectively. The N97 extract was most active with a 50% inhibitory concentration (IC₅₀) of 33.35 µg/ml. A 50% cytotoxic concentration (CC₅₀) of 268.4 µg/ml was obtained with HFF cells and the selectivity index (SI) was 8.01. The percentages of cell populations were increased at late apoptosis (Annexin+/PI+), with the percentages of 27.4 ± 0.3 and 19.2 ± 0.01 obtained, respectively, for 50 µg/ml and 80 µg/ml of the N97 extract and 2.1 ± 0.1 obtained for the control in late apoptosis (Annexin V+/PI+) . Moreover, a higher reduction in the percentage of viable cells was observed in the HeLa control cells (93.6 ± 0.3), but the percentages of viable HeLa cells were 37 ± 0.05 and 45 ± 0.1, respectively, for the 50 µg/ml and 80 µg/ml treatments with the N97 extract. Also, the percentages of 34.7 ± 0.1 and 33.9 ± 0.4 were, respectively, obtained for 50 µg/ml and 80 µg/ml compared to the control with 4.6 ± 0.2, in early apoptosis (Annexin V+/PI-). These findings highlight the anticancer potential of the N97 extract of endophytic fungi from Terminalia catappa, which is mediated through apoptosis and presumably also attenuation of chemoresistance.