The state of gene therapy research in Africa, its significance and implications for the future.

Gene therapy has made impressive recent progress and has potential for treating a wide range of diseases, many of which are important to Africa. However, as a result of lack of direct public funding and skilled personnel, direct research on gene therapy in Africa is currently limited and resources to support the endeavor are modest. A strength of the technology is that it is based on principles of rational design, and the tools of gene therapy are now highly versatile. For example gene silencing and gene editing may be used to disable viral genes for therapeutic purposes. Gene therapy may thus lead to cure from infections with HIV-1, hepatitis B virus and Ebola virus, which are of significant public health importance in Africa. Although enthusiasm for gene therapy is justified, significant challenges to implementing the technology remain. These include ensuring efficient delivery of therapeutic nucleic acids to target cells, limiting unintended effects, cost and complexity of treatment regimens. In addition, implementation of effective legislation that will govern gene therapy research will be a challenge. Nevertheless, it is an exciting prospect that gene therapy should soon reach the mainstream of medical management. Participation of African researchers in the exciting developments is currently limited, but their involvement is important to address health problems, develop capacity and enhance economic progress of the continent.

Pharmacogenetic comparison of CYP2D6 predictive and measured phenotypes in a South African cohort.

This corrects the article DOI: 10.1038/tpj.2015.76.

Pharmacogenetic comparison of CYP2D6 predictive and measured phenotypes in a South African cohort.

The relationship between genetic variation in CYP2D6 and variable drug response represents a potentially powerful pharmacogenetic tool. However, little is known regarding this relationship in the genetically diverse South African population. The aim was therefore to evaluate the relationship between predicted and measured CYP2D6 phenotype. An XL-PCR+Sequencing approach was used to determine CYP2D6 genotype in 100 healthy volunteers and phenotype was predicted using activity scores. With dextromethorphan as the probe drug, metabolic ratios served as a surrogate measure of in vivo CYP2D6 activity. Three-hour plasma metabolic ratios of dextrorphan/dextromethorphan were measured simultaneously using semi-automated online solid phase extraction coupled with tandem mass spectrometry. Partial adaptation of the activity score system demonstrated a strong association between genotype and phenotype, as illustrated by a kappa value of 0.792, inter-rater discrepancy of 0.051 and sensitivity of 72.7%. Predicted phenotype frequencies using the modified activity score were 1.3% for poor metabolisers (PM), 7.6% for intermediate metabolisers (IM) and 87.3% for extensive metabolisers (EM). Measured phenotype frequencies were 1.3% for PM, 13.9% for IM and 84.8% for EM. Comprehensive CYP2D6 genotyping reliably predicts CYP2D6 activity in this South African cohort and can be utilised as a valuable pharmacogenetic tool.

Mesenchymal Stromal Cells: a Possible Reservoir for HIV-1?

The introduction of antiretroviral therapy (ART) and highly active antiretroviral therapy (HAART) has transformed human immunodeficiency virus (HIV)-1 into a chronic, well-managed disease. However, these therapies do not eliminate all infected cells from the body despite suppressing viral load. Viral rebound is largely due to the presence of cellular reservoirs which support long-term persistence of HIV-1. A thorough understanding of the HIV-1 reservoir will facilitate the development of new strategies leading to its detection, reduction, and elimination, ultimately leading to curative therapies for HIV-1. Although immune cells derived from lymphoid and myeloid progenitors have been thoroughly studied as HIV-1 reservoirs, few studies have examined whether mesenchymal stromal/stem cells (MSCs) can assume this function. In this review, we evaluate published studies which have assessed whether MSCs contribute to the HIV-1 reservoir. MSCs have been found to express the receptors and co-receptors required for HIV-1 entry, albeit at levels of expression and receptor localisation that vary considerably between studies. Exposure to HIV-1 and HIV-1 proteins alters MSC properties in vitro, including their proliferation capacity and differentiation potential. However, in vitro and in vivo experiments investigating whether MSCs can become infected with and harbour latent integrated proviral DNA are lacking. In conclusion, MSCs appear to have the potential to contribute to the HIV-1 reservoir. However, further studies are needed using techniques such as those used to prove that cluster of differentiation (CD)4+ T cells constitute an HIV-1 reservoir before a reservoir function can definitively be ascribed to MSCs. MSCs may contribute to HIV-1 persistence in vivo in the vasculature, adipose tissue, and bone marrow by being a reservoir for latent HIV-1. To harbour latent HIV-1, MSCs must express HIV-1 entry markers, and show evidence of productive or latent HIV-1 infection. The effect of HIV-1 or HIV-1 proteins on MSC properties may also be indicative of HIV-1 infection.

Regenerative medicines: A new regulatory paradigm for South Africa.

Clinicians are increasingly using regenerative medicines to repair, replace, regenerate or rejuvenate lost, damaged or diseased genes, cells, tissues or organs. In South Africa, access to these novel gene therapies and cell and tissue-based products is limited. The human leukocyte antigen (HLA) diversity and a paucity of suitable HLA-identical unrelated donors, results in limited access to haematopoietic stem and progenitor cell transplantation (HSPCT). Cell-based products could increase this access. Genetic diversity can also manifest in local or region-specific rare congenital disorders, and in vivo gene therapies hold the promise of developing treatments and cures for these debilitating disorders. South Africa has a disproportionate mortality rate due to non-natural causes, with many surviving with permanent injuries and disabilities. Tissue-engineered cell-based products have the potential to restore many of those affected and improve quality of life and productivity. These factors create an urgency for South Africa to develop regenerative medicines to address the country's unique needs and to provide access to these new and innovative treatment modalities. Achieving this objective requires a well-coordinated effort by multiple stakeholders and role players. A critical component of a regenerative medicine ecosystem is establishing an enabling regulatory framework for these new classes of medicines. Here we provide a brief profile of South Africa, including its genetic diversity, economy, the impact of the burden of disease, health policy and the healthcare system. We address the regulation of medicines, how the existing framework can accommodate regenerative medicines, and the steps needed to establish a future regulatory framework.

When cells become medicines: A South African perspective.

The discovery of human leucocyte antigen (HLA), serological matching and HLA-typing techniques, combined with the development of immunosuppressive medicines and improvements in infection control, have opened the way to cell, tissue and vascularised organ transplantation. Since the early 1960s, more than a million haematopoietic progenitor cell (HPC) transplantations have been performed worldwide to restore haematopoiesis and support immune system recovery after bone marrow ablation. HPC transplantation uses minimally manipulated autologous or allogeneic cells to restore the homologous functions of bone marrow. Research in biological sciences supported by new technologies is increasingly translated into therapeutic products intended to augment, repair, replace or regenerate genes, cells, tissues, organs and metabolic processes in the body. These products are referred to as regenerative medicine therapies or advanced therapy medicinal products, and include gene therapies, cell-based therapies and engineered tissue products.

Viruses, variants and vaccines.

The current SARS-CoV-2 pandemic has brought a number of major global clinical, sociological and economic issues into sharp focus. We address some of these issues, focusing on short-term factors such as virus mutations and vaccine efficacy, and also considering the longer-term implications of the current pandemic. We discuss societal responses to the presence of a pathogen that will probably remain in circulation for decades or longer, and to future new emergent viruses.

Thrombospondin-1 is downregulated by anoxia and suppresses tumorigenicity of human glioblastoma cells.

Angiogenesis, the sprouting of new capillaries from preexisting blood vessels, results from a disruption of the balance between stimulatory and inhibitory factors. Here, we show that anoxia reduces expression of thrombospondin-1 (TSP-1), a natural inhibitor of angiogenesis, in glioblastoma cells. This suggests that reduced oxygen tension can promote angiogenesis not only by stimulating the production of inducers, such as vascular endothelial growth factor, but also by reducing the production of inhibitors. This downregulation may significantly contribute to glioblastoma development, since we show that an increase in TSP-1 expression is sufficient to strongly suppress glioblastoma cell tumorigenicity in vivo.

The impact of obesity on the cellular and molecular pathophysiology of COVID-19.

Emerging evidence reveals a strong association between COVID-19 and obesity in terms of disease severity, need for hospitalisation and risk of mortality. In this review, we discuss cellular and molecular mechanisms potentially contributing to the pathophysiology of COVID-19 in obese patients. Understanding the relationship between COVID-19 and obesity is pertinent for the clinical management of these patients.

Rapid evolution of our understanding of the pathogenesis of COVID-19: Implications for therapy.

COVID-19 severity appears to lie in its propensity to cause a hyperinflammatory response, attributed to the cytokine release syndrome (CRS) or 'cytokine storm', although the exact role of the CRS remains to be fully elucidated. Hyperinflammation triggers a hypercoagulable state, also thought to play a key role in COVID-19 pathogenesis. Disease severity is linked to age, sex and comorbid conditions, which in turn may be linked to oxidative stress and pre-existing depletion of nicotinamide adenine dinucleotide (NAD+). There is increasing evidence that the host genome may determine disease outcome. Since most information pertaining to COVID-19 has thus far been extrapolated from the 'global North', similar studies in African populations are warranted. Many studies are aimed at finding a therapeutic strategy based on scientific rationale. Some promising results have emerged, e.g. the use of corticosteroids in severe acute respiratory distress syndrome (ARDS).

Research in COVID-19 times: The way forward.

The COVID-19 pandemic has had a major impact on research at universities. Universities around the world, including in South Africa, have been or are still closed as part of national lockdown strategies. Students have not been attending classes or doing hands-on experimental work, and students and academics have been working from home. Many thousands of students have had their university education interrupted, and for them, the resumption of learning programmes online, and where possible in research laboratories, is critically important. There is no question that as we emerge from lockdown we will not be entering a world that resembles a 'norm' as lived in the pre-COVID-19 era, and many changes will be required. Here we discuss the importance of research, the urgency to get things up and running again, and strategies that will need to be implemented to ensure that research activities continue. At the same time, it is necessary to ensure that students and staff are not exposed to risk in their research endeavours, which will require the development and implementation of risk management plans.

The impact of obesity on the cellular and molecular pathophysiology of COVID-19.

Emerging evidence reveals a strong association between COVID-19 and obesity in terms of disease severity, need for hospitalisation and risk of mortality. In this review, we discuss cellular and molecular mechanisms potentially contributing to the pathophysiology of COVID-19 in obese patients. Understanding the relationship between COVID-19 and obesity is pertinent for the clinical management of these patients.

A prospective observational study of developmental outcomes in survivors of neonatal hypoxic ischaemic encephalopathy in South Africa.

BACKGROUND: Neonatal hypoxic ischaemic encephalopathy (NHIE) is an important cause of long-term handicap in survivors. There is limited information on the burden of handicap from NHIE in sub-Saharan Africa. OBJECTIVES: To determine the developmental outcomes in survivors of NHIE in South Africa (SA). METHODS: In this prospective observational study, the developmental outcomes in 84 infants who had survived hypoxic ischaemic encephalopathy (the NHIE group) were compared with those in 64 unaffected infants (the control group). The Bayley Scales of Infant Development version III were used for assessment of developmental outcomes. RESULTS: Significant differences were found between the developmental outcomes of the two groups, with a significantly lower composite language score and higher proportions with language, motor and cognitive developmental delays in the NHIE group than in the control group. Cerebral palsy (CP) was present in 13 of the infants with NHIE (15.5%) and none in the control group (p<0.001). CP was associated with developmental delay, and also with the severity of NHIE. Therapeutic hypothermia (TH) was administered in 58.3% of the study group, but although it was associated with lower rates of CP and developmental delay than in the group without TH, the only significant difference was for delay on the language subscale. CONCLUSIONS: Survivors of NHIE in SA are at risk of poor developmental outcomes.

Privacy rights of human research participants in South Africa must be taken seriously.

Letter by Thaldar and Townsend, following an article by the same authors (Thaldar D, Townsend B. Genomic research and privacy: A response to Staunton et al. S Afr Med J 2020;110(3):172-174. https://doi.org/10.7196/SAMJ.2020.v110i3.14431) and both commenting on an article by Staunton et al. (Staunton C, Adams R, Botes M, et al. Safeguarding the future of genomic research in South Africa: Broad consent and the Protection of Personal Information Act No. 4 of 2013. S Afr Med J 2019;109(7):468-470. https://doi.org/10.7196/SAMJ.2019.v109i7.14148); and response to article and letter by Staunton et al.

Urokinase-type plasminogen activator is induced in migrating capillary endothelial cells.

Cellular migration is an essential component of invasive biological processes, many of which have been correlated with an increase in plasminogen activator production. Endothelial cell migration occurs in vivo during repair of vascular lesions and angiogenesis, and can be induced in vitro by wounding a confluent monolayer of cells. By combining the wounded monolayer model with a substrate overlay technique, we show that cells migrating from the edges of an experimental wound display an increase in urokinase-type plasminogen activator (uPA) activity, and that this activity reverts to background levels upon cessation of movement, when the wound has closed. Our results demonstrate a direct temporal relationship between endothelial cell migration and uPA activity, and suggest that induction of uPA activity is a component of the migratory process.

Transforming growth factor-beta 1 modulates basic fibroblast growth factor-induced proteolytic and angiogenic properties of endothelial cells in vitro.

Tightly controlled proteolytic degradation of the extracellular matrix by invading microvascular endothelial cells is believed to be a necessary component of the angiogenic process. We have previously demonstrated the induction of plasminogen activators (PAs) in bovine microvascular endothelial (BME) cells by three agents that induce angiogenesis in vitro: basic FGF (bFGF), PMA, and sodium orthovanadate. Surprisingly, we find that these agents also induce plasminogen activator inhibitor-1 (PAI-1) activity and mRNA in BME cells. We also find that transforming growth factor-beta 1 (TGF-beta 1), which in vitro modulates a number of endothelial cell functions relevant to angiogenesis, also increases both PAI-1 and urokinase-type PA (u-PA) mRNA. Thus, production of both proteases and protease inhibitors is increased by angiogenic agents and TGF-beta 1. However, the kinetics and amplitude of PAI-1 and u-PA mRNA induction by these agents are strikingly different. We have used the ratio of u-PA:PAI-1 mRNA levels as an indicator of proteolytic balance. This ratio is tilted towards enhanced proteolysis in response to bFGF, towards antiproteolysis in response to TGF-beta 1, and is similar to that in untreated cultures when the two agents are added simultaneously. Using an in vitro angiogenesis assay in three-dimensional fibrin gels, we find that TGF-beta 1 inhibits the bFGF-induced formation of tube-like structures, resulting in the formation of solid endothelial cell cords within the superficial parts of the gel. These results suggest that a net positive proteolytic balance is required for capillary lumen formation. A novel perspective is provided on the relationship between extracellular matrix invasion, lumen formation, and net proteolytic balance, thereby reflecting the interplay between angiogenesis-modulating cytokines such as bFGF and TGF-beta 1.

Junctional communication is induced in migrating capillary endothelial cells.

Using an in vitro model in which a confluent monolayer of capillary endothelial cells is mechanically wounded, gap junction-mediated intercellular communication has been studied by loading the cells with the fluorescent dye, Lucifer Yellow. Approximately 40-50% of the cells in a nonwounded confluent monolayer were coupled in groups of four to five cells (basal level). Basal levels of communication were also observed in sparse and preconfluent cultures, but were reduced in postconfluent monolayers. 30 min after wounding, coupling was markedly reduced between cells lining the wound. Communication at the wound was partially reestablished by 2 h, exceeded basal levels after 6 h and reached a maximum after 24 h, at which stage approximately 90% of the cells were coupled in groups of six to seven cells. When the wound had closed (after 8 d), the increase in communication was no longer observed. Induction of wound-associated communication was unaffected by exposure of the cells to the DNA synthesis inhibitor mitomycin C, but was prevented by the protein synthesis inhibitor, cycloheximide. The induction of wound-associated communication was also inhibited when migration was prevented by placing the cells immediately after wounding at 22 degrees C or after exposure to cytochalasin D, suggesting that the increase in communication is dependent on cells migrating into the wound area. In contrast, migration was not prevented when coupling was blocked by exposure of the cells to retinoic acid, although this agent did disrupt the characteristic sheet-like pattern of migration typically seen during endothelial repair. These results suggest that junctional communication may play an important role in wound repair, possibly by coordinating capillary endothelial cell migration.

Upregulation of urokinase receptor expression on migrating endothelial cells.

One of the phenotypic hallmarks of migrating endothelial cells, both in vivo and in vitro, is expression of the urokinase-type plasminogen activator (u-PA), a key mediator of extracellular proteolysis. In the study reported here, we have used an in vitro model of endothelial cell migration to explore the mechanism of this phenomenon. We have found that wounding of an endothelial cell monolayer triggers a marked, rapid and sustained increase in expression of a specific high-affinity receptor for u-PA (u-PAr) on the surface of migrating cells. Migrating cells displayed an increase in the levels of u-PA and u-PAr mRNAs, and this increase was mediated by endogenous basic fibroblast growth factor (bFGF). We also show that the increase in u-PA activity on migrating cells can be accounted for by an increase in receptor-bound u-PA, and that the increase in activity is also dependent on endogenous bFGF. These results demonstrate that the expression of plasmin-mediated proteolytic activity by migrating endothelial cells is a consequence of increased production of both u-PA and its receptor, and that this in turn is mediated by endogenous bFGF. This suggests that u-PA, produced at increased levels by migrating cells, binds to u-PAr whose expression is upregulated on the same cells. These observations are in accord with the postulated role of u-PAr in mediating efficient and spatially restricted extracellular proteolysis, particularly in the context of cell migration.

Polyoma middle T-induced vascular tumor formation: the role of the plasminogen activator/plasmin system.

The middle T antigen of murine Polyomavirus (PymT) rapidly transforms endothelial cells, leading to the formation of vascular tumors in newborn mice. Transformed endothelial (End.) cell lines established from such tumors exhibit altered proteolytic activity as a result of increased expression of urokinase-type plasminogen activator (uPA) and are capable of inducing vascular tumors efficiently when injected into adult mice. In this study we have used mice lacking components of the PA/plasmin system to analyze the role of this system in the transformation process and in tumor growth. We found that the proteolytic status of the host is not a critical determinant for PymT-induced vascular tumor formation. In addition, the lack of either uPA or tissue-type PA (tPA) activity is not limiting for the establishment and proliferation of End. cells in vitro, although the combined loss of both PA activities leads to a marked reduction in proliferation rates. Furthermore, the in vitro morphogenetic properties of mutant End. cells in fibrin gels could only be correlated with an altered proteolytic status in cells lacking both uPA and tPA. However, in contrast with tumors induced by PymT itself, the tumorigenic potential of mutant and wild-type End. cell lines was found to be highly dependent on the proteolytic status of both the tumor cells and the host. Thus, genetic alterations in the PA/plasmin system affect vascular tumor development, indicating that this system is a causal component in PymTmediated oncogenesis.

Human leukocyte antigen (HLA) diversity and clinical applications in South Africa.

The major histocompatibility complex, known as the human leukocyte antigen (HLA) complex in humans, forms an integral component of adaptive T cell immunity by presenting self and non-self peptides to the T cell receptor, thereby allowing clonal expansion of responding peptide-specific CD4+ and CD8+ T cells. HLA likewise forms an integral part of the innate immune response through the binding of killer-cell immunoglobulin-like receptor (KIR) molecules, which regulate the response of natural killer (NK) cells. The HLA complex is found on the short arm of chromosome 6 and is the most polymorphic region in the human genome. Africans are genetically more diverse than other populations; however, information on HLA diversity among southern Africans, including South African populations, is limited. Paucity of African HLA data limits our understanding of disease associations, the ability to identify donor-recipient matches for transplantation and the development of disease-specific vaccines. This review discusses the importance of HLA in the clinical setting in South Africans and highlights how tools such as HLA imputation might augment standard HLA typing methods to increase our understanding of HLA diversity in our populations, which will better inform disease association studies, donor recruitment strategies into bone marrow registries and our understanding of human genetic diversity in South Africa.