Potential therapeutic use of corticosteroids as SARS CoV-2 main protease inhibitors: a computational study

The outbreak of COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS CoV-2), represents a pandemic threat to global public health. To date, ∼530,000 people died of this disease worldwide. Presently, researchers/clinicians are adopting the drug repurposing strategy to combat this disease. It has also been observed that some repurposed anti-viral drugs may serve as potent inhibitors of SARS CoV-2 Mpro, a key component of viral replication. Apart from these anti-viral drugs, recently dexamethasone (an important corticosteroid) is effectively used to treat COVID-19 patients. However, the mechanism behind the mode of its action is not so clear. Additionally, the effect of other well-known corticosteroids to control this disease by inhibiting the proteolytic activity of Mpro is ambiguous. In this study, we have adopted computational approaches to understand these aspects. Six well-known corticosteroids (cortisone, hydrocortisone, prednisolone, methylprednisolone, betamethasone and dexamethasone) and two repurposed drugs (darunavir and lopinavir) against COVID-19 were subjected for molecular docking studies. Two of them (betamethasone and dexamethasone) were selected by comparing their binding affinities with selected repurposed drugs toward Mpro. Betamethasone and dexamethasone interacted with both the catalytic residues of Mpro (His41 and Cys145). Molecular dynamics studies further revealed that these two Mpro-corticosteroid complexes are more stable, experience less conformational fluctuations and more compact than Mpro-darunavir/lopinavir complexes. These findings were additionally validated by MM-GBSA analysis. This study provides corroboration for execution of anti-COVID-19 activity of dexamethasone. Our study also emphasizes on the use of another important corticosteroid (betamethasone) as potential therapeutic agent for COVID-19 treatment.

Human T-Cell Lymphotropic Virus Type 1 and associated diseases in Latin America

This narrative review, which is based on a systematic literature search following the PRISMA guidelines, provides a general overview of Human T-cell Lymphotropic Virus type 1 (HTLV-1) and associated diseases: Adult T-cell Leukaemia-Lymphoma (ATLL) and HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) in Latin America, focusing on epidemiology and prevention. Using the published information on HTLV-1, ATLL and HAM/TSP prevalence, we present comprehensive and accurate maps and tables, and developed an algorithm to assist in the prevention of HTLV-1 transmission through breastfeeding while considering socio-economic status. Latin America is an interesting scenario to study HTLV-1 because of the diverse origin of its population. Apart from the expected high prevalence in inhabitants of African ancestry, the presence of endemic foci affecting indigenous populations is particularly striking. ATLL prevention is the biggest challenge in this field. Most ATLL cases are transmitted through breastfeeding; thus, prevention methods to avoid ATLL in endemic countries have to be focused on this. In view of the high inequality in most Latin American countries, reduction in breastfeeding duration, freezing/thawing and pasteurisation of breastmilk can be suitable interventions in poor settings, considering that avoiding the risk of malnutrition and infant mortality must be the priority.

Tax and Semaphorin 4D Released from Lymphocytes Infected with Human Lymphotropic Virus Type 1 and Their Effect on Neurite Growth

Human lymphotropic virus type 1 (HTLV-1) is a retrovirus causing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a neurodegenerative central nervous system (CNS) axonopathy. This virus mainly infects CD4(+) T lymphocytes without evidence of neuronal infection. Viral Tax, secreted from infected lymphocytes infiltrated in the CNS, is proposed to alter intracellular pathways related to axonal cytoskeleton dynamics, producing neurological damage. Previous reports showed a higher proteolytic release of soluble Semaphorin 4D (sSEMA-4D) from CD4(+) T cells infected with HTLV-1. Soluble SEMA-4D binds to its receptor Plexin-B1, activating axonal growth collapse pathways in the CNS. In the current study, an increase was found in both SEMA-4D in CD4(+) T cells and sSEMA-4D released to the culture medium of peripheral blood mononuclear cells (PBMCs) from HAM/TSP patients compared to asymptomatic carriers and healthy donors. After a 16-h culture, infected PBMCs showed significantly higher levels of CRMP-2 phosphorylated at Ser(522). The effect was blocked either with anti-Tax or anti-SEMA-4D antibodies. The interaction of Tax and sSEMA-4D was found in secreted medium of PBMCs in patients, which might be associated with a leading role of Tax with the SEMA-4D-Plexin-B1 signaling pathway. In infected PBMCs, the migratory response after transwell assay showed that sSEMA-4D responding cells were CD4(+)Tax(+) T cells with a high CRMP-2 pSer(522) content. In the present study, the participation of Tax-sSEMA-4D in the reduction in neurite growth in PC12 cells produced by MT2 (HTLV-1-infected cell line) culture medium was observed. These results lead to the participation of plexins in the reported effects of infected lymphocytes on neuronal cells.

Tax secretion from peripheral blood mononuclear cells and Tax detection in plasma of patients with human T-lymphotropic virus-type 1-associated myelopathy/tropical spastic paraparesis and asymptomatic carriers

Human T-lymphotropic virus-type 1 (HTLV-1) is the etiologic agent of the neurologic disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Tax viral protein plays a critical role in viral pathogenesis. Previous studies suggested that extracellular Tax might involve cytokine-like extracellular effects. We evaluated Tax secretion in 18 h-ex vivo peripheral blood mononuclear cells (PBMCs) cultures from 15 HAM/TSP patients and 15 asymptomatic carriers. Futhermore, Tax plasma level was evaluated from other 12 HAM/TSP patients and 10 asymptomatic carriers. Proviral load and mRNA encoding Tax were quantified by PCR and real-time RT-PCR, respectively. Intracellular Tax in CD4(+)CD25(+) cells occurred in 100% and 86.7% of HAM/TSP patients and asymptomatic carriers, respectively. Percentage of CD4(+)CD25(+) Tax+, proviral load and mRNA encoding Tax were significantly higher in HAM/TSP patients. Western blot analyses showed higher secretion levels of ubiquitinated Tax in HAM/TSP patients than in asymptomatic carriers. In HTLV-1-infected subjects, Western blot of plasma Tax showed higher levels in HAM/TSP patients than in asymptomatic carriers, whereas no Tax was found in non-infected subjects. Immunoprecipitated plasma Tax resolved on SDS-PAGE gave two major bands of 57 and 48 kDa allowing identification of Tax and Ubiquitin peptides by mass spectrometry. Relative percentage of either CD4(+)CD25(+) Tax+ cells, or Tax protein released from PBMCs, or plasma Tax, correlates neither with tax mRNA nor with proviral load. This fact could be explained by a complex regulation of Tax expression. Tax secreted from PBMCs or present in plasma could potentially become a biomarker to distinguish between HAM/TSP patients and asymptomatic carriers.

Tax posttranslational modifications and interaction with calreticulin in MT-2 cells and human peripheral blood mononuclear cells of human T cell lymphotropic virus type-I-associated myelopathy/tropical spastic paraparesis patients

The human retrovirus human T cell lymphotropic virus type-I (HTLV-1) is the etiologic agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Axonal degeneration in HAM/TSP patients occurs without neuron infection, with the secreted viral Tax protein proposed to be involved. We previously found that Tax secreted into the culture medium of MT-2 cells (HTLV-1-infected cell line) produced neurite retraction in neuroblastoma cells differentiated to neuronal type. To assess the relevance of Tax posttranslational modifications on this effect, we addressed the question of whether Tax secreted by MT-2 cells and peripheral blood mononuclear cells (PBMCs) of HTLV-1-infected subjects is modified. The interaction of Tax with calreticulin (CRT) that modulates intracellular Tax localization and secretion has been described. We studied Tax localization and modifications in MT-2 cells and its interaction with CRT. Intracellular Tax in MT-2 cells was assessed by flow cytometry, corresponding mainly to a 71-kDa protein followed by western blot. This protein reported as a chimera with gp21 viral protein-confirmed by mass spectrometry-showed no ubiquitination or SUMOylation. The Tax-CRT interaction was determined by confocal microscopy and coimmunoprecipitation. Extracellular Tax from HAM/TSP PBMCs is ubiquitinated according to western blot, and its interaction with CRT was shown by coimmunoprecipitation. A positive correlation between Tax and CRT secretion was observed in HAM/TSP PBMCs and asymptomatic carriers. For both proteins inhibitors and activators of secretion showed secretion through the endoplasmic reticulum-Golgi complex. Tax, present in PBMC culture medium, produced neurite retraction in differentiated neuroblastoma cells. These results suggest that Tax, whether ubiquitinated or not, is active for neurite retraction.

Cerebrospinal fluid neopterin, but not osteopontin, is a valuable biomarker for the treatment response in patients with HTLV-I-associated myelopathy

OBJECTIVE

The concentrations of neopterin and osteopontin in the cerebrospinal fluid (CSF) were measured in patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in order to evaluate their utility as biomarkers for the treatment response.

METHODS

Seven HAM/TSP patients were treated intravenously with high-dose methylprednisolone (1,000 mg/day) for 3 days. CSF samples were collected before and after the treatment. The neopterin and osteopontin concentrations were determined using high-performance liquid chromatography (HPLC) and an enzyme immunoassay, respectively. The clinical symptoms were evaluated using the Osame Motor Disability Score and the Urinary Disturbance Score.

RESULTS

Four out of the seven patients showed an improvement in motor function with the treatment, and were therefore classed as responders. The pre-treatment CSF neopterin concentration exceeded the upper limit of normal in all seven of the patients, and tended to be higher in treatment responders as compared to non-responders. The CSF neopterin concentration was reduced following treatment in all patients. The mean CSF neopterin concentration significantly (p<0.01) decreased following treatment by almost 60% (from 124.1±79.9 nmol/L to 49.2±29.8 nmol/L). The mean CSF osteopontin concentration was significantly (p<0.01) higher in the HAM/TSP patients in comparison to the 18 HTLV-1-seronegative patients who were designated as controls (9.54±4.53 mg/L vs. 3.72±3.04 mg/L). No significant (p=0.47) reduction of the CSF osteopontin concentration was observed following the intravenous administration of high-dose methylprednisolone.

CONCLUSION

These results indicate that the CSF neopterin concentration, but not the osteopontin concentration, is a potentially valuable biomarker for monitoring the treatment response in HAM/TSP patients. Furthermore, high pre-treatment CSF neopterin concentrations may be a predictive biomarker for a response to intravenous high-dose methylprednisolone therapy.