The interplay of drug therapeutics and immune responses to SARS-CoV-2

In silico evaluation of bisphosphonates identifies leading candidates for SARS-CoV-2 RdRp inhibition

The novel coronavirus disease (COVID-19) pandemic has resulted in 777 million confirmed cases and over 7 million deaths worldwide, with insufficient treatment options. Innumerable efforts are being made around the world for faster identification of therapeutic agents to treat the deadly disease. Post Acute Sequelae of SARS-CoV-2 infection or COVID-19 (PASC), also called Long COVID, is still being understood and lacks treatment options as well. A growing list of drugs are being suggested by various in silico, in vitro and ex vivo models, however currently only two treatment options are widely used: the RNA-dependent RNA polymerase (RdRp) inhibitor remdesivir, and the main protease inhibitor nirmatrelvir in combination with ritonavir. Computational drug development tools and in silico studies involving molecular docking, molecular dynamics, entropy calculations and pharmacokinetics can be useful to identify new targets to treat COVID-19 and PASC, as shown in this work and our recent paper that identified alendronate as a promising candidate. In this study, we have investigated all bisphosphonates (BPs) on the ChEMBL database which can bind competitively to nidovirus RdRp-associated nucleotidyl (NiRAN) transferase domain, and systematically down selected seven candidates (CHEMBL608526, CHEMBL196676, CHEMBL164344, CHEMBL4291724, CHEMBL4569308, CHEMBL387132, CHEMBL98211), two of which closely resemble the approved drugs minodronate and zoledronate. This work and our recent paper together provide an in silico mechanistic explanation for alendronate and zoledronate users having dramatically reduced odds of SARS-CoV-2 testing, COVID-19 diagnosis, and COVID-19-related hospitalizations, and indicate that similar observational studies in Japan with minodronate could be valuable.

Progress in research on osteoporosis secondary to SARS-CoV-2 infection

The World Health Organization has declared that COVID-19 no longer constitutes a "public health emergency of international concern," yet the long-term impact of SARS-CoV-2 infection on bone health continues to pose new challenges for global public health. In recent years, numerous animal model and clinical studies have revealed that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can lead to secondary osteoporosis. The mechanisms involved are related to the virus's direct effects on bone tissue, dysregulation of the body's inflammatory response, hypoxia, noncoding RNA imbalance, and metabolic abnormalities. Although these studies have unveiled the connection between SARS-CoV-2 infection and osteoporosis, current research is not comprehensive and in depth. Future studies are needed to evaluate the long-term effects of SARS-CoV-2 on bone density and metabolism, elucidate the specific mechanisms of pathogenesis, and explore potential interventions. This review aims to collate existing research literature on SARS-CoV-2 infection-induced secondary osteoporosis, summarize the underlying mechanisms, and provide direction for future research.

PAD4 inhibition impacts immune responses in SARS-CoV-2 infection

Protein arginine deiminase 4 (PAD4) has emerged as a potential therapeutic target for various diseases due to its role in promoting neutrophil extracellular trap (NET) formation. NETs, composed of DNA and antimicrobial proteins, serve as a defense mechanism against pathogens but can also drive lung injury, particularly in SARS-CoV-2 infection. In this study, we examined the effects of PAD4 inhibition on clinical outcomes and adaptive immunity within the context of SARS-CoV-2 infection. Our results show that PAD4 pharmacological inhibition reduced lung NET concentration and improved clinical outcomes, similar to treatment with recombinant human DNase (rhDNase), which degrades NET structure. However, in contrast to rhDNase, PAD4 targeting diminished virus-specific T cell responses by impairing dendritic cell antigen presentation and reducing IL-2 signaling by affecting its production by T cells. In line with these observations, PAD4 pharmacological inhibition diminished antigen-specific T cell responses in a model of lung inflammation. These findings highlight the importance of carefully evaluating PAD4 as a therapeutic target in COVID-19, given its potential to compromise adaptive immune responses crucial for fighting the virus.