The Peptide A-3302-B Isolated from a Marine Bacterium Micromonospora sp. Inhibits HSV-2 Infection by Preventing the Viral Egress from Host Cells

Herpesviruses are highly prevalent in the human population, and frequent reactivations occur throughout life. Despite antiviral drugs against herpetic infections, the increasing appearance of drug-resistant viral strains and their adverse effects prompt the research of novel antiherpetic drugs for treating lesions. Peptides obtained from natural sources have recently become of particular interest for antiviral therapy applications. In this work, we investigated the antiviral activity of the peptide A-3302-B, isolated from a marine bacterium, Micromonospora sp., strain MAG 9-7, against herpes simplex virus type 1, type 2, and human cytomegalovirus. Results showed that the peptide exerted a specific inhibitory activity against HSV-2 with an EC50 value of 14 μM. Specific antiviral assays were performed to investigate the mechanism of action of A-3302-B. We demonstrated that the peptide did not affect the expression of viral proteins, but it inhibited the late events of the HSV-2 replicative cycle. In detail, it reduced the cell-to-cell virus spread and the transmission of the extracellular free virus by preventing the egress of HSV-2 progeny from the infected cells. The dual antiviral and previously reported anti-inflammatory activities of A-3302-B, and its effect against an acyclovir-resistant HSV-2 strain are attractive features for developing a therapeutic to reduce the transmission of HSV-2 infections.

SARS-CoV-2 and the Host Cell: A Tale of Interactions

The ability of a virus to spread between individuals, its replication capacity and the clinical course of the infection are macroscopic consequences of a multifaceted molecular interaction of viral components with the host cell. The heavy impact of COVID-19 on the world population, economics and sanitary systems calls for therapeutic and prophylactic solutions that require a deep characterization of the interactions occurring between virus and host cells. Unveiling how SARS-CoV-2 engages with host factors throughout its life cycle is therefore fundamental to understand the pathogenic mechanisms underlying the viral infection and to design antiviral therapies and prophylactic strategies. Two years into the SARS-CoV-2 pandemic, this review provides an overview of the interplay between SARS-CoV-2 and the host cell, with focus on the machinery and compartments pivotal for virus replication and the antiviral cellular response. Starting with the interaction with the cell surface, following the virus replicative cycle through the characterization of the entry pathways, the survival and replication in the cytoplasm, to the mechanisms of egress from the infected cell, this review unravels the complex network of interactions between SARS-CoV-2 and the host cell, highlighting the knowledge that has the potential to set the basis for the development of innovative antiviral strategies.

Flavivirus infections induce a Golgi stress response in vertebrate and mosquito cells

The stress of the Golgi apparatus is an autoregulatory mechanism that is induced to compensate for greater demand in the Golgi functions. No examples of Golgi stress responses due to physiological stimuli are known. Furthermore, the impact on this organelle of viral infections that occupy the vesicular transport during replication is unknown. In this work, we evaluated if a Golgi stress response is triggered during dengue and Zika viruses replication, two flaviviruses whose replicative cycle is heavily involved with the Golgi complex, in vertebrate and mosquito cells. Using GM-130 as a Golgi marker, and treatment with monensin as a positive control for the induction of the Golgi stress response, a significant expansion of the Golgi cisternae was observed in BHK-21, Vero E6 and mosquito cells infected with either virus. Activation of the TFE3 pathway was observed in the infected cells as indicated by the translocation from the cytoplasm to the nucleus of TFE3 and increased expression of pathway targeted genes. Of note, no sign of activation of the stress response was observed in CRFK cells infected with Feline Calicivirus (FCV), a virus released by cell lysis, not requiring vesicular transport. Finally, dilatation of the Golgi complex and translocation of TFE3 was observed in vertebrate cells expressing dengue and Zika viruses NS1, but not NS3. These results indicated that infections by dengue and Zika viruses induce a Golgi stress response in vertebrate and mosquito cells due to the increased demand on the Golgi complex imposed by virion and NS1 processing and secretion.

Anti-flavivirus Properties of Lipid-Lowering Drugs

Although Flaviviruses such as dengue (DENV) and zika (ZIKV) virus are important human pathogens, an effective vaccine or antiviral treatment against them is not available. Hence, the search for new strategies to control flavivirus infections is essential. Several studies have shown that the host lipid metabolism could be an antiviral target because cholesterol and other lipids are required during the replicative cycle of different Flaviviridae family members. FDA-approved drugs with hypolipidemic effects could be an alternative for treating flavivirus infections. However, a better understanding of the regulation between host lipid metabolism and signaling pathways triggered during these infections is required. The metabolic pathways related to lipid metabolism modified during DENV and ZIKV infection are analyzed in this review. Additionally, the role of lipid-lowering drugs as safe host-targeted antivirals is discussed.

Unlike Chloroquine, mefloquine inhibits SARS-CoV-2 infection in physiologically relevant cells and does not induce viral variants.

Repositioning of clinical approved drugs could represent the fastest way to identify therapeutic options during public health emergencies, the majority of drugs explored for repurposing as antivirals for 2019 coronavirus disease (COVID-19) have failed to demonstrate clinical benefit. Without specific antivirals, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic continues to cause major global mortality. Antimalarial drugs, such as chloroquine (CQ)/hydroxychloroquine (HCQ) and mefloquine have emerged as potential anti-SARS-CoV-2 antivirals. CQ/HCQ entered the Solidarity and RECOVERY clinical trials against COVID-19 and showed lack of efficacy. Importantly, mefloquine is not a 4-aminoquinoline like CQ and HCQ and has been previously repurposed for other respiratory diseases. Unlike the 4-aminoquinolines that accumulate in the high pH of intracellular lysosomes of the lung, the high respiratory tract penetration of mefloquine is driven by its high lipophilicity. While CQ and HCQ exhibit activity in Vero E6 cells, their activity is obviated in TMPRSS2-expressing cells, such as Calu-3 cells, which more accurately recapitulate in vivo entry mechanisms for SARS-CoV-2. Accordingly, here we report the anti-SARS-CoV-2 activity of mefloquine in Calu-3 type II pneumocytes and primary human monocytes. Mefloquine inhibited SARS-CoV-2 replication, including the gamma variant, in Calu-3 cells with low cytotoxicity and EC50 and EC90 values of 1.2 and 5.3 uM, respectively. In addition, mefloquine reduced up to 68% the SARS-CoV-2 RNA levels in infected monocytes, reducing viral-induced inflammation. Mefloquine blocked early steps of the SARS-CoV-2 replicative cycle and was less prone than CQ to induce drug-associated viral mutations and synergized with RNA polymerase inhibitor. The pharmacological parameters of mefloquine are consistent with its plasma exposure in humans and its tissue-to-plasma predicted coefficient points that this drug may accumulate in the lungs. These data indicate that mefloquine could represent an orally available clinically approved drug option against COVID-19 and should not be neglected on the basis of the failure of CQ and HCQ.

Membrane Interference Against HIV-1 by Intrinsic Antiviral Factors: The Case of IFITMs

HIV-1 is a complex retrovirus that is adapted to replicate in cells of the immune system. To do so, HIV-1, like other viruses, developed strategies to use several cellular processes to its advantage, but had also to come to terms with an arsenal of cellular innate defense proteins, or antiviral factors, that target more or less efficiently, virtually every step of the virus replicative cycle. Among antiviral restriction factors, the family of interferon-induced transmembrane proteins (IFITMs) has emerged as a crucial component of cellular innate defenses for their ability to interfere with both early and late phases of viral replication by inhibiting cellular and viral membranes fusion. Here, we review the enormous advances made since the discovery of IFITMs as interferon-regulated genes more than thirty years ago, with a particular focus on HIV-1 and on the elements that modulate its susceptibility or resistance towards members of this family. Given the recent advances of the field in the elucidation of the mechanism of IFITM inhibition and on the mechanism(s) of viral resistance, we expect that future years will bring novel insights into the definition of the multiple facets of IFITMs and on their possible use for novel therapeutical approaches.

Plitidepsin, an inhibitor of the cell elongation factor eEF1a, and molnupiravir an analogue of the ribonucleoside cytidine, two new chemical compounds with intense activity against SARS-CoV-2

The knowledge of the replicative cycle of SARS-CoV-2 and its interactions with cellular proteins has opened a new therapeutic possibility based on blocking those essential for the virus. The cellular protein elongation factor eEF1A could be a good target. Among its natural inhibitors are didemnins and their related chemical compounds such as plitidepsin. In human cell culture, this compound is capable of inhibiting the virus with a potency 27,5 times that of remdesivir. It must be administered intravenously. Of the ribonucleoside analogues, molnupiravir (MK-4483/EIDD-2801) (hydroxy-cytidine) determines a lethal mutagenesis on SARS-CoV-2. In animals, after oral administration, the pulmonary viral load decreases 25,000 times and when administered as prophylaxis, approximately 100,000 times. It prevents the transmission of the virus and eliminates its presence in the oropharynx. Both chemicals have started Phase I / II human clinical trials

Chikungunya virus entry is strongly inhibited by phospholipase A2 isolated from the venom of Crotalus durissus terrificus

Chikungunya virus (CHIKV) is the etiologic agent of Chikungunya fever, a globally spreading mosquito-borne disease. There is no approved antiviral or vaccine against CHIKV, highlighting an urgent need for novel therapies. In this context, snake venom proteins have demonstrated antiviral activity against several viruses, including arboviruses which are relevant to public health. In particular, the phospholipase A2CB (PLA2CB), a protein isolated from the venom of Crotalus durissus terrificus was previously shown to possess anti-inflammatory, antiparasitic, antibacterial and antiviral activities. In this study, we investigated the multiple effects of PLA2CB on the CHIKV replicative cycle in BHK-21 cells using CHIKV-nanoluc, a marker virus carrying nanoluciferase reporter. The results demonstrated that PLA2CB possess a strong anti-CHIKV activity with a selectivity index of 128. We identified that PLA2CB treatment protected cells against CHIKV infection, strongly impairing virus entry by reducing adsorption and post-attachment stages. Moreover, PLA2CB presented a modest yet significant activity towards post-entry stages of CHIKV replicative cycle. Molecular docking calculations indicated that PLA2CB may interact with CHIKV glycoproteins, mainly with E1 through hydrophobic interactions. In addition, infrared spectroscopy measurements indicated interactions of PLA2CB and CHIKV glycoproteins, corroborating with data from in silico analyses. Collectively, this data demonstrated the multiple antiviral effects of PLA2CB on the CHIKV replicative cycle, and suggest that PLA2CB interacts with CHIKV glycoproteins and that this interaction blocks binding of CHIKV virions to the host cells.

Atorvastatin effectively inhibits late replicative cycle steps of SARS-CoV-2 in vitro

IntroductionSARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) has caused a pandemic of historic proportions and continues to spread worldwide. Currently, there is no effective therapy against this virus. This article evaluated the in vitro antiviral effect of Atorvastatin against SARS-CoV-2 and also identified the interaction affinity between Atorvastatin and three SARS-CoV-2 proteins, using in silico structure-based molecular docking approach.Materials and methodsThe antiviral activity of Atorvastatin against SARS-CoV-2 was evaluated by three different treatment strategies using a clinical isolate of SARS-CoV-2. The interaction of Atorvastatin with Spike, RNA-dependent RNA polymerase (RdRp) and 3C-like protease (3CLpro) was evaluated by molecular docking.ResultsAtorvastatin showed anti-SARS-CoV-2 activity of 79%, 54.8%, 22.6% and 25% at 31.2, 15.6, 7.9, and 3.9 µM, respectively, by pre-post-treatment strategy. In addition, atorvastatin demonstrated an antiviral effect of 26.9% at 31.2 µM by pre-infection treatment. This compound also inhibited SARS-CoV-2 in 66.9%, 75%, 27.9% and 29.2% at concentrations of 31.2, 15.6, 7.9, and 3.9 µM, respectively, by post-infection treatment. The interaction of atorvastatin with SARS-CoV-2 Spike, RdRp and 3CL protease yielded a binding affinity of −8.5 Kcal/mol, −6.2 Kcal/mol, and −7.5 Kcal/mol, respectively.ConclusionOur study demonstrated the in vitro anti-SARS-CoV-2 activity of Atorvastatin, mainly against the late steps of the viral replicative cycle. A favorable binding affinity with viral proteins by bioinformatics methods was also shown. Due to its low cost, availability, well-established safety and tolerability, and the extensive clinical experience of atorvastatin, it could prove valuable in reducing morbidity and mortality from COVID-19.ImportanceThe COVID-19 pandemic constitutes the largest global public health crisis in a century, with enormous health and socioeconomic challenges. Therefore, it is necessary to search for specific antivirals against its causative agent (SARS-CoV-2). In this sense, the use of existing drugs may represent a useful treatment option in terms of safety, cost-effectiveness, and timeliness. Atorvastatin is widely used to prevent cardiovascular events. This compound modulates the synthesis of cholesterol, a molecule necessary in different stages of the viral replicative cycle. Our study demonstrated the antiviral potential of atorvastatin against SARS-CoV-2, using an in vitro model. Furthermore, the ability of Atorvastatin to directly interfere with three viral targets (Spike, RdRp and 3CL protease) was demonstrated by bioinformatic methods. This compound is a well-studied, low-cost, and generally well-tolerated drug, so it could be a promising antiviral for the treatment of COVID-19.

A divergent cyclin/cyclin-dependent kinase complex controls the atypical replication of a malaria parasite during gametogony and transmission

Cell cycle transitions are generally triggered by variation in the activity of cyclin-dependent kinases (CDKs) bound to cyclins. Malaria-causing parasites have a life cycle with unique cell-division cycles, and a repertoire of divergent CDKs and cyclins of poorly understood function and interdependency. We show that Plasmodium berghei CDK-related kinase 5 (CRK5), is a critical regulator of atypical mitosis in the gametogony and is required for mosquito transmission. It phosphorylates canonical CDK motifs of components in the pre-replicative complex and is essential for DNA replication. During a replicative cycle, CRK5 stably interacts with a single Plasmodium-specific cyclin (SOC2), although we obtained no evidence of SOC2 cycling by transcription, translation or degradation. Our results provide evidence that during Plasmodium male gametogony, this divergent cyclin/CDK pair fills the functional space of other eukaryotic cell-cycle kinases controlling DNA replication.