An Overview of Antivirals against Monkeypox Virus and Other Orthopoxviruses

Structural basis of human mpox viral DNA replication inhibition by brincidofovir and cidofovir

Mpox virus has wildly spread over 108 non-endemic regions in the world since May 2022. DNA replication of mpox is performed by DNA polymerase machinery F8-A22-E4, which is known as a great drug target. Brincidofovir and cidofovir are reported to have broad-spectrum antiviral activity against poxviruses, including mpox virus in animal models. However, the molecular mechanism is not understood. Here we report cryogenic electron microscopy structures of mpox viral F8-A22-E4 in complex with a DNA duplex, or dCTP and the DNA duplex, or cidofovir diphosphate and the DNA duplex at resolution of 3.22, 2.98 and 2.79 Å, respectively. Our structural work and DNA replication inhibition assays reveal that cidofovir diphosphate is located at the dCTP binding position with a different conformation to compete with dCTP to incorporate into the DNA and inhibit DNA synthesis. Conformation of both F8-A22-E4 and DNA is changed from the pre-dNTP binding state to DNA synthesizing state after dCTP or cidofovir diphosphate is bound, suggesting a coupling mechanism. This work provides the structural basis of DNA synthesis inhibition by brincidofovir and cidofovir, providing a rational strategy for new therapeutical development for mpox virus and other pox viruses.

Mpox (Monkeypox) Virus and Its Co-Infection with HIV, Sexually Transmitted Infections, or Bacterial Superinfections: Double Whammy or a New Prime Culprit?

Epidemiologic studies have established that mpox (formerly known as monkeypox) outbreaks worldwide in 2022-2023, due to Clade IIb mpox virus (MPXV), disproportionately affected gay, bisexual, and other men who have sex with men. More than 35% and 40% of the mpox cases suffer from co-infection with HIV and sexually transmitted infections (STIs) (e.g., Chlamydia trachomatis, Neisseria gonorrhoeae, Treponema pallidum, and herpes simplex virus), respectively. Bacterial superinfection can also occur. Co-infection of MPXV and other infectious agents may enhance disease severity, deteriorate outcomes, elongate the recovery process, and potentially contribute to the morbidity and mortality of the ensuing diseases. However, the interplays between MPXV and HIV, bacteria, other STI pathogens and host cells are poorly studied. There are many open questions regarding the impact of co-infections with HIV, STIs, or bacterial superinfections on the diagnosis and treatment of MPXV infections, including clinical and laboratory-confirmed mpox diagnosis, suboptimal treatment effectiveness, and induction of antiviral drug resistance. In this review article, we will discuss the progress and knowledge gaps in MPXV biology, antiviral therapy, pathogenesis of human MPXV and its co-infection with HIV, STIs, or bacterial superinfections, and the impact of the co-infections on the diagnosis and treatment of mpox disease. This review not only sheds light on the MPXV infection and co-infection of other etiologies but also calls for more research on MPXV life cycles and the molecular mechanisms of pathogenesis of co-infection of MPXV and other infectious agents, as well as research and development of a novel multiplex molecular testing panel for the detection of MPXV and other STI co-infections.

An overview on mRNA-based vaccines to prevent monkeypox infection

The human monkeypox virus (Mpox) is classified as a member of the Poxviridae family and belongs to the Orthopoxvirus genus. Mpox possesses double-stranded DNA, and there are two known genetic clades: those originating in West Africa and the Congo Basin, commonly known as Central African clades. Mpox may be treated with either the vaccinia vaccination or the therapeutics. Modifying the smallpox vaccine for treating and preventing Mpox has shown to be beneficial because of the strong link between smallpox and Mpox viruses and their categorization in the same family. Cross-protection against Mpox is effective with two Food and Drug Administration (FDA)-approved smallpox vaccines (ACAM2000 and JYNNEOSTM). However, ACAM2000 has the potential for significant adverse effects, such as cardiac issues, whereas JYNNEOS has a lower risk profile. Moreover, Mpox has managed to resurface, although with modified characteristics, due to the discontinuation and cessation of the smallpox vaccine for 40 years. The safety and efficacy of the two leading mRNA vaccines against SARS-CoV-2 and its many variants have been shown in clinical trials and subsequent data analysis. This first mRNA treatment model involves injecting patients with messenger RNA to produce target proteins and elicit an immunological response. High potency, the possibility of safe administration, low-cost manufacture, and quick development is just a few of the benefits of RNA-based vaccines that pave the way for a viable alternative to conventional vaccines. When protecting against Mpox infection, mRNA vaccines are pretty efficient and may one day replace the present whole-virus vaccines. Therefore, the purpose of this article is to provide a synopsis of the ongoing research, development, and testing of an mRNA vaccine against Mpox.

Natural compounds inhibit Monkeypox virus methyltransferase VP39 in silico studies

VP39, an essential 2'-O-RNA methyltransferase enzyme discovered in Monkeypox virus (MPXV), plays a vital role in viral RNA replication and transcription. Inhibition of the enzyme may prevent viral replication. In this context, using a combination of molecular docking and molecular dynamics (MDs) simulations, the inhibitory ability of NCI Diversity Set VII natural compounds to VP39 protein was investigated. It should be noted that the computed binding free energy of ligand via molecular docking and linear interaction energy (LIE) approaches are in good agreement with the corresponding experiments with coefficients of R = 0.72 and 0.75, respectively. NSC 319990, NSC 196515 and NSC 376254 compounds were demonstrated that can inhibit MPVX methyltransferase VP39 protein with the similar affinity compared to available inhibitor sinefungin. Moreover, nine residues involving Gln39, Gly68, Gly72, Asp95, Arg97, Val116, Asp138, Arg140 and Asn156 may be argued that they play an important role in binding process of inhibitors to VP39.Communicated by Ramaswamy H. Sarma.

Clinical considerations on monkeypox antiviral medications: An overview

Monkeypox (mpox), a virus belonging to the orthopoxvirus family, can cause a zoonotic infectious disease with morbidity and cosmetic complications. Therefore, effective antiviral drugs with appropriate safety profiles are important for the treatment of patients with mpox. To date, there is no FDA-approved drug for the treatment of mpox. However, tecovirimat, brincidofovir, and cidofovir are the candidate therapies for the management of mpox. Given the safety concerns following the use of these medications, we aimed to review evidence on the clinical considerations of mpox antiviral medications that will be useful to guide clinicians in the treatment approach. Based on the current evidence, tecovirimat has favorable clinical efficacy, safety, and side effect profile and it can be considered as first-line treatment for mpox.

Differences in pathogenicity among the mpox virus clades: impact on drug discovery and vaccine development

Since May 2022, mpox virus (MPXV) has attracted considerable attention due to a multi-country outbreak. Marked differences in epidemiology, transmission, and pathology between the 2022 global mpox outbreak (clade IIb) and classical mpox disease, endemic in Africa (clades I and IIa) have been highlighted. MPXV genome analysis has identified the genomic changes characterizing clade IIb and the drivers of MPXV rapid evolution. Although mpox cases have largely declined, MPXV cryptic transmission and microevolution continues, which may lead to an MPXV of unpredictable pathogenicity. Vaccines and antivirals developed against variola virus, the agent that caused the extinguished plague smallpox, have been used to contain the 2022 mpox outbreak. In this review article, recent findings on MPXV origin and evolution and relevant models able to recapitulate differences in MPXV pathogenicity, which are important for drug and vaccine development, are discussed.

Exploring the Traditional Chinese Medicine (TCM) database chemical space to target I7L protease from monkeypox virus using molecular screening and simulation approaches

In the current study, we used molecular screening and simulation approaches to target I7L protease from monkeypox virus (mpox) from the Traditional Chinese Medicines (TCM) database. Using molecular screening, only four hits TCM27763, TCM33057, TCM34450 and TCM31564 demonstrated better pharmacological potential than TTP6171 (control). Binding of these molecules targeted Trp168, Asn171, Arg196, Cys237, Ser240, Trp242, Glu325, Ser326, and Cys328 residues and may affect the function of I7L protease in in vitro assay. Moreover, molecular simulation revealed stable dynamics, tighter structural packing and less flexible behaviour for all the complexes. We further reported that the average hydrogen bonds in TCM27763, TCM33057, TCM34450 and TCM31564I7L complexes remained higher than the control drug. Finally, the BF energy results revealed -62.60 ± 0.65 for the controlI7L complex, for the TCM27763I7L complex -71.92 ± 0.70 kcal/mol, for the TCM33057I7L complex the BF energy was -70.94 ± 0.70 kcal/mol, for the TCM34450I7L the BF energy was -69.94 ± 0.85 kcal/mol while for the TCM31564I7L complex the BF energy was calculated to be -69.16 ± 0.80 kcal/mol. Although, we used stateoftheart computational methods, these are theoretical insights that need further experimental validation.

A Comprehensive Review on Monkeypox Viral Disease with Potential Diagnostics and Therapeutic Options

The purpose of this review is to give an up-to-date, thorough, and timely overview of monkeypox (Mpox), a severe infectious viral disease. Furthermore, this review provides an up-to-date treatment option for Mpox. The monkeypox virus (MPXV) has remained the most virulent poxvirus for humans since the elimination of smallpox approximately 41 years ago, with distribution mainly in central and west Africa. Mpox in humans is a zoonotically transferred disease that results in symptoms like those of smallpox. It had spread throughout west and central Africa when it was first diagnosed in the Republic of Congo in 1970. Mpox has become a major threat to global health security, necessitating a quick response by virologists, veterinarians, public health professionals, doctors, and researchers to create high-efficiency diagnostic tests, vaccinations, antivirals, and other infection control techniques. The emergence of epidemics outside of Africa emphasizes the disease's global significance. A better understanding of Mpox's dynamic epidemiology may be attained by increased surveillance and identification of cases.

Antiviral activities of two nucleos(t)ide analogs against vaccinia, mpox, and cowpox viruses in primary human fibroblasts

Many poxviruses are significant human and animal pathogens, including viruses that cause smallpox and mpox (formerly monkeypox). Identifying novel and potent antiviral compounds is critical to successful drug development targeting poxviruses. Here we tested two compounds, nucleoside trifluridine, and nucleotide adefovir dipivoxil, for antiviral activities against vaccinia virus (VACV), mpox virus (MPXV), and cowpox virus (CPXV) in physiologically relevant primary human fibroblasts. Both compounds potently inhibited the replication of VACV, CPXV, and MPXV (MA001 2022 isolate) in plaque assays. In our recently developed assay based on a recombinant VACV expressing secreted Gaussia luciferase, they both exhibited high potency in inhibiting VACV replication with EC₅₀s in the low nanomolar range. In addition, both trifluridine and adefovir dipivoxil inhibited VACV DNA replication and downstream viral gene expression. Our results characterized trifluridine and adefovir dipivoxil as strong poxvirus antiviral compounds and further validate the VACV Gaussia luciferase assay as a highly efficient and reliable reporter tool for identifying poxvirus inhibitors. Given that both compounds are FDA-approved drugs, and trifluridine is already used to treat ocular vaccinia, further development of trifluridine and adefovir dipivoxil holds great promise in treating poxvirus infections, including mpox.

Progress and prospects on vaccine development against Monkeypox Infection

The monkeypox virus (MPOX) is an uncommon zoonotic illness brought on by an orthopoxvirus (OPXV). MPOX can occur with symptoms similar to smallpox. Since April 25, 2023, 110 nations have reported 87,113 confirmed cases and 111 fatalities. Moreover, the outspread prevalence of MPOX in Africa and a current outbreak of MPOX in the U.S. have made it clear that naturally occurring zoonotic OPXV infections remain a public health concern. Existing vaccines, though they provide cross-protection to MPOX, are not specific for the causative virus, and their effectiveness in the light of the current multi-country outbreak is still to be verified. Furthermore, as a sequel of the eradication and cessation of smallpox vaccination for four decades, MPOX found a possibility to re-emerge, but with distinct characteristics. The World Health Organization (WHO) suggested that nations use affordable MPOX vaccines within a framework of coordinated clinical effectiveness and safety evaluations. Vaccines administered in the smallpox control program and conferred immunity against MPOX. Currently, vaccines approved by WHO for use against MPOX are replicating (ACAM2000), low replicating (LC16m8), and non-replicating (MVA-BN). Although vaccines are accessible, investigations have demonstrated that smallpox vaccination is approximately 85% efficient in inhibiting MPOX. In addition, developing new vaccine methods against MPOX can help prevent this infection. To recognize the most efficient vaccine, it is essential to assess effects, including reactogenicity, safety, cytotoxicity effect, and vaccine-associated side effects, especially for high-risk and vulnerable people. Recently, several orthopoxvirus vaccines have been produced and are being evaluated. Hence, this review aims to provide an overview of the efforts dedicated to several types of vaccine candidates with different strategies for MPOX, including inactivated, live-attenuated, virus-like particles (VLPs), recombinant protein, nucleic acid, and nanoparticle-based vaccines, which are being developed and launched.