56 Years of the Marburg Virus—A Review of Therapeutics

Background: The Marburg virus (MARV) is the causative agent of Marburg virus disease (MVD). This filovirus first appeared in 1967 and has since caused several outbreaks with case fatality rates between 23% and 90%. The earliest cases of MVD are thought to be caused by exposure to an infected animal, either a reservoir host (some bat species, e.g., Rousettus aegyptiacus) or a spill-over host, such as non-human primates. The virus is spread between people by direct contact with blood or other bodily fluids (including saliva, sweat, faeces, urine, tears, and breast milk) from infected individuals. Despite the high fatality rate, the Marburg virus has no vaccine or drug treatment. Recent outbreaks of the virus in 2023 in Tanzania and Equatorial Guinea have reignited the need to develop effective therapeutics, especially in the wake of the COVID-19 pandemic. Purpose: This review seeks to highlight the drug discovery efforts aimed at developing vaccines or possible treatments as potential therapeutics. Several existing antiviral agents are being probed, and vaccines are in pre-clinical and clinical stages. Natural products are also an important source of possible drugs or lead compounds and when coupled with computational techniques, these strategies offer possible therapeutics for the Marburg virus, especially in Africa, which has a high disease burden. Methods: Using the search engines Google Scholar and PubMed;keywords e.g. Marburg virus, Marburg treatments, Marburg virus drug discovery were utilized. Several results were yielded, and articles published in recent years were accepted into the final list.Results and Conclusion: This study shows there is a growing interest in therapeutics for the Marburg virus, especially with the recent outbreaks and pandemic preparedness. Initiatives that to support vaccine development and access like the MARVAC consort time are critical to fighting this public health threat.

A review of inherent beneficial effects of black seeds(Nigella sativa)in Marburg virus disease management

Background:In the management of patients with MARV infection,this review article focuses on the potential protective effects of black seeds(Nigella sativa).Methods:To find studies that evaluated various effects of black seeds(N.sativa)related to signs and symptoms of MARV infection,reference lists and databases such as Medline/Pubmed/PMC,Google Scholar,Science Direct,Ebsco,Scopus,Web of Science,and Embase were searched.Results:In numerous clinical,animal,in-vitro,in-vivo,and in-ovo studies,black seeds(N.sativa)have demonstrated potential antiviral,anti-inflammatory,antioxidant,immunomodulatory,and hepatoprotective properties that may aid in the treatment of MARV-infected patients.Conclusion:In the initial generalization phase of MARV infection,patients may use black seeds(N.sativa)as an adjunctive therapy in addition to symptomatic treatment and supportive care.Future randomized controlled clinical trials would confirm N.sativa’s efficacy and safety in MARV-infected patients.

Development and characterization of a guinea pig model for Marburg virus

The Angolan strain of Marburg virus （MARV/Ang） can cause lethal disease in humans with a case fatality rate of up to 90%, but infection of immunocompetent rodents do not result in any observable symptoms. Our previous work includes the development and characterization of a MARV/Ang variant that can cause lethal disease in mice （MARV/Ang-MA）, with the aim of using this tool to screen for promising prophylactic and therapeutic candidates. An intermediate animal model is needed to confirm any findings from mice studies before testing in the gold-standard non-human primate （NHP） model. In this study, we serially passaged the clinical isolate of MARV/Ang in the livers and spleens of guinea pigs until a variant emerged that causes 100% lethality in guinea pigs （MARV/Ang- GA）. Animals infected with MARV/Ang-GA showed signs of filovirus infection including lymphocytopenia, thrombocytopenia, and high viremia leading to spread to major organs, including the liver, spleen, lungs, and kidneys. The MARV/Ang-GA guinea pigs died between 7-9 days after infection, and the LD50 was calculated to be 1.1x10-1 TCID50 （median tissue culture infective dose）. Mutations in MARV/Ang-GA were identified and compared to sequences of known rodent-adapted MARV/Ang variants, which may benefit future studies characterizing important host adaptation sites in the MARV/Ang viral genome.

Animal models for filovirus infections

The family Filoviridae, which includes the genera Marburgvirus and Ebolavirus, contains some of the most pathogenic viruses in humans and non-human primates （NHPs）, causing severe hemorrhagic fevers with high fatality rates. Small animal models against filoviruses using mice, guinea pigs, hamsters, and ferrets have been developed with the goal of screening candidate vaccines and antivirals, before testing in the gold standard NHP models. In this review, we summarize the different animal models used to understand filovirus pathogenesis, and discuss the advantages and disadvantages of each model with respect to filovirus disease research.

Rapid Detection of Filoviruses by Real-time TaqMan Polymerase Chain Reaction Assays

Ebola virus （EBOV） and Marburg virus （MARV） are causative agents of severe hemorrhagic fever with high mortality rates in humans and non-human primates and there is currently no licensed vaccine or therapeutics. To date, there is no specific laboratory diagnostic test in China, while there is a national need to provide differential diagnosis during outbreaks and for instituting acceptable quarantine procedures. In this study, the TaqMan RT-PCR assays targeting the nucleoprotein genes of the Zaire Ebolavirus （ZEBOV） and MARV were developed and their sensitivities and specificities were investigated. Our results indicated that the assays were able to make reliable diagnosis over a wide range of virus copies from 103 to 109, corresponding to the threshold of a standard RNA transcript. The results showed that there were about 101 RNA copies per milliliter of virus culture supernatant, equivalent to 10,000 RNA molecules per infectious virion, suggesting the presence of many non-infectious particles. These data indicated that the TaqMan RT-PCR assays developed in this study will be suitable

Laboratory Detection and Diagnosis of Filoviruses

Ebola virus(EBOV) and Marburg virus(MARV),belonging to the Filoviridae family,emerged four decades ago and caused severe viral hemorrhagic fever in human and other primates.As high as 50-90% mortality,filoviruses can cause significant threats to public health.However,so far no specific and efficient vaccine has been available,nor have other treatment methods proved to be effective.It is of great importance to detect these pathogens specific,rapidly and sensitively in order to control future filovirus outbreaks.Here,recent progresses in the development of detection and diagnosis methods for EBOV and MARV are summarized.

EBOV-Z和MARV的NP基因在杆状病毒表达系统的表达及反应原性鉴定

利用昆虫杆状病毒表达系统,成功地对埃博拉(EBOV)扎伊尔型病毒和马尔堡病毒(MARV)的NP基因进行表达。Western blot结果显示,重组EBOV蛋白和重组MARV-NP与各自阳性血清有特异的反应原性,在血清学上无交叉反应。IFA检测感染重组昆虫杆状病毒的Sf9细胞表明,EBOV和MARV NP获得大量表达,呈现强烈的荧光,对照组细胞无特异荧光。该研究为EBOV和MARV流行病学调查和研制诊断试剂盒奠定了基础。

Virus inoculation and treatment regimens for evaluating anti-filovirus monoclonal antibody efficacy in vivo

The development of monoclonal antibodies to treat disease caused by filoviruses,particularly Ebola virus,has risen steeply in recent years thanks to several key studies demonstrating their remarkable therapeutic potential.The increased drive to develop new and better monoclonal antibodies has necessarily seen an increase in animal model efficacy testing,which is critical to the pre-clinical development of any novel countermeasure.Primary and secondary efficacy testing against filoviruses typically makes use of one or more rodent models(mice,guinea pigs,and occasionally hamsters)or the more recently described ferret model,although the exact choice of model depends on the specific filovirus being evaluated.Indeed,no single small animal model exists for all filoviruses,and the use of any given model must consider the nature of that model as well as the nature of the therapeutic and the experimental objectives.Confirmatory evaluation,on the other hand,is performed in nonhuman primates(rhesus or cynomolgus macaques)regardless of the filovirus.In light of the number of different animal models that are currently used in monoclonal antibody efficacy testing,we sought to better understand how these efficacy tests are being performed by numerous different laboratories around the world.To this end,we review the animal models that are being used for antibody efficacy testing against filoviruses,and we highlight the challenge doses and routes of infection that are used.We also describe the various antibody treatment regimens,including antibody dose,route,and schedule of administration,that are used in these model systems.We do not identify any single best model or treatment regimen,and we do not advocate for field-wide protocol standardization.Instead,we hope to provide a comprehensive resource that will facilitate and enhance the continued pre-clinical development of novel monoclonal antibody therapeutics.