The Epidemiology And Treatment Of Ebola Virus

Introduction

Ebola hemorrhagic fever (EHF) is a severely brutal disease that can lead towards death. The mortality rates have been found to be approximately 90% and the symptoms may appear soon after an incubation period of 2 to 21 days. These symptoms include intense fever, malaise, chills, nausea, fatigue, and myalgia. A combination of these symptoms affects other systems which apparent effects on gastrointestinal tract, respiratory organs, as well as neurological indications and uncontrolled bleeding among many other things. (EB book)

Ebola Virus

EBOV belongs to the Filoviridae family who are usually collectively named as “filoviruses”. These have been found as the causative agents of hemorrhagic fever disease in humans as well as other primates. (Ebola 1 Jun et al 2015)

The Ebola virus is filamentous and enveloped which is comprised of a negative strand ssRNA genome having the size of around 19 kb. The genome of this virus further transcribes for eight different sub genomic mRNAs that translates seven proteins having structural roles and these includes a nucleoprotein (NP), two virion proteins (VP35 and VP40), a surface glycoprotein (GP), two additional viral proteins associated with the membrane (VP30 and VP24), and RNA- dependent RNA polymerase (L), and a non-structural soluble protein (sGP) (Feldman et all 1993 ebola2).

Epidemiology

The origin of the word Ebola is linked to the Ebola River which is present in the Democratic Republic of Congo. In 1976, the first Ebola outbreak was documented (Pattyn et al., 1977 Ebola 5). There are various Ebola strains that vary in their nucleotide sequences and include Sudan, Zaire, Restin, and Ivory Coast strains that have been named as per the regions on which they were first identified. The difference in the sequences of these strains have been found approximately 30-40%.

Pathology

Within a week the condition of the patient may either deteriorate or get better leading to death or recovery respectively. But most of the times, the severity increases, and the high fatality rate of the Ebola virus makes it one of the most lethal and dangerous organisms. During experiments it has been found to possess the ability to spread easily though aerosols making it a contagious disease. These characteristics make it a favored tool to be used in bioterrorism.

Transmission of Ebola virus in humans

The Ebola virus is transmitted through contact with body fluids belonging to infected individuals or primates. Upon entering the human body, the virus replicates in immune cells that contain single nucleus like monocytes and macrophages. These immune cells that are usually circulating in the blood are the prime targets and when the virus is replicated and produced in a high amount, it transfers to other regions through the route provided by the bloodstream. After targeting liver, kidneys, spleen, lungs, etc. leading to the failure of the affected organs. At this stage the visible symptoms begin to appear such as chest pain, anorexia, vomiting, cough, difficulty in breathing, edema, seizure, coma, and many more.

World Health Organization (WHO) has been keeping an eye on the Ebola outbreaks and collected data as well as recruited experienced researchers and medical teams to limit the disease and develop new treatments including vaccines. A report released by the agency in 2015 showed more than 26,000 reported cases when in the outbreak began in the mentioned year in the regions of highest rates which included Guinea, Sierra Leone, and Liberia where more than 11,000 deaths occurred (WHO 2015a). The virus was also found in various African countries as well as the USA and the UK where it spread via air travel causing a huge outburst of attention in the media and at the public forums, where immense stress was laid on controlling and treating the deadly disease.

Prevention

The best approach to limit the spread of the disease outbreak is by isolating the patients who are exhibiting the symptoms of Ebola virus disease and keeping them within containment facilities, but this approach is very strenuous and hard to apply (Kekule 2015 Ebola 1). This maybe because the identification of the affected individuals in such underdeveloped regions is extremely difficult and even if they are found, the disease may progress to the last level and the virus have high chances of escaping to other individuals.

Treatment Ebola 5

Currently specific treatments against EBOV are not available. The severity of the disease has stimulated researchers and pharmaceutical companies to design new experiments, use unconventional approaches, and increase the pace for developing efficient and effective therapies. One such potential therapy is ZMappTM that is essentially a cocktail of EBOV neutralizing monoclonal antibodies (mAbs). This was used to treat 5 patients infected with the virus and had a 60% success rate (quoted from original paper Ebola 6). It was mainly because it was tested for the first time in humans with no previous safety tests other than some animal studies. And it was uniquely produced using plant-based technology (quoted from original paper Ebola 6).

Plants as a production platform for antibodies

Plant-based approaches are one of the best and most effective platforms for developing drugs and therapies for various disease. They are usually preferred over other production systems because of the benefits such as low costs, decreased time for expressions as compared to other complex systems, high turnover, decreased chances of contamination through pathogens that attack mammalian species, and increased scalability potential. The Post-translational modifications (PTMs) can be influenced and controlled by the researchers (Ebola 6 35) and their functionality and features are better enhanced than other systems (Ebola 6).

For antibody production in plants, recombination is introduced in the genes by usually using Agrobacterium tumefaciens. A virulence operon is used and the regions of the genetic material that are exchanged or transferred are referred to as T-DNA, with t pointing towards transfer. An increased transcriptional activity can occur, and this can be used as a benefit for producing immense amounts of the recombinant protein without going through the hassle of long and time-consuming steps. Viral genes are considered as another helpful entities that can help in the delivery of concerned genes. Not only can this help in the RNA replication, but it can also aid in cell communication and signaling (Ebola 6 36).

Plant-based monoclonal antibodies for Ebola treatment

Mapp Biopharmaceutical Inc. successfully isolated protective monoclonal antibodies against epitopes on Ebola glycoprotein (28 Ebola 6) and designed and changed the sequences for expression through A. tumefaciens mediated T-DNA transfer to Nicotiana benthamiana plants. A geminvirus expression cassette was used to produce 6D8 mAb in the leaves of the plant (37 Ebola 6). A high yield was obtained of the mAb within a very short amount of time. One other antibody complex namely 13F6 mAb was successfully produced in plants and the influence of the glycans of plants in the constant arm (Fc)region of the antibody was observed (38 Ebola 6). The efficacy of the plant glycans was more enhanced than the mammalian glycans and the cellular toxicity mediated by antibodies was the found to be the mode of attack used by these engineered entities.

Over the years, many attempts have been done to express an immune complex of Ebola that can be useful in immunization. In one study (EB 4), a geminiviral replicon system that was obtained from a virus (Huang et al., 2010 eb 4) was used to generate the Ebola immune complex in a plant and C-terminus of the human monoclonal antibody was fused with the Ebola glycoprotein. IgG was obtained and the immune complex that was developed as a result, was then purified and used in the immunization of mice.

Aims and Objectives

The aim of this study is to develop plant-based monoclonal antibodies that can be used as an effective treatment against the deadly Ebola virus. We expect to transform N. benthamiana and express our gene of interest that produces a monoclonal antibody that can work against the epitopes of the EBOV antigens. The viability and functionality of the produced mAbs is proposed to be analyzed through SDS/PAGE and enzyme-linked immunosorbent assay (ELISA). The expressed mAbs can then be inserted in patients of Ebola and their humoral response is to be monitored.