Post-exposure prophylaxis following high-risk contact with Ebola virus, using immunotherapies with monoclonal antibodies, in the eastern Democratic Republic of the Congo: an emergency use program

Improving Ebola virus disease outbreak control through targeted post-exposure prophylaxis

Ebola virus disease kills more than half of people infected. Since the disease is transmitted via close human contact, identifying individuals at the highest risk of developing the disease is possible on the basis of the type of contact (correlated with viral exposure). Different candidates for post-exposure prophylaxis (PEP; ie, vaccines, antivirals, and monoclonal antibodies) each have their specific benefits and limitations, which we discuss in this Viewpoint. Approved monoclonal antibodies have been found to reduce mortality in people with Ebola virus disease. As monoclonal antibodies act swiftly by directly targeting the virus, they are promising candidates for targeted PEP in contacts at high risk of developing disease. This intervention could save lives, halt viral transmission, and, ultimately, help curtail outbreak propagation. We explore how a strategic integration of monoclonal antibodies and vaccines as PEP could provide both immediate and long-term protection against Ebola virus disease, highlighting ongoing clinical research that aims to refine this approach, and discuss the transformative potential of a successful PEP strategy to help control viral haemorrhagic fever outbreaks.

Recent advances in the treatment of Ebola disease: A brief overview

Ebola disease (EBOD) remains a significant and ongoing threat to African countries, characterized by a mortality rate of 25% to 90% in patients with high viral load and significant transmissibility. The most recent outbreak, reported in Uganda in September 2022, was declared officially over in January 2023. However, it was caused by the Sudan Ebola virus (SUDV), a culprit species not previously reported for a decade. Since its discovery in 1976, the management of EBOD has primarily relied on supportive care. Following the devastating outbreak in West Africa from 2014 to 2016 secondary to the Zaire Ebola virus (EBOV), where over 28,000 lives were lost, dedicated efforts to find effective therapeutic agents have resulted in considerable progress in treating and preventing disease secondary to EBOV. Notably, 2 monoclonal antibodies-Ebanga and a cocktail of monoclonal antibodies, called Inmazeb-received Food and Drug Administration (FDA) approval in 2020. Additionally, multiple vaccines have been approved for EBOD prevention by various regulatory bodies, with Ervebo, a recombinant vesicular stomatitis virus-vectored vaccine against EBOV being the first vaccine to receive approval by the FDA in 2019. This review covers the key signs and symptoms of EBOD, its modes of transmission, and the principles guiding supportive care. Furthermore, it explores recent advancements in treating and preventing EBOD, highlighting the unique properties of each therapeutic agent and the ongoing progress in discovering new treatments.

Prevention and post-exposure management of occupational exposure to Ebola virus

There have been significant advances in the prevention and management of Ebola virus disease (EVD) caused by Zaire Ebola virus (ZEBOV), including the development of two effective vaccines, rVSV-ZEBOV and Ad26.ZEBOV/MVA-BN-Filo. In addition, ZEBOV monoclonal antibodies have become first-line therapy for EVD. However, the 2022-23 outbreak of Sudan Ebola virus (SUDV) in Uganda has highlighted the gap in current therapies and vaccines, whose efficacy is uncertain against non-ZEBOV species. Health-care and laboratory staff working in EVD treatment centres or Ebola virus diagnostic and research laboratories face unique risks relating to potential occupational exposure to Ebola viruses. Given the substantial morbidity and mortality associated with EVD, facilities should have strategies in place to manage occupational exposures, including consideration of post-exposure therapies. In this Review, we discuss currently available evidence for prevention and post-exposure prophylaxis of EVD, including therapies currently under evaluation for SUDV.

Monoclonal antibody applications in travel medicine

For decades, immunoglobulin preparations have been used to prevent or treat infectious diseases. Since only a few years, monoclonal antibody applications (mAbs) are taking flight and are increasingly dominating this field. In 2014, only two mAbs were registered; end of October 2023, more than ten mAbs are registered or have been granted emergency use authorization, and many more are in (pre)clinical phases. Especially the COVID-19 pandemic has generated this surge in licensed monoclonal antibodies, although multiple phase 1 studies were already underway in 2019 for other infectious diseases such as malaria and yellow fever. Monoclonal antibodies could function as prophylaxis (i.e., for the prevention of malaria), or could be used to treat (tropical) infections (i.e., rabies, dengue fever, yellow fever). This review focuses on the discussion of the prospects of, and obstacles for, using mAbs in the prevention and treatment of (tropical) infectious diseases seen in the returning traveler; and provides an update on the mAbs currently being developed for infectious diseases, which could potentially be of interest for travelers.

Limited Benefit of Postexposure Prophylaxis With VSV-EBOV in Ebola Virus-Infected Rhesus Macaques

Vesicular stomatitis virus-Ebola virus (VSV-EBOV) vaccine has been successfully used in ring vaccination approaches during EBOV disease outbreaks demonstrating its general benefit in short-term prophylactic vaccination, but actual proof of its benefit in true postexposure prophylaxis (PEP) for humans is missing. Animal studies have indicated PEP efficacy when VSV-EBOV was used within hours of lethal EBOV challenge. Here, we used a lower EBOV challenge dose and a combined intravenous and intramuscular VSV-EBOV administration to improve PEP efficacy in the rhesus macaque model. VSV-EBOV treatment 1 hour after EBOV challenge resulted in delayed disease progression but little benefit in outcome. Thus, we could not confirm previous results indicating questionable benefit of VSV-EBOV for EBOV PEP in a nonhuman primate model.

Ebola outbreak in Guinea, 2021: Clinical care of patients with Ebola virus disease

Background

Experience from the Zaire Ebolavirus epidemic in the eastern Democratic Republic of the Congo (2018-2020) demonstrates that early initiation of essential critical care and administration of Zaire Ebolavirus specific monoclonal antibodies may be associated with improved outcomes among patients with Ebola virus disease (EVD).

Objectives

This series describes 13 EVD patients and 276 patients with suspected EVD treated during a Zaire Ebolavirus outbreak in Guinea in 2021.

Method

Patients with confirmed or suspected EVD were treated in two Ebola treatment centres (ETC) in the region of N'zérékoré. Data were reviewed from all patients with suspected or confirmed EVD hospitalised in these two ETCs during the outbreak (14 February 2021 - 19 June 2021). Ebola-specific monoclonal antibodies, were available 2 weeks after onset of the outbreak.

Results

Nine of the 13 EVD patients (age range: 22-70 years) survived. The four EVD patients who died, including one pregnant woman, presented with multi-organ dysfunction and died within 48 h of admission. All eight patients who received Ebola-specific monoclonal antibodies survived. Four of the 13 EVD patients were health workers. Improvement of ETC design facilitated implementation of WHO-recommended 'optimized supportive care for EVD'. In this context, pragmatic clinical training was integrated in routine ETC activities. Initial clinical manifestations of 13 confirmed EVD patients were similar to those of 276 patients with suspected, but subsequently non confirmed EVD. These patients suffered from other acute infections (e.g. malaria in 183 of 276 patients; 66%). Five of the 276 patients with suspected EVD died. One of these five patients had Lassa virus disease and a coronavirus disease 2019 (COVID-19) co-infection.

Conclusion

Multidisciplinary outbreak response teams can rapidly optimise ETC design. Trained clinical teams can provide WHO-recommended optimised supportive care, including safe administration of Ebola-specific monoclonal antibodies. Pragmatic training in essential critical care can be integrated in routine ETC activities.

Contribution

This article describes clinical realities associated with implementation of WHO-recommended standards of 'optimized supportive care' and administration of Ebola virus specific treatments. In this context, the importance of essential design principles of ETCs is underlined, which allow continuous visual contact and verbal interaction of health workers and families with their patients. Elements that may contribute to further quality of care improvements for patients with confirmed or suspected EVD are discussed.

The Evolution of Medical Countermeasures for Ebola Virus Disease: Lessons Learned and Next Steps

The Ebola virus disease outbreak that occurred in Western Africa from 2013-2016, and subsequent smaller but increasingly frequent outbreaks of Ebola virus disease in recent years, spurred an unprecedented effort to develop and deploy effective vaccines, therapeutics, and diagnostics. This effort led to the U.S. regulatory approval of a diagnostic test, two vaccines, and two therapeutics for Ebola virus disease indications. Moreover, the establishment of fieldable diagnostic tests improved the speed with which patients can be diagnosed and public health resources mobilized. The United States government has played and continues to play a key role in funding and coordinating these medical countermeasure efforts. Here, we describe the coordinated U.S. government response to develop medical countermeasures for Ebola virus disease and we identify lessons learned that may improve future efforts to develop and deploy effective countermeasures against other filoviruses, such as Sudan virus and Marburg virus.

Ebola virus protein VP40 stimulates IL-12- and IL-18-dependent activation of human natural killer cells

Accumulation of activated natural killer (NK) cells in tissues during Ebola virus infection contributes to Ebola virus disease (EVD) pathogenesis. Yet, immunization with Ebola virus-like particles (VLPs) comprising glycoprotein and matrix protein VP40 provides rapid, NK cell–mediated protection against Ebola challenge. We used Ebola VLPs as the viral surrogates to elucidate the molecular mechanism by which Ebola virus triggers heightened NK cell activity. Incubation of human peripheral blood mononuclear cells with Ebola VLPs or VP40 protein led to increased expression of IFN-γ, TNF-α, granzyme B, and perforin by CD3^–CD56⁺ NK cells, along with increases in degranulation and cytotoxic activity of these cells. Optimal activation required accessory cells like CD14⁺ myeloid and CD14^– cells and triggered increased secretion of numerous inflammatory cytokines. VP40-induced IFN-γ and TNF-α secretion by NK cells was dependent on IL-12 and IL-18 and suppressed by IL-10. In contrast, their increased degranulation was dependent on IL-12 with little influence of IL-18 or IL-10. These results demonstrate that Ebola VP40 stimulates NK cell functions in an IL-12– and IL-18–dependent manner that involves CD14⁺ and CD14^– accessory cells. These potentially novel findings may help in designing improved intervention strategies required to control viral transmission during Ebola outbreaks.