Emergency postexposure vaccination with vesicular stomatitis virus-vectored Ebola vaccine after needlestick

Circulating follicular T helper cells and cytokine profile in humans following vaccination with the rVSV-ZEBOV Ebola vaccine

The most recent Zaire Ebolavirus (ZEBOV) outbreak was the largest and most widespread in recorded history, emphasizing the need for an effective vaccine. Here, we analyzed human cellular immune responses induced by a single dose of the rVSV-ZEBOV vaccine candidate, which showed significant protective efficacy in endemic populations in Guinea. This is the first in-depth characterization of ZEBOV-GP specific, circulating follicular T cells (cTfh). Since antibody titers correlated with protection in preclinical models of ZEBOV infection, Tfh were predicted to correlate with protection. Indeed, the ZEBOV-specific cTfh data correlated with antibody titers in human vaccines and unexpectedly with the Tfh17 subset. The combination of two cutting edge technologies allowed the immuno-profiling of rare cell populations and may help elucidate correlates of protection for a variety of vaccines.

Phase 1 Trials of rVSV Ebola Vaccine in Africa and Europe

BACKGROUND

The replication-competent recombinant vesicular stomatitis virus (rVSV)-based vaccine expressing a Zaire ebolavirus (ZEBOV) glycoprotein was selected for rapid safety and immunogenicity testing before its use in West Africa.

METHODS

We performed three open-label, dose-escalation phase 1 trials and one randomized, double-blind, controlled phase 1 trial to assess the safety, side-effect profile, and immunogenicity of rVSV-ZEBOV at various doses in 158 healthy adults in Europe and Africa. All participants were injected with doses of vaccine ranging from 300,000 to 50 million plaque-forming units (PFU) or placebo.

RESULTS

No serious vaccine-related adverse events were reported. Mild-to-moderate early-onset reactogenicity was frequent but transient (median, 1 day). Fever was observed in up to 30% of vaccinees. Vaccine viremia was detected within 3 days in 123 of the 130 participants (95%) receiving 3 million PFU or more; rVSV was not detected in saliva or urine. In the second week after injection, arthritis affecting one to four joints developed in 11 of 51 participants (22%) in Geneva, with pain lasting a median of 8 days (interquartile range, 4 to 87); 2 self-limited cases occurred in 60 participants (3%) in Hamburg, Germany, and Kilifi, Kenya. The virus was identified in one synovial-fluid aspirate and in skin vesicles of 2 other vaccinees, showing peripheral viral replication in the second week after immunization. ZEBOV-glycoprotein-specific antibody responses were detected in all the participants, with similar glycoprotein-binding antibody titers but significantly higher neutralizing antibody titers at higher doses. Glycoprotein-binding antibody titers were sustained through 180 days in all participants.

CONCLUSIONS

In these studies, rVSV-ZEBOV was reactogenic but immunogenic after a single dose and warrants further evaluation for safety and efficacy. (Funded by the Wellcome Trust and others; ClinicalTrials.gov numbers, NCT02283099, NCT02287480, and NCT02296983; Pan African Clinical Trials Registry number, PACTR201411000919191.).

Use of Postexposure Prophylaxis After Occupational Exposure to Zaire ebolavirus

From September 2014 to April 2015, 6 persons who had occupational exposures to Zaire ebolavirus in West Africa received investigational agent rVSV-ZEBOV or TKM-100802 for postexposure prophylaxis and were monitored in the United States. All patients experienced self-limited symptoms after postexposure prophylaxis; none developed Ebola virus disease.

Vaccines against 'the other' Ebolavirus species

The Ebolavirus genus includes five member species, all of which pose a threat to global public health. These viruses cause fatal hemorrhagic fever in humans and nonhuman primates, and are considered category A pathogens due to the risk of their use as a bioweapon. The potential for an outbreak, either as a result of a natural emergence, deliberate release, or imported case underscores the need for protective vaccines. Recent progress in advancing vaccines for use against the strain of Zaire ebolavirus (EBOV) responsible for the West African Ebola outbreak offers reasons for optimism against EBOV, and demonstrates that protection against other Ebolavirus species is achievable.

[Ebola virus disease: Update]

The first known Ebola outbreak occurred in 1976. Since then, 24 limited outbreaks had been reported in Central Africa, but never affecting more than 425 persons. The current outbreak in Western Africa is the largest in history with 28,220 reported cases and 11,291 deaths. The magnitude of the epidemic has caused worldwide alarm. For the first time, evacuated patients were treated outside Africa, and secondary cases have occurred in Spain and the United States. Since the start of the current epidemic, our knowledge about the epidemiology, clinical picture, laboratory findings, and virology of Ebola virus disease has considerably expanded. For the first time, experimental treatment has been tried, and there have been spectacular advances in vaccine development. A review is presented of these advances in the knowledge of Ebola virus disease.

Ebola Virus Infections in Nonhuman Primates Are Temporally Influenced by Glycoprotein Poly-U Editing Site Populations in the Exposure Material

Recent experimentation with the variants of the Ebola virus that differ in the glycoprotein's poly-uridine site, which dictates the form of glycoprotein produced through a transcriptional stutter, has resulted in questions regarding the pathogenicity and lethality of the stocks used to develop products currently undergoing human clinical trials to combat the disease. In order to address these concerns and prevent the delay of these critical research programs, we designed an experiment that permitted us to intramuscularly challenge statistically significant numbers of naïve and vaccinated cynomolgus macaques with either a 7U or 8U variant of the Ebola virus, Kikwit isolate. In naïve animals, no difference in survivorship was observed; however, there was a significant delay in the disease course between the two groups. Significant differences were also observed in time-of-fever, serum chemistry, and hematology. In vaccinated animals, there was no statistical difference in survivorship between either challenge groups, with two succumbing in the 7U group compared to 1 in the 8U challenge group. In summary, survivorship was not affected, but the Ebola virus disease course in nonhuman primates is temporally influenced by glycoprotein poly-U editing site populations.

Clinical development of Ebola vaccines

The ongoing outbreak of Ebola virus disease in West Africa highlighted the lack of a licensed drug or vaccine to combat the disease and has renewed the urgency to develop a pipeline of Ebola vaccines. A number of different vaccine platforms are being developed by assessing preclinical efficacy in animal models and expediting clinical development. Over 15 different vaccines are in preclinical development and 8 vaccines are now in different stages of clinical evaluation. These vaccines include DNA vaccines, virus-like particles and viral vectors such as live replicating vesicular stomatitis virus (rVSV), human and chimpanzee adenovirus, and vaccinia virus. Recently, in preliminary results reported from the first phase III trial of an Ebola vaccine, the rVSV-vectored vaccine showed promising efficacy. This review charts this rapidly advancing area of research focusing on vaccines in clinical development and discusses the future opportunities and challenges faced in the licensure and deployment of Ebola vaccines.

Post-exposure prophylaxis against Ebola virus disease with experimental antiviral agents: a case-series of health-care workers

BACKGROUND

Although a few international health-care workers who have assisted in the current Ebola outbreak in west Africa have been medically evacuated for treatment of Ebola virus disease, more commonly they were evacuated after potential accidental exposure to Ebola virus. An urgent need exists for a consensus about the risk assessment of Ebola virus transmission after accidental exposure, and to investigate the use of post-exposure prophylaxis (PEP). Experimental vaccines have occasionally been used for Ebola PEP, but newly developed experimental antiviral agents have potential advantages. Here, we describe a new method for risk assessment and management of health-care workers potentially exposed to Ebola virus and report the use of experimental antiviral therapies for Ebola PEP in people.

METHODS

We devised a risk assessment and management algorithm for health-care workers potentially exposed to Ebola virus and applied this to eight consecutive individuals who were medically evacuated to the UK from west Africa between January, and March, 2015. PEP with antiviral agents was given to health-care workers assessed to have had substantial risk exposures to Ebola virus. Participants were followed up for 42 days after potential exposure.

FINDINGS

Four of eight health-care workers were classified as having had low risk exposures and managed by watchful waiting in the community. None of these health-care workers developed Ebola virus disease. The other four health-care workers had intermediate or maximum risk exposures and were given PEP with antiviral agents. PEP was well tolerated with no serious adverse effects. None of these four health-care workers, including two with maximum risk exposures from penetrating injuries with freshly used hollow-bore needles, developed Ebola virus disease.

INTERPRETATION

Standardised risk assessment should be adopted and consensus guidelines developed to systematically study the efficacy and safety of PEP with experimental agents. New experimental antiviral treatments are a viable option for PEP against Ebola.

FUNDING

Royal Free London NHS Foundation Trust.

EBOLA VACCINE. VSV-EBOV rapidly protects macaques against infection with the 2014/15 Ebola virus outbreak strain

The latest Ebola virus (EBOV) epidemic spread rapidly through Guinea, Sierra Leone, and Liberia, creating a global public health crisis and accelerating the assessment of experimental therapeutics and vaccines in clinical trials. One of those vaccines is based on recombinant vesicular stomatitis virus expressing the EBOV glycoprotein (VSV-EBOV), a live-attenuated vector with marked preclinical efficacy. Here, we provide the preclinical proof that VSV-EBOV completely protects macaques against lethal challenge with the West African EBOV-Makona strain. Complete and partial protection was achieved with a single dose given as late as 7 and 3 days before challenge, respectively. This indicates that VSV-EBOV may protect humans against EBOV infections in West Africa with relatively short time to immunity, promoting its use for immediate public health responses.

Backs against the wall: novel and existing strategies used during the 2014-2015 Ebola virus outbreak

The 2014-2015 outbreak of Ebola virus (EBOV), originating from Guinea, is now responsible for the infection of >20,000 people in 9 countries. Whereas past filovirus outbreaks in sub-Saharan Africa have been rapidly brought under control with comparably few cases, this outbreak has been particularly resistant to containment efforts. Both the general population and primary health care workers have been affected by this outbreak, with hundreds of doctors and nurses being infected in the line of duty. In the absence of approved therapeutics, several caregivers have turned to investigational new drugs as well as experimental therapies in an effort to save lives. This review aims to summarize the candidates currently under consideration for postexposure use in infected patients during the largest EBOV outbreak in history.

Definitive Management of Oligometastatic Melanoma in a Murine Model Using Combined Ablative Radiation Therapy and Viral Immunotherapy

PURPOSE

The oligometastatic state is an intermediate state between a malignancy that can be completely eradicated with conventional modalities and one in which a palliative approach is undertaken. Clinically, high rates of local tumor control are possible with stereotactic ablative radiation therapy (SABR), using precisely targeted, high-dose, low-fraction radiation therapy. However, in oligometastatic melanoma, virtually all patients develop progression systemically at sites not initially treated with ablative radiation therapy that cannot be managed with conventional chemotherapy and immunotherapy. We have demonstrated in mice that intravenous administration of vesicular stomatitis virus (VSV) expressing defined tumor-associated antigens (TAAs) generates systemic immune responses capable of clearing established tumors. Therefore, in the present preclinical study, we tested whether the combination of systemic VSV-mediated antigen delivery and SABR would be effective against oligometastatic disease.

METHODS AND MATERIALS

We generated a model of oligometastatic melanoma in C57BL/6 immunocompetent mice and then used a combination of SABR and systemically administered VSV-TAA viral immunotherapy to treat both local and systemic disease.

RESULTS

Our data showed that SABR generates excellent control or cure of local, clinically detectable, and accessible tumor through direct cell ablation. Also, the immunotherapeutic activity of systemically administered VSV-TAA generated T-cell responses that cleared subclinical metastatic tumors. We also showed that SABR induced weak T-cell-mediated tumor responses, which, particularly if boosted by VSV-TAA, might contribute to control of local and systemic disease. In addition, VSV-TAA therapy alone had significant effects on control of both local and metastatic tumors.

CONCLUSIONS

We have shown in the present preliminary murine study using a single tumor model that this approach represents an effective, complementary combination therapy model that addresses the need for both systemic and local control in oligometastatic melanoma.

Ebola Virus Disease: Experience and Decision Making for the First Patients outside of Africa

David Stephens and colleagues describe their experience of treating patients with Ebola virus disease at Emory University in the United States.

Development of experimental and early investigational drugs for the treatment of Ebola virus infections

INTRODUCTION

Ebola virus (EBOV) causes severe hemorrhagic fever in humans, and due to the aggressive nature of infection it has been difficult to develop effective medical countermeasures. Total casualties from past outbreaks numbered fewer than 1500 cases, but EBOV unexpectedly emerged from Guinea in late 2013 and infected over 25,000 people in nine countries spanning Africa, Europe and North America. Concern among the public and authorities helped spark an unprecedented push to fast-track experimental drugs for clinical use.

AREAS COVERED

The authors provide a historical timeline of the progress in developing a licensed post-exposure EBOV drug for use in humans. Furthermore, they summarize and discuss the published data with different in light of their potential to play a role during outbreak times.

EXPERT OPINION

Monoclonal antibody-based therapy is able to reverse advanced EBOV disease, but the outbreak of an antigenically divergent filovirus would require the reformulation and possibly redevelopment of the most promising candidates. Immunocompetent small animal models have not yet been developed for screening drugs against other filoviruses aside from Ravn and Marburg virus, and thus the number of prophylactic and therapeutic candidates lag behind that of EBOV. There is an urgent need for the proactive development of drugs against other neglected pathogens before the next major outbreak.

Pathophysiology of Ebola Virus Infection: Current Challenges and Future Hopes

The filoviruses, Ebola virus (EBOV) and Marburg virus (MARV), are among the deadliest viruses that cause disease in humans, with reported case fatality rates of up to 90% in some outbreaks. The high virulence of EBOV and MARV is largely attributed to the ability of these viruses to interfere with the host immune response. Currently, there are no approved vaccines or postexposure therapeutics, and treatment options for patients infected with EBOV are limited to supportive care. In this review, we discuss mechanisms of EBOV pathogenesis and its ability to subvert host immunity as well as several vaccines and therapeutics with respect to their evaluation in small animal models, nonhuman primates, and human clinical trials.

Ebola, the killer virus

Ebola virus disease (EVD) has mostly affected economically deprived countries as limited resources adversely affect a country's infrastructure and administration. Probing into the factors that led to the widespread outbreak, setting forth plans to counter EVD cases in developing countries, and devising definitive measures to limit the spread of the disease are essential steps that must be immediately taken. In this review we summarize the pathogenesis of EVD and the factors that led to its spread. We also highlight interventions employed by certain countries that have successfully limited the epidemic, and add a few preventive measures after studying the current data. According to the available data, barriers to prevent and control the disease in affected countries include irresolute and disorganized health systems, substandard sanitary conditions, poor personal hygiene practices, and false beliefs and stigma related to EVD. The public health sector along with the respective chief authorities in developing countries must devise strategies, keeping the available resources in mind, to deal with the outbreak before it occurs. As a first step, communities should be educated on EVD's symptoms, history, mode of transmission, and methods of protection, including the importance of personal hygiene practices, via seminars, newspapers, and other social media. A popular opinion leader (POL) giving this information would further help to remove the misconception about the nature of the disease and indirectly improve the quality of life of affected patients and their families.