The rapid spread of Zaire ebolavirus (or more commonly, Ebola) prompted agencies, such as the World Health Organisation (WHO) to encourage the fast tracking of a cure. The effort is being led by GlaxoSmithKline (GSK) in collaboration with the National Institute of Allergy and Infectious Diseases (NIAID). The first human trial for an Ebola vaccine was carried out last week and shows promise, according to US scientists.
Zaire ebolavirus suppresses the immune system and targets the vascular system. Ebola’s primary targets are dendritic cells. These cells display signals of Ebola’s presence on their cell surface, presenting them to T-cells. The virus however, interferes with this process by inhibiting a molecule called interferon. As a result, the virus is left alone to replicate and grow.
Ebola then enters the bloodstream where it may travel to new sites in the body. Wherever the destination, macrophages (white blood cells that engulf foreign microbes) digest the virus, harbouring ebolavirus themselves. This causes the macrophages to release certain molecules that promote blood coagulation and clotting. The epicentre of the outbreak and its first introduction is the region of Guéckédou, which is in Guinea’s remote forest region. From there, the outbreak spilled into neighbouring regions of Guinea in addition to Liberia and Sierra Leone.
Ebola comes in a variety of forms, the most relevant of which is the current Zaire ebolavirus. However, this species is native to West Africa – a minimum 12-hour drive from Guinea. This information, as well as data from various serological experiments has led scientists to suggest the fruit bat’s intestinal tracts served as a reservoir for the virus. Humans consume these bats regularly and so authorities have prohibited the consumption of these animals in efforts to prevent the spread of Ebola in the future.
Typically, it takes many years for human trials for a completely new vaccine to be approved. However, recent events have urged a change in this timeline to push development to match the intensity of the current situation. This trial was a Phase I trial involving 20 healthy volunteers between ages 18 and 50. Each was injected with the vaccine in September. Within a month, all volunteers were producing Ebola antibodies with only two showing mild fevers. Those who developed fevers were among those given higher doses of the vaccine. This means the vaccine is successfully triggering an immunological response and providing protection.
Julie Ledgerwood’s team from the NIAID also analysed the blood of each participant to investigate whether the vaccine stimulated the production of T-lymphocytes, which help to clear infection. Assuredly, they found the vaccine induces a T-cell response, which has played an important role in protecting animals that had been injected with this vaccine and exposed to higher doses of Ebola. The vaccine contains parts of the Ebola virus genetic code from the Zaire and Sudan species. This is delivered by a chimpanzee-derived adenovirus that causes the common cold in chimps while is asymptomatic in humans.
Included in the Obama administration’s $6.2 billion fund request to treat Ebola is $238 million for the National Institute of Health (NIH) for clinical trials. Scientists aim to carry out large field trials in West Africa of those with a higher chance of contracting the virus in January to assess the efficacy of the vaccine in populations with the virus. The recent results of the human trials were sufficiently productive to warrant ‘next-step testing’ in Liberia and Sierra Leone, according to Dr Anthony Fauci of the NIAID. An equally successful result replicated in mid-2015 in larger populations may see the production of an effective vaccine late next year.
What productive aspects might pharmaceutical companies learn in order to prepare for future outbreaks, generally?