Ebola Zaire vaccine (live, attenuated)

Ebola virus disease occurs when the virus comes into contact with the host tissue and invades the tissue by breaking in the mucosa or skin. Exposure can occur through animal-to-human or human-to-human transmission from blood and other bodily fluids of the virus-infected animal or human. The viral genome then replicates inside the cell, causing gene modulation in host cells - including monocytes, macrophages, and dendritic cells - and promote cell apoptosis, releasing the viral particles to extracellular tissue. The virus can further disseminate the infection by migrating to the regional lymph nodes, liver, and spleen to cause lymphadenopathy, hepatocellular necrosis, and lymphopenia. Ebola virus can cause dysregulation of the host immune system by inducing the host expression and release of pro-inflammatory mediators, including interferons, interleukins (IL-2, IL- 6, IL-8, and IL-10), and tumour necrosis factor α (TNF-α). These inflammatory processes promote endothelial activation and reduced vascular integrity. Furthermore, the release of tissue factors and increased nitric oxide levels lead to disseminated intravascular coagulation (DIC) and hypotension seen in the Ebola virus disease, respectively. The incubation period after the Ebola virus infection is 1-21 days.

By introducing the attenuated viral protein to the patient, the Ebola Zaire vaccine elicits strong cellular and antibody responses against the virus. The vaccine produces a long-term immunity and protects the patient from Ebola virus infection and disease when he or she is exposed to Zaire ebolavirus in the future. However, the relative contributions of innate, humoral and cell-mediated immunity to protection from Zaire ebolavirus is not fully understood.