Zika virus is a mosquito-borne flavivirus that was first identified in Uganda in 1947 in monkeys through a network that monitored yellow fever. It was later identified in humans in 1952 in Uganda and the United Republic of Tanzania. Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific. From the 1960s to 1980s, human infections were found across Africa and Asia, typically accompanied by mild illness. The first large outbreak of disease caused by Zika infection was reported from the Island of Yap (Federated States of Micronesia) in 2007. In July 2015 Brazil reported an association between Zika virus infection and Guillain-Barré syndrome. In October 2015 Brazil reported an association between Zika virus infection and microcephaly.
The incubation period (the time from exposure to symptoms) of Zika virus disease is not clear, but is likely to be a few days. The symptoms are similar to other arbovirus infections such as dengue, and include fever, skin rashes, conjunctivitis, muscle and joint pain, malaise, and headache. These symptoms are usually mild and last for 2-7 days.
Based on a systematic review of the literature up to 30 May 2016, WHO has concluded that Zika virus
infection during pregnancy is a cause of congenital brain abnormalities, including microcephaly; and that Zika virus is a trigger of Guillain-Barré syndrome. Intense efforts are continuing to investigate the link between Zika virus and a range of neurological disorders, within a rigorous research framework.On June 4th 2017 at the American Society for Microbiology(ASM) Microbe conference in New Orleans, Farshad Guirakhoo, Ph.D., Chief Scientific Officer, GeoVax, Inc., presented the results of a study regarding new Zika virus vaccine that gives 100% protection in mice
This vaccine is the first to be established on the studies using Zika virus NS1 protein, and the first to show single-dose protection against Zika in an immuno competent fatal mouse challenge model.
Outbred immunocompetent mice were injected with to a fatal challenge dose of Zika virus delivered directly into the brain. “A single dose of GeoVax’s NS1 vaccine candidate protected 100% of vaccinated animals,” claimed Guirakhoo.
To avoid a potential risk of disease enhancement when vaccines are developed based on Zika virus envelope proteins, the NS1 antigen was chosen as the target immunogen since it is not present on the surface of the virus. This “Antibody Dependent Enhancement (ADE) of infection” occurrence has been shown between Zika virus and a related flavivirus, Dengue, in both in vitro and in vivo studies.
An NS1- based vaccine also has the potential to limit or block transmission of Zika virus in its mosquito vector. The NS1 protein is richly produced by flaviviruses in infected hosts and is extracted together with the virus after the mosquito takes a blood meal from humans. The NS1 proteins interfere with the innate immune system of the mosquito, evolved to fight foreign pathogens, allowing the flavivirus to replicate and disseminate in mosquitoes. Therefore, claimed Guirakhoo, “a vaccine that can induce effective antibodies to NS1 and disable its function has the potential to reduce growth and transmission of Zika virus in its mosquito vector. This could enhance vaccine effectiveness in endemic areas by blocking the virus transmission from infected individuals to other members of the community.”
