ZIKV Vaccine Based On Recombinant Chimpanzee Adenovirus Vector

OBJECTIVE: Zika virus(ZIKV)is one of the flaviviruses.It can pass the bloodbrain barrier,blood-eye barrier,blood-fetal barrier and blood-testis barrier after infecting the host.After 2007,ZIKV experienced a major outbreak of viral outbreaks in Yap Island,French Bosnia and Herzegovina,and with serious complications,then quickly spread to more than 80 countries including China.Pregnant women with ZIKV infection can cause congenital ZIKV syndrome and microcephaly in infants,while adults with infection may cause Guillain-Barre syndrome(GBS)and other neurological complications.It also can cause fatal paralysis and so on.Due to the human health threats and serious social impacts brought about by ZIKV,ZIKV infection was classified as an international public health emergency by the World Health Organization in 2016.More importantly,so far,there are still no specific drugs effective against ZIKV infection.And there is no approved vaccine for ZIKV,vaccines including attenuated vaccines,inactivated vaccines and DNA vaccines,and mRNA vaccines are still in preclinical or clinical trials.Based on the demand for infectious virus control,the development of ZIKV vaccine is still the focus of current research in the field of health care.Therefore,the design of ZIKV vaccine is imminent,and the vaccine based on adenovirus vector is currently applied to many pathogens,which makes it an excellent vaccine candidate.Chimpanzee adenovirus type 7,AdC7 vector has low pre-existing immunity.So,we chose it to build a vaccine.METHODS: The E protein of ZIKV is responsible for mediating the binding and the invasion of viruses and cells and membrane fusion.It is the main antigen that causes immune translation.The pr protein can stabilize the conformation of E protein.Therefore,we chose ZIKV-prM/E protein to construct vaccine.The full-length cDNA of ZIKV-prME was cloned into chimpanzee adenovirus vector,and packaged into recombinant adenovirus vaccine in 293 cell line.The expression of antigen was detected by Western blot and flow cytometry.The prepared vaccine was used to immunize mice,and the neutralizing antibody level induced by the vaccine in mice was detected by a micro-neutralization experiment;in order to further verify the protective effect of the vaccine,we selected an interferon receptor knock-out mice that are sensitive to ZIKV.The mouse was used as an infection model,and the lethal dose of ZIKV was tested in mice.After challenge,the body weight of the mice was observed and viremia was detected.Furthermore,the in vitro antibody-dependent enhancement(ADE)of sera of the four serotypes of DENV after immunization of the ZIKV vaccine was also evaluated.RESULTS: In the above experiments,it was found that immunization with AdC7-ZIKV-prM/E and AdC7-ZIKV-M/E induced a large number of neutralizing antibodies against ZIKV in mice,and there was no significant difference in levels.In addition,we also found that mice were fully protected in lethal dose challenge experiments,and mice immunized with AdC7-ZIKV-prM/E and AdC7-ZIKV-M/E did not lose weight and no viremia was detected.In the in vitro ADE assay,the in vitro ADE effects against the four serotypes of DENV were generated following detection of AdC7-ZIKV-M/E and AdC7-ZIKV-prM/E immunization.Conclusion: We found that the AdC7-ZIKV-prM/E and AdC7-ZIKV-M/E vaccines based on chimpanzee recombinant adenovirus were able to protect mice from ZIKV infection by further evaluation of immunized mice.The ADE effect on the four DENV serotypes was found to cause significant ADE effects.Since most of the current vaccines are based on prM/E,suggesting that such ZIKV vaccines may present a potential safety risk of increasing DENV infection,further research is needed to clarify the scope of application or to optimize and improve.