Session topic

14:10–14:15

Title: An influenza A virus–based vaccine candidate expressing Zika virus envelope protein domain III
ID: PS 125
Type: Poster session
Talk time: 3 + 2 min
Session: Poster session 3
Vaccines

Speaker: Lucas Wilken (Hannover/DE)


Abstract - Text

Abstract text (incl. references and figure legends)

Background


Zika virus (ZIKV) is a re-emerging mosquito-borne flavivirus that has been associated with congenital neurological defects in foetuses born to infected mothers. Several vaccine candidates have been developed that are based on the full-length ZIKV envelope (E) protein, which is the primary target of the neutralising antibody response. However, certain epitopes located in domains I and II of the E protein induce poorly neutralising cross-reactive antibodies that could potentially enhance infections with other co-circulating flaviviruses, such as dengue virus. By contrast, E protein domain III (EDIII) is targeted by type-specific antibodies with potent neutralising activities and, thus, considered a safe and effective subunit vaccine. Yet, EDIII is poorly immunogenic by itself, making delivery by a vaccine vector with intrinsic immunostimulatory features desirable.



Methods


Here, we generated a recombinant neuraminidase (NA)-deficient influenza A virus expressing ZIKV DIII, FLU-NA-ZIKV-EDIII, using the A/PR/8/34 reverse genetics system. To this end, we replaced most of the open reading frame of the NA gene segment with the ZIKV EDIII coding sequence, essentially as described for the construction of a West Nile virus vaccine candidate (Martina et al., PLoS One 2011). We then characterised the vaccine candidate in vitro, assessing replication kinetics, plaque morphologies, genetic stability, and antigen expression.


 


Results


FLU-NA-ZIKV-EDIII showed a highly attenuated phenotype in vitro and was dependent on exogenous NA for its replication. Moreover, the ZIKV EDIII coding sequence was stably maintained in the recombinant virus population over five passages in cell culture. Expression of ZIKV EDIII in FLU-NA-ZIKV-EDIII–infected cells was confirmed by Western blot and immunostaining of viral plaques. Surface staining also confirmed the presence of ZIKV EDIII on the membrane of infected cells, suggesting incorporation of ZIKV EDIII into viral particles.


 


Conclusions


Our results identify FLU-NA-ZIKV-EDIII as a promising replication-deficient vaccine candidate showing proper expression of ZIKV EDIII. We anticipate FLU-NA-ZIKV-EDIII to induce strong ZIKV-neutralising antibody responses in the absence of cross-reactivity with other flaviviruses and to afford protection against ZIKV infection. Currently, we are testing its immunogenicity in mice.