With two distinct lineages (African & Asian), and reportedly Growing Genetic Diversity Of Zika Viruses In Latin America, one of the concerns has been whether this diverse constellation of Zika strains would hamper the development of an effective vaccine.
Yesterday Cell Reports published an NIH funded study that provides potentially good news on that front, as researchers have found that despite its diversity, all of the Zika viruses tested to date belong to the same serotype.
First a link to the study, and the abstract, followed by excerpts from the press release.
Kimberly A. Dowd, Christina R. DeMaso, Rebecca S. Pelc, Scott D. Speer, Alexander R.Y. Smith, Leslie Goo, Derek J. Platt, John R. Mascola, Barney S. Graham, Mark J. Mulligan, Michael S. Diamond, Julie E. Ledgerwood, Theodore C. Pierson
•Neutralization studies with convalescent ZIKV-immune sera identify a single serotype
•Infection with a single ZIKV strain elicits broadly neutralizing antibodies
•Strain selection may not be a critical parameter for ZIKV vaccine development
Recent epidemics of Zika virus (ZIKV) have been associated with congenital malformation during pregnancy and Guillain-Barré syndrome. There are two ZIKV lineages (African and Asian) that share >95% amino acid identity. Little is known regarding the ability of neutralizing antibodies elicited against one lineage to protect against the other.
We investigated the breadth of the neutralizing antibody response following ZIKV infection by measuring the sensitivity of six ZIKV strains to neutralization by ZIKV-confirmed convalescent human serum or plasma samples. Contemporary Asian and early African ZIKV strains were similarly sensitive to neutralization regardless of the cellular source of virus.
Furthermore, mouse immune serum generated after infection with African or Asian ZIKV strains was capable of neutralizing homologous and heterologous ZIKV strains equivalently. Because our study only defines a single ZIKV serotype, vaccine candidates eliciting robust neutralizing antibody responses should inhibit infection of both ZIKV lineages, including strains circulating in the Americas.
While this finding makes the development of a vaccine less complicated than if multiple serotypes were involved, there is still a long road (and potentially bumpy) road ahead before we have a safe, effective, and commercially available Zika vaccine.
This press release on the above study from NIAID.
Public Release: 29-Jul-2016
Zika infection is caused by one virus serotype, NIH study finds
Finding may have implications for vaccine development
NIH/National Institute of Allergy and Infectious Diseases
Vaccination against a single strain of Zika virus should be sufficient to protect against genetically diverse strains of the virus, according to a study conducted by investigators from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH); Washington University in St. Louis; and Emory University in Atlanta.
Zika virus strains are grouped into two distinct genetic lineages: African and Asian. The Zika virus strain circulating in the current outbreak affecting Central and South America and the Caribbean is of the Asian lineage. When individuals are infected with Zika virus, their immune systems produce neutralizing antibodies to fight the infection. These antibodies may offer immunity against future infections by strains of the same Zika virus lineage. Until now, it was unclear whether the antibodies could also protect against infection with strains of the other Zika virus lineage. Results from laboratory experiments and tests in mice now show this may be possible. Such protection indicates that, despite being genetically distinct, all strains of Zika virus have identical surface antigens and therefore are the same serotype. The closely-related Dengue virus has four serotypes, which is why people can be infected with dengue as many as four times, once with each serotype.
In this study, scientists took serum samples from people infected by Zika virus strains circulating in South America and mixed them with multiple strains of the virus in the laboratory to see how well the serum antibodies neutralized the virus. Results showed that antibodies elicited after infection with Zika virus strains of the Asian lineage were able to potently inhibit both Asian lineage and African lineage strains. The researchers conducted similar experiments using serum samples from mice and found that sera from mice infected with either Asian or African Zika virus strains were equally effective in neutralizing virus strains from either lineage.
The findings are important to the ongoing effort to rapidly develop a preventive Zika vaccine, according to the authors. Because there is only one Zika virus serotype, antibodies elicited by any Zika virus strain in a vaccine could conceivably confer protection against all Zika virus strains, the researchers conclude.