Zika virus antibodies identified in mice

Scientists have identified six Zika virus antibodies in mice, an advance that may pave the way for a vaccine, better diagnostic tests and possibly new therapies for the mosquito-borne virus.
The researchers conducted experiments in mice and identified the antibodies, including four that neutralise African, Asian and American strains of Zika virus.
The research could inform prophylactic treatment approaches for pregnant women at risk of Zika virus infection.
The team headed by Michael S Diamond and Daved H Fremont, of Washington University School of Medicine also developed atomic-level X-ray crystal structure images showing four of the antibodies in complex with three distinct regions (epitopes) of a key Zika protein.

Structural information about antibody-epitope interactions is useful to vaccine developers because it provides a pathway for designing vaccines that can induce antibodies directed towards the critical epitopes.
The researchers also found that two of the newly identified Zika antibodies could protect mice from Zika infection.

Currently there are no specific treatments for Zika virus infection, and women who become infected while pregnant are at risk of having babies with severe congenital abnormalities.
In their study, the scientists first infected mice with Zika virus and allowed the animals' immune systems to produce anti-Zika antibodies.
They identified six different antibodies that recognised a particular Zika protein, the envelope or E protein. Of those, four were shown in test-tube experiments to inhibit an Asian strain of Zika virus from infecting cells.

In addition to inhibiting the Asian strain, two of the four antibodies also neutralised Zika virus strains derived from Africa and South America (Brazil).
In additional experiments, the scientists first prophylactically treated mice with either the most potent Zika neutralising antibodies or with antibodies directed towards an unrelated Chikungunya virus, and a day later exposed the mice to Zika virus.
Mice given Chikungunya antibodies developed high levels of Zika virus in their blood and lost weight, and most died.
In contrast, mice given Zika antibodies as a preventive treatment developed lower levels of Zika virus and did not develop any clinical signs of infection.

The researchers note that the key question of whether Zika neutralising antibodies could protect pregnant women and their developing foetuses remains to be answered.
Due to significant differences in gestational features between mice and humans, antibody protection studies may require experiments in other mammals, such as non-human primates, that allow for optimal transfer of antibodies from the mother to the foetus, as occurs in humans, they noted.