Protection against Zika fever
Candidate antibodies for immunotherapy and prevention of Zika fever have been identified
The Zika virus, which causes the fever of the same name, primarily threatens pregnant women – more precisely, their future children. Recently, scientists have discovered antibodies that can neutralize this pathogen, which can protect the fetus from infection in the body of a pregnant woman and the expectant mother herself
The Zika virus was first isolated from the human body in 1954. Before that, it was considered a pathogen of monkeys, and then for a long time it did not cause serious concerns. There were few cases of Zika fever among people, and it proceeded in a relatively mild form, causing a slight increase in temperature, headache and joint pain, rash and conjunctivitis.
Doctors sounded the alarm in the mid-2000s – after a serious outbreak of the disease on the islands of Micronesia. And a few years later, an even larger outbreak, affecting about 30 thousand people, was registered on the islands of French Polynesia. A year later, Zika fever came to the South American continent.
And only then it became clear that the virus poses a great danger, however, not for adults, but for the developing fetus. It turned out that approximately 14% of mothers infected during pregnancy have children with microcephaly, an underdevelopment of the brain.
The main vector of the Zika virus, according to modern data, are yellow-horned mosquitoes (Aedes aegypti), whose natural reservoir is wild primates, and now humans. At the moment, there are no major outbreaks of Zika fever, but, according to scientists, this situation will inevitably change – and not for the better.
There is no specific therapy for Zika fever, although it can be treated with varying degrees of effectiveness with "conventional" antiviral drugs. There are also no approved preventive vaccines yet – all developments have the status of experimental ones. And recently, scientists from the USA, Brazil and Singapore have made a discovery that can accelerate the emergence of a specific treatment for Zika fever.
The idea came to scientists after studying blood samples taken from infected pregnant women during an outbreak of the disease in 2015. The researchers paid special attention to women who, despite infection and prolonged presence of the virus in the body, had healthy children.
It was suggested that these women have antibodies that prevent infection of the fetus, which was confirmed. Immune cells of "resistant" women were indeed able to produce antibodies that prevent viral particles from entering the cells.
Oddly enough, these antibodies belong to the IgM class – a more "weak", less mature type of antibodies that is produced in the early stages of infection, whereas a good neutralizing effect is usually inherent in IgG class antibodies. But in this case, the fact that IgM antibodies can have a characteristic pentameric structure, which turned out to be the most suitable to effectively "cling" to the viral particle, played a role.
In experiments on laboratory mice, researchers have shown that such antibodies not only protect animals from infection, but also suppress the reproduction of this virus to such an extent that it cannot be detected in the blood.
The discovered IgM subtype (now it appears under the name DH1017.IgM) is a promising candidate for immunotherapy of Zika fever.
The IgM free antibody molecule is a pentamer consisting of five identical monomers.
Such antibodies can be used to quickly reduce the level of Zika virus in the blood of infected pregnant women, as well as for prevention in the focus of infection. The researchers plan to conduct several more safety and efficacy tests on preclinical (animal) models and then proceed to human trials, including pregnant women as the main target group.
Article by Singh et al. A Zika virus-specific IgM elicited in pregnancy exhibits ultrapotent neutralization is published in the journal Cell.
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