Molecular Zika study finds possible target for tests, drugs


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The molecular structure of the Zika virus as seen on x-ray crystallography revealed electrostatic differences in a key protein compared with other flaviviruses that might explain how it infects human cells, according to a study today from Chinese researchers.

In other developments, Peru reported its first sexually transmitted Zika virus case, and public health experts from Mexico described the country's outbreak and clinical illness pattern.

NS1 surface protein clues

Scientific research to answer the many questions surrounding the explosive spread of Zika virus and its link to birth defects is under way on many fronts, and today's report on x-ray crystallography findings is the second recent study on its structure. In late March, another team published a detailed viral structure map, which revealed a variation in its surface envelope (E) proteins.

In today's report, in Nature Structural & Molecular Biology, the researchers from China focused on the nonstructural protein (NS1) of Zika virus, which plays a role in pathogenesis in other flaviviruses such as dengue and West Nile.

Identifying NS1 also helps to diagnose infections, and other research teams are eyeing it as a possible target for antiviral drug development.

In imaging the NS1 fragment, the team used the strain responsible for fueling Brazil's Zika virus outbreak. They found that it is structurally similar to dengue and West Nile viruses, but the arrangement of the electrical charges on its surface were substantially different.  

The investigators said the difference they saw might relate to host-factor interactions, which should be studied in greater detail, and that other scientists might be able to harness their findings for developing new diagnostic tools.

Sexual transmission case in Peru

In new outbreak developments, health officials in Peru reported the country's first sexually transmitted Zika case, involving a 32-year-old woman who was infected by her 39-year-old husband who was exposed to the virus while visiting Venezuela, Reuters reported today, citing the Peru's health minister.

Evidence of the virus was found in the man's semen, and both patients are recovering from their infections, according to the report.

Peru's announcement raises the number of countries that have reported cases of sexual Zika transmission to seven.

The World Health Organization (WHO), meanwhile, on Apr 15 acknowledged a sexual transmission case in Chile. The agency said a woman got sick with Zika virus symptoms, including fever and rash, on Feb 4, after her partner was ill with a Zika-like illness after traveling to a country in which local transmission was occurring.

Test results were positive for Zika virus immunoglobulin M (IgM) and IgG for both patients, and the woman's partner was negative for dengue IgM.

The WHO said sporadic sexual transmission cases will probably continue to be reported, but they don't change the overall risk assessment, given that the disease is primarily passed through mosquitoes.

Mexico's Zika outbreak pattern

Elsewhere, epidemiologists from Mexico's health ministry recently profiled the country's outbreak, noting that the first two local cases were detected on Nov 25, 2015, and that as of Feb 19, surveillance systems have identified 93 local cases so far. They reported their findings on Apr 15 in Public Library of Science (PLoS) Currents Outbreaks.

One of the first two cases was detected in Chiapas state, the same location that reported the first local chikungunya case the year before. The other was Nuevo Leon, which is near the US border.

Eight Mexican states have reported cases, but Chiapas has been hardest hit, reporting 58.1% of the country's Zika cases. Oaxaca has reported 27,  Nuevo Leon has reported 4, and Guerro has reported 3. Jalisco, Michoacan, Sinaloa, Veracruz, and Yucatan have each noted 1 case.

Eight of the 93 cases are in pregnant women, with one diagnosed at 34 weeks' gestation. The woman delivered a healthy baby, according to the report.

Clinically, Mexico's Zika cases are consistent with those reported in other countries in the Americas. Only two patients were hospitalized, and so far no related Guillain-Barre syndrome cases have been reported, though neck stiffness was reported in two cases.

Travel update, Zika in body fluids, pregnancy study launch

  • The US Centers for Disease Control and Prevention today added Belize to the destinations on its level 2 travel notice, which recommends that pregnant women postpone travel and urges women considering getting pregnant and male travelers to take certain precautions.

  • Brazil's Fiocruz Institute recently noted that it has detected live Zika virus in urine in saliva samples, according to an Apr 15 statement translated and posted by Avian Flu Diary. The institute said live virus was found in samples with the highest viral load and that infective virus particles were low or absent in urine samples with acidic pH levels. The statement noted that more studies are needed to investigate possible transmission from urine or saliva.

  • An observational study of Zika infection in pregnant women has launched in Brazil, with the goal of enrolling about 200 pregnant women per month in Sao Paulo state, according to an Apr 15 statement from the University of Alabama at Birmingham (UAB). The study will follow women starting in their first trimester regardless of Zika status. Investigators from UAB's pediatrics department are collaborating on the study with colleagues from the University of Sao Paulo. William Britt, MD, a pediatric infectious disease specialist at UAB who is leading the study, has done similar research in Brazil involving cytomegalovirus in pregnancy.

See also:

Apr 18 Nat Struct Mol Biol abstract

Apr 18 Reuters story

Apr 15 WHO statement

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