New Species of Virus Found in Patients with Brain Infections in Vietnam, Named CyCV-VN

Scientists from the Netherlands, Vietnam and United Kingdom, reporting the journal mBio, have described a new cyclovirus in the viral family Circoviridae.

Left : structure CyCV-VN with nonamer sequence in red (Le Van Tan et al).  Right: virions of porcine circovirus, which is in the same viral family as CyCV-VN (Deshka Foster / Claire Watt)

Left : structure CyCV-VN with nonamer sequence in red (Le Van Tan et al). Right: virions of porcine circovirus, which is in the same viral family as CyCV-VN (Deshka Foster / Claire Watt)

The team has identified the novel virus in the fluid around the brain of two patients with brain infections of unknown cause. The virus, named CyCV-VN, was subsequently detected in an additional 26 out of 642 patients with brain infections of known and unknown causes.

The team then sequenced the entire genetic material of CyCV-VN, confirming that it represents a new species that has not been isolated before. They found that it belongs to the viral family Circoviridae, which have previously only been associated with disease in animals, including birds and pigs.

“We don’t yet know whether this virus is responsible for causing the serious brain infections we see in these patients, but finding an infectious agent like this in a normally sterile environment like the fluid around the brain is extremely important. We need to understand the potential threat of this virus to human and animal health,” said Dr Rogier van Doorn from the University of Oxford’s Center for Clinical Vaccinology and Tropical Medicine, co-author of a paper reporting the discovery in the journal mBio.

The team was not able to detect CyCV-VN in blood samples from the patients but it was present in 8 out of 188 fecal samples from healthy children. CyCV-VN was also detected in more than half of fecal samples from chickens and pigs taken from the local area of one of the patients from whom the virus was initially isolated, which may suggest an animal source of infection.

“The evidence so far seems to suggest that CyCV-VN may have crossed into humans from animals, another example of a potential zoonotic infection. However, detecting the virus in human samples is not in itself sufficient evidence to prove that the virus is causing disease, particularly since the virus could also be detected in patients with other known viral or bacterial causes of brain infection,” said study lead author Dr Le Van Tan from Hospital for Tropical Diseases in Ho Chi Minh City.

“While detection of this virus in the fluid around the brain is certainly remarkable, it could still be that it doesn’t cause any harm. Clearly we need to do more work to understand the role this virus may play in these severe infections.”

The team is currently trying to grow CyCV-VN in the laboratory using cell culture techniques in order to develop a blood assay to test for antibody responses in patient samples, which would indicate that the patients had mounted an immune response against the virus. Such a test could also be used to study how many people in the population have been exposed to CyCV-VN without showing symptoms of disease.

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Bibliographic information: Le Van Tan et al. Identification of a New Cyclovirus in Cerebrospinal Fluid of Patients with Acute Central Nervous System Infections. mBio, vol. 4, no. 3, e00231-13; doi: 10.1128/mBio.00231-13