In fall 2015, a new human hepegivirus (HHpgV-1) was identified by using a novel, high throughput sequencing technique. Concerns were raised that this virus was found in blood to be used for transfusions, potentially passing on the infection. But without tools to test for its presence, there was no way to know how widespread HHpgV-1 infection is, or whether it is associated with human disease.
A new report in the Journal of Clinical Microbiology describes new tools to help address these questions. HHpgV-1 (referred to as Human Pegivirus 2, or HPgV-2, in this report) is a flavivirus, and has typical flavivirus structure: A viral envelope with embedded M and E glycoproteins surrounds the capsid, composed of C nucleocapsid proteins. The single-stranded RNA genome is inside the capsid, along with several nonstructural (NS) proteins. Using antibodies against recombinant E2 glycoprotein or NS4AB protein, first author Katie Coller and senior scientist George Dawson were able to test the seroprevalence of HPgV-2.
The researchers observed a much higher seroprevalence of HPgV-2 antibodies among those coinfected with hepatitis C virus (HCV). This confirms previous suggestions that the HPgV-2 virus has both a similar mode of transmission as HCV (both are blood-borne viruses) and indicates there may be similar factors that put people at risk for both viruses. One factor is clear: those that require blood transfusions, such as hemophiliacs, are at risk for any virus for which we aren’t testing.
HPgV-2 viremia can persist at least 7 weeks, according to molecular detection tools. This differentiates HPgV-2 from flaviviruses like West Nile or Zika virus, which cause acute infection but are cleared by the immune system, and suggests HPgV-2 may be more similar to HCV, also a blood-borne flavivirus that causes chronic infections. Future screening of active infections will provide a clearer picture on the HPgV-2 infectious cycle, which will be easier with these new tools that allow detection of both active and resolved infection.
One of the themes of yesterday’s #ASMzika conference was the importance of having a wide repertoire of research. The discovery of new viruses in the blood supply emphasizes that we don't know where new infectious agents will be found. These viruses may not make us sick – or they may be associated with illness in a way we haven’t discovered yet. Only by having proper diagnostic tests to detect the virus will we be able to make these associations, and to prevent these viruses from contaminating the blood supply.
-- Julie Wolf
Photo credits: JClinMicro report