Hendra and Nipah viruses

Hendra and Nipah viruses are classified as biosafety level 4 (BSL-4) agents in the United States and Australia, as there is a risk of infection of laboratory personnel and appropriate precautions must be taken. Widespread presence of Nipah virus antigens could be seen by immunohistochemistry (IHC) in endothelial and smooth muscle cells of blood vessels and in various parenchymal cells, particularly in neurons. Primer sequences can be designed to detect both Hendra and Nipah viruses or to detect each virus separately. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) assays can facilitate research into the pathogenesis of Hendra and Nipah viruses. African green monkey kidney (Vero) cells inoculated with high-titer samples contain antigen within a few days of inoculation. Cytopathic effect (CPE) is usually seen within 3 to 5 days. The CPE is noticeable by the formation of syncytia containing several nuclei. To confirm the presence and identity of the virus, fixed cells are tested by immunofluorescence assay, or supernatant fluids can be tested for evidence of viral replication by RT-PCR techniques. Hendra and Nipah viruses can be reliably distinguished from each other only by neutralization tests. Other cells, such as rabbit kidney cells (RK-13), are susceptible to Hendra and Nipah viruses. Hyperimmune mouse ascites fluid, which recognizes all of the structural proteins of Nipah or Hendra viruses, is used as the positive control. The enzyme-linked immunosorbent assay (ELISA) immunoglobulin M (IgM) test has been the most important technique for serological confirmation in acute patients.