Entry gates of Japanese encephalitis virus into brain identified
doi:10.1038/nindia.2018.106 Published online 19 August 2018
Indian scientists have identified the ‘entry gates’ that allow the Japanese encephalitis virus (JEV) to invade the brain and strike the neurons, resulting in crippling brain function. Working for the first time on mouse models, a collaborative group of researchers from across the country has identified these doorways in two protein receptors – PLVAP and GKN3 – inside the rodents’ brain.
The researchers say if the functions of these two receptors are tweaked, it may be possible to stop viral entry into the neurons, thus preventing a Japanese encephalitis infection. The two newly-identified receptors are housed in the plasma membrane of the neurons, which interact with the virus glycoprotein.
JEV causes one of the major viral encephalitis in India, mostly affecting children and young adults between ages 3 and 15. Outbreaks of the virus have been reported from the states of Assam, West Bengal, Bihar, Odisha, Uttar Pradesh and Tamil Nadu in recent times.
The virus is enveloped in a glycoprotein shield. When the virus tries to enter the host cell, this ‘E-glycoprotein’ interacts with the receptors on the cell surface. This helps push the viral genome inside the cell’s cytoplasm. Many research groups across the world have been trying to identify these cell surface receptors of the virus and have also reported them in mouse cell lines. Till now, no studies were conducted in an animal model.
Anirban Basu from the National Brain Research Centre in Haryana along with collaborators from Institute of Life Sciences, Bhubaneswar, University of Calcutta and Barasat State University in West Bengal, identified the novel receptors PLVAP and GKN3 by first cloning the E-glycoprotein in the bacteria Escherichia coli. They then purified the glycoprotein, bound it to a mouse brain membrane fraction and separated the complex (through 2-DE gel electrophoresis and mass spectrometry) to study what happened.
“When we blocked these receptor proteins with specific interfering RNA (esiRNA) in the neuronal cells, the viral entry reduced,” Basu says. Similarly, when the receptors were made in abundance (or overexpressed), the virus entered more. The researchers also used antibodies to protect the neuronal cells against these receptors and found that the viral entry was less.
With computer modeling and protein docking experiments, they showed how the JEV E-glycoprotein communicates with these receptors at the molecular level. Validating the study in mouse primary cortical neuronal cultures during a JEV infection, they found that the receptor proteins were well expressed.
The researchers also worked on human autopsy tissue of JEV infected patients collected from the National Institute of Mental Health and Neurosciences, Bangalore. In these tissues, they found that the PLVAP receptor gene was more in different age groups as compared to uninfected autopsy cases.
Basu says, extendable to human trials, the study provides potential targets in these receptors for development of antivirals.
1. Mukherjee, S. et al. PLVAP and GKN3 are two critical host cell receptors which facilitate Japanese encephalitis virus entry into neurons. Sci. Rep. 8, 11784 (2018) doi: 10.1038/s41598-018-30054-z