Could anti-cytokine therapy be the key to reducing CNS damage in HHV-6 encephalitis?

Japanese investigators evaluated cytokines and chemokines in the CSF and plasma in HHV-6 encephalitis patients with good and poor prognoses. They found IL-6, IL-7, MCP-1 to be elevated one week before onset, suggesting that these cytokines may be effective targets for intervention. In patients with poor prognoses, concentrations of IL-6 and IL-8 were higher at the onset of encephalitis.

Since cells use cytokines and chemokines to signals one another, the team from Oita, Japan hypothesized that the concentrations of these signaling molecules could be used to characterize HHV-6 infection. They analyzed blood and CSF samples were analyzed from twenty patients across six different institutions who received allo-HSCT and were diagnosed with HHV-6 encephalitis.

While HHV-6 DNA in the CSF was significantly higher in the poor prognosis group, there was no correlation between good and poor prognosis in the viral load in the CSF or in the blood.

Patients were placed in the good prognosis group if they did not die from HHV-6 encephalitis and did not suffer any neurological sequelae, while patients in the poor prognosis group died or retained neurological sequelae.

Previous studies have shown a correlation  elevated elevated levels of IL-6 and subsequebnt HHV-6B reactivation in transplant patients (Ogata 2009). Recently a Japanese group speculated that corticosteroids used for reduced intensity prophylaxis may have suppressed cytokine production which in turn limited reactivation of HHV-6 (Tamaki 2019).

IL-8 is a chemokine released by glial cells, the cells responsible for maintaining and protecting neurons, which appears to increase in concentration over the progression of encephalitis.

Read the full paper: Takano 2019