Infectious Diseases and Microbiology -Subacute Sclerosing Panencephalitis (SSPE)( defective measles virus mutant)

Infectious Diseases and Microbiology = ​Subacute Sclerosing Panencephalitis (SSPE)( defective measles virus mutant) 
A defective measles virus mutant is the cause of SSPE. Measles virus is transmitted by respiratory droplets.
SSPE is a rare, late progressive neurologic disease of children, with the majority of cases appearing  6–8 years after acute measles. Incidence of SSPE in unvaccinated children is 1 in 1 million cases.
SSPE is characterized by an insidious onset of personality changes, intellectual deterioration, with later myoclonic jerks (periodic muscle spasms), spasticity, blindness, and death. The clinical course is progressive,
with death occurring 1–3 years after onset.
Brain pathology in SSPE consists of demyelination and inflammation due to chronic infection by SSPE measles virus over the course of years. Measles virus defective in virion production can be isolated from brain cells of patients with SSPE. The measles virus variant that causes SSPE has mutations in the matrix (M) protein responsible for viral assembly and budding. The lack of a functional M protein results in nonproductive infection by SSPE measles virus. Patients with SSPE have elevated levels of measles virus antibodies in serum and CSF, but no antibody to the M protein. Measles virus escapes immune surveillance by cell-to-cell fusion mediated by the fusion (F) protein.
Patients with SSPE are diagnosed by the detection of high measles virus antibody levels in serum and CSF.
There is no specific treatment for measles virus infection. Live, attenuated measles virus vaccine is highly effective in preventing measles and has reduced markedly the incidence of SSPE.