Nhiễm vi rút chậm là rối loạn liên tục với thời gian ủ bệnh dài (năm), tiến hành từ từ cho đến chết. Các đại lý nhân gây bệnh là virus hoặc thông thường hay được gọi là đại lý độc đáo hoặc không điển hình, gần đây còn được gọi là prion. | 40. SLOW VIRUSES The term slow virus infection was introduced by the late Icelandic veterinary surgeon Bj0rn Sigurdsson in 1954. G. Haukenes Slow virus infections are progressive disorders with a long incubation period years proceeding slowly to death. The causative agents are either conventional viruses or so-called unconventional or atypical agents recently also called prions. CONVENTIONAL SLOW VIRUS INFECTIONS SUBACUTE SCLEROSING PANENCEPHALITIS SSPE SSPE is caused by measles virus which becomes reactivated in brain cells years after the primary acute measles infection. The majority of SSPE patients contracted their measles infection in early infancy before 2 years of age and the interval to development of SSPE is 5-10 years. Thus in most cases the SSPE patients are children or teenagers. Boys are more commonly affected than girls. The main clinical manifestations are intellectual deterioration and motor dysfunction. The disease progresses to death in the course of 4-12 months. The most significant diagnostic finding is the presence of oligoclonal IgG bands on agarose electrophoresis of concentrated cerebrospinal fluid CSF . The bands represent antibodies to various measles virus components. The antibody titres to measles virus antigens in the CSF examined by haemagglutination inhibition complement fixation or ELISA tests are raised relative to those of serum. Normally the antibody concentration in CSF is 100-800 times lower than in the serum. In SSPE this ratio is dramatically reduced for measles antibodies indicating intrathecal production of antibodies provided that a damaged blood-brain barrier can be excluded. The pathogenesis of SSPE is not clear. It is not known in what form and where the measles virus or viral genetic material persists in the period from acute measles to the development of SSPE. Measles virus is an RNA virus without a reverse transcriptase or other enzymes required for integration of a proviral DNA as is seen for retroviruses. SSPE virus
