The development and use of an antibody capture radioimmunoassay for specific IgM to a human parvovirus-like agent

An IgM-antibody capture radioimmunoassay (MACRIA) was developed for detection of IgM antibody specific for the human parvovirus-like agent B19. Diagnosis of infection with this agent by either antigen detection or antibody seroconversion had been made by counter-current immunoelectrophoresis (CIE) in 18 cases of aplastic crisis occurring in children with homozygous sickle-cell desease. The MACRIA described here gave positive results in 17 of 18 cases; in the remaining case only an acute specimen taken from the patient during viraemia and late convalescent specimens taken 184 and 247 days after onset of illness were avaliable. The test was used to investigate 20 further cases of aplastic crisis in which neither viral antigen nor antibody seroconversion could be detected by CIE. Detection of virus-specific IgM permitted diagnosis of infection with this parvovirus-like agent in 17 of these cases. In the remaining three cases only single serum specimens taken late in convalescence, 82, days or more after the onset of symptoms, were available. In addition to these 34 cases of aplastic crisis in which primary infection with this agent was diagnosed by MACRIA, seven cases of apparent 'silent' infection detected by CIE were investigated. The test permitted the discrimination between primary infection and re-exposure to the virus in six of these patients. The use of this assay has added a considerable weight of evidence implicating primary infection with this parvovirus-like agent as an important cause of aplasic crisis in children with sickle-cell disease. Furthermore, MACRIA permits diagnosis of infection when only single serum specimens taken up to ten weeks after infection are available. Thus the use of this test will significantly facilitate the investigation of other clinical syndromes of presumptive infective infectious aetiology (AU)

Outbreak of aplastic crises in sickle cell anaemia associated with parvovirus-like agent

Since 1952, 112 childen with sickle cell anaemia (SCA) in Jamaica have had an aplastic crisis. Outbreaks occurred in 1956, 1960, 1965-67, 1971-73, and 1979-80. Most cases occurred in children under 10 years of age, and an aplastic crisis in a patient over the age of 15 years is rare. There were 38 cases in 1970-80 and stored serum specimens from 28 of these were available for virus studies. Evidence for infection with a parvovirus-like agent was found in 24 of these 28 cases. Viral antigen was detected in 2 patients, both of whom demonstated seroconversion. Serconversion during 1980 was detected in a further 7, increasing amounts of antibody during the convalescent period were found in 5, antibody was found in 2 of 4 patients from whom only an acute phase specimen was available and the remaining 10 were antibody positive in the only convalescent phase sample available for testing. Antibody was found in 4 of 94 controls with the SS genotype (in retrospect 2 of these may have had an aplastic crisis) and in 17 percent of 48 controls with a normal haemoglobin (AA) genotype. The results accord with the possibility that the parvovirus-like agent is the principal cause of aplastic crisis in SCA (Summary)