Human parvovirus infection in homozygous sickle cell disease

We studied the epidemiology of human parvovirus B19 infection in 308 children with homozygous sickle cell (SS) disease and 239 controls with a normal haemoglobin (AA) genotype followed from birth in a cohort study. Annual serum samples identified the time and frequency of B19 infection, which did not differ between SS and AA children, about 40 percent of each age group developing specific IgG by age 15. B19 infection followed an epidemic pattern similar to that observed for aplastic crises; accounted for all 91 aplastic crises that occurred; and was found in an additional 23 SS patients, of whom 10 showed mild haematological changes and 13 no changes. The magnitude or duration of IgG response did not differ between these groups. No patient had 2 attacks of aplasia and no patient nor control had 2 attacks of B19 infection. Following B19 infection, serial specific IgG concentrations remained high after 5 years in only 45 percent of SS patients, although the rarity of recurrent aplasia suggests lifelong immunity. B19 infection accounts for most if not all aplastic crises in SS disease, but at least 20 percent of infections do not result in aplasia. An effective vaccine against B19 might make an important contribution to the management of sickle cell disease (AU)

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)