B J Cohen

The prevalence of antibody to human parvovirus B19 (anti-B19 IgG) in England and Wales was measured by an antibody-capture radioimmunoassay. Over 2000 sera were examined; 1422 from the general population, 374 from unselected children admitted to hospital and 300 from women attending an antenatal clinic. Waning levels of maternally-derived antibody were found in infants under 1 year old. In children 1-5 years old, 5-15% had anti-B19 IgG and this rose to 50-60% in older children, young adults and women of child-bearing age. In older people, the prevalence of anti-B19 IgG increased with age, rising to more than 85% in those over 70 years old.

Erythema infectiosum (EI) or fifth disease is a mild, acute exanthematous disease, occurring mainly among children, for which a causative virus has long been sought. In May 1983 an outbreak of exanthematous illness was reported in a primary school in North London. Children attending the school were investigated by questionnaire and 162 (43.9%) reported an illness with the features of EI. In each of 36 cases investigated virologically the illness was associated with parvovirus infection. Moreover, pre-existing antibody to parvovirus was correlated with protection from EI in 16 of 17 close family contacts of cases. We propose therefore that EI is the common manifestation of infection with the human parvovirus.

Monoclonal antibodies to the serum parvovirus-like virus (SPLV) were prepared by the hybridoma technique. They provided an antibody reagent which was used to develop solid phase antibody-capture assays for anti-SPLV IgM and IgG and for SPLV antigen. These assays were more sensitive than those based on human convalescent antibody as a reagent, and were more economical in the use of SPLV antigen. Their use enabled the serological responses to SPLV to be studied more fully and their sensitivity revealed the extent of SPLV infection. SPLV antigen was detected in four patients by both counter-immuno electrophoresis (CIE) and radioimmunoassay (RIA) and in two others by RIA alone. Parvovirus particles were seen in all six by electron microscopy. The anti-SPLV IgM response was measured in patients infected by SPLV. It was strong 5-18 days after the onset of illness, then declined and was only detectable in trace amounts after 6 months. Anti-SPLV IgG was also formed early, and persisted for at least 6 months. In a survey of 310 blood donors anti-SPLV was detected in 134 (43%) by CIE, but in 190 (61%) by IgG antibody capture RIA.