Identification and characterization of persistent human erythrovirus infection in blood donor samples

Abstract

The presence of human erythrovirus DNA in 2,440 blood donations from the United Kingdom and sub-Saharan Africa (Ghana, Malawi, and South Africa) was screened. Sensitive qualitative and real-time quantitative PCR assays revealed a higher prevalence of persistent infection with the simultaneous presence of immunoglobulin G (IgG) and viral DNA (0.55 to 1.3%) than previously reported. This condition was characterized by a low viral load (median, 558 IU/ml; range, 42 to 135,000 IU/ml), antibody-complexed virus, free specific IgG, and potentially infectious free virus. Human erythrovirus genotype 1 (formerly parvovirus B19) was prevalent in the United Kingdom, Malawi, and South Africa. In contrast, only human erythrovirus genotype 3 (erythrovirus variant V9) was prevalent in Ghana. Genotype 3 had considerable genetic diversity, clustering in two probable subtypes. Genotype 1-based antibody assays failed to detect 38.5% of Ghanaian samples containing antibodies to genotype 3 virus but did not fail to detect cases of persistent infection. This study indicates a potential African origin of genotype 3 human erythrovirus and considerable shortcomings in the tools currently used to diagnose erythrovirus infection.

FIG. 1.

Phylogenetic relationships among human erythrovirus NS1 and VP1u sequences. Four sequences from the United Kingdom, 12 from Ghana, 2 from South Africa, and 1 from Malawi were aligned with 19 human erythrovirus reference sequences from the GenBank database. The three major lineages of human erythrovirus are indicated by the branches. Reference strains are identified by their GenBank accession numbers. The sequences determined in this study are indicated by boldface characters. Only significant bootstrap values (≥75%) are shown.

FIG. 2.

Alignment of VP1u partial amino acid sequences of human erythrovirus genotypes 1 and 3. The sequences determined in this study were aligned with the sequence of the genotype 1 reference strain Pvbaua (GenBank accession number M13178); the sequence of strain V9 (GenBank accession number AX003421) was added for comparison within the genotype 3 group. Residues identical to those in the Pvbaua sequence are indicated by dashes. The numbering of the residues starts at the NH2 terminus of VP1u.

FIG. 3.

Free and IgG-complexed viruses in six human erythrovirus-infected plasma samples. Antibodies to erythrovirus were detected by using a genotype 1 VP2-based commercial EIA. id, identification.

FIG. 4.

Amino acid substitutions between free and IgG-complexed viruses in five cases of persistent human erythrovirus infection. Partial NS1 (A) and VP1u (B) amino acid sequences of viruses retained (R) and not retained (NR) on protein G columns were aligned. To facilitate the viewing, only differences within each sample are shown, and their positions in the NS1 and VP1u proteins are indicated according to the sequence of reference strain Pvbaua (GenBank accession number M13178).