Background: The presence of a specific cellular receptor is thought to be necessary for susceptibility to viral infection. The erythrocyte P antigen is the cellular receptor for parvovirus B19. We hypothesized that the rare persons with the p phenotype, whose erythrocytes do not have this receptor, would be naturally resistant to B19 infection, which causes erythema infectiosum.
Methods: Blood samples were collected from two populations in cross-sectional studies. We determined the P antigen phenotype of the red cells and tested plasma for anti-B19-specific antibodies. Bone marrow from donors of known P antigen phenotype was inoculated with parvovirus B19. Infectivity was measured by assays of erythroid progenitor cells, dot blot analysis, and in situ hybridization for B19 DNA, and an immunofluorescence assay for viral-capsid proteins.
Results: Of the 17 subjects with the p red-cell phenotype, who did not have P antigen on their erythrocytes, none (0 of 11 and 0 of 6) had serologic evidence of previous parvovirus B19 infection. In contrast, the seropositivity rates in the two control groups were 71 percent (53 of 75, P < 0.001) and 47 percent (32 of 68, P = 0.03). In vitro, bone marrow from donors with the p phenotype maintained normal erythropoiesis despite very high concentrations of virus, with no evidence of infection of erythroid progenitor cells by parvovirus B19.
Conclusions: People who do not have P antigen, which is the cellular receptor for parvovirus B19, are naturally resistant to infection with this pathogen.