Background
Human parvovirus B19 (B19) is a ubiquitous and clinically significant pathogen, causing erythema infectiosum,
arthropathy, transient aplastic crisis, and intrauterine fetal death. The
phenotype of CD8+ T cells in acute B19
infection has not been studied previously.
Methods and Findings
The number and phenotype of B19-specific CD8+ T cell responses during and after acute adult infection was studied using HLApeptide multimeric complexes. Surprisingly, these responses increased in magnitude over the first year post-infection despite resolution of clinical symptoms and control of viraemia, with T cell populations specific for individual epitopes comprising up to 4 of CD8+ T cells. B19-specific T cells developed and maintained an activated CD38+ phenotype, with strong expression of perforin and CD57 and downregulation of CD28 and CD27. These cells possessed strong effector function and intact proliferative capacity. Individuals tested many years after infection exhibited lower frequencies of B19-specific cytotoxic T lymphocytes, typically 0.050.5 of CD8+ T cells, which were perforin, CD38, and CCR7 low.
Conclusion
This is the first example to our knowledge of an acute human viral infection inducing a persistent activated CD8+ T cell response. The likely explanationanalogous to that for cytomegalovirus infectionis that this persistent response is due to low-level antigen exposure. CD8+ T cells may contribute to the long-term control of this significant pathogen and should be considered during vaccine development.