Parvovirus B19 Replication and Expression in Differentiating Erythroid Progenitor Cells

Abstract

The pathogenic Parvovirus B19 (B19V) is characterized by a strict adaptation to erythroid progenitor cells (EPCs), a heterogeneous population of differentiating cells with diverse phenotypic and functional properties. In our work, we studied the dynamics of B19V infection in EPCs in dependence on the cell differentiation stage, in terms of distribution of infected cells, synthesis of viral nucleic acids and production of infectious virus. EPCs at early differentiation stage led to an abortive infection, without viral genome replication and a very low transcriptional activity. EPCs at later stages were permissive, with highest levels of viral replicative activity at day 9 (+3.0 Log from 2 to 48 hpi) and lower levels at day 18 (+1.5 Log from 2 to 48 hpi). B19V DNA increment was in accordance with the percentage of cells positive to flow-FISH assay (41.4% at day 9, 1.1% at day 18). Quantitation of total RNA indicated a close association of genome replication and transcription with viral RNA accumulation within infected cells related to viral DNA increase during the course of infection. Analysis of the different classes of mRNAs revealed two distinct pattern of genome expression profile with a fine regulation in the frequency utilization of RNA processing signals: an early phase, when cleavage at the proximal site leading to a higher relative production of mRNA for NS protein, and a late phase, when cleavage at the distal site was more frequent leading to higher relative abundance of mRNA for VP and 11 kDA proteins. Infectious virus was released from cells at day 6–15, but not at day 18. Our results, providing a detailed description of B19V replication and expression profile in differentiating EPCs, highlight the very tight adaptation of B19V to a specific cellular target defined both by its erythroid lineage and its differentiation stage.

The VP1u Receptor Restricts Parvovirus B19 Uptake to Permissive Erythroid Cells

“…In order to define the correlation of the VP1u receptor expression with the cellular permissivity for B19V infection, we expanded CD34+ hematopoietic stem cells ex vivo towards the erythroid lineage [4,5,6,16] and tested the MS2-VP1u internalization, virus uptake and infection along the differentiation. The results show that MS2-VP1u internalization (Figure 4A), B19V uptake (Figure 4C) and virus infection (Figure 4D) all show a similar profile along the erythroid development.…”

“…It is thought that this extreme tropism is determined by intracellular permissivity factors as well as by a specific internalization into this cell type [4,5,7]. Previous studies have shown that only erythroid cells around the proerythroblast stage support efficient viral replication and production of infectious progeny [3,4,5,6]. To avoid predominant and abortive infections into non-permissive cells, B19V needs to restrict the virus uptake to permissive erythroid differentiation stages.…”

“…In the past, several studies have used ex vivo expansion of CD34+ hematopoietic stem cells isolated from peripheral blood mononuclear cells or bone marrow to define the tropism of B19V along the erythroid differentiation [4,5,6,32,34]. The stimulation of the isolated CD34+ cells with erythropoiesis-supporting cytokines as SCF, IL-3 and EPO generally led to an increase of the permissivity between days 2–4 of the expansion [4,6] (Figure 4D).…”

“…The cellular tropism of B19V is strongly restricted to intermediate erythroid differentiation stages, where the susceptibility increases from erythroid progenitors to erythroblasts [2]. Studies using ex vivo expanded cluster of differentiation (CD) 34+ hematopoietic stem cells show the highest permissivity in erythropoietin-dependent erythroid differentiation stages—colony forming unit-erythroid (CFU-E), proerythroblasts and early basophilic erythroblasts [3,4,5,6]. The extraordinarily narrow tropism is supposed to be determined by both a restricted receptor expression and intracellular factors [7].…”

Parvovirus B19 integration into human CD36+ erythroid progenitor cells

“…Not all erythropoietic cells are equally permissive for viral replication (Bua et al, 2016; Takahashi et al, 1990). B19V infects EPCs by binding P antigen (glycosphingolipid globoside), the primary B19V receptor (Brown et al, 1993).…”