α5β1 integrin as a cellular coreceptor for human parvovirus B19: requirement of functional activation of β1 integrin for viral entry

Abstract

Replication of the pathogenic human parvovirus B19 is restricted to erythroid progenitor cells. Although blood group P antigen has been reported to be the cell surface receptor for parvovirus B19, a number of nonerythroid cells, which express P antigen, are not permissive for parvovirus B19 infection. We have documented that P antigen is necessary for parvovirus B19 binding but not sufficient for virus entry into cells. To test whether parvovirus B19 utilizes a cell surface coreceptor for entry, we used human erythroleukemia cells (K562), which allow parvovirus B19 binding but not entry. We report here that upon treatment with phorbol esters, K562 cells become adherent and permissive for parvovirus B19 entry, which is mediated by ␣5␤1 integrins, but only in their high-affinity conformation. Mature human red blood cells (RBCs), which express high levels of P antigen, but not ␣5␤1 integrins, bind parvovirus B19 but do not allow viral entry. In contrast, primary human erythroid progenitor cells express high levels of both P antigen and ␣5␤1 integrins and allow ␤1 integrin-mediated entry of parvovirus B19. Thus IntroductionTwo parvoviruses of human origin, the nonpathogenic adenoassociated virus 2 (AAV) and the pathogenic parvovirus B19, have been studied extensively. 1,2 Recombinant AAV vectors have gained attention as a potentially useful alternative to the more commonly used recombinant retroviral and adenoviral vectors in human gene therapy. 3 AAV possesses a broad host range that transcends the species barrier because it utilizes the ubiquitously expressed cell surface heparan sulfate proteoglycan as a primary receptor for viral binding. 4 We and others have reported the requirement of fibroblast growth factor receptor 1 (FGFR1) and ␣V␤5 integrin as coreceptors for viral entry. 5,6 Parvovirus B19, on the other hand, has been shown to have an extremely limited tissue-tropism, and the virus replication is restricted to human erythroid progenitor cells, 7 presumably because (1) the blood group P antigen (synonym "globoside"; "globotetraosylceramide") is used as primary cellular receptor for parvovirus B19, 8 (2) putative intracellular factors, largely restricted to human erythroid cells, are required for optimal transcriptional activation of the B19 promoter at map unit 6 (B19p6) and viral replication, 9,10 and (3) B19 capsid protein expression in nonpermissive cells is impaired due to a block in full-length transcription of the viral genome, atypical mRNA splicing, and impaired ribosome loading of structural gene transcripts. [11][12][13] However, P antigen expression is not restricted to erythroid cells, and a number of P antigen-positive nonerythroid cells are nonpermissive for a successful infection by parvovirus B19. 2 In addition, mature red blood cells (RBCs), which are known to express high levels of P antigen, are unlikely to be ideal targets for B19 infection and replication because they lack nuclei. Similarly, B19p6 promoter-driven expression analyses were carried out with plasmid DNA transfections, 11...

Ex Vivo-Generated CD36 + Erythroid Progenitors Are Highly Permissive to Human Parvovirus B19 Replication

“…We have previously reported that the necessary cellular receptor for B19V infection is globoside (P antigen) (2), and others have reported coreceptors to be ␣5␤1 integrin (37) and/or autoantigen Ku80 (17). The permissiveness to B19V infection of the cells relies primarily on viral entry.…”

“…Antibodies to CD34 (BD Biosciences, Franklin Lakes, NJ), CD36 (BD Biosciences), GPA (BD Biosciences), and CD71 (BD Biosciences) were used for phenotyping. Antibodies against globoside (Matreya, Pleasant Gap, PA), CD49e (BD Biosciences), and KU80 (Calbiochem, San Diego, CA) were used for the detection of B19V cellular receptors (17,37). Flow cytometry was performed using the Beckman Coulter Cytomics FC 500 flow cytometry system (Beckman Coulter, Fullerton, CA).…”

Parvovirus B19 and the Kidney

“…Although the P antigen is necessary for binding of the virus to the cell surface, it is not sufficient for entry and replicative infection in human cells (22,23). Recent studies support the existence of a cellular co-receptor, ␣5␤1 integrin, for successful infection (24), although this remains controversial. This integrin is expressed at high levels on erythroid progenitors, whereas P antigen-positive nonerythroid cells that do not express this co-receptor are considered non-permissive for efficient infection.…”

Childhood Skin Disorders: Genetic Study of the Erythema Infectiosum (Fifth Disease)

“…The viral genome encodes five known, and a possible sixth, protein products: VP1 and VP2 that compose the viral capsid, NS1, the main replicative protein, and two or three smaller proteins of unclear function (7.5 kDa, 11 kDa, and an open reading frame for the putative X protein) [10][11][12]. In addition to erythroid precursor cells, which are permissive for viral replication, B19V can infect a number of different cell types, utilizing the globoside or blood group P-antigen as a receptor13 along with α5β1 integrin [14]. After entry, the viral DNA is shuttled to the nucleus with the host-encoded DNA repair protein Ku80 [15] where replication and transcription occur concurrently following initial conversion of the viral DNA to double-stranded DNA [16,17].…”

“…The single-stranded DNA genome of B19 is packaged into a nonenveloped, icosahedral protein shell of 280 Å in diameter [14]. The capsid consists of 60 structural subunits, 95% of which is the major viral protein VP2 (58 kDa) [15].…”