Peptide Derivatives of Platelet-Derived Growth Factor Receptor Alpha Inhibit Cell-Associated Spread of Human Cytomegalovirus

Abstract

Cell-free human cytomegalovirus (HCMV) can be inhibited by a soluble form of the cellular HCMV-receptor PDGFRα, resembling neutralization by antibodies. The cell-associated growth of recent HCMV isolates, however, is resistant against antibodies. We investigated whether PDGFRα-derivatives can inhibit this transmission mode. A protein containing the extracellular PDGFRα-domain and 40-mer peptides derived therefrom were tested regarding the inhibition of the cell-associated HCMV strain Merlin-pAL1502, hits were validated with recent isolates, and the most effective peptide was modified to increase its potency. The modified peptide was further analyzed regarding its mode of action on the virion level. While full-length PDGFRα failed to inhibit HCMV isolates, three peptides significantly reduced virus growth. A 30-mer version of the lead peptide (GD30) proved even more effective against the cell-free virus, and this effect was HCMV-specific and depended on the viral glycoprotein O. In cell-associated spread, GD30 reduced both the number of transferred particles and their penetration. This effect was reversible after peptide removal, which allowed the synchronized analysis of particle transfer, showing that two virions per hour were transferred to neighboring cells and one virion was sufficient for infection. In conclusion, PDGFRα-derived peptides are novel inhibitors of the cell-associated spread of HCMV and facilitate the investigation of this transmission mode.

Viral and Cellular Factors Contributing to the Hematogenous Dissemination of Human Cytomegalovirus via Polymorphonuclear Leukocytes

“…Thus, the strong effect on PMN-mediated transmission of HCMV could be due to the fact that in the absence of pp65 or pp71, virions are either more poorly packaged or even released in lower numbers as mature virus particles from the infected donor cultures. During focal growth of the mutants in fibroblast monolayers, this circumstance might be overcome by the high multiplicity of infection that is observed for the cell-associated spread of HCMV [ 35 , 37 ]. Since we have demonstrated that the tegument proteins pp65 and pp71 contribute to the pathophysiologically relevant dissemination via leukocytes, the use of one of these proteins as a potential candidate for a future HCMV vaccine might be even more approachable.…”

“…A soluble derivative thereof, PDGFRα-Fc, can bind to cell-free virions and inhibit entry into fibroblasts, endothelial and epithelial cells, but it could not inhibit PMN-mediated transfer [ 20 , 30 , 33 ]. In contrast to the failure of these large decoy receptors, smaller peptide fragments derived from the extracellular PDGFRα domains 1–3 [ 33 , 35 ] reduced the efficiency of virus transmission by PMNs when added either during the initial uptake step or during the subsequent transfer step [ 20 ]. Similar phenomena are observed for the spread of clinical HCMV isolates in fibroblast cultures.…”

“…Similar phenomena are observed for the spread of clinical HCMV isolates in fibroblast cultures. While large entry inhibitors such as PDGFRα-Fc or neutralizing antibodies did not inhibit the strictly cell-associated growth of these viruses [ 35 , 36 , 37 ], PDGFRα-derived peptides reduced the number and size of infected foci [ 35 ]. The finding that large entry inhibitors fail to reduce cell-associated spread of HCMV isolates or transmission via PMNs, whereas smaller derivatives prove effective, also prompts considerations regarding the virus-cell interactions underlying this viral mode of transmission.…”

Relationship of human cytomegalovirus‐infected endothelial cells and circulating leukocytes in the pathogenesis of disseminated human cytomegalovirus infection: A narrative review

“…[92][93][94] In addition, scFv have been used against subunits of pentamer complex, 95 thus promising to be useful in the control of PMNL-mediated HCMV transmission. 96 By using: i) immortalised human endothelial cells 97 and human foetal fibroblasts; ii) PMNL derived from HCMV-seronegative blood donors; iii) the Merlin HCMV reference strain, 98 as a parental BAC clone comprising the entire wild-type HCMV genome; iv) four KO genes [UL128 (pentamer complex), UL74 (gO), UL83 (pp65), and UL82 (pp71)], which were generated by introduction into each gene of two stop codons, according to markerless mutagenesis, 99 the following results were obtained 90 in both directions of PMNL uptake and transmission.…”

Growth defect of domain III glycoprotein B mutants of human cytomegalovirus reverted by compensatory mutations co-localizing in post-fusion conformation

“…Cell culture-adapted strains, however, have at least partially lost this spread mode due to genomic alterations which mostly occur in the accessory proteins of the pentamer or in the RL13 locus [18,19]. gB and gH/gL complexes are required for both, the cell-free and the cell-to-cell spread as for example small inhibitors directed towards gO of the trimer [20,21] or towards gB [22] are able to inhibit both modes of spread. The pentamer can alternatively be used for cell-associated spread on fibroblasts and is sufficient for epithelial cell spread even without the presence of the trimer [23][24][25][26].…”