Human cytomegalovirus clinical isolates carry at least 19 genes not found in laboratory strains

Abstract

Nucleotide sequence comparisons were performed on a highly heterogeneous region of three human cytomegalovirus strains, Toledo, Towne, and AD169. The low-passage, virulent Toledo genome contained a DNA segment of approximately 13 kbp that was not found in the Towne genome and a segment of approximately 15 kbp that was not found in the AD169 genome. The Towne strain contained approximately 4.7 kbp of DNA that was absent from the AD169 genome, and only about half of this segment was present, arranged in an inverted orientation, in the Toledo genome. These additional sequences were located at the unique long (U L)/b (IR L) boundary within the L component of the viral genome. A region representing nucleotides 175082 to 178221 of the AD169 genome was conserved in all three strains; however, substantial reduction in the size of the adjacent b sequence was found. The additional DNA segment within the Toledo genome contained 19 open reading frames not present in the AD169 genome. The additional DNA segment within the Towne genome contained four new open reading frames, only one of which shared homology with the Toledo genome. This comparison was extended to five additional clinical isolates, and the additional Toledo sequence was conserved in all. These findings reveal a dramatic level of genome sequence complexity that may explain the differences that these strains exhibit in virulence and tissue tropism. Although the additional sequences have not altered the predicted size of the viral genome (230 to 235 kbp), a total of 22 new open reading frames (denoted UL133 to UL154), many of which have sequence characteristics of glycoproteins, are now defined as cytomegalovirus specific. Our work suggests that wild-type virus carries more than 220 genes, some of which are lost by large-scale deletion and rearrangement of the U L /b region during laboratory passage.

Human Cytomegalovirus Elicits a Coordinated Cellular Antiviral Response via Envelope Glycoprotein B

“…We assessed the antiviral response of human endothelial cells to two distinct CMV strains. The fibroblast-adapted AD169 strain is highly attenuated in humans and contains a large genomic deletion compared to clinical isolates (13,17). In contrast, the endothelium-tropic VHL/E strain has been maintained exclusively in endothelial cells and is predicted to retain a higher degree of genetic similarity to CMV clinical isolates than to AD169 (46).…”

The Human Cytomegalovirus-Specific UL1 Gene Encodes a Late-Phase Glycoprotein Incorporated in the Virion Envelope

“…Sequence analyses of the HCMV genome showed that as many as 70 putative glycoprotein-encoding ORFs are found in clinical isolates (11) and that 57 are found in the AD169 strain (13). HCMV structural glycoproteins can be divided into two broad classes, those conserved between members of the family Herpesviridae (including gB, gH, gL, gM, and gN) and subgenus-specific glycoproteins without homology to other herpesviruses, comprised of, among others, gpTRL10 (51), gpRL13 (53), gpUL132 (52), UL74-encoded gO (29), UL4-encoded gp48 (12), US27 (24), and UL33 (34).…”

Early inhibitors of human cytomegalovirus: State-of-art and therapeutic perspectives

“…Most of the studies that support a role for EGFR and integrins as entry receptors were carried out by infecting fibroblasts with the HCMV laboratory strain AD169. This strain harbors deletions, mutations, and rearrangements within a genomic area that comprises the UL128, UL130, and UL131 genes which are important determinants of HCMV tropism for endothelial and epithelial cells (Cha et al, 1996;Murphy et al, 2003;Dolan et al, 2004;Hahn et al, 2004;Wang & Shenk, 2005a. The role of EGFR and integrins as entry receptors has not been confirmed for epithelial and endothelial cells infected with viral strains endowed with a broader cell tropism.…”