Erik Larsson

ERV3 and Related Sequences in Humans: Structure and RNA Expression

ABSTRACT The ERV3 locus at chromosome 7q11 is a much studied human endogenous retroviral (HERV) sequence, owing to an env open reading frame (ORF) and placental RNA and protein expression. An analysis of the human genome demonstrated that ERV3 is one of a group of 41 highly related elements (ERV3-like HERVs) which use proline, isoleucine, or arginine tRNA in their primer binding sites. In addition to elements closely related to ERV3, the group included the previously known retinoic acid-inducible element, RRHERVI, also referred to as HERV15, but was separate from the related HERV-E elements. The ERV3-like elements are defective. The only element with an ORF among gag, pro, pol, and env genes was the env ORF of the original ERV3 locus. A search in dbEST revealed ERV3 RNA expression in placenta, skin, carcinoid tumor, and adrenal glands. Expression was also studied with newly developed real-time quantitative PCRs (QPCR) of ERV3 and HERV-E(4-1) env sequences. Results from a novel histone 3.3 RNA QPCR result served as the expression control. QPCR results for ERV3 were compatible with previously published results, with a stronger expression in adrenal gland and placenta than in 15 other human tissues. The expression of the envelope (env) of ERV3 at chromosome 7q11 was also studied by using stringent in situ hybridization. Expression was found in corpus luteum, testis, adrenal gland, Hassals bodies in thymus, brown fat, pituitary gland, and epithelium of the lung. We conclude that ERV3 env is most strongly expressed in adrenal and sebaceous glands as well as in placenta.

Expression of the endogenous retrovirus ERV3 (HERV-R) during induced monocytic differentiation in the U-937 cell line

ERV3 (HERV‐R) is a complete human endogenous retrovirus located on the long arm of chromosome 7. LTR‐env‐gene‐spliced mRNA of 9 and 3.5 Kb is widely expressed in human tissues and cells, but gag‐pol mRNA has not been found. Further, the env gp70 gene contains an open reading frame throughout its length and its expression has recently been detected as a full‐length protein. The highest expression of ERV3 detected so far is in placenta and the lowest in cytotrophoblasts and choriocarcinoma cell lines. In this report we have studied ERV3 mRNA and protein expression in the human monoblastic cell line U‐937 during differentiation into monocytes/macrophages. Differentiation of U‐937 cells was induced by 1,25a‐dihydroxyvitamin D3 (vitD3), retinoic acid (RA), gamma interferon (IFN‐γ) and phorbol‐myristate‐acetate (PMA‐TPA). The expression of ERV3 env mRNA was found to be differentiation‐associated, with high expression detected in the late stages of monocytic development. Using TPA, the expression of ERV3 env was detected as 9‐ and 3.5‐kb transcripts by Northern blotting, as mRNA by in situ hybridization and as a cytoplasmic 65‐kDa protein by immunofluorescence and Western blots. Low levels of basal expression were found, with up‐regulation of both message and protein at 24 to 48 hr after addition of TPA. Induction with vitD3, IFN‐γ and RA produced higher levels of mRNA at earlier time points. It is concluded that the U‐937 cell line represents an excellent model system for further studies to study the relationship between ERV3 expression and cellular differentiation.

Active cytomegalovirus infection in aortic smooth muscle cells from patients with abdominal aortic aneurysm.

Cytomegalovirus (CMV) is associated with atherosclerosis and transplant vascular sclerosis. The aim of this study was to explore the hypothesis that active CMV infection in the vessel wall could be associated with abdominal aortic aneurysm (AAA). We examined the prevalence of CMV in AAA specimens from 22 patients undergoing surgery and, in five cases, characterized the function of smooth muscle cells (SMCs) from the aneurysm in vitro. Twenty-one (95%) of the 22 AAA specimens were CMV positive by a polymerase chain reaction assay, in situ hybridization, or a highly sensitive immunohistochemical staining technique. No positive cells were found in aortas from three CMV-seronegative organ donor cadavers. CMV immediate-early and late antigens were expressed in SMCs in the lesions and were associated with 5-lipoxygenase (5-LO) expression. CMV-positive intimal SMCs migrated 6.6 ± 1.5 times more efficiently than CMV-negative medial SMCs (p < 0.05). In vitro CMV infection of medial SMCs resulted in a 3.2 ± 1.2 times increase in migration (p < 0.05). The intimal migration was significantly inhibited by antibodies against basic fibroblast growth factor (bFGF; p < 0.05) in a dose-dependent fashion. Antibodies against platelet-derived growth factor (PDGF)-AB, insulin-like growth factor 1, vascular endothelial growth factor (VEGF), RANTES, monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein (MIP)-1α, or interleukin-1β did not significantly affect intimal SMC migration. However, intimal and medial SMCs secreted similar amounts of bFGF, MCP-1, MIP-1α, RANTES, PDGF-AB, PDGF-BB, epidermal growth factor, and VEGF. CMV infection in vitro of intimal and medial cells did not result in significant changes of bFGF or MCP-1 secretion. Since CMV infection can affect several functional parameters in SMCs, including several key factors in infected SMCs, our findings provide support for the hypothesis that CMV contributes to the pathogenesis of abdominal aortic aneurysm.

First known case of Bartonella quintana endocarditis in Sweden

In this report, we present the first known case of Bartonella endocarditis in Sweden. IgG antibody titres to Bartonella spp. were elevated but blood cultures remained negative. Sequencing of a gltA fragment from DNA extracted from heart valve tissue specimens revealed sequence homology with B. quintana.