Comparison of efficiency of infection of human gene therapy target cells via four different retroviral receptors

The relative efficiency of transduction of gene therapy target cells was measured for retroviruses bearing the envelopes of amphotropic murine leukemia virus (MLV-A), xenotropic murine leukemia virus (MLV-X), gibbon ape leukemia virus (GALV), feline leukemia virus subgroup B (FeLV-B), and the feline endogenous virus RD114. These viruses use various cell-surface receptors. Activated peripheral blood lymphocytes (PBL) and primary melanoma cultures were infected relatively poorly by MLV-X pseudotypes. RD114 pseudotypes infected PBL relatively well, whereas bone marrow progenitor cells were efficiently infected by all viruses. Helper-free virus bearing the envelopes of MLV-A, RD114, or GALV was similarly tested. All infected melanoma or bone marrow progenitor cells efficiently, whereas MLV-A was relatively inefficient for infection of PBL. The general utility of RD114 pseudotyped virus for gene delivery coupled with its resistance to inactivation by human serum makes this envelope the most suitable choice for in vivo gene therapy.

Retrovirus classification and cell interactions

Retroviruses cause a variety of diseases such as cancer, AIDS, autoimmunity and diseases of central nervous system, bone and joints. Some retroviruses are apparently harmless and some retroviral genomes are even inherited as host mendelian traits. Whereas oncoviruses generally have a low virus load, so that antiviral therapy would not greatly affect disease progression, lentiviruses like HIV have high load and turnover. The cell interactions of retroviruses largely determine their pathogenesis. Finally, retroviruses are being exploited therapeutically as vectors for gene therapy.

Human endogenous retrovirus expression and reverse transcriptase activity in the T47D mammary carcinoma cell line

We have examined the human mammary tumor cell line T47D and have found that these cells produce virus-like particles which band at the typical density for retroviral particles on a sucrose gradient, possess reverse transcriptase activity, and package HERV-K10-like sequences. Using this information and a bacterial expression system to identify long open reading frames, we have identified individual clones which have full-length open reading frames for reverse transcriptase and RNase H and which could encode the reverse transcriptase activity detected in these cells.

Magnetic resonance imaging findings in a case of advanced Coats' disease

Coats' disease is an idiopathic, primary vascular anomaly of the retina often presenting with retinal detachment. In this report, the unusual radiologic findings of a 17-month-old patient with advanced Coats' disease are discussed. Computed tomography (CT) showed diffuse increased density of the right eye. Magnetic resonance imaging (MRI) demonstrated moderately hyperintense signal intensity on T1-weighted images, mildly hypointense signal intensity on T2-weighted images, and linear enhancement of the leaves of the detached retina with intense enhancement in the retinal periphery following gadolinium-diethylenetriamine penta-acetic acid (DTPA) contrast administration. The hypointense T2-weighted images and the linear enhancement of the detached retina have not been reported previously in cases of Coats' disease. These observations correlated with the histopathologic features, which showed a totally detached retina containing large telangiectatic vesses and a supretinal space occupied by eoinophilic proteinaceous exudates containing abundant cholesterol crystals. It appears that the MRI characteristics observed in Coats' disease may vary depending on the nature of the subretinal exudate and the severity of the disease.

Kaposi's sarcoma-associated herpesvirus and Kaposi's sarcoma in Africa. Uganda Kaposi's Sarcoma Study Group

BACKGROUND

Endemic Kaposi's sarcoma (KS) is a clinically and epidemiologically distinct human immunodeficiency virus negative form of KS occurring in Africa. Kaposi's sarcoma is now the most frequently reported cancer in some areas of Africa.

OBJECTIVE

To determine if a KS-associated herpesvirus (KSHV) is present in both endemic HIV-seronegative and HIV-seropositive KS lesions from African patients.

METHODS

Paraffin-embedded tissue specimens from Ugandan patients with KS and non-KS tumor control patients attending a university-based oncology clinic were examined in a blinded case-control study. Tissue DNA specimens were examined for detectable KSHV genome by nested polymerase chain reaction performed at two independent laboratories.

RESULTS

We identified KSHV in 17 (85%) of 20 KS tissue specimens from HIV-seronegative patients and 22 (92%) of 24 KS tissue specimens from HIV-infected persons. Kaposi's sarcoma lesions from four HIV-infected persons and four HIV-seronegative persons were positive for KSHV. Unlike previous studies in North America and Europe, three (14%) of 22 non-KS cancer control patients' tissue specimens were also positive for KSHV that resulted in an overall odds ratio of 49.2 (95% confidence interval, 9.1 to 335) for detecting KSHV in KS lesions from patients in Uganda.

CONCLUSION

As in North America and Europe, KSHV infection is strongly associated with both HIV-seropositive and HIV-seronegative KS in Africa. However, it is likely that infection with this virus is more highly prevalent in Uganda.

Sensitization of cells and retroviruses to human serum by (alpha 1-3) galactosyltransferase

Mammalian C-type retroviruses are inactivated by human serum, following triggering of the classical complement cascade. This may have inhibited transmission to humans of C-type oncoviruses from other mammals. Indeed, the retroviruses human immunodeficiency virus and human T-cell leukaemia virus are resistant to human complement. Antibody-independent activation of human C1q, the first component of the classical pathway, by retroviral envelope proteins has been described. However, retroviruses produced from human cells are resistant to inactivation by human complement and human serum is known to contain antibodies directed against carbohydrates on retroviral envelopes. Gal(alpha 1-3)Gal terminal carbohydrates are expressed by most mammals but are absent in humans, which lack a functional (alpha 1-3)galactosyltransferase gene. Here, we demonstrate that anti-Gal(alpha 1-3)Gal antibodies in human serum inactivate retroviruses produced from animal cells. Expression of porcine (alpha 1-3)galactosyltransferase in human cells renders the cells and the retroviruses they produce sensitive to human serum.

High-titer packaging cells producing recombinant retroviruses resistant to human serum

Novel retroviral protein expression constructs were designed to retain minimal retroviral sequences and to express dominant selectable markers by reinitiation of translation after expression of the viral genes. HT1080 cells were selected as producer cells for their ability to release high-titer viruses that are resistant to inactivation by human serum. Two HT1080-based packaging cell lines which produce Moloney murine leukemia virus cores with envelope glycoproteins of either amphotropic murine leukemia virus (FLYA13 line) or cat endogenous virus RD114 (FLYRD18 line) are described. Direct comparison with previous retroviral packaging systems indicated that 100-fold-higher titers of helper-free recombinant viruses were released by the FLYA13 and FLYRD18 lines.

Kaposi's sarcoma-associated herpesvirus infects endothelial and spindle cells

Kaposi's sarcoma (KS), a vascular tumour that contains characteristic spindle cells forming slit-like spaces, may have an infectious aetiology. Recently, sequences of a new human herpesvirus, KSHV/HHV-8, have been identified in both HIV-associated and classical KS. We sought to identify the target cell of this virus in KS tumour tissue. Using PCR in situ hybridization (PCR-ISH) we show that KSHV/HHV-8 is present in the flat endothelial cells lining vascular spaces of KS lesions as well as in typical KS spindle cells. These findings show that KSHV/HHV-8 is present in the cell types thought to represent neoplastic cells in these lesions.

Cell cycle dependence of foamy retrovirus infection

In common with oncoviruses but unlike the lentivirus human immunodeficiency virus type 1, foamy (spuma) viruses require host cell proliferation for productive infection. We show that human immunodeficiency virus type 1 replicates in RD-CD4 cells regardless of the growth arrest condition of the cells, while murine leukemia virus is unable to infect growth-arrested RD-CD4 cells or cells progressing through a partial cell cycle that includes S phase but not mitosis. Human foamy virus, like murine leukemia virus, does not productively infect G1/S or G2 growth-arrested cells. Two other foamy viruses, simian foamy virus type 1, isolated from a macaque, and simian foamy virus type 6, isolated from a chimpanzee, also fail to establish productive infection in G1/S-arrested cells.

Sclerotherapy. Continuous wave Doppler-guided injections

BACKGROUND

The usual method of injection of sclerosing agents is based simply on clinical recognition and visualization of the varicose vein.

OBJECTIVE

The authors present an original technique for sclerosing injections, named Doppler sclerotherapy. The purpose is to allow more accurate sclerotherapy in situations where varicose veins (usually greater than 4-5 mm) are not palpable in the supine position, but palpable when standing.

METHODS

This technique consists of injecting the sclerosing agent using an uncomplicated continuous wave Doppler, a syringe, and a needle, according to a method consisting of four well-defined steps ensuring avoidance of arterial vessels and constant appreciation of the varicose vein to be treated, even during the injection. It requires no assistants and allows the treating physician's gaze to remain at the injection site while listening for very specific Doppler sounds of aspiration and injection.

RESULTS

In our multicenter study of 220 patients (approximately 1,400 injections) all but 18 injections were successful for intravascular localization. No serious complications were noted.

CONCLUSIONS

The principal indication is the treatment of varicose veins that are palpable while standing but impalpable in the supine position. In addition varicose veins in the groin region, lower third of the thigh, and along the axis of the small saphenous vein may be treated with this technique. In these situations it is a more accessible, faster, and economical technique, although it does not replace duplex ultrasound-guided injections.

Retroviral retargeting by envelopes expressing an N-terminal binding domain

We have engineered ecotropic Moloney murine leukemia virus-derived envelopes targeted to cell surface molecules expressed on human cells by the N-terminal insertion of polypeptides able to bind either Ram-1 phosphate transporter (the first 208 amino acids of amphotropic murine leukemia virus surface protein) or epidermal growth factor receptor (EGFR) (the 53 amino acids of EGF). Both envelopes were correctly processed and incorporated into viral particles. Virions carrying these envelopes could specifically bind the new cell surface receptors. Virions targeted to Ram-1 could infect human cells, although the efficiency was reduced compared with that of virions carrying wild-type amphotropic murine leukemia virus envelopes. The infectivity of virions targeted to EGFR was blocked at a postbinding step, and our results suggest that EGFR-bound virions were rapidly trafficked to lysosomes. These data suggest that retroviruses require specific properties of cell surface molecules to allow the release of viral cores into the correct cell compartment.

Abundance of an endogenous retroviral envelope protein in placental trophoblasts suggests a biological function

To investigate the hypothesis that the human endogenous sequence ERV-3 has a function, we have cloned and expressed the transmembrane region of its envelope gene and raised specific antibodies to the fusion protein and to a synthetic peptide. These antibodies reacted with a 65-kDa polypeptide which constituted approximately 0.1% of the cellular protein in syncytiotrophoblasts in placenta. The evolutionary conservation and abundant expression of this endogenous retroviral protein in a specific cell type support the concept of a biological function. The similarity of a domain of ERV-3 env to putative immunosuppressive p15E sequences suggests that ERV-3 might form part of the placental immunosuppressive barrier between mother and foetus.

Reduced glycosylation of human cell lines increases susceptibility to CD4-independent infection by human immunodeficiency virus type 2 (LAV-2/B)

The human immunodeficiency virus type 2 (HIV-2) strain LAV-2/B is able to infect a variety of human cell lines via a CD4-independent pathway. We have used the glycosylation inhibitors tunicamycin, swainsonine, and deoxymannojirimycin to further characterize this putative alternative receptor for HIV-2 (LAV-2/B). These antibiotics resulted in an increase (5- to 30-fold) in the susceptibility of a variety of CD4- human cell lines to infection by LAV-2/B (RD, HeLa, HT29, Rsb, Heb7a, Hos, and Daudi). Several nonprimate cell lines (mink Mv-1-lu, rabbit SIRC, hamster a23, mouse NIH 3T3, cat CCC, and rat HSN) remained resistant to infection by LAV-2/B after treatment with glycosylation inhibitors, suggesting that they do not express the HIV-2 CD4-independent receptor. Two of these nonprimate cell lines are readily infected by HIV-2 when they express CD4 (Mv-1-lu and CCC). Treatment of human cells with neuraminidase had no effect on subsequent infection by LAV-2/B, suggesting that the increase in susceptibility to infection of deglycosylated cells is not due to a change in the electrostatic charge of the cell surface. Treatment of RD CD4- cells and HeLa CD4+ cells with a variety of proteases resulted in a 75 to 90% decrease in infection by LAV-2/B when compared with untreated cells. Taken together, all these data suggest that HIV-2 can utilize a membrane glycoprotein other than CD4 to attach and fuse with a variety of human cells.