Demonstration of cytomegalovirus and retrovirus pseudotypes in cultured guinea pig cells

Visualisation of phenotypically mixed HIV-1 and HTLV-I virus particles by electron microscopy

Virions produced after HIV-1 infection of HTLV-I transformed cells have an expanded tropism that has been attributed to the presence of HTLV-I glycoproteins in the envelope. This report now directly identifies these phenotypically mixed virions by immunogold labelling electron microscopy. Furthermore we estimate there are 2% of these in cell-free supernatant, which represents up to 1 x 10(7) particles/ml from an in vitro infection. HTLV-1 envelope labelling was localised to a single region, suggesting a defined event in packaging of foreign envelope proteins into HIV-1 virus particles.

HIV-1 DNA in fibroblast cultures infected with urine from HIV-seropositive cytomegalovirus (CMV) excretors

Interactions between HIV-1 and CMV may be important in the pathogenesis of AIDS. We have studied whether active CMV infection alters the cell tropism of HIV-1 in dually-infected individuals. Urines from HIV-seropositive individuals excreting CMV were compared to urines from CMV non-excretors. Sixty-six urines from HIV-seropositive individuals were tested. Infectious HIV-1 was not detected in any of the concentrated urines tested. The urines were filtered, concentrated, DNase-treated and cultured on HIV-1 non-permissive human forestin fibroblasts. HIV-1 DNA was detected by PCR with pol gene primers in 5 of 39 MRHF cell cultures inoculated with CMV culture positive urine (p = 0.037). HIV-1 DNA was not detected by PCR in uninfected fibroblasts, in fibroblasts inoculated with CMV uninfected urine from 27 HIV-seropositive patients or in fibroblasts cultured with 9 CMV culture positive urines from 16 HIV-seronegative renal transplant recipients. Supernatant fluid from an HIV-1 PCR-positive culture was passaged onto another fibroblast monolayer, and these cells were negative for HIV-1 DNA. Direct inoculation of fibroblasts with HIV-1 did not yield evidence of infection by PCR. CMV infection may facilitate HIV-1 DNA entry into ordinarily non-permissive cells.

Characterization of conditions for the activation of endogenous guinea pig retrovirus in cultured cells by 5-bromo-2'-deoxyuridine

Human endogenous retroviral sequences recently have been shown to be associated with breast cancer and some leukemias. These retroviral sequences have similarities to an endogenous retrovirus expressed in guinea pigs. The conditions for activation of this guinea pig retrovirus (GPRV) in cultured guinea pig embryo (GPE) cells using 5-bromo-2'-deoxyuridine (BrdU) was investigated. These studies employed the reverse transcriptase activity (RT) assay and electron microscopy (EM), in conjunction with Northern blot analysis that utilized a 2.6 kb GPRV-specific cDNA probe. Contrary to published studies, dexamethasone at concentrations ranging from 10(-8) to 10(-5) M appeared to play a minimal role in enhancing the production of GPRV. Following a 6 hr incubation with BrdU, GPRV mRNA was present in cultured GPE cells. Extracellular virion release was also observed by EM 12 hr later, although RT activity was not detected. All three methods detected viral expression at 48 hr after the addition of the drug. Additionally, after 6 hr exposure to BrdU, detectable RT and mRNA levels were maintained through 44 days after the removal of BrdU in a stationary culture condition and through 31 days in cultures that were subcultured weekly in media not containing BrdU. Low levels of extracellular viruses were detected in these cultures by electron microscopy through 49 days. Therefore, after only a 6 hr exposure to BrdU was extracellular GPRV detected 12 hr after drug removal and virus production continued for up to 49 days. This study provides information about an animal endogenous retroviral system that may be used as a model for the study of human endogenous retroviruses.

Re-examination of the McCoy cell line for confirmation of its mouse origin: karyotyping, electron microscopy and reverse transcriptase assay for endogenous retrovirus

BACKGROUND

The McCoy cell line originally derived from human synovial fluid in 1955, has been later found useful for cultivation of Chlamydia trachomatis. This cell line has been subcultured and exchanged between laboratories for many years. In recent years, the McCoy cell line has been widely used in many clinical diagnostic laboratories and has been supplied through commercial companies for the isolation and identification of Chlamydia trachomatis from clinical specimens.

OBJECTIVES

Since retrovirus-like particles have been observed in McCoy cells and the species of origin of the currently used cell line has not been adequately documented, further characterization of McCoy cell line obtained from commercial sources was carried out.

STUDY DESIGN

This study includes karyotypes analysis using G-banding for the confirmation of species origin of McCoy cells, electron microscopy for examination of virus particles associated with the cells and biochemical assay for reverse transcriptase activity for detection of retrovirus.

RESULTS

Our results showed by karyotype analysis that McCoy cells are of mouse origin. Electron microscopic examination revealed the presence of endogenous retrovirus type-A and type-C virions. Biochemical assays of culture supernatant fluids from McCoy cells detected reverse transcriptase activity which required Mg(2+) ions.

CONCLUSIONS

The present study has confirmed that McCoy cells currently used by many laboratories are mouse cells, not the original McCoy cells derived from human cells. Laboratory workers should be aware of the presence of endogenous murine retrovirus in this cell line and appropriate precautions should be taken.

Interactions between HIV-1 and cytomegalovirus in human osteosarcoma cells carrying both viruses

Cytomegalovirus (CMV) and the human immunodeficiency virus type 1 (HIV-1) may interact in the pathogenesis of AIDS. We compared CMV replication in human osteosarcoma (HOS) cells to that in HOS cells genetically engineered to contain an envelope-deficient HIV-1 proviral construct (designated HOS-HXG). Following acute CMV infection of each cell line, HOS-HXG cells contained higher numbers of intranuclear CMV nucleocapsids than did HOS cells. Infectious CMV could be persistently detected in culture supernatant fluids of the CMV-infected HOS-HXG cells, whereas CMV was lost over several weeks from HOS cells infected with CMV in parallel. HIV-1 CMV pseudotypes were not detected in supernatant fluids from CMV-infected HOS-HXG cells. On day 119 after CMV infection, these cultures were superinfected with HIV-1. These dually infected HOS-HXG cells produced infectious HIV-1 and exhibited markedly enhanced CMV replication compared to parental CMV-infected HOS-HXG cells. Two different HIV-1 tat gene function antagonists, Ro24-7429 and chemically modified antibodies to the Tat protein, did not inhibit the replication of CMV in either acute or persistent infections of HOS-HXG cells at concentrations that inhibited HIV-1 replication.