Murine gammaretrovirus group G3 was not found in Swedish patients with myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia.

Background: The recent report of gammaretroviruses of probable murine origin in humans, called xenotropic murine retrovirus related virus (XMRV) and human murine leukemia virus related virus (HMRV), necessitated a bioinformatic search for this virus in genomes of the mouse and other vertebrates, and by PCR in humans.

Results: Three major groups of murine endogenous gammaretroviruses were identified. The third group encompassed both exogenous and endogenous Murine Leukemia Viruses (MLVs), and most XMRV/HMRV sequences reported from patients suffering from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

Development of phenotypic HIV-1 drug resistance after exposure to single-dose nevirapine.

Objectives: Single-dose nevirapine (sdNVP) used to prevent mother-to-child transmission of HIV-1 results in the selection of genotypic drug resistance mutations. To assess the levels of phenotypic resistance conferred by these mutations, we examined the ability of sample-derived HIV-1 reverse transcriptase to function in the presence of nevirapine (NVP).

Methods: Plasma samples from HIV-1 pregnant women before and after exposure to sdNVP were used to extract viral reverse transcriptase for the Cavidi ExaVir Drug susceptibility assay.

Improved HIV-1 viral load determination based on reverse transcriptase activity recovered from human plasma.

A more sensitive version of ExaVir Load, a test that utilizes reverse transcriptase (RT) activity from virions in plasma to determine HIV-1 viral load, is described. The virions were immobilized on a gel that was washed, followed by lysis of the virions, elution of purified RT, and finally RT activity determination. The changes made to the original test were: (1) improved washing of the immobilized virions by addition of a non-lytic detergent to the wash buffer, (2) improved virion lysis procedure, including changes in salt, detergent and pH, (3) the use of larger sample volumes in the RT assay, and (4) prolonged RT reaction time.

HIV-1 viral load determination based on reverse transcriptase activity recovered from human plasma.

We describe a procedure (ExaVir Load) to carry out human immunodeficiency virus-1 (HIV-1) viral load testing using reverse transcriptase (RT) recovered from HIV-1 virions in plasma. Samples from individuals infected with HIV-1 were treated with a sulphydryl-reactive agent to inactivate endogenous polymerases. Virions were then immobilised on a gel and washed in individual mini columns to remove RT-inhibiting antibodies, antiviral drugs, and other RT inhibitors.

[Inhibition of duck hepatitis B virus DNA replication by antisense phosphorothioate oligodeoxynucleotides in vitro and in vivo].

Background: To determine the feasibility of inhibition of duck hepatitis B virus (DHBV) DNA replication by antisense phosphorothioate oligodeoxynucleotides corresponding to DHBV transcription region.

Methods: The authors designed three antisense phosphorothioate oligodeoxynucleotides which correspond to DHBV PreS1,PreS2 and S antigen gene promotors respectively. The DNA replication level was detected with Southern blot method and cpm calculation.

Use of HIV-1 reverse transcriptase recovered from human plasma for phenotypic drug susceptibility testing.

Objective: To demonstrate the use of HIV-1 reverse transcriptase (RT) recovered directly from plasma for phenotypic drug susceptibility testing.

Methods: Plasma from HIV-1 infected individuals with and without drug resistance-associated mutations were selected for the study. The blind coded plasmas were treated to inactivate cellular enzymes.

Application of a colorimetric chain-termination assay for characterization of reverse transcriptase from 3'-azido-2',3'-deoxythymidine-resistant HIV isolates.

Two different enzyme assays, both based on the interaction of native reverse transcriptase (RT) and 3'-azido-2',3'-deoxythymidine triphosphate (AZT-TP), were used to characterize the enzymes from 18 HIV-1 isolates with decreased sensitivity to AZT in cell culture. The first assay, which measures the balance between incorporation and excision of AZT monophosphate in the presence of dNTP substrate (in terms of IC(50)), gave an approx. 9-fold variation in sensitivity to AZT-TP.