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). Two sensitive real-time PCRs for this group were developed. The predicted and observed amplification range for these and three published XMRV/HMRV PCRs demonstrated conspicuous differences between some of them, partly explainable by a recombinatorial origin of XMRV. Three reverse transcription real-time PCRs (RTQPCRs), directed against conserved and not overlapping stretches of env, gag and integrase (INT) sequences of XMRV/HMRV were used on human samples. White blood cells from 78 patients suffering from ME/CFS, of which 30 patients also fulfilled the diagnostic criteria for fibromyalgia (ME/CFS/FM) and in 7 patients with fibromyalgia (FM) only, all from the Gothenburg area of Sweden. As controls we analyzed 168 sera from Uppsala blood donors. We controlled for presence and amplifiability of nucleic acid and for mouse DNA contamination. To score as positive, a sample had to react with several of the XMRV/HMRV PCRs. None of the samples gave PCR reactions which fulfilled the positivity criteria. CONCLUSIONS: XMRV/HMRV like proviruses occur in the third murine gammaretrovirus group, characterized here. PCRs developed by us, and others, approximately cover this group, except for the INT RTQPCR, which is rather strictly XMRV specific. Using such PCRs, XMRV/HMRV could not be detected in PBMC and plasma samples from Swedish patients suffering from ME/CFS/FM, and in sera from Swedish blood donors.

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. The fold increases in phenotypic resistance for each sample were compared with the genotypic profiles determined by population-based sequencing. RESULTS: None of the women sampled before sdNVP exposure had phenotypic resistance (median fold increase 0.7). Seven weeks after sdNVP, there was a 16-fold increase in phenotypic resistance among women who had NVP resistance mutations compared with only a 1.9-fold increase among NVP-exposed women with wild-type virus. Phenotypic resistance decayed with time coincident with the fading of genotypic mutations, and by 18 months, all samples were phenotypically susceptible. CONCLUSIONS: Exposure of pregnant women to sdNVP was associated with the transient appearance of viral populations that displayed phenotypic resistance to NVP. Overall, there was good concordance between phenotypic resistance to NVP, as measured with this enzymatic assay, and the presence of NVP genotypic mutations.

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. The alterations gave a tenfold increased sensitivity compared to the original version. The correlation between RT load by the current test and RNA PCR was the same as previously (r=0.90). Using colorimetric product detection, the average detection limit in a panel of 262 patient plasma from Stockholm was 0.5 fg RT/ml, corresponding to approximately 170 RNA copies/ml. None of 54 HIV-1 RNA negative samples exhibited RT. The amount of RT load positive samples were 19% for samples containing 50-400 RNA, 71% for samples with 400-1,500, and 100% among samples with >8,000 copies/ml (according to Roche Amplicor). The sensitivity could be increased further using fluorimetric detection. In conclusion, the modifications of the test described result in an important increase in sensitivity. It can now be regarded as a competitive alternative method for HIV viral load determinations.

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. Immobilised virions were lysed finally, and the viral RT eluted. The amount of RT recovered was quantified by a sensitive RT activity assay using either colorimetry or fluorimetry to detect DNA produced by RT. The "RT load" values of 390 samples from 302 HIV-1 patients living in Sweden were compared to results obtained with an HIV-1 RNA viral load assay. The correlation between the two tests was r = 0.90, P < 0.0001. Four of 202 samples from healthy blood donors gave low positive values in the RT test. All samples in a panel with 10 HIV-1 subtypes were positive by the RT load. The RT load test provides a technically less demanding and cost-effective alternative to methods based on nucleic acid amplification. Being insensitive to genetic drift occurring in HIV, the assay should be of particular use in resource-limited settings, where different subtypes and recombinant HIV strains occur.

[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. RESULTS: Primary duck hepatocyte culture was treated with 1.5 micromol/L antisense oligodeoxynucleotides in vitro, all the antisense fragments caused a firm inhibition of viral DNA replication and the inhibition rates were 61.5%, 69.3% and 62.4%, respectively. In vivo, the animals were treated with 10 microgram/g PreS1 antigen gene promotor antisense oligodeoxynucleotides per day for 6 days and a very strong inhibition rate of 87.9% was obtained. CONCLUSIONS: The results demonstrated the potential clinical application of antisense phosphorothioate oligodeoxynucleotides in clinics.

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. The virions were immobilized on a gel and washed to remove antiretroviral drugs and RT activity blocking antibodies. The immobilized virions were lysed; the viral RT eluted and quantified, all according to the ExaVir Load procedure. The drug sensitivity profiles of each RT were determined using serially diluted drugs and modified Cavidi HS Lenti RT kits. RESULTS: The phenotypic drug sensitivity profiles of the RT and the patterns of drug resistance mutations were highly concordant. Plasma RT from virions devoid of mutations associated with drug resistance had average 50% inhibitory concentrations (IC(50)) of 1.5 +/- 0.93 microM for nevirapine, 0.21 +/- 0.099 microM for efavirenz, 7.1 +/- 3.2 microM for delavirdine, 0.42 +/- 0.15 microM for azidothymidine triphosphate and 0.059 +/- 0.018 microM for didehydrothymidine triphosphate. The increase in IC(50) value for RT with drug resistance associated substitutions was from 3- to more than 65-fold for non-nucleoside inhibitors and between 2- and 30-fold for thymidine analogue drugs. CONCLUSION: RT derived from virions recovered from the plasma of HIV infected individuals can be used for analysis of phenotypic drug susceptibility. The methods presented provide rapid alternatives for analysing phenotypic drug susceptibility especially when the therapy is based on non-nucleoside RT inhibitors and thymidine-analogue drugs.

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. There was a correlation between the IC(50) values and the sensitivity of the corresponding virus to AZT in cell culture (r=0.60, P<0.01). The second assay, which was designed specifically for measurement of chain termination in the absence of dNTP substrate (as the concentration of AZT-TP giving 50% residual primer function, or CT(50)), revealed a more than 600-fold difference between the different isolate RTs. For the majority of enzymes there was a strict correlation between the results from the two assays; however, four isolates exhibited significantly higher CT(50)/IC(50) ratios than the other isolates. These differences were not related to sensitivity of the corresponding viruses to AZT but to the occurrence of certain mutations in their pol gene. The four deviating isolates contained either a minimum of four AZT-specific substitutions, including Thr-215-->Tyr (isolates 134 and 143), or some of the known specific substitutions combined with Thr-39-->Ala (isolates 80 and 157). The Thr-39-->Ala substitution has previously been recorded in connection with AZT/Foscarnet combination therapy.