Ribonuclease-resistant RNA controls (Armored RNA) for reverse transcription-PCR, branched DNA, and genotyping assays for hepatitis C virus.

BACKGROUND: Comparison and evaluation of molecular diagnostic assays for the detection and quantification of hepatitis C virus (HCV) RNA have been limited by the lack of RNA controls and calibrators. Armored RNA technology is a means for producing RNA that is completely protected from plasma ribonucleases. This method produces recombinant pseudoviral particles that are noninfectious and contain predefined RNA sequences. METHODS: A consensus 412-base sequence from the 5'NCR/Core region of HCV subtype 2b was derived from 34 individually sequenced HCV genotype 2b variants. A DNA fragment encoding the consensus HCV-2b sequence was synthesized de novo, cloned, and expressed as an Armored RNA control. The resulting HCV-2b Armored RNA (AR-HCV-2b) contained the complete HCV-2b consensus RNA sequence encapsidated within a protective protein coat. RESULTS: AR-HCV-2b was fully recoverable from human plasma incubated at 4 degrees C for >300 days. The particles were tested in three clinical assay formats: Amplicor HCV Monitor 1.0, Quantiplex HCV RNA 2.0, and INNO-LiPA HCV II. When added into seronegative, nonviremic plasma, AR-HCV-2b showed reproducible signals and linear dilutions in both the Amplicor and Quantiplex assays. AR-HCV-2b was correctly identified as subtype 2b in the INNO-LiPA line probe assay. CONCLUSION: The HCV-2b Armored RNA control is a versatile, durable, ribonuclease-resistant viral RNA control that is compatible in three different clinical assay formats.

Armored RNA technology for production of ribonuclease-resistant viral RNA controls and standards.

The widespread use of sensitive assays for the detection of viral and cellular RNA sequences has created a need for stable, well-characterized controls and standards. We describe the development of a versatile, novel system for creating RNase-resistant RNA. "Armored RNA" is a complex of MS2 bacteriophage coat protein and RNA produced in Escherichia coli by the induction of an expression plasmid that encodes the coat protein and an RNA standard sequence. The RNA sequences are completely protected from RNase digestion within the bacteriophage-like complexes. As a prototype, a 172-base consensus sequence from a portion of the human immunodeficiency virus type 1 (HIV-1) gag gene was synthesized and cloned into the packaging vector used to produce the bacteriophage-like particles. After production and purification, the resulting HIV-1 Armored RNA particles were shown to be resistant to degradation in human plasma and produced reproducible results in the Amplicor HIV-1 Monitor assay for 180 days when stored at -20 degreesC or for 60 days at 4 degreesC. Additionally, Armored RNA preparations are homogeneous and noninfectious.

Quantitation of hepatitis C viral RNA in sera of hemodialysis patients: gender-related differences in viral load.

Hepatitis C virus (HCV) infection is common in hemodialysis patients, as determined by antibody assays and qualitative polymerase chain reaction (PCR) analysis of serum HCV RNA. To further characterize HCV infection in this population, we measured the viral load in infected hemodialysis patients by a quantitative, competitive PCR assay (QC-PCR) for HCV RNA. Hepatitis C virus RNA levels were correlated with serologic, biochemical, and demographic features of a cohort of hemodialysis patients. Sera from 208 hemodialysis patients were screened for HCV RNA (5' conserved region) by reverse transcriptase PCR (RT-PCR) and HCV-specific antibody. Forty-four patients were antibody positive (21%); among these patients, 34 (77%) were HCV RNA positive. No viremic, seronegative patients were identified. Hepatitis C virus RNA levels quantitated by QC-PCR ranged from 3 x 10(5) to 10(8) molecules of HCV RNA/mL. Male patients had significantly higher mean and median HCV RNA levels (10(7) molecules/mL) compared with female patients (3.6 x 10(6) molecules/mL and 3 x 10(6) molecules/mL, respectfully; P = 0.02). No other demographic or clinical feature of this cohort correlated with HCV RNA levels. Intravenous drug abuse was the most frequently identified risk factor (29% of seropositive patients) for infection with HCV in this population. No association between HCV RNA levels and hepatic enzyme levels (alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, alkaline phosphatase) was apparent. Hepatitis C virus infection is highly prevalent in our hemodialysis population, and hemodialysis patients, particularly males, have high levels of HCV in serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic maxillary sinusitis associated with the mushroom Schizophyllum commune in a patient with AIDS.

Invasive infection with fungi of the Basidiomycota (rusts, smuts, toadstools, mushrooms, and puffballs) is extremely rare. We report such an infection in a patient with human immunodeficiency virus disease who presented with chronic maxillary sinusitis associated with the mushroom Schizophyllum commune. The organism was isolated from the surgical drainage material, and septate hyphae were seen invading the maxillary submucosa. The limited literature on this subject is reviewed.

A sequential, solid-phase assay for biotin in physiologic fluids that correlates with expected biotin status.

Interest in accurate measurement of biotin concentrations in plasma and urine has been stimulated by recent advances in the understanding of biotin-responsive inborn errors of metabolism and by several reports describing acquired biotin deficiency during parenteral alimentation. This paper presents a biotin assay utilizing radiolabeled avidin in a sequential, solid-phase method; the assay has increased sensitivity compared to previous methods (greater than or equal to 10 fmol/tube), correlates with expected trends in biotin concentrations in blood and urine in a rat model of biotin deficiency, and can utilize commercially available radiolabeled avidin.

Use of human antibodies to identify antigens in cultured human tumor cells: detection of discrete antigen molecules using electroblotting and enzyme-linked antibody probes.

To demonstrate antigens in cultured human tumor cells recognized by antibodies in human sera, extracts of cultured malignant melanoma cells were separated by SDS-PAGE, and electrophoretically transferred to nitrocellulose paper (NCP). The resulting electroblots were incubated with human serum, and bound immunoglobulin (Ig) was visualized with rabbit antibodies specific for human IgG, IgA or IgM, followed by peroxidase-conjugated goat anti-rabbit IgG. Antigen-antibody reactions in the nitrocellulose paper were also detected using 125I-labeled anti-rabbit IgG. As little as 125 pg of bound antibody per band were detectable. The numbers of proteins recognized by antibodies in human sera depended both on the quantity of protein transferred and the concentration of Ig applied to the NCP. Whole serum could not be used at dilutions less than or equal to 1:20 without an unacceptable increase in background staining. Binding of Ig to tumor cell proteins transferred to NCP depended on interactions with the Fab', not the Fc region of the Ig molecule. To determine the efficiency of transfer as a function of both time and molecular weight, tumor cell proteins were intrinsically labeled with 75Se-labeled methionine and transferred for up to 4 h after fractionation in gels containing acrylamide concentrations of 5%, 7.5%, 10% or 12%. Proteins less than 150 kDa were transferred with particularly high efficiency in greater than or equal to 2 h. Different antigens were recognized by the IgA, the IgG and the IgM molecules from the same sera. The methods outlined herein are proving to be useful in monitoring the purification of specific antigens from whole tumor cell extracts.

Correlation of immune complexes in disseminated neuroblastoma with serum antibody to bovine serum albumin.

To evaluate the relationship between tumor burden and circulating immune complexes (IC) in children with neuroblastoma (NBL), we studied sera collected at intervals from patients with disseminated (Stage III or IV) NBL. Sera from 10 of 12 patients contained IC by the Raji cell assay at some time during the first 9 to 11 months of the study. Higher IC levels were observed in sera of female patients. Fluid-phase C1q binding tests detected IC in only 16% of sera. IC measurements by either assay did not correlate with tumor burden. However, serum IC levels, as measured by the Raji cell assay, correlated significantly with serum antibody to bovine serum albumin (BSA) (rs = 0.54; p less than 0.001, rs = r as determined by Spearman rank correlation test). Measurement of anti-BSA antibodies in sera from the 12 patients, tested serially for circulating IC, and from five additional patients revealed that these had significantly higher anti-BSA activity than was found in sera from 13 age-matched controls. Sera from females also had relatively high levels of anti-BSA. Levels of antibody to bovine gamma-globulin and casein were not abnormal. Three sera with high IC levels (greater than 800 micrograms equivalents of heat-aggregated IgG) and relatively low anti-BSA activity appeared to contain "hidden" antibodies to BSA. These were demonstrated by measuring the increase in the ability of sera to bind 125I-BSA after they had been briefly acidified and then neutralized in the presence of the labeled BSA. The possible relevance of these results to the pathophysiology of NBL is discussed in light of earlier work that reported that serum IC levels correlate with the stage of the disease in NBL.

Synthesis of antigens, cross-reactive with bovine serum albumin, by cultured neuroblastoma cells.

Antisera to bovine serum albumin (BSA) react with biosynthetic products of the LAN-1 neuroblastoma cell line. This immunological reaction was shown by analysis of immunoprecipitates prepared with anti-BSA and products of this cell line intrinsically labeled by the incorporation of 3H- or 35S-labeled amino acids. Moreover, antibodies in sera from two patients with neuroblastoma precipitate intrinsically labeled macromolecules produced by these tumor cells. Release of antigens cross-reactive with BSA by neuroblastomas may explain, in part, the high levels of antibody to BSA and circulating immune complexes containing hidden or "blocked" antibodies to BSA found in some patients with this tumor.