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Biomedical subjects

V L Ng

Publications and source records attributed to V L Ng.

52 records · Page 3Linked to original sources
PubMed1989

Reliable confirmation of antibodies to human immunodeficiency virus type 1 (HIV-1) with an enzyme-linked immunoassay using recombinant antigens derived from the HIV-1 gag, pol, and env genes.

An enzyme-linked immunoassay (ELISA) using six recombinant proteins corresponding to large segments of the human immunodeficiency virus type 1 (HIV-1) gag, pol, and env gene products (HIVAGEN; SmithKline Bio-Science Laboratories, Van Nuys, Calif.) was developed to confirm the presence of antibodies to HIV-1 in sera reactive in the whole-cell-derived virion screening ELISAs. Serum samples for testing were obtained from healthy seronegative blood donors and from the different categories of HIV-infected individuals (asymptomatic, acquired immunodeficiency syndrome [AIDS]-related complex, and AIDS). A positive reaction was defined as reactivity against an env and at least one other (either gag or pol) HIV-1 gene product; negative was defined as no reaction with any antigen; and indeterminate was defined as reactivity with gag or pol (or both) or with env alone. None of the 1,180 serum samples from healthy seronegative blood donors gave a positive result, and only 49 of these samples (4%) gave indeterminate results. The recombinant HIV-1 antigen ELISA panel identified seropositive individuals with a high degree of accuracy, as a positive reaction was seen with 99.3% of asymptomatic healthy seropositive individuals, 98.1% of patients with AIDS-related complex, and 90.4% of patients with AIDS. None of the 725 HIV-1-seropositive subjects had a negative test result. Reactivity with the Kp41 antigen, corresponding to an amino-terminal portion of the gp41 envelope glycoprotein, by itself demonstrated 100% sensitivity and specificity in distinguishing seronegative from seropositive sera. A subset of seronegative and seropositive samples were tested both with the recombinant HIV-1 antigen ELISA panel and by Western blot (Du Pont Co.). The recombinant HIV-1 antigen ELISA panel accurately identified more seropositive and seronegative samples and had fewer indeterminate results than did Western blot (interpreted by Du Pont criteria).

AIDS-Related Complex↗
PubMed1989

Organization of microbiology laboratory services for the diagnosis of pulmonary infections in patients with human immunodeficiency virus infection.

When faced with the ever-increasing demand for the rapid laboratory diagnosis of Pneumocystis carinii pneumonia (PCP), as well as a variety of fungal, parasitic, and bacterial opportunistic infections in Human Immunodeficiency Virus (HIV)-infected individuals, the Chest Service and the Clinical Microbiology Laboratory at San Francisco General Hospital developed a coordinated plan for the collection and rapid examination of specimens to allow presumptive diagnoses to be made as quickly as possible. Clinical studies have been performed to determine the efficacy of different specimens and diagnostic systems for the provision of clinically useful information. Our approach has been to provide medical care on an outpatient basis using less invasive diagnostic systems that do not require direct physician participation. Direct laboratory examination of a single specimen submitted to microbiology often yielded presumptive or final diagnoses that were directly communicated to the physician. The evolution of PCP diagnosis in AIDS patients is described. Our current procedure of examining mucolysed, concentrated induced sputum stained with a rapid Giemsatype stain, Diff-Quik (Baxter/Scientific Products, McGaw, IL), has a sensitivity for P carinii detection of 74% to 77%. We have found that the use of commercially available immunofluorescence staining diminishes screening time and increases the sensitivity of P carinii detection in mucolysed concentrated induced sputum. We also describe the appearance of bacterial, fungal, and parasitic agents seen on direct examination and the usefulness of antigen detection, serology, and various microbiologic culture systems for diagnosing infections caused by these organisms.

Acquired Immunodeficiency Syndrome↗
PubMed1989

The use of mucolysed induced sputum for the identification of pulmonary pathogens associated with human immunodeficiency virus infection.

We describe a system for diagnosis of pulmonary disease in the human immunodeficiency virus-infected patient using induced sputum and other diagnostic procedures. This system has been successfully used at San Francisco (Calif) General Hospital for more than 2 years. It utilizes outpatient facilities and reduces the need for bronchoscopy. Sputum induced by inhalation of 3% saline mist, mucolysed, concentrated by centrifugation, and stained by a rapid modified Giemsa stain was the first diagnostic specimen examined in 404 episodes of suspected human immunodeficiency virus-associated pulmonary disease in 358 patients. Pneumocystis carinii was found in 222 (55%) sputum specimens. In 118 episodes in which the sputum did not contain P carinii, bronchoscopy with transbronchial biopsy and/or bronchoalveolar lavage was performed and P carinii was found in 50 (42%). These 118 bronchoscopy results, as well as evaluation of the subsequent clinical course of those patients who accounted for 64 episodes of lung disease and who did not have bronchoscopy following examination of nondiagnostic induced sputum, indicated a range of sensitivity for detection of P carinii in induced sputum of 74% to 77% and a negative predictive value of 58% to 64%. Mycobacteria were recovered from 11 (6%) of the induced sputum and 6 (12%) of the bronchoscopic specimens containing P carinii. However, only oral or environmental fungi were recovered from P carinii-containing induced sputum or bronchoscopic specimens. For those patients in whom P carinii was not detected, only the bronchoscopic specimens were cultured for Mycobacteria and fungi. Potentially pathogenic Mycobacteria and fungi were recovered from 16 (23.5%) and 34 (50%), respectively, of these P carinii-negative specimens. Analysis of these results, obtained under routine practice conditions, indicates that bronchoscopy should be reserved for those patients whose induced sputum examinations do not show P carinii and that mycobacterial and fungal cultures be performed only on bronchoscopic specimens in which P carinii is not detected.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Diagnosis of Pneumocystis carinii pneumonia: improved detection in sputum with use of monoclonal antibodies.

With the dramatic increase in the frequency of Pneumocystis carinii pneumonia associated with human immunodeficiency virus infection, there has been a need for more rapid and less invasive diagnostic techniques. Recent studies have shown that examination of induced sputum can establish the diagnosis of P. carinii pneumonia in about 55 percent of cases. To assess whether a recently developed indirect immunofluorescent stain using monoclonal antibodies was more sensitive than Giemsa or toluidine blue O stains in detecting P. carinii in sputum, we undertook two prospective studies. Of 63 patients at one institution from whom sputum specimens were obtained, 49 were ultimately given a diagnosis of P. carinii pneumonia, 46 of them by staining of sputum. The sensitivity of the three stains in detecting P. carinii was 45 of 49 (92 percent) for immunofluorescence; 37 of 49 (76 percent) for Diff-Quik (a Giemsa-type stain); and 39 of 49 (80 percent) for toluidine blue O. There were no false positive immunofluorescent stains. In a similar study of a series of 25 patients at another institution, a diagnosis of P. carinii pneumonia was made in 23 of 25 patients by staining of induced sputum. We conclude that examination of induced sputum is a rapid, sensitive, and inexpensive method for diagnosing P. carinii pneumonia and that indirect immunofluorescence is a practical and highly sensitive staining technique for establishing this diagnosis.

Animals↗
PubMed1988

High titer anti-HIV antibody reactivity associated with a paraprotein spike in a homosexual male with AIDS related complex.

We observed a human immunodeficiency virus (HIV)-infected homosexual male with AIDS related complex (ARC) who had a serum globulin level of 80 g/L. Serum protein electrophoresis revealed a gamma globulin fraction of 40 g/L, of which 50% (20 g/L) was contained within a paraprotein spike, comprised predominantly of IgG kappa. This patient also had high titer anti-HIV antibodies in his serum, which were Western blot reactive at a final dilution of 1:500,000, and recognized gp120env, p66pol, p55gag, p53pol, p41gag, and p24gag. Because paraproteins in the past have been shown to be directed against specific antigens, we purified this patient's paraprotein using a modified high performance liquid chromatography (HPLC)-hydroxylapatite procedure and tested the purified paraprotein for anti-HIV antibody activity. The purified paraprotein retained anti-HIV antibody activity to a final dilution of 1:100,000, and recognized p66pol, p55gag, p53pol, p41gag, and p24gag. The recognition of both "gag" and "pol" gene products suggested that the purified paraprotein might not be monoclonal in origin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that the purified paraprotein contained at least two immunoglobulin light chain species (Mol wt 30 to 33 Kd). Affinity chromatography of the purified paraprotein using a p24-Sepharose 4B matrix separated the "gag" and "pol" antibody activities. Immunoglobulin gene rearrangement analysis of a bone marrow aspirate (which contained 15% plasma cells) failed to reveal a clonal population of immunoglobulin producing cells. We conclude that this patient's paraprotein accounted for most of the anti-HIV activity present in whole serum, and that this paraprotein was not monoclonal in origin.

AIDS-Related Complex↗
PubMed1987

Successive bacteremias with "Campylobacter cinaedi" and "Campylobacter fennelliae" in a bisexual male.

A bisexual human immunodeficiency virus-seropositive male had successive bacteremias with "Campylobacter cinaedi" and "Campylobacter fennelliae." Because final identification of both isolates was not completed until 1 month after the last admission of the patient, a novel and nonstandardized antimicrobial susceptibility testing method was useful in guiding timely antimicrobial therapy.

AIDS-Related Complex↗
PubMed1983

Characterization of rabbit surfactant-associated proteins.

In the present study, the apolipoproteins associated with a purified surfactant fraction isolated from lung lavage of adult rabbits were characterized. Surfactant purity was assessed by the glycerophospholipid composition and by electron microscopic examination. The purified surfactant was delipidated and the apolipoproteins were analyzed by two-dimensional polyacrylamide gel electrophoresis. By use of this technique at least eight proteins or families of proteins were found to be associated with surfactant. Four of these apolipoproteins were families of proteins of 55-70, 29-36, 26-28 and 22-23 kilodaltons (kDa). All of these apolipoprotein families had acidic isoelectric points (pI less than or equal to 5.6), and were specifically bound to a Con A-Sepharose matrix, indicative that these apolipoprotein families are modified by oligosaccharide side-chains. The finding that neuraminidase treatment degraded the 29-36 kDa family is suggestive that this apolipoprotein family contains sialic acid residues. Three major proteins of 66, 43-45 and 35 kDa and a minor protein of 86 kDa were also observed. These proteins had isoelectric points in the more neutral range (pI 6.0-6.5). The 66 kDa protein (pI 6.4) had the same apparent molecular weight and isoelectric point as the major protein of delipidated rabbit serum and as purified rabbit albumin, which suggests that this protein is albumin. These findings are indicative that the apolipoproteins of surfactant are more numerous and complex than previously reported.

Animals↗
PubMed1983

Further studies on the glycosylated gag gene products of Rauscher murine leukemia virus: identification of an N-terminal 45,000-dalton cleavage product.

A glycosylated 45,000-Mr protein containing Rauscher murine leukemia virus p15 and p12 antigenic sites and tryptic peptides was identified in Rauscher murine leukemia virus-infected cells. This glycoprotein, termed gP45gag, was also shown to contain a single tryptic peptide also present in gPr80gag and its unglycosylated apoprotein precursor Pr75gag, but lacking in Pr65gag or Pr40gag. The presence of this peptide only in viral precursor proteins containing the so-called leader (L) sequence strongly suggests that gPr45gag is an N-terminal fragment of larger glycosylated gag polyproteins, composed of L sequences in addition to p15 and p12. The kinetics of appearance of radiolabeled gPr45gag and its disappearance during chase-incubation is suggestive of a precursor-like role for this intermediate gene product. An observed 27,000-Mr glycosylated polypeptide, termed gP27gag and containing p15 but not p12, p30, or p10 antigenic determinants, is a candidate cleavage product derived from gPr45gag. These observations suggest that gPr45gag and its putative cleavage product gP27gag represent an authentic pathway for intracellular processing of glycosylated core proteins.

Gene Products, gag↗
PubMed1980

Characterization of viral polyproteins in cells transformed and producing Moloney murine sarcoma virus-124.

The viral proteins of Moloney murine sarcoma virus-transformed mouse cells (G8-124), that overproduce the sarcoma virus relative to helper leukemia virus, were examined by immunoprecipitation, sizing by gel electrophoresis and peptide mapping. Using antisera to the viral core proteins, a p10-deficient core polyprotein of 63 000 daltons (P63gag) was detected which was found to be a product of the MuSV-124 genome. Helper virus proteins Pr67gag, gPr85gag, Pr200gag-pol, and gPr83env were also detected and characterized. An unusual helper virus precursor polyprotein of 93 000 daltons was also detected and characterized. It was labeled with [3H]fucose, suggesting that it was an intermediate precursor containing gp70 on which further modification of the core oligosaccharide had occurred relative to gPr83env. The usual viral proteins were also found in sarcoma virus particles and they were undistinguishable in size from those of Moloney murine leukemia virus (cl-1 strain). These experiments together with pulse-labeling experiments performed in the presence of the arginine analog canavanine, which prevents proteolytic cleavage, suggest that the product derived from the Mo-MuSV-specific sequences must be expressed as a separate gene product since we were unable to detect in transformed cells a polyprotein containing both viral (e.g., 'gag', 'pol' or 'env') and non-viral components. Cell-free protein synthesis studies performed with Mo-MuSV-124 genomic RNA have confirmed this interpretation and have identified three size classes of polypeptides as translation products of the sarcoma virus genome. They are P63gag, P42-P38 and P23. Intracellular p63gag and cell-free synthesized P63gag, appear to have identical sizes, antigenic determinants and tryptic peptides. The P42-P38 proteins contain core protein determinants. P23 is not related to the products of the replication genes of MuLV. Thus, P23 is a candidate for the 'src' gene product of Mo-MuSV-124.

Animals↗
PubMed1980

The structural relatedness of the virus core proteins of Rauscher and Moloney murine leukaemia virus.

The virus core proteins p30, p15, pp12 and p10 of Rauscher (R-MuLV) and Moloney murine leukaemia virus (Mo-MuLV) were purified. Two-dimensional peptide maps of 3H-leucine-containing tryptic peptides as well as elution profiles from ion-exchange chromatography of tryptic peptides derived from 3H-tyrosine-labelled R-MuLV core proteins and 14C-tyrosine-labelled Mo-MuLV core proteins were compared. The results show that the p30 and p10 proteins are very similar but that p15 and pp12 exhibit significant differences.

Animals↗
PubMed1979

Characterization of intracellular precursor polyproteins of Moloney murine leukemia virus.

Intracellular Moloney murine leukemia viral precursor polyproteins were compared with mature viral proteins by immunoprecipitation and tryptic peptide mapping experiments. The results were consistent with precursor roles for Pr65gag, Pr200gag-pol, Pr135pol, and gPr83env. The glycosylated gag gene product gPr85gag, although containing sequences characteristic of all four core proteins plus additional sequences not found in Pr65gag, lacked a major tyrosine-containing p30 tryptic peptide, suggesting that gPr85gag is not processed to p30.

Epitopes↗
PubMed1978

Inhibition of maturation of Rauscher leukemia virus by amino acid analogs.

Synthesis of primary precursor polyproteins of Rauscher leukemia virus (RLV) core and envelope proteins occurs in the presence of amino acid analogs canavanine and p-fluorophenylalanine, but cleavage of these precursors is severely inhibited or slowed down. After treatment with these agents, the release of characteristic virus or stable virus-like particles is greatly depressed.

Canavanine↗
PubMedDate not supplied

In vivo emergence of drug-resistant mutations at less than 50 HIV-1 RNA copies/mL that are maintained at viral rebound in longitudinal plasma samples from human immunodeficiency virus type-1-infected patients on highly active antiretroviral therapy.

OBJECTIVE: Emergence of human immunodeficiency virus type-1 (HIV-1) genotypic drug resistance is generally attributed to noncompliance, poorly absorbed drugs, or drug-to-drug interaction. Attempts to determine emerging genotypic drug resistance from study subjects on highly active antiretroviral therapy (HAART) relied on insensitive polymerase chain reaction (PCR) techniques, revealing wild type HIV-1 or precursor resistant genotypes from few plasma samples successfully amplified with <50 copies/mL. STUDY DESIGN/METHODS: In this analysis, using Applied Biosystems' ViroSeq HIV-1 Genotyping Systems, Version 2.0 (Applied Biosystems, Foster City, CA, USA) and the supplemental, for research use only, nested PCR primers, genotypic drug resistance was determined in longitudinal plasma samples from 11 study subjects on HAART. RESULTS: In 4 of 11 study subjects, newly emerging genotypic primary resistant mutations were detected in plasma samples with <50 copies/mL. Most of these primary drug-resistant mutations were detected in subsequent longitudinal samples with detectable viral load (viral breakthrough). CONCLUSIONS: This analysis suggests sufficient viral replication <50 copies/mL to generate genotypic drug resistance in study subjects on suppressive HAART.

Anti-HIV Agents↗