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Biomedical subjects

P C Frei

Publications and source records attributed to P C Frei.

At least 55 records · Page 3Linked to original sources
PubMed1991

Characterization of antibodies reacting with HIV gag proteins occasionally found in the serum of non-infected subjects.

The use of serological tests for the diagnosis of HIV infection has revealed that some non-infected persons have antibodies that react with HIV-1 gag proteins. Here, the sera of three non-infected subjects reacting with p17 and 11 non-infected subjects reacting with p24 were investigated, using an enzyme immunoassay (EIA) with six recombinant gag antigens and Western blot analysis of proteolytic peptides of two of these gag antigens. The results indicate that whereas all p17-reactive sera could react with an unique epitope, individual p24-reactive sera recognize different epitopes. Investigations by EIA also demonstrated the role of sequences located far from the epitopes in making these epitopes accessible to the antibodies or in providing them with an antigenic conformation. In addition to the 14 subjects mentioned above, another subject was shown to have antibodies reacting with the p9 (NC) gag protein. Several proteins are known as having homology with HIV-1 gag proteins. Their possible role in eliciting cross-reactive antibodies is discussed.

Blotting, Western↗
PubMed1990

Histopathologic features of hepatocellular carcinoma in Zaire.

The pathology of hepatocellular carcinoma (HCC) was studied based on 223 Zairian HCC cases registered from 1966 to 1985. The observations included the following: (1) hepatitis B surface antigen (HBsAg) status, (2) histologic types, (3) degree of cellular differentiation, and (4) frequency and types of the accompanying cirrhosis. Serum HBsAg was positive in 56.7% of HCC patients and 5.7% of controls (P less than 0.001). Immunohistochemical localization of HBsAg was positive in 53.3% in normal hepatocytes and in 10% in neoplastic cells. Morphologically, mixed type HCC (48.4%), trabecular (31.4%), and compact variants (13.5%) were predominant. Clear cell and pseudoglandular variants were rare (less than 1%). The majority of tumors (83%) were poorly differentiated HCC (Grades: 2-3, 3, 3-4, and 4). Well-differentiated HCC were extremely rare (0.5%). Fifty percent of HCC arose in a cirrhotic liver, predominantly of the macronodular (67.4%) inactive (55%) type. The micronodular cirrhosis was very uncommon (1.1%). These findings clearly show the excess of poorly differentiated HCC in African patients and suggest a possible link between the morphologic features of HCC in Africa and its extraordinary fast-running course.

Adolescent↗
PubMed1990

Modified dot assay with increased sensitivity: detection of small amounts of immunoglobulin molecules and the importance of different detection systems.

The original method of the dot assay described by Hawkes et al. enabled the detection of 100 pg of immunoglobulin molecules. We compared different enzyme detection systems based on the avidin-biotin complex, in conjunction with different substrates. Three commercial kits (Vectastain-ABC, Streptavidin Bridge, and Streptavidin-Peroxidase Complex) based on the same technique were also included in the comparison. In addition, we tested the Aureo-Probe kit, which is based on gold- and silver-enhanced staining. Various incubation times, blocking solutions (horse serum, bovine serum albumin, and milk), and commercial antihuman Ig antisera or monoclonal antibodies were tested. The greatest sensitivity was achieved by using the peroxidase-avidin-biotin complex together with 4-chloro-1-naphtol as substrate, which detected 1 pg of immunoglobulin molecules. Equal sensitivity was also shown by the Aureo-Probe system.

Avidin↗
PubMed1989

First documented case of human immunodeficiency virus type 2 infection in an asymptomatic Swiss subject.

Few cases of human immunodeficiency virus type 2 (HIV-2) infection have been reported in individuals other than of West African origin. The first well documented case of HIV-2 infection observed in a Swiss subject is presented here. The 50-year-old woman had a sexual relationship with a Senegalese man, who was later shown to be HIV seropositive. Initially, the subject's serum was tested using a routine screening assay for the detection of HIV-1 antibodies. This assay elicited a borderline positive result. A confirmatory competitive EIA and a Western blot test for anti-HIV-1 antibodies showed a positive reaction with gag and pol proteins of HIV-1, but not with env proteins. Thus, HIV-2 infection was suspected and subsequently confirmed by three different methods, including Western blot analysis and an HIV-1/HIV-2 differentiation test. This case emphasizes the need for screening with combined HIV-1/HIV-2 tests.

Blotting, Western↗
PubMed1989

Serological diagnosis of HIV infection: incidence, outcome and significance of partial reactions found in western blot analysis.

Between May 1986 and April 1987 routine screening for anti-HIV antibody was performed by enzyme immunoassay (EIA) on 3344 serum samples. The 1160 samples found positive or borderline were further analysed in Western blot (Wb). We analysed the frequency of different patterns of 'intermediate' Wb reactions (1-3 'specific' bands) and tried to determine their significance by searching for possible modifications of the pattern of reaction a few months later. Of 1160 Wb, 461 were clearly positive, 489 negative and 210 'intermediate'. The latter consisted of: 92 sera with anti-p24 (associated or not), 23 with anti-gp 120 and 160, 16 with anti-p55, 12 with anti-p41, 10 with anti-p65, eight with anti-p17 and four with anti-p31. A non-specific pattern was observed in the remaining 45. Of these sera, 46% were obtained from high risk subjects, 38% from persons without risk and in 16% no reliable information was available. In 30 subjects (24 with p24 and 6 with p41), a second sample was obtained about three months later. The reaction persisted in nine, was replaced by another in five, and disappeared in 15. One subject with anti-p41 in the first sample became clearly positive. In one of the 15 samples with disappearance of the reaction, the antigen p24 was present as the only sign of HIV infection. Later samples of this subject showed clear seroconversion. In many subjects with and without risk of exposure to HIV, the Wb gives an intermediate pattern of reactions (1-3 specific bands), that does not permit definitive conclusion on one single sample. Later controls are therefore necessary. Most of these reactions do not correspond to HIV infection.

AIDS Serodiagnosis↗
PubMed1989

Additives contained in drug formulations most frequently prescribed in Switzerland.

The presence of substances known to induce pseudoallergic reactions was investigated by means of a questionnaire to the manufacturers of 1,467 frequently administered formulations. Benzoates were found in 15% of the formulations, sorbates in 5.5%, sulfites in 3.8%, and benzalkonium in 3.0%. The occurrence of the seven artificial colours studied was as follows: indigotin 7.8, erythrosine 7.4, sunset yellow 6.6, tartrazine 4.9, quinoline yellow 2.8%, ponceau (new coccine) 2.6, and amaranth 1.7%. A significant risk of exposure to preservatives and dyes likely to induce asthma, urticaria, or other pseudoallergic reactions exists for all individuals taking commercial drug products.

Benzoates↗
PubMed1988

Multidisc RAST: a reliable method for screening of specific IgE antibodies in serum?

"Multidiscs" (md) are cellulose discs to which several allergens are coupled, allowing the simultaneous screening of several specific IgE antibodies. We compared RAST performed with md to RAST performed with the corresponding individual allergens coated on single discs (sd). One hundred and twenty-two RAST positive samples were analyzed for four different allergen groups: moulds, cereals, weed pollens and tree pollens. We found lower RAST sensitivity when screening with mds than with the individual sds in all allergen groups except cereals. In 30 to 70% of the samples, the results were concordant. In 25.5 to 66.7%, md values were lower and in 1.3 to 26.3% higher than sd values. When only qualitative results were considered, the loss of sensitivity appeared acceptable: only 6.7 to 16.7% of the sd positive samples were not detected by md screening. A cost-benefit analysis, calculated on local data, confirmed economic advantages.

Cost-Benefit Analysis↗
PubMed1988

Identification of monoclonal gammopathies: a comparison of immunofixation, immunoelectrophoresis and measurements of kappa- and lambda-immunoglobulin levels.

We study whether immunoelectrophoresis (IE) could be replaced by immunofixation (IF) for the routine diagnosis of monoclonal gammopathies and/or by a quantitative measurement of kappa-resp. lambda-Ig levels in serum. The values of these measurements, together with the level of each Ig class, were used to calculate two ratios. IF, IE and calculation of both ratios were simultaneously applied to 153 serum samples. A monoclonal gammopathy (MGP) was found with all three methods in 51 cases and by none of them in another 51 cases. The first two techniques were positive and the third one negative in 16 cases. In 15 cases, IF showed the presence of a MGP, which was not or incompletely identified with IE, these results being associated with normal (7x) or abnormal ratios (8x). Nineteen cases with normal IF and IE had one or two abnormal ratios. After comparison with clinical data and outcome, we conclude that IF revealed 15 cases of MGP, which were not or only partially shown by IE. IE did not show any case of MGP not detected by IF. One of the ratios appeared as an interesting adjunct to the diagnostic procedure, but insufficient to be used as a single test. The other appeared to be of no diagnostic help. We conclude that immunofixation is the test of choice in the routine diagnosis of monoclonal gammopathies.

Diagnostic Errors↗
PubMed1987

[The hepatitis B vaccination campaign carried out from 1982 to 1984 using the Hevac B Pasteur vaccine among 6162 employees of Vaud hospitals].

6162 Swiss hospital employees were vaccinated against hepatitis B from 1982-1984 with Hevac B Pasteur vaccine. Vaccination was offered free of charge to 8471 employees, 72% of whom accepted a series of three injections and 50% a booster about 15 months later. Side effects, all benign, brief and rapidly resolved, were observed after 4% of injections in 7% of patients. Side effects after each of the three injections were noted in 0.7% of subjects. These figures are below those of other authors. -Concentrations of protective anti-HBs antibodies produced by the vaccination were measured by sampling of subjects. Four years after the beginning of the vaccinations the subjects had an average concentration of 87 mU/ml without booster and 595 mU/ml with booster. On average these concentrations are higher in employees more heavily exposed to hepatitis B than in the others. They are also higher in vaccines than in subjects immunized after natural infection, in whom they were 138 mU/ml. Production of anti-HBs antibodies was observed in 94% of subjects vaccinated.-In conclusion, the preparation used proved effective and well tolerated. This observation should help to foster more general use of vaccination campaigns in exposed populations.

Hepatitis B↗
PubMed1987

[Retrospective (1970-1984) serological study of delta antigen and antibody. Observations on seroconversion and absence of delta in non-A, non-B hepatitis].

335 serum samples collected between 1970 and 1984 from 278 HBsAg positive patients were tested for HDV antigen and HDV antibody (HDV = hepatitis D virus; also referred to as delta virus). The first positive sample was obtained in February 1974. The prevalence of the delta coinfection fluctuated in the following years between 0 and 52% of HBV-infected subjects. It was 40% on average in subjects at risk for HBV infection (i.v. drug abusers, homosexuals and institutionalized mentally retarded subjects) and 6% in persons without risk factors. The antibody was also found in 22% of subjects in a group of drug abusers who recovered from HBV infection (positive for anti-HBs antibody). The study showed that dissemination of HDV infection in Switzerland after 1974 was small clusters occurring mainly in drug users. It also showed that the infection was principally associated with chronic active hepatitis. In addition, sequential serum samples were taken from five patients with chronic hepatitis B superinfected by HDV, over periods of 2 to 13 months. Seroconversion (HDV antigen to HDV antibody) was observed in 4 of these 5 patients, with simultaneous presence of antigen and antibody for periods of 2 to 6 weeks. 167 samples from patients with non-A, non-B hepatitis were all negative for anti-delta antibody.

Adolescent↗
PubMed1987

Screening for anti-HTLV-III/LAV antibody in high-risk subjects: sensitivity and specificity of commercial tests.

1,834 serum samples from high-risk subjects were tested for anti-HTLV-III/LAV antibody by using the enzyme immuno assay (EIA) of Abbott (A), or the EIA of Abbott and Pasteur (P), or those two EIA plus Western blot analysis (WB). 983 samples were negative in A, 766 were strongly positive when tested in duplicate with both A and P, and 85 were slightly positive in A (23 samples) or discordant (62 samples) when tested further in P and WB. Of 62 discordant samples, 38 were reproducible. The pattern A+P-WB- was by far the most frequently encountered (26 samples) and interpreted as reflecting the higher incidence of positive results in the assay A. If one assumes that WB results are correct, the specificities of A and P are 93 and 100%, respectively (p less than 0.01), whereas the sensitivities are similar (98 and 99%).

Acquired Immunodeficiency Syndrome↗