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PubMed1991

Evaluation of three commercial enzyme immunoassays for toxoplasma and cytomegalovirus antibodies.

Three commercially available enzyme immunoassays (EIAs) were evaluated for specificity and sensitivity compared to immunofluorescent assays (IFAs) for detection of IgG and IgM antibodies to Toxoplasma gondii (Toxo) and Cytomegalovirus (CMV). A panel of 78 sera were tested, including specimens known to contain Toxo IgG or IgM, CMV IgM or IgM, antinuclear antibodies (ANA), antimitochondrial antibodies (AMA), and rheumatoid factor (RF). Linear correlation analysis comparing EIA and IFA results showed that the statistical relationship between the two assay methods was relatively weak (correlation coefficients ranging from 0.33 to 0.86). Qualitative correlation showed that the EIA methods agreed with IFA results in most cases. One manufacturer's products (Diamedix Corp.) gave consistently better sensitivity, specificity, and intra-assay reproducibility values than the other two systems (Clinical Sciences, Inc., and Whittaker Bioproducts). ANA, AMA, and RF did not appear to interfere with any EIAs.

Animals↗
PubMed1997

Congenital syphilis: detection of Treponema pallidum in stillborns.

Paraffin-embedded tissue from all 17 autopsies performed following 56 stillbirths associated with maternal syphilis during a 3-year period (1987-1989) was reexamined to compare immunofluorescent antigen (IFA) testing with silver staining for the detection of Treponema pallidum. Congenital syphilis (CS) originally was diagnosed in 9 of the 17 cases of stillbirth, on the basis of positive silver stains (7 cases) or morphological findings alone (2). Upon review, silver staining revealed T. pallidum in 10 of 17 cases and IFA testing revealed the pathogen in 15 of 17 cases, enabling diagnosis of CS in 16 of 17 cases of stillbirth associated with a reactive maternal rapid plasma reagin (RPR) card test. Most stillbirths associated with a reactive maternal RPR test during this time period involved CS, and IFA testing for T. pallidum is superior to silver staining for the identification of treponemes.

Adolescent↗
PubMed1980

Serologic diagnosis of acute lymphadenopathic toxoplasmosis.

The diagnosis of acute toxoplasmosis usually depends on serology, yet little data are available to compare the relative usefulness of various serologic tests after the onset of illness. The Sabin-Feldman dye test (DT), the IgM immunofluorescent antibody (IgM-IFA) test, the soluble antigen complement-fixation (CF) test, and the indirect hemagglutination (IHA) test were performed on serial serum specimens from 27 previously healthy patients, each of whom could identify the date of onset of illness within two weeks. IgM-IFA titers of greater than or equal to 1:160 were the best indicators of infection acquired in the past two to four months. The DT was useful for screening, but two-tube rises in titer were rarely documented, and absolute titers were imprecise indicators of the recentness of infection. Although two-tube rises in titer in CF and IHA tests could be seen in the majority of patients, the rises were so slow that both tests were less useful than the IgM-IFA test in documenting the diagnosis of acute toxoplasmosis.

Acute Disease↗
PubMed1987

Antibody response to human immunodeficiency virus after primary infection.

The antibody response to human immunodeficiency virus (HIV) after primary infection was monitored in eight homosexual men with the acute mononucleosis-like illness associated with seroconversion. Multiple sera from each subject, taken at frequent intervals after onset of acute illness, were tested for antibody to HIV by IgM and IgG immunofluorescent assays (IFAs), four commercial enzyme-linked immunosorbent assays (ELISAs), and Western immunoblot (WB). Antibody to HIV was detected first by IgM IFA (mean +/- SD, 5 +/- 3 days), followed by IgG IFA (11 +/- 3 days); the IgM antibody titer peaked at 24 +/- 17 days and disappeared by 81 +/- 27 days, whereas the IgG antibody titer peaked at 133 +/- 63 days and has not disappeared in any subject. Antibody to HIV was first detected by ELISA from 31 +/- 14 to 58 +/- 32 days, depending on the assay kit used. Antibody to p24 and gp41 was first detected by WB at 24 +/- 10 days, followed by antibody to p55 (40 +/- 20 days), p68 (57 +/- 19 days), and p34 (71 +/- 22 days).

Acquired Immunodeficiency Syndrome↗
PubMed1987

Cross-reactivity in serological tests for Lyme disease and other spirochetal infections.

Serum specimens from 163 persons with Lyme disease, tick-borne or louse-borne relapsing fever, yaws, syphilis, leptospirosis, or Rocky Mountain spotted fever were analyzed to assess the specificity of indirect fluorescent antibody (IFA) tests, an enzyme-linked immunosorbent assay (ELISA), and microscopic agglutination (MA) procedures. Strong cross-reactivity occurred when sera from individuals with Lyme disease, tick-borne relapsing fever, and louse-borne relapsing fever were tested against heterologous Borrelia antigens. Antibodies to Borrelia burgdorferi bound to Treponema pallidum in immunofluorescence tests for syphilis. Sera from subjects with syphilis cross-reacted in IFA tests and the ELISA for Lyme disease. Immunoglobulin antibodies to Borrelia or Treponema spirochetes, however, did not react with serovars of Leptospira interrogans in MA or IFA tests, and the prevalence of false-positive results in the reciprocal analyses was negligible.

Antibodies, Bacterial↗
PubMed1992

Clinical evaluation of an EIA for the sensitive and specific detection of serum antibody to Trypanosoma cruzi (Chagas' disease).

A commercial EIA for the detection of antibody to Trypanosoma cruzi was clinically evaluated. The primary use of this test is in the diagnosis and screening of donated blood in Latin America. When compared with sera positive by xenodiagnosis, the assay had a clinical sensitivity of 100%. When tested against matched hemagglutination (HA) and immunofluorescence (IFA) results (i.e., when both tests gave negative results) the EIA had a specificity of 99.03% (305/308). The cross-reactivity of this test was determined using sera from malaria and leishmaniasis patients (obtained from Africa, ensuring that the sera did not contain Chagasic antibodies) and from schistosomiasis, toxoplasmosis, tuberculosis, syphilis, and systemic lupus erythematosus samples. The EIA was 100% specific whereas IFA or commercially available HA kits from Latin America cross-reacted with several of the samples. In this investigation, the EIA appeared to be at least as sensitive and more specific than IFA or HA in the serodiagnosis of Chagas' disease.

Animals↗
PubMed1994

Diagnosis of babesiosis: evaluation of a serologic test for the detection of Babesia microti antibody.

To assess the possibility of standardization of a commonly used indirect immunofluorescent antibody (IFA) test for detection of Babesia microti antibody in human sera, the results from four reference laboratories were compared. Patients with babesiosis from southern New England (n = 25) and subjects with no history of babesiosis from southern New England (n = 55) and Iceland (n = 50) were enrolled in the study. Anti-Babesia antibody titers were determined in a blinded fashion by IFA test. The range of test results in the four laboratories was 88%-96% sensitivity, 90%-100% specificity, 69%-100% positive predictive value, and 96%-99% negative predictive value. Interlaboratory and intralaboratory concordance ranged from 84% to 85% and 94% to 100%, respectively. This B. microti IFA procedure is a sensitive, specific, and reproducible method for diagnosing babesiosis and is suitable for use as a standard in laboratories testing human sera for B. microti antibody.

Adult↗
PubMed1997

Down-regulation of cell-surface CD4 co-receptor expression and modulation of experimental allergic encephalomyelitis.

Pre-immunization with autoantigens confers resistance in experimental models of autoimmune diseases. Since non-self molecules can also be protective, it is conceivable that part of the effect rests on a non-specific attenuation of the immune response. This study is aimed at identifying mechanisms by which pre-immunization with a moiety suspended in incomplete Freund's adjuvant (IFA) protects from experimental allergic encephalomyelitis (EAE). Lewis rats were immunized with each of either concanavalin A, lipopolysaccharide, bovine serum albumin, 70 or 65 kDa heat shock proteins, or myelin basic protein. All moieties were given in IFA 3 weeks prior to EAE induction. Serial cytofluorimetric monitoring of B cells and of the alpha beta TCR+, CD4+, CD8+, CD45high and CD45low cells was performed. IFN-gamma and IgG1 production was evaluated in parallel. All moieties were able to attenuate or abrogate the clinical signs of EAE. At day 4 and 10 after EAE induction, the surface expression of the CD4 molecule was down-regulated on T lymphocytes. This down-regulation was most evident in animals with the highest degree of clinical protection. By day 21 post-immunization, CD4 expression was restored. The same animals also showed an increase in the B cell percentage and Th2-related IgG1 production while IFN-gamma secretion was reduced. Pre-immunization with diverse antigens suspended in IFA confers resistance to EAE induction. The down-regulation of the CD4 co-receptor accompanied by events suggestive of an immune deviation may be a general mechanism that contributes to the protection.

Animals↗
PubMed2000

Reaching young Indonesian women through marriage registries: an innovative approach for anemia control.

In an effort to build iron stores before pregnancy and reduce the high prevalence of anemia in Indonesia, the Ministry of Health/Indonesia and the MotherCare project implemented an anemia control program for newly wed women. As part of an existing program to counsel couples about marriage and require them to obtain tetanus toxoid immunization before obtaining a marriage certificate, women also were counseled to buy and take 30-60 iron-folate (IFA) tablets. Women (n = 344) were enrolled from one of three participating districts in South Kalimantan, Indonesia. At first monitoring, at least 30 d after baseline, 261 women were tested for hemoglobin and asked about their IFA tablet consumption and knowledge of information, education, and communications (IEC) materials promoted through the program. Results showed that there was a decrease in the prevalence of anemia from 23.8 to 14.0% over the course of the program, 98% of women had taken at least some IFA tablets and 56% had taken >30 tablets.

Adult↗
PubMed1995

HIV-1 infection of human brain-derived microvascular endothelial cells in vitro.

We examined the ability of human immunodeficiency virus (HIV) type 1 (HIV-1) to infect in vitro, primary brain-derived human microvascular endothelial cells (HMEC) that constitute the blood-brain barrier (BBB). Immunofluorescence (IFA) and antigen capture assays failed to demonstrate p24 antigen from HIV inoculated endothelial cells and supernatants did not contain detectable levels of reverse transcriptase (RT). HIV could be rescued by cocultivation of infected HMEC with a susceptible T-lymphocyte line (CEM-SS), which were then shown to form syncytia and produce RT activity and p24 Ag (IFA, antigen captive assay). Polymerase chain reaction (PCR) was successfully used to amplify HIV-specific gag and env gene sequences from HMEC. CD4 expression was not identified on these cells by IFA. These results suggest that HIV infection of BBB endothelium occurs, but that viral replication is minimal. Infection of the BBB by HIV may give the virus a foothold in the CNS and suggests that the brain might be infected directly and may not be limited to just the passage of infected mononuclear cells.

Blood-Brain Barrier↗
PubMed2000

Identifying human herpesvirus 8 infection: performance characteristics of serologic assays.

Epidemiologic studies of infection with the oncogenic human herpesvirus 8 (HHV-8) depend on serologic methods to diagnose infection. However, optimal strategies for identifying HHV-8 infection remain undefined. We therefore evaluated four enzyme-linked immunoassays (EIAs) and one immunofluorescence assay (IFA) using sera from 87 individuals with the prototype HHV-8 disease, Kaposi's sarcoma (KS), and 210 participants in a hemophilia study (who were presumed not to be infected with HHV-8). Assays performed reasonably well in distinguishing between infected and uninfected persons, with receiver operator curve areas between 0.86 and 0.96. Nonetheless, IFA had only 86% sensitivity and 88% specificity, and no EIA simultaneously had sensitivity and specificity above 90% for any of the optical density (OD) cutpoints used to define seropositivity. Some assays were markedly less sensitive with diluted KS sera, suggesting that they poorly identify low-titer antibodies present in asymptomatic infection. We also developed a classification tree that categorized individuals as seropositive if they had OD > 2.00 on recombinant K8.1 protein EIA or if they had both K8.1 OD between 0.51 and 2.00 and positive IFA results; this strategy had between 80% and 90% sensitivity and 95% and 100% specificity. Overall, assays performed adequately for use in most epidemiologic investigations, but wider applications will require improved tests.

AIDS-Related Opportunistic Infections↗
PubMed2003

Epidemiologic, clinical and laboratory features of scrub typhus in thirty Thai children.

BACKGROUND: Scrub typhus, a potentially fatal rickettsial infection, is common in Asia. Although serologic surveys suggested that as many as one-fourth of cases of scrub typhus might be in children, very few reports of childhood scrub typhus are available in the medical literature. OBJECTIVES: To document the clinical, laboratory and epidemiologic characteristics of pediatric patients with scrub typhus. METHODS: From January 1, 2000 to December 31, 2001, all pediatric patients at Chiang Mai University Hospital who had obscure fever for >5 days were tested for indirect immunofluorescent antibody (IFA) against Orientia tsutsugamushi, the causative organism of scrub typhus. Scrub typhus was diagnosed on the basis of either a single IFA titer against O. tsutsugamushi > or =1/400 or a 4-fold or greater rise in IFA titer to at least 1/200. RESULTS: Thirty children with scrub typhus were enrolled. Most were diagnosed during the rainy months of June to November. Common physical signs included lymphadenopathy (93%), hepatomegaly (73%), eschar (68%), conjunctival hyperemia (33%), maculopapular rash (30%) and splenomegaly (23%). Eleven patients had interstitial pneumonitis and 1 patient had meningitis. All patients responded well to doxycycline or chloramphenicol. The average interval to defervescence after treatment was 29 h (range, 6 to 72). CONCLUSIONS: Clinical and epidemiologic features of 30 pediatric patients with scrub typhus are reported in a prospective study. The presence of eschar was helpful in making the diagnosis. Complications included pneumonitis and meningitis. All cases responded well to treatment with antibiotic.

Adolescent↗
PubMed1999

Seroprevalence of Bartonella henselae in cats in Germany.

Bartonella henselae and B. quintana infections in man are associated with various clinical manifestations including cat-scratch disease, bacillary angiomatosis and bacteraemia. While cats are the natural reservoir for B. henselae, the source of B. quintana is unclear. In this study, the sera of 713 cats from Germany were examined for the presence of antibodies against B. henselae, B. quintana or Afipia felis by an indirect immunofluorescence assay (IFA). Bartonella-specific antibody titres of > or =50 were found in 15.0% of the cats. There was substantial cross-reactivity among the various Bartonella antigens, although single sera showed high titres against B. henselae but not against B. quintana and vice versa. Antibodies against A. felis were not detected in any of these cats. Statistical analysis indicated that there is no correlation between Bartonella infections and the sex, age or breed of the cat or its hunting behavior. There was also no correlation between bartonella and toxoplasma infections in cats. However, whereas 16.8% of cats from northern Germany had B. quintana-specific antibodies, only 8.0% of cats from southern Germany were seropositive for B. quintana. No statistically significant difference was found for B. henselae. IFA-positive and IFA-negative sera were used for immunoblot analysis including B. henselae and B. quintana. Marked reactivity was observed with protein bands at 80, 76, 73, 65, 37, 33 and 15 kDa. The results of this study suggest that B. henselae, and possibly a B. quintana-related pathogen, but not A. felis, are common in cats in Germany, and that there are differences in the geographic distribution of bartonella infections in cats.

Animals↗
PubMed2006

Evaluation of antigenic variations between two virulent toxoplasma strains.

Toxoplasma gondii infection in humans is routinely assessed by serological means. Here, the authors attempted to compare the response of different Toxoplasma strains to serological tests and to evaluate the antigenic profiles of the RH and RH Ankara (TRH) strains with Western blotting. Anti-Toxoplasma IgG antibodies of 72 patients were examined with the indirect immunofluorescence antibody (IFA) test, ELISA and Western blotting (WB) by using antigen from both strains. Antigenic variations between strains did not affect IFA and ELISA test results, but qualitative and quantitative differences between the WB patterns were observed. A number of bands with molecular masses varying between 17 and 105 kDa were detected in WB. Fourteen different bands were obtained with the assay performed with RH strain antigen. An additional four bands were observed with TRH strain antigen. Also, an 80 kDa band was observed to stain darker in the blot with TRH strain antigen, whereas with RH strain antigen 30 and 38 kDa bands were darker. The results showed that strain-specific polymorphism in tachyzoite antigens of different Toxoplasma strains is important in the evaluation of WB but not in conventional serological analyses such as ELISA and IFA.

Animals↗
PubMed2005

The validity of serologic tests for Trypanosoma cruzi and the effectiveness of transfusional screening strategies in a hyperendemic region.

BACKGROUND: This study aims at obtaining unbiased estimates of the sensitivity and specificity of existing screening tests for Trypanosoma cruzi and at simulating the effectiveness of alternative screening strategies at different prevalence rates. STUDY DESIGN AND METHODS: A systematic random sample of 400 was taken from 1200 banked serum samples of donors screened between August 1998 and January 1999 in Santa Cruz, Bolivia. Samples were tested with indirect hemagglutination test (IHA), indirect immunofluorescence assay (IFA), and four enzyme-linked immunosorbent assays (ELISAs). Sensitivity and specificity of tests were estimated through latent class analysis. RESULTS: The sensitivity of individual tests ranged from 96.5 to 100 percent, and their specificity from 87.0 to 98.9 percent. Combinations of two tests used in parallel would, even at 40 percent prevalence, only miss approximately 1 infected unit per 10,000 screened. At 5 percent prevalence, however, they would yield 75 to 120 false-positive units per 1000 units screened. Parallel testing with IHA plus ELISA or with IHA plus IFA is marginally more cost-effective, compared to single IHA testing, than single ELISA or single IFA testing, regardless of the T. cruzi prevalence. CONCLUSIONS: Routine blood donor screening for T. cruzi with a single test results in unacceptable numbers of false-negative samples in highly endemic areas or in at risk population groups. Adding a second test seems mandatory, but which one to choose depends on local cost components and feasibility.

Animals↗
PubMed1983

Delayed-type hypersensitivity (DTH) response to dengue virus in mice: effect of route of sensitization and splenectomy.

This study was designed to determine the role of the sensitization route and the spleen in the development of delayed-type hypersensitivity (DTH) to dengue virus in mice. DTH was measured by footpad swelling response. Strong but transient DTH was produced in cyclophosphamide (CY) pretreated mice sensitized subcutaneously (s.c.) or intravenously (i.v.) with dengue virus type 4. Subcutaneous inoculation of virus in incomplete Freund's adjuvant (IFA) further enhanced the DTH elicited. The time course of DTH generated by s.c. and i.v. sensitization were similar with the peak reactivity seen on day 6 after sensitization. Poor DTH was observed in mice given an i.p. inoculation even when CY and/or IFA were used. Intracerebral (i.c.) inoculation also sensitized mice poorly. Splenectomized mice showed enhanced DTH response when compared to intact mice. In contrast to intact mice, pretreatment of splenectomized mice with CY did not alter the DTH level. Splenectomized mice inoculated s.c. with virus in IFA showed poorer DTH than mice sensitized with virus alone.

Animals↗
PubMed1994

Effect of adjuvant formulations on the induction of virus-neutralizing and virus-binding antibodies by chemosynthetic peptides of VP1 of foot-and-mouth-disease virus.

Synthetic peptides corresponding to the 141-160 amino acid sequence of the protein VP1 of virus type O1 Kaufbeuren (O1K) and A5 Riems (A5R) were conjugated to thyroglobulin and mixed with complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA) together with Quil A. Although the peptide of A5R, together with IFA and Quil A, or with CFA, elicited a high antibody response to the virus in the ELISA, formula containing both IFA and Quil A induced only high titres of virus-neutralizing antibodies in rabbits. These adjuvant formulas did not display significant differences with regard to side effects.

Adjuvants, Immunologic↗
PubMed1994

Seroprevalence of bovine immunodeficiency-virus (BIV) antibodies in the cattle population in Germany.

Serum samples from 380 cattle were analysed for the presence of bovine immunodeficiency-virus (BIV) antibodies by focus immunoassay (cell-ELISA) and immunofluorescence assay (IFA). All specimens originated from dairy farms in the eastern part of Germany, which had been randomly collected during the period 1989-1991. The cattle were clinically healthy and free of bovine leukaemia virus (BLV) and bovine-virus diarrhoea-virus (BVDV) antibodies. Infection of cell lines with BIV was monitored by syncytia formation, cell-ELISA, and immunofluorescence. The seroprevalence of BIV antibodies was 6.6%, as determined by cell-ELISA. Comparison of IFA and cell-ELISA showed that all IFA positive sera were also positive in cell-ELISA. However, additional sera were reactive only in cell-ELISA. This first report suggests that BIV infection may cause minor problems in German cattle, while BIV is present in a similar prevalence to that reported from other countries.

Animals↗