Immunoperoxidase staining was compared with flowcytometry for the enumeration of lymphocyte subsets. The percentages obtained for peripheral blood lymphocytes using immunoperoxidase (CD3 = 76 CD4 = 27.9, B = 10.7 CD4/CD8 = 1.8) differed significantly from those obtained by flowcytometry (CD3 = 65.7 CD4 = 39.4, CD8 = 25.6, B = 16.7, HLA DR = 11.9 CD4/CD8 = 1.54) for certain subsets (CD3, CD4, B). There was no significant difference in lymphocyte subsets between children and adults using the same method. These differences are probably due to the different methods used to prepare lymphocytes for analysis. Other factors that should also be considered are the presence of CD4 antigen on monocytes and CD8 on natural killer cells.
Haemorrhagic septicaemia (HS) is an acute septicaemic disease of buffalo and cattle caused by Pasteurella multocida B:2 and E:2. Field outbreaks of HS are known to result in localisation of bacteria in the tonsils of surviving buffalo, confirming that animals can become carriers and the role of respiratory tract in the transmission of the disease. This report describes additional sites of localisation of P. multocida B:2 in surviving buffalo following experimental induction of HS.
An indirect enzyme immunoassay for the measurement of total 17alpha-hydroxyprogesterone (17OHP) in serum using monoclonal antibodies generated in our laboratory was developed. Here, (a) instead of extraction with solvents, serum was heated to free protein-bound 17OHP and assay was performed at pH 9.6, (b) to ensure uniform assay conditions for both standards and samples, buffer for standards contained charcoal-stripped pre-heated pooled cord serum. Assays were done in 96-well EIA microplates pre-coated with 17alpha-hydroxyprogesterone-3-(o-carboxymethyl)oxime: bovine serum albumin. Secondary antibody was horseradish peroxidase-linked sheep anti-mouse IgG polyclonal antibody. The method was accurate and suitable for screening for congenital adrenal hyperplasia.
Porcine gelatine is a common adulterant found in edible bird's nests (EBNs) used to increase the net weight prior to sale. This study aimed to develop indirect enzyme-linked immunosorbent assays (ELISAs) for porcine gelatine adulteration using anti-peptide polyclonal antibodies. Three indirect ELISAs were developed (PAB1, 2 and 3), which had limits of detection (LODs) of 0.12, 0.10 and 0.11 µg g(-1), respectively. When applied to standard solutions of porcine gelatine, the inter- and intra-assays showed coefficients of variation (CVs) less than 20% and were able to detect at least 0.5 ng µg(-1) (0.05%) porcine gelatine in spiked samples. The proposed ELISA offers attractions for quality control in the EBN industry.
A dot enzyme immunoassay (DEIA) for the detection of antibodies to dengue virus was tested for use as a tool in the presumptive diagnosis of dengue fever and dengue haemorrhagic fever. Paired sera from the following groups of patients were tested using the DEIA and the haemagglutination inhibition (HI) test: those with primary dengue fever; those experiencing a second dengue infection; and febrile patients who did not have dengue. The data obtained show that the DEIA can be effectively used at a serum dilution of 1:1000 to confirm presumptive recent dengue in patients with a second dengue infection. However, demonstration of seroconversion proved necessary for patients with primary dengue. At a serum dilution of 1:1000 the DEIA has a specificity of 97.3%. The role of this simple and rapid test in improving the effectivity of programmes for the control of dengue virus infection is discussed.
An in-house method which utilizes 14C-thymidine as a substrate was used to assay deoxythymidine kinase in serum. The method is sensitive enough to detect normal levels of serum deoxythymidine kinase and the assay procedure also enables rapid handling of multiple samples. With a total reaction volume of 60 ul, the enzyme reaction was found to be linear with concentrations for up to 650 U/L of TK activity. On studying serum deoxythymidine kinase (s-TK) activity with incubation time, there was a proportional increase in activity with the length of incubation time. "Within-batch" precision showed a coefficient of variation (CV) of 4.7% for serum with extremely high s-TK levels and a CV of 8.8% for serum with normal s-TK levels. S-TK showed a CV of less than 16.0% in its activity when stored at -8 degrees C and at -20 degrees C. The normal reference range obtained for s-TK activity was 8.6 +/- 7.5 U/L.
A new and rapid malaria immunoperoxidase assay using the enzyme horseradish peroxidase in place of fluorescein isothiocyanate was developed to allow the serological measurement of antimalarial antibody by light microscopy. Acetone-fixed thin blood films prepared from cultured Plasmodium falciparum were used as the source of antigen. This malaria immunoperoxidase assay is as sensitive as, and occasionally more sensitive than, the indirect fluorescent antibody assay. It is easy to perform and the antigen used does not show cross-reactivity with sera from nonmalarial diseases.
150 specimens from suspected herpes simplex genital and skin lesions were received in virus transport medium. They were inoculated into Hep-2 cell monolayers, examined for the presence of virus by cytopathic effect (CPE), direct immunoperoxidase (DIP) and direct immunofluorescence (DIF). Of 39 (26.0%) virus-positive specimens by CPE, 37 (24.7%) were HSV-positive by DIP and 36 (24.0%) by DIF staining. DIP staining had a sensitivity of 100%, specificity of 99.1%, positive predictive value of 97.3% and negative predictive value of 100% in relation to DIF as a standard test. Of 39 specimens positive by CPE, only 25.6% were HSV-positive within 24 h post-inoculation compared to 94% HSV-positive by DIP and DIF staining at the same time.
Partially purified DEN3 virus was used as antigen in a sensitive dot enzyme immunoassay (DEIA) for the detection of antibodies to flavivirus antigens. We describe here the method used to prepare and optimise the antigen-bearing nitrocellulose membranes and present the results obtained from screening 20 acute phase sera from patients shown to have had recent dengue infections by the haemagglutination inhibition (HI) test. Sixteen pairs of acute and convalescent sera from dengue-negative patients had no detectable antibody to dengue virus by HI. These were shown to have no antibody detectable by DEIA. Sera positive for dengue antibodies by HI had DEIA titers ranging from 10 to several thousand times greater than the titers detected by HI.
This case study demonstrates a 36-year-old ex-intravenous drug user (IVDU) who had been initially tested positive for human immunodeficiency virus (HIV) twice using Enzyme Immunoassay (EIA) method (Particle agglutination, PA done), but a year later he was tested HIV-negative. The patient was asymptomatic for HIV and T helper cells (CD4) count remained stable throughout this period. In light of this case, there may be a need to retest by molecular methods for high risk category patients who were initially diagnosed HIV-positive, but later showing an unexpected clinical course, such as a rising or stable CD4 titre over the years.
Human cytomegalovirus (HCMV) is a species-specific DNA virus of the Herpetoviridae family. After a primary infection, HCMV persists in a latent form most probably in bone marrow progenitor cells or in peripheral blood monocytes. The virus can reactivate to result in shedding of the virus leading to virus dissemination and new infections. Immunocompromized patients are the ones most vulnerable to serious diseases occasionally acquired in blood transfusions. In a human population, HCMV seropositivity increases steadily with age to become approximately 100% in adults. This study was performed to detect seropositivity among regular blood donors in The Hospital of the Universiti Sains Malaysia, in the state of Kelantan. Using an enzyme immunoassay, it was found that 97.6% of blood donors were HCMV-positive. HCMV is highly prevalent and may be endemic in Kelantan. Hence, long-term strategies are required for the reduction of disease dissemination, and to prevent the exposure of immunocompromized patients to the virus.
The indirect immunoperoxidase (HP) test has been used extensively in most government hospitals in Malaysia for the serodiagnosis of scrub typhus, murine typhus and tick typhus during the 1990s. The test was used to determine the IgG and IgM antibody titers in patients' sera for three rickettsial species, ie Orientia tsutsugamushi OT; the causative agent of scrub typhus), Rickettsia typhi (RT; the causative agent of murine typhus), and TT118 spotted fever group rickettsiae (TT; the causative agent of tick typhus). The serological findings obtained from Malaysian hospitals using the IIP test (1994-1999) were analyzed. During the six-year period, a total of 61,501 patients' sera were tested, of which 9.6%, 10.5%, and 12.9% had antibody (IgG and/or IgM of > or = 1:50) for OT, RT and TT respectively. A total of 8.6%, 9.8%, and 9.7% of sera had IgG antibody of > or = 1:50 for OT, RT, and TT respectively, indicating past infection. A total of 3.4%, 3.8%, and 6.4 % of sera had IgM antibody of > or = 1:50 for OT, RT, and TT respectively, indicating recent infection. A total of 2,986 (4.9%), 1,882 (3.1%), and 1,574 (2.6%) of sera had IgG and/or IgM antibody titers of > or = 1:400 for OT, RT, and TT respectively, suggesting active rickettsial infection. The seropositivity rates of OT, RT and TT varied according to geographical locations. While the seropositivity of OT remained constant during the six-year period, a reduction in the seropositivity of both RT and TT was noted during recent years. The serological findings reflect the endemicity of rickettsial diseases, including tick typhus, and endemic typhus in various parts of Malaysia. Awareness of these diseases by health and medical staff and by the general public is important if the mortality and morbidity associated with scrub typhus, tick typhus, and murine typhus in Malaysia, are to be reduced.
The traditional methods used in the diagnosis of dengue infection do not lend themselves to field application. As such, clinical specimens have to be sent to a central laboratory for processing which invariably leads to delay. This affects patient management and disease control. The development of the dengue IgM dot enzyme immunoassay has opened up the possibility of carrying out the test in peripheral health settings.
This study describes the use of an IgM capture ELISA using cell culture derived antigens and a polyclonal rabbit antiflavivirus antisera for the detection of dengue positive cases. The IgM capture ELISA is compared with the dot enzyme immunoassay and the results are discussed in the context of dengue endemicity.
An immunohistochemical assay was developed combining an avidin-biotin-glucose oxidase complex procedure (ABC-GO) with light microscopy to detect specific antibody against Plasmodium falciparum. Thin blood films were prepared from culture material of P. falciparum and fixed with acetone. Antibody was detected by successive incubations with test serum, biotinylated goat antihuman antibody, avidin-biotin-glucose oxidase complex, and glucose oxidase substrate. In the presence of reactive serum, a blue precipitate formed on the parasites and could be visually observed with a 40x objective. Sera from patients with single infections for P. vivax or P. ovale were unreactive. No cross-reactivity was observed with sera from patients with rheumatoid arthritis, filariasis, amebiasis, schistosomiasis, dengue, scrub typhus, leptospirosis, or toxoplasmosis. The sensitivity of ABC-GO is comparable to that of the indirect fluorescent antibody test.
An indirect immunoperoxidase test was compared with an indirect fluorescent antibody test and the Weil-Felix OXK test for serodiagnosis of scrub typhus by measuring the rickettsial antigen specific activity of IgG, IgM, and whole globulin. Acute and convalescent sera from 50 Rickettsia tsutsugamushi isolate-positive scrub typhus patients and from 45 febrile patients diagnosed as having diseases other than scrub typhus were tested. The receiver operating characteristic for each test showed that the indirect immunoperoxidase and indirect fluorescent antibody tests were more sensitive and specific than the Weil-Felix test using convalescent and acute as well as paired sera. The indirect immunoperoxidase test showed no cross-reactivity when R. tsutsugamushi antigen was tested against sera collected from patients living outside the scrub typhus-endemic area with diseases other than scrub typhus. The indirect immunoperoxidase and indirect fluorescent antibody tests were comparable in measured response to R. tsutsugamushi, R. typhi, and TT-118 (spotted fever group) antigen. Thus the indirect immunoperoxidase test represents a sensitive, specific, reproducible, and practical semiquantitative test for rickettsial disease diagnosis.