Strategies for laboratory HIV testing: an examination of alternative approaches not requiring Western blot.

Advances in laboratory tests for antibodies to human immunodeficiency virus (HIV) have permitted the development of alternative HIV testing strategies that do not require use of the Western blot approach. Three strategies are proposed. In strategy I, sera are tested for HIV antibody using an enzyme-linked immunosorbent assay (ELISA)/rapid/simple (ERS) test; in strategy II, sera reactive in an initial ERS test are retested using a second ERS test; strategy III involves retesting with a third ERS test all sera reactive in two previous ERS tests. Where the objective is identification of asymptomatic HIV-infected individuals, strategy III is proposed where HIV prevalences in the study population are < or = 10%, and strategy II at prevalences > 10%. Strategy II is recommended where the diagnosis of HIV-related disease requires HIV testing. For serosurveillance, strategy II is recommended if the prevalence is < or = 10%, and strategy I if the prevalences are > 10%. Use of strategy I is recommended for transfusion and transplantation safety, at any prevalence. Lower-cost laboratory HIV testing will permit such testing to become more widely available.

PIP: Testing of sera for antibodies to HIV typically involves screening with enzyme-linked immunosorbent assays (ELISA) and subsequent confirmation with Western blot (WB). Western blot testing, however, is relatively expensive and technically demanding. Recent technological advances have produced tests which provide results equivalent in accuracy to those obtained by WB. These include new ELISA tests, simple tests, and rapid tests. Simple tests are those which are easily learned and require no additional equipment or instrumentation, while rapid tests yield results in 30 minutes or less. The lower cost of these methods will allow HIV testing to become more widely available. The authors propose alternative laboratory HIV testing strategies based upon these newer ELISA/rapid/simple tests (ERS). Strategy 1 tests sera for HIV antibody using ERS tests. Strategy 2 retests sera reactive to initial ERS, and strategy 3 simply retests reactive sera a third time with ERS tests. Strategy 1 is recommended for transfusion and transplantation safety at any prevalence of HIV infection is selected populations. Strategy 1 is also recommended for serosurveillance in study populations where the prevalence of HIV infection is greater than 10%, but strategy 2 is recommend where prevalence are less than or equal to 10%. Strategy 2 is generally recommended when diagnosis of HIV-related disease requires HIV testing. Finally, strategy 3 is proposed to identify asymptomatic HIV-infected individuals where HIV prevalence in the study population are less than or equal to 10%, but strategy 2 will suffice where prevalence are greater than 10%.

HIV-1 western blot: development and assessment of testing to resolve indeterminate reactivity.

OBJECTIVE: To reduce the number of HIV-1 Western blot (WB)-indeterminates requiring follow-up and the time taken to provide a clear positive or negative result. DESIGN: In the first of two stages, a testing and follow-up strategy was developed to resolve anti-HIV-1 status of WB-indeterminates. In the second stage, implementation of this strategy was assessed. METHODS: After dividing indeterminates into four groups according to WB profile, samples were tested for anti-HIV-1, anti-HIV-2, anti-HTLV-I antibodies, and HIV-1 antigen using the most sensitive assays available. When testing failed to clarify anti-HIV-1 status, follow-up samples were taken to monitor changes in antibody status. RESULTS: Samples in two out of the four indeterminate groups were negative for anti-HIV-1. The other two groups required additional testing and/or follow-up to distinguish reactivity caused by anti-HIV-1 from cross-reactivity. CONCLUSION: Grouping HIV-1 WB-indeterminates according to profile allows a significant percentage to be reported as anti-HIV-1-negative, while additional testing may allow others to be reported as anti-HIV-1-positive. The remainder require a maximum of 3 months' follow-up to resolve anti-HIV-1 status.

Preparation and characterization of Salmonella H antibodies in mouse ascites fluid.

A method is described for raising antibodies to Salmonella H antigens in mice. Quantities of high titre antibodies of specificities similar to the traditional methods using rabbits are obtained.

Use of a conserved immunodominant epitope of HIV surface glycoprotein gp41 in the detection of early antibodies.

An enzyme immunoassay (EIA) utilizing a synthetic peptide analogue of HIV gp41 (amino acids 579-599, RILAVERYLKDQQLLGIWGCS) as antigen was compared with two commercial assays (Genetic Systems, Abbott ENVACORE) for the ability to detect antibodies in the early stages of infection. Two panels, consisting of 96 sera from 15 people and 140 sera from 44 people seroconverting to HIV, were examined. In the first group the synthetic peptide assay (gp41 EIA) detected antibodies before the Genetic Systems EIA in seven out of 15 people and concurrently in the remaining eight. With the second panel the Abbott ENVACORE assay detected antibodies before the gp41 EIA in two out of 44 people while the gp41 EIA detected antibodies first in six out of 44. In the remaining 36 people antibodies were detected simultaneously by the two tests. The gp41 EIA usually detected anti-HIV antibodies before or concurrently with the two commercial assays examined suggesting that the epitope cluster represented by this peptide is recognized early in infection.

Detection of anti-HIV immunoglobulin M by particle agglutination following acute HIV infection.

In a study of 23 subjects infected with HIV, a modified particle agglutination assay was used to detect anti-HIV-specific immunoglobulin M (IgM). The presence of anti-HIV IgM was demonstrated in every subject, becoming detectable 1-2 weeks after the onset of acute symptoms, and showing a variable duration of 1-5 weeks. Anti-HIV immunoglobulin G (IgG) developed 1-2 weeks after anti-HIV IgM. Particle agglutination detected the presence of specific antibody up to 7-10 days earlier than the Abbott recombinant or Genetic Systems enzyme immunoassays. In this study, all subjects with acute infection became clearly positive by Western blot within 3 months of the onset of acute symptoms.

An evaluation of competitive and second generation ELISA screening tests for antibody to HIV.

Two competitive anti-HIV ELISA screening assays (Behring and Wellcozyme) and two second generation assays using antigens generated by recombinant DNA technology (Abbott) and synthetic peptides (Biochrom) were evaluated against common panels of anti-HIV positive sera and sera known or thought likely to give false positive reactions. The assays were also tested on fresh sequential blood donations. Conventional estimates of sensitivity and specificity did not reveal a significant difference between the assays. Statistical analyses using log10 transformed data to determine delta values (the distance of the mean optical density (OD) ratio from the cut-off measured in standard deviation units) showed the Abbott assays to have the highest probability (greater than 99.99%) of detecting anti-HIV positive samples and the Behring assay as having the highest probability (greater than 99.99%) of correctly identifying anti-HIV negative specimens. The combined data from conventional estimates of sensitivity and specificity and delta values suggests that the Abbott assay is the test of choice for screening purposes.

A preliminary evaluation of five HIV antigen detection assays.

Five commercial assays for detecting HIV antigen were evaluated using a panel of 40 coded samples in six laboratories. All assays were capable of detecting HIV-1 antigen (HIV-1 Ag), and are likely to prove useful for monitoring supernatant fluids from a variety of cell cultures. The concentration of HIV-1 protein which the assays detected varied from 25 ng/ml down to 25 pg/ml. Three of the five assays were also able to detect HIV-2 Ag. More extensive evaluations are needed to determine the sensitivity and specificity of these assays on serum samples and body fluids.

Presence of antibodies to human immunodeficiency virus-1 in reference reagents of human origin in diagnostic kits.

We tested 54 reagents of human origin that were included in a number of diagnostic kits to be used as positive or negative control material, and for quality assurance, for the presence of antibodies to human immunodeficiency virus-1 (HIV-1). Of these, 12 (22%) reagents were found to give positive results for antibodies to HIV-1 by enzyme-linked immunosorbent assay and/or supplementary tests. These results suggest that some diagnostic reagents of human origin may be contaminated with HIV-1 and potentially may be infectious.

Comparison of enzyme immunoassay and reverse transcriptase assay for detection of HIV in culture supernates.

An enzyme immunoassay (EIA) was developed for detection of human immunodeficiency virus antigen (HIV Ag) in tissue culture supernatants. The assay was found to be specific for HIV and cheaper, easier to perform and more sensitive than the generally used reverse transcriptase (RT) assay. Cultures of peripheral blood leucocytes (PBL) from 106 patients with acquired immune deficiency syndrome (AIDS), AIDS related complex (ARC), healthy anti-HIV positive subjects and healthy anti-HIV negative subjects were held for 35 days and the supernatant fluid tested at regular intervals by EIA and RT. Of these 106 cultures, the presence of HIV was detected by EIA in 27 and by RT in 21. While six cultures were positive by EIA alone, none were positive by RT alone; the specificity of the results in the six EIA positive RT negative cultures was confirmed by subculture. In the 21 cultures in which HIV was detected by both techniques, the EIA became positive first on 10 occasions; in the remaining cultures both tests became positive at the same time. The HIV Ag assay reduces the time taken to process specimens and thus increases the efficiency and reduces the cost of isolation procedures.

Investigation by enzyme-linked immunosorbent assay of Salmonella H antigen-antibody reactions.

An indirect enzyme-linked immunosorbent assay has been used for the detection of Salmonella group H antibodies.

The use of the microagglutination technique to determine the antibody status of healthy New Zealanders to Brucella abortus.

Sera from healthy blood donors from different parts of New Zealand, collected between 1977 and 1980, were analysed by the microagglutination technique for antibodies against Brucella abortus. Populations from both urban and rural areas were studied. The technique was shown to be capable of handling the 3351 sera studied and thus to be a useful screening test to assess the immune status of large populations. The results demonstrated some of the effects on the human population of the successful bovine brucellosis eradication programme.

Comparison of standard tube and microagglutination techniques for determining Brucella antibodies.

A microagglutination method for determining the agglutinating and "blocking' antibodies to Brucella abortus is described. A collection of sera from healthy blood donors in two rural areas of New Zealand were tested by the microagglutination methods and the standard methods in tube. The results are compared and show that where discrepancies occur, these are due to the microagglutination methods being more sensitive. It is concluded that these are suitable methods for screening populations.

Antibodies against double-stranded RNA in patients with rheumatoid arthritis, osteoarthrosis and Paget's disease of bone.

Using a liquid phase radioimmunoassay to detect antibodies to 3H-labelled double-stranded RNA the premise that rheumatoid arthritis and Paget's disease of the bone may be associated with a chronic virus disease was examined. About 33% of patients with rheumatoid arthritis had antibody levels above the normal range and 11% had antibody levels below the normal range of controls (blood bank donors). The low binding activities were attributed to the action of a nuclease that degraded the dsRNA. Some patients with Paget's disease of bone had higher binding activities than the normal range and similar binding activity was also found in patients with osteoarthrosis. The increase in antibodies to double-stranded RNA did not correlate with increasing age.

Bacteriological aspects of a case of Brucella suis infection.

Brucella sinus biotype 1 was isolated from the blood of a 55 year old Tongan woman patient in Auckland Hospital. Problems in identification of this organism are described and discussed