Efficacies of US Food and Drug Administration-licensed HIV-1-screening enzyme immunoassays for detecting antibodies to HIV-2

Alternative algorithms for human immunodeficiency virus infection diagnosis using tests that are licensed in the United States

Serodiagnosis of human immunodeficiency virus (HIV) infection in the United States has traditionally relied on a sequential two-test algorithm: an initial screen with an enzyme immunoassay (EIA) and reflex testing of EIA-reactive specimens with a more specific supplemental test such as Western blotting or immunofluorescence. The supplemental tests are tedious, subjective, and expensive. In addition, there have been major improvements in the performance and accuracy of the EIA tests as well as the introduction of rapid serologic tests (RT) and HIV nucleic acid amplification tests (NAAT). Related to these improvements is the possibility that alternative algorithms using combinations of currently approved HIV tests may function as well as if not better than the current algorithm, with more flexibility, improved accuracy, and lower cost. To this end, we evaluated the performance of 12 currently licensed tests and 1 in-house HIV test (6 EIA, 4 RT, and 3 NAAT) on panels of plasma samples from HIV-infected (n = 621 HIV type 1 [HIV-1] and 34 HIV-2) and uninfected (n = 513) people and of sequential specimens from people early in seroconversion (183 specimens from 15 patients). Test combinations were analyzed in two dual-test (sensitivity-optimized and specificity-optimized) algorithms and in a three-test (tie-breaking) algorithm, and performance was compared to the conventional algorithm. The results indicate that alternative algorithm strategies with currently licensed tests compare favorably with the conventional algorithm in detecting and confirming established HIV infection. Furthermore, there was a lower frequency of discordant or indeterminate results that require follow-up testing, and there was improved detection of early infection.

Use of an acute seroconversion panel to evaluate a third-generation enzyme-linked immunoassay for detection of human immunodeficiency virus-specific antibodies relative to multiple other assays

A human immunodeficiency virus type 1 (HIV-1)/HIV-2 antibody screening assay, the Genetic Systems HIV-1/HIV-2 PLUS O EIA, was compared to several established screening or confirmatory tests using an acute HIV seroconversion panel. The HIV-1/HIV-2 PLUS O EIA showed an improved sensitivity over all tested antibody screening methods, and detected antibody in 7 of 19 specimens found to be negative by a first-generation EIA but positive for the presence of HIV RNA.

New methods for the detection of HIV

In the past few years, several strides have been made in the ability to detect the presence of HIV-1 and HIV-2. This article discusses recent advances in serologic testing, including routine ELISA and Western blot tests, rapid HIV tests, home collection kits, and HIV tests using nonserum samples. The clinical application of nucleic acid-based tests also is discussed. Finally, appropriate use of these tests in both acute HIV-1 infection and in infants is reviewed.

Surveillance of HIV-1 genetic subtypesand diversity in the US blood supply

BACKGROUND

Recent reports of variant (non-subtype B) HIV infections in US populations have raised concerns about the sensitivity of subtype B virus-based donor screening and diagnostic assays. This study was designed to determine the prevalence and genetic diversity of HIV subtypes in US blood donors over the last two decades.

STUDY DESIGN AND METHODS

Three groups were studied: hemophiliacs infected by clotting factor concentrates in the early 1980s (n = 49), blood donors retrospectively identified as being seropositive in 1985 (n = 97), and blood donors identified as seropositive between 1993 and 1996 (n = 405). Subtype assignment was based primarily on heteroduplex mobility analysis (HMA) of HIV-1 env, with DNA sequence confirmation of selected specimens. HIV peptide-based EIA serotyping was used to rule out HIV-2 and group O infections and to serotype HMA-refractory specimens.

RESULTS

Of 551 specimens, 535 (97%) were assigned subtypes; 532 (99%) of these were subtype B. Three postscreening donations (1%) were assigned non-B subtypes (2 A, 1 C). Two of these three donors were born in Africa; the third was born in the United States and reported no risk factors other than heterosexual activity. HMA distribution plots showed an increase in env diversity among HIV-1 group B strains over time.

CONCLUSION

The results support the need for continued surveillance of HIV subtype diversity and ongoing validation of the sensitivity of HIV diagnostic assays to non-B subtype infections.

Infection with HIV-1 group O

The author presents the case history of the first patient with HIV-1 group O reported in the United States. The various human retroviruses and their clinical syndromes are described and the increasing diversity of HIV-1 strains and their spread are documented. The discovery of the divergent group O and its spread from endemic areas are discussed. The clinician is alerted to the pitfalls of laboratory diagnosis and is advised to seek special studies when clinical findings and epidemiologic history suggest the possibility of HIV infection.

Differentiation of human immunodeficiency virus type 1 (HIV-1) infections with HIV-2-cross-reacting antibody from mixed infections with HIV-1 and HIV-2 by serological absorption test

The interpretation of dual seroreactivity with human immunodeficiency virus type 1 (HIV-1) and HIV-2 in blood samples is a serious problem facing AIDS researchers worldwide. Some samples of sera from HIV-1-infected patients showed a serological cross-reaction with HIV-2, causing confusion regarding the serodiagnosis. Therefore, we tried to differentiate these serum samples from those containing real mixed infections with both types of virus. Sera from patients with HIV-1 infections with HIV-2 cross-reacting antibody in Japan were distinguished from sera from patients with mixed infections with HIV-1 and HIV-2 in West Africa by our serological cross-absorption test, which proved to be highly specific and useful for serodiagnosis.

Evaluation of a dipstick method for the detection of human immunodeficiency virus infection

Serology has been a fundamental tool to prevent post-transfusional infection with human immunodeficiency virus (HIV) and for epidemiological surveys, the first step to attempt control of the pandemia. Enzyme immunoassay is in widespread use. Nevertheless, simpler methods are needed in many countries, where laboratory facilities and trained personnel are limited, and HIV prevalence is high. The evaluation of a simple and noninstrumented HIV antibody test is presented here. The test employs synthetic antigens of HIV-1 and HIV-2 attached to the teeth of a polystyrene comb, which fit into the wells of standard microtiter plates where samples are diluted. Captured antibodies are developed with colloidal gold-labeled Protein A. Three seroconversion panels plus 662 samples were tested, including HIV-1 and HIV-2-infected individuals, normal blood donors, and a noninfected baby born to a seroreactive mother. When compared with enzyme-linked immunosorbent assay (ELISA) and Western blot, the dipstick showed 100% sensitivity and 98.7% specificity. The simplicity of result evaluations and excellent reagent stability make the dipstick suitable for small blood banks and for epidemiological surveys.

Sentinel surveillance for HIV-2 infection in high-risk US populations

OBJECTIVES

We conducted sentinel surveillance in persons practicing behaviors known to transmit retroviruses to determine the US presence and extent of human immunodeficiency virus type 2 (HIV-2).

METHODS

Sentinel surveillance for HIV-2 was conducted by testing 31,533 anonymous blood specimens from patients at sexually transmitted disease clinics, injecting drug users at treatment centers, and clients at HIV counseling and testing sites in 14 US cities where West African immigrants often settle. Specimens were tested by HIV-1 and HIV-2 whole virus and synthetic peptide enzyme immunoassay and confirmed by HIV-1 and HIV-2 Western blots.

RESULTS

Nearly 10% of 31,533 sera were positive for HIV-1. Two heterosexual Black male sexually transmitted disease patients were infected with HIV-2. One of the HIV-2 positive specimens did not cross-react on HIV-1 enzyme immunoassay screening. One client had antibodies consistent with malarial infection in West Africa; the other, who had syphilis, did not have antibodies to malaria or to any of 20 arboviruses present in Africa.

CONCLUSIONS

Clinics serving clients from HIV-2 endemic areas should test persons practicing risk behaviors for both HIV-1 and HIV-2. Sentinel surveillance for HIV-2 serves as an early warning system for the possible spread of this virus in the United States.

Evaluation of testing algorithms following the use of combination HIV-1/HIV-2 EIA for screening purposes

The licensure of combination human immunodeficiency virus type 1 and type 2 (HIV-1/HIV-2) enzyme immunoassays (EIAs) by the Food and Drug Administration has been accompanied by a recommendation that U.S. blood banks begin testing the nation's blood supply for HIV-2 by June 1, 1992. The performance of a recently licensed combination HIV-1/HIV-2 EIA (Genetic Systems) was evaluated using 3100 sera collected in the United States. A total of 2,049 sera were obtained from populations with low risk for HIV infections, and 1,051 sera from populations with high-risk behaviors. The combination EIA, in comparison with monospecific EIA, was found to be 100% sensitive for HIV-1 for both populations. The high-risk population had an HIV-1 seroprevalence rate of 17.4%, with a positive predictive value (PPV) of 97.3%. The low-risk population had an HIV-1 seroprevalence of 0.05% with a PPV of 8%. The incorporation of the combination EIA in various testing algorithms was also evaluated, and recommendations are given with consideration for the type of screening and populations involved.

Enzyme-linked immunosorbent assay (ELISA) for HIV antibody by a glass slide technique

An enzyme-linked immunosorbent assay (ELISA) technique is described which utilizes a commercially available glass microscope slide coated with hydrophobic teflon in such a pattern as to give 30 small circular wells, each of which has a glass bottom. Each well serves as a solid phase, analogous to a microtiter well for adsorption of purified human immunodeficiency virus (HIV) antigens. Since only 5-10 microliter volumes of reagents are used and rinsing processing is simple, the cost per test is much less than most other ELISA technologies. HIV antigen is stable for over 1 year at 37 degrees C when dried on the glass slides. The sensitivity and specificity of the micro slide immunoenzymatic assay (Micro-SIA) was studied by testing randomly selected, known HIV-seropositive and seronegative plasma. Results compare well with microtiter and Western blot assays. A simple vertical-beam colorimeter is described (useful in the Micro-SIA) which can be easily assembled by the user from commonly available components.