Absence of HIV infection in blood donors with indeterminate western blot tests for antibody to HIV-1

Seroprevalence of HIV-1 and HIV-2 infection among children diagnosed with protein-calorie malnutrition in Nigeria

Excessive weight loss due to protein calorie malnutrition (PCM) is a significant problem in Nigerian children. This syndrome may be difficult to differentiate from the wasting disease caused by human immunodeficiency virus type 1 (HIV-1) infection. We studied 70 children admitted to the Baptist Medical Center in Ogbomosho, Nigeria in 1990 with PCM for prevalence of antibodies to HIV-1 and HIV-2. The cohort was from low-risk mothers and had a median age of 25 months (range, 4 months-9 years) with a weight deficit of at least 20% of the theoretical weight for age. Two sera were positive for anti-HIV-1 by both ELISA and Western blot (WB). A high prevalence of samples negative for HIV-1 antibody by ELISA were repeatedly reactive (11%, 8/70) or indeterminate (46%, 32/70) by WB. None of the sera was positive for antibody to HIV-2. There was no correlation of ELISA positivity or extent of WB banding with successful recovery from malnutrition. These results indicate a relatively low but significant prevalence of HIV-1 infection in Nigerian children with PCM. The high prevalence of indeterminate reactions in WB assays for HIV-1 suggests that other procedures may be necessary for confirmatory diagnosis of HIV-1 infection in this African population.

Idiopathic CD4+ T-lymphocytopenia--four patients with opportunistic infections and no evidence of HIV infection

BACKGROUND AND METHODS

We describe four patients without major risk factors for human immunodeficiency virus (HIV) infection, each of whom presented with severe opportunistic infections and was found to have idiopathic CD4+ T-lymphocytopenia. We performed assays to detect the presence of retroviruses and undertook immunophenotyping of subgroups of peripheral-blood lymphocytes.

RESULTS

The opportunistic infections at presentation included Pneumocystis carinii pneumonia, cryptococcal meningitis (two patients, one with concurrent pulmonary tuberculosis), and histoplasma-induced brain abscess. During 10 to 68 months of observation, none of the four patients had evidence of infection with HIV type 1 or 2 or human T-cell lymphotropic virus type I or II on the basis of epidemiologic, serologic, or polymerase-chain-reaction studies or culture, nor was there any detectable reverse transcriptase activity. Although all the patients had severe, persistent CD4+ T-lymphocytopenia (range, 12 to 293 cells per cubic millimeter), the CD4+ cell count progressively declined in only one and was accompanied by multiple opportunistic infections. All four patients had significantly reduced numbers of circulating CD8+ T cells, natural killer cells, or B cells (or all three).

CONCLUSIONS

These four patients had idiopathic CD4+ T-lymphocytopenia with opportunistic infections but no evidence of HIV infection. Instead of the progressive, selective depletion of CD4+ T cells characteristic of HIV infection, some patients with idiopathic immunodeficiency have stable CD4+ cell counts accompanied by reductions in the levels of several other lymphocyte subgroups.

Blood donations indeterminate in HIV-1 western blot analysed by IgM immunoblot and polymerase chain reaction

The presence of IgM antibodies to human immunodeficiency virus 1 (HIV-1) was investigated in blood donor sera which were indeterminate in anti-HIV-1 IgG Western blot testing. In 7 of 173 instances out of approximately 1,000,000 blood donation sera with an isolated anti-p24 IgG produced an anti-gp41-45 IgM immunoblot reaction. Applying polymerase chain reaction (PCR) to 29 indeterminate samples out of approximately 125,000 blood donations it was found that 2 of them were IgM-positive and also contained HIV-1-specific DNA sequences. Eleven months later 1 of these 2 donors was retested and found IgM and PCR negative.

AIDS: Part I

Acquired immunodeficiency syndrome (AIDS) is caused by infection with a pathogenic human retrovirus known as human immunodeficiency virus (HIV). Approximately 1 million people are currently infected with HIV in the United States, with 8 to 10 million infected individuals worldwide. The virus is transmitted predominantly through genital sexual contact, although orogenital spread has been rarely reported. Heterosexual transmission has been most common in the Third World, whereas male homosexual transmission has predominated in the United States and western Europe. Transmission through homosexual contact has been steadily declining over the past 5 years as transmission through illicit intravenous drug use and promiscuous unprotected heterosexual activity has increased. Sexually transmitted diseases that cause inflammatory or ulcerative lesions of the genital tract act as important cofactors in increasing the risk of transmission through sexual contact. Perinatal transmission of HIV occurs in approximately 30% of infants born to infected mothers. Transmission to infants through breast-feeding has also been documented. Health care workers have been infected with HIV through accidental high-risk percutaneous or mucous membrane exposures, albeit at a low transmission rate of 0.3%. Infection of patients by infected health care professionals is a rare event, having been reported only once in 10 years of the epidemic. Infection with HIV results in a chronic lifelong infection. The major targets for HIV are CD4+ T-helper lymphocytes and cells of monocyte/macrophage lineage. Infection of the T-helper lymphocyte ultimately results in the death of the cell. Over time (measured in years), a progressive destruction of the T-helper lymphocyte population occurs, which results in profound immune suppression. Infection of monocytes/macrophages is not cidal, but these cells do have functional alterations as a result of the infection, which may contribute to the immune deficiency. In addition, chronically infected tissue macrophages may act as an important reservoir for HIV, particularly in the central nervous system. Infection of the T-helper lymphocytes and monocytes/macrophages is mediated through attachment of HIV through a specific binding interaction between CD4 expressed in the plasma membrane of these cells and a surface glycoprotein on the virus, gp120. Once the virus nucleocapsid (core particle) enters the cytoplasm of the target cell, the viral RNA genome is reverse transcribed by a reverse transcriptase enzyme into proviral DNA. This proviral DNA migrates into the nucleus where it integrates into the host cellular genome, which results in a chronically infected cell.(ABSTRACT TRUNCATED AT 400 WORDS)

Essential HIV/AIDS facts. What you need to know in 1992

The fast pace of HIV/AIDS research and the wide spectrum of issues involved can be intimidating for busy primary care physicians who see HIV-infected patients infrequently. The information covered in this article is intended to form a core that should be a part of all physicians' medical knowledge today.

Indeterminate western blot patterns in a cohort of individuals at high risk for human immunodeficiency virus (HIV-1) exposure

Our objective was to map serial patterns of Western blot reactivity over time of a cohort of initially ELISA-negative, Western blot-indeterminate individuals from a high-risk group and to determine if these individuals were at increased risk of harboring occult HIV-1 infection. A 2-year prospective study used serial ELISA, two types of Western blot, immunologic profiles, HIV-1 culture, and analysis by polymerase chain reaction. Subjects were 20 ELISA-negative, Western blot indeterminate homosexual volunteers and 20 matched seronegative controls. Results showed that 19 of 20 study subjects completed a mean of 17.0 months of clinical and laboratory follow-up. Reactivities with p24 and/or with p55 were the two most commonly observed Western blot patterns, occurring in 70% of individuals. Specific Western blot reactivity was dependent upon the particular immunoblot preparation being used and varied considerably on a longitudinal basis. No individual pattern appeared predictive of an increased likelihood of subsequent seroconversion to HIV-1 relative to controls. By all other criteria including polymerase chain reaction analysis, samples from 17 of 19 individuals remained negative for HIV-1 at each time point. Two individuals evolved from an indeterminate to a positive Western blot and, simultaneously, from a negative to a positive polymerase chain reaction analysis, during follow-up. Our conclusions were as follows. ELISA-negative, Western blot-indeterminate individuals from a high-risk group show marked variability in immunoblot findings over time, and these patterns do not appear predictive of an increased likelihood of infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Reactivity patterns and infection status of serum samples with indeterminate Western immunoblot tests for antibody to human immunodeficiency virus type 1

Serum samples with indeterminate Western blot (WB) tests from 61 individuals whose sera were positive by enzyme-linked immunosorbent assay (ELISA) were studied in order to characterize their putative reactions with the human immunodeficiency virus (HIV) proteins and to resolve the HIV infection status of these individuals. The reaction observed by WB could not be confirmed either by radioimmunoprecipitation assay and subsequent electrophoresis (RIPA) or by use of LiaTek (Organon Teknika, Turnbout, The Netherlands) in 28% of the samples. Of the 86 samples that were indeterminate by WB, 66 reacted with p24 by WB; this reaction was confirmed by RIPA in only 21 (32%) and by LiaTek in 49 (74%) of the 66 samples. On the other hand, none of the indeterminate samples that reacted with HIV envelope proteins by WB did so by LiaTek, while 50% precipitated at least some of these proteins in the RIPA. The sensitivities of the three methods for detecting the antibody reaction with the different HIV proteins, which were studied with serial dilutions of positive serum samples, were similar. Thus, a lower sensitivity of RIPA or LiaTek does not seem to be the cause for the lack of reaction of the WB-indeterminate samples by these two methods. Sequential samples from individuals whose serum samples reacted by the three methods gave reproducible results, but all showed low antibody titers. Peripheral blood mononuclear cells obtained from three of the four individuals with sequential samples that reacted with HIV env proteins by WB and RIPA were negative for HIV provirus DNA after amplification by the polymerase chain reaction.

Multicenter evaluation of the novel ABN Western blot (immunoblot) system in comparison with an enzyme-linked immunosorbent assay and a different Western blot

A new, modular Western blot (immunoblot) system for human immunodeficiency virus (HIV) antibodies (ABN WesPage; Wellcome) was compared with enzyme immunoassays (Wellcome, Behringwerke, and Abbott) and with a U.S. Food and Drug Administration (FDA)-licensed Western blot (DuPont) in a multicenter study. A total of 649 serum samples from HIV patients at different stages of the disease, as well as from high-risk patients, from patients with conditions unrelated to AIDS, and from healthy blood donors, were used in the evaluation along with nine seroconversion panels. For evaluation of Western blot reactivity, both Centers for Disease Control (CDC) and FDA criteria were used. With the DuPont Western blot as the reference assay, the overall sensitivity and specificity of the ABN WesPage were 100 and 99.1%, respectively, when indeterminate results were not taken into account and when both tests were interpreted in accordance with CDC criteria. The DuPont Western blot detected significantly more antibodies to pol and gag gene products than the ABN WesPage. The ABN WesPage showed a higher positive rate of detection of viral envelope band gp160. When both Western blots were interpreted in accordance with CDC criteria, the ABN WesPage and the DuPont Western blot yielded 9.3 and 10.4% indeterminate results, respectively. When the DuPont Western blot was interpreted in accordance with the manufacturer's instructions (FDA criteria), 25.7% of the samples tested were regarded as indeterminate. The choice of interpretation criteria is of paramount importance for the evaluation of HIV Western blot patterns.

Significance of human T-lymphotropic virus type I indeterminant serological findings among healthy individuals

Follow-up studies on 67 blood donors with indeterminant serological findings for human T-lymphotropic virus (HTLV) type I by standard immunoassays showed no evidence of infection by polymerase chain reaction analysis for HTLV-I or HTLV-II nucleic acids or by antibody reactivity to a unique HTLV-I recombinant envelope protein, MTA-4. Among HTLV-I- or -II-infected individuals, a history of blood transfusion, past residence in established HTLV-I endemic areas or some association with intravenous drug use were common. In contrast, 85% of indeterminant cases had none of these risk factors. These observations suggest that healthy individuals with indeterminant serology for HTLV-I should not require additional studies.

Comparison of five commercial enzyme-linked immunosorbent assays and Western immunoblotting for human immunodeficiency virus antibody detection in serum samples from Central Africa

Detection by five different enzyme-linked immunosorbent assays (ELISAs) of antibody to human immunodeficiency virus (HIV) in sera from three Zairian populations consisting of 1,998 individuals with various risks for HIV infection was evaluated. Sera that were reactive by at least one assay and 10% of the nonreactive serum samples were analyzed by Western blot (immunoblot) by using U.S. Public Health Service interpretation criteria. Sera which were positive by ELISA for detection of antibody to HIV-1 and HIV-2 and negative or indeterminate by HIV-1 Western blot were also analyzed by HIV-2 Western blot. Overall, 443 (22.2%) serum specimens were HIV-1 Western blot positive, 390 (19.5%) had indeterminate HIV-1 Western blot patterns, and no samples were HIV-2 Western blot positive. The sensitivity of the ELISAs ranged from 97.5 to 99.8%, and the specificity ranged from 51.7 to 98.4%. By population group, the negative predictive value ranged from 97.1 to 100%, in contrast to the positive predictive value, which varied from 6.6 to 100%. Follow-up results for sera which were indeterminate for antibody to HIV-1 documented only four seroconversions (6.0%) among 67 individuals at high risk for HIV-1 infection and no seroconversions among 202 individuals at relatively low risk for HIV-1 infection. This study demonstrates the importance of evaluating commercial ELISAs with sera from appropriate geographical regions in order to select the most cost-effective and practical assay for use in that region. Furthermore, the high frequency of indeterminate Western blots for African sera emphasizes the continual need for improved confirmatory assays and interpretation criteria.

HIV types and testing

The past year has seen the discovery of new isolates which do not readily fit into the established categories HIV-1, HIV-2 and SIV, as well as the availability of new assays including the use of the polymerase chain reaction. New combination enzyme-linked immunosorbent assays can detect viruses from two or more groups where specific enzyme-linked immunosorbent assays have been developed using peptides and monoclonal antibodies.

The polymerase chain reaction: a new tool for the understanding and diagnosis of HIV-1 infection at the molecular level

The polymerase chain reaction (PCR) is at present the most powerful analytical tool for detection of specific nucleic acid sequences. The method is based on the in vitro amplification of DNA segments before detection with conventional hybridization techniques or visualization following electrophoresis and staining. The current diagnostic methods for HIV-1 do not allow easy identification of subgroups of infected patients including infants born to seropositive mothers, individuals with delayed serological responses to the virus, infected patients with indeterminate serology results, and patients with dual retroviral infections. Furthermore, response to antiviral therapy cannot be evaluated with serological assays. The rationale for applying PCR in those situations is elaborated here. The applications of this technique for HIV-1 as a diagnostic test and for the understanding of the pathogenesis of this retrovirus are described. Potential limitations of this technique for diagnostic purposes include mainly the possibility of false-positive results due to contamination and false-negative reactions caused by Taq polymerase inhibition. Non-isotopic means for detection of amplified products have been described and should allow for a wider application of this technology. Modifications of PCR which make use of internal standards seem promising for quantitative analysis of nucleic acids. PCR has great potential for viral diagnosis but still requires further studies and better characterization.

Enhanced detection of HIV-1 sequences using polymerase chain reaction and a liquid hybridization technique. Application for individuals with questionable HIV-1 infection

In this report we describe a sensitive HIV-1 detection method which is applicable for confirmation testing of donors whose blood sample gives indeterminate viral-serology results. The method involves performing a polymerase chain reaction (PCR) and detecting the generated fragments using liquid hybridization and gel retardation. We found that it is as specific as blotting on a filter and hybridization with an internal probe but at least tenfold more sensitive. After applying it on DNA samples of a panel of 11 persistent indeterminate anti-p24gag-reactive donors, none was found to be PCR positive. Considering other negative virological and biochemical test results and case-historical data, these donors are not likely to be HIV-1 infected.

Evaluation of screened blood donations for human immunodeficiency virus type 1 infection by culture and DNA amplification of pooled cells

BACKGROUND

Reports of transmission of the human immunodeficiency virus type 1 (HIV-1) from transfusions of screened blood and reports of silent, antibody-negative HIV-1 infections in persons at high risk continue to foster concern about the safety of the blood supply. Previous estimates of the risk of HIV-1 range from 1 in 38,000 to 1 in 300,000 per unit of blood but are based on either epidemiologic models or the demonstration of seroconversion in recipients.

METHODS

We isolated peripheral-blood mononuclear cells from blood that was fully screened and found to be seronegative, combined them into pools of cells from 50 donors, and tested them for HIV-1 by viral culture and the polymerase chain reaction, using protocols specifically adapted for this analysis.

RESULTS

The 1530 pools of mononuclear cells were prepared from 76,500 blood donations made in San Francisco between November 1987 and December 1989. Of these pools, 1436 (representing 71,800 donations) were cultured successfully; 873 (43,650 donations) were evaluated by the polymerase chain reaction. Only one pool was confirmed as HIV-1--infected by both methods. After adjustment for sample-based estimates of the sensitivity of the detection systems using culture and the polymerase chain reaction, the probability that a screened donor will be positive for HIV-1 was estimated as 1 in 61,171 (95 percent upper confidence bound, 1 in 10,695).

CONCLUSIONS

Silent HIV-1 infections are exceedingly rare among screened blood donors, so the current risk of HIV-1 transmission from blood transfusions, even in high-prevalence metropolitan areas, is extremely low.

Human immunodeficiency virus-1 infection in an infertile population

OBJECTIVE

The aim of our study was to determine the prevalence of human immunodeficiency virus-1 (HIV-1) in an infertile population.

DESIGN

The study design included a retrospective anonymous survey of clinical data and screening for HIV-1 antibody by enzyme-linked immunoabsorbent assay (ELISA) in stored sera. Samples that were ELISA-positive were further tested by Western blot assay. Frequency distributions were analyzed by Fisher's exact test.

SETTING

University tertiary care center.

PARTICIPANTS

Based on availability of stored frozen sera, the total study population included 182 of 304 consecutively registered infertile couples.

RESULTS

Seventy-five percent of the study population were found to have one or more risk factors for HIV infection. Of the 252 sera tested, 10 were repeatedly reactive by ELISA, and Western blot testing confirmed HIV-1 infection in one woman and two men.

CONCLUSIONS

This relatively high HIV-1 seroprevalence (male: 2.6%; female: 0.6%) in a low-middle class infertile population emphasizes the urgent need to implement on-site HIV-infection counseling aimed at preventing the spread of disease to the healthy partner and fetus and to discuss therapeutic and reproductive options.

Immune response to a major epitope of p24 during infection with human immunodeficiency virus type 1 and implications for diagnosis and prognosis

A sequential inhibition enzyme-linked immunoassay (SIEIA) using a peroxidase-conjugated monoclonal antibody reacting to the sequence AAEWDRVHP of p24HIV-1 (amino acids 209 to 217 of p55) was developed in order to detect and determine the titer of antibody to this epitope in various populations of human immunodeficiency virus type 1 (HIV-1)-positive patients. There was a good correlation between SIEIA and a commercially available competition assay that uses recombinant p24 protein and polyclonal antibody to HIV-1 antigen, demonstrating the importance of the described epitope. Analysis of sera from French patients showed a decline of antibody to the AAEWDRVHP sequence associated with the progression of AIDS. No decrease was observed with serum samples from African patients. An immune response to the epitope was detected by SIEIA early in the course of seroconversion. Although our SIEIA uses a single p24 epitope, these data are in accordance with previously published studies in which antibodies to the whole p24 were analyzed. Sera reacting to p24 only (indeterminate profiles by Western blot [immunoblot]) did not bind to AAEWDRVHP. This epitope, which is conserved between HIV-1 and HIV-2/simian immunodeficiency virus, appears to be a major antigenic domain of p24. The area containing the sequence AAEWDRVHP and the corresponding monoclonal antibody may serve as a convenient alternative to whole purified p24 and polyclonal antibody in diagnostic and prognostic assays.

Characterization of serum antibody responses to recombinant HIV-1 gp160 vaccine by enzyme immunoassay. NIAID AIDS Vaccine Clinical Trials Network

An enzyme immunoassay (EIA) was developed to measure serum antibody responses of healthy adult volunteers vaccinated with 40 or 80 micrograms of human immunodeficiency virus type 1 (HIV-1) recombinant gp160 (rgp160) vaccine at 0, 1, 6, and 18 months. This assay, which used purified rgp160 as antigen, was compared with the Biotech/Du Pont HIV-1 Western blot and the Abbott HIV-1 EIA. Of 33 volunteers who received three doses of rgp160 vaccine, seroresponses were detected in 91% by rgp160 EIA, 97% by Western blot, and 30% by HIV-1 EIA. The level of IgG rgp160 EIA antibody (mainly IgG1) peaked after the third immunization; 64% of 33 vaccinees still had detectable antibody by 12 months. The fourth immunization induced anamnestic IgG EIA antibody in 23 of 24 vaccinees, with titers ranging from 1:200 to 1:25,600. Neutralizing antibody was not detected in postvaccination sera by microtiter syncytium formation inhibition assay. Additional testing of sera by EIA indicated that the immune response to the vaccine was directed toward epitopes on both gp120 and gp41. Seroresponses to the immunodominant epitopes on gp41 were infrequent and none were detected to the neutralization epitope in the V3 region of gp120. This highly sensitive EIA is useful for characterizing HIV-1-specific antibody responses induced by an HIV-1 gp160 subunit vaccine.

Comparison of false-positive reactions in direct-binding anti-HIV ELISA using cell lysate or recombinant antigens

In a 2-year study of false-positive anti-HIV-1 tests in blood donors at Manchester and Lancaster Blood Banks, the reactions associated with a HIV-infected cell lysate antigen were compared with those using recombinant-antigen-based tests. In year 1 (cell lysate test) at Manchester BTS 0.21% of 119.178 donations were repeatedly reactive, compared with 0.53% of 119,004 donations in year 2 (recombinant antigen). Reactive sera were tested at Manchester PHL by three different immunoassays. Referred specimens were classified as anti-HIV positive (95-100% reactive in all the assays), equivocal or negative (negative results in all three immunoassays). Two donors were confirmed to be anti-HIV positive over the 2-year period. Most sera were negative by confirmatory immunoassays in years 1 and 2. In year 1, a study of 60 referred sera with sex- and age-matched controls showed high correlation between a reactive anti-HIV-1 screening test and indeterminate anti-HIV-1 patterns on Western blot showing reactions with HIV gag-coded proteins. In year 2, less than 10% of referred sera were reactive by Western blot, and there was no correlation between a reactive screening anti-HIV test, the strength of signal in the test or a reactive Western blot. Follow-up showed that donors whose sera were reactive in years 1 and 2 by the anti-HIV-1 screening test formed almost two different populations. Four donors with equivocal anti-HIV-1 confirmatory tests had anti-HIV 'envelope' reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Current status of clinical laboratory tests for the human immunodeficiency virus

The predictive values of positive and negative test results for human immunodeficiency virus (HIV) antibody are extremely high in laboratories that have good quality control and high performance standards and use licensed FDA-approved enzyme immunoassay (EIA) and Western blot standardized tests. With a carefully designed protocol, the false-positive rate of combined EIA and Western blot has been reported to be as low as 1 in 10(5). When results of HIV confirmatory antibody tests are indeterminate, other tests such as culture and nucleotide probe methods for HIV DNA or RNA may help resolve false-reactive screening EIA tests. Improvements are constantly in progress for HIV laboratory tests with the use of recombinant DNA-derived antigens and synthetic polypeptides. With the use of new-generation synthetic polypeptide antigens, specific assays to identify HIV-1 and HIV-2 have been developed. Recently, assays for the HIV regulatory gene products have been studied for their predictive potential. Antibodies to nef protein, a regulator of HIV-1 replication, may be an early indicator of HIV infection.