Blood donor sera with false-positive Western blot reactions to human immunodeficiency virus

Antibodies to the HIV-1 p17 protein cross-react with human superoxide dismutase-2

Antibodies reacting with the gag protein p17 of the human immunodeficiency virus type 1 (HIV-1) can occasionally be found in the serum of non-HIV-1-infected individuals. Conversely, anti-p17 antibodies can also react with human tissues from non-infected individuals. Here we report on the isolation from human liver of a molecule that is immunoreactive with anti-p17 antibodies. This molecule was purified to homogeneity and identified as superoxide dismutase-2 (manganese type SOD). Both human SOD-2 and HIV-1 p17 contain the LQPALK hexapeptide which may serve as a common antigenic determinant. This study indicates that human SOD-2 is a target for anti-p17 antibodies and suggests that HIV-1-negative individuals may possess SOD-2 auto-antibodies that cross-react with HIV-1 p17.

The HIV/AIDS epidemic: its evolutionary implications for human ecology with special reference to the immune system

The epidemiology of AIDS in Africa is discussed. Serological and clinical data on virology and population genetics are related to current theories of heterosexual transmission and to cultural practices involving the exchange or transmission of body fluids between individuals, such as female and male genital mutilation and indigenous or 'folk' medicine, as well as non-Western medical uses of medical syringes. A review of the relationship of autoimmune conditions, graft-vs-host disease and the retrovirus/oncogene involvement is presented. These data place in a new perspective concepts of widespread heterosexual infection and transmission of HIVs as well as their relation to AIDS in the context of the evolution of the human immune system.

False-positive human immunodeficiency virus testing in patients with lupus erythematosus

Testing for human immunodeficiency virus (HIV) infection in patients with systemic lupus erythematosus (SLE) leads to a higher than expected rate of positive ELISA results and indeterminate Western blot results. Because most of these patients lack any risk factors for HIV infection and the coexistence of SLE and HIV infection is extremely rare, most of these results represent false-positives. Two cases of false-positive HIV tests are reported and the related literature is reviewed. Further, Celum's algorithm for evaluating indeterminate HIV Western blot tests, which is especially valuable in lupus patients, is discussed.

Evaluation of a rapid membrane enzyme immunoassay (Testpack HIV-1/HIV-2) at zonal, regional and district hospital laboratories in Tanzania

The performance of a rapid and simple membrane enzyme immunoassay for antibodies to HIV-1 and HIV-2 (Testpack HIV-1/HIV-2) was evaluated by testing 1000 sera from the Kilimanjaro region of Tanzania. A sensitivity of 100% (118/118 positives) and specificity of 95.1% were obtained following the manufacturer's procedure. The specificity was significantly enhanced to 97.2% (P = 0.026) by modifying the Testpack procedure by including an extra was after serum adsorption to the unit membrane. The testing of a single specimen could be completed in 8 min and up to 10 individual tests could be run simultaneously. There was complete agreement in interpretation when the results were read independently by two trained technicians. A built-in control insured against incorrect procedures or inactive reagents. In a subsequent field trial including 450 sera, one strongly reactive sample failed to be detected at a participating field hospital for unknown reasons. The Testpack reagents proved stable for up to one year at room temperature (25-30 degrees C). The data indicate that Testpack is suitable for the detection of serum antibodies to HIV and is especially applicable in laboratories with limited facilities. When used to test African sera which are known to produce a high degree of false positivity, an extra wash of the membrane after serum adsorption is recommended.

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.

Seroreactivity to human T cell leukemia/lymphoma virus type 1 and related retroviruses in multiple sclerosis patients from Denmark and the Faroes

A total of 40 multiple sclerosis (MS) patients from Denmark and 10 from the Faroes were examined for antibodies with affinity to human T cell leukemia/lymphoma virus type 1 (HTLV-I) and human immunodeficiency virus type 1 and 2 (HIV-1 and HIV-2). Using ELISA, MS patients and a group of healthy controls did not differ significantly in their reactivities to HTLV-I. However, elevated reactivities were recorded with 5 MS sera, whereas only 2 of the sera from the controls produced highly values. Ten patients with other neurological diseases all seemed to exhibit low reactivity in HTLV-I ELISA. The reactivities of 2 MS sera decreased considerably by absorption with an HTLV-I lysate. In immunofluorescence assay, two other MS sera reacted with HTLV-I transformed cell lines as well as with non-infected cells. Examined by Western blotting (WB), a single MS serum produced a distinct HTLV-I p19 band. With ELISA for detection of HIV-1 and HIV-2 antibodies, 2 MS sera exhibited borderline reactions. Further examination of these two sera by WB revealed weak reactivities against p24 and p53 of HIV-1. One the whole, the present observations do not suggest that a putative MS retrovirus would be closely related with HTLV-I, HIV-1 or HIV-2.

Fine specificity of the B-cell epitopes recognized in HIV-1 NEF by human sera

We have previously used partially overlapping synthetic nonapeptides to characterize the human natural antibody response against HIV-1 negative regulatory factor (NEF), and identified nine 5 to 13 amino acid long regions that were recognized by sera of HIV-1-infected individuals. In this report we define the minimal size of these epitopes with the use of shorter, from 3 to 8 amino acid long partially overlapping peptides covering the complete sequence of the previously identified reacting regions and the N- and C-terminal flanking sequences. We also introduce a new method for the analysis of the reactivities obtained with peptides of different lengths. In six of the antigenic regions the epitopes were found to be noncontiguous and to consist of multiple, down to three amino acid long separate reactive stretches (epitope 1: WSK, VGW, TVRERMRR; epitope 3A: PLRPM, SHFLK; epitope 3B: SQRRQD, DLW; epitope 3C: IYHT, QGYFPDWQN; epitope 4: SLL, VSL; epitope 5: EVLEWRFDSR, VAR). Three epitopes were clearly linear (epitope 2: CAWLE; epitope 3D: LTFGWC; epitope 6: PEYF). Interestingly, five of the minimized B-cell epitopes (1, 3A, 3C, 3D, 5) recognized by human sera overlap totally or partly with the previously identified T-cell epitopes in HIV-1 NEF. Also, only three of the epitopes (3C, 3D, 5) were in a computer-based homology search shown to contain strictly NEF-specific sequences.

Evaluation of the Genetic Systems Corp. Integra HIV-1 Pageblot system

The Genetic Systems Corp. Integra HIV-1 Pageblot system was evaluated as a supplementary assay to confirm the presence of antibodies to human immunodeficiency virus type 1 in 57 specimens from individuals at high risk of infection with the virus. Forty-one specimens identified as reactive in the Genetic Systems Integra HIV-1 Pageblot system were likewise identified as reactive in a U.S. Food and Drug Administration-licensed (Biotech/Dupont) Western blot (immunoblot). Six specimens identified as indeterminate in either or both immunoblot assays were all identified as nonreactive in a U.S. Food and Drug Administration-licensed enzyme immunoassay with recombinant antigens.

Advantages of a human immunodeficiency virus type 1 (HIV-1) persistently infected HeLa T4+ cell line for HIV-1 indirect immunofluorescence serology

A HeLa T4+ cell line persistently infected with human immunodeficiency virus type 1 (HIV-1) was used in an indirect immunofluorescent antibody assay (IFA) system to explore its potential suitability as an alternative source of viral antigen for confirmatory IFA in HIV serology. In a study of 121 serum samples chosen because they were reactive on repeat examination by enzyme immunoassay but nonspecific by IFA by using HIV-1-infected H9 cells (H9 IFA) or gave discrepant results by enzyme immunoassay and H9 IFA, the specificity and sensitivity of the HeLa T4+ IFA were comparable to those of Western blot (immunoblot), and identification of the true positive samples among these discrepant or nonspecific samples by HeLa T4+ IFA was approximately twice that by H9 IFA. The primary advantages of using the HeLa cell line rather than lymphoid cell lines in IFA are that cells can be grown as a monolayer and that the individual cells are much larger. The cell membrane, cytoplasm, and nucleus are easily discernible; this allows specific and nonspecific staining to be distinguished. At least eight different nonspecific nuclear and cytoplasmic staining patterns were identified in this study by using T4+ cells.

What to do when results of a western blot test are indeterminate

The role of primary care physicians in diagnosis of human immunodeficiency virus (HIV) infection is becoming increasingly important. Given the development of antiretroviral therapy, which can delay the clinical progression of asymptomatic HIV infection, early and accurate identification is invaluable to these patients. Screening begins with the enzyme immunoassay, which, although highly sensitive, lacks specificity. Therefore, the Western blot test should always be used for confirmation. When results of the Western blot test are indeterminate, reassessment for risk factors for HIV infection should be followed by serial Western blot testing and HIV culture or polymerase chain reaction testing.

Laboratory diagnosis of HIV infection

Laboratory diagnosis of human immunodeficiency virus (HIV) infection is complicated by absence of data on sensitivity, specificity and predictive value of the various tests as they apply to children. The presence of maternal anti-HIV passively transmitted across the placenta also confounds diagnosis. The authors review currently available data on the detection of HIV, HIV genome, and HIV gene products, as well as the diagnostic value of detecting serologic and cellular responses to HIV in infants and children.

Identification of regions of HIV-1 p24 reactive with sera which give "indeterminate" results in electrophoretic immunoblots with the help of long synthetic peptides

We analyzed nine sera from persons unlikely to be HIV infected which had an IgG reactivity directed against HIV-1 p24, and in two cases also to its precursor p55, but to no other HIV proteins, nor to proteins of the H9 host cell, in electrophoretic immunoblots (EIB). These sera are also referred to as having an indeterminate HIV EIB pattern or as HIV antibody false positive sera. Seven of nine sera reacted with longer (61-77 amino acids) and none with shorter (17-25 amino acids) p24-derived peptides in enzyme immunoassays (EIAs). This is compatible with a conformational (discontinuous) nature of the epitopes involved in many false positive HIV-1 p24 antibody reactions. Four sera reacted with an N-terminal, one with an internal, and two with a C-terminal fragment. Each of the seven sera thus only reacted with one of the long p24 peptides. The specificity and singularity of the reaction was further demonstrated by competition and/or absorption experiments with synthetic peptides. In contrast, 18 of 20 confirmed HIV-1+ sera with p24 reactivity in EIB reacted with at least one and often several of the longer peptides, most frequently the C-terminal one. Thus, the distribution of peptide reactivity of true HIV-1 antibody-positive sera was different from that of the falsely reactive sera. According to two of several explanations, these antibodies may have arisen because of (1) molecular mimicry by chance or by functional selection, (2) immunization by activation, noninfectious exposure, or infection involving non-HIV endogenous or exogenous retroviral antigens. The latter gains some support from our finding of antibody reactions with capsid proteins of the simian viruses, simian sarcoma-associated virus (SSAV), and Mason-Pfizer monkey retrovirus in some of the p24 +/- p55 reactive sera.

Protein blotting: ten years on

Protein blotting was originally described in 1979 as an outgrowth of nucleic acid techniques, and received its commonly used designation of 'Western' blotting in 1981. The use of the technique to render electrophoresed proteins accessible for further analysis has found many roles, the most prominent being subsequent reaction with antibodies or antisera, which has many clinical and research applications. Since the initial development of the system there have been many changes to the techniques involved, but the basic principles remain unaltered. This review discusses these changes, and also provides a summary of current techniques.

New sensitive and specific assay for human immunodeficiency virus antibodies using labeled recombinant fusion protein and time-resolved fluoroimmunoassay

A new, rapid method for the detection of human immunodeficiency virus type 1 (HIV-1) antibody by time-resolved fluoroimmunoassay (TR-FIA) was developed. In this assay format, microtitration strips were coated with a recombinant fusion protein, and the same protein was labeled with europium and added into the wells simultaneously with the test specimens. The recombinant fusion protein contained the HIV-1 p24 gag protein sequence that carried an insertion, near the carboxyl terminus, of a 23-amino-acid sequence from a highly conserved region of the HIV-1 gp41 envelope protein. This recombinant antigen enabled the detection of antibodies to both gag and env gene products. When this assay was compared with a commercially available recombinant enzyme-linked immunoabsorbent assay (ELISA) by using four quality-control panels, the TR-FIA detected all 20 positive specimens, while the recombinant ELISA detected only 16 of them. This increased sensitivity could be demonstrated directly by the assay of dilution series of HIV-1-positive sera. The analysis of two seroconversion panels by TR-FIA and six ELISAs showed that TR-FIA allowed detection of antibody in infected individuals 16 days earlier than the other assays did. In addition to being highly sensitive, the assay was highly specific; of the 57 samples shown to be repeatedly positive by ELISA but known to be HIV-1 negative by Western immunoblot analysis, only 1 sample reacted positively in this assay. The specificity of the assay was 99.9% when 1.054 random serum specimens were tested.

Antigenic epitopes of NEF proteins from different HIV-1 strains as recognized by sera from patients with manifest and latent HIV infection

Human immunodeficiency virus (HIV) infection that generally causes a strong antibody response toward HIV may sometimes occur in a latent form, characterized by seronegativity in assays based on structural HIV proteins. Latently infected individuals, however, often have an antibody response against the nonstructural regulatory HIV-1 protein NEF, a factor implicated in down-regulation of viral expression. In order to define the specificity of NEF antibodies, we looked for antibody response against more than 600 overlapping nonapeptides representing the total NEF sequence of three different HIV-1 isolates BRU, SF2, and MAL. Nine distinct homologous antigenic epitopes were recognized by sera from seropositive HIV-1-infected individuals by the peptide ELISA. We further demonstrated that sera from "at risk" individuals, with no antibodies to HIV structural proteins but reacting with the recombinant NEF protein in Western blot, recognize the same epitopes. Immunological assays based on the defined NEF epitopes can therefore be used to diagnose early or latent HIV Infection.

An analysis of indeterminate western blot patterns of black African subjects

The significance of indeterminate Western blotting results was assessed by determining their distribution in attenders of sexually transmitted diseases (STD) and family planning (FP) clinics. As expected, it was found that the former had a highly significantly greater prevalence of HIV infection. Indeterminate results were not found more frequently in STD attenders refuting any association with sexual promiscuity. They were, however, found significantly more frequently amongst black compared to white subjects, but no difference was found between males and females. Indeterminate results appear to be a feature of black African sera and what the significance is, still remains to be elucidated.

Characteristics of a population volunteering for human immunodeficiency virus immunization. NIAID AIDS Clinical Trials Network

A total of 166 volunteers for an AIDS vaccine study (Vaxsyn, baculovirus produced recombinant GP160; MicroGeneSys Inc, West Haven, Connecticut, USA) were interviewed and examined. Blood was collected for routine laboratory testing as well as T-cell counts, HIV ELISA (EIA), Western blot (WB) and p24 Ag. Eighty-five men (mean age 22.2 years, range 18-42) and 81 women (mean age 23.9 years, range 17-50) volunteered; 130/166 (78%) were university students. Most had learned of the study from news media (55%), friends or workplace (37%). The most common causes for exclusion were the presence of indeterminate WB (26.5%) or a change of mind after the initial interview (24%). Other causes were abnormal cell count and differential (7.2%), elevated alanine aminotransferase (3.6%), positive hepatitis B antibody (3.6%), abnormal urinalysis (3.4%), recent venereal disease (3.0%), T4 cell count less than 400 (1.9%), abnormal chest X-ray (1.7%), recognized high-risk behaviour (1.7%), multiple sex partners (1.2%), positive rapid plasma reagin test (1.2%), failure to meet age criteria (1.2%), unable to be available for entire study (1.2%), abnormal physical examination (0.6%) and positive p24 Ag (0.6%). No volunteers had positive EIA, but 14.5% had more than one reason for exclusion. Even in a community with low prevalence for HIV, a large majority of healthy heterosexual volunteers can be expected to be ineligible for enrollment in HIV vaccine trials. An average of 4.8 volunteers were screened for each of 12 vaccinees chosen.

Performance of six different commercial assays to demonstrate antibodies to HIV-2 among immigrants from high-endemic areas

Four HIV-2 and 8 HIV-1 infections were detected when serum specimens from 422 persons from high-endemic areas were examined with 6 different commercial ELISA tests. 41 specimens showed a positive result in at least one of the assays. 12 of these were confirmed as anti-HIV positive. One of the anti-HIV-2 specimens was negative in the Abbott recombinant HIV-1 test but positive in the ELAVIA II and the 4 HIV-1/HIV-2 combination tests. The 4 HIV-2 positive individuals originated from West Africa.

HIV-1 antibody testing strategy: evaluation of ELISA screening and western blot profiles in a mixed low risk/high risk patient population

The Westmead HIV-1 antibody testing strategy showed that, regardless of ELISA screening kit manufacturer, sera which were repeatedly positive by two ELISA screening assays (one indirect and the other competitive format) had a 97-98% chance of being confirmed positive by Western blot for HIV-1 antibody or a less than 3% chance of either being identified as a seroconverter (1%) or a late stage AIDS patient (1.2%). Sera which were discordant by two ELISA screening assays had a less than 4% chance of either being confirmed positive by Western blot (2.5%) or identified as a seroconverter (1.3%). The incidence of non-specific indeterminate Western blot profiles were shown to be inversely proportional to the specificity of the ELISA screening kits used. The use of a recombinant envelope ELISA was able to confirm the viral specificity of HIV-1 envelope bands (gp160, 120 or 41) on Western blot. Guidelines suggested by the Australian National HIV Reference Laboratory, Fairfield Hospital, Melbourne, which categorized indeterminate or typical Western blot profiles into four reaction groups were found to be useful for the interpretation of Western blot patterns. A Western blot profile which is reactive for HIV-1 viral glycoproteins (gp160, 120 and 41) alone or in combination with not more than two other viral proteins (Indeterminate Group 4) and which is confirmed viral envelope specific by a recombinant envelope ELISA can be used as a predictor of seroconversion.

Low-titer antibodies reactive with HTLV-I gag p19 in patients with chronic myeloneuropathy

To elucidate the possible association of human T-lymphotropic virus type I (HTLV-I) and chronic neurological diseases, 156 serum samples from patients with various neurological diseases, including multiple sclerosis, chronic progressive myelopathy, chronic inflammatory polyradiculoneuropathy, myasthenia gravis, polymyositis, motor neuron disease, and tension headache, and healthy control subjects were examined for IgG antibodies to HTLV-I by three independent techniques--gelatin particle agglutination test, enzyme-linked immunosorbent assay, and Western blot assay. Specificity of antibodies was assessed by homologous competitive inhibition on Western blot assay. Six patients (3 with chronic progressive myelopathy, 1 with chronic inflammatory polyradiculoneuropathy, 1 with motor neuron disease, and 1 with tension headache) had high-titer HTLV-I antibodies. Twelve patients (5 with multiple sclerosis, 1 with chronic progressive myelopathy, 2 with chronic inflammatory polyradiculoneuropathy, 2 with myasthenia gravis, and 2 with motor neuron disease) had low-titer HTLV-I antibodies that reacted with a single gag protein, p19 or p24, on Western blot assay. In 4 (2 with multiple sclerosis, 1 with chronic progressive myelopathy, and 1 with chronic inflammatory polyradiculoneuropathy) of these 12, the antibodies that were all directed to p19 were determined to be specific by homologous competitive inhibition. In the remaining 8 patients (3 with multiple sclerosis, 1 with chronic inflammatory polyradiculoneuropathy, 2 with myasthenia gravis, and 2 with motor neuron disease), restricted reactions against p19 or p24 were considered to be nonspecific because they were not inhibited by homologous competitive inhibition. The results suggest that in some patients chronic myeloneuropathy diagnosed as chronic progressive multiple sclerosis, chronic progressive myelopathy, and chronic inflammatory polyradiculoneuropathy may be associated with HTLV-I or related retroviruses.

Antigen-antibody reaction in solution in capture competition immunoassay for human immunodeficiency virus antibodies

In the capture competition immunoassay, undiluted serum was reacted in solution with purified human immunodeficiency virus (HIV) antigen in wells of microtest plates coated with anti-HIV immunoglobulin G antibodies (HIV capture antibodies). HIV antibodies present in the serum being tested combined with the HIV antigen and thus blocked (completely or partially) the fixation of the antigen to the capture layer. Unblocked antigenic activity was measured in subsequent steps by the use of biotinylated anti-HIV immunoglobulin G and peroxidase-conjugated avidin. The assay was evaluated in comparison with indirect enzyme-linked immunosorbent assay and Western (immuno-) blot (WB). A total of 180 serum samples which reacted repeatedly as positive in indirect enzyme-linked immunosorbent assay but negative in WB were found to be negative by the capture competition assay. Of 54 serum samples showing dubious reactions (single p24 bands in WB), 53 were clearly separated into positive or negative reactions, whereas 1 serum sample gave a borderline reaction. It was concluded that a characteristic feature of this kind of inhibition assay is a very low frequency of equivocal results.

Agreement study between two laboratories of immunofluorescence as a confirmatory test for human immunodeficiency virus type 1 antibody screening

A total of 114 serum specimens from 76 blood donors, 21 patients with acquired immune deficiency syndrome or acquired immune deficiency syndrome-related complex, 7 multiply transfused patients, 3 hemophiliacs, and 7 others were tested for anti-human immunodeficiency virus type 1 (HIV-1) antibody by enzyme immunoassay (EIA) and Western blot (WB) and then blindly tested by immunofluorescence (IF), independently, in two separate laboratories. The IF technique used acetone-fixed HIV-1-infected E cells and uninfected HUT-78 cells mixed at a 1:3 ratio in one spot on a glass slide and uninfected HUT-78 cells (to assess nonspecific fluorescence) alone in a second spot. Of 114 serum specimens, 85 were repeat EIA positive, and 21 of these were WB positive. A total of 129 of 134 of the IF results (included were 20 duplicates) were identical between laboratories, for a Kappa agreement statistic of 0.93. All five IF results discordant between laboratories were EIA repeat positive and WB negative. Included in the study were eight WB-indeterminate sera, of which five blood donor serum specimens and one hemophiliac serum specimen were IF negative and two acquired immune deficiency syndrome serum specimens were IF positive. As a confirmatory test for HIV-1 antibodies, IF provided a faster alternative or supplementary test for confirming EIA results.

Reliable confirmation of antibodies to human immunodeficiency virus type 1 (HIV-1) with an enzyme-linked immunoassay using recombinant antigens derived from the HIV-1 gag, pol, and env genes

An enzyme-linked immunoassay (ELISA) using six recombinant proteins corresponding to large segments of the human immunodeficiency virus type 1 (HIV-1) gag, pol, and env gene products (HIVAGEN; SmithKline Bio-Science Laboratories, Van Nuys, Calif.) was developed to confirm the presence of antibodies to HIV-1 in sera reactive in the whole-cell-derived virion screening ELISAs. Serum samples for testing were obtained from healthy seronegative blood donors and from the different categories of HIV-infected individuals (asymptomatic, acquired immunodeficiency syndrome [AIDS]-related complex, and AIDS). A positive reaction was defined as reactivity against an env and at least one other (either gag or pol) HIV-1 gene product; negative was defined as no reaction with any antigen; and indeterminate was defined as reactivity with gag or pol (or both) or with env alone. None of the 1,180 serum samples from healthy seronegative blood donors gave a positive result, and only 49 of these samples (4%) gave indeterminate results. The recombinant HIV-1 antigen ELISA panel identified seropositive individuals with a high degree of accuracy, as a positive reaction was seen with 99.3% of asymptomatic healthy seropositive individuals, 98.1% of patients with AIDS-related complex, and 90.4% of patients with AIDS. None of the 725 HIV-1-seropositive subjects had a negative test result. Reactivity with the Kp41 antigen, corresponding to an amino-terminal portion of the gp41 envelope glycoprotein, by itself demonstrated 100% sensitivity and specificity in distinguishing seronegative from seropositive sera. A subset of seronegative and seropositive samples were tested both with the recombinant HIV-1 antigen ELISA panel and by Western blot (Du Pont Co.). The recombinant HIV-1 antigen ELISA panel accurately identified more seropositive and seronegative samples and had fewer indeterminate results than did Western blot (interpreted by Du Pont criteria).

Blood donors with indeterminate anti-p24gag reactivity in HIV-1 western blot: absence of infectivity to transfused patients and in virus culture

During a follow-up period of 23-40 months, 7 regular blood donors had persistently, and 4 had intermittently indeterminate anti-p24gag reactivity in human immunodeficiency virus (HIV)-1 Western Blot. Serological testing and viral cultures revealed that these donors had no signs of infection for HIV-1, HIV-2, human T-cell lymphotropic virus (HTLV)-4, and HTLV-1. Extensive interviewing and physical examination of these donors revealed neither risk factors, nor signs of HIV infection in the tested donors. Ten recipients, who were transfused with blood products from 6 of these 11 anti-p24gag-positive donors, were traced back. Six months after transfusion, no serological or clinical signs of HIV-1, HIV-2, or HTLV-1 infection were observed in these patients. It is concluded that blood donors with persistent or intermittent anti-p24gag reactivity in HIV-1 Western Blot, without development of antibodies to other HIV-encoded proteins in later blood samples, do not transmit the described retroviruses to transfused patients.

Screening of African sera stored for more than 17 years for HIV antibodies by site-directed serology

Antibodies to Human Immunodeficiency Virus type 1 (HIV-1) and type 2 (HIV-2) were investigated, using site-directed enzyme immunoassay (ELISA), in 320 specimens obtained from three remote, African tribes during 1969-1971. Using HIV-1 E34/E32 ELISA and HIV-2 149 ELISA, assay were conducted on 101 serum specimens from the Korekore tribe of Zimbabwe, 93 specimens from the Mano tribe of Liberia, and 126 specimens from the Turkana tribe of Kenya; specimens which tested positive in ELISA were further tested by radioimmunoprecipitation assay (RIPA) and Western blot (WB). Two serum specimens from the Mano tribe of Liberia gave OD 492 nm values greater than 0.2 in HIV E34/E32 ELISA in all three runs. These two specimens reacted with HIV-1 envelope proteins gp160 and gp120 and the internal protein p24 in RIPA and WB; however, the reactivity was uncostant. All other serum specimens were negative for HIV-1 and HIV-2 antibodies. Site directed ELISA serology for HIV-1 and HIV-2 gave very low rates of false positive reactivity. Thus, reaction with HIV-1 antigen was identified in two persons of one tribe in Liberia in 1971, but HIV-2 antibodies were not detected in this tribe; HIV-1 and HIV-2 antibodies were absent during the late 1960's and early 1970's from two African tribes resident in Zimbabwe and Kenya.

HIV-2 antibody testing of blood donors with doubtful immunoblot results for HIV-1

Antibodies against human immunodeficiency virus type-1 (HIV-1) in samples from blood donors are commonly detected by various enzyme-linked immunosorbent assays (ELISA) and by confirmatory tests, e.g., "Western blot" or immunofluorescence tests. Immunoblot reactivity, which is directed only towards the HIV-1 core proteins p 18, p 24 and p 55, may represent false-positive reactions. Out of 125,000 blood donations, 140 were repeatably HIV-1 antibody reactive by ELISA; of these, 20 were doubtful positive sera with isolated p 18 and/or p 24 bands in the HIV-1 confirmatory assay. Antibodies to HIV-2 are known to cross-react with these HIV-1 core proteins. We therefore assayed the 20 sera by immunofluorescence and immunoblotting for the presence of antibodies to HIV-2. None of these doubtful HIV-1 antibody positive blood donor sera was found to have antibodies to HIV-2.

Serological markers of primary HIV infection

39 persons with an incidentally discovered seroconversion from HIV antibody negative (Ab-) to antibody positive (Ab+) state as measured by an enzyme-linked immunosorbent assay (ELISA) were investigated for the presence of (1) HIV antigen (Ag) and (2) immunoblotting test (IBT) Ab in serum samples collected within the year before seroconversion. 13 (33%) of the patients were HIV Ag+ at some time before seroconversion. However, the collection of samples was not done systematically and the samples from patients who had at least 1 sample collected within 3 months before seroconversion were thus compiled separately. This group consisted of 58 samples from 19 patients and among these none were HIV Ag+ earlier than 11 weeks before seroconversion, but the prevalence of HIV Ag+ samples was rising towards seroconversion and 10 patients (53%, 95% confidence limits: 29-76%) became HIV Ag+ in this 11-week period. Further, among all patients 13 (33%) were IBT Ab+ 4-50 days (median: 14 days) before seroconversion. Finally, among 18 patients with signs and symptoms consistent with an acute HIV infection 10 were HIV Ag+, as opposed to 4 HIV Ag+ patients among 21 without symptoms (p = 0.041).

Passive hemagglutination test for detection of antibodies to human immunodeficiency virus type 1 and comparison of the test with enzyme-linked immunosorbent assay and Western blot (immunoblot) analysis

A passive hemagglutination test (PHA) was developed for detecting antibodies to human immunodeficiency virus type 1 (HIV-1) utilizing sheep erythrocytes cross-linked with purified envelope glycoprotein (gp160) of HIV-1. In an analysis of 216 human serum samples, 100% correlation was observed in 86 reactive and 124 nonreactive serum samples between PHA and commercial enzyme-linked immunosorbent assays and Western blot (immunoblot) analysis. Serum samples from gp160-immunized chimpanzees also reacted equally well in PHA. The test is simple, rapid, and inexpensive, thus providing an alternate, quick method of detecting HIV antibodies. These advantages and the thermal stability of the reagents that are used make this an attractive alternative for detecting prior exposure of individuals to HIV-1.

Infection with human immunodeficiency virus in the Pittsburgh transplant population. A study of 583 donors and 1043 recipients, 1981-1986

We performed a retrospective serologic survey of 583 organ donors and 1043 transplant recipients for antibodies to human immunodeficiency virus type 1 (HIV-1). Two (0.34%) of the 583 donors and 18 (1.7%) of the 1043 recipients had HIV-1 antibodies by enzyme immunoassay and by Western blot. Two of 5 seropositive recipients tested also had blood cultures positive for HIV-1. Seven (0.7%) of the 1043 transplant recipients had antibodies to HIV-1 before transplantation; 2 of these had hemophilia A, and 5 had previous transfusions. Eleven (1.3%) of 860 recipients followed for 45 days or more seroconverted to HIV-1 a mean of 96 days after transplantation. Likely sources of HIV-1 infection for 3 of these 11 recipients included a seropositive organ donor in 1 patient and high-risk blood donors in 2 patients. A definite source of HIV-1 infection was not found for the other 8 recipients, 3 of whom seroconverted to HIV-1 after institution of blood donor screening for HIV-1 antibodies. Seroconversion to HIV-1 was less common in kidney recipients than in liver, heart, or multiple-organ recipients (P less than 0.02). Nine (50%) of the 18 HIV-1 seropositive transplant recipients died a mean of 6 months after transplant surgery, and 9 (50%) are still alive a mean of 43 months after transplantation. AIDS-like illnesses occurred in 3 of the dead and 1 of the living patients and included pneumocystis pneumonia (3 cases), miliary tuberculosis (1 case), and recurrent cytomegalovirus infection (1 case). These data suggest that the course of HIV-1 infection is not more severe in transplant recipients receiving cyclosporine than in other hosts and that, despite screening of blood and organ donors, a small number of transplant recipients will become infected with HIV-1.

False-positive sera do not react with human immunodeficiency virus (HIV) gag-encoded recombinant antigen

Ten sera from healthy blood donors positive by enzyme-linked immunoadsorbent assay (ELISA) were studied by immunoblot assay using natural and recombinant proteins. They interacted only with p17 or p24 proteins but were nonreactive with a recombinant protein (RP 50), which carries antigenic determinants to p17 and p24. Reactions were not blocked by preincubation of sera with genetically engineered p17 and p24 or purified viral p24, indicating that some new epitopes were formed during the Western blot procedure. Recombinant gag-encoded protein is required for confirmation of human immunodeficiency virus (HIV) seropositivity.

Long-term persistence of false positive antibody reactivity in HIV western blot testing of sera from a healthy blood donor

HIV-Western blot (WB) testing of sequential sera from a blood donor revealed identical bands in the p24 and p55 positions. Additional testing using indirect immunofluorescence antibody technique, radioimmunoprecipitation assay and an HIV p24 antigen immunoassay were negative. During a 5-year follow-up period the blood donor has remained apparently healthy and no signs of disease have developed. We conclude that sera from this blood donor show a false positive HIV WB reactivity. The nature of this reactivity remains obscure but has practical implications for the routine HIV screening of blood donors.

HTLV-1 in Switzerland: low prevalence of specific antibodies in HIV risk groups, high prevalence of cross-reactive antibodies in normal blood donors

Sera from various Swiss population groups were tested for antibodies against the human T-cell leukemia virus type I (HTLV-I). Particle agglutination and ELISA were performed for screening; Western blot was done for confirmation. True-positive sera were found at a prevalence of 0.12% in a cohort of 846 individuals at risk for AIDS tested in 1984-1985. Prevalences of 0.35% were found among 575 HIV-I positives tested in 1987, and of 1.3% among 292 HIV-I positives of a different group tested in 1988. The 6 positives found in our study represent the first cases of HTLV-I infection, or HIV-I/HTLV-I double infection, diagnosed in Switzerland. In addition, high proportions of sera, regardless of whether they were from normal blood donors, HIV-positives, or individuals at risk for AIDS, had antibodies that reacted weakly with one or several proteins of the size of viral gag proteins. The prevalence of such antibodies in normal donors was in the range of 10 to 40%, depending on the strictness of interpretation. Competition Western blots performed with some of these sera showed that these antibodies reacted with HTLV-I, but not with HIV-I or cellular antigens, and had a lower affinity to HTLV-I proteins than the antibodies of human or goat antisera. The results indicate that these antibodies may be induced by agents immunologically related to, but different from, HTLV-I, which are highly prevalent in the Swiss population. Oligopeptide stretches with sequence homology to HTLV-I are known to exist in various normal body proteins, several infectious agents including common viruses and protozoa, but the results might also indicate the existence of additional human retroviruses. Screening of blood donors with sensitive tests for antibodies to HTLV-I might produce an unacceptably high rate of false-positive results, if stringent rules of interpretation analogous to those common in HIV screening are not used.

Transfusion transmitted human T-lymphotropic virus infections

Human immunodeficiency virus (HIV) type 1 has emerged during the 1980s as an important transfusion transmitted agent. The impact of HIV depends on the epidemiology and characteristics of the virus, serological response to infection and efficacy of serological tests to identify infected blood units. These factors will be described in the present article. The risk to acquire HIV today, by transfusion of anti-HIV screened blood, is extremely small in Scandinavia and the Western world. The risk can be further minimized by more sensitive screening tests and an improved donor information. The epidemiology in Scandinavia of other members of the human T-lymphotrophic viruses, HTLV-1 and HIV-2, has to be further investigated.

False-positive band in the gp41 region in anti-HIV western blotting

A consistently positive ELISA reaction and a band in the gp41-region of the HIV-1 western blot were found in repeated serum samples from a healthy pregnant woman. The band was more clearly defined than the HIV gp41 band. Additional ELISA testing and repeated western blot analyses using different test kit batches confirmed our suspicion of a false-positive reaction.

Comparative evaluation of particle agglutination test for antibody to human immunodeficiency virus

A comparative evaluation of a new serological test for human immunodeficiency virus (HIV) was carried out. The test used the agglutination of gelatin particles coated with HIV antigen. It was found to be more sensitive than current enzyme linked immunosorbent assays (ELISAs) and more specific than the western blot test. Because of its simplicity, it promises to be of value, especially in developing countries.

The Karpas AIDS Cell Test compared with an enzyme-linked immunosorbent assay for detecting antibody to the human immunodeficiency viruses (HIV-I and HIV-2)

We have compared the Karpas AIDS Cell Test for antibodies to the human immunodeficiency viruses (HIV) with a commercial enzyme-linked immunosorbent assay (ELISA) (Organon Teknika) by testing serum samples from 324 intravenous drug abusers in Turin. The cell test was found to be more sensitive and as specific as the ELISA with the serum samples from the drug abusers. In Lisbon, 30 samples were tested on slides containing cells infected with HIV-1 and/or HIV-2. All 15 samples, which were positive for HIV-2 alone (in the HIV-2 Elavia test and by the Western blotting technique), were also positive in the Karpas AIDS test. In contrast, only one of the 15 samples (7%) gave a positive reading in the ELISA for HIV-1. Results of 30 samples tested in Turin and Lisbon by the Western blotting technique agreed closely with those obtained with the Karpas AIDS Cell Test. We were also able to show that the entire test can be performed at room temperature and completed within 1 hour. Moreover, the cell test requires minimal skill and simple equipment and is inexpensive. It also includes non-infected cells as a control and the specificity of positive samples may be verified with a bench microscope. Furthermore, this test which detects antibodies to both HIV-1 and HIV-2 allows rapid typing of the infecting strain.

Antibodies reactive with human immunodeficiency virus gag-coded antigens (gag reactive only) are a major cause of enzyme-linked immunosorbent assay reactivity in a blood donor population

Normal blood donors were examined for human immunodeficiency virus (HIV)-reactive antibodies with both virus- and Escherichia coli-expressed env- and gag-coded antigens. The frequency of samples from normal (low-risk) donors that were repeatedly reactive with an HIV enzyme-linked immunosorbent assay blood screening test (Du Pont Co.) was 0.6%. Two classes of HIV serological reactivity were identified: a minor env-reactive class (0.03 to 0.06% of donors) and the predominant env-nonreactive gag-reactive class (gag reactive only [GRO]) (0.4 to 0.5% of donors). Assignment of env reactivity was made by a synthetic (recombinant) env enzyme-linked immunosorbent assay and virus immunoblot. Most GRO sera reacted with p15/p17 bands on HIV immunoblot. Antibody specificity in GRO sera was confirmed by competition-binding studies with viral gag and E. coli-expressed p55gag. This study provides independent verification that gag-specific antibodies are present in many env-nonreactive sera. More serological and virological studies of individuals with this antibody pattern should be pursued to determine the origin of these gag-reactive antibodies.

Comparison of six serological assays for human immunodeficiency virus antibody detection in developing countries

Three commercially available assays for the detection of human immunodeficiency virus (HIV) antibodies-Vironostika enzyme immunoassay (EIA), Wellcozyme competitive EIA, and JLC Allaman indirect immunofluorescence assay--were tested on 300 serum samples from African subjects with and without HIV-related conditions. Two experimental assays both rapid and simple to perform (Biotech dip stick and Cambridge Bioscience latex agglutination) were also evaluated on the same serum samples. The results were compared with those of a commercial Western blot (WB) (immunoblot) assay from Biotech, used as the reference technique. All assays were tested in the laboratory of the AIDS Project in Kigali, Rwanda. Calculated specificity ranged from 90.8% (dip stick) to 98.6% (Vironostika EIA, Wellcozyme competitive EIA, and Cambridge Bioscience latex agglutination). Sensitivity ranged from 95.2% (Cambridge Bioscience latex agglutination) to 98.0% (Vironstika EIA) and JLC indirect immunofluorescence assay). However, the sensitivity of the latex agglutination test improved to 98.6% after the prozone effect was controlled for by serial twofold dilution of latex agglutination-negative, WB-positive samples. In situations with a high prevalence of HIV infection, any one of these tests can be regarded as an alternative to the more expensive, time-consuming, and difficult WB assay.

Acquired immunodeficiency syndrome mimicking Sjögren's syndrome and systemic lupus erythematosus

We describe a patient in whom the diagnosis of transfusion-associated acquired immunodeficiency syndrome (AIDS) was delayed because her clinical symptoms were similar to those of systemic lupus erythematosus and Sjögren's syndrome and because of a false-negative result on a Western blot test for human immunodeficiency virus. The importance of using different diagnostic tests for AIDS and the pitfalls in diagnosing AIDS in patients who appear to have connective tissue disease are discussed.