HIV screening among patients seeking care at Xuanwu Hospital: A cross-sectional study in Beijing, China, 2011-2016

Objectives

One-third of people living with HIV in China are still unaware of their status, so we sought to better understand HIV testing in the general hospital setting in China.

Methods

A cross-sectional study was conducted using the electronic medical records of all patients who attended Xuanwu Hospital in Beijing, January 1, 2011 to December 31, 2016. HIV screening and detection rates and characteristics of patients diagnosed with HIV were assessed.

Results

Overall, 235,961 patients were screened, for a screening rate of 1.4%. Although most were outpatients (98.4%), screening rate was higher among inpatients (70.0% versus 0.4%), and highest in internal medicine (36.1%) and surgery (33.3%) departments. A total of 140 patients were diagnosed with HIV, for a detection rate of 5.93 per 10,000. Detection rates were highest among outpatients (9.34 per 10,000), and patients attending the dermatology and sexually transmitted infection (STI) department (153.85 per 10,000). Most diagnoses were made among males (91.4%), aged 20–39 (67.1%), who reported becoming infected through homosexual contact (70.0%).

Conclusions

HIV screening in China’s general hospitals needs to be improved. More focus should be placed on screening outpatients, especially in the dermatology and STI department, and young men.

The characteristics of screening and confirmatory test results for HIV in Xi'an, China

OBJECTIVES

Individuals with recent or acute HIV infection are more infectious than those with established infection. Our objective was to analyze the characteristics of detection among HIV infections in Xi'an.

METHODS

A 4th-generation kit (Architect HIV Ag/Ab Combo) and three 3rd-generationEIA kits (WanTai, XinChuang and Livzon) were used for HIV screening. Overall, 665 individuals were identified as positive and were tested by western blotting (WB). The characteristics of the screening and confirmatory tests were analyzed, including the band patterns, the early detection performance and the false-positive rates.

RESULTS

In total, 561 of the 665 patients were confirmed as having HIV-1 infection, and no HIV-2 specific band was observed. Among these 561 WB-positive cases, reactivity to greater than or equal to 9 antigens was the most commonly observed pattern (83.18%), and the absence of reactivity to p17, p31 and gp41 was detected in 6.44%, 5.9% and 2.86% of the cases, respectively. Two cases were positive by the 4th-generation assay but negative by the 3rd-generation assay for HIV screening and had seroconversion. The false-positive rate of the Architect HIV Ag/Ab Combo (22.01%) was significantly higher than those of WanTai (9.88%), XinChuang (10.87%) and Livzon (8.93%), p<0.05.

CONCLUSION

HIV infection in Xi'an is mainly caused by HIV-1, and individuals are rarely identified at the early phase. Although the false-positive rate of the 4th-generation assay was higher than that of the 3rd-generation assay, it is still recommended for use as the initial HIV screening test for high-risk individuals. In Xi'an, a 3rd-generation assay for screening could be considered.

Generation of a recombinant Gag virus-like-particle panel for the evaluation of p24 antigen detection by diagnostic HIV tests

Background

Detection of HIV-1 p24 antigen permits early identification of primary HIV infection and timely intervention to limit further spread of the infection. Principally, HIV screening should equally detect all viral variants, but reagents for a standardised test evaluation are limited. Therefore, we aimed to create an inexhaustible panel of diverse HIV-1 p24 antigens.

Methods

We generated a panel of 43 recombinantly expressed virus-like particles (VLPs), containing the structural Gag proteins of HIV-1 subtypes A-H and circulating recombinant forms (CRF) CRF01_AE, CRF02_AG, CRF12_BF, CRF20_BG and group O. Eleven 4^th generation antigen/antibody tests and five antigen-only tests were evaluated for their ability to detect VLPs diluted in human plasma to p24 concentrations equivalent to 50, 10 and 2 IU/ml of the WHO p24 standard. Three tests were also evaluated for their ability to detect p24 after heat-denaturation for immune-complex disruption, a pre-requisite for ultrasensitive p24 detection.

Results

Our VLP panel exhibited an average intra-clade p24 diversity of 6.7%. Among the 4^th generation tests, the Abbott Architect and Siemens Enzygnost Integral 4 had the highest sensitivity of 97.7% and 93%, respectively. Alere Determine Combo and BioRad Access were least sensitive with 10.1% and 40.3%, respectively. Antigen-only tests were slightly more sensitive than combination tests. Almost all tests detected the WHO HIV-1 p24 standard at a concentration of 2 IU/ml, but their ability to detect this input for different subtypes varied greatly. Heat-treatment lowered overall detectability of HIV-1 p24 in two of the three tests, but only few VLPs had a more than 3-fold loss in p24 detection.

Conclusions

The HIV-1 Gag subtype panel has a broad diversity and proved useful for a standardised evaluation of the detection limit and breadth of subtype detection of p24 antigen-detecting tests. Several tests exhibited problems, particularly with non-B subtypes.

In vivo biotinylation and capture of HIV-1 matrix and integrase proteins

This report describes the adaptation of the biotin ligase BirA-biotin acceptor sequence (BAS) labeling system to biotinylate specific human immunodeficiency virus 1 (HIV-1) proteins in vivo. Two HIV-1 clones were constructed, with the BAS introduced into the matrix region of gag or the integrase region of pol. Specific biotinylation of target proteins in virions was observed when molecular clones were co-expressed with BirA. Both BAS-containing viruses propagated in SupT1 T-cells although replication of the integrase clone was delayed. Further studies demonstrated that the integrase insertion yielded an approximate 40% reduction in single-round infectivity as assessed on MAGI-5 indicator cells, as well as in the in vitro integration activity of preintegration complexes extracted from acutely infected C8166-45 T-cells. Biotinylation of the integrase BAS tag furthermore rendered this virus non-infectious. The matrix viral clone by contrast displayed wild-type behavior under all conditions tested. These results therefore establish a system whereby biotinylated matrix protein in the context of replication-competent virus could be used to label and capture viral protein complexes in vivo.

Efficacy assessment of a cell-mediated immunity HIV-1 vaccine (the Step Study): a double-blind, randomised, placebo-controlled, test-of-concept trial

BACKGROUND

Observational data and non-human primate challenge studies suggest that cell-mediated immune responses might provide control of HIV replication. The Step Study directly assessed the efficacy of a cell-mediated immunity vaccine to protect against HIV-1 infection or change in early plasma HIV-1 levels.

METHODS

We undertook a double-blind, phase II, test-of-concept study at 34 sites in North America, the Caribbean, South America, and Australia. We randomly assigned 3000 HIV-1-seronegative participants by computer-generated assignments to receive three injections of MRKAd5 HIV-1 gag/pol/nef vaccine (n=1494) or placebo (n=1506). Randomisation was prestratified by sex, adenovirus type 5 (Ad5) antibody titre at baseline, and study site. Primary objective was a reduction in HIV-1 acquisition rates (tested every 6 months) or a decrease in HIV-1 viral-load setpoint (early plasma HIV-1 RNA measured 3 months after HIV-1 diagnosis). Analyses were per protocol and modified intention to treat. The study was stopped early because it unexpectedly met the prespecified futility boundaries at the first interim analysis. This study is registered with ClinicalTrials.gov, number NCT00095576.

FINDINGS

In a prespecified interim analysis in participants with baseline Ad5 antibody titre 200 or less, 24 (3%) of 741 vaccine recipients became HIV-1 infected versus 21 (3%) of 762 placebo recipients (hazard ratio [HR] 1.2 [95% CI 0.6-2.2]). All but one infection occurred in men. The corresponding geometric mean plasma HIV-1 RNA was comparable in infected male vaccine and placebo recipients (4.61 vs 4.41 log(10) copies per mL, one tailed p value for potential benefit 0.66). The vaccine elicited interferon-gamma ELISPOT responses in 75% (267) of the 25% random sample of all vaccine recipients (including both low and high Ad5 antibody titres) on whose specimens this testing was done (n=354). In exploratory analyses of all study volunteers, irrespective of baseline Ad5 antibody titre, the HR of HIV-1 infection between vaccine and placebo recipients was higher in Ad5 seropositive men (HR 2.3 [95% CI 1.2-4.3]) and uncircumcised men (3.8 [1.5-9.3]), but was not increased in Ad5 seronegative (1.0 [0.5-1.9]) or circumcised (1.0 [0.6-1.7]) men.

INTERPRETATION

This cell-mediated immunity vaccine did not prevent HIV-1 infection or reduce early viral level. Mechanisms for insufficient efficacy of the vaccine and the increased HIV-1 infection rates in subgroups of vaccine recipients are being explored.

[Assay for simultaneous detection of HIV p24 antigen and anti-HIV antibody]

OBJECTIVE

To develop a rapid assay for simultaneous detection of HIV p24 antigen (Ag) and anti-HIV antibody (Ab).

METHODS

HIV-1 gp41 antigen and HIV-2 gp36 antigen were expressed by recombinant baculovirus insect system and purified by immunochromatography. p24 monoclonal antibody (mAb) was obtained from p24 hybridoma cell line. Purified antigen and mAb were dot blotted to nitrocellular membrane; 20 nm colloidal gold-anti-human IgG ab and p24 ab complex were used for this test. Previously detected 39 sera specimens were tested in this study to compare with the result of HIV test with commercial HIV test kit.

RESULTS

20 mg/L purified gp41 Ag and gp36 Ag were obtained from recombinant baculovirus-insect cell system; 1.5 mg/L p24 mAb was obtained from p24 mAb hybridoma cell line. Compared the test result of 39 sera with commercial HIV test kits, consistency rate was 100%.

CONCLUSIONS

The rapid assay for simultaneous detection of HIV p24 antigen and anti-HIV antibody provides a simple, sensitive and reliable test for HIV diagnosis.

Recombinant fusion proteins for haemagglutination-based rapid detection of antibodies to HIV in whole blood

Recombinant fusion proteins, consisting of a monovalent anti-human RBC monoclonal antibody B6, and conserved immunodominant peptide of HIV-1 envelope glycoprotein gp41 or HIV-2 envelope glycoprotein gp36, have been designed and purified after over-expression in E. coli. These fusion proteins are Fab-based and were obtained by assembling the light chain with Fd (variable domain and the first constant domain of the heavy chain) or Fd fusions containing HIV-derived peptide, and following a protocol of in vitro denaturation of inclusion bodies and subsequent renaturation to assemble functional Fab. Using a multistep column chromatographic procedure, monomeric Fab and Fab fusion proteins containing HIV-derived peptide were purified to high degree, free of aggregates. The yield of various proteins on the laboratory scale (1-2 l of shake flask culture) was in the range of tens of milligram. Purified anti-human RBC Fab fusion proteins containing sequences derived from HIV-1 gp41 and HIV-2 gp36 were highly specific for detection of antibodies to HIV-1 and HIV-2, respectively. The described design, expression and purification protocols will make it possible to produce specific recombinant reagents in large quantities for agglutination-based rapid detection of antibodies to HIV in whole blood.

Gag-derived proteins of HIV-1 isolates from Indian patients: cloning, expression, and purification of p17 of B- and C-subtypes

A simple and efficient method for expression in Escherichia coli and purification of matrix protein, p17, of human immunodeficiency virus type 1 (HIV-1) of both B- and C-subtypes is described. DNA sequences encoding p17 of B- and C-subtype were cloned from respective gag sequences. The gag sequences were obtained by PCR amplification using DNA extracted from peripheral blood lymphocytes of an HIV-1 infected patient from India. A T7-promoter-based expression system was optimized for expression of p17 in soluble form. p17 (B- and C-subtype) was purified to near homogeneity using conventional chromatographic techniques. Purification of p17 (C-subtype) is described for the first time with yield of 7.7 mg from a 1-liter culture. The yield of p17 (B-subtype) is 14.7 mg from a 1-liter culture, which is severalfold better than that reported earlier. N-terminal sequencing and CD spectra of the purified proteins, p17B and p17C, show that the proteins are properly processed and well-folded. The immunoreactivity of both types of p17 to sera from HIV-infected individuals is comparable.

Retrovirus in salivary glands from patients with Sjögren's syndrome

AIMS

To investigate the possibility of an immune response to retroviral antigens or of detecting retrovirus in Sjögren's syndrome.

METHODS

Retroviruses were sought in labial salivary glands and peripheral blood mononuclear cells from patients with Sjögren's syndrome by immunoblotting assay, immunohistochemical assay, polymerase chain reaction (PCR), reverse transcriptase (RT) activity assay, and transmission electron microscopy.

RESULTS

Sera from five of 15 patients with Sjögren's syndrome (33%) reacted against p24 group specific antigen (gag) of human immunodeficiency virus (HIV). Labial salivary gland biopsy specimens from seven of the 15 patients with Sjögren's syndrome (47%) contained an epithelial cytoplasmic protein reactive with a monoclonal antibody to p24 of HIV. PCR was performed to detect HIV and human T lymphotropic virus type I (HTLV-I) genes from salivary gland tissues and peripheral blood mononuclear cells from patients with Sjögren's syndrome. Mn2+ dependent, Mg2+ independent RT activity was detected in the salivary gland tissues in three of 10 patients. A-type-like retroviral particles were observed in epithelial cells of salivary glands by transmission electron microscopy. Target genes for HIV and HTLV-I were not found in any of the salivary gland tissues or peripheral blood mononuclear cells from Sjögren's syndrome patients.

CONCLUSIONS

The data suggest the presence of an unknown retrovirus similar to HIV in the salivary gland which might be involved in the pathogenesis of a subpopulation in Sjögren's syndrome.

Overproduction, purification, and diagnostic use of the recombinant HIV-1 Gag proteins, the precursor protein p55 and the processed products p17, p24, and p15

HIV-1 Gag protein precursor p55, and its processed products, p17, p24, and p15 were overproduced in Escherichia coli and purified to near homogeneity. To study the antigenic properties and the potentiality as the diagnostic and prognostic reagents, varying amounts of the purified Gag proteins were dotted onto the polyvinylidene difluoride membrane and reacted with 40 sera of HIV-1-infected individuals (35 AC, 1 ARC, and 4 AIDS patients) and 10 sera of normal healthy donors. p55 reacted with 40 (100%) sera of HIV-1 carriers, while p17, p24, and p15 reacted with 37 (92.5%), 35 (87.5%) and 34 (85%) of the 40 sera of HIV-1 carriers, respectively. On the whole, the reaction of p55 was especially strong and that of p15 was the weakest. p55 showed the strongest reaction among the four Gag proteins with all specimens, and it showed a positive reaction with a carrier serum with which none of the processed Gag proteins showed a positive reaction. Therefore, p55 is the most useful antigen among the four Gag proteins for detection of the Gag antibodies and may even be one of the most useful antigens for the diagnosis of HIV-1 infection.

[Laboratory diagnosis of HIV infection]

Recent use of modern methods in the field of molecular biology has provided new insights into the genetic and structural nature of HIV, which are now increasingly being applied to the diagnostic work-up. For the reliable laboratory diagnosis of HIV infection, three different possibilities are available: detection of specific antibodies against viral proteins (anti HIV AB), detection of the virus itself (HIV antigen) and detection of viral nucleic acid using in vitro amplification techniques. In this overview, we compare clinical and diagnostic parameters of an HIV infection, and discuss the current state of the art of an HIV infection and the future prospects offered by new molecular biological methods such as the use of recombinant antigens or the polymerase chain reaction (PCR) for the detection of viral nucleic acid.

Influence of MA internal sequences, but not of the myristylated N-terminus sequence, on the budding site of HIV-1 Gag protein

HIV-1 Gag protein intracellular transport and budding was investigated by altering the sequence of the MA domain, which directly bears an essential N-terminal myristyl adduct and forms the viral matrix after Gag proteolysis in mature virions. We found that removal of a substantial MA internal segment did not abolish the assembly and budding of Gag particles, but rather diverted these events to intracellular cisternae. The internally deleted Gag was further modified by substituting either of two heterologous myristylated N-termini for the natural one: amino acids 1-12 from v-Src oncoprotein (for which a membrane-bound intracellular receptor has been postulated), or amino acids 1-12 from Poliovirus polyprotein (for which no membrane-targeting function has been demonstrated). Both Src-Gag and Polio-Gag chimerae exhibited transport and processing characteristics similar to those of the MA-deleted Gag. These results are discussed with respect to the possible transport pathway of HIV-1 Gag.

Evaluation of the automated 'Enzymen-Test Anti HIV-1 + 2' and 'Enzymen-Test Anti HIV-1/2 selective' for the combined detection and differentiation of anti-HIV-1 and anti-HIV-2 antibodies

A new, modular automated ELISA (test 1) for HIV-1 and HIV-2 antibody detection and differentiation (Enzymun-Test Anti HIV-1 + 2; anti HIV 1/2 selective, Boehringer Mannheim) was compared with 3 alternative enzyme immunoassays (Abbott recombinant HIV-1/HIV-2 3rd generation EIA, Abbott (test 2); Enzygnost HIV 1 + 2, Behringwerke (test 3); and Wellcozyme HIV recombinant, Murex (test 4)) and Western blot (New LAV I Blot and New LAV II Blot; Diagnostics Pasteur). 380 serum samples from HIV-1 and HIV-2 seropositive patients at different stages of disease, high risk individuals, patients with conditions unrelated to AIDS and from healthy blood donors were used in this evaluation along with 6 seroconversion panels, 6 serum dilution series and 'tricky' sera (repeatedly positive results in ELISA, but negative or undeterminate in Western blot; n = 67). Using the Western blot as reference assay, the overall sensitivity of the four ELISAs was 100%. Test 4 showed the highest sensitivity for antibody detection in seroconversion and dilution series. A high specificity was achieved with test 1 (100%) and test 2 (99.4%). A relatively high rate of false positive results were obtained with test 2 (n = 12) and test 3 (n = 10) by testing 'tricky' sera or samples obtained from healthy blood donors. In comparison to Western blot, a clear differentiation between HIV-1 and HIV-2 antibody serum samples was achieved with the Enzymun-Test. The results of the present study show that the Enzymun-Test provides reliable selective HIV-1 and HIV-2 antibody detection at a cost which is significantly lower than the costs of Western blot tests. Furthermore, the evaluation of test 1 suggests, that it is a highly specific assay for HIV antibody detection.

Overexpression of HIV-1 proteins in Escherichia coli by a modified expression vector and their one-step purification

A synthetic expression system, pMH, was constructed for high-level expression and rapid purification of HIV-1 proteins in Escherichia coli, by introducing two synthetic sequences. The first sequence permitted a high-level expression via a second ribosome-binding site plus an A/T-rich region. This minicistron between the 5' untranslated region of the mRNA and the protein-coding region minimized the formation of local secondary structures and favored ribosome binding. The second region coded for six histidines, which allowed for easy purification of the proteins. Purification was based on interaction of the protein with metal ions: immobilized metal affinity chromatography. The p17 and p24 structural genes of HIV-1 were cloned into this modified expression vector. Expression of the structural proteins represented up to 30% of the total protein in E. coli, i.e., 40 mg of highly purified protein could be obtained per liter of culture.

Detection of simian immunodeficiency virus and human immunodeficiency virus type 2 capsid antigens by a monoclonal antibody-based antigen capture assay

We have tested the ability of a monoclonal antibody-based simian immunodeficiency virus (SIV) p27 capsid antigen assay to detect SIV antigen in supernatants from a variety of infected cell cultures. The antigen capture assay has a sensitivity of approximately 30 pg of SIV p27 capsid antigen/ml. The assay detected SIV p27 capsid antigen in cell culture supernatants from all six strains tested, detected the replication of SIV following the inoculation of the virus in peripheral blood mononuclear cell cultures earlier compared to reverse transcriptase assay, and was more sensitive in detection of the SIV antigen compared to human immunodeficiency virus type 1 (HIV-1) antigen capture assays. The SIV antigen capture assay was used to detect SIV antigen from serum samples and tissue cultures from eight of eight SIVB670-infected rhesus macaques (Macaca mulatta). Similar samples from four control rhesus macaques were negative when tested by the assay. The SIV antigen was detected in virus-infected monkeys during early time periods following inoculation (1 to 3 weeks) or during episodes of CD4+ lymphocytopenia and clinically evident disease. In addition, the SIV antigen capture assay positively identified each of three different HIV-2 strains in cell culture supernatants. The SIV antigen capture assay provides a sensitive and specific method to monitor SIV and HIV-2 capsid antigen in cell cultures and from infected animals. The assay will be an important tool in the utilization of SIV and HIV-2 primate models for HIV-induced acquired immunodeficiency disease syndrome.

Envelope glycoproteins of HIV-1, HIV-2, and SIV purified with Galanthus nivalis agglutinin induce strong immune responses

Lectin affinity chromatography was used to purify in a single step the envelope glycoproteins of HIV-1, HIV-2, and SIV. Envelope glycoproteins carry the major determinants essential for protection by the humoral immune response. The purification of these proteins has previously been a laborious procedure. The glycoproteins were purified by a one-step procedure to a high level of purity by using Galanthus nivalis agglutinin (GNA). The purified glycoprotein had CD4-binding and antigenic reactivities. Strong immune responses to envelope proteins and peptides were seen in mice and primates after immunization with these preparations.

[New methods of isolating recombinant proteins]

Recombinant proteins are isolated from very complex protein mixtures present in the producing cell. The isolation process involves in general four mutually interconnected stages: 1. release of the recombinant protein from the cellular environment, 2. preparation of the specimen for separation, 3. separation, 4. qualitative and quantitative analysis of the preparation. Each of these stages is formed by a complex series of methods which destroy the cellular wall, solubilize the specimen and involve the use of suitable precipitation, chromatographic, electrophoretic, immunochemical and other techniques for separation and analysis. In the submitted paper the authors describe a relatively simple isolation of recombinant peptide used for the preparation of a diagnostic kit for AIDS. From knowledge of the sequence of nucleotides in cDNA antisense peptides can be derived which have a high affinity with the isolated protein and they can be also used for affinity chromatography. An effective isolation technique is the use of mimetic ligands on the basis of textile dyes. By their combination and possible modification it is also possible to achieve separation of the required protein from contaminating substances. The mentioned highly specific methods can be combined with classical chromatographic techniques. During every step individual chromatographic fractions are tested by SDS electrophoresis in polyacrylamide gel incl. possible use of immunoblotting a specific staining.

Bacterial expression, purification, and in vitro N-myristoylation of HIV-1 p17gag

The coding region of the N-terminal 17-kDa portion of HIV-1 Pr55gag (p17gag) was cloned into the pET-3c expression vector and was used to overexpress HIV-1 p17gag in Escherichia coli. Induction of the transformed bacteria caused the accumulation of a 17-kDa polypeptide in the soluble cell fraction which was released by sonication in hypotonic nondetergent buffer. The 17-kDa polypeptide was purified by ammonium sulfate precipitation and successive chromatography on G-75 Sephadex, DEAE-Sephacel, and S-Sephadex. The final product was purified 12-fold with about a 16% recovery from the original soluble cell lysate and was judged to be 97+% pure by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Western blotting with two different antibodies confirmed the identify of the purified 17-kDa polypeptide as authentic p17gag. In the presence of myristoyl-CoA and bovine brain N-myristoyl-transferase, p17gag was quantitatively N-myristoylated in vitro with a pseudo-first-order rate constant of 4.7 +/- 1.0 x 10(-3) min-1, but with only about 3% of the catalytic efficiency of N-myristoylation of a 16-residue peptide homologous to the N-terminus of p17gag. The myristate group in the N-myristoylated p17gag was stable to treatment with detergent and hydroxylamine consistent with a covalent N-acyl-amide linkage. The N-myristoylglycyl linkage was confirmed by partial acid hydrolysis and identification of the p-nitrobenzylazlactone derivative of the resulting N-myristoylglycine by high-performance liquid chromatography.

Gag proteins of the highly replicative MN strain of human immunodeficiency virus type 1: posttranslational modifications, proteolytic processings, and complete amino acid sequences

The MN strain of human immunodeficiency virus type 1 was grown in H9 cells, concentrated by centrifugation, and disrupted, and proteins were purified by reversed-phase high-pressure liquid chromatography. Complete amino acid sequences were determined for the mature Gag proteins, showing natural proteolytic cleavage sites and the order of proteins (p17-p24-p2-p7-p1-p6) in the Gag precursors. At least two sequence variants of p24 and eight sequence variants of p17 were detected. The two most abundant variants of p24 and p17 represented at least 50% +/- 5% and 20% +/- 5% of their totals, respectively. These data suggest heterogeneity in the virus population, with 50% of the total virus containing the most abundant forms of p17 and p24 and 20% of the virus containing the second most abundant forms. The Gag precursors of these suggested viruses differ from each other by only 3 amino acid residues but differ from the precursors predicted by the published MN proviral DNA sequence by 10 residues. Electrospray ionization mass spectrometry analysis of the purified p24 forms showed that the measured molecular weight of the protein was 200 +/- 50 atomic mass units greater than the calculated molecular weight. The source of additional mass for the p24 forms was not determined, but the observation is consistent with previous suggestions that the protein is phosphorylated. Greater than 98% of the total recovered p17 was myristylated at the N-terminal glycine residue, and the measured molecular weights (as determined by electrospray ionization mass spectrometry) of the most abundant forms were within 3 atomic mass units of the calculated molecular weights (15,266).

[HIV-2 in The Netherlands]

By comparing data from the HIV confirmation laboratories it could be established that in the period prior to February 1991 a HIV-2 infection was demonstrated in at least 18 persons in the Netherlands. Consequently, use of combined HIV-1/2 tests is urgently recommended for screening in diagnostic and blood bank laboratories in the Netherlands. A suspicion of presence of HIV-2 antibodies may arise in the interpretation of a combined HIV-1/2-ELISA, a specific HIV-1-ELISA and the pattern of HIV-1 western immunoblot. Confirmation of the presence of HIV-2 antibodies should be obtained by means of western blots of viral lysates of both HIV-1 and HIV-2 and peptide tests from the transmembranous region. Most persons with a HIV-2 infection originated from Africa south of the Sahara or the Cape Verdean Islands or had had a sexual relationship with a person from these areas. The vast majority was heterosexual and 13 of the 18 infected persons were women. This differs greatly from the epidemiological pattern of HIV-1 infections in the Netherlands. The possibility of further spread of HIV-2 in the Netherlands via heterosexual contacts should be seriously taken into account.

Lack of evidence of occult human immunodeficiency virus in seronegative individuals at very high risk of infection

Reports of human immunodeficiency virus (HIV) infection in seronegative individuals prompted the authors to investigate subjects who are at very high risk of acquisition of HIV in San Francisco. Nine HIV seronegative subjects were evaluated extensively, eight of whom were drawn from a well-characterized cohort of seropositive and seronegative homosexual men who have been followed prospectively since 1983-1984. These men have calculated probabilities of infection based on a fitted model of between 0.22 and 0.94. One additional subject is an intravenous drug user who has shared needles with HIV-infected individuals extensively. Peripheral blood lymphocytes and monocytes were separately cultured from each subject and evidence of HIV infection was sought by a reverse transcriptase assay, enzyme immunoassay, and immunocytofluorographic analysis for HIV antigens, in situ hybridization, RNA slot blot analysis, and polymerase chain reaction amplification of HIV cDNA. Uncultured monocytes and lymphocytes from each donor were also examined by these techniques. Evidence of HIV infection was not found in the peripheral blood mononuclear cells of these high risk individuals.

Oligomeric nature of transmembrane glycoproteins of HIV-2: procedures for their efficient dissociation and preparation of Western blots for diagnosis

Western blot (WB) analysis of various strains of HIV-2 indicated that transmembrane glycoprotein (TMP) of HIV-2 exists as trimers. These trimers have molecular weights and electrophoretic mobilities in the region of the major external glycoprotein, gp120, resulting in WB misidentification during diagnosis. A simple and rapid procedure was developed using trichloroacetic acid (TCA) to efficiently dissociate oligomeric forms of the TMP to monomers prior to the preparation of WB. This procedure permitted the unambiguous identification of antibodies to gp120 and to the TMP. Use of HIV-2 WB strips without any oligomeric forms of the TMP demonstrated (1) that cross reactivity of HIV-1-positive specimens on HIV-2 WB was mainly directed to Gag and Pol proteins, with some reactivity to gp36/gp41 TMP, but none to gp120; (2) that these strips can substantially reduce the number of specimens falsely identified as dually (HIV-1 and HIV-2) reactive; and (3) that HIV-2-positive specimens reacted to viral gp120 in a strain-specific manner, demonstrating high antigenic variation in this glycoprotein. It is recommended that this general procedure of viral protein dissociation be used for HIV-2 WB preparation.

Antiretroviral therapy in combination with interferon for AIDS-related Kaposi's sarcoma

In vitro studies have shown that 3'-azido-3'-deoxythymidine (zidovudine, AZT) and interferon synergistically inhibit the replication of the human immunodeficiency virus type 1 (HIV) in peripheral blood mononuclear cells at concentrations achievable in patients. Interferon alfa can cause lesions to regress in patients with acquired immunodeficiency syndrome (AIDS)-related Kaposi's sarcoma (KS). Although zidovudine has no significant effect on the regression of these lesions, it does have antiviral activity in these patients as manifested by a decline in serum HIV antigen. However, when used separately, the two drugs can have serious side effects in some patients. In addition, the development of zidovudine-resistant strains has been noted in patients with advanced HIV disease receiving zidovudine for nine months or longer. Three in vivo trials have been initiated to assess possible advantages of combination therapy with zidovudine and interferon alfa in patients with AIDS-related KS. The incidence of serious adverse reactions, therapeutic efficacy, and the rate of emergence of zidovudine-resistant strains of HIV were evaluated. Preliminary results indicate that combination therapy with interferon alfa and zidovudine can safely be administered to patients with AIDS-related KS in doses that elicit antitumor and antiviral responses and discourage the potential emergence of zidovudine-resistant HIV strains.

Expression in yeast of a cDNA clone encoding a transmembrane glycoprotein gp41 fragment (a.a. 591-642) bearing the major immunodominant domain of human immunodeficiency virus

A cDNA clone corresponding to the gp41 gene fragment nucl. 7573-7730 of the human immunodeficiency virus type 1 (HIV-1) was selected from a random HIV-1 genomic library expressed in yeast. This clone encodes a 52-residue long peptide (amino acid (a.a.)) 591-642) bearing the major immunodominant domain (a.a. 598-609) of the HIV-1 transmembrane glycoprotein gp41. Expression of the recombinant peptide pSE-env591-642 was driven by the alpha-mating factor leader sequence contained in a plasmid pSE-x allowing the synthesis and secretion of foreign gene product in Saccharomyces cerevisiae. Time-course analysis of the secretion into culture medium revealed an optimal production of the glycoprotein fragment at 28-30 h with no observable cytotoxicity. The secreted peptide is highly glycosylated with NH2-terminal heterogeneity probably due to different post-translational modifications. The secreted peptide shows an extreme antigenicity since in ELISA assays, as few as 5 microliters/well of crude supernatant are sufficient to obtain a strong detection by monoclonal antibodies or by 100% of sera from HIV-infected individuals. The purified glycopeptide pSE-env591-642 binds to a monoclonal antibody directed against the immunodominant epitope (a.a. 603-609) with an affinity similar to that of the complete glycoprotein gp160 (Kd values within the 10(-10) M range) and with a 100-fold higher affinity than that of a linear peptide fragment SP-env584-609. These results indicate that overexpression in yeast can efficiently provide an abundant source of highly antigenic gp41 protein fragment pSE-env591-642 which retains the antigenic properties of the native gp160 protein. Such a recombinant peptide should therefore be considered as a good candidate for antigen in HIV detection tests.

Expression and purification of p24, the core protein of HIV, using a baculovirus-insect cell expression system

The baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) has been genetically manipulated to yield a recombinant virus capable of expressing p24, the major core protein of HIV-1, in insect cell culture. The expressed product is a p24 protein flanked by short regions of p17 at the amino terminus and p12 at the carboxy terminus. It has been identified and characterized using monoclonal antibodies on Western blots and by amino-terminal sequence analysis. The presence of p24 in the soluble fraction of infected cells following lysis by detergent or sonication, combined with a high level of expression (in excess of 50 mg/l of culture) facilitates the enrichment of large quantities of recombinant HIV antigen in a simple two-step procedure involving ammonium sulphate fractionation and gel filtration. p24 antigen purified in this way is shown to be an efficient diagnostic reagent.

[HIV-1 antigenemia and T-cell activation in HIV-1 infected patients]

In order to study a supposed association between T-cell activation in vivo and HIV-1-antigenemia in HIV-1-infected patients, the detection of p24-antigen in sera was correlated to serum levels of beta-2-microglobulin and C1q-binding immune complexes. Anti-p24-antibodies and the urinary excretion of neopterin were also analysed. In 24 of 80 patients (30%) p24-antigen could be detected, and in 15 of 59 (25.4%) there was a loss of anti-p24-antibodies. Tests revealed elevated serum levels of beta-2-microglobulin in 58 of 80 patients (72.5%), elevated levels of C1q-binding immune complexes in 15 of 66 (22.7%), and increased excretion of neopterin in 52 of 60 (86.7%). Detection of p24-antigen, loss of anti-p24-antibodies, serum levels of beta-2-microglobulin, and urinary excretion of neopterin were significantly correlated to advanced stages of HIV-1 infection. Patients with p24-antigen in the serum showed significantly more frequently elevated serum levels of beta-2-microglobulin and no significant association with increased urinary excretion of neopterin. Because of the high proportion of patients with elevated serum levels of beta-2-microglobulin and increased excretion of urinary neopterin in the absence of detectable p24-antigen in serum, we could not correlate HIV-1-antigenemia to T-cell activation in vivo.

HIV associated arthropathy: HIV antigen demonstration in the synovial membrane

Light and electron microscopic studies were performed on the synovial membranes of 5 patients with HIV associated arthropathy. An immunoperoxidase technique with the use of monoclonal antibodies against CD4, CD8, B and DR lymphocytes, and HIV p24 antigen was also used. Mild to moderate nonspecific proliferative changes and increased vascularity of the subsynovial space were seen. Electron dense deposits and viral-like particles were not observed. Immunohistochemical staining revealed HIV p24 positive staining in cells of the synovial lining layer and in the mononuclear cells of the subsynovial space. CD4, CD8, with predominance of CD8, and B and DR cells were also present. The presence of HIV p24 antigen may be indicative of a role, yet to be defined, in the pathogenesis of HIV associated rheumatic disorders.

Removal of HIV antigens and HIV-infected cells in vitro using immunomagnetic beads

Human anti-HIV antibody-coated magnetic beads and magnetic particle concentrators were used to eliminate HIV antigens and the infected cells in vitro. Fifty micrograms/ml of the antibody coated on 30 mg/ml of tosyl-activated beads, and 10 min of reaction time between the antigens and the immunobeads were sufficient to eliminate the virus antigens from phosphate buffered saline, serum and peripheral blood. HIV-infected cells were eliminated in vitro, but not completely. This method will be useful in eliminating viral antigens and infected cells from clinical material such as blood and blood products.

An assay for quantifying infectious HIV particles

A method for assessing the number of infectious particles in preparations of HIV has been developed. Virus was mixed with cells to allow binding of virus. The cells were then cast in an agar gel to block any further transfer of virus between the cells. After 4 days of incubation the cells initially infected with HIV expressed viral antigens. The percentage of infected cells was then determined by indirect immunofluorescence. The method was developed for HIV, but is presumably suitable for any virus that can replicate in cells not attached to a surface.

Comparative study with in situ hybridization and immunocytochemistry in detection of HIV-1 in formalin-fixed paraffin-embedded cell cultures

The sensitivities of three immunohistological techniques were compared in this study for detecting human immunodeficiency virus (HIV-1) in infected cultured human lymphocytes that had been formalin-fixed and paraffin-embedded. The techniques included in situ hybridization (ISH) with HIV-1 cDNA; immunocytochemistry with HIV-1 p24 monoclonal antibody (ICC-m); and immunocytochemistry with HIV-1 polyclonal antibody from a patient with acquired immunodeficiency syndrome (AIDS) (ICC-p). Procedures were optimized for enzyme digestion and for antibody reaction conditions. HIV-1--infected cells and noninfected control cells were tested. Noninfected controls were uniformally negative by all three methods. Infected cells had the highest positivity rate by the ISH method (p less than or equal to 0.0001), and the ICC-p method was more positive than the ICC-m (p less than or equal to 0.0001). Both the ICC-p and the ICC-m techniques were more positive with the cocultivated cell cultures than the ISH, which was more sensitive with the infected continuous cell line (P less than or equal to 0.0001). The ICC-p method had a lower standard deviation on positive results than either the ICC-m or ISH method. The variability observed with these test procedures, reagents, and specimens suggests that these are important technological parameters in detecting p24, with implications for detecting other HIV-1 markers in infected tissues.

Human immunodeficiency virus type 1 detected in all seropositive symptomatic and asymptomatic individuals

Between February 1987 and October 1988, peripheral mononuclear blood cells (PBMC) from 409 adult individuals antibody positive by Western (immuno-)blot for human immunodeficiency virus type 1 (HIV-1) (56 acquired immunodeficiency syndrome [AIDS] patients, 88 patients with AIDS-related complex, and 265 asymptomatic individuals) were consecutively cultured for HIV-1 or tested for the presence of HIV-1 DNA sequences by a polymerase chain reaction assay (PCR). We isolated HIV-1 or detected HIV-1 DNA sequences from the PBMC of all 409 HIV-1 antibody-positive individuals. None of 131 healthy HIV-1 antibody-negative individuals were HIV-1 culture positive, nor were HIV-1 DNA sequences detected by PCR in the blood specimens of 43 seronegative individuals. In addition, HIV-1 PCR and HIV-1 culture were compared in testing the PBMC of 59 HIV-1 antibody-positive and 20 HIV-1 antibody-negative hemophiliacs. Both methods were found to have sensitivities and specificities of at least 97 and 100%, respectively. In contrast, the sensitivities of serum HIV-1 antigen testing in AIDS patients and asymptomatic seropositive patients were 42 and 17%, respectively. Our ability to directly demonstrate HIV-1 infection in all HIV-1 antibody-positive individuals provides definitive support that HIV-1 antibody positivity is associated with present HIV-1 infection. Moreover, the sensitivities and specificities of PCR and culture for the detection of HIV-1 appear to be equivalent, and both methods are superior to testing for HIV-1 antigen in serum for the direct detection of HIV-1.

Comparison of particulate 3,3',5,5'-tetramethylbenzidine and 3,3'-diaminobenzidine as chromogenic substrates for immunoblot

In horseradish peroxidase (EC: 1.11.1.7)-dependent immunoblot assays, particulate 3,3',5,5'-tetramethylbenzidine (TMB) is shown to be a more efficient immunoblot substrate than the standard substrate 3,3'-diaminobenzidine (DAB), because TMB is easily prepared, stable, and less carcinogenic than is DAB. Assays of antibody in a serially diluted human immunodeficiency virus (HIV) control serum (CDC reference CAT# VS2151) have the same sensitivity limits with both DAB and TMB (1:312,500). Complete, working substrate solutions of H2O2/TMB/enhancer and of H2O2/DAB were stored at room temperatures and at 48 degrees C respectively. Periodic tests showed the TMB substrate system to be functional after four weeks at 48 degrees C and after eight weeks at room temperature, while the DAB system was functional after one week at 48 degrees C and after four weeks at room temperature. The stability, safety, and convenience of the commercially available TMB kits make this substrate ideal for immunoblot tests.

A novel method for the purification of HIV-1 p24 protein from hybrid Ty virus-like particles (Ty-VLPs)

The self-assembly properties of a protein encoded by the yeast retrotransposon Ty can be exploited to produce large amounts of recombinant, particulate fusion proteins as hybrid Ty virus-like particles (Ty-VLPs). This system has now been adapted to allow the release of the additional protein by incorporation of a protease cleavage site between the yeast carrier protein and the protein of interest. The purification of the additional protein is facilitated by exploiting the ease with which Ty-VLPs can be purified from other yeast cell components due to their particulate nature. We have used this modified system to produce hybrid particles containing the HIV-1 p24 protein downstream of the recognition sequence for the blood coagulation factor Xa. The p24 was released from the particles by proteolytic cleavage and rapidly separated from the residual particulate material using centrifugation and standard chromatography techniques. This procedure has been used to purify milligram quantities of HIV-1 p24 protein that reacts with anti-p24 sera and elicits the production of p24-specific antibodies in experimental animals.

Isolation of recombinant partial gag gene product p18 (HIV-1Bru) from Escherichia coli

The membrane-associated structural protein, p18, of the human immunodeficiency virus (HIV-1), has been expressed in Escherichia coli. The recombinant protein was purified by cation-exchange chromatography on S Sepharose followed by cation-exchange high-performance liquid chromatography (HPLC) on Sulfoethyl Aspartamide. The isolation of 28.7 mg of recombinant p18 from 16.71 of cell culture represents an overall yield of ca. 20%. Recombinant p18 was characterized by sodium dodecyl sulphate polyacrylamide gel electrophoresis, reversed-phase HPLC, amino acid composition and amino acid sequence analysis of the N-terminus. Edman degradation of peptides generated by trypsin or Staphylococcus aureus V8 proteolytic digestion, including the C-terminus, confirmed the amino acid sequence to be that predicted from the cDNA. A C-terminally cleaved form of recombinant p18, p18LM, was separated in the cation-exchange HPLC step and was partially characterized in parallel with the intact molecule. By Western blotting it was shown that recombinant p18 in addition to the cleaved form p18LM is recognized by a monoclonal antibody which was generated against the natural protein from HIV-1.

Evaluation of three enzyme immunoassays for HIV-1 antigen detection

Three enzyme immunoassay (EIA) methods for the detection of human immunodeficiency virus (HIV-1) were evaluated. Serum or plasma samples from 22 individuals seropositive for HIV-1 antibodies were tested with the Abbott, Coulter, and DuPont kits for presence of HIV-1 p24 antigen. Another 12 samples were tested with two kits only. Discordant results were obtained with 9 of 34 (26%) HIV-1-antibody-positive patient samples tested. Most of these discrepancies were found in samples containing less than 30 pg/ml of HIV-1 p24 core antigen. A sampling of sera from normal blood donors and patients with infectious or autoimmune diseases revealed a low level of false positive reactions, especially with sera containing antinuclear antibodies or rheumatoid factor. Noteworthy is the frequency of false positive reactions seen with the DuPont EIA for HIV-1 p24 antigen. 18/111 sera (16.2%) containing auto-antibodies tested positively with the DuPont HIV-1 p24 antigen EIA. The nonspecific nature of the test reactivity for 9/10 of these samples was confirmed using an HIV-1 p24 antigen inhibition assay. These findings are discussed in light of the need for HIV-1 antigen detection in the clinical laboratory and of other methods for HIV-1 detection: the polymerase chain reaction and measurements of reverse transcriptase activity.

Virologic and serologic aspects of human immunodeficiency virus infection in infants and children

Serologic diagnosis of HIV infection in infants and children is made especially difficult by the universal presence of maternal antibodies in blood during the first year of life, technical difficulties associated with the measurement of virus-specific IgM antibodies (except, perhaps, when the mother and, hence, the child have been very recently infected), and the weaker and more limited antibody reactivities revealed by Western blot analysis. Infants in the first year of life who develop reactivities on a Western blot that are different from those of their mothers are almost certainly infected. In addition, infants whose lymphocytes can be stimulated in vitro to produce HIV-specific antibodies of both the IgG and IgM isotypes and whose viral-specific antibodies can be found in the IgG3 subclass are also likely to be infected. Finally, children older than 15 months of age who remain seropositive by Western blot and who have both clinical and immunologic abnormalities consistent with HIV infection are also, doubtlessly, infected.

Increased detection of human immunodeficiency virus antigen carriers by simultaneous assay of plasma and extracts from resting and phytohaemagglutinin-stimulated peripheral blood mononuclear cells

Antigenaemia due to human immunodeficiency virus (HIV) is thought to be significant either before the appearance of a specific antibody response, or after its decline during terminal stages. In order to increase the rate of detection of HIV antigen carriers, regardless of the stage or despite the presence of specific serum antibodies, we assayed, simultaneously, plasma samples and extracts from resting and phytohaemagglutinin-stimulated mononuclear cells from 25 infected, anti-body-positive individuals and 10 healthy, antibody-negative female volunteer blood donors. We detected the presence of HIV antigen in at least one of the three types of specimens obtained from all the 25 infected subjects but in none of the 10 healthy blood donors. This approach might prove most useful for the study of patients with controversial or equivocal antibody test results.

Decline in CD4+ cell numbers reflects increase in HIV-1 replication

Changes in CD4+ cell numbers were studied in relation to the presence of HIV-1 antigen (HIV-1-Ag) in serum from homosexual men followed prospectively. During 30 months of follow-up the mean CD4+ cell number (x 10(9) per liter) was stable in 134 at entry HIV-1 antibody (HIV-1-Ab) seropositives, who remained HIV-1-Ag negative (from 0.59 to 0.62) and declined in 38 at entry HIV-1-Ab seropositives who were persistently HIV-1-Ag positive (from 0.43 to 0.34). In sera of 9 of 65 HIV-1-Ab seroconverters HIV-1-Ag was detected only once, 3 months before or concomitantly with antibody seroconversion. Another 11 men became persistently HIV-1-Ag positive with antibody seroconversion or 2-6 weeks thereafter. A decline in CD4+ cell numbers was seen between 6 months before and the moment of HIV-1-Ab seroconversion, independently of duration and level of antigen expression. This indicates initial HIV-1 replication in both HIV-1-Ag negatives and positives. Following antibody seroconversion, HIV-1-Ag negatives had higher CD4+ cell numbers than HIV-1-Ag positives. Similarly to those who were HIV antigenemic from entry of the study, the HIV-1-Ab seroconverters who concomitantly with seroconversion or shortly thereafter became HIV-1 antigenemic showed a steady and significant (p = 0.01) decline in CD4+ cell numbers. In those who remained HIV-1-Ag negative after antibody seroconversion, CD4+ cell numbers were stable during follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell-mediated immune response toward viral envelope and core antigens in gibbon apes (Hylobates lar) chronically infected with human immunodeficiency virus-1

The specific cellular immune response toward envelope and core proteins of human immunodeficiency virus-1 (HIV-1) was investigated in gibbon apes chronically infected with the HTLV-IIIB isolate. After in vitro stimulation of PBMC from infected and control animals with HIV-1 Ag, DNA synthesis, IL-2R expression and IL-2 release were assayed. Cells from infected gibbon apes demonstrated a group-specific response toward whole virus preparations from three divergent HIV-1 isolates (HTLV-IIIB, HTLV-IIIRF, HTLV-IIIMN). Consistent responses were also detected against purified HIV-1 Ag, i.e., native gp120 envelope glycoprotein, recombinant gp160 glycoprotein, a synthetic peptide (peptide 7) representing a highly conserved region of gp120, and purified native core protein p24. In addition, lymphocytes from infected gibbon apes displayed a specific, MHC-restricted, cytotoxic activity against autologous cells expressing HIV-1 envelope or gag proteins. The specific T cell reactivity toward HIV-1 proteins observed in infected gibbons contrasts with findings in HIV-1 infected humans, and may help to explain the apparent discrepancy in the natural history of the infection between the two species.

A simple assay based on HIV infection preventing the reclustering of MT-4 cells

This report confirms and extends the recent work of Pauwels et al. on a "reclustering" assay (a simple microtitration plate method) for the determination of human immuno-deficiency virus (HIV) infection of MT-4 cells. MT-4 cells, which are highly susceptible to and permissive for HIV, typically grow in clusters. In the absence of virus these cell aggregates, after dissociation by pipetting, reform into clusters within 2 to 3 hours. Growth of HIV results in an inhibition of reclustering, with an end-point some 4-5 days after initiation of infection. In cultures inoculated with 5 to 8 TCID(50) of HIV, only 2-4% of the cells remain viable after 4 days. Correspondingly, HIV antigens can be detected by immunofluorescence in more than 90% of the cells remaining in the culture. The sensitivity of the "reclustering" assay is only slightly less than that of the immunofluorescence test. A colorimetric assay is also described that employs a tetrazolium salt (designated as MTT) to measure the cytolytic effect of various dilutions of HIV; comparable virus titres were obtained. This reclustering assay now appears to offer the simplest method for titration of prototype HIV in virus stocks and when used in drug evaluation tests and for measurement of HIV neutralizing antibodies.