Anti-p24 Antibody Research Articles

Phospholipid Interactions of a Peptide from the Fusion-Related Domain of the Glycoprotein of VHSV, a Fish Rhabdovirus

Previous studies mapped a p2 domain (aa 82–109) which binds phosphatidylserine (PS) (Estepa and Coll, 1996a) and contains three contiguous hydrophobic amino acid heptad repeats followed by a positively charged stretch (Coll, 1995b) in the glycoprotein G of the viral hemorrhagic septicemia virus (VHSV), a fish rhabdovirus. Anti-p2 antibodies inhibited low-pH VHSV-induced fusion (Estepa and Coll, 1997) and low-pH PS binding to VHSV (Estepa and Coll, 1996a). We report here further studies on the interaction of the synthetic peptide p2 with phospholipid vesicles. The synthetic p2 peptide was able to mediate aggregation, lipid mixing, and leakage of contents only with negatively charged phospholipid vesicles and in a concentration-dependent manner. As shown by its effect on lipid phase transitions deduced from data with fluorescence polarization and differential scanning calorimetry, the p2 peptide becomes inserted into the hydrophobic negatively charged phospholipid vesicle bilayers. In addition, data based on circular dichroism showed that the p2 peptide folds as a structure with a high content of β-sheets stabilized by interaction with anionic phospholipids. These studies are potentially relevant to viral fusion in VHSV.

Immunologic cross-reaction between HIV type 1 p17 and Mycoplasma hyorhinis variable lipoprotein.

Monoclonal antibodies directed against the HIV-1 matrix protein p17 that react with a component present on the surface of HIV-1-infected cells have previously been described. In this study we show that one of these monoclonal antibodies binds to persistently HIV-1-infected cell lines that are coinfected with Mycoplasma hyorhinis, but not to cell lines that are uninfected with mycoplasma. Mycoplasma-infected cells secrete HIV-1 at a higher rate, have a slight increase in cell surface expression of gp120 and gp41, and are less sensitive to immunotoxins than uninfected cells. The anti-p17 antibody binds to a protein of M. hyorhinis grown in cell-free culture. The variable expression and size of the protein among strains is typical of the variable lipoprotein (Vlp) system of M. hyorhinis. Confirmation of the reactivity of the antibody with a Vlp was provided by demonstrating its specific binding to recombinant VlpF expressed in E. coli, and to a synthetic peptide representing the carboxy-terminal region of VlpF, but not to other recombinant Vlp products or peptides. This is a true cross-reaction because the antibody also binds to recombinant p17 expressed in E. coli and the binding is inhibited by the VlpF peptide. These analyses highlight the potential of mycoplasma contamination of tissue culture cell lines to cause anomalous results. With regard to HIV-1, mycoplasma infection of cells results in increased rates of virus secretion, and introduces a potential confounding immunologic cross-reaction as well. The existence of a cell surface form of p17 is unlikely.

HIV p17 enhances lymphocyte proliferation and HIV-1 replication after binding to a human serum factor.

To analyse the role of recombinant HIV-1 protein p17 in the modulation of cell activity. Peripheral blood mononuclear cells (PBMC) obtained from healthy donors were cultured in the presence or absence of p17 with mitogens such as phytohaemagglutinin or interleukin-2 and their response assayed by cell proliferation. Cross-linking experiments were employed to investigate the presence of a binding between p17 and factor(s) present in human serum. An immunoenzymatic assay for p24 antigen detection was used to analyse the effect of the addition of exogenous p17 to cultures of PBMC infected with HIV-1 in vitro. Purified recombinant p17 protein at a concentration of 0.25 microg/ml significantly increased the proliferation of preactivated PBMC obtained from healthy donors. This effect was obtained by binding p17 to factor(s) present in human serum and observed on both CD4+ and CD8+ T cells. Recombinant p17 also induced an increased rate of HIV-1 replication, probably due to enhanced T-cell proliferation. The activity of p17 protein was inhibited by anti-p17 antibodies generated by injecting recombinant p17 in rabbits, but not by human antibodies generated during the natural course of HIV infection. Characterization of the human factor(s) and identification of the interacting p17 epitope(s) will improve our understanding of the mechanisms used by HIV to efficiently replicate in our organisms.

Patterns of in VitroAnti-Human Immunodeficiency Virus Type 1 Antibody Production in Long-Term Nonprogressors

With the aim of evaluating the specific pattern of in vitroantibody production (IVAP) in human immunodeficiency virus type 1 (HIV-1)-infected long-term nonprogressors (LTNPs), we tested 20 subjects who had remained asymptomatic for more than 8 years with a CD4 +cell count higher than 500/μl and 59 patients at different stages of HIV-1 infection as controls. In cell cultures, IVAP was detected in 14 out of 20 LTNPs (70%), in 5 out of 6 recent seroconverters (83%), and in all the other control patients. Anti-p24 antibody production was significantly lower in LTNPs than in asymptomatic patients with a more recent infection. Recent seroconverters and patients with AIDS did not produce anti-p24 antibodies ( P= 0.02). Anti-gp160 antibodies were produced by peripheral blood mononuclear cells from LTNPs in 12/20 cases. CD4 +cell count was significantly higher in IVAP-negative than in IVAP-positive LTNPs ( P= 0.013), while the viral load was not significantly different. Specific anti-HIV-1 antibody production did not seem to be a correlate of long-term nonprogression.

Molecular Basis for the Binding Promiscuity of an Anti-p24 (HIV-1) Monoclonal Antibody

Multiple binding capabilities utilized by specific protein-to-protein interactions in molecular recognition events are being documented increasingly but remain poorly understood at the molecular level. We identified five unrelated peptides that compete with each other for binding to the paratope region of the monoclonal anti-p24 (HIV-1) antibody CB4-1 by using a synthetic positional scanning combinatorial library XXXX[B 1,B 2, B 3,X 1,X 2,X 3]XXXX (14 mers; 68,590 peptide mixtures in total) prepared by spot synthesis. Complete sets of substitution analogs of the five peptides revealed key interacting residues, information that led to the construction of binding supertopes derived from each peptide. These supertope sequences were identified in hundreds of heterologous proteins, and those proteins that could be obtained were shown to bind CB4-1. Implications of these findings for immune escape mechanisms and autoimmunity are discussed.

Characterization of one monoclonal antibody against feline immunodeficiency virus p24 and its application to antigen capture ELISA

Several monoclonal antibodies (mAbs) were produced against feline immunodeficiency virus (FIV) p24 capsid antigen. One of these, F2710, reacted strongly, not only with viral p24 and recombinant p24, but also with p50 Gag precursor protein in Western blot. Epitope mapping analysis revealed that mAb F2710 recognizes a heptapeptide, SFIDRLF, in the FIV p24 amino acid sequence. As this portion of FIV p24 is highly conserved among various FIV strains, the rnAb seems to be a useful tool for detecting FIV p24 antigen in various samples. By means of this mAb and rabbit anti-p24 polyclonal antibody, an antigen capture ELISA was developed. The ELISA detected viral p24 antigen with good linearity. The lower detection limit of this assay is 40 pg/ml of recombinant p24 antigen, which is at least as sensitive as the reverse transcriptase assay in detecting FIV virion. Thus, this system is valuable for monitoring FIV replication in vitro.

Streptococcus sanguis expresses a 150-kilodalton two-domain adhesin: characterization of several independent adhesin epitopes.

Streptococcus sanguis binds to saliva-coated hydroxylapatite (sHA), an in vitro model of the enamel pellicle. To learn if more than one adhesin functions during adhesion, 12 reactive monoclonal antibodies (MAbs) were isolated by screening against both adhesive and nonadhesive strains. Two of these MAbs, 1.1 and 1.2, inhibited adhesion in a dose-dependent fashion, although maximum inhibition with either was only 37%. When these two MAbs plus a polyclonal antibody to P1-like adhesin were combined, the inhibition was additive to about 82%. These data indicated that there were at least three distinct, functional adhesion epitopes on the surface of S. sanguis. Western blot analyses of S. sanguis surface macromolecules showed antigens at 36 and 56 (with MAb 1.2), 87 and 150 (with both MAb 1.1 and MAb 1.2), and 100, 130, and 170 kDa (with anti-P1 antibody). The antigens were eluted from gels. Isolated antigens and corresponding antibodies inhibited adhesion similarly. Additivity experiments suggested the distinct epitopes were in three groups: (i) 36/56 kDa, (ii) 87/150 kDa, and (iii) 100/130/170 kDa. The 150-kDa antigen reacting with both MAbs was isolated from gels and digested with trypsin. The digestion revealed a series of tryptic bands. A band at 38 kDa reacted with MAb 1.1 whereas a band at 54 kDa reacted with MAb 1.2 in Western blot analysis, indicating two distinct adhesive epitopes on the 150-kDa antigen. These data strongly suggest that S. sanguis adhesion to sHA is maximized when several adhesin epitopes are coexpressed on surface antigens of different sizes.

Monoclonal antibodies to P24 and P61 immunodominant antigens from Nocardia brasiliensis.

We prepared a Nocardia brasiliensis cell extract and purified two immunodominant antigens with molecular weights of 61,000 and 24,000. The isolated proteins were shown to be reasonably pure when analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (8 to 18% polyacrylamide gradient) and stained with Coomassie blue and silver nitrate. By using an immunoelectrotransfer blot method (Western blotting), we demonstrated that these two purified proteins reacted strongly with serum from N. brasiliensis-infected mycetoma patients. To obtain anti-P61 and anti-P24 monoclonal antibodies (MAbs), we used an N. brasiliensis cell extract as the antigen for the first immunization; 2 weeks later female mice were reimmunized with a semipurified antigen containing the P24 or P61 fraction. A booster injection was given 3 days before the fusion was carried out. Two hybrids that reacted strongly with P24 were cloned by limiting dilution, the generated MAbs were analyzed for isotyping, and their specificity was tested in a Western blot assay with cell extracts from Nocardia asteroides and Mycobacterium tuberculosis cultures. Anti-P24 MAbs were shown to be specific for N. brasiliensis HUJEG-1 and did not cross-react with either the N. asteroides or M. tuberculosis strains used. However, additional studies with several N. asteroides and N. brasiliensis strains are needed to investigate whether there are cross-reactions between strains or species when these MAbs are used. The anti-P61 and anti-24 MAbs were used to locate the antigen in N. brasiliensis cells by immunofluorescence. The lack of reaction with intact cells suggests that the P24 and P61 antigens are not exposed in the complete bacterial cell surface or that the recognized epitopes are different. Only one anti-P61 MAb that reacted specifically with the N. brasiliensis cell extract was obtained.

Antibodies to the HIV-1 p17 Protein Cross-React with Human Superoxide Dismutase-2

Antibodies reacting with thegagprotein 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.

BCell Superantigens in HIV-1 Infection

HIV-1 infection affects many of the cellular components vital for the maintenance of immune homeostasis. Similar to the T cell superantigen effect on T cell expansion and depletion in AIDS, HIV components with B cell superantigenic properties could be responsible for the observed B cell activation and skewing of VH family usage. Current data on possible B cell superantigen properties of HIV proteins (gp120) are mostly based on studies describing the clonality and VH family usage of immunoglobulins in HIV infection. Various laboratories reported independently an unusual skewing of the VH-repertoire of antibodies that appears not to be random. According to these observations, an enrichment of VH 1 and VH4 family - paralleled a depletion of VH3 family - utilizing anti-HIV-1 gp120 and p24 antibodies in HIV-1 infected individuals and a loss of total VH3+ Ig in patients with late stages of AIDS. Polyclonal and monoclonal (VH1, VH4, and VH5) anti-p24 and gp120 antibodies share a crossreactive idiotype (IF7). IF7 like antibodies were found in the serum of HIV-1 infected individuals, persisting in the course of infection, perhaps contributing to the depletion of VH3+ Ig. Furthermore, a restriction of clonal heterogeneity of anti-p24 and anti-gp120 antibodies was detected by isoelectric focusing and indicated by skewed kappa/lambda light chain isotype ratios, indicating clonal dominance of certain sets of anti-HIV-1 antibodies during infection. Taken these findings together, a strong case for the involvement of a B cell superantigen can be made, although the mechanism of B cell depletion is not fully understood.

Lack of predictive value for progression of dissociated circulating P24 antigen in human immunodeficiency virus type 1-infected black patients.

In human immunodeficiency virus type 1 (HIV)-1-infected Black people, the circulating p24 antigen is hidden frequently in immune complexes, because of high titers of serum anti-p24 antibodies. In order to evaluate the prognostic values for progression of free and dissociated serum p24 antigen in Black people, sera from 45 HIV-1-infected Black patients, all at non-AIDS stages, were evaluated prospectively for p24 antigen by several assays; circulating free p24 antigen was measured by immunocapture ELISA only (method 1) and with ELAST amplification (method 2), and dissociated p24 antigen determined after glycine-HCl pretreatment of serum, by immunocapture ELISA only (method 3) and with ELAST amplification (method 4). Serum CD4 and CD8 cell counts, beta 2-microglobulin, and total IgA were determined also at least twice a year. Clinical events for AIDS were those included in the 1986 CDC classification for HIV infection. At entry, p24 antigen was found in 3 (6.7%) patients by method 1, in 7 (15.6%) by method 2, in 14 (31.1%) by method 3, and in 22 (48.9%) by method 4. Methods 3 and 4 were more sensitive than method 1 (P < 0.001) and method 2 (P < 0.001). The mean follow-up was 30 months. The free symptom survival times (mean +/- SD months) were significantly lower in patients being p24 antigen positive by method 1 [(+) 33 +/- 27 vs. (-) 61 +/- 15, P = 0.03), but they were similar in patients positive and in those negative for p24 antigen determined by method 2 [(+) 71 +/- 17 vs. (-) 74 +/- 9, P = 0.54], method 3 [(+) 76 +/- 12 vs. (-) 69 +/- 13.2, P = 0.80], and method 4 [(+) 79 +/- 9 vs. (-) 63 +/- 7, P = 0.71]. At 24 months, p24 antigen positivity did not correlate either with CD4 or CD4/CD8 slops, nor with beta 2-microglobulin or IgA variations. By contrast, a CD4 cell count below 200/mm3 at entry was significantly associated with disease progression. In conclusion, dissociated p24 antigenemia does not appear as a useful surrogate marker for progression in HIV-1-infected Black people.

Phosphatidylserine binding to solid-phase rhabdoviral peptides: a new method to study phospholipid/viral protein interactions.

A new method is described for the study of phosphatidylserine binding to rhabdoviral peptides by using solid-phase assays. This new assay could probably be extended to study the interactions between host membrane phospholipid and viral proteins in other viruses. By using labeled and hydrated phosphatidylserine (PS), PS-binding to solid-phase 15-mer peptides (pepscan) could map putative phospholipid-binding regions of the glycoprotein G of viral haemorrhagic septicaemia virus (VHSV), a salmonid rhabdovirus. The major PS-binding region of 27 aa (aa82-109, p2) did not only bind PS, but also phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Extraction of the PS bound to solid-phase p2 by a variety of chemical compounds and competition experiments with several phospholipid-related compounds showed that PS-Binding to p2 was dependent on not only hydrophobic, but also ionic interactions, as suggested by prior work on phospholipid interactions in other rhabdoviruses. Saturation/competition experiments with labeled and cold PS, PE and PC also showed that the reaction probably takes place between high molecular weight aggregates of hydrated phospholipids and several molecules of solid-phase p2. This assay has been used previously to detect hydrophobic amino acid heptad-repeats in rhabdoviruses and when anti-p2 antibodies to VHSV were obtained they were capable of inhibiting VHSV-induced cell to cell fusion.

Prevalence of Borna disease virus RNA in peripheral blood mononuclear cells from blood donors.

The presence of Borna disease virus (BDV) in peripheral blood mononuclear cells (PBMC) of 100 blood donors from Sapporo and 72 blood donors from Tokyo was examined using nested reverse transcriptase/polymerase chain reaction amplification with specific-primers for BDV p24. Anti-BDV p24 antibodies in the plasma of the 100 blood donors from Sapporo also were studied by enzyme-linked immunosorbent assay and by Western blot. BDV RNA was detected in 3 (4.2%) of the 72 PBMC samples from Tokyo, and in 5 (5%) of the 100 PBMC samples from Sapporo. In contrast, anti-p24 antibodies were found in only 1 (1%) of the donors from Sapporo. These results suggest that BDV infection in humans may be more widespread than previously thought.

Serum anti-p24 antibody concentration has a predictive value on the decrease of CD4 lymphocyte count higher than acid-dissociated p24 antigen.

We studied the prognostic value on the decrease of CD4 lymphocyte count of anti-p24 antibody (ab) titer and compared this value with that of polyclonal and monoclonal p24 (ag) titer before and after immune complex dissociation (ICD); 53 human immunodeficiency virus (HIV)-infected patients having CD4+ counts above 400/mm3 when first examined were followed up over a 3-year period including at least four visits; HIV disease progressors (n = 18) were defined as having CD4+ counts below 200/mm3 and non-progressors (n = 35) as having CD4+ counts still above 400/mm3 at the end of follow-up. Sera were collected at each visit and assayed for p24 ag with and without ICD and for anti-p24 ab titer. The mean anti-p24 ab titer of progressors and of non-progressors at entry was significantly different. A threshold of anti-p24 ab titer indicating a HIV progression was determined at 1/300. The proportion of individuals with an anti-p24 ab titer lower than 1/300 at least once during the study period was 34% in non-progressors and 94% in progressors. The difference between progressors and non-progressors at entry was significant with monoclonal p24 ag without ICD and more significant with monoclonal p24 ag after ICD. The marker having the highest predictive value was the anti-p24 ab titer, then monoclonal p24 ag with ICD, then polyclonal p24 ag with ICD. Anti-p24 ab is an earlier and stronger marker of the decrease of CD4 lymphocyte count than p24 ag even after ICD.

Schwangerschaften bei HIV-infizierten Frauen in der Schweiz*

In a national multicentre study, 229 pregnancies in 219 HIV-positive women were prospectively followed up between January 1, 1990, and October 30, 1993. 69.8% were infected by intravenous drug abuse and 91.5% were asymptomatic (CDC classes II and III) in early pregnancy. 48 (21.0%) were first discovered to be HIV-infected during the index pregnancy: 46 of these had risk factors. The present epidemiologic development does not seem to warrant a general HIV-screening in pregnancy at this time. 71 pregnancies (31%) were terminated; 158 children were born, 17 (23.3%) of the 73 definitely classified are HIV-infected. An asymptomatic HIV infection with a sufficiently high (> 200/microliters) CD4 cell count has no proven influence on the pregnancy. Otherwise, however, maternal infectious diseases can lead to prematurity. For mothers with i.v. drug abuse, there is a significantly higher incidence of prematurity and fetal growth retardation. The maternal HIV infection can be transmitted to the child either during pregnancy or at delivery. The incidence of vertical transmission in our study was 23.3%; the most predictive parameter for a prenatal HIV transmission is a low anti-p24 antibody titre. The risk of intrapartum transmission seems to be somewhat, but not significantly, reduced for primary Caesarean sections. Recently, prophylaxis with Zidovudin during pregnancy, beginning after the 14th GW, was found to reduce vertical HIV-transmission by 66%. Since the virus can also be transmitted through mothers' milk, HIV-positive mothers should not nurse their babies. Maternal infections are significantly more frequent in HIV-positive women, and are a risk factor for prematurity.(ABSTRACT TRUNCATED AT 250 WORDS)

The Possible Involvement of DNA-Dependent Protein-Kinase in the Phosphorylation of P1 Protein in Cell-Free DNA-Replication Xenopus Eggs

We prepared two types of antibodies: one directed against an oligopeptide corresponding to the C-terminal portion of P1 protein and the other against an oligopeptide corresponding to the C-terminal portion of the 80-kDa subunit of the Ku antigen (p80 Ku) essential for DNA-dependent protein kinase (DNA-PK) activity. Immunoprecipitation and immunoblot of sperm nuclei preincubated in Xenopus egg extracts by anti-P1 antibody showed that Xenopus P1 protein is a phosphoprotein with two phosphorylated forms: a hyperphosphorylated form extractable with Triton X-100 and a hypophosphorylated form resistant to Triton X-100. The immunodepletion of extracts with anti-p80 Ku IgG-bound beads caused the hyperphosphorylated form to disappear but hardly affected the hypophosphorylated form of Fl protein. DNA replication was stimulated by immunodepletion of the extract with anti-p80 Ku IgG-bound beads. These findings suggest that DNA-PK down-regulates DNA replication through inhibition of hyperphosphorylation of P1 protein during S phase in this cell-free system.

Assay of HIV-1 protease activity by use of crude preparations of enzyme and biotinylated substrate

An enzyme immunoassay was developed for monitoring protease reactions of human immunodeficiency virus (HIV). The protease and its substrate, the gag precursor, were generated separately in Escherichia coli. The HIV-1 protease was generated with a glutathione-S-transferase expression system and the gag substrate, named Pin17/24, was prepared with a PinPoint expression system. Pin17/24 consists of an N-terminal peptide, which is biotinylated in E. coli, fused with a C-terminal peptide that contains a protease cleavage site flanked by p17 and p24 segments. Through its biotin in the N-terminal region, Pin17/24 bound to ELISA plates coated with avidin, whereas through its C-terminal region, the same molecule of Pin17/24 could be recognized by an anti-p24 monoclonal antibody. When the protease was added to Pin17/24, the p24 fragment was released from the biotinylated fusion protein and could no longer be retained on the avidin plates, and as a result, binding of the anti-p24 monoclonal antibody decreased. The binding was specific and the reaction was inhibited by a known HIV protease inhibitor. Due to the specific interactions between avidin and biotin, monoclonal antibody and antigen, and the HIV protease and the gag substrate, crude preparations of these reagents can be used readily in the assay. The simplicity and feasibility of this method should be useful for simultaneous monitoring of many enzyme reactions, particularly for screening possible HIV protease inhibitors.

FIV infection of macrophages: in vitro and in vivo inhibition by dideoxycytidine 5′-triphosphate

We have evaluated in vitro and in vivo whether it is possible to protect cat macrophages from feline immunodeficiency virus (FIV) infection by the administration of dideoxycytidine 5′-triphosphate (DDCTP). Since cell membranes are impermeable to phosphorylated drugs we have encapsulated DDCTP into autologous erythrocytes and modified erythrocyte membranes to target these drug-loaded cells to macrophages. DDCTP-loaded erythrocytes reduced FIV production by macrophages infected in vitro or obtained from naturally or experimentally infected cats. The same treatment protected the majority of peritoneal macrophages during a 7 month experimental FIV infection and reduced the percentage of circulating lymphocytes stained with an anti-p24 antibody. These results suggest that the administration of nucleoside analogues in phosphorylated form is feasible and their targeting to macrophages reduces FIV infection in vitro and in vivo.

Renal involvement in feline immunodeficiency virus infection: p24 antigen detection, virus isolation and PCR analysis

Renal alterations characterized morphologically by glomerular and tubulo-interstitial lesions and clinically by a heavy proteinuria and sometimes by renal failure are frequent in feline immunodeficiency virus (FIV) infected cats. To investigate the possible role of local FIV replication in the genesis of this renal damage, renal tissues of 15 consecutive naturally infected and five non-infected cats were examined for traces of the virus by immunohistochemistry, using a monoclonal anti-p24 antibody in a streptavidin-biotin peroxidase labeled system, cultivation and polymerase chain reaction (PCR). Tubular epithelial cells as well as scattered interstitial inflammatory and glomerular cells were positive for p24 antigen in 13 cats. Viral isolation was successful in seven cats, and FIV gag DNA and RNA sequences were detected in 14 and five cats, respectively. Control cats were constantly negative. Although not conclusive, these results suggest that a direct role of FIV in the induction of the renal damage observed in infected animals is possible.

Passive immunotherapy in AIDS: a double-blind randomized study based on transfusions of plasma rich in anti-human immunodeficiency virus 1 antibodies vs. transfusions of seronegative plasma.

A randomized double-blind controlled trial was conducted to determine the efficacy of passive immunotherapy in the treatment of symptomatic human immunodeficiency virus (HIV) infection. This trial included 86 symptomatic patients randomized to receive plasma rich in anti-HIV-1 antibody or standard seronegative plasma. Each patient in both groups received a 300-ml infusion every 14 days over a 1-year period, and every 28 days thereafter, in addition to zidovudine and other conventional prophylactic treatments. Plasma donors were selected among symptomless seropositive individuals with a CD4 lymphocyte count > or = 400 x 10(6) cells per liter, a negative p24 antigen assay, and a high concentration of anti-p24 antibody. The plasmas were heat-inactivated before infusion. During the study period (day 28-day 365) scheduled by the protocol, clinical benefit from passive immunotherapy was observed in delaying the appearance of the first AIDS-defining event (P < 0.009) and reducing the cumulative incidence of such events, which was estimated 3-fold higher in the control group compared to the treatment group. Seven deaths occurred in the treatment group vs. 11 in the control group (P = 0.27). A total of 47 patients died or exhibited new AIDS-defining events, 18 in the treatment group and 29 in the control group (P = 0.009). No clinical benefit was observed after the 1-year period with infusions performed every 4 weeks. These results indicate a favorable effect of passive immunotherapy on the evolution of advanced AIDS.