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S Zolla-Pazner

Publications and source records attributed to S Zolla-Pazner.

At least 55 records · Page 3Linked to original sources
PubMed1998

Human immunodeficiency virus (HIV) envelope binds to CXCR4 independently of CD4, and binding can be enhanced by interaction with soluble CD4 or by HIV envelope deglycosylation.

Chemokine receptor CXCR4 (also known as LESTR and fusin) has been shown to function as a coreceptor for T-cell-tropic strains of human immunodeficiency virus type 1 (HIV-1). We have developed a binding assay to show that HIV envelope (Env) can interact with CXCR4 independently of CD4 but that this binding is markedly enhanced by the previous interaction of Env with soluble CD4. We also show that nonglycosylated HIV-1(SF-2) gp120 or sodium metaperiodate-treated oligomeric gp160 from HIV-1(451) bound much more readily to CXCR4 than their counterparts with intact carbohydrate residues did.

Animals↗
PubMed1998

Synergistic neutralization of simian-human immunodeficiency virus SHIV-vpu+ by triple and quadruple combinations of human monoclonal antibodies and high-titer anti-human immunodeficiency virus type 1 immunoglobulins.

We have tested triple and quadruple combinations of human monoclonal antibodies (MAbs), which are directed against various epitopes on human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins, and a high-titer anti-HIV-1 human immunoglobulin (HIVIG) preparation for their abilities to neutralize a chimeric simian-human immunodeficiency virus (SHIV-vpu+). This virus encodes the HIV-1 strain IIIB env, tat, rev, and vpu genes. The quantitative nature of the Chou-Talalay method (Adv. Enzyme Regul. 22:27-55, 1984) allows ranking of various combinations under identical experimental conditions. Of all triple combinations tested, the most potent neutralization was seen with MAbs 694/98D plus 2F5 plus 2G12 (directed against domains on V3, gp41, and gp120, respectively) as measured by the total MAb concentration required to reach 90% neutralization (90% effective concentration [EC90], 2.0 microg/ml). All triple combinations involving MAbs and/or HIVIG that were tested yielded synergy with combination index values of < 1; the dose reduction indices (DRIs) ranged from 3.1 to 26.2 at 90% neutralization. When four MAbs (the previous three plus MAb F105, directed against the CD4 binding site) were combined, higher neutralization potency (EC90 1.8 microg/ml) and a higher degree of synergy compared to any triple combination were seen. The mean DRIs of the quadruple combination were approximately twice that of the most synergistic triple combination. We conclude that human MAbs targeting different HIV-1 envelope glycoprotein epitopes exhibit strong synergy when used in combination, a fact that could be exploited clinically for passive immunoprophylaxis against HIV-1.

Animals↗
PubMed1998

Neutralization profiles of primary human immunodeficiency virus type 1 isolates in the context of coreceptor usage.

Most strains of human immunodeficiency virus type 1 (HIV-1) which have only been carried in vitro in peripheral blood mononuclear cells (primary isolates) can be neutralized by antibodies, but their sensitivity to neutralization varies considerably. To study the parameters that contribute to the differential neutralization sensitivity of primary HIV-1 isolates, we developed a neutralization assay with a panel of genetically engineered cell lines (GHOST cells) that express CD4, one of eight chemokine receptors which function as HIV-1 coreceptors, and a Tat-dependent green fluorescent protein reporter cassette which permits the evaluation and quantitation of HIV-1 infection by flow cytometry. All 21 primary isolates from several clades could grow in the various GHOST cell lines, and their use of one or more coreceptors could easily be defined by flow cytometric analysis. Ten of these primary isolates, three that were CXCR4 (X4)-tropic, three that were CCR5 (R5)-tropic, and four that were dual- or polytropic were chosen for study of their sensitivity to neutralization by human monoclonal and polyclonal antibodies. Viruses from the X4-tropic category of viruses were first tested since they have generally been considered to be particularly neutralization sensitive. It was found that the X4-tropic virus group contained both neutralization-sensitive and neutralization-resistant viruses. Similar results were obtained with R5-tropic viruses and with dual- or polytropic viruses. Within each category of viruses, neutralization sensitivity and resistance could be observed. Therefore, sensitivity to neutralization appears to be the consequence of factors that influence the antibody-virus interaction and its sequelae rather than coreceptor usage. Neutralization of various viruses by the V3-specific monoclonal antibody, 447-52D, was shown to be dependent not only on the presence of the relevant epitope but also on its presentation. An epitope within the envelope of a particular virus is not sufficient to render a virus sensitive to neutralization by an antibody that recognizes that epitope. Moreover, conformation-dependent factors may overcome the need for absolute fidelity in the match between an antibody and its core epitope, permitting sufficient affinity between the viral envelope protein and the antibody to neutralize the virus. The studies indicate that the neutralization sensitivity of HIV-1 primary isolates is a consequence of the complex interaction between virus, antibody, and target cell.

Cell Line↗
PubMed1998

Role of cellular adhesion molecules in HIV type 1 infection and their impact on virus neutralization.

While CD4 and several chemokine receptors are the principal receptors for human immunodeficiency virus type 1 (HIV-1) viruses, other cell membrane proteins also play a role in HIV-1 infection. A large array of host cell-derived membrane proteins, including adhesion molecules, are incorporated into the envelope of HIV-1 virions, and the profile of host cell proteins acquired by the virus depends on the cells used to propagate the virus. The major leukocyte adhesion molecules, such as leukocyte-function associated antigen-1 (LFA-1), intercellular adhesion molecule-1 (ICAM-1), and CD44, retain their biological functions when expressed on the virion surface, and have been shown to increase virus-cell interaction, enhance virus infectivity, and extend the host cell range of the virus. LFA-1 and its ICAM ligands are also necessary for syncytium formation and cell-to-cell transmission of HIV-1. Furthermore, several studies demonstrate that the presence and level of cell-derived adhesion molecules on the surface of HIV-1 virions affect the process by which antibody-mediated virus neutralization occurs and is measured: the level of virus neutralization is influenced by the host cell-derived adhesion molecules present on the virus, and thus, by the type of host cells in which the virus was produced. Adhesion molecules expressed on the target cells used in neutralization assays similarly affect HIV-1 neutralization by virus-specific antibodies. Consistent with these observations is the finding that neutralizing activities of both HIV+ plasma and human anti-gp120 monoclonal antibodies (Mabs) are enhanced by an anti-LFA-1 Mab capable of blocking LFA-1 functions. Hence, LFA-1, ICAM-1, and other cellular adhesion molecules are involved in different stages of HIV-1 infection and profoundly affect HIV-1 neutralization by virus-specific antibodies. These findings illuminate the biology of virus-cell interactions and have significant implications for evaluating candidate HIV vaccines.

Apoptosis↗
PubMed1998

[Increase of circulating CD3+CD4-CD8-CD19+ cells in the latent phase of HIV-1 infection].

Having reported that HIV-1-infected T cell lines are rescued as CD4- from cytolysis by human complement factor B, we now show the presence of an in vivo counterpart of such CD4- T cells by demonstrating the circulating CD3+ CD4- CD8- CD29+ cells in the blood of seropositive subjects (n = 91, classified by the immunologic scale scores 0, 1, 2 and 3). The cell population was found to be significantly increased in the early phase of infection in score 0: 195/mm3 (p < 0.005) and in score 1:376/mm3 (p = 0.001). With the infection progressing to score 2, the cells decreased to 220/mm3 (p < 0.001) and finally to the same range: 101/mm3, as that of uninfected subjects. Further elucidation of the mechanism of the appearance and disappearance of that population in vivo could help to elucidate protective immunologic processes.

Antigens, CD↗
PubMed1997

Anti-human immunodeficiency virus type 1 human monoclonal antibodies that bind discontinuous epitopes in the viral glycoproteins can identify mimotopes from recombinant phage peptide display libraries.

A phage display library screening approach was used to identify peptide sequences that could bind to anti-HIV-1 MAbs whose binding specificities are complex. Most of the antibodies used recognize discontinuous epitopes in gp120 and one recognizes gp41. Both a 15-mer and a 21-mer display library (each with a complexity of greater than 60 x 10[6]) and two constrained, V3 region-biased libraries, all expressed as recombinant pIII protein of filamentous phage, were used. The unmapped anti-gp120 human MAb A32 recognized a set of related linear sequences and repeatedly identified a single phage sequence that could form a cyclic disulfide structure. Selection methods were also developed so that phage could be obtained by competition selection in the presence of antibody bound to native, monomeric gp120 antigen (used with MAb IgG1b12 and the anti-gp120 V3 region MAb 447-52D) or gp120 variable region 3 synthetic peptides (used with anti-gp120 V3 region MAb 19b). The potent, virus-neutralizing MAb IgG1b12 recognized numerous sequences and, when used in competition with gp120, recognized only one sequence. These studies extend the range of antibody determinant studies that can be performed with display phage libraries, demonstrate a workable experimental strategy for use of competition ligands to discriminate among phage mimotopes, and provide a large number of mimotopes that bind potent virus-neutralizing MAbs for HIV-1 vaccine studies.

Amino Acid Sequence↗
PubMed1997

Human monoclonal antibodies to the V3 loop of HIV-1 with intra- and interclade cross-reactivity.

Five human anti-V3 mAbs were generated from Ab-producing cells derived from the blood of HIV-1-infected individuals from North America and selected using the V3 peptide of a divergent clade B isolate, HIV(RF). The anti-V3(RF) mAbs were mapped to a cluster of three overlapping epitopes present in the KSITKGP sequence located in the hypervariable region on the N-terminal side of the V3 loop. Broad immunochemical cross-reactivity was noted when the mAbs were tested for binding to V3 peptides derived from four clade A viruses, nine clade B viruses, and two clade C viruses. These results demonstrate antigenic relatedness in the V3 regions of these three HIV-1 clades. Affinities determined by surface plasmon resonance were higher for recombinant gp120 than for V3 peptides, suggesting that these mAbs recognize both linear and conformationally dependent epitopes of the V3 loop. Two of the mAbs neutralized four clade B T cell line-adapted and primary isolates with varying degrees of potency. The two neutralizing mAbs were the most cross-reactive with V3 peptides from several clades, had the highest affinity for V3(RF) and V3(MN), and stained HIV-infected cells. The data suggest that cross-reactivity, affinity, cell surface staining, and neutralizing activity are characteristics that describe an optimal fit between Ag and Ab. The results also demonstrate that the V3 peptides representing the sequence of several clade A, B, and C viruses share antigenic features that are recognized by the human immune response, a finding that suggests that cross-clade immunity to HIV-1 may be inducible by HIV-1 vaccines.

Antibodies, Monoclonal↗
PubMed1997

Synergistic neutralization of a chimeric SIV/HIV type 1 virus with combinations of human anti-HIV type 1 envelope monoclonal antibodies or hyperimmune globulins.

A panel of 14 human IgG monoclonal antibodies (MAbs) specific for envelope antigens of the human immunodeficiency virus type 1 (HIV-1), 2 high-titer human anti-HIV-1 immunoglobulin (HIVIG) preparations, and 15 combinations of MAbs or MAb/HIVIG were tested for their ability to neutralize infection of cultured human T cells (MT-2) with a chimeric simian immunodeficiency virus (SHIV-vpu+), which expressed HIV-1 IIIB envelope antigens. Eleven MAbs and both HIVIGs were neutralizing. When used alone, the anti-CD4-binding site MAb b12, the anti-gp41 MAb 2F5, and the anti-gp120 MAb 2G12 were the most potent. When combination regimens involving two MAbs targeting different epitopes were tested, synergy was seen in all paired MAbs, except for one combination that revealed additive effects. The lowest effective antibody concentration for 50% viral neutralization (EC50) and EC90 were achieved with combinations of MAbs b12, 2F5, 2G12, and the anti-V3 MAb 694/98D. Depending on the combination regimen, the concentration of MAbs required to reach 90% virus neutralization was reduced approximately 2- to 25-fold as compared to the dose requirement of individual MAbs to produce the same effect. Synergy of the combination regimens implies that combinations of antibodies may have a role in passive immunoprophylaxis against HIV-1. The ability of SHIV to replicate in rhesus macaques will allow us to test such approaches in vivo.

Animals↗
PubMed1997

Binding of antibodies to virion-associated gp120 molecules of primary-like human immunodeficiency virus type 1 (HIV-1) isolates: effect on HIV-1 infection of macrophages and peripheral blood mononuclear cells.

Using immunobiochemical approaches we previously studied the conformation and surface exposure of different immunodominant regions within the oligomeric, virion-associated form of the gp120 envelope glycoprotein of the human immunodeficiency virus type 1 (HIV-1) (L Stamatatos and C. Cheng-Mayer (1995) J. Virol. 69, 6191-6198). These studies allowed us to determine to what extent epitopes within these immunodominant regions of the oligomeric gp120 are occluded or accessible to antibody binding on the virion surface of two primary-like (HIV-1SF162 and HIV-1SF128A) and one. T-cell-line-adapted (HIV-1SF2) isolates. Here, we investigate whether binding of anti-gp120 monoclonal antibodies (MAbs) to exposed epitopes of the immunodominant regions of oligomeric gp120 results in neutralization of HIV-1 infection and whether certain exposed sites are better targets for neutralization than others. We also test whether proposed mechanisms for antibody-mediated neutralization of T-cell-line-adapted HIV-1 isolates, e.g., antibody-mediated gp120-virion dissociation, are applicable to primary-like HIV-1 isolates. We assess the neutralization potential of anti-V2 loop, anti-V3 loop, and anti-CD4 binding site MAbs using human primary macrophages or peripheral blood mononuclear cells (PBMC) as target cells and HIV-1SF162 and HIV-1SF128A as infecting isolates. Our data indicate that: (i) not every exposed epitope of the immunodominant regions of gp120 oligomers on the virion surface is a target for neutralization; (ii) during virus-cell fusion specific exposure of previously occluded V3 loop epitopes within gp120 oligomers occurs, which may become targets for neutralization; (iii) antibody-mediated gp120-virion dissociation does not appear to be a major mechanism of neutralization for the primary-like HIV-1 isolates tested here; and (iv) infection of macrophages is more sensitive to neutralization by anti-gp120 monoclonal antibodies than PBMC. We also report that binding of one of the two anti-CD4 binding site MAbs tested mediated enhancement of macrophage cell infection in a concentration-dependent fashion, while binding of the other anti-CD4 binding site MAb resulted in efficient neutralization of infection of both macrophages and PBMC.

Animals↗
PubMed1997

Resting cell neutralization assay for HIV-1 primary isolates.

A technique is described for detecting the activity of neutralizing polyclonal or monoclonal antibodies against HIV-1 primary isolates. Most commonly, neutralizing antibody activity for HIV-1 is assessed by quantifying the ability of antibodies to inhibit virus infection in mitogen-activated peripheral blood mononuclear cells or transformed lymphocytes. Because the target of HIV infection in vivo is neither a mitogen-activated nor a transformed cell, an assay using unstimulated peripheral blood mononuclear cells as a more physiologic target cell was developed. This "resting cell assay" mainly utilizes primary HIV-1 isolates that have been carried for only a few passages in vitro. The result is an assay that is more efficient to perform and that detects neutralizing activity with comparable or greater sensitivity than that previously described for assays of primary HIV-1 isolates.

Antibodies, Monoclonal↗
PubMed1997

Long-term protection of chimpanzees against high-dose HIV-1 challenge induced by immunization.

A combination AIDS vaccine approach consisting of priming with adenovirus-HIV-1MN gp160 recombinants followed by boosting with HIV-1SF2 gp120 was evaluated in chimpanzees. Long-lasting protection, requiring only three immunizations, was achieved against a low-dose challenge with the SF2 strain of HIV-1 and a subsequent high-dose SF2 challenge administered 1 year later without an intervening boost. Notably, neutralizing antibody responses against both clinical and laboratory isolates developed in three chimpanzees and persisted until the time of high-dose challenge. The possibility that cytotoxic T-lymphocytes contribute to low-dose protection of a chimpanzee lacking neutralizing antibodies is suggested. Our results validate the live vector priming/subunit booster approach and should stimulate interest in assessing this combination vaccine approach in humans.

Adenoviridae↗
PubMed1997

Neutralization of a clade B primary isolate by sera from human immunodeficiency virus-uninfected recipients of candidate AIDS vaccines.

The inability of antibodies induced by experimental human immunodeficiency virus type 1 (HIV-1) vaccines to neutralize HIV-1 primary isolates may be due to a failure to elicit such antibodies, antigenic differences between the vaccine and the strains tested, insensitivity of the assays used, or to a combination of factors. New neutralization assays were used to determine the ability of candidate AIDS vaccines to generate neutralizing antibodies for clade B primary isolate BZ167, which is closely related in portions of its envelope to the immunizing strains. Sera from HIV-uninfected volunteers in vaccine trials were tested, and neutralizing activity was found in recipients of recombinant (r) gp120MN or of rgp160MN-containing canarypox boosted with rgp120SF-2. Detection of antibodies that neutralize primary isolate BZ167 correlated with neutralizing activity for homologous vaccine strains. These data demonstrate that certain candidate AIDS vaccines can elicit antibodies that neutralize a primary isolate of HIV-1.

AIDS Vaccines↗
PubMed1997

Surrogate marker of preclinical tuberculosis in human immunodeficiency virus infection: antibodies to an 88-kDa secreted antigen of Mycobacterium tuberculosis.

Antibodies to purified, size-fractionated secreted proteins of Mycobacterium tuberculosis in sera from patients with human immunodeficiency virus (HIV) infection and active tuberculosis (HIV/TB patients), and in stored sera obtained from the same patients prior to clinical manifestation of TB, were evaluated by ELISA, and the repertoire of antigens recognized was analyzed by immunoblotting. Compared with non-HIV/TB patients, HIV/TB patients had lower levels of anti-mycobacterial antibodies, and these were directed toward a restricted set of antigens. Antibodies to an 88-kDa secreted antigen were present in the sera of 74% of HIV/TB patients during the years (1.5-6) prior to manifestation of active, clinical tuberculosis, although only 66% were positive by the time tuberculosis was diagnosed. The presence of antibodies to the 88-kDa antigen can serve as a surrogate marker for identifying HIV-infected persons with active, subclinical disease who are at a high risk of developing clinical tuberculosis.

Antibodies, Bacterial↗
PubMed1997

Neutralization of HIV-1 primary isolates by polyclonal and monoclonal human antibodies.

To examine antibody-mediated neutralization of HIV-1 primary isolates in vitro, we tested sera and plasma from infected individuals against four clade B primary isolates. These isolates were analyzed further for neutralization by a panel of several human anti-HIV-1 mAb in order to identify the neutralizing epitopes of these viruses. Each of the HIV-1+ serum and plasma specimens tested had neutralizing activities against one or more of the four primary isolates. Of the three individual sera, one (FDA-2) neutralized all of the four isolates, while the other two sera were effective against only one virus. The pooled plasma and serum samples reacted broadly with these isolates. Based on the neutralizing activities of the mAb panel, each virus isolate exhibited a distinct pattern of reactivity, suggesting antigenic diversity among clade B viruses. Neutralizing epitopes were found in the V3 loop and CD4-binding domain of gp120, as well as near the transmembrane region (cluster II epitope) of gp41. A mAb directed to the cluster I epitope of gp41 near the immunodominant disulfide loop weakly neutralized one primary isolate. None of the mAb in the panel affected one primary isolate, US4, although this virus was sensitive to neutralization by some of the polyclonal antibody specimens. This isolate was also resistant to neutralization by a cocktail of 10 mAb, most of which individually inhibited at least one of the other three viruses tested. These results suggest that neutralizing activity for this latter virus is present in certain HIV-1+ sera/plasma, but is not exhibited by the mAb in the panel. Thus, effective neutralizing antibodies against primary isolates can be generated by humans upon exposure to HIV-1, but not all of these antigenic specificities are represented in a large panel of human anti-HIV-1 mAb.

Antibodies, Monoclonal↗
PubMed1997

Human humoral responses to antigens of Mycobacterium tuberculosis: immunodominance of high-molecular-mass antigens.

The selection of antigens of Mycobacterium tuberculosis for most studies of humoral responses in tuberculosis patients has been restricted to molecules that were either immunodominant in immunized animals or amenable to biochemical purification rather than those that were reactive with the human immune system. Delineation of antigens that elicit humoral responses during the natural course of disease progression in humans has been hindered by the presence of cross-reactive antibodies to conserved regions on ubiquitous prokaryotic antigens in sera from healthy individuals and tuberculosis patients. The levels of cross-reactive antibodies in the sera were reduced by preadsorption with Escherichia coli lysates, prior to studying their reactivity against a large panel of M. tuberculosis antigens to which the human immune system may be exposed during natural infection and disease. Thus, reactivity against pools of secreted, cellular, and cell wall-associated antigens of M. tuberculosis was assessed by an enzyme-linked immunosorbent assay (ELISA). Initial results suggested that the secreted protein preparation contained antigens most frequently recognized by the humoral responses of pulmonary tuberculosis patients. The culture filtrate proteins were subsequently size fractionated by preparative polyacrylamide gel electrophoresis, characterized by reaction with murine monoclonal antibodies to known antigens of M. tuberculosis by an ELISA, and assessed for reactivity with tuberculous and nontuberculous sera. Results show that a secreted antigen of 88 kDa elicits a strong antibody response in a high percentage of patients with pulmonary tuberculosis. This and other antigens identified on the basis of their reactivity with patient sera may prove useful for developing serodiagnosis for tuberculosis.

Antibodies, Bacterial↗
PubMed1997

Host cell-dependent alterations in envelope components of human immunodeficiency virus type 1 virions.

In addition to gp41 and gp120, an array of cell adhesion molecules is present on the envelope of human immunodeficiency virus type 1 (HIV-1). To examine the role of the host cell in the acquisition of these molecules by virions, both laboratory-adapted and primary isolates were sequentially passaged into different host cells. Viruses obtained from the various host cells were examined for the presence of 10 different cell-derived molecules by a virus binding enzyme-linked immunosorbent assay. Virus progeny raised in peripheral blood mononuclear cells expressed most of the adhesion molecules tested, with the level of LFA-1 being the highest. When viruses were passaged into CEM-SS or SupT1 cells, the expression of most of the adhesion molecules on the virus envelope was lost. In contrast, when viruses were passaged into MT2 cells, the virus progeny bore high levels of LFA-3, ICAM-1, and major histocompatibility complex classes I and II. These studies demonstrate for the first time the host cell dependence of the adhesion molecule profile present on the envelope of primary isolates of HIV-1. The presence of several adhesion molecules that have not previously been identified as components of the envelope of either laboratory or primary isolates is also described. In addition, we show that the adhesion molecule profile of the virions is acquired, or lost, within one passage and is maintained with subsequent passages in the same cell type.

Cell Adhesion Molecules↗