Search PubMed⌕ Search

Biomedical subjects

R A Koup

Publications and source records attributed to R A Koup.

At least 73 records · Page 4Linked to original sources
PubMed1996

Cellular targets of infection and route of viral dissemination after an intravaginal inoculation of simian immunodeficiency virus into rhesus macaques.

We used the simian immunodeficiency virus (SIV)/rhesus macaque model to study events that underlie sexual transmission of human immunodeficiency virus type 1 (HIV-1). Four female rhesus macaques were inoculated intravaginally with SIVmac251, and then killed 2, 5, 7, and 9 d later. A technique that detected polymerase chain reaction-amplified SIV in situ showed that the first cellular targets for SIV were in the lamina propria of the cervicovaginal mucosa, immediately subjacent to the epithelium. Phenotypic and localization studies demonstrated that many of the infected cells were likely to be dendritic cells. Within 2 d of inoculation, infected cells were identified in the paracortex and subcapsular sinus of the draining internal iliac lymph nodes. Subsequently, systemic dissemination of SIV was rapid, since culturable virus was detectable in the blood by day 5. From these results, we present a model for mucosal transmission of SIV and HIV-1.

Animals↗
PubMed1996

Defining antibody protection against HIV-1 transmission in Hu-PBL-SCID mice.

Multiple monoclonal and polyclonal antibody preparations have been shown to neutralize HIV-1 infection in vitro. Upon direct testing in humans, however, many of these have failed to demonstrate clinical efficacy. Hu-PBL-SCID mice offer a model system in which to test the pre-clinical efficacy of antibody preparations. Testing in hu-PBL-SCID mice has shown that some antibodies are able to mediate pre- and post-exposure protection against HIV-1 infection, at concentrations that should be attainable in humans. Despite differences in the route and mode of transmission in humans and in hu-PBL-SCID mice, several aspects of the model make it a favorable model for future testing of antibody protection against HIV-1 infection. These include the architecture of the peritoneal cavity, the mixture of human cells that engraft, the density of human target cells for HIV-1 infection, and the presence of complement and NK cells that can interact with antibody preparations in blocking HIV-1 infection. The use of this model in testing newer antibody preparations for efficacy against primary isolates should enhance our knowledge of the mechanisms of antibody protection against HIV-1 infection in vivo and speed the pre-clinical evaluation of potential immunoprophylactic agents against HIV-1.

Animals↗
PubMed1996

Relative resistance to HIV-1 infection of CD4 lymphocytes from persons who remain uninfected despite multiple high-risk sexual exposure.

Some individuals remain uninfected with human immunodeficiency virus type-1 (HIV-1) despite multiple high-risk sexual exposures. We studied a cohort of 25 subjects with histories of multiple high-risk sexual exposures to HIV-1 and found that their CD8+ lymphocytes had greater anti-HIV-1 activity than did CD8+ lymphocytes from nonexposed controls. Further studies indicated that their purified CD4+ lymphocytes were less susceptible to infection with multiple primary isolates of HIV-1 than were CD4+ lymphocytes from the nonexposed controls. This relative resistance to HIV-1 infection did not extend to T-cell line-adapted strains, was restricted by the envelope glycoprotein, was not explained by the cell surface density of CD4 molecules, but was associated with the activity of the C-C chemokines RANTES, MIP-1alpha, and MIP-1beta. This relative resistance of CD4+ lymphocytes may contribute to protection from HIV-1 in multiply exposed persons.

CD4-Positive T-Lymphocytes↗
PubMed1996

The role of a mutant CCR5 allele in HIV-1 transmission and disease progression.

A 32-nucleotide deletion (delta 32) within the beta-chemokine receptor 5 (CCR5) gene has been described in subjects who remain uninfected despite extensive exposure to HIV-1. This allele was found to be common in the Caucasian population with a frequency of 0.0808, but was not found in people of African or Asian ancestry. To determine its role in HIV-1 transmission and disease progression, we analyzed the CCRS genotype of 1252 homosexual men enrolled in the Chicago component of the Multicenter AIDS Cohort Study (MACS). No infected participant was found to be homozygous for the delta 32 allele, whereas 3.6% of at-risk but uninfected Caucasian participants were homozygous, showing the highly protective role of this genotype against sexual acquisition of HIV-1. No evidence was found to suggest that heterozygotes were protected against HIV-1 infection, but a limited protective role against disease progression was noted. The delta 32 allele of CCR5 is therefore an important host factor in HIV-1 transmission and pathogenesis.

Alleles↗
PubMed1996

The immunopathology of HIV infection.

Fourteen years into the global epidemic of the acquired immunodeficiency syndrome, the exact mechanisms by which the human immunodeficiency virus (HIV) causes the destruction of the immune system remain unresolved. Infection with HIV is characterized by both continual virus replication and a vigorous immune response. The length of time from initial infection to the almost inevitable loss of CD4 positive T helper lymphocytes averages 10 years, indicating the dramatic and prolonged interplay of the virus and the host immune response. In this article we discuss many of the leading hypotheses for both direct and indirect mechanisms that have been proposed to explain the loss of CD4 cells. Current evidence suggests strongly that direct infection of CD4 cells is adequate to explain their loss, but that cofactors and indirect mechanisms may contribute to the overall process. This leads to the conclusion that the immunopathology of HIV infection can be most effectively countered by using antiretroviral chemotherapy.

Animals↗
PubMed1996

Macrophages and CD4+ T lymphocytes from two multiply exposed, uninfected individuals resist infection with primary non-syncytium-inducing isolates of human immunodeficiency virus type 1.

Despite multiple, high-risk sexual exposures, some individuals remain uninfected with human immunodeficiency virus type 1 (HIV-1). CD4+ lymphocytes from these individuals are less susceptible to infection in vitro with some strains of HIV-1, suggesting that the phenotype of the virus may influence its ability to interact with certain CD4+ cells. In the present study, we examined the susceptibility of CD4+ T lymphocytes and macrophages from two exposed uninfected individuals (EU2 and EU3) to infection with a panel of biologically cloned isolates of HIV-1 having either a non-syncytium-inducing (NSI) or a syncytium-inducing (SI) phenotype. Our results indicate that CD4+ T lymphocytes from EU2 and EU3 are resistant to infection with NSI isolates of HIV-1 but are susceptible to infection with primary SI isolates. In addition, we found that macrophages from EU2 and EU3 are resistant to infection with both NSI and SI isolates. The latter finding was confirmed by using several uncloned NSI and SI isolates obtained from patients during acute HIV-1 infection. In further experiments, env clones encoding glycoproteins characteristic of NSI or SI viruses were used in single-cycle infectivity assays to evaluate infection of CD4+ lymphocytes and macrophages from EU2 and EU3. Consistent with our previous results, we found that macrophages from these individuals are resistant to infection with NSI and SI env-pseudotyped viruses, while CD4+ T lymphocytes are resistant to NSI, but not SI, pseudotyped viruses. Overall, our results demonstrate that CD4+ cells from two exposed uninfected individuals resist infection in vitro with primary, macrophage-tropic, NSI isolates of HIV-1, which is the predominant viral phenotype found following HIV-1 transmission. Furthermore, infection with NSI isolates was blocked in both CD4+ T lymphocytes and macrophages from these individuals, suggesting that there may be a common mechanism for resistance in both cell types.

CD4-Positive T-Lymphocytes↗
PubMed1996

Effective ex vivo neutralization of human immunodeficiency virus type 1 in plasma by recombinant immunoglobulin molecules.

We tested the ability of human monoclonal antibodies (immunoglobulin G1b12 [IgG1b12] and 19b) and CD4-based molecules (CD4-IgG2 and soluble CD4 [sCD4]) to neutralize human immunodeficiency virus type 1 directly from the plasma of seropositive donors in an ex vivo neutralization assay. IgG1b12 and CD4-IgG2, at concentrations from 1 to 25 micrograms/ml, were found to be effective at reducing the HIV-1 titer in most plasma samples. When viruses recovered from plasma samples were expanded to produce virus stocks, no correlation between the neutralization sensitivities to IgG1b12 and CD4-IgG2 of the in vitro passaged stocks and those of the ex vivo neutralizations performed directly on the plasma was observed. These differences could be due to changes in neutralization sensitivity that occur after one passage of the virus in vitro, or they could be related to the presence of complement or antibodies in the plasma. Furthermore, differences in expression of adhesion molecules on plasma-derived and phytohemagglutinin-activated peripheral blood mononuclear cell-derived viruses could be involved. These studies suggest that IgG1b12 and CD4-IgG2 have broad and potent neutralizing activity in both in vitro and ex vivo neutralization assays and should be considered for use as potential immunoprophylactic or therapeutic agents.

Antibodies, Monoclonal↗
PubMed1995

An epitope-selective, transporter associated with antigen presentation (TAP)-1/2-independent pathway and a more general TAP-1/2-dependent antigen-processing pathway allow recognition of the HIV-1 envelope glycoprotein by CD8+ CTL.

The lysis of virally infected cells by CTLs requires the recognition of processed fragments of viral proteins presented in association with class I MHC molecules on the surfaces of infected cells. Processing begins in the cytosol with the degradation of viral proteins into peptides that are then transported into the endoplasmic reticulum (ER) for association with newly synthesized class I molecules. Transport is mediated by a heterodimer of the MHC-encoded proteins, transporter associated with Ag presentation (TAP)-1 and TAP-2. Uncertainty exists over the site of processing of viral envelope (env) proteins. The extracellular domains of env proteins are not present in the cytosol, the site in which the class I-restricted Ag-processing pathway begins. Rather, the ecto-domains of env proteins are cotranslationally translocated into the ER during biosynthesis. We have analyzed the processing of the HIV-1 env protein by using a large series of env-specific human CD8+ CTL clones. These studies have led to the delineation of two distinct processing pathways. The first pathway permits a subset of class I-restricted epitopes in the ecto-domain of the env protein to be generated efficiently by a TAP-1/2-independent mechanism localized to the ER or a premedial Golgi compartment. A second, more general pathway that is capable of generating all env epitopes uses as a substrate env protein mislocalized to the cytosol and produces peptides that are transported from the cytoplasm to the ER in a TAP-1/2-dependent fashion.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

The immunology of primary HIV infection: which immune responses control HIV replication?

In the majority of patients, HIV-1 replication is quickly and efficiently controlled after the initial burst of viremia. Recent studies have begun to elucidate the underlying immune responses that may be responsible for this dramatic reduction in viral load. These responses include those of HIV-specific CD8+ cytotoxic T lymphocytes and antibodies capable of binding the virus.

Amino Acid Sequence↗
PubMed1995

Expression and characterization of CD4-IgG2, a novel heterotetramer that neutralizes primary HIV type 1 isolates.

CD4-IgG2 is a novel fusion protein comprising human IgG2 in which the Fv portions of both heavy and light chains have been replaced by the V1 and V2 domains of human CD4. This tetrameric protein is being developed as an immunoprophylactic agent to reduce the probability of infection following HIV-1 exposure, in settings such as occupational or perinatal exposure to the virus. CD4-IgG2 has been expressed in Chinese hamster ovary cells and is secreted as a fully assembled heterotetramer. The protein binds with nanomolar affinity to purified gp120 from both a laboratory-adapted strain and a primary isolate of HIV-1. Pharmacokinetic studies in rabbits demonstrated that CD4-IgG2 has a plasma terminal half-life greater than 1 day, compared with 15 min for soluble CD4 (sCD4). CD4-IgG2 does not bind to Fc receptors on the surface of U937 monocyte/macrophage cells. Compared to molecules that incorporate the Fc portion of IgG1, CD4-IgG2 has less potential to mediate functions such as antibody-dependent enhancement of infection or transplacental transmission of HIV-1. When tested in a virus-free HIV-1 envelope glycoprotein-mediated cell fusion assay, the tetrameric CD4-IgG2 molecule inhibited syncytium formation more effectively than monomeric sCD4 or a dimeric CD4-gamma 2 fusion protein. This suggests the protein will block cell-to-cell transmission of HIV-1. Moreover, CD4-IgG2 effectively neutralized a panel of laboratory-adapted strains and primary isolates of HIV-1, including strains with different tropisms and isolated from different stages of the disease, at concentrations that should be readily achieved in vivo.

Animals↗
PubMed1995

Pre- and postexposure protection against human immunodeficiency virus type 1 infection mediated by a monoclonal antibody.

Monoclonal antibody BAT123 was passively transferred into SCID mice reconstituted with human peripheral blood lymphocytes (hu-PBL-SCID) to study passive antibody protection against human immunodeficiency virus type 1 (HIV-1) infection. BAT123 is specific for the third variable loop of the gp120 of HIV-1LAI. Animals were protected against subsequent infection with LAI strain, but not other virus strains, when BAT123 (1 mg/kg; 25 micrograms/mouse) was given 1 h before virus inoculation. This resulted in a peak serum concentration of 16 micrograms/mL of the antibody, which should be easily attainable in humans. In addition, postexposure protection was observed when the antibody was given within 4 h of virus inoculation. No therapeutic effect was observed, however, when BAT123 was administered after infection had been established. These results indicate that passive antibody prophylaxis against HIV-1 infection may be possible in certain clinical situations.

Animals↗
PubMed1994

A region of the third variable loop of HIV-1 gp120 is recognized by HLA-B7-restricted CTLs from two acute seroconversion patients.

HIV-1 envelope-specific CTL clones were isolated from the peripheral blood of two patients from within weeks of seroconversion. These clones were CD8+ and restricted by the HLA-B7 molecule. The minimum epitope recognized by the clones was determined to be the 30-amino acid (aa) sequence RPNNNTRKSI within the third variable (V3) loop of the envelope glycoprotein gp120. The aa sequence of this epitope is consistent with the motif found in naturally processed peptides eluted from HLA-B7 molecules. This region of the V3 loop is reasonably well conserved among clade B and some nonclade B isolates of HIV-1, especially at the anchor residues that determine binding to the HLA-B7 molecule. Using peptides based upon virus sequences present within each patient, we determined that autologous viruses were recognized by the clones, and we detected no escape variants from the initial clonal response during the acute phase of infection. Interestingly, a serine to arginine change at position 9 of the epitope abrogated clone recognition in one of the patients. This aa change is one factor that has been associated with a change from a nonsyncytium-inducing to a syncytium-inducing phenotype of HIV-1, raising the possibility that in HLA-B7-expressing patients, escape from this clonal CTL response and a change in viral phenotype may be linked. This study demonstrates that human CTL can be generated against sequences within the third variable loop of HIV-1 gp120. Because multiple vaccine strategies are based upon the V3 loop of HIV-1 gp120, this defined epitope can be exploited in determining the ability of certain vaccines to stimulate a CTL response in a select population of individuals.

Acute Disease↗
PubMed1994

Shutting down HIV.

Explore the source record for details and available documents.

Acute Disease↗
PubMed1994

Characterization of human immunodeficiency virus type 1-specific cytotoxic T lymphocyte clones isolated during acute seroconversion: recognition of autologous virus sequences within a conserved immunodominant epitope.

Virus-specific cytotoxic T lymphocytes (CTL) are involved in protective immunity to many virus infections. It has recently been shown that CTL are detectable early during primary infection with the primate lentiviruses, human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus. To better characterize the CTL response during acute HIV-1 infection, HIV-1-specific CTL clones were generated from two patients during symptomatic HIV-1 seroconversion. These CTL clones demonstrated specificity for env of HIV-1 and recognized sequences within gp41. Two human histocompatibility leukocyte antigen (HLA) A31-restricted clones from the same individual were found to have differing virus strain specificities. Both clones recognized the 11-amino acid peptide RLRDLLLIVTR from position 770-780 of gp41. A change from T to V at position 779 in this epitope abrogated lysis by one clone but not the other. A CTL clone from the other patient, restricted by a different class I HLA allele, recognized the nine-amino acid peptide HRLRDLLLI from position 769-777 of gp41. Of note, the peptide RLRDLLLIVTR has been shown by others to be presented to CTL by HLA-A3.1. Autologous virus sequences from seroconversion and up to 15 wk after presentation in these two patients were recognized by the CTL clones isolated during acute infection. None of the CTL clones recognized the MN strain of HIV-1, indicating the problems inherent in relying on a single virus strain in the development of a vaccine. These studies have identified an immunodominant and promiscuous area for the generation of CTL responses within gp41. This recognition of autologous virus sequences by the initial CTL response is consistent with the hypothesis that a single virus strain is transmitted to the seroconverter and that the CTL response is involved in the initial control of that virus. These studies indicate the importance of the CTL response to HIV-1 infection and have implications in the design of vaccines.

Adult↗
PubMed1994

Quantitative assessment of human immunodeficiency virus type 1 replication in human xenografts of acutely infected Hu-PBL-SCID mice.

Replication of the IIIB strain of human immunodeficiency virus type 1 (HIV-1IIIB) in CB.17 scid/scid mice reconstituted with human peripheral blood lymphocytes (Hu-PBL-SCID) was investigated. Hu-PBL-SCID mice could be infected, in a dose-dependent manner, when HIV-1IIIB was injected intraperitoneally. Replication-competent HIV-1 could be recovered from spleen, peripheral blood, bone marrow, thymus, lymph node, and peritoneal cavity, indicating the ability of the infection to spread to human tissue throughout the chimeric animals. HIV-1 infection was quantitated using p24 determination, end-point dilution culture, and polymerase chain reaction amplification. The level of HIV-1 replication in Hu-PBL-SCID mice was found to approximate the level reported in human infection. No HIV-1-specific immune response was generated to this infection, but nonspecific immune activation did occur, as also reported in human infection. Similarities therefore exist between HIV-1 infection of humans and Hu-PBL-SCID mice, which makes the latter an in vivo model in which to study HIV-1 replication.

Animals↗
PubMed1994

Temporal association of cellular immune responses with the initial control of viremia in primary human immunodeficiency virus type 1 syndrome.

Virologic and immunologic studies were performed on five patients presenting with primary human immunodeficiency virus type 1 (HIV-1) infection. CD8+ cytotoxic T lymphocyte (CTL) precursors specific for cells expressing antigens of HIV-1 Gag, Pol, and Env were detected at or within 3 weeks of presentation in four of the five patients and were detected in all five patients by 3 to 6 months after presentation. The one patient with an absent initial CTL response had prolonged symptoms, persistent viremia, and low CD4+ T-cell count. Neutralizing antibody activity was absent at the time of presentation in all five patients. These findings suggest that cellular immunity is involved in the initial control of virus replication in primary HIV-1 infection and indicate a role for CTL in protective immunity to HIV-1 in vivo.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Development of the anti-gp120 antibody response during seroconversion to human immunodeficiency virus type 1.

We have studied the development of the antibody response to the surface glycoprotein gp120 of human immunodeficiency virus type 1 in three individuals who presented with primary human immunodeficiency virus type 1 infection syndrome. Serum anti-gp120 antibodies were first detected 4 to 23 days after presentation, after p24 antigen and infectious-virus titers in the peripheral blood had declined manyfold from their highest values. Whether anti-gp120 antibodies present at undetectable levels are involved in clearance of viremia remains unresolved. Among the earliest detectable anti-gp120 antibodies were those to conformationally sensitive epitopes; these antibodies were able to block the binding of gp120 monomers to soluble CD4 or to a human monoclonal antibody to a discontinuous epitope overlapping the CD4-binding site. Some of these antibodies were type specific to a degree, in that they were more effective at blocking ligand binding to autologous gp120 than to heterologous gp120. However, the appearance of these antibodies did not correlate with that of antibodies able to neutralize the autologous virus in vitro by a peripheral blood mononuclear cell-based assay. Antibodies to the V3 loop were detected at about the same time as, or slightly later than, those to the CD4-binding site. There was a weak correlation between the presence of antibodies to the V3 loop and autologous virus-neutralizing activity in two of three individuals studied. However, serum from the third individual contained V3 antibodies but lacked the ability to neutralize the autologous virus in vitro, even immediately after seroconversion. Thus, no simple, universal correlate of autologous virus-neutralizing activity in a peripheral blood mononuclear cell-based assay is apparent from in vitro assays that rely on detecting antibody interactions with monomeric gp120 or fragments thereof.

Amino Acid Sequence↗