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D D Ho

Publications and source records attributed to D D Ho.

At least 145 records · Page 8Linked to original sources
PubMed1993

Endophthalmitis caused by the coagulase-negative staphylococci. 1. Disease spectrum and outcome.

PURPOSE: The coagulase-negative staphylococci are the most common causes of postoperative endophthalmitis. This study investigates the variability in the disease spectrum and visual outcome of coagulase-negative staphylococcal endophthalmitis in a large, single-center series. METHODS: Ninety consecutive cases of coagulase-negative staphylococcal endophthalmitis were investigated retrospectively from two time periods, 1978 to 1982 and 1985 to 1987, separated by a transitional period in cataract surgery technique. Using a detailed protocol, inpatient, outpatient, and microbiologic records were analyzed. Six-month visual acuity results were obtained. RESULTS: Diagnosis frequently was delayed, often suspected only after hypopyon development. Thirty-seven percent of patients presented more than 1 week after the inoculating event, and 13% presented after more than 1 month. Variable asymptomatic intervals and gradually worsening inflammatory prodromes are noted. Painless endophthalmitis occurred in 16%. Non-epidermidis infections comprised 28%. With vitrectomy/intraocular antibiotic management, 38% and 68% achieved visual acuities of 20/50 and 20/400, respectively. Overall, 10% of patients developed late retinal detachments. This occurred in only 4% of patients, with endophthalmitis occurring after cataract surgery. CONCLUSION: Ophthalmologists should become familiar with the emerging concepts of delayed-onset, chronic, and often painless endophthalmitis in which the coagulase-negative staphylococci play a prominent role.

Adult↗
PubMed1993

Antigenic variation in gp120s from molecular clones of HIV-1 LAI.

To address the relationship between primary sequence variation in HIV-1 gp120 and its antigenic structure in a simple system, we have measured the binding of human and murine monoclonal antibodies (MAbs) to gp120 from four molecular clones of HIV-1 LAI: HxB2, HxB3, Hx10, and NL4-3. Despite the close relationship between these clones, and their relatively conserved gp120 sequences, there is considerable variation in their antigenic structure, judged by MAb reactivities to the V2, V3, and C4 domains and to discontinuous epitopes. Because of our prior studies of the determinants of MAb binding to HxB2 gp120, we can make reasonable estimates of how sequence variation among the LAI clone gp120s affects their binding of some MAbs; for other MAbs our current knowledge of gp120 structure is too limited to allow such estimates. These results indicate that small variations in primary gp120 amino acid sequence can profoundly affect recognition of this glycoprotein by all five groups of defined anti-gp120 neutralizing antibodies.

Amino Acid Sequence↗
PubMed1993

Adaptation of two primary human immunodeficiency virus type 1 isolates to growth in transformed T cell lines correlates with alterations in the responses of their envelope glycoproteins to soluble CD4.

Two sCD4-resistant, primary viruses (P-08 and P-17) were compared with two sCD4-sensitive, T cell line-adapted variants (C-08 and C-17) for their biochemical responses to sCD4. At 37 degrees C, neither primary virus shed gp120 within 8 hr at sCD4 concentrations of up to 500 nM, whereas C-08 and C-17 lost gp120 within minutes of addition of 5-10 nM sCD4. At 4 degrees C, however, P-17 and C-17 shed gp120 at similar rates in response to the same sCD4 concentration. Irrespective of the temperature, gp120 dissociation from both P-17 and C-17 was inhibited by CD4 MAbs 6H10 and 5A8, the latter of which blocks events subsequent to sCD4 binding. Binding of sCD4 to P-17 was greater at 4 degrees C than at 37 degrees C, whereas the converse was found for C-17. Consistent with this, P-17 was neutralized much more potently by sCD4 at 4 degrees C than at 37 degrees C, whereas C-17 was slightly more sensitive to sCD4 at 37 degrees C than at 4 degrees C. Resistance to neutralization by sCD4 is probably determined by kinetic parameters. We suggest that the acquisition of sCD4 neutralization sensitivity and the above biochemical responses to sCD4 are coincidental to the process by which some primary viruses adapt to growth in transformed T cells. Sequence data indicate that there are a limited number of amino acid differences between the Env glycoproteins of the primary viruses and their T cell line-adapted counterparts; the significance of the individual changes is under investigation, but both pairs of viruses have amino acid substitutions in a region of gp41 thought to contact gp120.

Adaptation, Biological↗
PubMed1993

Biological cloning of functionally diverse quasispecies of HIV-1.

Twenty putative clones of HIV-1, derived by biological cloning from two different individuals, were characterized in vitro for functional activity and genotypic diversity. Many of the biological clones isolated by this method were genetically distinct, and could be further distinguished by differences in replication kinetics, host cell range, and/or cytopathicity. Our findings indicate that biological cloning by limiting dilution cultures is an effective method for isolating replication-competent, functionally diverse quasispecies of HIV-1.

Amino Acid Sequence↗
PubMed1993

Antibodies to discontinuous or conformationally sensitive epitopes on the gp120 glycoprotein of human immunodeficiency virus type 1 are highly prevalent in sera of infected humans.

We have used an indirect-capture enzyme-linked immunosorbent assay to quantitate the reactivity of sera from human immunodeficiency virus type 1 (HIV-1)-infected humans with native recombinant gp120 (HIV-1 IIIB or SF-2) or with the gp120 molecule (IIIB or SF-2) denatured by being boiled in the presence of dithiothreitol with or without sodium dodecyl sulfate. Denaturation of IIIB gp120 reduced the titers of sera from randomly selected donors by at least 100-fold, suggesting that the majority of cross-reactive anti-gp120 antibodies present are directed against discontinuous or otherwise conformationally sensitive epitopes. When SF-2 gp120 was used, four of eight serum samples reacted significantly with the denatured protein, albeit with ca. 3- to 50-fold reductions in titer. Only those sera reacting with denatured SF-2 gp120 bound significantly to solid-phase-adsorbed SF-2 V3 loop peptide, and none bound to IIIB V3 loop peptide. Almost all antibody binding to reduced SF-2 gp120 was blocked by preincubation with the SF-2 V3 loop peptide, as was about 50% of the binding to native SF-2 gp120. When sera from a laboratory worker or a chimpanzee infected with IIIB were tested, the pattern of reactivity was reversed, i.e., there was significant binding to reduced IIIB gp120, but not to reduced SF-2 gp120. Binding of these sera to reduced IIIB gp120 was 1 to 10% that to native IIIB gp120 and was substantially decreased by preincubation with IIIB (but not SF-2) V3 loop peptide. To analyze which discontinuous or conformational epitopes were predominant in HIV-1-positive sera, we prebound monoclonal antibodies (MAbs) to IIIB gp120 and then added alkaline phosphatase-labelled HIV-1-positive sera. MAbs (such as 15e) that recognize discontinuous epitopes and compete directly with CD4 reduced HIV-1-positive sera binding by about 50%, whereas neutralizing MAbs to the C4, V2, and V3 domains of gp120 were either not inhibitory or only weakly so. Thus, antibodies to the discontinuous CD4-binding site on gp120 are prevalent in HIV-1-positive sera, antibodies to linear epitopes are less common, most of the antibodies to linear epitopes are directed against the V3 region, and most cross-reactive antibodies are directed against discontinuous epitopes, including regions involved in CD4 binding.

Amino Acid Sequence↗
PubMed1993

Increased viral burden and cytopathicity correlate temporally with CD4+ T-lymphocyte decline and clinical progression in human immunodeficiency virus type 1-infected individuals.

The rate of clinical progression is variable among individuals infected with human immunodeficiency virus type 1 (HIV-1). Changes in viral burden which correlate with disease status have been demonstrated in cross-sectional studies; however, a detailed longitudinal study of the temporal relationship between viral burden, CD4+ T-cell numbers, and clinical status throughout the course of infection has not been reported. Multiple longitudinal blood samples were obtained from four HIV-1-infected individuals with clinically divergent profiles. Levels of HIV-1 were measured in sequential samples of peripheral blood mononuclear cells, using both end-point dilution cultures and quantitative polymerase chain reaction methods. Serial HIV-1 isolates from each case were also evaluated to determine their biological properties in vitro. For the three patients with clinical progression, a dramatic increase in the level of HIV-1 was observed concurrent with or prior to a marked drop in CD4+ T lymphocytes. This increase in viral burden was temporally associated with the emergence of a more cytopathic viral phenotype. In contrast, consistently low levels of HIV-1 were observed in the one patient who was clinically and immunologically stable for more than a decade. Moreover, viral isolates from this patient were less cytopathic in vitro compared with HIV-1 isolates from those patients with disease progression. The temporal association between increased viral burden and CD4+ T-cell decline suggests a direct role for HIV-1 in the cytopathology of CD4+ T cells in vivo. Our results indicate that the pathogenic mechanisms responsible for CD4+ T-cell depletion may be related to both quantitative and qualitative changes in HIV-1.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Effect of amino acid changes in the V1/V2 region of the human immunodeficiency virus type 1 gp120 glycoprotein on subunit association, syncytium formation, and recognition by a neutralizing antibody.

The contributions of the first and second variable regions of the human immunodeficiency virus type 1 gp120 glycoprotein to envelope glycoprotein structure, function, and recognition by a neutralizing antibody were studied. Several mutants with substitutions in the V2 loop demonstrated complete dissociation of the gp120 and gp41 glycoproteins, suggesting that inappropriate changes in V2 conformation can affect subunit assembly. Some glycoproteins with changes in V1 or V2 were efficiently expressed on the cell surface and were able to bind CD4 but were deficient in syncytium formation and/or virus entry. Recognition of gp120 by the neutralizing monoclonal antibody G3-4 was affected by particular substitutions affecting residues 176 to 184 in the V2 loop. These results suggest that the V1/V2 variable regions of the human immunodeficiency virus type 1 gp120 glycoprotein play a role in postreceptor binding events in the membrane fusion process and can act as a target for neutralizing antibodies.

Amino Acid Sequence↗
PubMed1993

Characterization of conserved human immunodeficiency virus type 1 gp120 neutralization epitopes exposed upon gp120-CD4 binding.

Interaction with the CD4 receptor enhances the exposure on the human immunodeficiency type 1 gp120 exterior envelope glycoprotein of conserved, conformation-dependent epitopes recognized by the 17b and 48d neutralizing monoclonal antibodies. The 17b and 48d antibodies compete with anti-CD4 binding antibodies such as 15e or 21h, which recognize discontinuous gp120 sequences near the CD4 binding region. To characterize the 17b and 48d epitopes, a panel of human immunodeficiency virus type 1 gp120 mutants was tested for recognition by these antibodies in the absence or presence of soluble CD4. Single amino acid changes in five discontinuous, conserved, and generally hydrophobic regions of the gp120 glycoprotein resulted in decreased recognition and neutralization by the 17b and 48d antibodies. Some of these regions overlap those previously shown to be important for binding of the 15e and 21h antibodies or for CD4 binding. These results suggest that discontinuous, conserved epitopes proximal to the binding sites for both CD4 and anti-CD4 binding antibodies become better exposed upon CD4 binding and can serve as targets for neutralizing antibodies.

Amino Acid Sequence↗
PubMed1992

Macromolecular assemblage in the design of a synthetic AIDS vaccine.

We describe a peptide vaccine model based on the mimicry of surface coat protein of a pathogen. This model used a macromolecular assemblage approach to amplify peptide antigens in liposomes or micelles. The key components of the model consisted of an oligomeric lysine scaffolding to amplify peptide antigens covalently 4-fold and a lipophilic membrane-anchoring group to further amplify noncovalently the antigens many-fold in liposomal or micellar form. A peptide antigen derived from the third variable domain of glycoprotein gp120 of human immunodeficiency virus type 1 (HIV-1), consisting of neutralizing, T-helper, and T-cytotoxic epitopes, was used in a macromolecular assemblage model (HIV-1 linear peptide amino acid sequence 308-331 in a tetravalent multiple antigen peptide system linked to tripalmitoyl-S-glycerylcysteine). The latter complex, in liposome or micelle, was used to immunize mice and guinea pigs without any adjuvant and found to induce gp120-specific antibodies that neutralize virus infectivity in vitro, elicit cytokine production, and prime CD8+ cytotoxic T lymphocytes in vivo. Our results show that the macromolecular assemblage approach bears immunological mimicry of the gp120 of HIV virus and may lead to useful vaccines against HIV infection.

AIDS Vaccines↗
PubMed1992

Anti-idiotype monoclonal antibody elicits broadly neutralizing anti-gp120 antibodies in monkeys.

Murine monoclonal antibodies (mAbs) were raised against human, polyclonal, anti-gp120 antibodies (Ab1) and were selected for binding to broadly neutralizing anti-gp120 antibodies in sera positive for human immunodeficiency virus (HIV). One anti-idiotype mAb (Ab2), 3C9, was found to be specific for human anti-gp120 antibodies directed against an epitope around the conserved CD4 attachment site of gp120. The 3C9 reactive human anti-gp120 antibodies (3C9+ Ab) neutralized MN, IIIB, RF, and four primary isolates of HIV type 1 (HIV-1). Cynomolgus monkeys were immunized with 3C9 in adjuvant to test whether this anti-idiotype mAb could induce neutralizing anti-gp120 antibodies. The results show that purified anti-anti-idiotype antibodies (Ab3) from 3C9 immune sera bind to an epitope around the CD4 attachment site of gp120SF and gp120IIIB. Furthermore, purified gp120-specific Ab3 neutralize MN, IIIB, and RF isolates. These results demonstrate that primates immunized with an anti-idiotype mAb produce broadly neutralizing anti-HIV-1 antibodies. Since this anti-idiotype mAb was selected by identifying a clonotypic marker, its biological activity can be explained as the results of clonotypic B-cell stimulation.

Animals↗
PubMed1992

Human T lymphotropic virus types I- and II-specific antibody-dependent cellular cytotoxicity: strain specificity and epitope mapping.

Antibody-dependent cellular cytotoxicity (ADCC) against human T lymphotropic virus (HTLV) types I and II was investigated using sera obtained from infected individuals or from rabbits immunized with HTLV-I or -II envelope peptides. Target cells included an HTLV-I-transformed cell line (C91/PL), an HTLV-II-transformed cell line (729pH6neo), and Epstein Barr virus (EBV)-transformed B lymphocytes expressing HTLV-I or -II env or gag gene products after infection with vaccinia/HTLV recombinants. ADCC activity was directed at HTLV-I and -II envelope glycoproteins but not against core (gag) components. In contrast to the human immunodeficiency virus system, significant cross-reactivity between HTLV-I- and -II-directed ADCC activity was observed. Epitope mapping studies using sera from rabbits that had been immunized with HTLV-I or -II envelope peptides suggested that the critical epitopes for ADCC activity are located primarily in hydrophilic regions of the exterior (gp46) part of the envelope glycoprotein.

Animals↗
PubMed1992

Identification and quantitation of HIV-1 in the liver of patients with AIDS.

OBJECTIVE: To detect and quantify HIV-1 in the liver in vivo. DESIGN: Fourteen liver biopsy samples and corresponding blood lymphocytes and monocytes from patients with AIDS were studied for HIV-1 using quantitative polymerase chain reaction (PCR). In addition, expression of HIV-1 antigen and messenger (m) RNA in 10 autopsy liver specimens was examined by immunohistochemistry and in situ hybridization. RESULTS: The amount of HIV-1 DNA in nine liver samples ranged from 850 to 27,000 copies per 10(6) cells, with mean and median values of 8150 and 3500 copies per 10(6) cells, respectively. Five other samples had no detectable HIV-1 DNA by PCR. Intracellular expression of HIV-1 antigen and mRNA was also detected in both Kupffer cells and hepatocytes by in situ studies. CONCLUSION: These findings strongly indicate that HIV-1 could replicate in the liver of a majority of patients with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Rapid generation of sequence variation during primary HIV-1 infection.

OBJECTIVE: HIV-1 undergoes extensive genetic variation in infected individuals. The extent of genetic variation has been examined in patients with AIDS, but little is known regarding the appearance of HIV-1 genetic variation immediately following infection during the primary phase of HIV-1 infection prior to seroconversion. DESIGN: We examined HIV-1 genetic variation during this early phase of HIV-1 infection by polymerase chain reaction (PCR) and nucleotide sequence analysis of the V4 by polymerase chain reaction (PCR) and nucleotide sequence analysis of the V4 variable region and the CD4-binding domain. RESULTS: Our results demonstrate that extensive sequence variation is seen early after infection, although a predominant HIV-1 species is maintained. CONCLUSIONS: The type of variants that occur are dynamic, changing over time, and the mutations seen are consistent with those expected from random occurrence, unlike the pattern of variation previously reported during later stages of disease.

Adult↗
PubMed1992

Virions of primary human immunodeficiency virus type 1 isolates resistant to soluble CD4 (sCD4) neutralization differ in sCD4 binding and glycoprotein gp120 retention from sCD4-sensitive isolates.

Primary isolates of human immunodeficiency virus type 1 (HIV-1) are much less sensitive to neutralization by soluble CD4 (sCD4) and sCD4-immunoglobulin (Ig) chimeras (CD4-IgG) than are HIV-1 strains adapted to growth in cell culture. We demonstrated that there are significant reductions (10- to 30-fold) in the binding of sCD4 and CD4-IgG to intact virions of five primary isolates compared with sCD4-sensitive, cell culture-adapted isolates RF and IIIB. However, soluble envelope glycoproteins (gp120) derived from the primary isolate virions, directly by detergent solubilization or indirectly by recombinant DNA technology, differed in affinity from RF and IIIB gp120 by only one- to threefold. The reduced binding of sCD4 to these primary isolate virions must therefore be a consequence of the tertiary or quaternary structure of the envelope glycoproteins in their native, oligomeric form on the viral surface. In addition, the rate and extent of sCD4-induced gp120 shedding from these primary isolates was lower than that from RF. We suggest that reduced sCD4 binding and increased gp120 retention together account for the relative resistance of these primary isolates to neutralization by sCD4 and CD4-IgG and that virions of different HIV-1 isolates vary both in the mechanism of sCD4 binding and in subsequent conformational changes in their envelope glycoproteins.

Amino Acid Sequence↗