Showing papers by "David C. Montefiori published in 1993"

V3-specific neutralizing antibodies in sera from HIV-1 gp160-immunized volunteers block virus fusion and act synergistically with human monoclonal antibody to the conformation-dependent CD4 binding site of gp120. NIH-NIAID AIDS Vaccine Clinical Trials Network.

Abstract: Sera from 11 volunteers immunized with a recombinant HIV-1 gp160-expressing vaccinia virus (HIVAC-1e; Oncogen/Bristol-Myers Squibb, Seattle, WA) and boosted with baculovirus-derived rgp160 (VaxSyn; MicroGeneSys, Inc., Meriden, CT) were evaluated for functional serum antibodies and their epitopes. Sera obtained prior to boosting had undetectable HIV-1-specific IgG and neutralizing activity, and did not block HIV-1 from binding or fusing to CD4+ MT-2 cells. 14 d after boosting, sera from each volunteer contained HIV-1-specific IgG titers of 1:40 to 1:1,280. Five of these sera also contained neutralizing antibodies, where most or all neutralizing activity was blocked by a synthetic peptide corresponding to amino acids 307-330 of the V3 loop of gp120, indicating that neutralizing antibodies were mostly V3 loop-specific. All sera obtained after boosting contained HIV-1 binding/fusion-inhibition antibodies, and a significant portion of their activity was blocked by the V3 loop peptide, a result consistent with the presence of antibodies against the region of the V3 loop that participates in fusion. Three sera with V3 loop-specific neutralizing and fusion-inhibition antibodies were studied further. In competitive antibody binding experiments, antibodies reactive with the conformation-dependent, CD4 binding site of gp120 were undetectable in each serum. When evaluated in combination with a monoclonal antibody to the CD4 binding site of gp120, two sera demonstrated synergism in neutralizing assays, and all three sera demonstrated synergism in binding/fusion-inhibition assays, further indicating that the functional antibodies were primarily V3 loop-specific. The synergism also suggests that a vaccine that elicits strong serum antibody responses to both regions of gp120 may improve the potential for inducing protective immunity.

Complement-mediated binding of naturally glycosylated and glycosylation-modified human immunodeficiency virus type 1 to human CR2 (CD21).

Abstract: Particulate glycoproteins lacking sialic acid, such as desialylated enveloped viruses, readily activate complement through the alternative pathway. Human immunodeficiency virus type 1 (HIV-1) contains two heavily glycosylated and partially sialylated envelope glycoproteins: a surface gp120 and a transmembrane gp41. The abilities of naturally glycosylated HIV-1 and glycosylation-modified HIV-1 to interact with the complement system were examined with a biological assay which measured the binding of whole virus particles to cells expressing CR2 (CD21), the complement receptor found naturally in abundance on follicular dendritic cells and immature B cells. HIV-1 IIIB was synthesized in the presence or absence of the mannosidase II inhibitor, swainsonine, to give rise to high-mannose-type, nonsialylated, nonfucosylated carbohydrate moieties. The virus also was treated with neuraminidase or endo-beta-galactosidase to remove terminal sialic acids. An enzyme immunoassay specific for HIV-1 p24 core protein was used to quantitate the amount of virus bound to cell surfaces. Virus particles incubated with 1:3-diluted, fresh HIV-1-negative human serum as a source of complement readily bound to MT-2 (CD4+ CR2+) and Raji-3 (CD4- CR2+) cells but not to CEM (CD4+ CR2-) cells, suggesting that the virus bound to CR2 independently of CD4. Compared with heat-inactivated or C3-deficient sera, fresh complement increased binding by as much as 62 times for naturally glycosylated virus, and 5 times more than this for glycosylation-modified virus. Similar observations were made with freshly isolated, non-mitogen-stimulated peripheral blood mononuclear cells. Additional evidence that HIV-1 bound to CR2 independently of CD4 was provided by the fact that binding was blocked by monoclonal antibody OKB7 (anti-CR2) but not by OKT4a (anti-CD4). Also, the virus bound to transfected K562 cells (CD4-) which expressed recombinant human CR2 but did not bind to untransfected K562 cells. Results obtained with complement component-deficient sera indicated that binding required the alternative complement pathway. Raji-3 and transfected K562 cells could not be infected with HIV-1 in the presence of complement, suggesting that utilization of CR2 as a receptor in the absence of CD4 does not allow virus entry. The demonstration of CR2 as a receptor for HIV-1 in the presence of complement, together with the ability to enhance binding by desialylation, provides new insights into mechanisms of HIV-1-induced immunity and immunopathogenesis.

Synthesis and anti-HIV activity of a series of 2-indolinones and related analogues

Abstract: Summary A novel series of 2-indolinones with in vitro anti-HIV (human immunodeficiency virus) activity is described. Two structurally related compounds, 1, 3,3­ (4-N-methyl-1,2,5,6-tetrahydroPYlidylmethyl)-1- phe­ nyl-2-indolinone, and 2, its 4-N-methylpiperidinylme-· thyl analogue (Fig. 1), formed the basis of a structure­ activity study. The synthesis of approximately 50 analogues and their respective activities vs. HIV are presented. Both 1 and 2 were effective inhibitors of HIV(lIIb) in cell protection assays with ICgovalues of 4.4 and 14.9[1M (2.2 and 7.9[1g rnr"), respectively. In the same concentration range, 1 and 2also inhibitsyncytia formation. These compounds represent a novel class of anti-HIV agents which appear to act by inhibiting virus-dependent cell fusion.