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C R Alving

Publications and source records attributed to C R Alving.

At least 55 records · Page 3Linked to original sources
PubMed1995

Induction of protective polyclonal antibodies by immunization with a Plasmodium yoelii circumsporozoite protein multiple antigen peptide vaccine.

Monoclonal Abs against the repeat region of the circumsporozoite protein (CSP) completely protect mice against Plasmodium yoelii (Py), but synthetic peptide and recombinant protein vaccines designed to produce only Abs to the PyCSP repeat region have never been reported to consistently provide protection. This lack of protection in the rodent model system has predicted the poor protection achieved in humans after immunization with synthetic peptide and recombinant protein P. falciparum CSP vaccines and has raised serious questions regarding the capacity for vaccine-induced polyclonal Abs against the CSP to consistently protect humans. We now report immunization studies with a multiple Ag peptide vaccine designed to rely on "universal" T epitopes from tetanus toxin to produce T cell help for induction of protective Abs against the repeat region of the PyCSP. When delivered with a nonionic block co-polymer adjuvant, the vaccine protected 78 to 100% of three inbred strains of mice, and 100% of outbred mice against P. yoelii sporozoite challenge. Protection was associated with Ab titer, and passive transfer of purified IgG from immune mice protected naive recipients. Similar protection was achieved when the peptide was encapsulated in liposomes with lipid A and mixed with aluminum hydroxide. By demonstrating for the first time solid protection against P. yoelii by polyclonal Abs against the CSP, these data provide the rationale for assessment of a similarly constructed and formulated P. falciparum CSP multiple Ag peptide vaccine in humans.

Amino Acid Sequence↗
PubMed1995

Antibody and cytotoxic T-lymphocyte responses to a single liposome-associated peptide antigen.

The development of peptide-based vaccines that elicit antibody (Ab) and cellular immune responses has been hampered by the lack of highly immunogenic formulations. In this study, we compared the induction of Ab and cytotoxic T-lymphocyte (CTL) responses to a peptide derived from the V3 loop of HIV-1 gp120 (P18 and its cysteine-glycine derivative (CG-P18)) when incorporated into liposomes with lipid A (LA) or mixed with aluminum hydroxide. P18-specific CTL were only observed with liposomes with LA. P18-specific Ab responses were found with liposomes containing CG-P18 but not P18. Increased surface expression of the former, resulted in enhancement of the Ab response without loss of CTL induction. Thus, the manner in which a peptide is localized can influence the outcome of the response induced by highly immunogenic liposome formulations.

Amino Acid Sequence↗
PubMed1995

Liposomes as carriers of peptide antigens: induction of antibodies and cytotoxic T lymphocytes to conjugated and unconjugated peptides.

In the quest for effective immunization against complex diseases such as cancer, parasitic diseases, AIDS, and other viral infections, numerous peptides and recombinant proteins have been synthesized, examined for the ability to induce antibodies and CTLs, and tested for binding capability and therapeutic or prophylactic efficacy against the original target cell or organism. A liposome formulation, consisting of alum-adsorbed liposomes containing both a potent adjuvant, lipid A, and encapsulated or surface bound antigen, has had a record of safety and strong effectiveness for induction of antibodies in human vaccine trials. These same liposomes can also serve as effective vehicles for delivering conjugated or unconjugated peptides and proteins to antigen presenting cells for presentation via MHC class I and class II pathways for induction of CTLs and antibodies in experimental animal models. Liposomal lipid A appears to be extremely important, and is often a requirement, as an adjuvant for induction of CTLs against liposomal peptide antigens. Computer-generated molecular modelling analysis of small unconjugated or lipid-conjugated peptides strongly suggests that the expression of peptide antigen on the surface of the liposomes can be an important factor both in the induction of antibodies and in determining antibody specificities to small peptides. However, antigenic surface expression of liposomal peptide is not required for induction of CTLs. The data suggest that small synthetic peptides, synthesized with or without a lipid tail, or chemically conjugated to the surface of liposomes, might serve as effective antigenic epitopes, in combination with liposomal lipid A for induction of antibodies and CTLs.

Amino Acid Sequence↗
PubMed1995

Intracellular processing of liposome-encapsulated antigens by macrophages depends upon the antigen.

Two proteins, a recombinant malaria protein (R32NS1) and conalbumin, were encapsulated in separate liposomes. The mechanisms of presentation of unencapsulated and liposome-encapsulated R32NS1 and conalbumin to antigen-specific T-cell clones were investigated in in vitro antigen presentation assays using murine bone marrow-derived macrophages (BMs) as antigen-presenting cells. A much lower concentration of liposomal antigen than of unencapsulated antigen was required for T-cell proliferation. Liposome-encapsulated conalbumin required intracellular processing by BMs for antigen-specific T-cell proliferation, as determined by inhibition with chloroquine, NH4Cl, leupeptin, brefeldin A, monensin, antimycin A, NaF, and cycloheximide and by treatment of BMs with glutaraldehyde. Liposome-encapsulated conalbumin therefore follows the classical intracellular antigen processing pathway described for protein antigens. Similarly, unencapsulated conalbumin also required intracellular processing for presentation to antigen-specific T cells. In contrast, both unencapsulated R32NS1 and liposome-encapsulated R32NS1 were presented to T cells by BMs without undergoing internalization and intracellular processing. These results suggest that the antigen itself is the major element that determines whether a requirement exists for intracellular processing of liposomal antigens by macrophages.

Amino Acid Sequence↗
PubMed1995

A vaccine-elicited, single viral epitope-specific cytotoxic T lymphocyte response does not protect against intravenous, cell-free simian immunodeficiency virus challenge.

Protection against simian immunodeficiency virus (SIV) challenge was assessed in rhesus monkeys with a vaccine-elicited, single SIV epitope-specific cytotoxic T-lymphocyte (CTL) response in the absence of SIV-specific antibody. Strategies were first explored for eliciting an optimal SIV Gag epitope-specific CTL response. These studies were performed in rhesus monkeys expressing the major histocompatibility complex (MHC) class I gene Mamu-A*01, a haplotype associated with a predominant SIV CTL epitope mapped to residues 182 to 190 of the Gag protein (p11C). We demonstrated that a combined modality immunization strategy using a recombinant Mycobacterium bovis BCG-SIV Gag construct for priming, and peptide formulated in liposome for boosting, elicited a greater p11C-specific CTL response than did a single immunization with peptide-liposome alone. Vaccinated and control monkeys were then challenged with cell-free SIVmne by an intravenous route of inoculation. Despite a vigorous p11C-specific CTL response at the time of virus inoculation, all monkeys became infected with SIV. gag gene sequencing of the virus isolated from these monkeys demonstrated that the established viruses had no mutations in the p11C-coding region. Thus, the preexisting CTL response did not select for a viral variant that might escape T-cell immune recognition. These studies demonstrate that a potent SIV-specific CTL response can be elicited by combining live vector and peptide vaccine modalities. However, a single SIV Gag epitope-specific CTL response in the absence of SIV-specific antibody did not provide protection against a cell-free, intravenous SIV challenge.

Animals↗
PubMed1995

Complement activation by liposome-encapsulated hemoglobin in vitro: the role of endotoxin contamination.

Incubation of liposome-encapsulated Hb (LEH) with rat serum at 37 degrees C led to accelerated decay of serum hemolytic complement (C) activity (CH50/ml). Empty liposomes (L) caused less decrease of CH50/ml, whereas free Hb had no effect on C activity. The LEH- and L-induced increases in C consumption were unlikely a consequence of endotoxin (LPS) contamination, as spiking of rat serum with LPS caused reduction in C only at levels significantly higher than those detectable in LEH or L. LPS-induced C consumption was not potentiated by free hemoglobin.

Animals↗
PubMed1994

Complement activation in rats by liposomes and liposome-encapsulated hemoglobin: evidence for anti-lipid antibodies and alternative pathway activation.

Intravenous injection of hemoglobin-containing liposomes (LEH) caused a significant reduction in plasma hemolytic complement activity in rats on a time scale of minutes. Liposomes without hemoglobin also caused complement consumption, but less than LEH, while free hemoglobin was without effect. Consistent with complement activation, the LEH-induced drop in plasma hemolytic complement activity was closely paralleled by an increase in plasma thromboxane B2 level. Studies to determine the mechanism of complement activation demonstrated the presence of natural antibodies in rat serum against all lipid components of LEH, thus, the potential for classical pathway activation. Yet, in vitro incubation of LEH with rat serum showed that: 1) EGTA/Mg++, which inhibits complement activation through the classical pathway, did not inhibit complement consumption by LEH, and 2) the use of serum preheated at 50 degrees C, which inhibits C activation through the alternative pathway by selectively depleting factor B, effectively reversed the complement-consuming effect of LEH. Consequently, LEH-induced complement activation in rat serum seems to involve primarily the alternative pathway.

Animals↗
PubMed1994

Liposomes as carriers for vaccines.

A liposome vaccine formulation that has been successfully used in both animal immunization studies and clinical trials is described. Issues concerning the choice of components for the liposomal vaccine formulation are discussed, especially with respect to the lipid components and the adjuvant. A procedure is described for manufacturing liposomal vaccines using Good Manufacturing Practices as promulgated by the U.S. Food and Drug Administration. Quality control testing for clinical use is described, with particular emphasis on aspects relevant to liposomes. Utilization issues are discussed, including injection volumes, antigen and adjuvant doses, and routes of administration.

AIDS Vaccines↗
PubMed1994

Cytotoxic T lymphocytes induced by liposomal antigens: mechanisms of immunological presentation.

It is known that liposomes can deliver encapsulated substances, including drugs and antigens, to lysosomes in macrophages. Because of this it has been assumed that although liposomes might be useful for induction of humoral (class II) immunity, they would not be capable of cytoplasmic delivery of antigen for introduction into the class I pathway leading to induction of cytotoxic T lymphocytes (CTLs). However, experiments conducted by numerous laboratories, including our own, have demonstrated the ability to induce CTLs either in vitro with cultured cells incubated with liposome-associated antigen, or in vivo after immunization of mice or monkeys with liposomes containing associated antigen. Using a monoclonal antibody that recognizes repeating sequences of tetrapeptide epitopes derived from the circumsporozoite protein of Plasmodium falciparum, it has been shown by immunogold electron microscopy that liposomal antigenic epitopes can actually spill from endosomes into the cytoplasm of cultured macrophages. On the basis of this observation, a theoretical intracellular pathway is proposed whereby liposomal antigen is processed by macrophages through a cytoplasmic process that results in delivery of antigenic epitopes to the Golgi apparatus and the endoplasmic reticulum. The liposomal antigenic epitopes would then have the opportunity to associate with class I MHC molecules and undergo vesicular transport to the surface of the cells for presentation and induction of CTLs.

Animals↗
PubMed1993

Novel adjuvant strategies for experimental malaria and AIDS vaccines.

Adjuvant research has improved the ability of biotechnology to generate novel vaccines. Numerous strategies for enhancing the immunogenicity of synthetic peptides and proteins have been identified. This overview focuses on adjuvant development and vaccine delivery systems that provide new tools for amplifying the effectiveness of ongoing malaria and AIDS vaccine development programs. In addition, some of the complex challenges and issues that have become associated with the delivery of modern vaccines in man are outlined. As adjuvant research continues to open new opportunities in vaccine development, there is renewed expectation that further generations of safe and potent vaccines will be possible against a broad spectrum of infectious agents and cancer.

AIDS Vaccines↗
PubMed1993

ATP specifically bound as a hapten to a monoclonal anti-phospholipid antibody retains phosphate donor activity.

We have previously reported that each of four monoclonal antibodies to a phospholipid, phosphatidylinositol phosphate (PIP), has a phosphate binding subsite in the antigen binding site that can bind ATP (Molec. Immunol. 21, 863-868, 1984). We have now observed that antibody-bound ATP has the ability to donate a phosphate group in the phosphorylation reaction of glucose to glucose-6-phosphate catalyzed by hexokinase. The phosphorylation reaction proceeds equally efficiently when ATP is provided as free (nonbound) ATP or as antibody-bound ATP. We conclude that an anti-phospholipid antibody can serve as a carrier of a functionally active nucleotide.

Adenosine Triphosphate↗
PubMed1993

Gangliosides elicit a T-cell independent antibody response.

Antibodies to glycolipids have recently been found to be elevated in a substantial proportion of patients with motor neuron diseases, various neuropathies and classical ALS. Several features of these antibody responses suggest that they may be produced by a T-cell independent B lymphocyte response: (1) antibodies are predominantly of IgM class; (2) antibodies against gangliosides are directed against the carbohydrate component of the gangliosides; and (3) antiganglioside antibodies are difficult to suppress. In this study we have asked whether gangliosides can induce T-independent responses, in T-cell deficient and T-cell competent mice. Homozygous nude mice (nu/nu), which lack T-cells, and heterozygous controls (nu/+) with intact T-cells, were immunized and rechallenged with the ganglioside GM1 in liposomes. Antibodies were measured by an ELISA method. Both nude mice and controls produced high titers of IgM class antibodies to the ganglioside GM1. The antibody titers peaked by 7 days after each immunization and declined by 14 days. The maximum titer rose progressively after each immunization. No significant amount of IgG antibody to GM1 was produced by either nu/nu or nu/+ mice, even after repeated immunization. These results suggest that gangliosides elicit prominent T-cell-independent antibody responses. The implications of these findings for neurologic disorders associated with anti-ganglioside antibodies are discussed.

Animals↗
PubMed1993

Complement-dependent phagocytosis of liposomes.

In this article we describe an in vitro model for complement-dependent phagocytosis of liposomes. We have previously reported that complement-opsonized liposomes are avidly ingested by murine peritoneal or bone marrow-derived cultured macrophages. However, when the liposomes contained certain lipids, including phosphatidylinositol, ganglioside GM1, and sulfogalactosyl ceramide, that have been identified as causing prolonged circulation time in vivo, complement-dependent phagocytosis of the liposomes was greatly suppressed. We identify certain additional factors associated with suppressed complement-dependent phagocytosis, including, liposomal negative charge and liposomal prostaglandin E2 or thromboxane B2. Possible mechanisms responsible for suppression of complement dependent phagocytosis are suggested. We propose that suppression of complement-dependent phagocytosis could be a contributing factor in the promotion of increased circulation time of 'stealth' liposomes and that complement opsonization probably plays a role in vivo in removing liposomes from the circulation.

Animals↗
PubMed1993

Induction of cytolytic and antibody responses using Plasmodium falciparum repeatless circumsporozoite protein encapsulated in liposomes.

Plasmodium circumsporozoite (CS) protein-induced antibody and T-cell responses are considered to be important in protective immunity. Since the key repeat determinant of the CS protein may actually restrict the recognition of other potential T- and B-cell sites, a modified Plasmodium falciparum CS protein lacking the central repeat region, RLF, was expressed in Escherichia coli. On purification, RLF was encapsulated into liposomes [L(RLF)] and used for the in vivo induction of cytolytic T lymphocytes (CTL) and antibodies. Immunization of B10.Br (H-2k) mice with L(RLF), but not with RLF, induced CD8+ CTL specific for the P. falciparum CS protein CTL epitope, amino acid residues 368-390. Anti-L(RLF) serum reacted with antigens on intact sporozoites and inhibited sporozoite invasion of hepatoma cells. Antibody specificity studies in New Zealand White rabbits revealed new B-cell sites localized in amino acid residues 84-94, 91-99, 97-106 and 367-375. Although the mechanisms by which liposomes enhance cellular and humoral immune responses remain unknown, liposome-formulated vaccines have been well tolerated in humans; hence, their use in vaccines, when efficacy depends on antibody and CTL responses, may be broadly applicable.

Amino Acid Sequence↗
PubMed1993

Lipopolysaccharide, lipid A, and liposomes containing lipid A as immunologic adjuvants.

Numerous studies have demonstrated that most or all of the potent adjuvant activity of Gram-negative bacterial endotoxin resides in the lipid A moiety of lipopolysaccharide (LPS). Synthetic analogues of lipid A have provided insights into structure-activity relationships. Several cellular mechanisms of LPS and lipid A adjuvant activities have been identified. Activation of macrophages by LPS or lipid A results in cytokine secretions that enhance the immune response. LPS and lipid A cause recruitment of antigen-presenting cells, particularly macrophages. Liposomes containing lipid A serve as an in vivo adjuvant to recruit increased numbers of macrophages. Liposomal lipid A that has been phagocytized by cultured macrophages also serves as an "intracellular adjuvant" to cause increased immunologic presentation of liposomal antigen by the macrophages to specific T lymphocytes. Lipid A can abolish suppressor T cell activity, resulting in increased immune responses to polysaccharide antigens. Upon combination of lipid A or lipid A analogues with nonionic block polymers, modulation of murine antibody isotypes can be achieved with antibodies against a variety of antigens in vivo. Liposomes containing monophosphoryl lipid A (MPL) have been utilized in a phase I clinical trial of a proposed malaria vaccine in humans. The liposomal malaria vaccine resulted in very high levels of antibodies against the malarial antigen, and despite the presence of huge amounts of MPL (up to 2.2 mg), the liposomal lipid A was nonpyrogenic and safe for use in humans. Lipid A and lipid A analogues, and liposomes or other carriers containing lipid A, have shown considerable promise both as adjuvants for immunization of animals and for human vaccines.

Adjuvants, Immunologic↗
PubMed1992

Liposomal malaria vaccine in humans: a safe and potent adjuvant strategy.

This study describes the safety and immunogenicity of a liposome-based vaccine injected into human subjects. Thirty healthy adult male volunteers were immunized with a liposome-encapsulated recombinant protein (R32NS181) containing epitopes from the repeat region of the circumsporozoite protein of Plasmodium falciparum. This antigen had previously been found to be poorly immunogenic in humans when it was adsorbed with Al(OH)3. In the present study, R32NS181 was encapsulated in liposomes containing monophosphoryl lipid A that were subsequently adsorbed to Al(OH)3. Increasing doses of liposomes containing antigen and monophosphoryl lipid A were used, but the liposomes were always adsorbed to the same dose of Al(OH)3. R32-specific serum IgG antibody responses to liposome-encapsulated R32NS181 were much higher than levels attained previously in humans with R32NS181 adsorbed to Al(OH)3. Geometric mean specific IgG levels after three doses ranged from 14 to 33 micrograms/ml. Sera from volunteers receiving the two highest doses inhibited P. falciparum sporozoite invasion of cultured hepatoma cells by an average of 92%, a result that was again superior to previously reported vaccines. Moderate but acceptable transient local reactogenicity was noted at high doses of the vaccine formulation, but little or no systemic toxicity was seen despite liposomal monophosphoryl lipid A doses up to 2200 micrograms. We conclude that encapsulation of poorly immunogenic circumsporozoite protein repeat peptides in monophosphoryl lipid A-containing liposomes is a successful adjuvant strategy in humans for inducing high levels of specific antibody production.

Adjuvants, Immunologic↗