ABSTRACT
A main effector mechanism of rituximab (RTX) is the induction of complement-dependent cytotoxicity (CDC). However, this effector function is limited, because CLL cells are protected from complement-induced damage by regulators of complement activation (RCAs). A prominent RCA in fluid phase is factor H (fH), which has not been investigated in this context yet. Here, we show that fH binds to CLL cells and that human recombinant fH-derived short-consensus repeat 18-20 (hSCR18-20) interferes with this binding. In complement-based lysis assays, CLL cells from therapy-naive patients were differently susceptible to RTX-induced CDC and were defined as CDC responder or CDC non-responder, respectively. In CDC responders, but notably also in non-responders, hSCR18-20 significantly boosted RTX-induced CDC. Killing of the cells was specific for CD20(+) cells, whereas CD20(-) cells were poorly affected. CDC resistance was independent of expression of the membrane-anchored RCAs CD55 and CD59, although blocking of these RCAs further boosted CDC. Thus, inhibition of fH binding by hSCR18-20 sensitizes CLL cells to CDC and may provide a novel strategy for improving RTX-containing immunochemotherapy of CLL patients.
Subject(s)
Antibodies, Monoclonal, Murine-Derived/pharmacology , Antibody-Dependent Cell Cytotoxicity/immunology , Complement Activation/immunology , Cytotoxicity, Immunologic/immunology , Leukemia, Lymphocytic, Chronic, B-Cell/immunology , Leukemia, Lymphocytic, Chronic, B-Cell/pathology , Antineoplastic Agents/pharmacology , Blotting, Western , Complement Factor H/immunology , Complement Factor H/metabolism , Flow Cytometry , Humans , Leukemia, Lymphocytic, Chronic, B-Cell/drug therapy , Leukemia, Lymphocytic, Chronic, B-Cell/metabolism , Prognosis , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Recombinant Proteins/metabolism , Rituximab , Tumor Cells, CulturedABSTRACT
In both human immunodeficiency virus-infected humans and simian immunodeficiency virus (SIV)-infected macaques, genes encoded in the major histocompatibility complex (MHC) class I region are important determinants of disease progression. However, compared to the human human lymphocyte antigen complex, the macaque MHC region encodes many more class I genes. Macaques with the same immunodominant class I genes express additional Mhc genes with the potential to influence the disease course. We therefore assessed the association between of the Mhc class I haplotypes, rather than single gene variants, and survival time in SIV-infected rhesus macaques (Macaca mulatta). DNA sequence analysis and Mhc genotyping of 245 pedigreed monkeys identified 17 Mhc class I haplotypes that constitute 10 major genotypes. Among 81 vaccination-naive, SIV-infected macaques, 71 monkeys carried at least one Mhc class I haplotype encoding only MHC antigens that were incapable of inducing an effective anti-SIV cytotoxic T lymphocytes response. Study of these macaques enabled us to relate individual Mhc class I haplotypes to slow, medium and rapid disease progression. In a post hoc analysis, classification according to disease progression was found to explain at least 48% of the observed variation of survival time.
Subject(s)
Haplotypes , Histocompatibility Antigens Class I/genetics , Simian Acquired Immunodeficiency Syndrome/genetics , Simian Immunodeficiency Virus/immunology , Alleles , Animals , Cohort Studies , Disease Progression , Gene Frequency , Histocompatibility Antigens Class I/immunology , Macaca mulatta , Simian Acquired Immunodeficiency Syndrome/immunology , Statistics as Topic , Survival AnalysisABSTRACT
We studied the central nervous system (CNS) of rhesus macaques during series of vaccination experiments in which attenuated simian immunodeficiency virus (SIV), SIVmac239Deltanef, was applied to the tonsils and the animals were later challenged with pathogenic SIVmac251 or SHIV/89.6P via tonsils or rectum. The pathologic lesions were graded on a scale of 0-5. The lesions were in general very mild, with a score of 0.5, except for one case, in which the animal had progressed to simian AIDS (SAIDS) and had severe lesions of grade 4. Except for the SAIDS case, the most common lesions were meningitis, ependymitis, inflammation of choroid plexus, and astrocytosis. Invasion of the challenge virus, SIVmac251, and pathologic lesions were detected 4 days post infection. The main features of the pathological lesions were similar during short-term follow-up (4 days to 2 weeks) and long-term follow-up (23 to 56 weeks) after challenge. No significant difference was found between unvaccinated controls infected with the challenge viruses and vaccinated and challenged animals. The pathological lesions in the one SAIDS case consisted of extensive lesions of the white matter in connection with confluent ependymitis, indicating an invasion through the choroid plexus. The lesions were characterized by a myriad of multinucleated giant cells of macrophage origin, which showed, together with individual macrophages, strong labelling for viral RNA and proteins. Productive infection of astrocytes was a very rare finding. In three cases infected via tonsils with SIVmac239Deltanef without challenge, we detected expression of Nef-derived peptides, indicating a selective pressure for Nef functions in the CNS.
Subject(s)
Brain/pathology , Immunity, Mucosal , Palatine Tonsil , SAIDS Vaccines/adverse effects , Simian Acquired Immunodeficiency Syndrome/prevention & control , Animals , Female , Genes, nef , Immunohistochemistry , In Situ Hybridization , Macaca mulatta , Male , Mucous Membrane , RNA, Viral/isolation & purification , SAIDS Vaccines/administration & dosage , Simian Acquired Immunodeficiency Syndrome/pathology , Simian Immunodeficiency Virus , Vaccines, Attenuated/adverse effectsABSTRACT
In a case-control study that included a total of 98 patients and 83 controls, the possible link between various pathogens and abdominal aortic aneurysms was investigated. For 68 patients with abdominal aortic aneurysm and age-matched controls, no differences were detected in the levels of immunoglobulin (Ig)A and IgG Chlamydiaceae and Chlamydophila pneumoniae antibodies. Patients with IgA titers positive for Chlamydophila pneumoniae showed progressive disease (defined as an annual increase of the aneurysm diameter of > or = 0.5 cm) more frequently than patients with negative IgA titers (p = 0.046). Polymerase chain reactions performed to detect DNA for Chlamydophila pneumoniae, Chlamydia trachomatis, Chlamydophila psittaci, human cytomegalovirus, Borrelia burgdorferi and Helicobacter pylori in tissue specimens of 30 patients and 15 controls were negative. In summary, Chlamydophila pneumoniae may contribute to aortic aneurysm disease progression, but DNA of this and other pathogens was not found in patients' specimens.
Subject(s)
Antibodies, Bacterial/blood , Aorta, Abdominal/microbiology , Aortic Aneurysm, Abdominal/microbiology , Chlamydiaceae/immunology , Chlamydophila pneumoniae/immunology , DNA, Bacterial/analysis , Aged , Aged, 80 and over , Case-Control Studies , Chlamydia Infections/immunology , Chlamydia Infections/microbiology , Chlamydiaceae/genetics , Chlamydiaceae/isolation & purification , Chlamydiaceae Infections/immunology , Chlamydiaceae Infections/microbiology , Chlamydophila pneumoniae/genetics , Chlamydophila pneumoniae/isolation & purification , Female , Humans , Immunoglobulin A/blood , Immunoglobulin G/blood , MaleABSTRACT
Ovarian cancer is potentially well suited for local monoclonal antibody (mAb) immunotherapy, because it remains within the peritoneal cavity for a long period of time before giving rise to distant metastases. At the stage of minimal residual disease, the cells appear to be in a state of dormancy (G(0)) or at least have lower rates of tumour cell proliferation. They should be a promising target for immunotherapy. Here we first examined the cell-cycle expression of CD59 and decay-accelerating factor (DAF; CD55) on four different ovarian carcinoma cell lines, using simultaneous flow cytometric analysis of DNA content or the cell-cycle-specific nuclear proliferation protein Ki67 and CD59 or DAF surface expression. We found that CD59 and DAF are stably expressed throughout the cell cycle. The polyvalent approach to target-independent antigens to improve the efficiency of mAb complement (C)-mediated damages was promising, and tumour cells become sensitive to C damage, when incubated with cross-linked mAb against different tumour-associated antigens. Although, such immune complex-mediated C activation was rather ineffective in killing the cells, it could be potentiated by the addition of blocking mAb against CD59 and DAF. Our results suggest that the activities of intrinsic C regulators must be neutralized to make minimal residual disease a promising target for antibody therapy.
Subject(s)
Adenocarcinoma/drug therapy , Antibodies, Blocking/therapeutic use , Antibodies, Monoclonal/therapeutic use , CD55 Antigens/drug effects , Complement System Proteins/immunology , Ovarian Neoplasms/drug therapy , Adenocarcinoma/immunology , Antigens, Neoplasm/analysis , CD55 Antigens/analysis , CD55 Antigens/metabolism , Cell Cycle , Cell Line, Tumor , DNA, Neoplasm/analysis , Female , Flow Cytometry , Humans , Immunotherapy , Ki-67 Antigen/analysis , Ki-67 Antigen/metabolism , Neoplasm, Residual , Ovarian Neoplasms/immunologyABSTRACT
During the budding process, human immunodeficiency virus (HIV) acquires several cellular proteins from the host. Thus, antibodies against self antigens found in sera patients with autoimmune disorders may cross react with host-derived or the HIV-specific proteins gp120 and gp41 on the viral envelope and probably neutralize HIV infection. To verify this hypothesis, 88 sera from HIV negative patients suffering from systemic lupus erythematosus (SLE) and other autoimmune disorders were analysed for cross reacting antibodies against HIV-1 by Western blot and FACS analysis indicating that antibodies cross-react with epitopes expressed on HIV infected or non-infected cells. Virus capture assays revealed that HIV-1(IIIB) was directly recognized by 60% of sera from patients with autoimmune disorders. Sera were also tested in HIV neutralization assays with stimulated T cells. Reduction of the viral load by patient sera correlated with their reactivity in Western blot analysis. Complement further enhanced the reduction of viral titres, although no complement-mediated lysis was observed. These data suggest a possible protective role of auto-antibodies against HIV infection in lupus patients.
Subject(s)
Autoantibodies/immunology , Connective Tissue Diseases/immunology , HIV Infections/immunology , HIV-1/immunology , Lupus Erythematosus, Systemic/immunology , Adolescent , Adult , Aged , Autoantibodies/pharmacology , Complement System Proteins/immunology , Cross Reactions , Female , Flow Cytometry , HIV Infections/prevention & control , HIV Seronegativity , HIV-1/growth & development , Humans , Male , Middle Aged , Neutralization Tests , T-Lymphocytes/cytology , T-Lymphocytes/immunology , T-Lymphocytes/virology , U937 Cells , Virus Replication/immunologyABSTRACT
The aim of this study was to correlate results of therapeutic drug monitoring, genotypic resistance and viral response to lopinavir/ritonavir (LPV/r) or saquinavir/ritonavir (SQV/r) containing antiretroviral regimens. The retrospective short-term study included 20 patients with LPV/r and 20 patients with SQV/r containing highly active antiretroviral therapy (HAART). At baseline 7 LPV/r patients and 10 SQV/r patients had CD4+T cell counts above 410 cells/microl. After 6 months CD4+T cells had doubled in 5 LPV/r and 2 SQV/r patients. In LPV/r patients the mean serum concentration of lopinavir (LPV) was 2.6 ppm and 67% of all LPV/r samples had 50 or fewer viral copies/ml. In SQV/r patients the mean serum concentration of saquinavir (SQV) was 2.1 ppm. 79% of all SQV/r samples had 50 or fewer viruses/ml. Pharmacoenhanced regimens efficiently suppress human immunodeficiency virus type 1 (HIV-1) and the risk of developing resistance mutations is therefore reduced. The implementation of drug monitoring is an additional tool to determine optimal treatment conditions.
Subject(s)
Anti-HIV Agents/therapeutic use , HIV Infections/drug therapy , HIV-1 , Pyrimidinones/therapeutic use , Ritonavir/therapeutic use , Saquinavir/therapeutic use , Adult , Anti-HIV Agents/pharmacokinetics , CD4 Antigens/genetics , Drug Monitoring , Female , Genotype , HIV Antibodies/analysis , HIV Antibodies/biosynthesis , HIV Infections/virology , HIV Protease/genetics , HIV-1/enzymology , HIV-1/genetics , Humans , Lopinavir , Male , Middle Aged , Mutation , Neopterin/blood , Pyrimidinones/pharmacokinetics , Retrospective Studies , Ritonavir/pharmacokinetics , Saquinavir/pharmacokineticsABSTRACT
The standard treatment for HIV infected patients is the highly active antiretroviral therapy. Due to resistance developments treatment failure can be found in some patients. In our study two different strategies are compared, which may reduce resistance mutations. Six patients (group A and B) have been monitored for about six years. Group A patients had a switch in their AZT-containing treatment to non AZT-containing regimens. In group B patients AZT-containing regimens' were interrupted by drug holidays. Early mono- and dual-therapies containing zidovudine (AZT) have been applied in all patients with poor long-term improvements. Due to the rapid development of escape mutants viral rebound was observed soon after treatment initiation. Genotypic assays were developed to asses AZT-resistance mutations. The longer AZT had been applied the more mutations had developed. These mutations disappeared when patients were taking "drug-holidays" and drug selection pressure was missing. Besides, it was demonstrated in two patients that these AZT-mutations could disappear, if in combination therapies AZT was replaced by other antiretroviral drugs. This study shows that not only by drug-holidays but also by switches in therapy mutations can disappear, which is especially important for patients with low CD 4 cell counts and high viral load levels.
Subject(s)
Anti-HIV Agents/therapeutic use , HIV Infections/drug therapy , HIV Reverse Transcriptase/genetics , HIV/genetics , Mutation/drug effects , Reverse Transcriptase Inhibitors/therapeutic use , Zidovudine/therapeutic use , Antiretroviral Therapy, Highly Active , CD4 Lymphocyte Count , Drug Administration Schedule , Drug Resistance, Viral/genetics , Genotype , HIV/drug effects , Humans , Treatment Outcome , Viral LoadABSTRACT
Since the first contact with the host, human immunodeficiency virus (HIV) exploits the complement system to reach maximal spread of infection. HIV has adapted many strategies to avoid complement-mediated lysis and uses the opsonization with complement fragments for attachment to complement receptors (CR). From the pathogen's perspective, binding to CR-expressing cells is remarkably beneficial, bringing together virus and activated target cells that are highly susceptible to infection. Moreover, complement-mediated trapping on CR+ cells permits HIV to infect surrounding cells even in the presence of an excess of neutralizing antibodies. Thus, complement activation initiates the assumption of power over the host's immune system by HIV and thus augments viral spread and replication throughout the body. On the other hand, natural hosts of primate lentiviruses, such as sooty mangabeys, African green monkeys and chimpanzees, are generally considered to be resistant to the development of AIDS, despite persistent viral replication. This review focuses on the possible link between the resistance to disease and species-specific diversity in function of human and monkey complement system.
Subject(s)
Complement System Proteins , HIV Infections/immunology , Lentiviruses, Primate/pathogenicity , Simian Acquired Immunodeficiency Syndrome/immunology , Animals , HIV Infections/etiology , Haplorhini , Humans , Immunity, Innate , Simian Acquired Immunodeficiency Syndrome/etiology , Species SpecificityABSTRACT
The scope of this work was to investigate the migration behavior of the currently used protease inhibitors for antiretroviral therapy of people infected with the human immunodeficiency virus and to develop a method for their capillary electrophoretic separation and determination. All of the protease inhibitors (indinavir, saquinavir, nelfinavir, amprenavir, and ritonavir) contain at least one basic amino functional group. As a consequence, they can be separated by capillary zone electrophoresis using acidic buffer electrolytes. A fast electroosmotic flow is established in order to increase separation speed, by adding a cationic electroosmotic flow modifier to the electrolyte. After using conventional serum pretreatment procedures it is possible to separate all five protease inhibitors within less than 5 min. In addition, a non-aqueous CE method is also presented which enables the separation of three protease inhibitor compounds within less than 3 min.
Subject(s)
Electrophoresis, Capillary/methods , HIV Infections/drug therapy , HIV Protease Inhibitors/isolation & purification , HIV Protease Inhibitors/blood , HIV Protease Inhibitors/therapeutic use , Humans , Hydrogen-Ion ConcentrationABSTRACT
Oropharyngeal candidiasis is one of the first and most commonly reported opportunistic infections of untreated AIDS patients. With the introduction of the new antiviral HAART therapy, including HIV protease inhibitors, this mucocutaneous infection is nowadays only rarely observed in treated patients. It was recently shown that HIV protease inhibitors have a direct attenuating effect on Candida albicans secreted aspartic proteinases (Saps), an investigation prompted by the fact that both Sap and HIV protease belong to the superfamily of aspartic proteinases and by the observation that mucocutaneous infections sometimes resolve even in the absence of an immunological improvement of the host. As these Saps are important fungal virulence factors and play a key role in adhesion to human epithelial cells we tried to assess the effect of the HIV protease inhibitors Ritonavir, Indinavir and Saquinavir on fungal adhesion to these cells. The effect on phagocytosis by polymorphonuclear leukocytes was also assessed. Ritonavir was found to be the most potent inhibitor of fungal adhesion. A dose-dependent inhibition of adhesion to epithelial cells was found already at 0.8 microM and was significant at 4 microM or higher, at 500 microM the inhibition was about 55%. Indinavir and Saquinavir inhibited significantly at 4 microM or 20 microM, respectively; at 500 microM the inhibition was 30% or 50%. In contrast, no protease inhibitor was able to modulate phagocytosis of Candida by polymorphonuclear leukocytes. In conclusion, inhibition of Saps by HIV protease inhibitors may directly help to ease the resolution of mucosal candidiasis. In future, derivatives of HIV protease inhibitors, being more specific for the fungal Saps, may form an alternative in the treatment of mucosal candidiasis insensitive to currently available antimycotics.
Subject(s)
Aspartic Acid Endopeptidases/antagonists & inhibitors , Candida albicans/drug effects , HIV Protease Inhibitors/pharmacology , Candida albicans/pathogenicity , Candida albicans/physiology , Cell Adhesion/drug effects , Dose-Response Relationship, Drug , HeLa Cells , Humans , Indinavir/pharmacology , Neutrophils/drug effects , Neutrophils/immunology , Phagocytosis , Ritonavir/pharmacology , Saquinavir/pharmacologyABSTRACT
This review focuses on interactions of HIV with the first-line defence of native immunity, the complement system. In all body compartments tested so far, HIV meets complement. Activation of the complement system results in deposition of C3 fragments on the viral surface, but in contrast to other pathogens, most of HIV is not or is only poorly lysed by membrane attack complexes. To survive complement-mediated lysis, HIV has not only developed resistance mechanisms, but uses opsonisation with complement fragments for its own advantage. Opsonised virions interact with complement receptor-expressing cells, which are either subsequently infected with high efficiency or retain viral particles on their surface, which promotes transmission of virus to other permissive cells. Our knowledge of these mechanisms has increased enormously over the past few years. A complete understanding of these complex interactions of HIV with the complement system opens new perspectives for development of alternative therapeutic strategies.
Subject(s)
Complement C3/immunology , Complement System Proteins/physiology , HIV Infections/etiology , HIV/pathogenicity , AIDS Dementia Complex/immunology , AIDS Dementia Complex/virology , AIDS-Related Opportunistic Infections/microbiology , Anaphylatoxins/physiology , Animals , Antiretroviral Therapy, Highly Active , Brain/immunology , Brain/virology , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/virology , Candida albicans/chemistry , Candida albicans/immunology , Candida albicans/pathogenicity , Candidiasis/etiology , Candidiasis/microbiology , Complement C3/metabolism , Complement Pathway, Classical , Dendritic Cells/immunology , Dendritic Cells/virology , Disease Susceptibility , Germinal Center/immunology , HIV/metabolism , Humans , Macrophages/virology , Molecular Mimicry , Mucous Membrane/immunology , Mucous Membrane/virology , Opsonin Proteins/immunology , Opsonin Proteins/metabolism , Phagocytosis , Protein Binding , Substance Abuse, Intravenous , Trypanosoma/chemistry , Trypanosoma/immunology , Trypanosoma/pathogenicity , Trypanosomiasis/etiology , Trypanosomiasis/parasitology , Viremia/immunology , VirulenceABSTRACT
Complement factor H (fH) is an important regulator of complement activation. It contributes to protection of cells against homologous complement attack. In this study we tested the effect of fH-depletion of normal human serum (NHS) on lysis of antibody-coated sheep and human erythrocytes (EshA and EhuA). In the absence of fH, lysis of sensitised Esh and Ehu was clearly increased. Addition of fH to fH-depleted serum re-established protection of cells against complement similar to that seen with NHS. A fH-derived peptide (pepAred), covering the N-terminal half of SCR 13 in fH, was able to enhance complement-mediated lysis of EhuA significantly. However, the oxidised form of this peptide (pepAox) had no effect. Biotinylated pepAred, but not pepAox, was able to directly bind to cells. Additionally, pepAred competed with direct fH-cell interaction which was observable only after treatment of purified fH with mercaptoethanol. Only pepAred increased the amount of C3 fragments and reduced levels of fH detectable on cells as shown by FACS analysis and radio-immuno assay. Furthermore, fH and factor I (fI)-mediated cleavage of agarose bound C3b into iC3b was decreased in the presence of pepAred. These data indicate that a fH-derived peptide can enhance complement-mediated lysis. We will continue to investigate whether the use of a fH peptide can be exploited for therapeutical purposes.
Subject(s)
Complement Activation , Complement Factor H/immunology , Peptide Fragments/immunology , Amino Acid Sequence , Animals , Cell Line , Complement Factor H/isolation & purification , Consensus Sequence , Erythrocytes/immunology , Hemolysis/immunology , Humans , In Vitro Techniques , Molecular Sequence Data , Peptide Fragments/isolation & purification , Repetitive Sequences, Amino Acid , SheepABSTRACT
Mononuclear phagocytes, which include circulating blood monocytes and differentiated tissue macrophages, are believed to play a central role in the sexual transmission of HIV infection. The ability of HIV to productively infect these cells may be influenced by action of exogenous or host-derived substances at the site of viral entry. Given the potent capacities of inflammatory mediators to stimulate anaphylatoxic and immunomodulatory functions in mucosa, the effects of complement-derived anaphylatoxins on the susceptibility of monocytes and monocyte-derived macrophages (MDM) to HIV-1 infection were examined. In our in vitro system, the susceptibility to infection was up to 40 times increased in MDM that had been exposed to C5a or C5a(desArg), but not to C3a or C3a(desArg), for 2 days before adding of virus. By contrast, the treatment with complement anaphylatoxins did not affect HIV replication in fresh monocytes. Stimulatory effect of C5a and its desArg derivative on HIV infection correlated with the increase of TNF-alpha and IL-6 secretion from MDM. All these functional effects of C5a and C5a(desArg) were reversible by treatment of cells with the mAb that functionally blocks C5aR. Taken together, these results indicate that C5a and C5a(desArg) may increase the susceptibility of MDM to HIV infection through stimulation of TNF-alpha and IL-6 secretion from these cells.
Subject(s)
Adjuvants, Immunologic/physiology , Complement C5a, des-Arginine/physiology , Complement C5a/physiology , HIV-1/immunology , Macrophages/immunology , Macrophages/virology , Membrane Proteins , Monocytes/immunology , Monocytes/virology , Antibodies, Blocking/pharmacology , Antibodies, Monoclonal/pharmacology , Antigens, CD/biosynthesis , Antigens, CD/immunology , Cells, Cultured , Complement C3a/metabolism , Complement C5a/metabolism , Cytokines/metabolism , HIV-1/physiology , Humans , Immunity, Innate , Interleukin-6/metabolism , Leukocytes, Mononuclear/immunology , Leukocytes, Mononuclear/virology , Macrophages/metabolism , Monocytes/metabolism , Receptor, Anaphylatoxin C5a , Receptors, Complement/antagonists & inhibitors , Receptors, Complement/biosynthesis , Receptors, Complement/immunology , Time Factors , Tumor Necrosis Factor-alpha/metabolism , Virus Replication/immunologyABSTRACT
Since the brain is separated from the blood immune system by a tight barrier, the brain-resident complement system may represent a central player in the immune defense of this compartment against human immunodeficiency virus (HIV). Chronic complement activation, however, may participate in HIV-associated neurodegeneration. Since the level of complement factors in the cerebrospinal fluid is known to be elevated in AIDS-associated neurological disorders, we evaluated the effect of HIV type 1 (HIV-1) on the complement synthesis of brain astrocytes. Incubation of different astrocytic cell lines and primary astrocytes with HIV-1 induced a marked upregulation of the expression of the complement factors C2 and C3. The synthesis of other secreted or membrane-bound complement proteins was not found to be altered. The enhancement of C3 production was measured both on the mRNA level and as secreted protein in the culture supernatants. HIV-1 laboratory strains as well as primary isolates were capable of inducing C3 production with varied effectiveness. The usage of viral coreceptors by HIV-1 was proved to be a prerequisite for the upregulation of C3 synthesis, which was modulated by the simultaneous addition of cytokines. The C3 protein which is secreted after incubation of the cells with HIV was shown to be biologically active as it can participate in the complement cascade.
Subject(s)
Astrocytes/immunology , Astrocytes/virology , Complement C2/biosynthesis , Complement C3/biosynthesis , HIV-1/immunology , Antibodies/immunology , Complement Activation , Complement C3/immunology , Cytokines/pharmacology , HIV Infections/immunology , HIV Infections/virology , HIV-1/metabolism , Humans , RNA, Messenger/genetics , RNA, Messenger/metabolism , Receptors, CCR5/immunology , Receptors, CCR5/metabolism , Receptors, CXCR4/immunology , Receptors, CXCR4/metabolism , Tumor Cells, Cultured , Up-RegulationABSTRACT
Tat, the human immunodeficiency virus type 1 (HIV-1) transactivating protein, binds through its RGD-motif to human integrin receptors. Candida albicans, the commonest cause of mucosal candidiasis in subjects infected with HIV-1, also possesses RGD-binding capacity. The present study reveals that Tat binds to C. albicans but not to C. tropicalis. Tat binding was markedly reduced by laminin and to a lesser extent by a complement C3 peptide containing the RGD motif, but not by a control peptide. The outgrowth of C. albicans was accelerated following binding of Tat, but phagocytosis of opsonized C. albicans was also increased after Tat binding. Thus, Tat binding promotes fungal virulence by inducing hyphae but may also reduce it by augmenting phagocytosis. The net effect of Tat in vivo is difficult to judge but in view of the many disease-promoting effects of Tat we propose that accelerating the formation of hyphae dominates over the augmentation of phagocytosis.
Subject(s)
Candida albicans/metabolism , DNA-Binding Proteins/metabolism , Phagocytosis/drug effects , Proteasome Endopeptidase Complex , ATPases Associated with Diverse Cellular Activities , Binding, Competitive , Candida/metabolism , Candida albicans/pathogenicity , Cell Culture Techniques , Complement C3/pharmacology , DNA-Binding Proteins/pharmacology , Dose-Response Relationship, Drug , Female , Humans , Laminin/pharmacology , Ligands , Monocytes/drug effects , Monocytes/immunology , VirulenceABSTRACT
Drugs which inhibit different stages of the HIV infection process, such as cell entry through CD4 and chemokine receptors, production of double stranded DNA from the HIV genome and maturation of newly produced viruses, are now proposed for AIDS therapy. None of these treatments, however, solve the problem of complete HIV eradication and the frequent appearance of mutants displaying drug resistance. We have recently detailed a strategy describing how HIV protects itself from the human complement and propose that interference of this resistance could be a possible target for therapy.
Subject(s)
AIDS Vaccines/pharmacology , Anti-HIV Agents/pharmacology , Complement System Proteins/drug effects , Complement System Proteins/physiology , HIV Infections/drug therapy , HIV Infections/immunology , AIDS Vaccines/therapeutic use , Animals , Anti-HIV Agents/therapeutic use , Antibodies, Monoclonal , Complement C3b , Complement Factor H/physiology , HIV/drug effects , HIV/physiology , HIV Envelope Protein gp120 , HIV Envelope Protein gp41 , Humans , Peptide FragmentsABSTRACT
In vivo, human immunodeficiency virus type 1 (HIV-1) is opsonized with complement fragments and virus-specific antibodies (Ab). Thus, HIV is able to interact with complement receptor (CR) - and Fc receptor (FcR) - positive cells such as B cells, follicular dendritic cells or macrophages. In this study we demonstrate that the interaction between B cells and HIV has an impact on autologous primary T cell infection in vitro. We confirmed the presence of complement-fragments and virus-specific Ab on serum-treated HIV using a virus-capture assay. In experiments with CR2-specific Ab we showed that the virus/B cell interaction was mainly dependent on CR2. In infection experiments immobilisation of HIV on stimulated tonsil B cells greatly enhanced the infection of interleukin (IL)-2-activated autologous tonsil T cells. Surprisingly, enhancement of T cell infection by B cell-HIV complexes was observed even in the absence of mitogenic stimuli such as PMA and was independent of the addition of exogenous IL-2. Taken together, these results indicate that primary B cells are able to efficiently transmit opsonised HIV to autologous primary T cells and induce a massive enhancement of infection. These in vitro experiments mimic the in vivo situation in the lymphoid tissue and suggest an alternative mechanism for the infection of primary T cells.
Subject(s)
B-Lymphocytes/virology , Complement C3/immunology , HIV-1/immunology , T-Lymphocytes/virology , B-Lymphocytes/immunology , Cells, Cultured , Coculture Techniques , Complement C1q/immunology , HIV Antibodies/immunology , Humans , Palatine Tonsil/cytology , T-Lymphocytes/immunology , Tumor Cells, CulturedABSTRACT
After the transition from the acute to the chronic phase of human immunodeficiency virus (HIV) infection, complement mediates long-term storage of virions in germinal centers (GC) of lymphoid tissue. The contribution of particular complement receptors (CRs) to virus trapping in GC was studied on tonsillar specimens from HIV-infected individuals. CR2 (CD21) was identified as the main binding site for HIV in GC. Monoclonal antibodies (MAb) blocking the CR2-C3d interaction were shown to detach 62 to 77% of HIV type 1 from tonsillar cells of an individual in the presymptomatic stage. Although they did so at a lower efficiency, these antibodies were able to remove HIV from tonsillar cells of patients under highly active antiretroviral therapy, suggesting that the C3d-CR2 interaction remains a primary entrapment mechanism in treated patients as well. In contrast, removal of HIV was not observed with MAb blocking CR1 or CR3. Thus, targeting CR2 may facilitate new approaches toward a reduction of residual virus in GC.
Subject(s)
Germinal Center/virology , HIV-1/immunology , Palatine Tonsil/virology , Receptors, Complement 3d/metabolism , Adult , Animals , Antibodies, Monoclonal/metabolism , Binding, Competitive , Complement C3d/immunology , Complement C3d/metabolism , Enzyme-Linked Immunosorbent Assay , Germinal Center/immunology , HIV-1/metabolism , Humans , Immunohistochemistry , Mice , Palatine Tonsil/immunology , RNA, Viral/analysis , Receptors, Complement 3d/immunologyABSTRACT
In the present article we review selected aspects of the complement system as a major determinant of innate immunity. Besides a detailed description of the components of the complement system, its mode of action, cellular receptors and regulatory control mechanisms, we have focused on the role of the complement system in mutual defence strategies of invading viral pathogens and the host. Since a detrimental activation of the complement cascade is a critical element of several pathological conditions in diverse organs, we summarise the role of a deteriorated complement system in dermatology, nephrology, neurology and xenotransplantation.