Academic literature on the topic 'IgG2 anti-gp41'

ABSTRACT We studied the effect of entry inhibitors on 58 virus isolates derived during acute and chronic infection to validate these inhibitors in vitro and to probe whether viruses at early and chronic disease stages exhibit general differences in the interaction with entry receptors. We included members of all types of inhibitors currently identified: (i) agents that block gp120 binding to CD4 (CD4-IgG2 and monoclonal antibody [MAb] IgG1b12), (ii) compounds that block the interaction with CCR5 (the chemokine RANTES/CCL5, the small-molecule inhibitor AD101, and the anti-CCR5 antibody PRO 140), (iii) the fusion inhibitor enfuvirtide (T-20), and (iv) neutralizing antibodies directed against gp120 (MAb 2G12) and gp41 (MAbs 2F5 and 4E10). No differences between viruses from acute and chronic infections in the susceptibility to inhibitors targeting the CD4 binding site, CCR5, or fusion or to MAb 2G12 were apparent, rendering treatment with entry inhibitors feasible across disease stages. The notable exceptions were antibodies 2F5 and 4E10, which were more potent in inhibiting viruses from acute infection (P = 0.0088 and 0.0005, respectively), although epitopes of these MAbs were equally well preserved in both groups. Activities of these MAbs correlated significantly with each other, suggesting that common features of the viral envelope modulate their potencies.

We have explored the effect of antiretroviral drugs on the antiviral immune response in human immunodeficiency virus-1 (HIV-1)—infected patients by using an enzymatic immunosensor that detects epitope-modifying anti-gp41 antibodies. By this molecular sensing approach, we have identified an irreversible impact of drug administration on the functionality of IgG4 and IgM specific antibodies regarding the structural modification promoted on their target epitope. During the antiretroviral therapy, the prevalent induced fit promoted by IgM on the epitope was lost at the expense of that promoted by IgG4, suggesting alternative-ness in the neutralization potency of these antibody subpopulations. Because the particular drug composition of the antiretroviral treatment did not affect such immune shift, the obtained data strongly suggest that the drop in the viral load and the consequent lost of antigenemia are responsible for the functional adaptation observed in the humoral response. ( Journal of Biomolecular Screening 2008:817-821)

Objective: Novel vaccination approaches are required to control human immunodeficiency virus (HIV) infections. The membrane proximal external region (MPER) of Env gp41 subunit and the V3/glycans of Env gp120 subunit were known as potential antigenic targets for anti-HIV-1 vaccines. In this study, we prepared the modified dendritic cells (DCs) and mesenchymal stem cells (MSCs) with HIV-1 MPER-V3 gene using mechanical and chemical approaches. Methods: At first, MPER-V3 fusion DNA delivery was optimized in dendritic cells (DCs) and mesenchymal stem cells (MSCs) using three mechanical (i.e., uniaxial cyclic stretch, equiaxial cyclic stretch and shear stress bioreactors), and two chemical (i.e., TurboFect or Lipofectamine) methods. Next, the modified DCs and MSCs with MPER-V3 antigen were compared to induce immune responses in vivo. Results: Our data showed that the combination of equiaxial cyclic stretch loading and lipofectamine twice with 48 h intervals increased the efficiency of transfection about 60.21 ± 1.05 % and 65.06 ± 0.09 % for MSCs and DCs, respectively. Moreover, DCs and MSCs transfected with MPER-V3 DNA in heterologous DC or MSC prime/ peptide boost immunizations induced high levels of IgG2a, IgG2b, IFN-γ and IL-10 directed toward Th1 responses as well as an increased level of Granzyme B. Indeed, the modified MSCs and DCs with MPER-V3 DNA could significantly enhance the MPER/V3-specific T-cell responses compared to MPER/V3 peptide immunization. Conclusion: These findings showed that the modified MSC-based immunization could elicit effective immune responses against HIV antigen similar to the modified DC-based immunization.

ABSTRACT A window of opportunity for immune responses to extinguish human immunodeficiency virus type 1 (HIV-1) exists from the moment of transmission through establishment of the latent pool of HIV-1-infected cells. A critical time to study the initial immune responses to the transmitted/founder virus is the eclipse phase of HIV-1 infection (time from transmission to the first appearance of plasma virus), but, to date, this period has been logistically difficult to analyze. To probe B-cell responses immediately following HIV-1 transmission, we have determined envelope-specific antibody responses to autologous and consensus Envs in plasma donors from the United States for whom frequent plasma samples were available at time points immediately before, during, and after HIV-1 plasma viral load (VL) ramp-up in acute infection, and we have modeled the antibody effect on the kinetics of plasma viremia. The first detectable B-cell response was in the form of immune complexes 8 days after plasma virus detection, whereas the first free plasma anti-HIV-1 antibody was to gp41 and appeared 13 days after the appearance of plasma virus. In contrast, envelope gp120-specific antibodies were delayed an additional 14 days. Mathematical modeling of the earliest viral dynamics was performed to determine the impact of antibody on HIV replication in vivo as assessed by plasma VL. Including the initial anti-gp41 immunoglobulin G (IgG), IgM, or both responses in the model did not significantly impact the early dynamics of plasma VL. These results demonstrate that the first IgM and IgG antibodies induced by transmitted HIV-1 are capable of binding virions but have little impact on acute-phase viremia at the timing and magnitude that they occur in natural infection.

ABSTRACT The characteristics of antibody-dependent cellular cytotoxicity (ADCC) directed by a panel of human and chimpanzee antienvelope (anti-Env) monoclonal antibodies (MAbs) of different epitope specificities were studied; this was accomplished by using target cells expressing human immunodeficiency virus type 1 (HIV-1) Envs of either primary or laboratory-adapted strains. Human MAbs of similar apparent affinities (1 × 109 to 2 × 109 liters/mol) against either a “cluster II”-overlapping epitope of gp41 or against the CD4 binding site, V3 loop, or C5 domain of gp120 directed substantial and comparable levels of specific lysis against targets infected with laboratory-adapted strains of HIV-1. As expected, those MAbs specific for relatively conserved regions of Env generally exhibited ADCC activity against a broader range of HIV-1 strains than those directed against variable epitopes. Significant ADCC activities of selected MAbs against primary isolate Env-expressing cells were demonstrated. In addition, a new ADCC epitope in the V2 domain of gp120 was defined. CD56+ cells were demonstrated to be the effector cells in these studies by fluorescence-activated cell sorting followed by ADCC assays. Notably, all anti-Env MAbs tested in this study, including MAbs directed against each of the known neutralization epitope clusters in gp120, directed significant levels of ADCC against targets expressing Env of one or more HIV-1 strains. These results imply that many, if not most, HIV-1-neutralizing human Abs of high affinity (≥3 × 108 liters/mol in these studies) and of the immunoglobulin G1 (IgG1) subclass (i.e., the predominate IgG subclass) are capable of directing ADCC. Since neutralizing Abs have been associated with long-term survival following HIV-1 infection, this suggests that ADCC activity may be beneficial in vivo.

ABSTRACT In light of the weak or absent neutralizing activity mediated by anti-V2 monoclonal antibodies (MAbs), we tested whether they can mediate Ab-dependent cellular phagocytosis (ADCP), which is an important element of anti-HIV-1 immunity. We tested six anti-V2 MAbs and compared them with 21 MAbs specific for V3, the CD4-binding site (CD4bs), and gp41 derived from chronically HIV-1-infected individuals and produced by hybridoma cells. ADCP activity was measured by flow cytometry using uptake by THP-1 monocytic cells of fluorescent beads coated with gp120, gp41, BG505 SOSIP.664, or BG505 DS-SOSIP.664 complexed with MAbs. The measurement of ADCP activity by the area under the curve showed significantly higher activity of anti-gp41 MAbs than of the members of the three other groups of MAbs tested using beads coated with monomeric gp41 or gp120; anti-V2 MAbs were dominant compared to anti-V3 and anti-CD4bs MAbs against clade C gp120ZM109. ADCP activity mediated by V2 and V3 MAbs was positive against stabilized DS-SOSIP.664 trimer but negligible against SOSIP.664 targets, suggesting that a closed envelope conformation better exposes the variable loops. Two IgG3 MAbs against the V2 and V3 regions displayed dominant ADCP activity compared to a panel of IgG1 MAbs. This superior ADCP activity was confirmed when two of three recombinant IgG3 anti-V2 MAbs were compared to their IgG1 counterparts. The study demonstrated dominant ADCP activity of anti-gp41 against monomers but not trimers, with some higher activity of anti-V2 MAbs than of anti-V3 and anti-CD4bs MAbs. The ability to mediate ADCP suggests a mechanism by which anti-HIV-1 envelope Abs can contribute to protective efficacy. IMPORTANCE Anti-V2 antibodies (Abs) correlated with reduced risk of HIV-1 infection in recipients of the RV144 vaccine, suggesting that they play a protective role, but a mechanism providing such protection remains to be determined. The rare and weak neutralizing activities of anti-V2 MAbs prompted us to study Fc-mediated activities. We compared anti-V2 MAbs with other MAbs specific for V3, CD4bs, and gp41 for Ab-dependent cellular phagocytosis (ADCP) activity, implicated in protective immunity. The anti-V2 MAbs displayed stronger activity than other anti-gp120 MAbs in screening against one of two gp120s and against DS-SOSIP, which mimics the native trimer. The activity of anti-gp41 MAbs was superior in targeting monomeric gp41 but was comparable to that seen against trimers, which may not adequately expose gp41 epitopes. While anti-envelope MAbs in general mediated ADCP activity, anti-V2 MAbs displayed some dominance compared to other MAbs. Our demonstration that anti-V2 MAbs mediate ADCP activity suggests a functional mechanism for their contribution to protective efficacy.

« Etude des paramètres immunologiques et immunopathologiques des patients infectés par le virus de l’immunodéficience humaine et asymptomatiques à long terme » Comme nous avons pu le voir dans ce travail de thèse, les sujets infectés par le Virus de l’Immunodéficience Humaine (VIH) et asymptomatiques à long terme (ALT) montrent des caractéristiques immunitaires remarquables permettant d’analyser de façon fine l’équilibre entre réplication virale contenue, réponses immunes et conséquences immunopathologiques de ces réponses et/ou de la réplication virale. Les réponses immunes T en particulier CD4 semblent jouent un rôle clé dans le maintien du statut asymptomatique à long terme mais il n’est pas possible de définir précisément si l’intensité exceptionnelle de ces réponses est cause ou conséquence du contrôle du VIH. Nos résultats préliminaires sur l’étude de l’expression des récepteurs aux cytokines IL-15 et IL-7 suggèrent que les cellules anti-VIH expriment des pourcentages plus élevés d’expression de la chaîne  du récepteur à l’IL-15 que les cellules CD8 totales. Cette expression est associée à une activation intense et un état de différenciation plus avancé contrairement à l’expression de chaîne  du récepteur à l’IL-7. Par ailleurs, le développement d’une réponse autoimmune en particulier la production d’autoanticorps anticardiolipines au cours de l’infection par le VIH apparaît comme lié aux paramètres de réplication virale, à l’existence d’anticorps neutralisants dirigés contre la gp41 et/ou la gp120 et à l’activation T CD4. De même, il n’est pas encore possible de définir les mécanismes de causalité ni la pathogénicité de ces manifestations Les progrès dans les connaissances et la compréhension des facteurs participant à l’absence de progression de l’infection par le VIH sont primordiaux et ouvrent la possibilité, en l’absence de guérison et de vaccin efficace, de pouvoir conférer un jour ce statut à l’ensemble des patients infectés par le VIH-1.

Le SIDA est une infection transmise essentiellement au niveau des muqueuses génitales. Pour empêcher la transmission du virus de l'immunodéficience humaine (VIH-1), il faudrait dresser des barrières efficaces susceptibles de bloquer l'infection dès l'entrée du VIH-1 dans les muqueuses, avant l'établissement de réservoirs muqueux. Les IgA sont les principaux effecteurs immunitaires protecteurs des muqueuses génitales et participent à la protection contre la transmission muqueuse du virus. En effet, chez des femmes hautement exposées au VIH-1 qui restent séronégatives malgré des rapports sexuels non protégés avec des partenaires infectés par le VIH-1 (ESN), les IgA muqueux spécifiques de l'enveloppe virale gp41 avec des activités antivirales cross-clade puissantes sont un corrélat de protection majeur. Mais les muqueuses génitales sont aussi protégées par des IgG dont l'origine et le rôle sont actuellement réévalués. Dans ce travail, nous avons analysé l'influence de l'isotype, A ou G, sur la spécificité épitopique, les fonctions antivirales des anticorps protecteurs de sujets ESN et évalué de nouvelles fonctions antivirales médiées par le fragment constant des IgA. Pour ces études, nous avons d'abord utilisé 2 Fab IgA protecteurs issus d'une banque d'IgA muqueux provenant de femmes ESN spécifiques de régions conservées de gp41 de l'enveloppe du VIH, caractérisés au laboratoire. Ces Fab IgA (FabA) ont d'abord été transformés en Fab IgG (FabG) correspondants par génie génétique puis comparés au niveau immunochimique et fonctionnel. Ces couples FabA/G portent les mêmes paratopes mais diffèrent par leur partie CH1 (alpha ou gamma) qui dicte l'isotype. Nous avons montré que l'isotype et notamment le domaine CH1 de l'anticorps influence : i) l'affinité des Fabs pour leurs antigènes de clades A, B et C par la résonance plasmonique de surface et ELISA : les FabA ont une affinité &gt;50x supérieure aux FabG correspondants ; ii) les fonctions antivirales : les FabA neutralisent plus efficacement l'infection de LTCD4 et le transfert du virus de cellules de Langerhans aux LTCD4 que les FabG correspondants. Puis, en prenant comme modèle expérimental l'anticorps 2F5 sous forme IgA, nous avons caractérisé une nouvelle propriété antivirale pour les IgA médiée par leur domaine Fc et montré que cet isotype est aussi capable d'induire la lyse de cellules infectées par le VIH-1 par Antibody dependent cell cytotoxicity, ADCC. Cette ADCC est médiée par des cellules effectrices (monocytes) de façon FcR alpha-dépendante. De plus, IgA et IgG spécifiques de gp41 agissent en synergie pour augmenter l'ADCC des cellules infectées par le VIH. L'ensemble de ces résultats montre que l'isotype (le domaine CH1) a une influence sur la reconnaissance et l'affinité pour l'antigène, mais aussi sur la qualité de la réponse immunitaire secondaire (fonctions antivirales). Finalement nous avons caractérisé les épitopes conformationnels de ces FabA/FabG sur des gp41 des différentes clades, A, B et C, chacune sous conformation pré et post fusion en utilisant une stratégie de biopanning couplée à une analyse in silico. Nous avons ainsi défini les épitopes conformationnels cross-clade de ces anticorps protecteurs de sujets ESN. Ils pourront servir d'immunogènes dans une stratégie vaccinale visant à reproduire la réponse IgA protectrice des ESN. Au cours de cette étude, nous avons mis en œuvre une stratégie de Reverse Vaccinology 2.0 pour caractériser, à partir d'anticorps de sujets ESN protégés de l'infection par le VIH, des épitopes conformationnels spécifiques de gp41 qui pourraient servir d'immunogènes dans une stratégie vaccinale contre le VIH. Cette approche vaccinale muqueuse pourrait conduire à diminuer les cas de nouvelles infections sexuelles par le VIH chez les femmes (les plus touchées par l'infection au niveau mondiale) mais aussi chez les hommes, ce qui reste un énorme challenge de santé publique<br>AIDS is an infection transmitted mainly in the genital mucosa. It is at this level that an effective barrier should be developed to block infection from the initial entry of HIV-1 in the genitals, before establishment of mucosal reservoirs. IgA is the main protective antibody at the genital mucosa and has been suggested to be protective in vivo against HIV-1. Hence, mucosal gp41-specific IgA with strong cross-clade antiviral activity are a major protective correlate in Highly HIV- Exposed individuals that remain SeroNegative (ESN) despite unprotected sexual intercourse with infected partners. However, genital mucosa are also protected by IgG whose origin and role are currently reevaluated. In this work, we have analyzed the influence of the antibody isotype, IgA or IgG, on the epitope specificity, antiviral functions of HIV-1 protective antibodies and evaluated new antiviral functions mediated by the constant IgA regions. For this purpose we have used a library of protective Fab IgA derived from ESN women that are specific for conserved regions of the HIV-1 envelope gp41 subunit, already characterized in the laboratory (Tudor et al., Mucosal Immunol, 2009). By genetic engineering, we have first transformed two of these Fab IgA (FabA) into their corresponding Fab IgG (FabG), having the same paratopes but differing from each other by their CH1 domain (alpha or gamma). These two FabA/FabG couples were then analyzed comparatively for their epitope specificity and functional activities. We have shown that the isotype and particularly the CH1 domain influences (i) the affinity of Fabs for their antigens (gp41 and P1 of clades A, B and C) using surface plasmon resonance and ELISA : FabA have a 50- to 100-fold higher affinity than corresponding FabG ; (ii) antiviral functions: FabA more effectively neutralize CD4+ T-cells infection and transfer of HIV-1 from Langerhans cells to CD4+ T-cells than their corresponding FabG. In a second step, taking as experimental model the neutralizing HIV-1 antibody 2F5 as IgA, we demonstrated that IgA specific for gp41 were able to lyse HIV-1 infected cells in a process mediated by their Fc alpha domain, namely antibody mediated cell cytoxicity (ADCC), a function usually attributed to IgG. Furthermore, anti-gp41 IgA and IgG work in synergy to increase HIV-1-infected cell lysis. Altogether, the results show the isotype (the CH1 domain) has an influence on the recognition and affinity for the antigen, but also on the quality of the secondary immune response (antiviral functions). Finally, we characterized epitopes specific from the two FabA/FabG couples using biopanning followed by in silico analysis. Cross clade 3-dimensional epitopes were mapped on gp41 from Clade A, B and C, each in pre- or post-fusion conformation. These analyses allowed to define cross clade 3-dimensional epitopes targeted by these protective antibodies derived from ESN subjects. These epitopes could serve as immunogen in a vaccine strategy aiming at recapitulating the protective ESN IgA response. Altogether, we have used the strategy of Reverse Vaccinology 2.0 to characterize novel immunogens based on 3D-epitopes targeted by mucosal antibodies from individuals resisting HIV infection. These results should be taken into account in the design of an effective vaccine against the active clades of HIV-1 in the world (A, B and C). Such mucosal vaccine approach is necessary to decrease the number of new HIV infections among women (the most affected) but also in men, which remains a huge public health challenge