CD4 mimetics sensitize HIV-1-infected cells to ADCC Richard, Jonathan; Veillette, Maxime; Brassard, Nathalie ...
Proceedings of the National Academy of Sciences - PNAS,
05/2015, Letnik:
112, Številka:
20
Journal Article
Recenzirano
Odprti dostop
Significance The prevention of HIV-1 transmission and progression likely requires approaches that can specifically eliminate HIV-1-infected cells. Rationally designed CD4-mimetic compounds (CD4mc) ...have been shown to efficiently inhibit viral entry and sensitize HIV-1 particles to neutralization by otherwise nonneutralizing CD4-induced antibodies. Here we found that CD4mc can also sensitize HIV-1-infected cells to antibody-dependent cell-mediated cytotoxicity (ADCC). Indeed, CD4mc induced the CD4-bound conformation of HIV-1 envelope glycoproteins, exposing CD4-induced epitopes recognized by easy-to-elicit antibodies present in sera, cervicovaginal lavages, and breast milk from HIV-1-infected individuals. Importantly, we provide evidence that CD4mc can efficiently sensitize primary CD4 T cells from HIV-1-infected individuals to ADCC mediated by autologous sera and effector cells. Therefore, CD4mc might represent an attractive approach to prevent and control HIV-1 infection.
HIV-1-infected cells presenting envelope glycoproteins (Env) in the CD4-bound conformation on their surface are preferentially targeted by antibody-dependent cell-mediated cytotoxicity (ADCC). HIV-1 has evolved a sophisticated mechanism to avoid exposure of ADCC-mediating Env epitopes by down-regulating CD4 and by limiting the overall amount of Env at the cell surface. Here we report that small-molecule CD4-mimetic compounds induce the CD4-bound conformation of Env, and thereby sensitize cells infected with primary HIV-1 isolates to ADCC mediated by antibodies present in sera, cervicovaginal lavages, and breast milk from HIV-1-infected individuals. Importantly, we identified one CD4 mimetic with the capacity to sensitize endogenously infected ex vivo-amplified primary CD4 T cells to ADCC killing mediated by autologous sera and effector cells. Thus, CD4 mimetics hold the promise of therapeutic utility in preventing and controlling HIV-1 infection.
An efficient and stereospecific Pd-catalyzed protocol for the C–H arylation of pyroglutamic acid derivatives that uses 8-aminoquinoline as a directing group is described. The reaction was shown to ...proceed efficiently with a variety of aryl and heteroaryl iodides bearing different functional groups, giving C3-arylated cis products in good to high yields. Removal of the 8-aminoquinoline unit from these C–H arylation products enables access to synthetically useful cis and trans pyroglutamic acid-based building blocks.
A unified synthetic strategy to the Cryptocarya family of natural products has been achieved employing four-component fragment unions in a “single flask” exploiting Anion Relay Chemistry (ARC). ...Functionalization of the ARC adducts permits rapid construction of five polyhydroxylated di- and tetrahydropyrone natural products of the Cryptocarya class (1–5), in a total of 7–9 steps from commercially available materials.
Human immunodeficiency virus-1 (HIV-1), the causative agent of AIDS, impacts millions of people. Entry into target cells is mediated by the HIV-1 envelope (Env) glycoprotein interacting with host ...receptor CD4, which triggers conformational changes allowing binding to a coreceptor and subsequent membrane fusion. Small molecule or peptide CD4-mimetic drugs mimic CD4's Phe43 interaction with Env by inserting into the conserved Phe43 pocket on Env subunit gp120. Here, we present single-particle cryo-EM structures of CD4-mimetics BNM-III-170 and M48U1 bound to a BG505 native-like Env trimer plus the CD4-induced antibody 17b at 3.7 Å and 3.9 Å resolution, respectively. CD4-mimetic-bound BG505 exhibits canonical CD4-induced conformational changes including trimer opening, formation of the 4-stranded gp120 bridging sheet, displacement of the V1V2 loop, and formation of a compact and elongated gp41 HR1C helical bundle. We conclude that CD4-induced structural changes on both gp120 and gp41 Env subunits are induced by binding to the gp120 Phe43 pocket.
The inhibition of Plasmodium cytosolic phenylalanine tRNA-synthetase (cFRS) by a novel series of bicyclic azetidines has shown the potential to prevent malaria transmission, provide prophylaxis, and ...offer single-dose cure in animal models of malaria. To date, however, the molecular basis of Plasmodium cFRS inhibition by bicyclic azetidines has remained unknown. Here, we present structural and biochemical evidence that bicyclic azetidines are competitive inhibitors of L-Phe, one of three substrates required for the cFRS-catalyzed aminoacylation reaction that underpins protein synthesis in the parasite. Critically, our co-crystal structure of a PvcFRS-BRD1389 complex shows that the bicyclic azetidine ligand binds to two distinct sub-sites within the PvcFRS catalytic site. The ligand occupies the L-Phe site along with an auxiliary cavity and traverses past the ATP binding site. Given that BRD1389 recognition residues are conserved amongst apicomplexan FRSs, this work lays a structural framework for the development of drugs against both Plasmodium and related apicomplexans.
Primary human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimers (gp120/gp41)
typically exist in a metastable closed conformation (state 1). Binding the CD4 receptor triggers Env to ...undergo extensive conformational changes to mediate virus entry. We identified specific gp120 residues that restrain Env in state 1. Alteration of these restraining residues destabilized state 1, allowing Env to populate a functional conformation (state 2) intermediate between state 1 and the full CD4-bound state (state 3). Increased state 2 occupancy was associated with lower energy barriers between the states. State 2 was an obligate intermediate for all transitions between state 1 and state 3. State 2-enriched Envs required lower CD4 concentrations to trigger virus entry and more efficiently infected cells expressing low levels of CD4. These Envs were resistant to several broadly neutralizing antibodies and small-molecule inhibitors. Thus, state 2 is an Env conformation on the virus entry pathway; sampling state 2 increases the adaptability of HIV-1 to different host cell receptor levels and immune environments. Our results provide new insights into the conformational regulation of HIV-1 entry.
The envelope glycoproteins (Env) of HIV-1 mediate virus entry and are the sole targets of neutralizing antibodies. Understanding the way that Env promotes HIV-1 entry can expedite drug and vaccine development. By destabilizing Env, we found that it assumes an intermediate state that is functional and obligate for transitions to entry-competent conformations. Increased sampling of this state enhances the ability of HIV-1 to infect cells that express low levels of the CD4 receptor and allows the virus to evade neutralizing antibodies and small-molecule inhibitors. These findings provide new mechanistic insights into the function and inhibition of HIV-1 Env and will contribute to ongoing therapeutic and prevention efforts to combat HIV-1.
Human immunodeficiency virus type 1 (HIV-1) entry into cells is mediated by the viral envelope glycoproteins (Env), a trimer of three gp120 exterior glycoproteins, and three gp41 transmembrane ...glycoproteins. The metastable Env is triggered to undergo entry-related conformational changes when gp120 binds sequentially to the receptors, CD4 and CCR5, on the target cell. Small-molecule CD4-mimetic compounds (CD4mc) bind gp120 and act as competitive inhibitors of gp120-CD4 engagement. Some CD4mc have been shown to trigger Env prematurely, initially activating Env function, followed by rapid and irreversible inactivation. Here, we study CD4mc with a wide range of anti-HIV-1 potencies and demonstrate that all tested CD4mc are capable of activating as well as inactivating Env function. Biphasic dose-response curves indicated that the occupancy of the protomers in the Env trimer governs viral activation versus inactivation. One CD4mc bound per Env trimer activated HIV-1 infection. Envs with two CD4mc bound were activated for infection of CD4-negative, CCR5-positive cells, but the infection of CD4-positive, CCR5-positive cells was inhibited. Virus was inactivated when all three Env protomers were occupied by the CD4mc, and gp120 shedding from the Env trimer was increased in the presence of some CD4mc. Env reactivity and the on rates of CD4mc binding to the Env trimer were found to be important determinants of the potency of activation and entry inhibition. Cross-sensitization of Env protomers that do not bind the CD4mc to neutralization by an anti-V3 antibody was not evident. These insights into the mechanism of antiviral activity of CD4mc should assist efforts to optimize their potency and utility.
The trimeric envelope glycoproteins of human immunodeficiency virus type 1 (HIV-1) mediate virus entry into host cells. Binding to the host cell receptors, CD4 and CCR5, triggers changes in the conformation of the HIV-1 envelope glycoprotein trimer important for virus entry. Small-molecule CD4-mimetic compounds inhibit HIV-1 infection by multiple mechanisms: (i) direct blockade of the interaction between the gp120 exterior envelope glycoprotein and CD4; (ii) premature triggering of conformational changes in the envelope glycoproteins, leading to irreversible inactivation; and (iii) exposure of cryptic epitopes to antibodies, allowing virus neutralization. The consequences of the binding of the CD4-mimetic compound to the HIV-1 envelope glycoproteins depends upon how many of the three subunits of the trimer are bound and upon the propensity of the envelope glycoproteins to undergo conformational changes. Understanding the mechanistic factors that influence the activity of CD4-mimetic compounds can help to improve their potency and coverage of diverse HIV-1 strains.
Lifelong antiretroviral therapy (ART) for HIV-1 does not diminish the established latent reservoir. A possible cure approach is to reactivate the quiescent genome from latency and utilize immune ...responses to eliminate cells harboring reactivated HIV-1. It is not known whether antibodies within HIV-1-infected individuals can recognize and eliminate cells reactivated from latency through antibody-dependent cellular cytotoxicity (ADCC). We found that reactivation of HIV-1 expression in the latently infected ACH-2 cell line elicited antibody-mediated NK cell activation but did not result in antibody-mediated killing. The lack of CD4 expression on these HIV-1 envelope (Env)-expressing cells likely resulted in poor recognition of CD4-induced antibody epitopes on Env. To examine this further, cultured primary CD4(+) T cells from HIV-1(+) subjects were used as targets for ADCC. These ex vivo-expanded primary cells were modestly susceptible to ADCC mediated by autologous or heterologous HIV-1(+) serum antibodies. Importantly, ADCC mediated against these primary cells could be enhanced following incubation with a CD4-mimetic compound (JP-III-48) that exposes CD4-induced antibody epitopes on Env. Our studies suggest that with sufficient reactivation and expression of appropriate Env epitopes, primary HIV-1-infected cells can be targets for ADCC mediated by autologous serum antibodies and innate effector cells. The results of this study suggest that further investigation into the potential of ADCC to eliminate reactivated latently infected cells is warranted.
An HIV-1 cure remains elusive due to the persistence of long-lived latently infected cells. An HIV-1 cure strategy, termed "shock and kill," aims to reactivate HIV-1 expression in latently infected cells and subsequently eliminate the reactivated cells through immune-mediated killing. While recent research efforts have focused on reversing HIV-1 latency, it remains unclear whether preexisting immune responses within HIV-1(+) individuals can efficiently eliminate the reactivated cells. HIV-1-specific antibodies can potentially eliminate cells reactivated from latency via Fc effector functions by recruiting innate immune cells. Our study highlights the potential role that antibody-dependent cellular cytotoxicity might play in antilatency cure approaches.
Toxoplasma gondii commonly infects humans and while most infections are controlled by the immune response, currently approved drugs are not capable of clearing chronic infection in humans. Hence, ...approximately one third of the world's human population is at risk of reactivation, potentially leading to severe sequelae. To identify new candidates for treating chronic infection, we investigated a series of compounds derived from diversity-oriented synthesis. Bicyclic azetidines are potent low nanomolar inhibitors of phenylalanine tRNA synthetase (PheRS) in T. gondii, with excellent selectivity. Biochemical and genetic studies validate PheRS as the primary target of bicyclic azetidines in T. gondii, providing a structural basis for rational design of improved analogs. Favorable pharmacokinetic properties of a lead compound provide excellent protection from acute infection and partial protection from chronic infection in an immunocompromised mouse model of toxoplasmosis. Collectively, PheRS inhibitors of the bicyclic azetidine series offer promise for treatment of chronic toxoplasmosis.
The envelope glycoprotein (Env) trimer ((gp120/gp41)
) mediates human immunodeficiency virus (HIV-1) entry into cells. The "closed," antibody-resistant Env trimer is driven to more open conformations ...by binding the host receptor, CD4. Broadly neutralizing antibodies that recognize conserved elements of the closed Env are potentially protective, but are elicited inefficiently. HIV-1 has evolved multiple mechanisms to evade readily elicited antibodies against more open Env conformations. Small-molecule CD4-mimetic compounds (CD4mc) bind the HIV-1 gp120 Env and promote conformational changes similar to those induced by CD4, exposing conserved Env elements to antibodies. Here, we show that a CD4mc synergizes with antibodies elicited by monomeric HIV-1 gp120 to protect monkeys from multiple high-dose intrarectal challenges with a heterologous simian-human immunodeficiency virus (SHIV). The protective immune response persists for at least six months after vaccination. CD4mc should increase the protective efficacy of any HIV-1 Env vaccine that elicits antibodies against CD4-induced conformations of Env.
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