Mutational Escape in HIV-1 CTL Epitopes Leads to Increased Binding to Inhibitory Myelomonocytic MHC Class I Receptors

Escape mutations in HIV-1 cytotoxic T cell (CTL) epitopes can abrogate recognition by the TCR of HIV-1-specific CD8+ T cells, but may also change interactions with alternative MHC class I receptors. Here, we show that mutational escape in three HLA-A11-, B8- and B7- restricted immunodominant HIV-1 CTL epitopes consistently enhances binding of the respective peptide/MHC class I complex to Immunoglobulin-like transcript 4 (ILT4), an inhibitory myelomonocytic MHC class I receptor expressed on monocytes and dendritic cells. In contrast, mutational escape in an alternative immunodominant HLA-B57-restricted CTL epitope did not affect ILT4-mediated recognition by myelomonocytic cells. This suggests that in addition to abrogating recognition by HIV-1-specific CD8 T cells, mutational escape in some, but not all CTL epitopes may mediate important immunoregulatory effects by increasing binding properties to ILT4, and augmenting ILT4-mediated inhibitory effects of professional antigen-presenting cells.National Institutes of Health (U.S.) (Grant R01 AI078799)National Institutes of Health (U.S.) (Grant P01 AI074415)Doris Duke Charitable Foundatio

Systemic inhibition of myeloid dendritic cells by circulating HLA class I molecules in HIV-1 infection

<p>Abstract</p> <p>Background</p> <p>HIV-1 infection is associated with profound dysfunction of myeloid dendritic cells, for reasons that remain ill-defined. Soluble HLA class I molecules can have important inhibitory effects on T cells and NK cells, but may also contribute to reduced functional properties of professional antigen-presenting cells. Here, we investigated the expression of soluble HLA class I isoforms during HIV-1 infection and assessed their functional impact on antigen-presenting characteristics of dendritic cells.</p> <p>Results</p> <p>Soluble HLA class I molecules were highly upregulated in progressive HIV-1 infection as determined by quantitative Western blots. This was associated with strong increases of intracellular expression of HLA class I isoforms in dendritic cells and monocytes. Using mixed lymphocyte reactions, we found that soluble HLA class I molecules effectively inhibited the antigen-presenting properties of dendritic cells, however, there was no significant influence of HLA class I molecules on the cytokine-secretion properties of these cells. The immunomodulatory effects of soluble HLA class I molecules were mediated by interactions with inhibitory myelomonocytic MHC class I receptors from the Leukocyte Immunoglobulin Like Receptor (LILR) family.</p> <p>Conclusions</p> <p>During progressive HIV-1 infection, soluble HLA class I molecules can contribute to systemic immune dysfunction by inhibiting the antigen-presenting properties of myeloid dendritic cells through interactions with inhibitory myelomonocytic HLA class I receptors.</p

Developmental Pathway of the MPER-Directed HIV-1-Neutralizing Antibody 10E8

Antibody 10E8 targets the membrane-proximal external region (MPER) of HIV-1 gp41, neutralizes >97% of HIV-1 isolates, and lacks the auto-reactivity often associated with MPER-directed antibodies. The developmental pathway of 10E8 might therefore serve as a promising template for vaccine design, but samples from time-of-infection—often used to infer the B cell record—are unavailable. In this study, we used crystallography, next-generation sequencing (NGS), and functional assessments to infer the 10E8 developmental pathway from a single time point. Mutational analysis indicated somatic hypermutation of the 2nd-heavy chain-complementarity determining region (CDR H2) to be critical for neutralization, and structures of 10E8 variants with V-gene regions reverted to genomic origin for heavy-and-light chains or heavy chain-only showed structural differences >2 Å relative to mature 10E8 in the CDR H2 and H3. To understand these developmental changes, we used bioinformatic sieving, maximum likelihood, and parsimony analyses of immunoglobulin transcripts to identify 10E8-lineage members, to infer the 10E8-unmutated common ancestor (UCA), and to calculate 10E8-developmental intermediates. We were assisted in this analysis by the preservation of a critical D-gene segment, which was unmutated in most 10E8-lineage sequences. UCA and early intermediates weakly bound a 26-residue-MPER peptide, whereas HIV-1 neutralization and epitope recognition in liposomes were only observed with late intermediates. Antibody 10E8 thus develops from a UCA with weak MPER affinity and substantial differences in CDR H2 and H3 from the mature 10E8; only after extensive somatic hypermutation do 10E8-lineage members gain recognition in the context of membrane and HIV-1 neutralization

HLA-B*35-Px–mediated acceleration of HIV-1 infection by increased inhibitory immunoregulatory impulses

A subset of HLA-B*35 alleles, B*35-Px, are strongly associated with accelerated HIV-1 disease progression for reasons that are not understood. Interestingly, the alternative set of B*35 subtypes, B*35-PY, have no detectable impact on HIV-1 disease outcomes, even though they can present identical HIV-1 epitopes as B*35-Px molecules. Thus, the differential impact of these alleles on HIV-1 disease progression may be unrelated to interactions with HIV-1–specific CD8+ T cells. Here, we show that the B*35-Px molecule B*3503 binds with greater affinity to immunoglobulin-like transcript 4 (ILT4), an inhibitory MHC class I receptor expressed on dendritic cells, than does the B*35-PY molecule B*3501, even though these two B*35 molecules differ by only one amino acid and present identical HIV-1 epitopes. The preferential recognition of B*3503 by ILT4 was associated with significantly stronger dendritic cell dysfunction in in vitro functional assays. Moreover, HIV-1–infected carriers of B*3503 had poor dendritic cell functional properties in ex vivo assessments when compared with carriers of the B*3501 allele. Differential interactions between HLA class I allele subtypes and immunoregulatory MHC class I receptors on dendritic cells thus provide a novel perspective for the understanding of MHC class I associations with HIV-1 disease progression and for the manipulation of host immunity against HIV-1

Виртуальный скрининг и идентификация потенциальных ингибиторов ВИЧ-1 на основе кросс-реактивного нейтрализующего антитела N6

Six potential peptidomimetics of the cross-reactive neutralizing anti-HIV-1 antibody N6 that are able to mimic the pharmacophoric features of this immunoglobulin by specific and effective interactions with the CD4-binding site of the viral gp120 protein were identified by virtual screening and molecular modeling. The key role in the interaction of these compounds with gp120 is shown to play multiple van der Waals contacts with conserved residues of the gp120 Phe43 cavity critical for the HIV binding to cellular receptor CD4, as well as hydrogen bonds with Asp-368gp120 that increase the chemical affinity without activating unwanted allosteric effect. According to the data of molecular dynamics, the complexes of the identified ligands with gp120 are energetically stable and show the lower values of binding free energy compared with the HIV-1 inhibitors NBD-11021 and DMJ-II-121 used in the calculations as a positive control. The identified compounds may be involved in the design of novel antiviral drugs presenting HIV-1 inhibitors that block the early stages of the development of HIV infection.Методами виртуального скрининга и молекулярного моделирования идентифицированы 6 потенциальных пептидомиметиков кросс-реактивного нейтрализующего анти-ВИЧ-1 антитела N6, способных имитировать фармакофорные свойства этого иммуноглобулина путем специфических и эффективных взаимодействий с CD4-связывающим сайтом белка gp120 оболочки вируса. Показано, что ключевую роль во взаимодействии этих соединений с белком gp120 играют многочисленные ван-дер-ваальсовы контакты с консервативными остатками Phe43-полости гликопротеина, критическими для связывания ВИЧ-1 с клеточным рецептором CD4, а также водородные связи с остатком Asp-368gp120, образование которых увеличивает химическое сродство без активации нежелательного аллостерического эффекта. Согласно данным молекулярной динамики, комплексы обнаруженных лигандов с белком gp120 энергетически стабильны и характеризуются более низкими значениями свободной энергии связывания по сравнению с ингибиторами ВИЧ-1 NBD-11021 и DMJ-II-121, использованными в расчетах в качестве контрольных соединений. Идентифицированные соединения могут быть использованы в работах по созданию новых противовирусных препаратов – ингибиторов проникновения ВИЧ-1, блокирующих ранние стадии развития ВИЧ-инфекции

Идентификация функциональных миметиков нейтрализующего анти-вич антитела n6 методами виртуального скрининга и молекулярного моделирования

Three chemical compounds presenting functional mimetics of neutralizing anti-HIV-1 antibody N6 were identified by an integrated approach including virtual screening, high-throughput docking and molecular dynamics. Using molecular docking, the identified compounds are predicted to be able to block three key regions of the HIV-1 gp120 protein by formation of a wide network of intermolecular contacts with the glycoprotein residues critical for the virus binding to primary receptor CD4. It is shown that the complexes of these compounds with gp120 exhibit low values of dissociation constant and Gibbs free energy, which validates a high efficacy of intermolecular interactions stabilizing these supramolecular structures. Based on the data obtained, the identified compounds are assumed to form promising basic structures for the development of novel, potent and broad anti-HIV-1 drugs mimicking structural and functional properties of the cross-reactive neutralizing antibody N6.С помощью комплексного подхода, включающего методы виртуального скрининга, высокопроизводительного докинга и молекулярной динамики, обнаружены три химических соединения - функциональных ми-метика нейтрализующего анти-ВИЧ антитела N6. Методами молекулярного докинга предсказано, что идентифицированные соединения способны блокировать три ключевых области белка gp120 ВИЧ-1 путем образования широкой сети межмолекулярных контактов с остатками гликопротеина, критическими для связывания вируса с первичным рецептором CD4. Показано, что комплексы этих соединений с белком gp120 характеризуются низкими значениями констант диссоциации и свободной энергии Гиббса, что подтверждает высокую эффективность межмолекулярных взаимодействий, стабилизирующих эти надмолекулярные структуры. На основании полученных результатов сделан вывод о том, что идентифицированные соединения формируют перспективные базовые структуры для разработки новых эффективных лекарственных препаратов против ВИЧ-1 широкого спектра действия, имитирующих структурно-функциональные свойства кросс-реактивного нейтрализующего антитела N6

Vascular endothelial growth factor C promotes cervical cancer metastasis via up-regulation and activation of RhoA/ROCK-2/moesin cascade

<p>Abstract</p> <p>Background</p> <p>The elevated expression of vascular endothelial growth factor C (VEGF-C) is correlated with clinical cervical cancer metastasis and patient survival, which is interpreted by VEGF-C functions to stimulate angiogenesis and lymphatic genesis. However, the direct impact of VEGF-C on cervical cancer cell motility remains largely unknown.</p> <p>Methods</p> <p>In this study, we investigated the effects of VEGF-C on actin cytoskeleton remodeling and on cervical cancer cell migration and invasion and how the actin-regulatory protein, moesin regulated these effects through RhoA/ROCK-2 signaling pathway.</p> <p>Results</p> <p>On cervical carcinoma cell line SiHa cells, exposure of VEGF-C triggered remodeling of the actin cytoskeleton and the formation of membrane ruffles, which was required for cell movement. VEGF-C significantly enhanced SiHa cells horizontal migration and three-dimensional invasion into matrices. These actions were dependent on increased expression and phosphorylation of the actin-regulatory protein moesin and specific moesin siRNA severely impaired VEGF-C stimulated-cell migration. The extracellular small GTPase RhoA/ROCK-2 cascade mediated the increased moesin expression and phosphorylation, which was discovered by the use of Y-27632, a specific inhibitor of Rho kinase and by transfected constitutively active, dominant-negative RhoA as well as ROCK-2 SiRNA. Furthermore, in the surgical cervical specimen from the patients with FIGO stage at cervical intra-epithelial neoplasia and I-II cervical squamous cell carcinoma, the expression levels of moesin were found to be significantly correlated with tumor malignancy and metastasis.</p> <p>Conclusions</p> <p>These results implied that VEGF-C promoted cervical cancer metastasis by upregulation and activation of moesin protein through RhoA/ROCK-2 pathway. Our findings offer new insight into the role of VEGF-C on cervical cancer progression and may provide potential targets for cervical cancer therapy.</p

17β-Estradiol Enhances Breast Cancer Cell Motility and Invasion via Extra-Nuclear Activation of Actin-Binding Protein Ezrin

Estrogen promotes breast cancer metastasis. However, the detailed mechanism remains largely unknown. The actin binding protein ezrin is a key component in tumor metastasis and its over-expression is positively correlated to the poor outcome of breast cancer. In this study, we investigate the effects of 17β-estradiol (E2) on the activation of ezrin and its role in estrogen-dependent breast cancer cell movement. In T47-D breast cancer cells, E2 rapidly enhances ezrin phosphorylation at Thr567 in a time- and concentration-dependent manner. The signalling cascade implicated in this action involves estrogen receptor (ER) interaction with the non-receptor tyrosine kinase c-Src, which activates the phosphatidylinositol-3 kinase/Akt pathway and the small GTPase RhoA/Rho-associated kinase (ROCK-2) complex. E2 enhances the horizontal cell migration and invasion of T47-D breast cancer cells in three-dimensional matrices, which is reversed by transfection of cells with specific ezrin siRNAs. In conclusion, E2 promotes breast cancer cell movement and invasion by the activation of ezrin. These results provide novel insights into the effects of estrogen on breast cancer progression and highlight potential targets to treat endocrine-sensitive breast cancers

Structure and immune recognition of trimeric pre-fusion HIV-1 Env.

CAPRISA, 2014.The human immunodeficiency virus type 1 (HIV-1) envelope (Env) spike, comprising three gp120 and three gp41 subunits, is a conformational machine that facilitates HIV-1 entry by rearranging from a mature unliganded state, through receptor-bound intermediates, to a post-fusion state. As the sole viral antigen on the HIV-1 virion surface, Env is both the target of neutralizing antibodies and a focus of vaccine efforts. Here we report the structure at 3.5 Å resolution for an HIV-1 Env trimer captured in a mature closed state by antibodies PGT122 and 35O22. This structure reveals the pre-fusion conformation of gp41, indicates rearrangements needed for fusion activation, and defines parameters of immune evasion and immune recognition. Pre-fusion gp41 encircles amino- and carboxy-terminal strands of gp120 with four helices that form a membrane-proximal collar, fastened by insertion of a fusion peptide-proximal methionine into a gp41-tryptophan clasp. Spike rearrangements required for entry involve opening the clasp and expelling the termini. N-linked glycosylation and sequence-variable regions cover the pre-fusion closed spike; we used chronic cohorts to map the prevalence and location of effective HIV-1-neutralizing responses, which were distinguished by their recognition of N-linked glycan and tolerance for epitope-sequence variation

A Two-Stage Kalman Filter Approach for Robust and Real-Time Power System State Estimation

As electricity demand continues to grow and renewable energy increases its penetration in the power grid, real-time state estimation becomes essential for system monitoring and control. Recent development in phasor technology makes it possible with high-speed time-synchronized data provided by phasor measurement units (PMUs). In this paper, we present a two-stage Kalman filter approach to estimate the static state of voltage magnitudes and phase angles, as well as the dynamic state of generator rotor angles and speeds. Kalman filters achieve optimal performance only when the system noise characteristics have known statistical properties (zero-mean, Gaussian, and spectrally white). However, in practice, the process and measurement noise models are usually difficult to obtain. Thus, we have developed the adaptive Kalman filter with inflatable noise variances (AKF with InNoVa), an algorithm that can efficiently identify and reduce the impact of incorrect system modeling and/or erroneous measurements. In stage one, we estimate the static state from raw PMU measurements using the AKF with InNoVa; then in stage two, the estimated static state is fed into an extended Kalman filter to estimate the dynamic state. The simulations demonstrate its robustness to sudden changes of system dynamics and erroneous measurements. © 2010-2012 IEEE