Biology subjects

Colin, P.

Publications and source records attributed to Colin, P..

3 recordsLinked to original sources

bioRxiv2023

Glycan heterogeneity as a cause of the persistent fraction in HIV-1 neutralization

Neutralizing antibodies (NAbs) to multiple epitopes on the HIV-1 envelope glycoprotein (Env) have been isolated from infected persons. The potency of NAbs is more often measured than the size of the persistent fraction of infectivity at maximum neutralization, which may also influence preventive efficacy by active or passive immunization and the therapeutic outcome of the latter. HIV-1 CZA97.012, a clone of a Clade C isolate, is neutralized to [~]100% by many NAbs. But here NAb PGT151, directed to a fusion-peptide epitope, was shown to leave a persistent fraction of 15%. NAb PGT145, ligating the Env-trimer apex, was less potent but more effective. We sought explanations of the different persistent fractions by depleting pseudoviral populations of the most PGT151- and PGT145-reactive virions. Thereby, neutralization by the non-depleting NAb increased; it decreased by the depleting NAb. Furthermore, depletion by PGT151 increased sensitivity to autologous neutralization by sera from rabbits immunized with soluble native-like CZA97.012 trimer: substantial persistent fractions were reduced. NAbs in these sera target epitopes comprising residue D411 at the V4-{beta}19 transition in a defect of the glycan shield on CZA97.012 Env. Affinity-fractionated soluble native-like CZA97.012 trimer showed commensurate antigenic differences in analyses by ELISA and surface plasmon resonance. We then demonstrated glycan differences between PGT151- and PGT145-purified trimer fractions by mass spectrometry, providing one explanation for the differential antigenicity. These differences were interpreted in relation to a new structure at 3.4-[A] resolution of the soluble CZA97.012 trimer determined by cryo-electron microscopy. PGT151-purified trimer showed a closed conformation, refuting apex opening as the cause of reduced PGT145 binding. The evidence suggests that differences in binding and neutralization after trimer purification or PV depletion with PGT145 or PGT151 are caused by variation in glycosylation, and that some glycan variants confer antigenic heterogeneity through direct effects on antibody contacts, whereas others act allosterically. Author SummaryNeutralizing antibodies block the entry of HIV-1 into cells and protect against HIV-1 infection in animal models. Therefore, a goal of vaccination is to elicit antibodies that potently neutralize most HIV-1 variants. Such antibodies suppress virus levels when given to HIV-1-infected patients. Their potency is often measured as the concentration that gives 50% or 80% neutralization. But higher degrees of neutralization are needed to protect an organism from infection. And for some antibodies a ceiling is reached, so that even with increased concentrations a constant fraction of infectious virus persists. We studied the carbohydrate moieties on the envelope glycoprotein, which is the sole target for neutralizing antibodies, of one HIV-1 isolate of the most widespread subtype, Clade C, prevalent in Africa and Asia. We show how differences in carbohydrates can contribute to persistent infectivity, because distinct carbohydrates fit different antibodies. With a new three-dimensional structure of the entry-mediating protein from the Clade-C isolate, we illustrate that some carbohydrate differences occur exactly where the antibodies bind, whereas others are located elsewhere and can act indirectly. When we combined two neutralizing antibodies the persistent infectivity shrank. Our results reinforce the need for multiple specificities of neutralizing antibodies in prevention and therapy.

immunology↗

bioRxiv2022

HIV-1 cell-to-cell spread overcomes the virus entry block of non-macrophage-tropic strains in macrophages

Macrophages (M{Phi}) are increasingly recognized as HIV-1 target cells involved in the pathogenesis and persistence of infection. Paradoxically, in vitro infection assays suggest that virus isolates are mostly T-cell-tropic and rarely M{Phi}-tropic. The latter are assumed to emerge under CD4+ T-cell paucity in tissues such as the brain or at late stage when the CD4 T-cell count declines. However, assays to qualify HIV-1 tropism use cell-free viral particles and may not fully reflect the conditions of in vivo M{Phi} infection through cell-to-cell viral transfer. Here, we investigated the capacity of viruses expressing primary envelope glycoproteins (Envs) with CCR5 and/or CXCR4 usage from different stages of infection, including transmitted/founder Envs, to infect M{Phi} by a cell-free mode and through cell-to-cell transfer from infected CD4+ T cells. The results show that most viruses were unable to enter M{Phi} as cell-free particles, in agreement with the current view that non-M-tropic viruses inefficiently use CD4 and/or CCR5 or CXCR4 entry receptors on M{Phi}. In contrast, all viruses could be effectively cell-to-cell transferred to M{Phi} from infected CD4+ T cells. We further showed that viral transfer proceeded through Env-dependent cell-cell fusion of infected T cells with M{Phi} targets, leading to the formation of productively infected multinucleated giant cells. Compared to cell-free infection, infected T-cell/M{Phi} contacts showed enhanced interactions of R5 M- and non-M-tropic Envs with CD4 and CCR5, resulting in a reduced dependence on receptor expression levels on M{Phi} for viral entry. Altogether, our results show that virus cell-to-cell transfer overcomes the entry block of isolates initially defined as non-macrophage-tropic, indicating that HIV-1 has a more prevalent tropism for M{Phi} than initially suggested. This sheds light into the role of this route of virus cell-to-cell transfer to M{Phi} in CD4+ T cell rich tissues for HIV-1 transmission, dissemination and formation of tissue viral reservoirs. Author SummaryUnderstanding how HIV-1 hijacks the functions of immune cells to promote viral spreading remains a challenge in the fight against infection. M{Phi} are ubiquitous tissue-resident cells, involved in tissue homeostasis and immunity. In HIV-1 infection, along with CD4+ T lymphocytes, M{Phi} serve as vectors for virus dissemination and as viral reservoirs, impeding HIV-1 eradication. However, the mechanisms of their infection remain incompletely understood. A paradox is that infected M{Phi} are found in a large range of tissues whereas in vitro cellular tropism assays indicate that only a limited number of HIV-1 isolates can enter M{Phi}. We hypothesized that these assays, which evaluate infection using cell-free viruses, might not fully reflect the modes of M{Phi} infection in patients. We report here that virus cell-to-cell transfer through cell-cell fusion with infected CD4+ T cells is a very effective means of infecting M{Phi}, even with virus isolates characterized as non-macrophage tropic in cell-free infection. This intercellular viral transfer is facilitated by enhanced interactions between the HIV-1 envelope glycoproteins and cellular entry receptors. We propose that M{Phi} infection through viral transfer from infected CD4+ T cells impacts different aspects of the pathophysiology of HIV-1 infection, renewing our understanding of the role of M{Phi} in HIV-1 pathogenesis and persistence.

microbiology↗

bioRxiv2021

Single-molecule imaging reveals distinct effects of ligands on CCR5 dynamics depending on its dimerization status

G protein-coupled receptors (GPCR) are present at the cell surface in different conformational and oligomeric states. However, how these states impact GPCRs biological function and therapeutic targeting remains incompletely known. Here, we investigated this issue in living cells for the CC chemokine receptor 5 (CCR5), a major receptor in inflammation and the principal entry co-receptor for Human Immunodeficiency Viruses (HIV-1). We used TIRF microscopy and an original statistical method to track and classify the motion of different receptors subpopulations. We showed a diversity of ligand-free forms of CCR5 at the cell surface constituted of various oligomeric states and exhibiting transient Brownian and restricted motions. These forms were stabilized differently by distinct ligands. In particular, agonist stimulation restricted the mobility of CCR5 and led to its clustering, a feature depending on {beta}-arrestin, while inverse agonist stimulation exhibited the opposite effect. These results suggest a link between receptor activation and immobilization. Applied to HIV-1 envelope glycoproteins gp120, our quantitative analysis revealed agonist-like properties of gp120s. Distinct gp120s influenced CCR5 dynamics differently, suggesting that they stabilize different CCR5 conformations. Then, using a dimerization-compromized mutant, we showed that dimerization (i) impacts CCR5 precoupling to G proteins, (ii) is a pre-requisite for the immobilization and clustering of receptors upon activation, and (iii) regulates receptor endocytosis, thereby impacting the fate of activated receptors. This study demonstrates that tracking the dynamic behavior of a GPCR is an efficient way to link GPCR conformations to their functions, therefore improving the development of drugs targeting specific receptor conformations.

cell biology↗