CCR5 Mutation Research Articles

IL23R mutations associated with decreased risk of psoriasis lead to the differential expression of genes implicated in the disease.

Psoriasis is an incurable immune-mediated skin disease, affecting around 1%-3% of the population. Various lines of evidence implicate IL23 as being pivotal in disease. Genetic variants within the IL23 receptor (IL23R) increase the risk of developing psoriasis, and biologic therapies specifically targeting IL23 demonstrated high efficacy in treating disease. IL23 acts via the IL23R, signalling through the STAT3 pathway, mediating the cascade of events that ultimately results in the clinical presentation of psoriasis. Given the essential role of IL23R in disease, it is important to understand the impact of genetic variants on receptor function with respect to downstream gene regulation. Here we developed model systems in CD4+ (Jurkat) and CD8+ (MyLa) T cells to express either the wild type risk or mutant (R381Q) protective form of IL23R. After confirmation that the model system expressed the genes/proteins and had a differential effect on the phosphorylation of STAT3, we used RNAseq to explore differential gene regulation, in particular for genes implicated with risk to psoriasis, at a single time point for both cell types, and in a time course experiment for Jurkat CD4+ T cells. These experiments discovered differentially regulated genes in the cells expressing wild type and mutant IL23R, including HLA-B, SOCS1, RUNX3, CCR5, CXCR3, CCR9, KLF3, CD28, IRF, SOCS6, TNFAIP and ICAM5, that have been implicated in both the IL23 pathway and psoriasis. These genes have the potential to define a IL23/psoriasis pathway in disease, advancing our understanding of the biology behind the disease.

The Lack of the Association of the CCR5 Genotype with the Clinical Presentation and Frequency of Tick-Borne Encephalitis in the Polish Population.

Background: The host factors influencing the susceptibility to and the severity of tick-borne encephalitis (TBE) are poorly defined. The loss-of-function Δ32 mutation in the chemokine receptor gene CCR5 was identified as a risk factor for West Nile encephalitis and possibly for TBE, suggesting a protective role of CCR5 in Flavivirus encephalitis. Methods: We studied the CCR5 genotype in 205 TBE patients stratified by a clinical presentation and 257 controls from the same endemic area (Podlasie, Poland). The genotype distribution between the groups and differences between TBE patients with different genotypes were analyzed. Results: There were 36 (17.6%) CCR5Δ32 heterozygotes and 3 (1.5%) homozygotes in the TBE group, with no statistically significant difference in comparison with the controls. The CCR5Δ32 allele did not associate with the clinical presentation or the severity of TBE. The cerebrospinal fluid (CSF) inflammatory parameters did not differ between the wild-type (wt/wt) and wt/Δ32 genotype patients. The TBE clinical presentation and CSF parameters in three Δ32/Δ32 homozygotes were unremarkable. Conclusions: The lack of association of CCR5Δ32 with the risk and clinical presentation of TBE challenges the suspected CCR5 protective role. CCR5 is not indispensable for the effective immune response against the TBE virus.

Low CCR5 expression protects HIV-specific CD4+ T cells of elite controllers from viral entry

HIV elite controllers maintain a population of CD4 + T cells endowed with high avidity for Gag antigens and potent effector functions. How these HIV-specific cells avoid infection and depletion upon encounter with the virus remains incompletely understood. Ex vivo characterization of single Gag-specific CD4 + T cells reveals an advanced Th1 differentiation pattern in controllers, except for the CCR5 marker, which is downregulated compared to specific cells of treated patients. Accordingly, controller specific CD4 + T cells show decreased susceptibility to CCR5-dependent HIV entry. Two controllers carried biallelic mutations impairing CCR5 surface expression, indicating that in rare cases CCR5 downregulation can have a direct genetic cause. Increased expression of β-chemokine ligands upon high-avidity antigen/TCR interactions contributes to autocrine CCR5 downregulation in controllers without CCR5 mutations. These findings suggest that genetic and functional regulation of the primary HIV coreceptor CCR5 play a key role in promoting natural HIV control.

Clinical parameters, selected HLA and chemokine gene variants associated with late presentation into care of people living with HIV/AIDS.

Late presentation into care remains a significant problem in the diagnosis of HIV infection, and may negatively impact the Joint United Nations Program HIV/AIDS elimination targets. Host genetics affects the tempo of HIV disease progression and therefore may influence clinical status at care entry. Longitudinal data were collected for 863 Caucasian patients followed up at Pomeranian Medical University, Szczecin, Poland. Single nucleotide polymorphisms in CCR2 (rs1799864), CX3CR1 (rs3732378), HLAC-35 (rs9264942), CCR5 promoter (rs1799988) as well as 32 base pair CCR5 mutation and HLA-B*5701 genotypes were correlated with the clinical and immunologic patient status at care entry. Late presentation was defined as baseline CD4 lymphocyte count <350 cells/μL or history of AIDS-defining illness, while advanced HIV disease as baseline CD4 lymphocyte count <200 cells/μL or AIDS. Of the analyzed gene variants, the CCR2 (rs1799864) GG genotype was more frequent among patients presenting for care with a CD4 lymphocyte count <200/μL (82.6% for GG homozygotes vs. 74.5% for allele A carriers, p=0.01). The presence of the heterozygous wt/Δ32 genotype at the CCR5 gene was associated with a higher frequency of asymptomatic infection (18.9% for wt/Δ32 heterozygotes vs. 12% for wt/wt homozygotes, p=0.03). As expected, this association was also observed among late presenters compared to patients presenting for care earlier (13.7% vs. 19,7%, respectively, p=0.04). Finally, HLA-B*5701 was less common among late presenters (5%) compared to patients who entered care early (9.6%, p=0.01) or patients with advanced HIV disease (8.9% vs. 5.2%, p=0.02). Late presentation was associated with the GG homozygous genotype at the CCR2 rs1799864 SNP, while both the HLA-B*5701 variant and the CCR5 wt/Δ32 were associated with more favorable clinical profile at care entry.

Gene Editing Expands the Donor Pool for CCR5-Negative Stem Cell Transplants.

Cell therapy efforts for treating HIV+ patients are challenged by limited availability of donors with naturally occurring CCR5 mutations conferring resistance. Xu etal. (2019) report a CRISPR-based method for disrupting CCR5 in hematopoietic stem cells prior to transplant, providing a proof of concept for expanding the pool of potential donors.

CCR5 Is a Therapeutic Target for Recovery after Stroke and Traumatic Brain Injury

We tested a newly described molecular memory system, CCR5 signaling, for its role in recovery after stroke and traumatic brain injury (TBI). CCR5 is uniquely expressed in cortical neurons after stroke. Post-stroke neuronal knockdown of CCR5 in pre-motor cortex leads to early recovery of motor control. Recovery is associated with preservation of dendritic spines, new patterns of cortical projections to contralateral pre-motor cortex, and upregulation ofCREB and DLK signaling. Administration of a clinically utilized FDA-approved CCR5 antagonist, devised for HIV treatment, produces similar effects on motor recovery post stroke and cognitive decline post TBI. Finally, in a large clinical cohort of stroke patients, carriers for a naturally occurring loss-of-function mutation in CCR5 (CCR5-Δ32) exhibited greater recovery of neurological impairments and cognitive function. In summary, CCR5 is a translational target for neural repair in stroke and TBI and the first reported gene associated with enhanced recovery in human stroke.

Chemokine Receptor 5 Has No Major Role in the Severity of Hepatitis C Virus-Related Liver Damage.

Total or partial inactivation of the chemokine 5 (CC5) pathway, as caused by the CC5 receptor Δ32 deletion (CCR5Δ32), may result in a profound manipulation of immune surveillance with significant consequences on the course and response to therapy of diverse human infections, including HIV. It has been postulated that in chronic hepatitis C (CHC), such a deregulation of CC5 pathway may compromise T cell-dependent antiviral immune responses, which in turn may favor viral persistence. To test this hypothesis, we investigated a cohort of 100 patients with CHC in whom 12 heterozygous and 1 homozygous CCR5Δ32 mutations were detected compared to 8 and none in 98 healthy controls (13% vs. 8.2%, p = 0.36). As patients with and without CCR5Δ32 mutations were similar in terms of histological activity (p = 0.84) and fibrosis stage (p = 0.20) as well as CCR5 tissue expression, we reasonably exclude that this CCR5 mutation is significantly involved in the pathogenesis of CHC and may be a potential therapeutic target. However, deleted patients showed a significantly higher response to pegylated interferon-alfa (PEG-IFN), suggesting that a dormant immune system is more readily primed by immunostimulation.

The prevalence of CCR5-Δ32 mutation in a cohort of Saudi stem cell donors.

CCR5 is a chemokine receptor that was found to be used by HIV as a co-receptor for entering target cells. A 32 bp deletion was described in certain people that rendered CCR5 non-functional. The mutant allele CCR5-Δ32 has been shown to prevent HIV infection. In addition, stem cell transplantation with the CCR5-Δ32 homozygous genotype can lead to clearance of HIV infection. In this study, our aim was to investigate the frequency of CCR5-Δ32 mutation in a cohort of stem cell donors from cord blood bank and stem cell donor registry. A total of 3025 samples were collected from healthy stem cell donors (2625) and from cord blood units (400). DNA was extracted and the CCR5 gene was amplified by polymerase chain reaction (PCR) in a light cycler system using SYBR Green dye. The mutated gene was further confirmed by direct gene sequencing. We found 38 heterozygous for CCR5-Δ32 and one homozygous CCR5 mutation (Δ32/Δ32) out of the 3025 tested individuals. We conclude that the protective CCR5-Δ32 allele appears to be rarely present in Saudi Arabia.

CRISPR/Cas9-Mediated CCR5 Ablation in Human Hematopoietic Stem/Progenitor Cells Confers HIV-1 Resistance In Vivo

Transplantation of hematopoietic stem cells (HSCs) with a naturally occurring CCR5 mutation confers a loss of detectable HIV-1 in the patient, making ablation of the CCR5 gene in HSCs an ideal therapy for an HIV-1 cure. Although CCR5 disruption has been attempted in CD4+ Tcells and hematopoietic stem/progenitor cells (HSPCs), efficient gene editing with high specificity and long-term therapeutic potential remains a major challenge for clinical translation. Here, we established a CRISPR/Cas9 gene editing system in human CD34+ HSPCs and achieved efficient CCR5 ablation evaluated in long-term reconstituted NOD/Prkdcscid/IL-2Rγnull mice. The CCR5 disruption efficiency in our system remained robust in secondary transplanted repopulating hematopoietic cells. More importantly, an HIV-1 resistance effect was observed as indicated by significant reduction of virus titration and enrichment of human CD4+ Tcells. Hence, we successfully established a CRISPR/Cas9 mediated CCR5 ablating system in long-term HSCs, which confers HIV-1 resistance invivo. Our study provides evidence for translating CCR5 gene-edited HSC transplantation for an HIV cure to the clinic.

Possible Impact of 190G > A CCR2 and Δ32 CCR5 Mutations on Decrease of the HBV Vaccine Immunogenicity-A Preliminary Report.

Background: Chemokine genetic variations are involved in infectious diseases such as hepatitis B virus (HBV). Several allelic variants might, in theory, affect the outcome of vaccination. Objectives: This study was carried out to examine the associations of Δ32 CCR5 and 190G > A CCR2 polymorphisms with a response to a primary course of three HBV vaccinations. Methods: Between December 2014 and December 2016, patients from three randomly selected primary care clinics in the West Pomeranian region (Poland), 1 month after receiving the third dose of HBV vaccine, were enrolled. Enzyme-linked immunosorbent assay (ELISA) system version 3.0 was used to detect anti-HBs and anti-HBc totals. The identification of polymorphisms were performed by a polymerase chain reaction technique using a single primer extension assay. Genotype distributions of responders versus non-responders to HBV vaccination were compared on the basis of anti-HBs level. Results: In 149 patients (mean age 60 years) the mean anti-HBs level was 652.2 ± 425.9 mIU/mL (range: 0–1111.0 mIU/mL). There were 14.1% (n = 21) non-responders to the HBV vaccine (anti-HBs < 10.0 mIU/mL). The wild type/Δ32 genotype of CCR5 gene was found in 18.1% participants, and 1.3% were Δ32/Δ32 homozygotes. The frequency of allele A of the CCR2 gene was 11.1%. Lower anti-HBs levels in Δ32/Δ32 homozygotes were observed (Me = 61 mIU/mL vs. Me = 660.2 mIU/mL; p = 0.048). As age was found to be a correlate to the anti-HBs titer (r = −0.218, p = 0.0075; 95% CI: −0.366–−0.059)—an analysis of a co-variance was performed which found a statistically significant (p = 0.04) difference in anti-HBs titres between Δ32/Δ32 homozygotes and other CCR5 genotypes. The association between anti-HBs titres and CCR2 genotypes was not statistically significant. Conclusions: Our study—which is a preliminary report that suggest this topic deserves further observation with larger sample sizes, different ethnicities, and other single nucleotide poly-morphisms (SNPs)—suggests the possible involvement of CCR5 polymorphism in impairing the immunologic response to HBV vaccination, predominantly in relation to the passage of time.

Biased small-molecule ligands for selective inhibition of HIV-1 cell entry via CCR5.

Since the discovery of HIV's use of CCR5 as the primary coreceptor in fusion, the focus on developing small‐molecule receptor antagonists for inhibition hereof has only resulted in one single drug, Maraviroc. We therefore investigated the possibility of using small‐molecule CCR5 agonists as HIV‐1 fusion inhibitors. A virus‐free cell‐based fusion reporter assay, based on mixing “effector cells” (expressing HIV Env and luciferase activator) with “target cells” (expressing CD4, CCR5 wild type or a selection of well‐described mutations, and luciferase reporter), was used as fusion readout. Receptor expression was evaluated by ELISA and fluorescence microscopy. On CCR5 WT, Maraviroc and Aplaviroc inhibited fusion with high potencies (EC 50 values of 91 and 501 nM, respectively), whereas removal of key residues for both antagonists (Glu283Ala) or Maraviroc alone (Tyr251Ala) prevented fusion inhibition, establishing this assay as suitable for screening of HIV entry inhibitors. Both ligands inhibited HIV fusion on signaling‐deficient CCR5 mutations (Tyr244Ala and Trp248Ala). Moreover, the steric hindrance CCR5 mutation (Gly286Phe) impaired fusion, presumably by a direct hindrance of gp120 interaction. Finally, the efficacy switch mutation (Leu203Phe) – converting small‐molecule antagonists/inverse agonists to full agonists biased toward G‐protein activation – uncovered that also small‐molecule agonists can function as direct HIV‐1 cell entry inhibitors. Importantly, no agonist‐induced receptor internalization was observed for this mutation. Our studies of the pharmacodynamic requirements for HIV‐1 fusion inhibitors highlight the possibility of future development of biased ligands with selective targeting of the HIV–CCR5 interaction without interfering with the normal functionality of CCR5.

38. CCR5 Gene Edited Hematopoietic Stem Cells Engraft in Diverse Anatomical Locales and Undergo SHIV-Dependent Positive Selection in Nonhuman Primates

Background: Gene editing in hematopoietic stem/progenitor cells (HSPCs) has rapidly emerged as a promising therapy for a number of diseases, including human immunodeficiency virus (HIV) infection. We have previously demonstrated the feasibility of this approach in nonhuman primates. Here, we leverage our expertise with gene editing in large animal models to interrogate the clonal persistence, trafficking, and antiviral efficacy of CCR5-edited cells in the pigtailed macaque, M. nemestrina. Our objectives were to map the tissue distribution of HSPC-derived, gene edited progeny, understand how individual gene edited HSPCs persist following autologous transplantation, and develop strategies to select for these cells in vivo.Methods: Zinc Finger Nucleases (ZFNs) are used to target the CCR5 locus in macaque HSPCs. Engraftment and persistence of these autologous stem cells, and stem cell-derived lymphoid and myeloid cells, are measured ex vivo and in vivo. Animals are challenged with simian/human immunodeficiency virus (SHIV). Gene edited HSPCs are transplanted either prior to SHIV infection, or in SHIV-infected animals that are treated with combination antiretroviral therapy (cART) in order to approximate a well-suppressed HIV+ patient. Edited cells are measured longitudinally in peripheral blood, bone marrow, gastrointestinal (GI) tract, and lymph nodes, and at necropsy in a panel of 25 tissues, using methods including deep sequencing.Results: We observe up to 14-fold enrichment of CCR5-gene edited memory CD4+ T-cells in SHIV-infected animals, consistent with virus-dependent selection against CCR5 wt memory CD4+ T-cells. Gene edited cells are found in a broad array of anatomical sites, including GI tract and lymph nodes. Spatial and temporal tracking of CCR5 mutations suggests that gene edited cells persist in an analogous fashion to control lentivirus gene-marked cells. Homology directed repair (HDR) pathways can be exploited in macaque CD34+ HSPCs, facilitating knock-in of selectable markers at the disrupted CCR5 locus.Conclusions: Our results in SHIV-infected animals reinforce that this gene editing strategy results in stable engraftment of CCR5-mutated and SHIV-resistant HSPCs and their progeny. Additionally. gene edited CD4+ T-cells undergo positive selection during active infection, further supporting the validity of this approach in the clinic. Moreover, our preliminary ex vivo HDR data suggest that these gene edited cells could be engineered to undergo virus-independent selection.

CCR5 Genotyping and Chemokine Receptor usage among HIV-1 Treatment - Naive and Experienced Patients in India

The reverse transcriptase and proteaseinhibitors form the backbone of the AIDS control programme in India. Increasing reports on transmitted and second line antiretroviral resistance alarms the need for new drugs that could be used for effective patient management. In 2007, the Food and Drug Administration approved the use of CCR5 antagonist in HIV-1 infected treatment experienced patients. Thus, we aimed to determine the clinical feasibility of using CCR5 antagonist in HIV1 infected treatment naive (n=23) and experienced (n=22) patients. Cotropism testing, CCR5 genotyping and mutational resistance profile for first and second line antiretroviral drugs were determined for each patient. None of the patients (0%, 0/45) conferred mutant CCR5 genotype. HIV-1 subtype ‘C’ was found to be predominant in 95.6% (43/45, 95% CI:84100) patients, while 4.4% patients (2/45, 95% CI:0-16) were infected with circulating recombinant forms. Mutational testing reported 43.4% (10/23, 95% CI:26-63) treatment naive and 36.3% (8/22, 95% CI:20-57) treatment experienced patients to confer first and/or secondline antiretroviral drug resistance. Further, cotropism testing revealed use of R5 coreceptor for viral entry in 80% (8/10, 95% CI:48-95) treatment naive and 37.5% (3/8, 95% CI:13-70) treatment experienced drug resistant patients; indicating CCR5 antagonists should be considered for treating HIV-1 infected patients in India.

Frequency of CCR5 Delta 32 Polymorphism and its Relation to Disease Progression in Iranian HIV-1 Positive Individuals

Introduction: Homozygosis or heterozygosis for 32-nucleotide deletion (? 32) within CCR5 gene may influence HIV acquisition and progression in HIV-1 exposed or HIV-infected individuals. In this study, frequency of heterozygosis for CCR5 mutation in an Iranian HIV-infected population was determined and its relation with their disease progression was evaluated. Methods: A total of 194 HIV-infected patients were enrolled. The CCR5?32 in peripheral blood mononuclear cells was detected by the polymerase chain reaction (PCR) and gel electrophoresis. The disease progression was determined based on changes in CD4+ cell counts or clinical presentation of recruited patients. Results: Eight of all 194 patients were heterozygous for (CCR5?32) deletion 32 genotype (wt/del 32). We found no homozygosis for the mutated gene (Del 32/del 32). Of the 103 patients with clinical diagnosis of AIDS, 3 were heterozygote. Although statistically insignificant, the frequency of rapid progression to AIDS was less in heterozygous individuals than the rest (37.5% vs. 53.2%). Discussion: CCR5 mutation is found to be more prevalent in HIV-1 infected Iranians than literature reported data of healthy Iranian cohorts. Due to small sample size, our study did not demonstrate the implication of this mutation in HIV disease progression. Our finding could be related to ethnic variation between the populations and further studies on larger populations may help clarify the role of this mutation in the progression pattern of HIV in Iran.

Amino- and Carboxyl-Terminal CCR5 Mutations in Brazilian HIV-1-Infected Women and Homology Model of p.L55Q CCR5 Mutant.

Genetic factors from an HIV-1 host can affect the rate of progression to AIDS and HIV infection. To investigate the frequency of mutations in the CCR5 gene, HIV-1 samples from infected women and uninfected individuals were selected for sequencing of the CCR5 gene regions encoding the N- and C-terminal protein domains. Physicochemical CCR5 modeling and potential protein domain analysis were performed in order to evaluate the impact of the mutations found in the properties and structure of CCR5. The p.L55Q mutation in the N-terminal protein domain was observed only in uninfected individuals, with an allelic frequency of 1.8%. Physicochemical analysis revealed that the p.L55Q mutation magnified the flexibility and accessibility profiles and the modeling of CCR5 structures showed resulting in a small deviation to the right, as well as a hydrophobic to hydrophilic property alteration. The p.L55Q mutation also resulted in a slight modification of the electrostatic load of this region. Additionally, three novel silent mutations were found at the C-terminal coding region among HIV-1-infected women. The results suggest that the p.L55Q mutation might alter CCR5 conformation. Further studies should be conducted to verify the role of this mutation in HIV-1 susceptibility.

HIV-1 Infection: The Functional Importance of SDF1, CCR2 and CCR5 in Protection and Therapeutics

Abstract The acute or chronic infection of HIV1 resulting to AIDS pandemics is one of the major causes of morbidity and mortality worldwide. The infection, prevalence and propagation of HIV1 depend both on adaptive mutation in virus and host genetic factors. Virus infection to human CD4+ immune cells together is assisted and restricted by various host factors. Presence of mutations in CCR2, CCR5 and CXCR4 ligands SDF1 are associated to protection against HIV1 infection and restriction to AIDS progression. Globally, individuals in various populations harbouring CCR2 (64I), CCR5 (Δ32) and SDF1-3’A mutations are less susceptible to HIV1 infection and decipher delayed onset of AIDS. This review emphasizes the distribution and functional importance of CCR2 (64I), CCR5 (Δ32) and SDF1 (3’A) mutations in protection against HIV1 infection. Lastly the review discuss how CCR2, CCR5 and SDF1 can be explored for development of antagonistic for protection against HIV1 infection.

Genetic Redundancy and Chemokines: CCR5 Δ32 HIV-Resistance Allele

Gene mutation is a change in nucleotide sequence of DNA which results in an impaired or loss of functions of the associated gene. Mutation can occur spontaneously or be induced by mutagenic agent. It is considered deleterious when it affects the phenotypic expression of the gene products. However, some mutations, such as CCR5 gene mutation turns out to be beneficial. HIV virus uses the gene product, CCR5, as a co-receptor along with CD4 receptor to enter the host’s cell. The product of CCR5 mutant gene does not interact with HIV surface antigen, hence blocks the primary entry of the virus and thus provides immunity to AIDS for homozygous carriers and greatly slows the progress of the disease in heterozygous carriers. How about the critical role of the gene, being the gene encoding a member of the beta chemokine receptors, which in turn play an important role in the immune response? This is probably compensated by genomic redundancy of chemokine-receptor functions. Genetic redundancy refers to the situation where the loss of a gene can be completely or partially compensated by one or more other genes. Taken together, CCR5 Δ32 protein product is of clinical significance in conferring resistance to HIV infection and is thought to reduce the surface expression of wild type CCR5. In this review we highlight the origin of CCR5 Δ32 HIVResistance Allele and discuss chemokine receptors’ functional redundancy as the phenomenon compensating for the normal function the allele in individuals carrying the mutation.

A study of the molecular mechanism of binding kinetics and long residence times of human CCR5 receptor small molecule allosteric ligands

The human CCR5 receptor is a co-receptor for HIV-1 infection and a target for anti-viral therapy. A greater understanding of the binding kinetics of small molecule allosteric ligand interactions with CCR5 will lead to a better understanding of the binding process and may help discover new molecules that avoid resistance. Using [(3) H] maraviroc as a radioligand, a number of different binding protocols were employed in conjunction with simulations to determine rate constants, kinetic mechanism and mutant kinetic fingerprints for wild-type and mutant human CCR5 with maraviroc, aplaviroc and vicriviroc. Kinetic characterization of maraviroc binding to the wild-type CCR5 was consistent with a two-step kinetic mechanism that involved an initial receptor-ligand complex (RA), which transitioned to a more stable complex, R'A, with at least a 13-fold increase in affinity. The dissociation rate from R'A, k-2 , was 1.2 × 10(-3) min(-1) . The maraviroc time-dependent transition was influenced by F85L, W86A, Y108A, I198A and Y251A mutations of CCR5. The interaction between maraviroc and CCR5 proceeded according to a multi-step kinetic mechanism, whereby initial mass action binding and later reorganizations of the initial maraviroc-receptor complex lead to a complex with longer residence time. Site-directed mutagenesis identified a kinetic fingerprint of residues that affected the binding kinetics, leading to the conclusion that allosteric ligand binding to CCR5 involved the rearrangement of the binding site in a manner specific to each allosteric ligand.

Precision genome engineering

Precision genome engineering

Reversible and Efficient Activation of HIV-1 Cell Entry by a Tyrosine-Sulfated Peptide Dissects Endocytic Entry and Inhibitor Mechanisms

HIV-1 membranes contain gp120-gp41 trimers. Binding of gp120 to CD4 and a coreceptor (CCR5 or CXCR4) reduces the constraint on metastable gp41, enabling a series of conformational changes that cause membrane fusion. An analytic difficulty occurs because these steps occur slowly and asynchronously within cohorts of adsorbed virions. We previously isolated HIV-1JRCSF variants that efficiently use CCR5 mutants severely damaged in the tyrosine-sulfated amino terminus or extracellular loop 2. Surprisingly, both independent adaptations included gp120 mutations S298N, F313L, and N403S, supporting other evidence that they function by weakening gp120's grip on gp41 rather than by altering gp120 binding to specific CCR5 sites. Although several natural HIV-1 isolates reportedly use CCR5(Δ18) (CCR5 with a deletion of 18 N-terminal amino acids, including the tyrosine-sulfated region) when the soluble tyrosine-sulfated peptide is present, we show that HIV-1JRCSF with the adaptive mutations [HIV-1JRCSF(Ad)] functions approximately 100 times more efficiently and that coreceptor activation is reversible, enabling synchronous efficient entry control under physiological conditions. This system revealed that three-stranded gp41 folding intermediates susceptible to the inhibitor enfuvirtide form slowly and asynchronously on cell surface virions but resolve rapidly, with virions generally forming only one target. Adsorbed virions asynchronously and transiently become competent for entry at 37°C but are inactivated if the CCR5 peptide is absent during their window of opportunity. This competency is conferred by endocytosis, which results in inactivation if the peptide is absent. For both wild-type and adapted HIV-1 isolates, early gp41 refolding steps obligatorily occur on cell surfaces, whereas the final step(s) is endosomal. This system powerfully dissects HIV-1 entry and inhibitor mechanisms. We present a powerful means to reversibly and efficiently activate or terminate HIV-1 entry by adding or removing a tyrosine-sulfated CCR5 peptide from the culture medium. This system uses stable cell clones and a variant of HIV-1JRCSF with three adaptive mutations. It enabled us to show that CCR5 coreceptor activation is rapidly reversible and to dissect aspects of entry that had previously been relatively intractable. Our analyses elucidate enfuvirtide (T-20) function and suggest that HIV-1 virions form only one nonredundant membrane fusion complex on cell surfaces. Additionally, we obtained novel and conclusive evidence that HIV-1 entry occurs in an assembly line manner, with some steps obligatorily occurring on cell surfaces and with final membrane fusion occurring in endosomes. Our results were confirmed for wild-type HIV-1. Thus, our paper provides major methodological and mechanistic insights about HIV-1 infection.