Increasing COVID-19 vaccination in the United States: projected impact on cases, hospitalizations, and deaths by age and racial group.

OBJECTIVES: Minority populations in the United States face a disproportionate burden of illness from COVID-19 infection and have lower vaccination rates compared with other groups. This study estimated the equity implications of increased COVID-19 vaccination in the United States, with a focus on the number of cases, hospitalizations, and deaths avoided. STUDY DESIGN: This was an observational real-world modeling study. METHODS: Data from the Centers for Disease Control and Prevention (CDC) were used to identify the remaining unvaccinated US population by county, age, and race as of October 22, 2021. The number of COVID-19 cases, hospitalizations, and deaths avoided were calculated based on case incidence and death data from the CDC, along with data on race- and age-specific hospitalization multipliers, under a scenario in which half of the remaining unvaccinated population per county, race, and age group obtained a full vaccine regimen. RESULTS: Vaccinating half of the remaining unvaccinated population in each age and race subgroup within counties would result in an estimated 22.09 million COVID-19 cases avoided, 1.38 million hospitalizations avoided, and 150,000 deaths avoided over 12 months. Some minority groups, particularly Black and Hispanic/Latino populations, were projected to experience substantial benefits from increased vaccination rates as they face both lower vaccination rates and worse outcomes if infected with COVID-19. CONCLUSIONS: Increasing COVID-19 vaccination in the United States not only benefits the population as a whole but also serves as a potentially useful lever to reduce the disproportionate burden of COVID-19 illness among minority populations.

Pharmacological Characterization of a Novel Beta 3 Adrenergic Agonist, Vibegron: Evaluation of Antimuscarinic Receptor Selectivity for Combination Therapy for Overactive Bladder.

Although the physiologic role of muscarinic receptors in bladder function and the therapeutic efficacy of muscarinic antagonists for the treatment of overactive bladder are well established, the role of ß3-adrenergic receptors (ß3ARs) and their potential as therapeutics is just emerging. In this manuscript, we characterized the pharmacology of a novel ß3AR agonist vibegron (MK-4618, KRP-114V) and explored mechanistic interactions of ß3AR agonism and muscarinic antagonism in urinary bladder function. Vibegron is a potent, selective full ß3AR agonist across species, and it dose dependently increased bladder capacity, decreased micturition pressure, and increased bladder compliance in rhesus monkeys. The relaxation effect of vibegron was enhanced when combined with muscarinic antagonists, but differentially influenced by muscarinic receptor subtype selectivity. The effect was greater when vibegron was co-administered with tolterodine, a nonselective antagonist, compared with coadministration with darifenacin, a selective M3 antagonist. Furthermore, a synergistic effect for bladder strip relaxation was observed with the combination of a ß3AR agonist and tolterodine in contrast to simple additivity with darifenacin. To determine expression in rhesus bladder, we employed a novel ß3AR agonist probe, [3H]MRL-037, that selectively labels ß3 receptors in both urothelium and detrusor smooth muscle. Vibegron administration caused a dose-dependent increase in circulating glycerol and fatty acid levels in rhesus and rat in vivo, suggesting these circulating lipids can be surrogate biomarkers. The translation of our observation to the clinic has yet to be determined, but the combination of ß3AR agonists with M2/M3 antimuscarinics has the potential to redefine the standard of care for the pharmacological treatment of overactive bladder.

TL1A/TNFSF15 directly induces proinflammatory cytokines, including TNFα, from CD3+CD161+ T cells to exacerbate gut inflammation.

Tumor necrosis factor (TNF)-like cytokine 1A (TL1A)/TNF superfamily member 15 (TNFSF15) is a proinflammatory cytokine and TNFα superfamily member that is linked preclinically and clinically to inflammatory bowel disease (IBD). By homology and function, TNFα is its closest family member. In this study, we investigated the mechanism of TL1A-induced inflammation in CD4+ T cells and compared it with the TNFα pathway. We found that TL1A induces proinflammatory cytokines, including TNFα, from isolated human CD4+CD161+ T cells, whereas these cells were resistant to TNFα treatment. Anti-TNFα failed to block TL1A-induced cytokine production, indicating that the effects of TL1A are direct. Lastly, CD161 and TL1A expression were significantly and selectively increased in gut tissue biopsies, but not in the peripheral blood, from IBD patients. Thus, TLIA not only functions upstream of TNFα, driving its expression from CD161+ T cells, but is also independent of TNFα. These findings may have therapeutic IBD implications.

Assessment of chemokine receptor function on monocytes in whole blood: In vitro and ex vivo evaluations of a CCR2 antagonist.

Inhibition of monocyte and macrophage function by targeting chemokine receptors represents an attractive strategy for therapeutic intervention in inflammatory diseases. We describe an assay to assess chemokine receptor function on whole blood monocytes by measuring chemokine stimulated change in cell shape as measured by flow cytometry. The relative potential of the chemokine receptors CCR1, CCR2, CCR5, CX(3)CR1, and CXCR4 to activate monocytes in whole blood was evaluated and compared. Analysis of MCP-1 response for monocytes in blood from numerous donors revealed that the assay method had excellent intra-donor reproducibility and sensitivity. Further, the utility of this assay to determine target engagement by chemokine receptor antagonists was demonstrated using a CCR2 antagonist in rhesus monkeys. Blockade of CCR2 on whole blood monocytes was demonstrated ex vivo on blood samples collected from rhesus monkeys administered a small molecule CCR2 antagonist (MK-0812). Using a delayed-type hypersensitivity reaction to elicit monocyte recruitment to the skin of rhesus monkeys, we also evaluated the ability of MK-0812 to block monocyte migration in vivo. Blockade of CCR2 stimulation of whole blood monocytes was correlated with the inhibition of monocyte recruitment to the skin, validating the potential to use this approach in the evaluation of dose selection for chemokine receptor antagonists clinically.

Unaltered graft survival and intragraft lymphocytes infiltration in the cardiac allograft of Cxcr3-/- mouse recipients.

Previous studies showed that absence of chemokine receptor Cxcr3 or its blockade prolong mouse cardiac allograft survival. We evaluated the effect of the CXCR3 receptor antagonist MRL-957 on cardiac allograft survival, and also examined the impact of anti-CXCR3 mAb in human CXCR3 knock-in mice. We found only a moderate increase in graft survival (10.5 and 16.6 days, p < 0.05) using either the antagonist or the antibody, respectively, compared to control (8.7 days). We re-evaluated cardiac allograft survival with two different lines of Cxcr3(-/-) mice. Interestingly, in our hands, neither of the independently derived Cxcr3(-/-) lines showed remarkable prolongation, with mean graft survival of 9.5 and 10.8 days, respectively. There was no difference in the number of infiltrating mononuclear cells, expansion of splenic T cells or IFN-gamma production of alloreactive T cells. Mechanistically, an increased other chemokine receptor fraction in the graft infiltrating CD8 T cells in Cxcr3(-/-) recipients compared to wild-type recipients suggested compensatory T-cell trafficking in the absence of Cxcr3. We conclude Cxcr3 may contribute to, but does not govern, leukocyte trafficking in this transplant model.

Mice overexpressing chemokine ligand 2 (CCL2) in astrocytes display enhanced nociceptive responses.

Recent findings demonstrate that chemokines, and more specifically CC chemokine ligand 2 (CCL2 or monocyte chemoattractant protein-1), play a major role in pain processing. In the present study, we assess nociceptive responses of mice that overexpressed CCL2 under control of glial fibrillary acidic protein promoter (CCL2 tg). In models of acute nociception CCL2 tg mice demonstrated significantly enhanced nociceptive behavior relative to wild-type controls in responses to both thermal (hot plate) and chemical (formalin test) stimulus modalities. There were no differences in mechanical allodynia in the partial sciatic nerve ligation model, in terms of either magnitude or duration of the allodynic response; however, both groups responded to the maximal extent measurable. In a model of inflammatory pain, elicited by intraplantar administration of complete Freund's adjuvant (CFA), CCL2 tg mice displayed both greater edema and thermal hyperalgesia compared with control mice. In control mice, edema and hyperalgesia returned to baseline values 5-7 days post CFA. However, in CCL2 tg mice, thermal hyperalgesia was significantly different from baseline up to 3 weeks post CFA. Parallel to these enhanced behavioral responses CCL2 serum levels were significantly greater in CCL2 overexpressing mice and remained elevated 7 days post CFA. Consequently, proinflammatory cytokine mRNA expression (IL-1beta, IL-6, and TNFalpha) levels were greater in skin, dorsal root ganglia (DRG), and spinal cord, whereas the anti-inflammatory cytokine (IL-10) level was lower in skin and DRG in CCL2 overexpressing mice than in control mice. Taken together with data from CCR2-deficient mice, these present data confirm a key role of CCL2/CCR2 axis in pain pathways and suggest that inhibiting this axis may result in novel pain therapies.

Design, synthesis, and SAR of heterocycle-containing antagonists of the human CCR5 receptor for the treatment of HIV-1 infection.

Replacement of the large hydantoin-indole moiety from our previous work with a variety of smaller heterocyclic analogues gave rise to potent CCR5 antagonists having binding affinity comparable to the hydantoin analogues. The synthesis, SAR, and biological profiles of this class of antagonists are described.

Discovery of human CCR5 antagonists containing hydantoins for the treatment of HIV-1 infection.

A series of hydantoin derivatives has been discovered as highly potent nonpeptide antagonists for the human CCR5 receptor. The synthesis, SAR, and biological profiles of this class of antagonists are described.

1,3,4-Trisubstituted pyrrolidine CCR5 receptor antagonists. Part 2: lead optimization affording selective, orally bioavailable compounds with potent anti-HIV activity.

Investigations of the structure-activity relationships of 1,3,4-trisubstituted pyrrolidine human CCR5 receptor antagonists afforded orally bioavailable compounds with the ability to inhibit HIV replication in vitro.

Antagonists of the human CCR5 receptor as anti-HIV-1 agents. Part 3: a proposed pharmacophore model for 1-[N-(methyl)-N-(phenylsulfonyl)amino]-2-(phenyl)-4-[4-(substituted)piperidin-1-yl]butanes.

Structure-activity relationship studies directed toward the optimization of (2S)-2-(3-chlorophenyl)-1-[N-(methyl)-N-(phenylsulfonyl)amino]-4-[4-(substituted)piperidin-1-yl]butanes as CCR5 antagonists resulted in the synthesis of the spiro-indanone derivative 8c (IC50=5 nM). These and previous results are summarized in a proposed pharmacophore model for this class of CCR5 antagonist.

Antagonists of the human CCR5 receptor as anti-HIV-1 agents. Part 4: synthesis and structure-activity relationships for 1-[N-(methyl)-N-(phenylsulfonyl)amino]-2-(phenyl)-4-(4-(N-(alkyl)-N-(benzyloxycarbonyl)amino)piperidin-1-yl)butanes.

(2S)-2-(3-Chlorophenyl)-1-[N-(methyl)-N-(phenylsulfonyl)amino]-4-[spiro(2,3-dihydrobenzthiophene-3,4'-piperidin-1'-yl)]butane S-oxide (1b) has been identified as a potent CCR5 antagonist having an IC50=10 nM. Herein, structure-activity relationship studies of non-spiro piperidines are described, which led to the discovery of 4-(N-(alkyl)-N-(benzyloxycarbonyl)amino)piperidine derivatives (3-5) as potent CCR5 antagonists.

1,3,4-Trisubstituted pyrrolidine CCR5 receptor antagonists. Part 1: discovery of the pyrrolidine scaffold and determination of its stereochemical requirements.

A series of 1,3,4-trisubstituted pyrrolidines was discovered to have the ability to displace [(125)I]-MIP-1alpha from the CCR5 receptor expressed on Chinese hamster ovary (CHO) cell membranes. CCR5 activity was found to be dependent on the regiochemistry and the absolute stereochemistry of the pyrrolidine.

CCR5, CXCR4, and CD4 are clustered and closely apposed on microvilli of human macrophages and T cells.

The chemokine receptors CCR5 and CXCR4 act synergistically with CD4 in an ordered multistep mechanism to allow the binding and entry of human immunodeficiency virus type 1 (HIV-1). The efficiency of such a coordinated mechanism depends on the spatial distribution of the participating molecules on the cell surface. Immunoelectron microscopy was performed to address the subcellular localization of the chemokine receptors and CD4 at high resolution. Cells were fixed, cryoprocessed, and frozen; 80-nm cryosections were double labeled with combinations of CCR5, CXCR4, and CD4 antibodies and then stained with immunogold. Surprisingly, CCR5, CXCR4, and CD4 were found predominantly on microvilli and appeared to form homogeneous microclusters in all cell types examined, including macrophages and T cells. Further, while mixed microclusters were not observed, homogeneous microclusters of CD4 and the chemokine receptors were frequently separated by distances less than the diameter of an HIV-1 virion. Such distributions are likely to facilitate cooperative interactions with HIV-1 during virus adsorption to and penetration of human leukocytes and have significant implications for development of therapeutically useful inhibitors of the entry process. Although the mechanism underlying clustering is not understood, clusters were observed in small trans-Golgi vesicles, implying that they were organized shortly after synthesis and well before insertion into the cellular membrane. Chemokine receptors normally act as sensors, detecting concentration gradients of their ligands and thus providing directional information for cellular migration during both normal homeostasis and inflammatory responses. Localization of these sensors on the microvilli should enable more precise monitoring of their environment, improving efficiency of the chemotactic process. Moreover, since selectins, some integrins, and actin are also located on or in the microvillus, this organelle has many of the major elements required for chemotaxis.

Antagonists of the human CCR5 receptor as anti-HIV-1 agents. part 1: discovery and initial structure-activity relationships for 1 -amino-2-phenyl-4-(piperidin-1-yl)butanes.

Screening of the Merck sample collection for compounds with CCR5 receptor binding afforded (2S)-2-(3,4-dichlorophenyl)-1-[N-(methyl)-N-(phenylsulfonyl)amino]-4-[spiro(2,3-dihydrobenzthiophene-3,4'-piperidin-1'-yl)]butane S-oxide (4) as a potent lead structure having an IC50 binding affinity of 35 nM. Herein, we describe the discovery of this lead structure and our initial structure activity relationship studies directed toward the requirement for and optimization of the 1-amino fragment.

Antagonists of the human CCR5 receptor as anti-HIV-1 agents. Part 2: structure-activity relationships for substituted 2-Aryl-1-[N-(methyl)-N-(phenylsulfonyl)amino]-4-(piperidin-1-yl)butanes.

(2S)-2-(3,4-Dichlorophenyl)-1-[N-(methyl)-N-(phenylsulfonyl)amino]-4-[spiro(2,3-dihydrobenzthiophene-3,4'-piperidin-1'-yl)]butane S-oxide (3) has been identified as a potent CCR5 antagonist lead structure having an IC50 = 35 nM. Herein, we describe the structure-activity relationship studies directed toward the requirement for and optimization of the C-2 phenyl fragment. The phenyl was found to be important for CCR5 antagonism and substitution was limited to small moieties at the 3-position (13 and 16: X= H, 3-F, 3-Cl, 3-Me).

The CXCR4 agonist ligand stromal derived factor-1 maintains high affinity for receptors in both Galpha(i)-coupled and uncoupled states.

The alpha chemokine receptor CXCR4 and its only characterized chemokine ligand, stromal cell-derived factor-1 (SDF-1), are postulated to be important in the development of the B-cell arm of the immune system. In addition, CXCR4 is a critical coreceptor in support of viral entry by T-cell line tropic strains (X4) of the Human Immunodeficiency Virus Type 1 (HIV-1), viral variants which predominate in some infected individuals in end stage disease. SDF-1 can block X4-tropic HIV-1 infection of CD4+ target cells in vitro, and allelic variants of the human gene encoding SDF-1 in vivo correlate with delayed disease progression. Therefore, CXCR4 may be an appropriate target for therapeutic intervention in acquired immunodeficiency syndrome (AIDS), and knowledge of the pharmacology of SDF-1 binding to its cognate receptor will be important in the interpretation of these experiments. We report here a Kd derived using a competition binding assay of 4.5 nM for CXCR4 endogenously expressed on peripheral blood monocytes and T-cells. This affinity is similar to that which SDF-1 exhibits when binding to endogenous CXCR4 on an established immortal Jurkat T-cell line as well as recombinant CXCR4 transfected into Chinese Hamster Ovary (CHO) cells. We also demonstrate that the determined affinity of SDF-1 for CXCR4 is reflective of its ability to induce a CXCR4-mediated signal transduction in these different cell types. Furthermore, using Bordetella pertussis toxin, we observe that high affinity binding of SDF-1 to CXCR4 is independent of the G-protein coupled state of the receptor, as uncoupling of G-protein did not lead to the appearance of measurable low affinity SDF-1 binding sites. Moreover, binding affinity and receptor number were unaffected by uncoupling for both recombinant and endogenously expressed CXCR4. Thus, SDF-1 is novel among agonist ligands of G protein-coupled receptors in that it appears to have equal affinity for both the G protein-coupled and uncoupled states of CXCR4.

A critical site in the core of the CCR5 chemokine receptor required for binding and infectivity of human immunodeficiency virus type 1.

Like the CCR5 chemokine receptors of humans and rhesus macaques, the very homologous (approximately 98-99% identical) CCR5 of African green monkeys (AGMs) avidly binds beta-chemokines and functions as a coreceptor for simian immunodeficiency viruses. However, AGM CCR5 is a weak coreceptor for tested macrophage-tropic (R5) isolates of human immunodeficiency virus type 1 (HIV-1). Correspondingly, gp120 envelope glycoproteins derived from R5 isolates of HIV-1 bind poorly to AGM CCR5. We focused on a unique extracellular amino acid substitution at the juncture of transmembrane helix 4 (TM4) and extracellular loop 2 (ECL2) (Arg for Gly at amino acid 163 (G163R)) as the likely source of the weak R5 gp120 binding and HIV-1 coreceptor properties of AGM CCR5. Accordingly, a G163R mutant of human CCR5 was severely attenuated in its ability to bind R5 gp120s and to mediate infection by R5 HIV-1 isolates. Conversely, the R163G mutant of AGM CCR5 was substantially strengthened as a coreceptor for HIV-1 and had improved R5 gp120 binding affinity relative to the wild-type AGM CCR5. These substitutions at amino acid position 163 had no effect on chemokine binding or signal transduction, suggesting the absence of structural alterations. The 2D7 monoclonal antibody has been reported to bind to ECL2 and to block HIV-1 binding and infection. Whereas 2D7 antibody binding to CCR5 was unaffected by the G163R mutation, it was prevented by a conservative ECL2 substitution (K171R), shared between rhesus and AGM CCR5s. Thus, it appears that the 2D7 antibody binds to an epitope that includes Lys-171 and may block HIV-1 infection mediated by CCR5 by occluding an HIV-1-binding site in the vicinity of Gly-163. In summary, our results identify a site for gp120 interaction that is critical for R5 isolates of HIV-1 in the central core of human CCR5, and we propose that this site collaborates with a previously identified region in the CCR5 amino terminus to enable gp120 binding and HIV-1 infections.

The amino terminus of human CCR5 is required for its function as a receptor for diverse human and simian immunodeficiency virus envelope glycoproteins.

The chemokine receptor CCR5 plays a key role in the CD4-dependent entry of human and simian immunodeficiency viruses into target cells. We have mapped the interaction sites on CCR5 for a number of novel anti-CCR5 monoclonal antibodies and have used these to study the role of the CCR5 N-terminal ectodomain in viral entry and to demonstrate differential CCR5 epitope expression on different cell types. Deletions of the CCR5 amino terminal domain or substitution with equivalent regions from other chemokine receptors did not affect cell surface expression or reactivity with loop-specific antibodies, suggesting that the loop regions remained conformationally intact. Exchanges of the amino terminal segment of CCR5 with the equivalent domains of CCR1, CCR2, and CXCR4 did not significantly affect infection with virus pseudotyped with envelope glycoproteins (Envs) from HIV-2 and SIV, but substitution with the CXCR4 sequence abrogated entry mediated by Env from HIV-1. In contrast, deletion of the amino terminus abrogated CCR5 receptor activity for all viral Envs examined. These data indicate that the amino terminus of CCR5 has an essential role in entry mediated by diverse viral Envs but that the sequence requirements are more relaxed for the HIV-2 and SIV Envs compared to the HIV-1 Env examined. This suggests that different viral Envs make distinct and specific interactions with the amino terminus of CCR5. Viral Env utilization of CCR5 expressed on 293-T cells does not always correlate with the cellular tropism of the virus, and one possible explanation is that Env-accessible interaction sites on CCR5 differ on different cell types. We therefore analyzed binding of several anti-CCR5 monoclonal antibodies to cell lines and primary cells that express this chemokine receptor and found that whereas all antibodies bound to CCR5-transfected 293T cells, several did not bind to PBMC. The results suggest that CCR5 undergoes cell type specific structural modifications which may affect interaction with different HIV and SIV envelope glycoproteins.

Binding and functional properties of recombinant and endogenous CXCR3 chemokine receptors.

IP10 and MIG are two members of the CXC branch of the chemokine superfamily whose expression is dramatically up-regulated by interferon (IFN)-gamma. The proteins act largely on natural killer (NK)-cells and activated T-cells and have been implicated in mediating some of the effects of IFN-gamma and lipopolysaccharides (LPSs), as well as T-cell-dependent anti-tumor responses. Recently both chemokines have been shown to be functional agonists of the same G-protein-coupled receptor, CXCR3. We now report the pharmacological characterization of CXCR3 and find that, when heterologously expressed, CXCR3 binds IP10 and MIG with Ki values of 0.14 and 4.9 nM, respectively. The receptor has very modest affinity for SDF-1alpha and little or no affinity for other CXC-chemokines. The properties of the endogenous receptor expressed on activated T-cells are similar. Surprisingly, several CC-chemokines, particularly eotaxin and MCP-4, also compete with moderate affinity for the binding of IP10 to CXCR3. Eotaxin does not activate CXCR3 but, in CXCR3-transfected cells, can block IP10-mediated receptor activation. Eotaxin, therefore, may be a natural CXCR3 antagonist.

SCH 43478 and analogs: in vitro activity and in vivo efficacy of novel agents for herpesvirus type 2.

SCH 43478 and analogs are a class of non-nucleoside antiviral agents that have potent and selective activity against herpes simplex virus type 2 (HSV-2). The IC50 for these compounds in plaque reduction analysis using Vero cells ranges from 0.8 to 2.0 microg/ml. All compounds have a LC50 > 100 microg/ml in cytotoxicity analysis. Mechanism of action studies suggest that these molecules have an effect on the transactivation of viral immediate early (alpha) gene expression. Time of addition studies indicate that antiviral activity of these analogs is limited to the initial 2-3 h after infection and is not due to inhibition of viral adsorption or penetration. Analysis of HSV protein expression demonstrates that SCH 49286 inhibits the accumulation of viral immediate early (alpha) gene products. SCH 43478 demonstrates statistically significant efficacy (P < 0.05) in the guinea pig genital model of HSV infection. Following subcutaneous administration in a therapeutic treatment regimen, SCH 43478 (90 mg/kg/day) is efficacious in reducing the number and severity of lesions and the neurological complications of acute HSV infection. Thus, SCH 43478 and analogs are anti-herpesvirus agents with a unique mechanism of action.