Characterization of humoral and cellular immunologic responses to an mRNA-based human cytomegalovirus vaccine from a phase 1 trial of healthy adults.

mRNA-1647 is an investigational mRNA-based vaccine against cytomegalovirus (CMV) that contains sequences encoding the CMV proteins glycoprotein B and pentamer. Humoral and cellular immune responses were evaluated in blood samples collected from healthy CMV-seropositive and CMV-seronegative adults who participated in a phase 1 trial of a three-dose series of mRNA-1647 (NCT03382405). Neutralizing antibody (nAb) titers against fibroblast and epithelial cell infection in sera from CMV-seronegative mRNA-1647 recipients were higher than those in sera from control CMV-seropositive samples and remained elevated up to 12 months after dose 3. nAb responses elicited by mRNA-1647 were comparable across 14 human CMV (HCMV) strains. Frequencies of antigen-specific memory B cells increased in CMV-seropositive and CMV-seronegative participants after each mRNA-1647 dose and remained elevated for up to 6 months after dose 3. mRNA-1647 elicited robust increases in frequencies and polyfunctionality of CD4+ T helper type 1 and effector CD8+ T cells in samples from CMV-seronegative and CMV-seropositive participants after stimulation with HCMV-specific peptides. The administration of three doses of mRNA-1647 to healthy adults elicited high nAb titers with wide-breadth, long-lasting memory B cells, and strong polyfunctional T-cell responses. These findings support further clinical development of the mRNA-1647 vaccine against CMV.IMPORTANCECytomegalovirus (CMV), a common virus that can infect people of all ages, may lead to serious health problems in unborn babies and those with a weakened immune system. Currently, there is no approved vaccine available to prevent CMV infection; however, the investigational messenger RNA (mRNA)-based CMV vaccine, mRNA-1647, is undergoing evaluation in clinical trials. The current analysis examined samples from a phase 1 trial of mRNA-1647 in healthy adults to better understand how the immune system reacts to vaccination. Three doses of mRNA-1647 produced a long-lasting immune response, thus supporting further investigation of the vaccine in the prevention of CMV infection.CLINICAL TRIALSRegistered at ClinicalTrials.gov (NCT03382405).

Role of Cholesterol and its Biosynthetic Precursors on Membrane Organization and Dynamics: A Fluorescence Approach.

Cholesterol is the most representative sterol present in membranes of higher eukaryotes, and is the end product of a long and multistep biosynthetic pathway. Lathosterol and zymosterol are biosynthetic precursors of cholesterol in Kandutsch-Russell and Bloch pathways, respectively. Lathosterol differs with cholesterol merely in the position of the double bond in the sterol ring, whereas zymosterol differs with cholesterol in position and number of double bonds. In this work, we have monitored the effect of cholesterol and its biosynthetic precursors (lathosterol and zymosterol) on membrane organization and dynamics in fluid and gel phase membranes. Toward this goal, we have utilized two fluorescent membrane probes, DPH and its cationic derivative TMA-DPH. Our results using these probes show that cholesterol and its biosynthetic precursors (lathosterol and zymosterol) exhibit similar trend in maintaining membrane organization and dynamics (as reported by fluorescence anisotropy and apparent rotational correlation time), in fluid phase POPC membranes. Notably, although lathosterol and zymosterol show similar trend in maintaining membrane organization and dynamics, the corresponding change for cholesterol is different in gel phase DPPC membranes. These results demonstrate that the position and number of double bonds in sterols is an important determinant in maintaining membrane physical properties. Our results assume significance since accumulation of precursors of cholesterol have been reported to be associated with severe pathological conditions.

Humoral Immunogenicity of the mRNA-1273 Vaccine in the Phase 3 Coronavirus Efficacy (COVE) Trial.

BACKGROUND: Messenger RNA (mRNA)-1273 vaccine demonstrated 93.2% efficacy against coronavirus disease 2019 (COVID-19) in the Coronavirus Efficacy (COVE) trial. The humoral immunogenicity results are now reported. METHODS: Participants received 2 mRNA-1273 (100 µg) or placebo injections, 28 days apart. Immune responses were evaluated in a prespecified, randomly selected per-protocol immunogenicity population (n = 272 placebo; n = 1185 mRNA-1273). Serum binding antibodies (bAbs) and neutralizing antibodies (nAbs) to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-spike protein were assessed at days 1, 29, and 57 by baseline SARS-CoV-2-negative (n = 1197) and SARS-CoV-2-positive (n = 260) status, age, and sex. RESULTS: SARS-CoV-2-negative vaccinees had bAb geometric mean AU/mL levels of 35 753 at day 29 that increased to 316 448 at day 57 and nAb inhibitory dilution 50% titers of 55 at day 29 that rose to 1081 at day 57. In SARS-CoV-2-positive vacinees, the first mRNA-1273 injection elicited bAb and nAb levels that were 11-fold (410 049) and 27-fold (1479) higher than in SARS-CoV-2-negative vaccinees, respectively, and were comparable to levels after 2 injections in uninfected participants. Findings were generally consistent by age and sex. CONCLUSIONS: mRNA-1273 elicited robust serologic immune responses across age, sex, and SARS-CoV-2 status, consistent with its high COVID-19 efficacy. Higher immune responses in those previously infected support a booster-type effect. Clinical Trials Registration. NCT04470427.

The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts.

Protein trafficking across membranes is an essential function in cells; however, the exact mechanism for how this occurs is not well understood. In the endosymbionts, mitochondria and chloroplasts, the vast majority of proteins are synthesized in the cytoplasm as preproteins and then imported into the organelles via specialized machineries. In chloroplasts, protein import is accomplished by the TOC (translocon on the outer chloroplast membrane) and TIC (translocon on the inner chloroplast membrane) machineries in the outer and inner envelope membranes, respectively. TOC mediates initial recognition of preproteins at the outer membrane and includes a core membrane channel, Toc75, and two receptor proteins, Toc33/34 and Toc159, each containing GTPase domains that control preprotein binding and translocation. Toc75 is predicted to have a ß-barrel fold consisting of an N-terminal intermembrane space (IMS) domain and a C-terminal 16-stranded ß-barrel domain. Here we report the crystal structure of the N-terminal IMS domain of Toc75 from Arabidopsis thaliana, revealing three tandem polypeptide transport-associated (POTRA) domains, with POTRA2 containing an additional elongated helix not observed previously in other POTRA domains. Functional studies show an interaction with the preprotein, preSSU, which is mediated through POTRA2-3. POTRA2-3 also was found to have chaperone-like activity in an insulin aggregation assay, which we propose facilitates preprotein import. Our data suggest a model in which the POTRA domains serve as a binding site for the preprotein as it emerges from the Toc75 channel and provide a chaperone-like activity to prevent misfolding or aggregation as the preprotein traverses the intermembrane space.

Interim analysis of a phase 1 randomized clinical trial on the safety and immunogenicity of the mRNA-1283 SARS-CoV-2 vaccine in adults.

This interim analysis of an ongoing phase 1 randomized clinical trial evaluated the safety, reactogenicity, and immunogenicity of mRNA-1283, a next-generation SARS-CoV-2 messenger RNA (mRNA)-based vaccine encoding two segments of the spike protein (i.e. receptor binding and N-terminal domains). Healthy adults aged 18-55 years (n = 104) were randomized (1:1:1:1:1) to receive two doses of mRNA-1283 (10, 30, or 100 µg) or mRNA-1273 (100 µg) administered 28 days apart, or a single dose of mRNA-1283 (100 µg). Safety was assessed and immunogenicity was measured by serum neutralizing antibody (nAb) or binding antibody (bAb) responses. At the interim analysis, no safety concerns were identified and no serious adverse events, adverse events of special interest, or deaths were reported. Solicited systemic adverse reactions were more frequent with higher dose levels of mRNA-1283 than with mRNA-1273. At day 57, all dose levels of the 2-dose mRNA-1283 regimen (including the lowest dose level [10 µg]) induced robust nAb and bAb responses that were comparable to those of mRNA-1273 (100 µg). mRNA-1283 was generally safe in adults, with all dose levels of the 2-dose regimen (10, 30, and 100 µg) eliciting similar immunogenicity as the 2-dose mRNA-1273 regimen (100 µg).Clinical Trials Registration: Clinicaltrials.gov, NCT04813796.

The safety and immunogenicity of two Zika virus mRNA vaccine candidates in healthy flavivirus baseline seropositive and seronegative adults: the results of two randomised, placebo-controlled, dose-ranging, phase 1 clinical trials.

BACKGROUND: Developing a safe and immunogenic vaccine against Zika virus remains an unmet medical need. We did two phase 1 studies that evaluated the safety and immunogenicity of two mRNA-based Zika virus vaccines (mRNA-1325 and mRNA-1893) in adults. METHODS: Two randomised, placebo-controlled, dose-ranging, multicentre, phase 1 trials, one of mRNA-1325 (mRNA-1325 trial) and one of mRNA-1893 (mRNA-1893 trial), were done. For both studies, eligible participants were healthy adults (aged 18-49 years) who were flavivirus seronegative or flavivirus seropositive at baseline. Participants in the mRNA-1325 trial, which was done at three centres in the USA, were randomly assigned centrally (1:4), using a randomisation table, to the placebo group or one of three mRNA-1325 dose groups (10, 25, or 100 µg). All participants received two doses. The mRNA-1325 vaccine encoded the premembrane and envelope E structural proteins (prME) from a Micronesia 2007 Zika virus isolate. Participants in the mRNA-1893 trial, which was done at three centres in the USA and one centre in Puerto Rico, were randomly assigned (1:4) to the placebo group or one of four mRNA-1893 dose groups (10, 30, 100, or 250 µg) using centralised interactive response technology. All participants in the mRNA-1893 trial received dose one on day 1 and then dose two on day 29. The mRNA-1893 vaccine encoded the prME from the RIO-U1 Zika virus isolate. Safety was the primary outcome of each study, which was evaluated in the respective safety populations (mRNA-1325 trial: participants who received at least one dose and provided safety data; mRNA-1893 trial: participants who received at least one dose) and the solicited safety population (mRNA-1893 trial only: received at least 1 dose and contributed solicited adverse reaction data). Endpoints in both trials included solicited adverse reactions within 7 days after vaccination and unsolicited adverse events within 28 days after vaccination. The secondary outcome of both trials was immunogenicity assessed by Zika virus-specific neutralising antibodies (nAbs) in the per-protocol populations in either trial (participants with no major protocol deviations received full dose[s] of assigned dose level within the acceptable time window, had samples drawn within acceptable time window, and had prevaccination and corresponding post-vaccination serum samples for testing). These were descriptive studies, with no formal hypothesis testing in either trial. Both trials are registered with ClinicalTrials.gov, NCT03014089 (mRNA-1325 trial) and NCT04064905 (mRNA-1893 trial). FINDINGS: The mRNA-1325 trial was done from Dec 14, 2016, to Aug 16, 2018. 90 participants were enrolled: 53 (59%) participants were women and 37 (41%) were men; 84 (93%) were White; and 74 (82%) were not Hispanic or Latino. All three dose levels of mRNA-1325 (10, 25, and 100 µg) were generally well tolerated, but the vaccine elicited poor Zika virus-specific nAb responses. At 28 days after dose two, geometric mean titres (GMTs) were highest for mRNA-1325 10 µg (10·3 [95% CI 5·9-18·2]). The mRNA-1893 trial was done from July 23, 2019, to March 22, 2021. 120 participants (70 [58%] women and 50 [42%] men) were enrolled, most participants were White (89 [74%]), and not Hispanic or Latino (91 [76%]). In the mRNA-1893 trial, solicited adverse reactions in participants who received a vaccine were mostly grade 1 or 2 and occurred more frequently at higher dose levels and after dose two. No participants withdrew due to an unsolicited treatment-emergent adverse event and most of these events were not treatment related. On day 57, all evaluated mRNA-1893 dose levels induced robust Zika virus-specific nAb responses, independent of flavivirus serostatus, that persisted until month 13. At day 57 in participants who were flavivirus seronegative, plaque reduction neutralisation titre test nAb GMTs were highest for mRNA-1893 100 µg (454·2 [330·0-619·6]); in participants who were flavivirus seropositive, GMTs were highest for mRNA-1893 10 µg (224·1 [43·5-1153·5]) and mRNA-1893 100 µg (190·5 [19·2-1887·2]). INTERPRETATION: These findings support the continued development of mRNA-1893 against Zika virus, which was well tolerated at all evaluated dose levels and induced strong Zika virus-specific serum nAb responses after two doses, regardless of baseline flavivirus serostatus. FUNDING: Biomedical Advanced Research and Development Authority and Moderna.

Effectiveness of mRNA-1273 vaccination against SARS-CoV-2 omicron subvariants BA.1, BA.2, BA.2.12.1, BA.4, and BA.5.

Studies have reported reduced natural SARS-CoV-2 infection- and vaccine-induced neutralization against omicron BA.4/BA.5 compared with earlier omicron subvariants. This test-negative case-control study evaluates mRNA-1273 vaccine effectiveness (VE) against infection and hospitalization with omicron subvariants. The study includes 30,809 SARS-CoV-2 positive and 92,427 SARS-CoV-2 negative individuals aged ≥18 years tested during 1/1/2022-6/30/2022. While 3-dose VE against BA.1 infection is high and wanes slowly, VE against BA.2, BA.2.12.1, BA.4, and BA.5 infection is initially moderate to high (61.0%-90.6% 14-30 days post third dose) and wanes rapidly. The 4-dose VE against infection with BA.2, BA.2.12.1, and BA.4 ranges between 64.3%-75.7%, and is low (30.8%) against BA.5 14-30 days post fourth dose, disappearing beyond 90 days for all subvariants. The 3-dose VE against hospitalization for BA.1, BA.2, and BA.4/BA.5 is 97.5%, 82.0%, and 72.4%, respectively; 4-dose VE against hospitalization for BA.4/BA.5 is 88.5%. Evaluation of the updated bivalent booster is warranted.

Desmosterol replaces cholesterol for ligand binding function of the serotonin(1A) receptor in solubilized hippocampal membranes: support for nonannular binding sites for cholesterol?

The serotonin(1A) receptor is an important member of the G-protein coupled receptor family, and is involved in the generation and modulation of a variety of cognitive and behavioral functions. Solubilization of the hippocampal serotonin(1A) receptor by CHAPS is accompanied by loss of cholesterol that results in a reduction in specific agonist binding activity. Replenishment of cholesterol to solubilized membranes restores membrane cholesterol content and significantly recovers specific agonist binding. In order to test the stringency of cholesterol requirement, we solubilized native hippocampal membranes followed by replenishment with desmosterol. Desmosterol is the immediate biosynthetic precursor of cholesterol in the Bloch pathway differing only in a double bond at the 24th position. Our results show that replenishment with desmosterol restores ligand binding of serotonin(1A) receptors. This is consistent with earlier results showing that desmosterol can replace cholesterol in a large number of cases. However, these results appear to be contradictory to our earlier findings, performed by sterol manipulation utilizing methyl-ß-cyclodextrin, in which we observed that replacing cholesterol with desmosterol is unable to restore specific ligand binding of the hippocampal serotonin(1A) receptor. We discuss the possible molecular mechanism, in terms of nonannular lipid binding sites around the receptor, giving rise to these differences.

Cholesterol depletion enhances adrenergic signaling in cardiac myocytes.

Cardiac myocytes endogenously express α and ß adrenergic receptors, prototypes of the G-protein coupled receptor superfamily. Depending upon the dose of norepinephrine (agonist) exposure, hypertrophy and apoptosis are initiated by differential induction of two discrete constituents of the transcription factor AP-1, i.e., FosB and Fra-1. We explored differential adrenergic signaling as a paradigm for understanding how cholesterol dictates cells to choose hypertrophy or apoptosis. For this, we used fosB and fra-1 promoter-reporter constructs for monitoring adrenergic signaling. We show that cholesterol depletion enhances norepinephrine-mediated signaling in cardiac myocytes. Importantly, this increased signaling is reduced to original level upon cholesterol replenishment. We used specific ligands for α and ß adrenergic receptors and show that the enhanced signaling upon cholesterol depletion is a combined effect of both α and ß adrenergic receptors. These results constitute the first report demonstrating the effect of cholesterol on adrenergic signaling using a direct end-point gene expression.

Role of glycosphingolipids in the function of human serotonin1A receptors.

Glycosphingolipids are essential components of eukaryotic cell membranes and are involved in the regulation of cell growth, differentiation, and neoplastic transformation. In this work, we have modulated glycosphingolipid levels in CHO cells stably expressing the human serotonin(1A) receptor by inhibiting the activity of glucosylceramide synthase using (±)-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), a commonly used inhibitor of the enzyme. Serotonin(1A) receptors belong to the family of G-protein-coupled receptors and are implicated in the generation and modulation of various cognitive, behavioral, and developmental functions. We explored the function of the serotonin(1A) receptor under glycosphingolipid-depleted condition by monitoring ligand-binding activity and G-protein coupling of the receptor. Our results show that ligand binding of the receptor is impaired under these conditions although the efficiency of G-protein coupling remains unaltered. The expression of the receptor at the cell membrane appears to be reduced. Interestingly, our results show that the effect of glycosphingolipids on ligand binding caused by metabolic depletion of these lipids is reversible. These novel results demonstrate that glycosphingolipids are necessary for the function of the serotonin(1A) receptor. We discuss possible mechanisms of specific interaction of glycosphingolipids with the serotonin(1A) receptor that could involve the proposed 'sphingolipid-binding domain'.

Initial analysis of viral dynamics and circulating viral variants during the mRNA-1273 Phase 3 COVE trial.

The mRNA-1273 vaccine for coronavirus disease 2019 (COVID-19) demonstrated 93.2% efficacy in reduction of symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in the blinded portion of the Phase 3 Coronavirus Efficacy (COVE) trial. While mRNA-1273 demonstrated high efficacy in prevention of COVID-19, including severe disease, its effect on the viral dynamics of SARS-CoV-2 infections is not understood. Here, in exploratory analyses, we assessed the impact of mRNA-1273 vaccination in the ongoing COVE trial (number NCT04470427) on SARS-CoV-2 copy number and shedding, burden of disease and infection, and viral variants. Viral variants were sequenced in all COVID-19 and adjudicated COVID-19 cases (n = 832), from July 2020 in the blinded part A of the study to May 2021 of the open-label part B of the study, in which participants in the placebo arm started to receive the mRNA-1273 vaccine after US Food and Drug Administration emergency use authorization of mRNA-1273 in December 2020. mRNA-1273 vaccination significantly reduced SARS-CoV-2 viral copy number (95% confidence interval) by 100-fold on the day of diagnosis compared with placebo (4.1 (3.4-4.8) versus 6.2 (6.0-6.4) log10 copies per ml). Median times to undetectable viral copies were 4 days for mRNA-1273 and 7 days for placebo. Vaccination also substantially reduced the burden of disease and infection scores. Vaccine efficacies (95% confidence interval) against SARS-CoV-2 variants circulating in the United States during the trial assessed in this post hoc analysis were 82.4% (40.4-94.8%) for variants Epsilon and Gamma and 81.2% (36.1-94.5%) for Epsilon. The detection of other, non-SARS-CoV-2, respiratory viruses during the trial was similar between groups. While additional study is needed, these data show that in SARS-CoV-2-infected individuals, vaccination reduced both the viral copy number and duration of detectable viral RNA, which may be markers for the risk of virus transmission.

Metabolic depletion of sphingolipids enhances the mobility of the human serotonin1A receptor.

Sphingolipids are essential components of eukaryotic cell membranes. We recently showed that the function of the serotonin(1A) receptor is impaired upon metabolic depletion of sphingolipids using fumonisin B(1) (FB(1)), a specific inhibitor of ceramide synthase. Serotonin(1A) receptors belong to the family of G-protein coupled receptors and are implicated in the generation and modulation of various cognitive, behavioral and developmental functions. Since function and dynamics of membrane receptors are often coupled, we monitored the lateral dynamics of the serotonin(1A) receptor utilizing fluorescence recovery after photobleaching (FRAP) under these conditions. Our results show an increase in mobile fraction of the receptor upon sphingolipid depletion, while the diffusion coefficient of the receptor did not exhibit any significant change. These novel results constitute the first report on the effect of sphingolipid depletion on the mobility of the serotonin(1A) receptor. Our results assume greater relevance in the broader context of the emerging role of receptor mobility in understanding cellular signaling.

Membrane cholesterol in the function and organization of G-protein coupled receptors.

Cholesterol is an essential component of higher eukaryotic membranes and plays a crucial role in membrane organization, dynamics and function. The G-protein coupled receptors (GPCRs) are the largest class of molecules involved in signal transduction across membranes, and represent major targets in the development of novel drug candidates in all clinical areas. Membrane cholesterol has been reported to have a modulatory role in the function of a number of GPCRs. Two possible mechanisms have been previously suggested by which membrane cholesterol could influence the structure and function of GPCRs (i) through a direct/specific interaction with GPCRs, or (ii) through an indirect way by altering membrane physical properties in which the receptor is embedded, or due to a combination of both. Recently reported crystal structures of GPCRs have shown structural evidence of cholesterol binding sites. Against this backdrop, we recently proposed a novel mechanism by which membrane cholesterol could affect structure and function of GPCRs. According to our hypothesis, cholesterol binding sites in GPCRs could represent 'nonannular' binding sites. Interestingly, previous work from our laboratory has demonstrated that membrane cholesterol is required for the function of the serotonin(1A) receptor (a representative GPCR), which could be due to specific interaction of the receptor with cholesterol. Based on these results, we envisage that there could be specific/nonannular cholesterol binding site(s) in the serotonin(1A) receptor. We have analyzed putative cholesterol binding sites from protein databases in the serotonin(1A) receptor. Our analysis shows that cholesterol binding sites are inherent characteristic features of serotonin(1A) receptors and are conserved through natural evolution. Progress in deciphering molecular details of the GPCR-cholesterol interaction in the membrane would lead to better insight into our overall understanding of GPCR function in health and disease, thereby enhancing our ability to design better therapeutic strategies to combat diseases related to malfunctioning of GPCRs.

Effectiveness of mRNA-1273 against delta, mu, and other emerging variants of SARS-CoV-2: test negative case-control study.

OBJECTIVES: To evaluate the effectiveness of the mRNA-1273 vaccine against SARS-CoV-2 variants and assess its effectiveness against the delta variant by time since vaccination. DESIGN: Test negative case-control study. SETTING: Kaiser Permanente Southern California (KPSC), an integrated healthcare system. PARTICIPANTS: Adult KPSC members with a SARS-CoV-2 positive test sent for whole genome sequencing or a negative test from 1 March 2021 to 27 July 2021. INTERVENTIONS: Two dose or one dose vaccination with mRNA-1273 (Moderna covid-19 vaccine) ≥14 days before specimen collection versus no covid-19 vaccination. MAIN OUTCOME MEASURES: Outcomes included infection with SARS-CoV-2 and hospital admission with covid-19. In pre-specified analyses for each variant type, test positive cases were matched 1:5 to test negative controls on age, sex, race/ethnicity, and specimen collection date. Conditional logistic regression was used to compare odds of vaccination among cases versus controls, with adjustment for confounders. Vaccine effectiveness was calculated as (1-odds ratio)×100%. RESULTS: The study included 8153 cases and their matched controls. Two dose vaccine effectiveness was 86.7% (95% confidence interval 84.3% to 88.7%) against infection with the delta variant, 98.4% (96.9% to 99.1%) against alpha, 90.4% (73.9% to 96.5%) against mu, 96-98% against other identified variants, and 79.9% (76.9% to 82.5%) against unidentified variants (that is, specimens that failed sequencing). Vaccine effectiveness against hospital admission with the delta variant was 97.5% (92.7% to 99.2%). Vaccine effectiveness against infection with the delta variant declined from 94.1% (90.5% to 96.3%) 14-60 days after vaccination to 80.0% (70.2% to 86.6%) 151-180 days after vaccination. Waning was less pronounced for non-delta variants. Vaccine effectiveness against delta infection was lower among people aged ≥65 years (75.2%, 59.6% to 84.8%) than those aged 18-64 years (87.9%, 85.5% to 89.9%). One dose vaccine effectiveness was 77.0% (60.7% to 86.5%) against infection with delta. CONCLUSIONS: Two doses of mRNA-1273 were highly effective against all SARS-CoV-2 variants, especially against hospital admission with covid-19. However, vaccine effectiveness against infection with the delta variant moderately declined with increasing time since vaccination.

Covid-19 in the Phase 3 Trial of mRNA-1273 During the Delta-variant Surge.

BACKGROUND: Following emergency use authorization in December 2020, the Coronavirus Efficacy (COVE) trial was amended to an open-label phase, where participants were unblinded and those randomized to placebo were offered vaccination. Emergence of the delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been associated with increased incidences of coronavirus disease 2019 (Covid-19) among unvaccinated and vaccinated persons. This exploratory analysis evaluated the incidence and genetic sequences of Covid-19 cases in the ongoing COVE trial during the open-label phase, with a focus on July-August 2021, when delta-variants surged in the US. METHODS: Covid-19 cases were identified in participants initially randomized to mRNA-1273 (vaccinated from July-December 2020) and those initially randomized to the placebo (vaccinated December 2020-April 2021) who received at least one dose and were SARS-CoV-2-negative at baseline in the modified-intent-to-treat population were analyzed. Included were Covid-19 cases occurring after 26-Mar-2021 with positive RT-PCR results in nasopharyngeal samples (central lab test) and reported Covid-19 symptoms. Genetic sequencing of Covid-19 cases was also performed. RESULTS: There were 14,746 participants in the earlier mRNA-1273 (mRNA-1273e) group and 11,431 in the later placebo-mRNA1273 (mRNA-1273p) group. Covid-19 cases increased from the start of the open-label phase to July-August 2021. During July and August, 162 Covid-19 cases occurred in the mRNA-1273e group and 88 in the mRNA-1273p group. Of the cases sequenced, 144/149 [97%]) in the mRNA-1273 and 86/88 (99%) in the mRNA-1273p groups were attributed to delta. The incidence rate of Covid-19 was lower for the mRNA-1273p (49.0/1000 person-years) versus mRNA-1273e (77.1/1000 person-years) group [36.4% (95% CI 17.1%-51.5%) reduction]. There were fewer severe Covid-19 cases in the mRNA-1273p (6; 6.2/1000 person-years) than mRNA-1273e (13; 3.3/1000 person-years) [46.0% (95% CI -52.4%-83.2%) reduction]. Three Covid-19 related hospitalizations occurred with two resulting deaths in the mRNA-1273e group. CONCLUSION: Incidence rates of Covid-19 and severe Covid-19 were lower during the months when delta was the dominant variant (July/August 2021) among COVE participants vaccinated more recently. Analysis of COVID-19 cases from the open-label phase of the COVE study is ongoing.

Safety and immunogenicity of SARS-CoV-2 variant mRNA vaccine boosters in healthy adults: an interim analysis.

The emergence of SARS-CoV-2 variants of concern (VOCs) and variants of interest (VOIs) with decreased susceptibility to neutralization has generated interest in assessments of booster doses and variant-specific vaccines. Clinical trial participants who received a two-dose primary series of the COVID-19 vaccine mRNA-1273 approximately 6 months earlier entered an open-label phase 2a study ( NCT04405076 ) to evaluate the primary objectives of safety and immunogenicity of a single booster dose of mRNA-1273 or variant-modified mRNAs, including multivalent mRNA-1273.211. As the trial is currently ongoing, this exploratory interim analysis includes preliminary descriptive results only of four booster groups (n = 20 per group). Immediately before the booster dose, neutralizing antibodies against wild-type D614G virus had waned (P < 0.0001) relative to peak titers against wild-type D614G measured 1 month after the primary series, and neutralization titers against B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta) VOCs were either low or undetectable. Both the mRNA-1273 booster and variant-modified boosters were safe and well-tolerated. All boosters, including mRNA-1273, numerically increased neutralization titers against the wild-type D614G virus compared to peak titers against wild-type D614G measured 1 month after the primary series; significant increases were observed for mRNA-1273 and mRNA-1273.211 (P < 0.0001). In addition, all boosters increased neutralization titers against key VOCs and VOIs, including B.1.351, P.1. and B.1.617.2, that were statistically equivalent to peak titers measured after the primary vaccine series against wild-type D614G virus, with superior titers against some VOIs. This trial is ongoing.

Metabolic depletion of sphingolipids impairs ligand binding and signaling of human serotonin1A receptors.

Sphingolipids are essential components of eukaryotic cell membranes and are thought to be involved in a variety of cellular functions. Mycotoxins such as fumonisins can disrupt sphingolipid metabolism, and treatment with fumonisins represents an efficient approach to modulate cellular sphingolipid levels. In this work, we modulated sphingolipid levels in CHO cells stably expressing the human serotonin(1A) receptor by metabolically inhibiting the biosynthesis of sphingolipids using fumonisin B(1). Serotonin(1A) receptors belong to the family of seven-transmembrane domain receptors that couple to G-proteins and are implicated in the generation and modulation of various cognitive, behavioral, and developmental functions. We explored the function of serotonin(1A) receptors under sphingolipid-depleted conditions by monitoring ligand binding, G-protein coupling, and downstream signaling of the receptor. Importantly, our results show that the function of the serotonin(1A) receptor is impaired upon metabolic depletion of sphingolipids, although the membrane receptor level does not exhibit any reduction. Interestingly, we find that the replenishment of sphingolipids using sphingosine results in restoration of ligand binding of serotonin(1A) receptors, demonstrating that the loss of ligand binding due to metabolic depletion of sphingolipids is reversible. These novel results demonstrate that sphingolipids are necessary for ligand binding and downstream signaling of the human serotonin(1A) receptor. We discuss possible mechanisms of specific interaction of sphingolipids with the serotonin(1A) receptor that could involve the proposed "sphingolipid-binding domain" (SBD).

Chronic cholesterol depletion using statin impairs the function and dynamics of human serotonin(1A) receptors.

Statins are potent inhibitors of HMG-CoA reductase, the key rate-limiting enzyme in cholesterol biosynthesis, and are some of the best selling drugs globally. We have explored the effect of chronic cholesterol depletion induced by mevastatin on the function of human serotonin(1A) receptors expressed in CHO cells. An advantage with statins is that cholesterol depletion is chronic which mimics physiological conditions. Our results show a significant reduction in the level of specific ligand binding and G-protein coupling to serotonin(1A) receptors upon chronic cholesterol depletion, although the membrane receptor level is not reduced at all. Interestingly, replenishment of mevastatin-treated cells with cholesterol resulted in the recovery of specific ligand binding and G-protein coupling. Treatment of cells expressing serotonin(1A) receptors with mevastatin led to a decrease in the diffusion coefficient and an increase in the mobile fraction of the receptor, as determined by fluorescence recovery after photobleaching measurements. To the best of our knowledge, these results constitute the first report describing the effect of chronic cholesterol depletion on the organization and function of a G-protein-coupled neuronal receptor. Our results assume significance in view of recent reports highlighting the symptoms of anxiety and depression in humans upon statin administration, and the role of serotonin(1A) receptors in anxiety and depression.

Are specific nonannular cholesterol binding sites present in G-protein coupled receptors?

The G-protein coupled receptors (GPCRs) are the largest class of molecules involved in signal transduction across membranes, and represent major drug targets in all clinical areas. Membrane cholesterol has been reported to have a modulatory role in the function of a number of GPCRs. Interestingly, recently reported crystal structures of GPCRs have shown structural evidence of cholesterol binding sites. Two possible mechanisms have been previously suggested by which membrane cholesterol could influence the structure and function of GPCRs (i) through a direct/specific interaction with GPCRs, which could induce a conformational change in the receptor, or (ii) through an indirect way by altering the membrane physical properties in which the receptor is embedded or due to a combination of both. We discuss here a novel mechanism by which membrane cholesterol could affect structure and function of GPCRs and propose that cholesterol binding sites in GPCRs could represent 'nonannular' binding sites. Interestingly, previous work from our laboratory has demonstrated that membrane cholesterol is required for the function of the serotonin1A receptor, which could be due to specific interaction of the receptor with cholesterol. Based on these results, we envisage that there could be specific/nonannular cholesterol binding site(s) in the serotonin1A receptor. We have analyzed putative cholesterol binding sites from protein databases in the serotonin1A receptor, a representative GPCR, for which we have previously demonstrated specific requirement of membrane cholesterol for receptor function. Our analysis shows that cholesterol binding sites are inherent characteristic features of serotonin1A receptors and are conserved over evolution. Progress in deciphering molecular details of the nature of GPCR-cholesterol interaction in the membrane would lead to better insight into our overall understanding of GPCR function in health and disease, thereby enhancing our ability to design better therapeutic strategies to combat diseases related to malfunctioning of GPCRs.