Plitidepsin as an Immunomodulator against Respiratory Viral Infections.

Plitidepsin is a host-targeted compound known for inducing a strong anti-SARS-CoV-2 activity, as well as for having the capacity of reducing lung inflammation. Because IL-6 is one of the main cytokines involved in acute respiratory distress syndrome, the effect of plitidepsin in IL-6 secretion in different in vitro and in vivo experimental models was studied. A strong plitidepsin-mediated reduction of IL-6 was found in human monocyte-derived macrophages exposed to nonproductive SARS-CoV-2. In resiquimod (a ligand of TLR7/8)-stimulated THP1 human monocytes, plitidepsin-mediated reductions of IL-6 mRNA and IL-6 levels were also noticed. Additionally, although resiquimod-induced binding to DNA of NF-κB family members was unaffected by plitidepsin, a decrease in the regulated transcription by NF-κB (a key transcription factor involved in the inflammatory cascade) was observed. Furthermore, the phosphorylation of p65 that is required for full transcriptional NF-κB activity was significantly reduced by plitidepsin. Moreover, decreases of IL-6 levels and other proinflammatory cytokines were also seen in either SARS-CoV-2 or H1N1 influenza virus-infected mice, which were treated at low enough plitidepsin doses to not induce antiviral effects. In summary, plitidepsin is a promising therapeutic agent for the treatment of viral infections, not only because of its host-targeted antiviral effect, but also for its immunomodulatory effect, both of which were evidenced in vitro and in vivo by the decrease of proinflammatory cytokines.

Cyanovirin-N binds to select SARS-CoV-2 spike oligosaccharides outside of the receptor binding domain and blocks infection by SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an enveloped positive stranded RNA virus which has caused the recent deadly pandemic called COVID-19. The SARS-CoV-2 virion is coated with a heavily glycosylated Spike glycoprotein which is responsible for attachment and entry into target cells. One, as yet unexploited strategy for preventing SARS-CoV-2 infections, is the targeting of the glycans on Spike. Lectins are carbohydrate-binding proteins produced by plants, algae, and cyanobacteria. Some lectins can neutralize enveloped viruses displaying external glycoproteins, offering an alternative therapeutic approach for the prevention of infection with virulent ß-coronaviruses, such as SARS-CoV-2. Here we show that the cyanobacterial lectin cyanovirin-N (CV-N) can selectively target SARS-CoV-2 Spike oligosaccharides and inhibit SARS-CoV-2 infection in vitro and in vivo. CV-N neutralizes Delta and Omicron variants in vitro better than earlier circulating viral variants. CV-N binds selectively to Spike with a Kd as low as 15 nM and a stoichiometry of 2 CV-N: 1 Spike but does not bind to the receptor binding domain (RBD). Further mapping of CV-N binding sites on Spike shows that select high-mannose oligosaccharides in the S1 domain of Spike are targeted by CV-N. CV-N also reduced viral loads in the nares and lungs in vivo to protect hamsters against a lethal viral challenge. In summary, we present an anti-coronavirus agent that works by an unexploited mechanism and prevents infection by a broad range of SARS-CoV-2 strains.

Long-Term Evolution of the Adaptive NKG2C+ NK Cell Response to Cytomegalovirus Infection in Kidney Transplantation: An Insight on the Diversity of Host-Pathogen Interaction.

Human CMV infection is frequent in kidney transplant recipients (KTR). Pretransplant Ag-specific T cells and adaptive NKG2C+ NK cells associate with reduced incidence of infection in CMV+ KTR. Expansions of adaptive NKG2C+ NK cells were reported in posttransplant CMV-infected KTR. To further explore this issue, NKG2C+ NK, CD8+, and TcRγδ T cells were analyzed pretransplant and at different time points posttransplant for ≥24 mo in a cohort of CMV+ KTR (n = 112), stratified according to CMV viremia detection. In cryopreserved samples from a subgroup (n = 49), adaptive NKG2C+ NK cell markers and T cell subsets were compared after a longer follow-up (median, 56 mo), assessing the frequencies of CMV-specific T cells and viremia at the last time point. Increased proportions of NKG2C+ NK, CD8+, and TcRγδ T cells were detected along posttransplant evolution in viremia(+) KTR. However, the individual magnitude and kinetics of the NKG2C+ NK response was variable and only exceptionally detected among viremia(-) KTR, presumably reflecting subclinical viral replication events. NKG2C+ expansions were independent of KLRC2 zygosity and associated with higher viral loads at diagnosis; no relation with other clinical parameters was perceived. Increased proportions of adaptive NKG2C+ NK cells (CD57+, ILT2+, FcεRIγ-) were observed after resolution of viremia long-term posttransplant, coinciding with increased CD8+ and Vδ2- γδ T cells; at that stage CMV-specific T cells were comparable to viremia(-) cases. These data suggest that adaptive NKG2C+ NK cells participate with T cells to restore CMV replication control, although their relative contribution cannot be discerned.

Randomized clinical trial to assess the impact of oral intervention with cetylpyridinium chloride to reduce salivary SARS-CoV-2 viral load.

AIM: Aerosols released from the oral cavity help spread the SARS-CoV-2 virus. The use of a mouthwash formulated with an antiviral agent could reduce the viral load in saliva, helping to lower the spread of the virus. The aim of this study was to assess the efficacy of a mouthwash with 0.07% cetylpyridinium chloride (CPC) to reduce the viral load in the saliva of Coronavirus disease 2019 (COVID-19) patients. MATERIALS AND METHODS: In this multi-centre, single-blind, randomized, parallel group clinical trial, 80 COVID-19 patients were enrolled and randomized to two groups, namely test (n = 40) and placebo (n = 40). Saliva samples were collected at baseline and 2 h after rinsing. The samples were analysed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and an enzyme-linked immunosorbent assay test specific for the nucleocapsid (N) protein of SARS-CoV-2. RESULTS: With RT-qPCR, no significant differences were observed between the placebo group and the test group. However, 2 h after a single rinse, N protein concentration in saliva was significantly higher in the test group, indicating an increase in lysed virus. CONCLUSIONS: The use of 0.07% CPC mouthwash induced a significant increase in N protein detection in the saliva of COVID-19 patients. Lysis of the virus in the mouth could help reduce the transmission of SARS-CoV-2. However, more studies are required to prove this.

Limited Humoral and Specific T-Cell Responses After SARS-CoV-2 Vaccination in PWH With Poor Immune Reconstitution.

BACKGROUND: We analyzed humoral and cellular immune responses induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) messenger RNA (mRNA) vaccines in people with human immunodeficiency virus (HIV; PWH) who had CD4+ T-cell counts <200/µL (HIV<200 group). METHODS: This prospective cohort study included 58 PWH in the HIV<200 group, 36 with CD4+ T-cell counts >500/µL (HIV>500 group), and 33 HIV-1-negative controls (control group). Antibodies against the SARS-CoV-2 spike protein (anti-S immunoglobulin [Ig] G) and the receptor-binding domain (anti-RBD IgG) were quantified before and 4 weeks after the first and the second doses of BNT162b2 or mRNA-1273 (at week 8). Viral neutralization activity and T-cell responses were also determined. RESULTS: At week 8, anti-S/anti-RBD IgG responses increased in all groups (P < .001). Median (interquartile range) anti-S and anti-RBD IgG levels at week 8 were 153.6 (26.4-654.9) and 171.9 (61.8-425.8) binding antibody units (BAU)/mL, respectively, in the HIV<200 group, compared with 245.6 (145-824) and 555.8 (166.4-1751) BAU/mL in the HIV>500 group and 274.7 (193.7-680.4) and 281.6 (181-831.8) BAU/mL in controls (P < .05). Neutralizing capacity and specific T-cell immune responses were absent or reduced in 33% of those in the HIV<200 group, compared with 3.7% in the HIV>500 group (P < .01). CONCLUSIONS: One-third of PWH with CD4+ T-cell counts <200/µL show low anti-S/anti-RBD IgG levels, reduced in vitro neutralization activity against SARS-CoV-2, and no vaccine-induced T cells after receiving coronavirus disease 2019 mRNA vaccines.

Pretransplant adaptive NKG2C+ NK cells protect against cytomegalovirus infection in kidney transplant recipients.

Cytomegalovirus (CMV) infection constitutes a complication for kidney transplant recipients (KTR) and CMV-specific T cells reduce the risk of viral replication in seropositive patients. CMV promotes the adaptive differentiation and expansion of an NK cell subset, hallmarked by expression of the CD94/NKG2C receptor with additional characteristic features. We previously reported an association of pretransplant NKG2C+ NK cells with a reduced incidence of CMV infection. We have strengthened the analysis in cryopreserved peripheral blood mononuclear cells from an enlarged KTR cohort (n = 145) with homogeneous immunosuppression, excluding cases at low risk of infection (ie, CMV D-R-) or receiving antiviral prophylaxis. Moreover, adaptive NKG2C+ NK cell-associated markers (ie, NKG2A, CD57, Immunoglobulin-like transcript 2 [LIR1 or LILRB1], FcεRI γ chain, and Prolymphocytic Leukemia Zinc Finger transcription factor) as well as T lymphocyte subsets were assessed by multicolor flow cytometry. The relation of NKG2C+ NK cells with T cells specific for CMV antigens was analyzed in pretransplant patients (n = 29) and healthy controls (n = 28). Multivariate Cox regression and Kaplan-Meier analyses supported that NKG2C+ NK cells bearing adaptive markers were specifically associated with a reduced incidence of posttransplant symptomatic CMV infection; no correlation between NKG2C+ NK cells and CMV-specific T cells was observed. These results support that adaptive NKG2C+ NK cells contribute to control CMV infection in KTR.

mTORC2 Deficiency in Myeloid Dendritic Cells Enhances Their Allogeneic Th1 and Th17 Stimulatory Ability after TLR4 Ligation In Vitro and In Vivo.

The mammalian/mechanistic target of rapamycin (mTOR) is a key integrative kinase that functions in two independent complexes, mTOR complex (mTORC) 1 and mTORC2. In contrast to the well-defined role of mTORC1 in dendritic cells (DC), little is known about the function of mTORC2. In this study, to our knowledge, we demonstrate for the first time an enhanced ability of mTORC2-deficient myeloid DC to stimulate and polarize allogeneic T cells. We show that activated bone marrow-derived DC from conditional Rictor(-/-) mice exhibit lower coinhibitory B7-H1 molecule expression independently of the stimulus and enhanced IL-6, TNF-α, IL-12p70, and IL-23 production following TLR4 ligation. Accordingly, TLR4-activated Rictor(-/-) DC display augmented allogeneic T cell stimulatory ability, expanding IFN-γ(+) and IL-17(+), but not IL-10(+) or CD4(+)Foxp3(+) regulatory T cells in vitro. A similar DC profile was obtained by stimulating Dectin-1 (C-type lectin family member) on Rictor(-/-) DC. Using novel CD11c-specific Rictor(-/-) mice, we confirm the alloreactive Th1 and Th17 cell-polarizing ability of endogenous mTORC2-deficient DC after TLR4 ligation in vivo. Furthermore, we demonstrate that proinflammatory cytokines produced by Rictor(-/-) DC after LPS stimulation are key in promoting Th1/Th17 responses. These data establish that mTORC2 activity restrains conventional DC proinflammatory capacity and their ability to polarize T cells following TLR and non-TLR stimulation. Our findings provide new insight into the role of mTORC2 in regulating DC function and may have implications for emerging therapeutic strategies that target mTOR in cancer, infectious diseases, and transplantation.

Cutting edge: Flt3 ligand mediates STAT3-independent expansion but STAT3-dependent activation of myeloid-derived suppressor cells.

The Flt3-Flt3 ligand (Flt3L) pathway is critically involved in the differentiation and homeostasis of myeloid cells, including dendritic cells (DC); however, its role in the expansion and function of myeloid-derived suppressor cells (MDSC) has not been determined. In this article, we describe the ability of Flt3L to expand and activate murine MDSC capable of suppressing allograft rejection upon adoptive transfer. Although Flt3L expands and augments the stimulatory capacity of myeloid DC, MDSC expanded by Flt3L have increased suppressive activity. Although STAT3 is considered the central transcription factor for MDSC expansion, inhibition and genetic ablation of STAT3 did not block, but rather augmented, Flt3L-mediated MDSC expansion. MDSC suppressive function, preserved when STAT3 inhibition was removed, was reduced by genetic STAT3 deletion. Both STAT3 inhibition and deletion reduced Flt3L-mediated DC expansion, signifying that STAT3 had reciprocal effects on suppressive MDSC and immunostimulatory DC expansion. Together, these findings enhance our understanding of the immunomodulatory properties of Flt3L.

Murine dendritic cell rapamycin-resistant and rictor-independent mTOR controls IL-10, B7-H1, and regulatory T-cell induction.

Mammalian target of rapamycin (mTOR) is an important, yet poorly understood integrative kinase that regulates immune cell function. mTOR functions in 2 independent complexes: mTOR complex (mTORC) 1 and 2. The immunosuppressant rapamycin (RAPA) inhibits mTORC1 but not mTORC2 and causes a paradoxical reduction in anti-inflammatory interleukin (IL) 10 and B7-homolog 1 (B7-H1) expression by dendritic cells (DCs). Using catalytic mTOR inhibitors and DCs lacking mTORC2, we show that restraint of signal transducer and activator of transcription 3-mediated IL-10 and B7-H1 expression during DC maturation involves a RAPA-insensitive and mTORC2-independent mTOR mechanism. Relatedly, catalytic mTOR inhibition promotes B7-H1-dependent and IL-1ß-dependent DC induction of regulatory T cells (Tregs). Thus, we define an immunoregulatory pathway in which RAPA-sensitive mTORC1 in DCs promotes effector T-cell expansion and RAPA-insensitive mTORC1 restrains T(reg) induction. These findings identify the first known RAPA-insensitive mTOR pathway that is not mediated solely by mTORC2 and have implications for the use of catalytic mTOR inhibitors in inflammatory disease settings.

Preclinical development of humanized monoclonal antibodies against CD169 as a broad antiviral therapeutic strategy.

New therapies to treat or prevent viral infections are essential, as recently observed during the COVID-19 pandemic. Here, we propose a therapeutic strategy based on monoclonal antibodies that block the specific interaction between the host receptor Siglec-1/CD169 and gangliosides embedded in the viral envelope. Antibodies are an excellent option for treating infectious diseases based on their high specificity, strong targeting affinity, and relatively low toxicity. Through a process of humanization, we optimized monoclonal antibodies to eliminate sequence liabilities and performed biophysical characterization. We demonstrated that they maintain their ability to block viral entry into myeloid cells. These molecular improvements during the discovery stage are key if we are to maximize efforts to develop new therapeutic strategies. Humanized monoclonal antibodies targeting CD169 provide new opportunities in the treatment of infections caused by ganglioside-containing enveloped viruses, which pose a constant threat to human health. In contrast with current neutralizing antibodies that bind antigens on the infectious particle, our antibodies can prevent several types of enveloped viruses interacting with host cells because they target the host CD169 protein, thus becoming a potential pan-antiviral therapy.

A monoclonal antibody targeting a large surface of the receptor binding motif shows pan-neutralizing SARS-CoV-2 activity.

Here we report the characterization of 17T2, a SARS-CoV-2 pan-neutralizing human monoclonal antibody isolated from a COVID-19 convalescent individual infected during the first pandemic wave. 17T2 is a class 1 VH1-58/κ3-20 antibody, derived from a receptor binding domain (RBD)-specific IgA+ memory B cell, with a broad neutralizing activity against former and new SARS-CoV-2 variants, including XBB.1.16 and BA.2.86 Omicron subvariants. Consistently, 17T2 demonstrates in vivo prophylactic and therapeutic activity against Omicron BA.1.1 infection in K18-hACE2 mice. Cryo-electron microscopy reconstruction shows that 17T2 binds the BA.1 spike with the RBD in "up" position and blocks the receptor binding motif, as other structurally similar antibodies do, including S2E12. Yet, unlike S2E12, 17T2 retains its neutralizing activity against all variants tested, probably due to a larger RBD contact area. These results highlight the impact of small structural antibody changes on neutralizing performance and identify 17T2 as a potential candidate for future clinical interventions.

Alloimmune risk assessment for antibody-mediated rejection in kidney transplantation: A practical proposal.

Kidney transplantation is the treatment of choice for patients with end-stage renal disease. Although an improvement in graft survival has been observed in the last decades with the use of different immunosuppressive drugs, this is still limited in time with antibody-mediated rejection being a main cause of graft-loss. Immune monitoring and risk assessment of antibody-mediated rejection before and after kidney transplantation with useful biomarkers is key to tailoring treatments to achieve the best outcomes. Here, we provide a review of the rationale and several accessible tools for immune monitoring, from the most classic to the modern ones. Finally, we end up discussing a practical proposal for alloimmune risk assessment in kidney transplantation, including histocompatibility leukocyte antigen (HLA) and non-HLA antibodies, HLA molecular mismatch analysis and characterization of peripheral blood immune cells.

Role of Siglecs in viral infections: A double-edged sword interaction.

Sialic-acid-binding immunoglobulin-like lectins are cell surface immune receptors known as Siglecs that play a paramount role as modulators of immunity. In recent years, research has underscored how the underlaying biology of this family of receptors influences the outcome of viral infections. While Siglecs are needed to promote effective antiviral immune responses, they can also pave the way to viral dissemination within tissues. Here, we review how recent preclinical findings focusing on the interplay between Siglecs and viruses may translate into promising broad-spectrum therapeutic interventions or key biomarkers to monitor the course of viral infections.

Self-sampling monkeypox virus testing in high-risk populations, asymptomatic or with unrecognized Mpox, in Spain.

The recent monkeypox virus (MPXV) outbreak was of global concern and has mainly affected gay, bisexual and other men who have sex with men (GBMSM). Here we assess prevalence of MPXV in high-risk populations of GBMSM, trans women (TW) and non-binary people without symptoms or with unrecognized monkeypox (Mpox) symptoms, using a self-sampling strategy. Anal and pharyngeal swabs are tested by MPXV real-time PCR and positive samples are tested for cytopathic effect (CPE) in cell culture. 113 individuals participated in the study, 89 (78.76%) were cis men, 17 (15.04%) were TW. The median age was 35.0 years (IQR: 30.0-43.0), 96 (85.02%) individuals were gay or bisexual and 72 (63.72%) were migrants. Seven participants were MPXV positive (6.19% (95% CI: 1.75%-10.64%)). Five tested positive in pharyngeal swabs, one in anal swab and one in both. Six did not present symptoms recognized as MPXV infection. Three samples were positive for CPE, and showed anti-vaccinia pAb staining by FACS and confocal microscopy. This suggests that unrecognized Mpox cases can shed infectious virus. Restricting testing to individuals reporting Mpox symptoms may not be sufficient to contain outbreaks.

ß-Cyclodextrins as affordable antivirals to treat coronavirus infection.

The SARS-CoV-2 pandemic made evident that there are only a few drugs against coronavirus. Here we aimed to identify a cost-effective antiviral with broad spectrum activity and high safety profile. Starting from a list of 116 drug candidates, we used molecular modelling tools to rank the 44 most promising inhibitors. Next, we tested their efficacy as antivirals against α and ß coronaviruses, such as the HCoV-229E and SARS-CoV-2 variants. Four drugs, OSW-1, U18666A, hydroxypropyl-ß-cyclodextrin (HßCD) and phytol, showed in vitro antiviral activity against HCoV-229E and SARS-CoV-2. The mechanism of action of these compounds was studied by transmission electron microscopy and by fusion assays measuring SARS-CoV-2 pseudoviral entry into target cells. Entry was inhibited by HßCD and U18666A, yet only HßCD inhibited SARS-CoV-2 replication in the pulmonary Calu-3 cells. Compared to the other cyclodextrins, ß-cyclodextrins were the most potent inhibitors, which interfered with viral fusion via cholesterol depletion. ß-cyclodextrins also prevented infection in a human nasal epithelium model ex vivo and had a prophylactic effect in the nasal epithelium of hamsters in vivo. All accumulated data point to ß-cyclodextrins as promising broad-spectrum antivirals against different SARS-CoV-2 variants and distant alphacoronaviruses. Given the wide use of ß-cyclodextrins for drug encapsulation and their high safety profile in humans, our results support their clinical testing as prophylactic antivirals.

Safety and immunogenicity of a recombinant protein RBD fusion heterodimer vaccine against SARS-CoV-2.

In response to COVID-19 pandemic, we have launched a vaccine development program against SARS-CoV-2. Here we report the safety, tolerability, and immunogenicity of a recombinant protein RBD fusion heterodimeric vaccine against SARS-CoV-2 (PHH-1V) evaluated in a phase 1-2a dose-escalation, randomized clinical trial conducted in Catalonia, Spain. 30 young healthy adults were enrolled and received two intramuscular doses, 21 days apart of PHH-1V vaccine formulations [10 µg (n = 5), 20 µg (n = 10), 40 µg (n = 10)] or control [BNT162b2 (n = 5)]. Each PHH-1V group had one safety sentinel and the remaining participants were randomly assigned. The primary endpoint was solicited events within 7 days and unsolicited events within 28 days after each vaccination. Secondary endpoints were humoral and cellular immunogenicity against the variants of concern (VOCs) alpha, beta, delta and gamma. All formulations were safe and well tolerated, with tenderness and pain at the site of injection being the most frequently reported solicited events. Throughout the study, all participants reported having at least one mild to moderate unsolicited event. Two unrelated severe adverse events (AE) were reported and fully resolved. No AE of special interest was reported. Fourteen days after the second vaccine dose, all participants had a >4-fold change in total binding antibodies from baseline. PHH-1V induced robust humoral responses with neutralizing activities against all VOCs assessed (geometric mean fold rise at 35 days p < 0.0001). The specific T-cell response assessed by ELISpot was moderate. This initial evaluation has contributed significantly to the further development of PHH-1V, which is now included in the European vaccine portfolio.ClinicalTrials.gov Identifier NCT05007509EudraCT No. 2021-001411-82.

Safety and immunogenicity of the protein-based PHH-1V compared to BNT162b2 as a heterologous SARS-CoV-2 booster vaccine in adults vaccinated against COVID-19: a multicentre, randomised, double-blind, non-inferiority phase IIb trial.

Background: A SARS-CoV-2 protein-based heterodimer vaccine, PHH-1V, has been shown to be safe and well-tolerated in healthy young adults in a first-in-human, Phase I/IIa study dose-escalation trial. Here, we report the interim results of the Phase IIb HH-2, where the immunogenicity and safety of a heterologous booster with PHH-1V is assessed versus a homologous booster with BNT162b2 at 14, 28 and 98 days after vaccine administration. Methods: The HH-2 study is an ongoing multicentre, randomised, active-controlled, double-blind, non-inferiority Phase IIb trial, where participants 18 years or older who had received two doses of BNT162b2 were randomly assigned in a 2:1 ratio to receive a booster dose of vaccine-either heterologous (PHH-1V group) or homologous (BNT162b2 group)-in 10 centres in Spain. Eligible subjects were allocated to treatment stratified by age group (18-64 versus ≥65 years) with approximately 10% of the sample enrolled in the older age group. The primary endpoints were humoral immunogenicity measured by changes in levels of neutralizing antibodies (PBNA) against the ancestral Wuhan-Hu-1 strain after the PHH-1V or the BNT162b2 boost, and the safety and tolerability of PHH-1V as a boost. The secondary endpoints were to compare changes in levels of neutralizing antibodies against different variants of SARS-CoV-2 and the T-cell responses towards the SARS-CoV-2 spike glycoprotein peptides. The exploratory endpoint was to assess the number of subjects with SARS-CoV-2 infections ≥14 days after PHH-1V booster. This study is ongoing and is registered with ClinicalTrials.gov, NCT05142553. Findings: From 15 November 2021, 782 adults were randomly assigned to PHH-1V (n = 522) or BNT162b2 (n = 260) boost vaccine groups. The geometric mean titre (GMT) ratio of neutralizing antibodies on days 14, 28 and 98, shown as BNT162b2 active control versus PHH-1V, was, respectively, 1.68 (p < 0.0001), 1.31 (p = 0.0007) and 0.86 (p = 0.40) for the ancestral Wuhan-Hu-1 strain; 0.62 (p < 0.0001), 0.65 (p < 0.0001) and 0.56 (p = 0.003) for the Beta variant; 1.01 (p = 0.92), 0.88 (p = 0.11) and 0.52 (p = 0.0003) for the Delta variant; and 0.59 (p ≤ 0.0001), 0.66 (p < 0.0001) and 0.57 (p = 0.0028) for the Omicron BA.1 variant. Additionally, PHH-1V as a booster dose induced a significant increase of CD4+ and CD8+ T-cells expressing IFN-γ on day 14. There were 458 participants who experienced at least one adverse event (89.3%) in the PHH-1V and 238 (94.4%) in the BNT162b2 group. The most frequent adverse events were injection site pain (79.7% and 89.3%), fatigue (27.5% and 42.1%) and headache (31.2 and 40.1%) for the PHH-1V and the BNT162b2 groups, respectively. A total of 52 COVID-19 cases occurred from day 14 post-vaccination (10.14%) for the PHH-1V group and 30 (11.90%) for the BNT162b2 group (p = 0.45), and none of the subjects developed severe COVID-19. Interpretation: Our interim results from the Phase IIb HH-2 trial show that PHH-1V as a heterologous booster vaccine, when compared to BNT162b2, although it does not reach a non-inferior neutralizing antibody response against the Wuhan-Hu-1 strain at days 14 and 28 after vaccination, it does so at day 98. PHH-1V as a heterologous booster elicits a superior neutralizing antibody response against the previous circulating Beta and the currently circulating Omicron BA.1 SARS-CoV-2 variants in all time points assessed, and for the Delta variant on day 98 as well. Moreover, the PHH-1V boost also induces a strong and balanced T-cell response. Concerning the safety profile, subjects in the PHH-1V group report significantly fewer adverse events than those in the BNT162b2 group, most of mild intensity, and both vaccine groups present comparable COVID-19 breakthrough cases, none of them severe. Funding: HIPRA SCIENTIFIC, S.L.U.

Regulatory role of vitamin D in T-cell reactivity against myelin peptides in relapsing-remitting multiple sclerosis patients.

BACKGROUND: Low levels of plasma 25-hydroxyvitaminD (25(OH)D) are associated with a higher incidence of multiple sclerosis (MS) due to the immune suppressive properties of vitamin D.The aim of this study was to determine the correlation between plasma 25(OH)D concentrations and clinical and immunological variables in a cohort of multiple sclerosis patients. METHODS: Plasma 25(OH)D concentrations were evaluated in summer and winter in 15 primary progressive MS (PPMS) patients, 40 relapsing- remitting MS (RRMS) patients and 40 controls (HC). Protocol variables included demographic and clinical data, radiological findings and immunological variables (oligoclonal bands, HLADR15 and T-lymphocyte proliferation to a definite mix of 7 myelin peptides). RESULTS: During the winter, plasma concentrations were significantly lower in RRMS patients compared to HC, whereas no differences were found in summer. No relationships were found between plasma 25(OH)D concentrations and clinical or radiological variables. RRMS patients with a positive T-cell proliferation to a mix of myelin peptides (n = 31) had lower 25(OH)D concentrations. CONCLUSIONS: 25(OH)D is an immunomodulatory molecule that might have a regulatory role in T-cell proliferation to myelin peptides in RRMS patients.

Phosphorylation of S6RP in peritubular capillaries of kidney grafts and circulating HLA donor-specific antibodies.

Antibody-mediated rejection (ABMR) caused by donor-specific HLA-antibodies (DSA) is a mediator of allograft loss after kidney transplantation (KT). DSA can activate microvascular endothelium damage through the mTOR pathway. In this study we assessed the mTOR pathway activation by DSA in KT with ABMR (ABMR + DSA+) compared to controls (ABMR-DSA-), biopsies with ABMR changes without DSA (ABMR + DSA-) and DSA without ABMR changes (ABMR-DSA+), and the potential modulation by mTOR inhibitors (mTORi). We evaluated 97 biopsies: 31 ABMR + DSA+, 33 controls ABMR-DSA-, 16 ABMR + DSA-, and 17 ABMR-DSA+ cases. Regarding immunosuppression of full ABMR + DSA+ and controls, 21 biopsies were performed under mTORi treatment (11 of them ABMR + DSA+ cases) and 43 without mTORi (20 of them ABMR + DSA+) so as to explore its effect on the mTOR pathway. Biopsies were stained for C4d, Ki67, and phosphorylated (p) S6RP, ERK, and mTOR by immunohistochemistry. Labeling was graded according to peritubular capillary staining. ABMR biopsies showed significantly higher C4d, p-S6RP, and Ki67 staining in peritubular capillaries (PTC) compared to controls, and light differences in p-ERK or p-mTOR. mTORi treatment did not modify p-S6RP, p-mTOR, and p-ERK staining. Diffuse p-S6RP in PTC in the biopsies significantly associated with circulating HLA-DSA independently of graft rejection, and with worse death-censored graft survival. These findings suggest that activation of endothelium through the mTOR pathway evidence different mechanisms of damage in ABMR + DSA+ and ABMR + DSA- despite similar histological injury.

Performance of SARS-CoV-2 Antigen-Detecting Rapid Diagnostic Tests for Omicron and Other Variants of Concern.

The SARS-CoV-2 antigen-detecting rapid diagnostic test (Ag-RDTs) is an easy-to-use diagnostic tool to identify the contagious individuals and reduce the new infections. However, to be effective, Ag-RDTs require the detection of distinct variants of concern (VOC) with high analytical sensitivity. Here, we found that the VOC diverge at the nucleocapsid protein used by four commercial Ag-RDTs for the viral detection. Relative to the original D614G variant, there was a 10-fold loss of detection for the Delta and Alpha variants in certain Ag-RDTs, a reduction above the threshold required to isolate the viable virus. However, Beta and Omicron variants did not lose the detection capacity. As the new VOC arise, successful contact tracing requires continuous monitoring of Ag-RDTs performance.