Immune Response to Initial and Booster SARS-CoV-2 mRNA Vaccination in Patients Treated with Siponimod-Final Analysis of a Nonrandomized Controlled Clinical Trial (AMA-VACC).

BACKGROUND: Evidence on SARS-CoV-2 mRNA vaccination under siponimod treatment is rare. METHODS: AMA-VACC is a prospective, open-label clinical study on SARS-CoV-2 mRNA vaccination during ongoing siponimod treatment (cohort 1), during siponimod interruption (cohort 2), or during treatment with other disease-modifying therapies or without therapy (cohort 3). SARS-CoV-2-specific antibodies and T-cell reactivity were measured six months after the initial vaccination and one month after the booster. RESULTS: 41 patients were recruited into cohort 1 (n = 17), cohort 2 (n = 4), and cohort 3 (n = 20). Seroconversion for SARS-CoV-2 neutralizing antibodies was reached by 50.0%, 100.0%, and 90.0% of patients at month 6 and by 81.3%, 100.0%, and 100.0% one month after booster (cohorts 1, 2, and 3, respectively). Antibody levels in cohort 1 increased after the booster compared to month 6 but remained lower compared to cohorts 2 and 3. T-cell responses were seen in 28.5%, 25.0%, and 73.7% at month 6 and in 28.6%, 50.0%, and 83.3% after the booster (cohorts 1, 2, and 3, respectively). In cohort 1, the extent of T-cell response was lower at month 6 compared to cohorts 2 and 3 but reached almost similar levels after the booster. CONCLUSIONS: The antibody and T-cell responses support SARS-CoV-2 (booster) vaccines in siponimod-treated patients.

Role of the C5a-C5a receptor axis in the inflammatory responses of the lungs after experimental polytrauma and hemorrhagic shock.

Singular blockade of C5a in experimental models of sepsis is known to confer protection by rescuing lethality and decreasing pro-inflammatory responses. However, the role of inhibiting C5a has not been evaluated in the context of sterile systemic inflammatory responses, like polytrauma and hemorrhagic shock (PT + HS). In our presented study, a novel and highly specific C5a L-aptamer, NoxD21, was used to block C5a activity in an experimental murine model of PT + HS. The aim of the study was to assess early modulation of inflammatory responses and lung damage 4 h after PT + HS induction. NoxD21-treated PT + HS mice displayed greater polymorphonuclear cell recruitment in the lung, increased pro-inflammatory cytokine levels in the bronchoalveolar lavage fluids (BALF) and reduced myeloperoxidase levels within the lung tissue. An in vitro model of the alveolar-capillary barrier was established to confirm these in vivo observations. Treatment with a polytrauma cocktail induced barrier damage only after 16 h, and NoxD21 treatment in vitro did not rescue this effect. Furthermore, to test the exact role of both the cognate receptors of C5a (C5aR1 and C5aR2), experimental PT + HS was induced in C5aR1 knockout (C5aR1 KO) and C5aR2 KO mice. Following 4 h of PT + HS, C5aR2 KO mice had significantly reduced IL-6 and IL-17 levels in the BALF without significant lung damage, and both, C5aR1 KO and C5aR2 KO PT + HS animals displayed reduced MPO levels within the lungs. In conclusion, the C5aR2 could be a putative driver of early local inflammatory responses in the lung after PT + HS.

ATP is stored in lamellar bodies to activate vesicular P2X4 in an autocrine fashion upon exocytosis.

Vesicular P2X4 receptors are known to facilitate secretion and activation of pulmonary surfactant in the alveoli of the lungs. P2X4 receptors are expressed in the membrane of lamellar bodies (LBs), large secretory lysosomes that store lung surfactant in alveolar type II epithelial cells, and become inserted into the plasma membrane after exocytosis. Subsequent activation of P2X4 receptors by adenosine triphosphate (ATP) results in local fusion-activated cation entry (FACE), facilitating fusion pore dilation, surfactant secretion, and surfactant activation. Despite the importance of ATP in the alveoli, and hence lung function, the origin of ATP in the alveoli is still elusive. In this study, we demonstrate that ATP is stored within LBs themselves at a concentration of ∼1.9 mM. ATP is loaded into LBs by the vesicular nucleotide transporter but does not activate P2X4 receptors because of the low intraluminal pH (5.5). However, the rise in intravesicular pH after opening of the exocytic fusion pore results in immediate activation of vesicular P2X4 by vesicular ATP. Our data suggest a new model in which agonist (ATP) and receptor (P2X4) are located in the same intracellular compartment (LB), protected from premature degradation (ATP) and activation (P2X4), and ideally placed to ensure coordinated and timely receptor activation as soon as fusion occurs to facilitate surfactant secretion.