Platelet transfusion practice pattern before and after implementation of a local restrictive transfusion protocol in a neonatal intensive care unit.

BACKGROUND: Following the results of the PlaNeT-2 randomized controlled trial showing decreased morbidity and mortality in neonates transfused at a threshold of 25 versus 50 × 109 platelets/L, a protocol supporting restrictive platelet transfusions was established in 2019 at the Sainte-Justine Hospital neonatal intensive care unit (NICU). This study aimed to: (1) determine the impact of a local restrictive transfusion protocol on the number of platelet transfusions and donor exposure; (2) compare platelet-transfusion determinants and justifications before and after its implementation. STUDY DESIGN AND METHODS: Prospective observational cohort chart-review study comparing all neonates consecutively admitted to the NICU during two 5-months periods: 2013 (before; N = 401) versus 2021 (after; N = 402). Possible determinants were assessed via logistic regressions and justifications via a questionnaire. RESULTS: Mean (± standard deviation) gestational age and birth weight were 34.9 ± 4.2 weeks and 2.5 ± 1.0 kg, respectively. In 2021, 5.0% were platelet-transfused versus 9.2% in 2013 (p = .027). Platelet transfusions decreased from a mean of 2.6 ± 1.7 in 2013 to 1.4 ± 0.7 in 2021 (p = .045). Adherence to protocol thresholds was of 70%. After protocol implementation, no infant received ≥4 platelet transfusions nor was exposed to ≥4 donors, compared to 29.7% and 21.6%, respectively, in 2013. Platelet transfusion justifications and determinants remained similar, except for severe intraventricular hemorrhage being an additional determinant in 2021. DISCUSSION: Restrictive local transfusion thresholds in a NICU decreased the proportion of platelet-transfused neonates by 46% and reduced donor exposure in transfused patients.

COVID-19-associated coagulopathy in children: A multicenter observational cohort study.

SARS-CoV-2 infection (coronavirus disease 2019 [COVID-19]) induces a stark procoagulant state, with many hospitalized adults developing thrombosis despite prophylactic anticoagulation. This study aimed to characterize hemostatic parameters and associated clinical outcomes of COVID-19, such as thrombosis and bleeding, in children and to assess thromboprophylaxis use. This multicenter observational cohort study included 79 patients aged up to 18 years admitted to all pediatric hospitals in Québec, Canada, with SARS-CoV-2 infection during a 5-month period. D-dimers were elevated in 18/19 patients (94.7%) and fibrinogen in 15/26 patients (60%). Eleven patients (13.9%) received anticoagulant thromboprophylaxis. One thrombotic event and one major bleed were observed.

Reevaluating immunization delays after red blood cell transfusion.

BACKGROUND: Current American and Canadian guidelines recommend delaying live vaccine immunization by 5 to 6 months after transfusion of red blood cells (RBCs) due to potential interference by serum antibodies. Due to lack of data, the recommendations may be unfounded and prevent valuable vaccination opportunities for children with frequent blood transfusions. The primary aim of this study was to determine measles, mumps, rubella (MMR) vaccine immunogenicity in patients chronically transfused with RBCs. A secondary aim was to quantify vaccine antibodies in RBC donations. STUDY DESIGN AND METHODS: MMR-specific antibodies were quantified in 25 pediatric patients who received both doses of MMR vaccine while on a chronic RBC transfusion program (median, 6.6 years after vaccination). MMR antibodies were also quantified in 30 samples of supernatants from RBC donations. RESULTS: Immunity to each of the MMR components was 68% to 76%. In blood donors born before 1976 (pre-MMR vaccine), 67% of MMR serologies in the supernatants of RBC donations were at the immune level versus 7% in blood donors born after 1976. CONCLUSION: This is the first study of the impact of RBC transfusions on MMR vaccine immunogenicity. Although lower than in the literature (immunity rates, ≥90%), the results show a high rate of immunogenicity of the MMR vaccine in chronically transfused patients. Additionally, results suggest that MMR antibody content in transfusions will continue to decrease with time. Weighing the risks and benefits of disease prevention in a vulnerable population, a reevaluation of immunization delays after RBC transfusions is called for.

Subcellular localization of coagulation factor II receptor-like 1 in neurons governs angiogenesis.

Neurons have an important role in retinal vascular development. Here we show that the G protein-coupled receptor (GPCR) coagulation factor II receptor-like 1 (F2rl1, previously known as Par2) is abundant in retinal ganglion cells and is associated with new blood vessel formation during retinal development and in ischemic retinopathy. After stimulation, F2rl1 in retinal ganglion cells translocates from the plasma membrane to the cell nucleus using a microtubule-dependent shuttle that requires sorting nexin 11 (Snx11). At the nucleus, F2rl1 facilitates recruitment of the transcription factor Sp1 to trigger Vegfa expression and, in turn, neovascularization. In contrast, classical plasma membrane activation of F2rl1 leads to the expression of distinct genes, including Ang1, that are involved in vessel maturation. Mutant versions of F2rl1 that prevent nuclear relocalization but not plasma membrane activation interfere with Vegfa but not Ang1 expression. Complementary angiogenic factors are therefore regulated by the subcellular localization of a receptor (F2rl1) that governs angiogenesis. These findings may have implications for the selectivity of drug actions based on the subcellular distribution of their targets.

Ischemic neurons prevent vascular regeneration of neural tissue by secreting semaphorin 3A.

The failure of blood vessels to revascularize ischemic neural tissue represents a significant challenge for vascular biology. Examples include proliferative retinopathies (PRs) such as retinopathy of prematurity and proliferative diabetic retinopathy, which are the leading causes of blindness in children and working-age adults. PRs are characterized by initial microvascular degeneration, followed by a compensatory albeit pathologic hypervascularization mounted by the hypoxic retina attempting to reinstate metabolic equilibrium. Paradoxically, this secondary revascularization fails to grow into the most ischemic regions of the retina. Instead, the new vessels are misdirected toward the vitreous, suggesting that vasorepulsive forces operate in the avascular hypoxic retina. In the present study, we demonstrate that the neuronal guidance cue semaphorin 3A (Sema3A) is secreted by hypoxic neurons in the avascular retina in response to the proinflammatory cytokine IL-1ß. Sema3A contributes to vascular decay and later forms a chemical barrier that repels neo-vessels toward the vitreous. Conversely, silencing Sema3A expression enhances normal vascular regeneration within the ischemic retina, thereby diminishing aberrant neovascularization and preserving neuroretinal function. Overcoming the chemical barrier (Sema3A) released by ischemic neurons accelerates the vascular regeneration of neural tissues, which restores metabolic supply and improves retinal function. Our findings may be applicable to other neurovascular ischemic conditions such as stroke.

Identification of novel mutations responsible for resistance to MK-2048, a second-generation HIV-1 integrase inhibitor.

MK-2048 represents a prototype second-generation integrase strand transfer inhibitor (INSTI) developed with the goal of retaining activity against viruses containing mutations associated with resistance to first-generation INSTIs, raltegravir (RAL) and elvitegravir (EVG). Here, we report the identification of mutations (G118R and E138K) which confer resistance to MK-2048 and not to RAL or EVG. These mutations were selected in vitro and confirmed by site-specific mutagenesis. G118R, which appeared first in cell culture, conferred low levels of resistance to MK-2048. G118R also reduced viral replication capacity to approximately 1% that of the isogenic wild-type (wt) virus. The subsequent selection of E138K partially restored replication capacity to approximately 13% of wt levels and increased resistance to MK-2048 to approximately 8-fold. Viruses containing G118R and E138K remained largely susceptible to both RAL and EVG, suggesting a unique interaction between this second-generation INSTI and the enzyme may be defined by these residues as a potential basis for the increased intrinsic affinity and longer "off" rate of MK-2048. In silico structural analysis suggests that the introduction of a positively charged arginine at position 118, near the catalytic amino acid 116, might decrease Mg(2+) binding, compromising enzyme function and thus leading to the significant reduction in both integration and viral replication capacity observed with these mutations.