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Targeting of different tissues via transcutaneous (TC), intradermal (ID) and intramuscular (IM) injection has the potential to tailor the immune response to DNA vaccination. In this Phase I randomised controlled clinical trial in HIV-1 negative volunteers we investigate whether the site and mode of DNA vaccination influences the quality of the cellular immune responses. We adopted a strategy of concurrent immunization combining IM injection with either ID or TC administration. As a third arm we assessed the response to IM injection administered with electroporation (EP). The DNA plasmid encoded a MultiHIV B clade fusion protein designed to induce cellular immunity. The vaccine and regimens were well tolerated. We observed differential shaping of vaccine induced virus-specific CD4 + and CD8 + cell-mediated immune responses. DNA given by IM + EP promoted strong IFN-γ responses and potent viral inhibition. ID + IM without EP resulted in a similar pattern of response but of lower magnitude. By contrast TC + IM (without EP) shifted responses towards a more Th-17 dominated phenotype, associated with mucosal and epidermal protection. Whilst preliminary, these results offer new perspectives for differential shaping of desired cellular immunity required to fight the wide range of complex and diverse infectious diseases and cancers.

Previous studies have shown targeting different tissues via the transcutaneous (TC) and intramuscular injection (IM) with or without electroporation (EP) has the potential to trigger immune responses to DNA vaccination. The CUTHIVTHER 001 Phase I/II randomized controlled clinical trial was designed to determine whether the mode of DNA vaccination delivery (TC+IM or EP+IM) could influence the quality and function of induced cellular immune responses compared to placebo, in an HIV positive clade B cohort on antiretroviral therapy (ART). The GTU MultiHIV B DNA vaccine DNA vaccine encoded a MultiHIV B clade fusion protein to target the cellular response. Overall the vaccine and regimens were safe and well-tolerated. There were robust pre-vaccination IFN-γ responses with no measurable change following vaccination compared to placebo. However, modest intracellular cytokine staining (ICS) responses were seen in the TC+IM group. A high proportion of individuals demonstrated potent viral inhibition at baseline that was not improved by vaccination. These results show that HIV positive subjects with nadir CD4+ counts ≥250 on suppressive ART display potent levels of cellular immunity and viral inhibition, and that DNA vaccination alone is insufficient to improve such responses. These data suggest that more potent prime-boost vaccination strategies are likely needed to improve pre-existing responses in similar HIV-1 cohorts (This study has been registered at http://ClinicalTrials.gov under registration no. NCT02457689).

Doc number: O64

Natural and vaccine-induced immunity and immunological memory to Haemophilus influenzae type b (Hib) were evaluated in adolescents and adults with β-thalassemia. At baseline 10/23 (43%) unvaccinated patients had naturally acquired anticapsular antibodies >0.15 μg/ml, the threshold of protection, compared to 9/10 (90%) aged-matched controls. Hib-conjugate vaccine (PRP-T) induced protective immune responses in all subjects and there were no differences in geometric mean concentrations at 1 month (GMC) between patients and controls (69.04 versus 40.5, respectively). Vaccine-induced immunological memory was assessed in 12 subjects with β-thalassemia who had been vaccinated against Hib in the past. All subjects had retained PRP > 1 μg/ml at baseline; PRP-T revaccination induced anamnestic responses which were similar, in terms of post vaccination antibody concentration ( P = 0.54) and avidity ( P = 0.08), with primary responses given by previously unvaccinated patients. A single dose of PRP-T induces adequate and long-lasting immunity and should be given in all unvaccinated adolescents and adults with β-thalassemia.

Objective Pacing in a univentricular circulation has been associated with worsened outcomes. We investigated the long‐term outcomes of pacing in children with a univentricular circulation compared to a complex biventricular circulation. We also identified predictors of adverse outcomes. Methods A retrospective study of all children with major congenital heart disease who underwent pacemaker implantation under the age of 18 years between November 1994 and October 2017. Results Eighty‐nine patients were included; 19 with a univentricular and 70 with a complex biventricular circulation. A total of 96% of pacemaker systems were epicardial. Median follow up was 8.3 years. The incidence of adverse outcome was similar between the two groups. Five (5.6%) patients died and two (2.2%) underwent heart transplantation. Most adverse events occurred within the first 8 years after pacemaker implantation. Univariate analysis identified five predictors of adverse outcomes in the patients in the biventricular but none in the univentricular group. The predictors of adverse outcome in the biventricular circulation were a right morphologic ventricle as the systemic ventricle, age at first congenital heart disease (CHD) operation, number of CHD operations, and female gender. The nonapical lead position was associated with a much higher risk of an adverse outcome. Conclusions Children with a pacemaker and a complex biventricular circulation have similar survival to the ones with a pacemaker and a univentricular circulation. The only modifiable predictor was the epicardial lead position on the paced ventricle, emphasizing the importance of apical placement of the ventricular lead.

Pediatric cardiac symptoms such as palpitations, syncope, or seizure-like episodes pose diagnostic challenges for general pediatricians. These symptoms, though often benign, may reveal underlying arrhythmias or inherited cardiac conditions (ICCs), affecting the quality of life and limiting activity participation. The purpose of this study is to determine the effectiveness and safety of implantable loop recorders (ILRs) in diagnosing and managing arrhythmias in pediatric patients. A retrospective cohort study conducted over an 8-year period from January 2016 to December 2023 in a single pediatric cardiology center. A cohort of 155 pediatric patients (median age 11.4 years) who underwent ILR implantation were selected based on symptoms such as palpitations, chest pain, or syncope, and those with previously recorded arrhythmias or high-risk ICCs. The primary outcomes were the diagnostic yield of ILRs for arrhythmias and subsequent changes in patient management. Diagnostic yield was defined as the detection of relevant arrhythmias, such as pauses of 3 s or longer, high-degree AV block, sinus node dysfunction, supraventricular tachycardia, ventricular tachycardia, or inappropriate sinus tachycardia. The median follow-up period was 2.3 years (845 days). Diagnostic arrhythmias were recorded in 60% of patients with symptom-activated transmissions and 80% of device-activated transmissions. Sinus pauses (37.5%) and VT (30%) were the most common arrhythmias detected. In patients with syncope ( n  = 76), 30% had relevant arrhythmias. In the palpitations group ( n  = 20), 35% had relevant arrhythmias. Approximately 80% of patients with ILR-diagnosed arrhythmias underwent targeted management, including medication changes and additional procedures. No significant complications were observed; minor complications occurred in 2.5% of patients. Conclusions : New generation ILRs are effective and safe for diagnosing and managing pediatric arrhythmias, providing significant reassurance to patients and families. Further studies are needed to evaluate the impact of ILRs on quality of life and sports participation in high-risk young patients. What is Known: • Pediatric Cardiac Symptoms: Symptoms like palpitations, syncope, and seizure-like episodes in pediatric patients pose significant diagnostic challenges. • Diagnostic Tools: Traditional diagnostic tools such as ECG, Holter monitors, and external loop recorders often have low diagnostic yields due to the sporadic nature of symptoms. • Implantable Loop Recorders (ILRs): ILRs have been shown to improve the diagnostic yield for arrhythmias in adults and provide long-term rhythm monitoring. What is New: • Effectiveness in Pediatrics: This study demonstrates that new generation ILRs significantly enhance the diagnostic yield for arrhythmias in pediatric patients with undiagnosed cardiac symptoms. • Safety and Efficacy: The study confirms that ILRs are both safe and effective in the pediatric population, with minimal complications and high diagnostic accuracy. • Targeted Management: Findings show that ILR-diagnosed arrhythmias lead to targeted management changes in approximately 80% of cases, including medication adjustments and additional procedures. • Long-term Monitoring: ILRs provide continuous long-term monitoring, offering reassurance to patients and families, and potentially improving quality of life and participation in activities for high-risk young patients.

The effect of growth on the subcutaneous cardioverter defibrillators when implanted in small children is unknown. These two chest X-rays demonstrate that these devices can cope well with growth.The effect of growth on the subcutaneous cardioverter defibrillators when implanted in small children is unknown. These two chest X-rays demonstrate that these devices can cope well with growth.