Publications by authors named "Kikkert M"

Background: Symptom severity and social functioning are important outcomes after first episode psychosis (FEP), yet current evidence about associations between them is inconsistent and lacks (subclinical) momentary insights.

Methods: The current Ecological Momentary Assessment (EMA) study was conducted in 58 people in remission from FEP, as part of the HAMLETT (Handling Antipsychotic Medication: Long-term Evaluation of Targeted Treatment) trial. At baseline, participants were prompted to report momentary mental states and social context 10x/day for eight consecutive days, including psychotic experiences (PEs), motivation/drive and negative affect, that may indicate proxies of (subclinical) psychotic, negative and general affective symptoms, respectively.

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Background: Recovery from severe mental illness, including psychosis has been described as a personal and unique process, but it rarely is a journey undertaken without profound influences of significant others (family, mental health professionals). Diverging perspectives between persons with severe mental illness, family and professionals are frequent during the recovery process, notably in psychotic disorders. We aimed to explore processes of collaboration during recovery, to inform recovery supporting practices.

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Background: A subgroup of patients with severe mental illness (SMI) is underrepresented in scientific research, in part due to barriers around giving informed consent. This may lead to response bias and lack of knowledge about this group. Retrospective research with existing patient data is the only way to increase our knowledge for some patient groups.

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Clinical outcomes after a first-episode of psychosis (FEP) are heterogeneous. Many patient-related factors such as gender and comorbidity have been studied to predict symptomatic outcomes. However, psychiatrist-related factors such as prescription behaviour and gender have received little attention.

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The SARS-CoV-2 pandemic and the emergence of novel virus variants have had a dramatic impact on public health and the world economy, underscoring the need for detailed studies that explore the high efficacy of additional vaccines in animal models. In this study, we confirm the pathogenicity of the SARS-CoV-2/Leiden_008 isolate (GenBank accession number MT705206.1) in K18-hACE2 transgenic mice.

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Usutu virus (USUV) is an emerging flavivirus that can infect birds and mammals. In humans, in severe cases, it may cause neuroinvasive disease. The innate immune system, and in particular the interferon response, functions as the important first line of defense against invading pathogens such as USUV.

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Human coronavirus 229E (HCoV-229E) is associated with upper respiratory tract infections and generally causes mild respiratory symptoms. HCoV-229E infection can cause cell death, but the molecular pathways that lead to virus-induced cell death as well as the interplay between viral proteins and cellular cell death effectors remain poorly characterized for HCoV-229E. Studying how HCoV-229E and other common cold coronaviruses interact with and affect cell death pathways may help to understand its pathogenesis and compare it to that of highly pathogenic coronaviruses.

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Article Synopsis
  • Numerous viruses carry deubiquitinating proteases in their genomes, which play a role in evading the host's immune response by cleaving ubiquitin chains from immune-related substrates.* -
  • Ubiquitination is a critical cellular process involved in signaling and immune response, and viral proteins can interfere with this process, impacting the effectiveness of antiviral defenses.* -
  • The review highlights potential drug targets within viral proteases, focusing on the development of small molecule inhibitors to block these enzymes and their functions.*
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Objectives: The aim of this study was to assess the safety and immunogenicity of a dose-sparing fractional intradermal (ID) booster strategy with the mRNA-1273 COVID-19 vaccine.

Methods: COVID-19 naive adults aged 18-30 years were recruited from a previous study on primary vaccination regimens that compared 20 μg ID vaccinations with 100 μg intramuscular (IM) vaccinations with mRNA-1273 as the primary vaccination series. Participants previously immunized with ID regimens were randomly assigned (1:1) to receive a fractional ID booster dose (20 μg) or the standard-of-care intramuscular (IM) booster dose (50 μg) of the mRNA-1273 vaccine, 6 months after completing their primary series (ID-ID and ID-IM group, respectively).

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The coronavirus papain-like protease (PLpro) is crucial for viral replicase polyprotein processing. Additionally, PLpro can subvert host defense mechanisms by its deubiquitinating (DUB) and deISGylating activities. To elucidate the role of these activities during SARS-CoV-2 infection, we introduced mutations that disrupt binding of PLpro to ubiquitin or ISG15.

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Background: Depressed patients who have become victim of violence are prone to revictimization. However, no evidence-based interventions aimed at reducing revictimization in this group exist.

Methods: This multicenter randomized controlled trial evaluated the effectiveness of an internet-based emotion regulation training (iERT) added to TAU in reducing revictimization, emotion dysregulation, and depressive symptoms in recently victimized, depressed patients compared to TAU alone.

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Article Synopsis
  • * A study tested five spike variants with different stability levels in mice, finding that a highly stable variant (S-closed-2) induced the highest neutralizing antibody response, outperforming less stable proteins by up to 16 times.
  • * However, the most stable variant (S-locked), which prevented the spike from interacting flexibly, produced lower antibody levels against diverse strains, suggesting that further research is needed on spike protein designs to improve vaccine effectiveness.
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Background: In patients with a psychotic disorder, rates of substance use (tobacco, cannabis, and alcohol) are higher compared to the general population. However, little is known about associations between substance use and self-reported aspects of social functioning in patients with a psychotic disorder.

Methods: In this cross-sectional study of 281 community-dwelling patients with a psychotic disorder, linear regression models were used to assess associations between substance use (tobacco, cannabis, or alcohol) and self-reported aspects of social functioning (perceived social support, stigmatization, social participation, or loneliness) adjusting for confounders (age, gender, and severity of psychopathology).

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Mitochondrial antiviral signaling protein (MAVS) is a crucial signaling adaptor in the sensing of positive-sense RNA viruses and the subsequent induction of the innate immune response. Coronaviruses have evolved multiple mechanisms to evade this response, amongst others, through their main protease (M), which is responsible for the proteolytic cleavage of the largest part of the viral replicase polyproteins pp1a and pp1ab. Additionally, it can cleave cellular substrates, such as innate immune signaling factors, to dampen the immune response.

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Background: Temstem is a smartphone app developed with and for clinical voice hearing individuals with the aim to reduce their voice hearing distress and improve social functioning.

Methods: A randomized controlled trial with adult outpatients suffering from distressing and frequent auditory verbal hallucinations (AVH) was conducted. Participants were randomized to unguided 'Temstem+AVH monitoring' or unguided 'AVH monitoring only' (control condition).

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Article Synopsis
  • Major Depressive Disorder often recurs, leading to increased disability and healthcare costs; this study evaluates the economic viability of Preventive Cognitive Therapy (PCT) compared to standard care for patients with recurrent depression who have remitted after Cognitive Behavioural Therapy.
  • A randomized trial involving 214 participants assessed health-related quality of life, depression-free days, healthcare use, and productivity losses over 15 months; results indicated PCT offered more depression-free days but at a higher societal cost.
  • While PCT showed potential benefits in terms of depression-free days, it was not deemed cost-effective overall, with limitations noted regarding the short follow-up period for assessing long-term outcomes.
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Deubiquitination of cellular substrates by viral proteases is a mechanism used to interfere with host cellular signaling processes, shared between members of the coronavirus- and arterivirus families. In the case of Arteriviruses, deubiquitinating and polyprotein processing activities are accomplished by the virus-encoded papain-like protease 2 (PLP2). Several studies have implicated the deubiquitinating activity of the porcine reproductive and respiratory syndrome virus (PRRSV) PLP2 in the downregulation of cellular interferon production, however to date, the only arterivirus PLP2 structure described is that of equine arteritis virus (EAV), a distantly related virus.

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Background: Vaccine hesitancy and lack of access remain major issues in disseminating COVID-19 vaccination to liver patients globally. Factors predicting poor response to vaccination and risk of breakthrough infection are important data to target booster vaccine programs. The primary aim of the current study was to measure humoral responses to 2 doses of COVID-19 vaccine.

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SARS-CoV-2 is the third zoonotic coronavirus to cause a major outbreak in humans in recent years, and many more SARS-like coronaviruses with pandemic potential are circulating in several animal species. Vaccines inducing T cell immunity against broadly conserved viral antigens may protect against hospitalization and death caused by outbreaks of such viruses. We report the design and preclinical testing of 2 T cell-based pan-sarbecovirus vaccines, based on conserved regions within viral proteins of sarbecovirus isolates of human and other carrier animals, like bats and pangolins.

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Article Synopsis
  • Vector-borne diseases, like those spread by mosquitoes, make up over 17% of infectious diseases around the world and may increase due to climate change.
  • Many mosquito-borne viruses (called arboviruses) can seriously harm humans and animals, with some causing major health issues.
  • Although there are a few vaccines for these viruses, most don’t have any, but scientists are working on new vaccine strategies that could help protect both people and animals from these diseases.
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Coronaviruses express a papain-like protease (PLpro) that is required for replicase polyprotein maturation and also serves as a deubiquitinating enzyme (DUB). In this study, using a Middle East respiratory syndrome virus (MERS-CoV) PLpro modified virus in which the DUB is selectively inactivated, we show that the PLpro DUB is an important MERS-CoV interferon antagonist and virulence factor. Although the DUB-negative rMERS-CoV replicates robustly in the lungs of human dipeptidyl peptidase 4 knock-in (hDPP4 KI) mice, it does not cause clinical symptoms.

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Positive-strand RNA viruses have been the cause of several recent outbreaks and epidemics, including the Zika virus epidemic in 2015, the SARS outbreak in 2003, and the ongoing SARS-CoV-2 pandemic. On June 18-22, 2022, researchers focusing on positive-strand RNA viruses met for the Keystone Symposium "Positive-Strand RNA Viruses" to share the latest research in molecular and cell biology, virology, immunology, vaccinology, and antiviral drug development. This report presents concise summaries of the scientific discussions at the symposium.

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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has made it clear that combating coronavirus outbreaks benefits from a combination of vaccines and therapeutics. A promising drug target common to all coronaviruses-including SARS-CoV, MERS-CoV, and SARS-CoV-2-is the papain-like protease (PLpro). PLpro cleaves part of the viral replicase polyproteins into non-structural protein subunits, which are essential to the viral replication cycle.

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Virus-specific cellular and humoral responses are major determinants for protection from critical illness after SARS-CoV-2 infection. However, the magnitude of the contribution of each of the components to viral clearance remains unclear. Here, we studied the timing of viral clearance in relation to 122 immune parameters in 102 hospitalised patients with moderate and severe COVID-19 in a longitudinal design.

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