Are fish immunocompetent enough to face climate change?

Ongoing climate change has already been associated with increased disease outbreaks in wild and farmed fish. Here, we evaluate the current knowledge of climate change-related ecoimmunology in teleosts with a focus on temperature, hypoxia, salinity and acidification before exploring interactive effects of multiple stressors. Our literature review reveals that acute and chronic changes in temperature and dissolved oxygen can compromise fish immunity which can lead to increased disease susceptibility. Moreover, temperature and hypoxia have already been shown to enhance the infectivity of certain pathogens/parasites and to accelerate disease progression. Too few studies exist that have focussed on acidification, but direct immune effects seem to be limited while salinity studies have led to contrasting results. Likewise, multi-stressor experiments essential for unravelling the interactions of simultaneously changing environmental factors are still scarce. This ultimately impedes our ability to estimate to what extent climate change will hamper fish immunity. Our review about epigenetic regulation mechanisms highlights the acclimation potential of the fish immune response to changing environments. However, due to the limited number of epigenetic studies, overarching conclusions cannot be drawn. Finally, we provide an outlook on how to better estimate the effects of realistic climate change scenarios in future immune studies in fish.

Juvenile Atlantic herring (Clupea harengus) use a time-compensated sun compass for orientation.

Atlantic herring (Clupea harengus), an ecologically and economically important species in the northern hemisphere, shows pronounced seasonal migratory behaviour. To follow distinctive migration patterns over hundreds of kilometers between feeding, overwintering and spawning grounds, they are probably guided by orientation mechanisms. We tested whether juvenile spring-spawning Atlantic herring, caught in the western Baltic, use a sun compass for orientation just before they start leaving their hatching area. Fish were randomly divided into two groups, one of them clock-shifted 6 h backwards, to investigate whether they shift their orientation direction accordingly. Individual fish were placed in a circular bowl and their orientation was tested multiple times with the sun as a sole visual orientational cue. Our results show for the first time that juvenile Atlantic herring use a time-compensated sun compass during their migration. Their swimming direction was impaired, but still present, even when the sky was very cloudy, indicating additional orientation capabilities.

Transmission of SARS-CoV-2 among children and staff in German daycare centres.

In daycare centres, the close contact of children with other children and employees favours the transmission of infections. The majority of children <6 years attend daycare programmes in Germany, but the role of daycare centres in the SARS-CoV-2 pandemic is unclear. We investigated the transmission risk in daycare centres and the spread of SARS-CoV-2 to associated households. 30 daycare groups with at least one recent laboratory-confirmed SARS-CoV-2 case were enrolled in the study (10/2020-06/2021). Close contact persons within daycare and households were examined over a 12-day period (repeated SARS-CoV-2 PCR tests, genetic sequencing of viruses, symptom diary). Households were interviewed to gain comprehensive information on each outbreak. We determined primary cases for all daycare groups. The number of secondary cases varied considerably between daycare groups. The pooled secondary attack rate (SAR) across all 30 daycare centres was 9.6%. The SAR tended to be higher when the Alpha variant was detected (15.9% vs. 5.1% with evidence of wild type). The household SAR was 53.3%. Exposed daycare children were less likely to get infected with SARS-CoV-2 than employees (7.7% vs. 15.5%). Containment measures in daycare programmes are critical to reduce SARS-CoV-2 transmission, especially to avoid spread to associated households.

[Symptoms of SARS-CoV-2 infections in children of day care age]. / Symptomatik einer akuten SARS-CoV-2-Infektion bei Kindern im Kita-Alter.

Background: The symptoms of SARS-CoV­2 infections in children are mostly mild; however, the symptoms are highly variable. There are only a few studies on non-hospitalized children. The clinical picture described in hospitalized children cannot be transferred to non-hospitalized children and the frequency of certain symptoms in children may thus be overestimated. Furthermore, most studies include a broad age group (up to 18 years). The symptoms of younger children have so far been described in less detail. Objective: The paper aims to describe the frequency of COVID-19 symptoms in younger children (1-6 years old). Data of the two modules COALA (Corona: Anlassbezogene Untersuchungen in Kitas) and CATS (Corona-KiTa surveillance) of the Corona-KiTa study are evaluated and the results of the two studies are compared and discussed against the background of the different methodologies. In the COALA study, the type and frequency of symptoms of children infected with SARS-CoV­2 are evaluated and compared to symptoms of children who tested negative for SARS-CoV­2. Symptom frequencies of SARS-CoV­2 infected children of the COALA study are compared with data collected from surveillance data (CATS). Material and methods: The COALA study investigated 30 SARS-CoV­2 outbreaks in day care centers where at least 1 SARS-CoV­2 case was reported between October 2020 and June 2021. Using a prospective study design, day care children who were infected with SARS-CoV­2 and their contact persons were studied over a period of 12 days (including regular SARS-CoV­2 testing, retrospective interviews and daily symptom reporting). The results from the COALA study were compared with data from COVID-19 surveillance cases (CATS) for the same age group and time period. In Germany, SARS-CoV­2 cases are reported to the local health authorities by physicians and laboratories. When reporting cases symptoms can be reported as well. Results: From the COALA study, interview and reported symptom data were available for 289 children from the participating day care centers. Of 39 children with a SARS-CoV­2 infection (wild-type, α­variant), 64% had at least 1 symptom; of the children who tested negative for SARS-CoV­2, 40% had at least 1 symptom. In both groups, rhinitis was the most common symptom (36% vs. 25%, n. s.). From the surveillance data (CATS), clinical information was available for 84,371 SARS-CoV­2 positive children; fever was most common (27%) along with rhinitis (26%). Severe symptoms such as dyspnea were rarely reported in the outbreak investigations and in the surveillance data (3% and 1%, respectively). Conclusion: Day care-aged children infected with SARS-CoV­2 usually have mild or asymptomatic courses. Their symptoms are similar to those of children who tested negative for SARS-CoV­2 from the same day care centers; thus, the observed COVID-19 symptoms are nonspecific. Combining data from the two modules is useful: findings from a very large database, as provided by the surveillance data, are complemented by findings from day care center outbreaks, where detailed prospective data on infected children can be compared with those of children who tested negative for SARS-CoV­2.

Development of a System for Additive Manufacturing of Ceramic Matrix Composite Structures Using Laser Technology.

Ceramic matrix composites (CMCs) are refractory ceramic materials with damage-tolerant behavior. Coming from the space industry, this class of materials is increasingly being used in other applications, such as automotive construction for high-performance brake discs, furnace technology, heat coatings for pipe systems and landing flaps on reusable rocket sections. In order to produce CMC faster and more cost-efficiently for the increasing demand, a new additive manufacturing process is being tested, which in the future should also be able to realize material joints and higher component wall thicknesses than conventional processes. The main features of the process are as follows. A ceramic fiber bundle is de-sized and infiltrated with ceramic suspension. The bundle infiltrated with matrix material is dried and then applied to a body form. During application, the matrix material is melted by laser radiation without damaging the fiber material. For the initial validation of the material system, samples are pressed and analyzed for their absorption properties using integrating sphere measurement. With the results, a suitable processing laser is selected, and initial melting tests of the matrix system are carried out. After the first validation of the process, a test system is set up, and the first test specimens are produced to determine the material parameters.

Poly-ß-hydroxybutyrate administration during early life: effects on performance, immunity and microbial community of European sea bass yolk-sac larvae.

The reliable production of marine fish larvae is one of the major bottlenecks in aquaculture due to high mortalities mainly caused by infectious diseases. To evaluate if the compound poly-ß-hydroxybutyrate (PHB) might be a suitable immunoprophylactic measure in fish larviculture, its capacity to improve immunity and performance in European sea bass (Dicentrarchus labrax) yolk-sac larvae was explored. PHB was applied from mouth opening onwards to stimulate the developing larval immune system at the earliest possible point in time. Larval survival, growth, microbiota composition, gene expression profiles and disease resistance were assessed. PHB administration improved larval survival and, furthermore, altered the larva-associated microbiota composition. The bacterial challenge test using pathogenic Vibrio anguillarum revealed that the larval disease resistance was not influenced by PHB. The expression profiles of 26 genes involved e.g. in the immune response showed that PHB affected the expression of the antimicrobial peptides ferritin (fer) and dicentracin (dic), however, the response to PHB was inconsistent and weaker than previously demonstrated for sea bass post-larvae. Hence, the present study highlights the need for more research focusing on the immunostimulation of different early developmental stages for gaining a more comprehensive picture and advancing a sustainable production of high quality fry.

Laser-assisted cholesteatoma surgery: technical aspects, in vitro implementation and challenge of selective cell destruction.

Cholesteatoma is a destructive ear condition requiring complete surgical removal. One major problem lies in the frequent occurrence of residual cholesteatoma caused by squamous epithelium remaining in the middle ear. Our aim is to develop a laser treatment that is selectively directed against residual cholesteatoma cells and can be performed after cholesteatoma surgery in the same session. In a first trial, we studied the photodynamic effect of argon (AL) and diode lasers (DL) on cholesteatoma tissue. Intraoperatively harvested monolayer-cultured cholesteatoma cells were stained in vivo with different absorption enhancers: neutral red (NR), fluorescein diacetate (FDA), and indocyanine green (ICG). In vitro, staining tests on enhanced cellular dye absorption and laser tests were followed by cytotoxicity measurements to determine the respective amount of damage. To achieve selective cell destruction, antibody-mediated staining of cholesteatoma and middle ear mucosa cells was examined in a second trial. Cell cultures (cytospin and coverglass growing) and paraffin-embedded cholesteatoma tissue sections were studied immunohistochemically to determine the binding of monoclonal mouse antibodies against human cytokeratins CK5, CK10, CK14 and the epidermal growth factor receptor EGFR. Intracellular staining with absorption enhancers increased the optical density at the wavelength corresponding to the dye. Staining and subsequent laser irradiation destroyed up to 92% of cultured cholesteatoma cells. Unstained irradiated tissue was not affected. In cytospins, the antibody against CK5/6 showed strong staining of cholesteatoma and weak staining of mucosa cells. Reactivity for CK14 and EGFR was positive in both tissues. In coverglass cultures, staining of cholesteatoma cells was positive for CK5/6, CK14 and EGFR. Mucosa cells were positive for EGFR but negative for cytokeratins. Both cell types were negative for CK10. In embedded cholesteatoma tissue, CK5/6 and CK14 were localized in the basal layers of the matrix, while CK10 was situated in the suprabasal layers, and EGFR was present in all layers of the matrix and perimatrix. As for the technical aspects of laser-assisted cholesteatoma surgery, AL and DL have proved to be suitable devices; ICG and FDA are effective nontoxic absorption enhancers. The investigated antibodies against cytokeratins and EGFR show nonselective staining and thus appear to be inappropriate for avoiding unwanted cell damage. For safe and specific intraoperative application to intact tissue, the chromophore should be coupled to a particular antibody that binds solely to an easily accessible specific antigen at the surface of cholesteatoma cells.