Myeloid Cells Restrict MCMV and Drive Stress-Induced Extramedullary Hematopoiesis through STAT1

Cytomegalovirus (CMV) has a high prevalence worldwide, is often fatal for immunocompromised patients, and causes bone marrow suppression. Deficiency of signal transducer and activator of transcription 1 (STAT1) results in severely impaired antiviral immunity. We have used cell-type restricted deletion of Stat1 to determine the importance of myeloid cell activity for the defense against murine CMV (MCMV). We show that myeloid STAT1 limits MCMV burden and infection-associated pathology in the spleen but does not affect ultimate clearance of infection. Unexpectedly, we found an essential role of myeloid STAT1 in the induction of extramedullary hematopoiesis (EMH). The EMH-promoting function of STAT1 was not restricted to MCMV infection but was also observed during CpG oligodeoxynucleotide-induced sterile inflammation. Collectively, we provide genetic evidence that signaling through STAT1 in myeloid cells is required to restrict MCMV at early time points post-infection and to induce compensatory hematopoiesis in the spleen

TYK2 Kinase Activity Is Required for Functional Type I Interferon Responses In Vivo

Tyrosine kinase 2 (TYK2) is a member of the Janus kinase (JAK) family and is involved in cytokine signalling. In vitro analyses suggest that TYK2 also has kinase-independent, i.e., non-canonical, functions. We have generated gene-targeted mice harbouring a mutation in the ATP-binding pocket of the kinase domain. The Tyk2 kinase-inactive (Tyk2K923E) mice are viable and show no gross abnormalities. We show that kinase-active TYK2 is required for full-fledged type I interferon- (IFN) induced activation of the transcription factors STAT1-4 and for the in vivo antiviral defence against viruses primarily controlled through type I IFN actions. In addition, TYK2 kinase activity was found to be required for the protein’s stability. An inhibitory function was only observed upon over-expression of TYK2K923E in vitro. Tyk2K923E mice represent the first model for studying the kinase-independent function of a JAK in vivo and for assessing the consequences of side effects of JAK inhibitors

Effect of Different Ambient Temperatures on Reproductive Outcome and Stress Level of Lactating Females in Two Mouse Strains

Ambient temperature is an important non-biotic environmental factor influencing immunological and oncological parameters in laboratory mice. It is under discussion which temperature is more appropriate and whether the commonly used room temperature in rodent facilities of about 21 °C represents a chronic cold stress or the 30 °C of the thermoneutral zone constitutes heat stress for the animals. In this study, we selected the physiological challenging period of lactation to investigate the influence of a cage temperature of 20 °C, 25 °C, and 30 °C, respectively, on reproductive performance and stress hormone levels in two frequently used mouse strains. We found that B6D2F1 hybrid mothers weaned more pups compared to C57BL/6N mothers, and that the number of weaned pups was reduced when mothers of both strains were kept at 30 °C. Furthermore, at 30 °C, mothers and pups showed reduced body weight at weaning and offspring had longer tails. Despite pronounced temperature effects on reproductive parameters, we did not find any temperature effects on adrenocortical activity in breeding and control mice. Independent of the ambient temperature, however, we found that females raising pups showed elevated levels of faecal corticosterone metabolites (FCMs) compared to controls. Peak levels of stress hormone metabolites were measured around birth and during the third week of lactation. Our results provide no evidence of an advantage for keeping lactating mice in ambient temperatures near the thermoneutral zone. In contrast, we found that a 30 °C cage temperature during lactation reduced body mass in females and their offspring and declined female reproductive performance

Deciphering Host Genotype-Specific Impacts on the Metabolic Fingerprint of <i>Listeria monocytogenes</i> by FTIR Spectroscopy

<div><p>Bacterial pathogens are known for their wide range of strategies to specifically adapt to host environments and infection sites. An in-depth understanding of these adaptation mechanisms is crucial for the development of effective therapeutics and new prevention measures. In this study, we assessed the suitability of Fourier Transform Infrared (FTIR) spectroscopy for monitoring metabolic adaptations of the bacterial pathogen <i>Listeria monocytogenes</i> to specific host genotypes and for exploring the potential of FTIR spectroscopy to gain novel insights into the host-pathogen interaction. Three different mouse genotypes, showing different susceptibility to <i>L. monocytogenes</i> infections, were challenged with <i>L. monocytogenes</i> and re-isolated bacteria were subjected to FTIR spectroscopy. The bacteria from mice with different survival characteristics showed distinct IR spectral patterns, reflecting specific changes in the backbone conformation and the hydrogen-bonding pattern of the protein secondary structure in the bacterial cell. Coupling FTIR spectroscopy with chemometrics allowed us to link bacterial metabolic fingerprints with host infection susceptibility and to decipher longtime memory effects of the host on the bacteria. After prolonged cultivation of host-passaged bacteria under standard laboratory conditions, the host's imprint on bacterial metabolism vanished, which suggests a revertible metabolic adaptation of bacteria to host environment and loss of host environment triggered memory effects over time. In summary, our work demonstrates the potential and power of FTIR spectroscopy to be used as a fast, simple and highly discriminatory tool to investigate the mechanism of bacterial host adaptation on a macromolar and metabolic level.</p></div

Host imprint on mice passaged <i>L. monocytogenes</i> isolates monitored be FTIR spectroscopy.

<p>LDA was carried out on second derivative, vector-normalized FTIR spectra from <i>L. monocytogenes</i> re-isolated from challenged 129/Sv (X), Tyk2−/− (O) and C57BL/6 (+) mice derived from the two independent experiments.</p

Potential host memory effects on mice passaged <i>L. monocytogenes</i> isolates monitored by FTIR spectroscopy.

<p>PCA on second derivative, vector-normalized FTIR spectra from <i>L. monocytogenes</i> isolates derived from challenged 129/Sv (X), Tyk2−/− (O) and C57BL/6 (+) mice from one representative experiment (A) directly after passage in mice and after consecutive sub-cultivations at 37°C on laboratory standard media for one week (B) and for 6 weeks (C).</p

FTIR spectra of <i>L. monocytogenes</i> re-isolated from challenged mice.

<p>(A) Average FTIR spectra derived from 129/Sv (dotted), Tyk2−/− (dashed) and C57BL/6 (solid) isolates are shown from the whole spectral range (B) Subtraction spectra were generated from second derivative, vector-normalized, average FTIR spectra of the three different mouse genotypes. Spectra from C57BL/6 mice were subtracted from 129/Sv isolates (black), spectra from C57BL/6 mice were subtracted from Tyk2−/− (red) and spectra from Tyk2−/− were subtracted from 129/Sv isolates (blue). Most pronounced differences were observed in the spectral range of 1700–1500 cm⁻¹ (protein region) and can be assigned to amide I (1670–1625 cm⁻¹) and amide II (1560–1530 cm⁻¹).</p

ANOVA-pairwise comparison to assess significant differentiation among the three genotypes (<i>p</i>-values).

<p>ANOVA-pairwise comparison to assess significant differentiation among the three genotypes (<i>p</i>-values).</p