Characteristics of viral pneumonia in the COVID-19 era: an update.

Influenza virus, rhinovirus, and adenovirus frequently cause viral pneumonia, an important cause of morbidity and mortality especially in the extreme ages of life. During the last two decades, three outbreaks of coronavirus-associated pneumonia, namely Severe Acute Respiratory Syndrome, Middle-East Respiratory Syndrome, and the ongoing Coronavirus Infectious Disease-2019 (COVID-19) were reported. The rate of diagnosis of viral pneumonia is increasingly approaching 60% among children identified as having community-acquired pneumonia (CAP). Clinical presentation ranges from mild to severe pneumonitis complicated by respiratory failure in severe cases. The most vulnerable patients, the elderly and those living with cancer, report a relevant mortality rate. No clinical characteristics can be useful to conclusively distinguish the different etiology of viral pneumonia. However, accessory symptoms, such as anosmia or ageusia together with respiratory symptoms suggest COVID-19. An etiologic-based treatment of viral pneumonia is possible in a small percentage of cases only. Neuraminidase inhibitors have been proven to reduce the need for ventilatory support and mortality rate while only a few data support the large-scale use of other antivirals. A low-middle dose of dexamethasone and heparin seems to be effective in COVID-19 patients, but data regarding their possible efficacy in viral pneumonia caused by other viruses are conflicting. In conclusion, viral pneumonia is a relevant cause of CAP, whose interest is increasing due to the current COVID-19 outbreak. To set up a therapeutic approach is difficult because of the low number of active molecules and the conflicting data bearing supportive treatments such as steroids.

Prenatal lens development in connexin43 and connexin50 double knockout mice.

PURPOSE: To determine the roles of intercellular communication in embryonic eye growth and development, mice with a targeted deletion of the Cx43 gene were examined, and mice without both Cx43 and Cx50 were generated and analyzed. METHODS: Embryonic eyes and lenses from wild-type mice, or mice deficient in Cx43, Cx50, or both Cx43 and Cx50 were collected and analyzed structurally by light and electron microscopy, immunohistochemically using connexin-specific antibodies, biochemically by Western blot analysis, and physiologically by measuring patterns of junctional communication revealed by iontophoretic injection of junction-permeable reporter molecules. RESULTS: Cx50 expression was limited to the ocular lens and was not detected in either the cornea or the retina. Cx43(-/-) embryos showed development of structurally normal lenses and eyes when examined by light and electron microscopy through embryonic day (E)18.5. In addition, Cx43(-/-) lenses synthesized four different markers of lens differentiation: MIP26, alphaA-crystallin, alphaB-crystallin, and gamma-crystallin. Double-knockout lenses were also histologically normal through E18.5 and synthesized the four lens differentiation markers. When assayed by intracellular injection with Lucifer yellow (Molecular Probes, Eugene, OR) and neurobiotin at E15.5, Cx43(-/-)/Cx50(-/-) lenses retained gap junction-mediated dye transfer between fiber cells. In contrast, dye transfer in double-knockout lenses was dramatically reduced between epithelial cells and was eliminated between epithelial cells and fibers. CONCLUSIONS: These data indicate that the unique functional properties of both Cx43 and Cx50 are not required for prenatal lens development and that connexin diversity is required for regulation of postnatal growth and homeostasis.

Lymphoproliferative disorder and imbalanced T-helper response in C/EBP beta-deficient mice.

C/EBP beta is considered a key element of interleukin-6 (IL-6) signalling as well as an important transcriptional regulator of the IL-6 gene itself. We describe here how mice lacking C/EBP beta develop a pathology similar to mice overexpressing IL-6 and nearly identical to multicentric Castleman's disease in human patients, with marked splenomegaly, peripheral lymphadenopathy and enhanced haemopoiesis. Humoral, innate and cellular immunity are also profoundly distorted, as shown by the defective activation of splenic macrophages, the strong impairement of IL-12 production, the increased susceptibility to Candida albicans infection and the altered T-helper function. Our data show that C/EBP beta is crucial for the correct functional regulation and homeostatic control of haemopoietic and lymphoid compartments.

Defective inflammatory response in interleukin 6-deficient mice.

Systemic and localized inflammation elicit a number of host responses which include fever, cachexia, hypoglycemia, and major changes in the concentration of liver plasma proteins. Interleukin 6 (IL-6) is considered an important mediator of the inflammatory response, together with IL-1 and tumor necrosis factor alpha (TNF-alpha). The purpose of this study was to unequivocally determine the role of IL-6 in these phenomena making use of IL-6-deficient mice that we have recently generated by gene targeting. We report here that in the absence of IL-6, mice are unable to mount a normal inflammatory response to localized tissue damage generated by turpentine injection. The induction of acute phase proteins is dramatically reduced, mice do not lose body weight and only suffer from mild anorexia and hypoglycemia. In contrast, when systemic inflammation is elicited through the injection of bacterial lipopolysaccharide (LPS), these parameters are altered to the same extent both in wild-type and IL-6-deficient mice, demonstrating that under these conditions IL-6 function is dispensable. Moreover, we show that LPS-treated IL-6-deficient mice produce three times more TNF-alpha than wild-type controls, suggesting that increased TNF-alpha production might be one of the compensatory mechanisms through which a normal response to LPS is achieved in the absence of IL-6. We also show that corticosterone is normally induced in IL-6-deficient mice, demonstrating that IL-6 is not required for the activation of the hypothalamic-pituitary-adrenal axis. Our results reinforce the idea that different patterns of cytokines are involved in systemic and localized tissue damage, and identify IL-6 as an essential mediator of the inflammatory response to localized inflammation.

Heterogeneity of microtubule organizing center components as revealed by monoclonal antibodies to mammalian centrosomes and to nucleus-associated bodies from dictyostelium.

The molecular composition of two morphologically distinct microtubule-organizing centers (MTOCs) was compared by probing with monoclonal antibodies raised against (i) nucleus-associated bodies (NABs) isolated in a complex with nuclei from the cellular slime mold Dictyostelium discoideum and (ii) mammalian mitotic spindles isolated from Chinese hamster ovary (CHO) cells. The staining patterns observed by immunofluorescence microscopy in whole CHO cells and Dictyostelium amoebae showed that the distribution of thirteen MTOC antigens is heterogeneous. Not all antibodies recognized the MTOC in both interphase and mitosis. Most of the anti-MTOC antibodies cross-reacted with other cellular organelles such as nuclei, Golgi apparatus-like aggregates and cytoskeletal elements. Two antibodies, CHO3 and AX3, recognized phosphorylated epitopes present in both mammalian centrosomes and Dictyostelium NABs. On immunoblots, most of the antibodies showed multiple bands, often of high molecular weight, indicating that the antigenic determinants are shared among different molecules. One antibody inhibited the regrowth of microtubules onto centrosomes in vitro after addition of exogenous tubulin to detergent-lysed CHO cells on coverslips; this antibody binds to an antigen(s) that might be essential for the microtubule-nucleating activity of centrosomes. These observations demonstrate that molecular components in different MTOCs exhibit a variety of distinct subcellular localizations and functional properties, and that some antigenic molecules have been conserved among morphologically distinct MTOCs.

A monoclonal antibody to a mitotic microtubule-associated protein blocks mitotic progression.

A monoclonal antibody raised against mitotic spindles isolated from CHO cells ([CHO1], Sellitto, C., and R. Kuriyama. 1988. J. Cell Biol. 106:431-439) identifies an epitope that resides on polypeptides of 95 and 105 kD and is localized in the spindles of diverse organisms. The antigen is distributed throughout the spindle at metaphase but becomes concentrated in a progressively narrower zone on either side of the spindle midplane as anaphase progresses. Microinjection of CHO1, either as an ascites fluid or as purified IgM, results in mitotic inhibition in a stage-specific and dose-dependent manner. Parallel control injections with nonimmune IgMs do not yield significant mitotic inhibition. Immunofluorescence analysis of injected cells reveals that those which complete mitosis display normal localization of CHO1, whereas arrested cells show no specific localization of the CHO1 antigen within the spindle. Immunoelectron microscopic images of such arrested cells indicate aberrant microtubule organization. The CHO1 antigen in HeLa cell extracts copurifies with taxol-stabilized microtubules. Neither of the polypeptides bearing the antigen is extracted from microtubules by ATP or GTP, but both are approximately 60% extracted with 0.5 M NaCl. Sucrose gradient analysis reveals that the antigens sediment at approximately 11S. The CHO 1 antigen appears to be a novel mitotic MAP whose proper distribution within the spindle is required for mitosis. The properties of the antigen(s) suggest that the corresponding protein(s) are part of the mechanism that holds the antiparallel microtubules of the two interdigitating half spindles together during anaphase.

Distribution of a matrix component of the midbody during the cell cycle in Chinese hamster ovary cells.

Monoclonal antibodies were raised against isolated spindles of CHO (Chinese hamster ovary) cells to probe for molecular components specific to the mitotic apparatus. One of the antibodies, CHO1, recognized an antigen localized to the midbody during mitosis. Immunofluorescence staining of metaphase cells showed that although the total spindle area was labeled faintly, the antigen corresponding to CHO1 was preferentially localized in the equatorial region of the spindle. With the progression of mitosis, the antigen was further organized into discrete short lines along the spindle axis, and eventually condensed into a bright fluorescent dot at the midzone of the intercellular bridge between two daughter cells. Parallel immunostaining of tubulin showed that the CHO1-stained area corresponded to the dark region where microtubules are entrapped by the amorphous dense matrix components and possibly blocked from binding to tubulin antibody. Immunoblot analysis indicated that CHO1 recognized two polypeptides of mol wt 95,000 and 105,000. The immunoreaction was always stronger in preparations of isolated midbodies than in mitotic spindle fractions. The protein doublet was retained in the particulate matrix fraction after Sarkosyl extraction (Mullins, J. M., and J. R. McIntosh. 1982. J. Cell Biol. 94:654-661), suggesting that CHO1 antigen is indeed a component of the dense matrix. In addition to the equatorial region of spindles and midbodies, CHO1 also stained interphase centrosomes, and nuclei in a speckled pattern that was cell cycle-dependent. Thus, the midbody appears to share either common molecular component(s) or a similar epitope with interphase centrosomes and nuclei.