Antimicrobial peptides (AMPs) are found widely distributed through Nature, and participate in the innate host defense of each species. Fish are a great source of these peptides, as they express all of the major classes of AMPs, including defensins, cathelicidins, hepcidins, histone-derived peptides, and a fish-specific class of the cecropin family, called piscidins. As with other species, the fish peptides exhibit broad-spectrum antimicrobial activity, killing both fish and human pathogens. They are also immunomodulatory, and their genes are highly responsive to microbes and innate immuno-stimulatory molecules. Recent research has demonstrated that some of the unique properties of fish peptides, including their ability to act even in very high salt concentrations, make them good potential targets for development as therapeutic antimicrobials. Further, the stimulation of their gene expression by exogenous factors could be useful in preventing pathogenic microbes in aquaculture.

Morphological switch is tightly coupled with the pathogenesis of many dimorphic fungal pathogens. Cryptococcus neoformans, the major causative agent of cryptococcal meningitis, mostly presents as the yeast form but is capable of switching to the hyphal form. The filamentous form has long been associated with attenuated virulence, yet the underlying mechanism remains elusive. We previously identified the master regulator Znf2 that controls the yeast-to-hypha transition in Cryptococcus. Activation of Znf2 promotes hyphal formation and abolishes fungal virulence in vivo. Here we demonstrated that the cryptococcal strain overexpressing ZNF2 elicited strong and yet temporally confined proinflammatory responses in the early stage of infection. In contrast, exacerbated inflammation in mice infected with the wild-type (WT) strain showed that they were unable to control the infection. Animals inoculated with this filamentous Cryptococcus strain had fewer pulmonary eosinophils and CD11c+ CD11b+ cells than animals inoculated with WT yeast. Moreover, mice infected with this strain developed protective Th1- or Th17-type T cell responses. These findings suggest that the virulence attenuation of the filamentous form is likely due to its elicitation of protective host responses. The antivirulence effect of Znf2 was independent of two previously identified factors downstream of Znf2. Interestingly, mucosal immunizations with high doses of ZNF2-overexpressing cells, either in the live or heat-killed form, offered 100% protection to the host from a subsequent challenge with the otherwise lethal clinical strain H99. Our results demonstrate that heat-resistant cellular components presented in cryptococcal cells with activated ZNF2 elicit protective host immune responses. These findings could facilitate future research on novel immunological therapies.

Background Increased inflammation has been well defined in COVID-19, while definitive pathways driving severe forms of this disease remain uncertain. Neutrophils are known to contribute to immunopathology in infections, inflammatory diseases and acute respiratory distress syndrome (ARDS), a primary cause of morbidity and mortality in COVID-19. Changes in neutrophil function in COVID-19 may give insight into disease pathogenesis and identify therapeutic targets. Methods Blood was obtained serially from critically ill COVID-19 patients for eleven days. Neutrophil extracellular trap formation (NETosis), oxidative burst, phagocytosis and cytokine levels were assessed. Lung tissue was obtained immediately post-mortem for immunostaining. Pubmed searches for neutrophils, lung and COVID-19 yielded ten peer-reviewed research articles in English. Results Elevations in neutrophil-associated cytokines IL-8 and IL-6, and general inflammatory cytokines IP-10, GM-CSF, IL-1b, IL-10 and TNF, were identified both at first measurement and across hospitalization (p<0.0001). COVID neutrophils had exaggerated oxidative burst (p<0.0001), NETosis (p<0.0001) and phagocytosis (p<0.0001) relative to controls. Increased NETosis correlated with leukocytosis and neutrophilia, and neutrophils and NETs were identified within airways and alveoli in lung parenchyma of 40% of SARS-CoV-2 infected lungs available for examination (2 out of 5). While elevations in IL-8 and ANC correlated with disease severity, plasma IL-8 levels alone correlated with death. Conclusions Literature to date demonstrates compelling evidence of increased neutrophils in the circulation and lungs of COVID-19 patients. importantly, neutrophil quantity and activation correlates with severity of disease. Similarly, our data shows that circulating neutrophils in COVID-19 exhibit an activated phenotype with enhanced NETosis and oxidative burst.

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