Susceptibility to vaccinia virus infection and spread in mice is determined by age at infection, allergen sensitization and mast cell status

Investigation of the mutated antimicrobial peptides to inhibit ACE2, TMPRSS2 and GRP78 receptors of SARS-CoV-2 and angiotensin II type 1 receptor (AT1R) as well as controlling COVID-19 disease

SARS-CoV-2 is a global problem nowadays. Based on studies, some human receptors are involved in binding to SARS-CoV-2. Thus, the inhibition of these receptors can be effective in the treatment of Covid-19. Because of the proven benefits of antimicrobial peptides (AMPs) and the side effects of chemical drugs, they can be known as an alternative to recent medicines. RCSB PDB to obtain PDB id, StraPep and PhytAMP to acquire Bio-AMPs information and 3-D structure, and AlgPred, Toxinpred, TargetAntiAngio, IL-4pred, IL-6pred, ACPred and Hemopred databases were used to find the best score peptide features. HADDOCK 2.2 was used for molecular docking analysis, and UCSF Chimera software version 1.15, SWISS-MODEL and BIOVIA Discovery Studio Visualizer4.5 were used for mutation and structure modeling. Furthermore, MD simulation results were achieved from GROMACS 4.6.5. Based on the obtained results, the Moricin peptide was found to have the best affinity for ACE2. Moreover, Bacteriocin leucocin-A had the highest affinity for GRP78, Cathelicidin-6 had the best affinity for AT1R, and Bacteriocin PlnK had the best binding affinity for TMPRSS2. Additionally, Bacteriocin glycocin F, Bacteriocin lactococcin-G subunit beta and Cathelicidin-6 peptides were the most common compounds among the four receptors. However, these peptides also have some side effects. Consequently, the mutation eliminated the side effects, and MD simulation results indicated that the mutation proved the result of the docking analysis. The effect of AMPs on ACE2, GRP78, TMPRSS2 and AT1R receptors can be a novel treatment for Covid-19.Communicated by Ramaswamy H. Sarma.

Mast Cells Meet Cytomegalovirus: A New Example of Protective Mast Cell Involvement in an Infectious Disease

Cytomegaloviruses (CMVs) belong to the β-subfamily of herpesviruses. Their host-to-host transmission involves the airways. As primary infection of an immunocompetent host causes only mild feverish symptoms, human CMV (hCMV) is usually not considered in routine differential diagnostics of common airway infections. Medical relevance results from unrestricted tissue infection in an immunocompromised host. One risk group of concern are patients who receive hematopoietic cell transplantation (HCT) for immune reconstitution following hematoablative therapy of hematopoietic malignancies. In HCT patients, interstitial pneumonia is a frequent cause of death from hCMV strains that have developed resistance against antiviral drugs. Prevention of CMV pneumonia requires efficient reconstitution of antiviral CD8 T cells that infiltrate lung tissue. A role for mast cells (MC) in the immune control of lung infection by a CMV was discovered only recently in a mouse model. MC were shown to be susceptible for productive infection and to secrete the chemokine CCL-5, which recruits antiviral CD8 T cells to the lungs and thereby improves the immune control of pulmonary infection. Here, we review recent data on the mechanism of MC-CMV interaction, a field of science that is new for CMV virologists as well as for immunologists who have specialized in MC.

Moderate Susceptibility to Subcutaneous Plague (Yersinia pestis) Challenge in Vaccine-Treated and Untreated Sonoran Deer Mice (Peromyscus maniculatus sonoriensis) and Northern Grasshopper Mice (Onychomys leucogaster)

The variable response of wild mice to Yersinia pestis infection, the causative agent of plague, has generated much speculation concerning their role in the ecology of this potentially lethal disease. Researchers have questioned the means by which Y. pestis is maintained in nature and also sought methods for managing the disease. Here we assessed the efficacy of a new tool, the sylvatic plague vaccine (SPV), in wild-caught northern grasshopper mice (Onychomys leucogaster) and commercially acquired Sonoran deer mice (Peromyscus maniculatus sonoriensis). More than 40% of the animals survived a subcutaneous Y. pestis challenge of 175,000 colony forming units (over 30,000 times the white mouse 50% lethal dose) in both vaccine-treated and control groups. Our results indicate that SPV distribution is unlikely to protect adult mice from plague infection in field settings and corroborate the heterogeneous response to Y. pestis infection in mice reported by others.

Responses of Mast Cells to Pathogens: Beneficial and Detrimental Roles

Mast cells (MCs) are strategically located in tissues close to the external environment, being one of the first immune cells to interact with invading pathogens. They are long living effector cells equipped with different receptors that allow microbial recognition. Once activated, MCs release numerous biologically active mediators in the site of pathogen contact, which induce vascular endothelium modification, inflammation development and extracellular matrix remodeling. Efficient and direct antimicrobial mechanisms of MCs involve phagocytosis with oxidative and non-oxidative microbial destruction, extracellular trap formation, and the release of antimicrobial substances. MCs also contribute to host defense through the attraction and activation of phagocytic and inflammatory cells, shaping the innate and adaptive immune responses. However, as part of their response to pathogens and under an impaired, sustained, or systemic activation, MCs may contribute to tissue damage. This review will focus on the current knowledge about direct and indirect contribution of MCs to pathogen clearance. Antimicrobial mechanisms of MCs are addressed with special attention to signaling pathways involved and molecular weapons implicated. The role of MCs in a dysregulated host response that can increase morbidity and mortality is also reviewed and discussed, highlighting the complexity of MCs biology in the context of host-pathogen interactions.

Divergent Mast Cell Responses Modulate Antiviral Immunity During Influenza Virus Infection

Influenza A virus (IAV) is a respiratory pathogen that infects millions of people each year. Both seasonal and pandemic strains of IAV are capable of causing severe respiratory disease with a high risk of respiratory failure and opportunistic secondary infection. A strong inflammatory cytokine response is a hallmark of severe IAV infection. The widespread tissue damage and edema in the lung during severe influenza is largely attributed to an overexuberant production of inflammatory cytokines and cell killing by resident and infiltrating leukocytes. Mast cells (MCs) are a sentinel hematopoietic cell type situated at mucosal sites, including the lung. Poised to react immediately upon detecting infection, MCs produce a vast array of immune modulating molecules, including inflammatory cytokines, chemokines, and proteases. As such, MCs have been implicated as a source of the immunopathology observed in severe influenza. However, a growing body of evidence indicates that MCs play an essential role not only in inducing an inflammatory response but in suppressing inflammation as well. MC-derived immune suppressive cytokines are essential to the resolution of a number of viral infections and other immune insults. Absence of MCs prolongs infection, exacerbates tissue damage, and contributes to dissemination of the pathogen to other tissues. Production of cytokines such as IL-10 and IL-6 by MCs is essential for mitigating the inflammation and tissue damage caused by innate and adaptive immune cells alike. The two opposing functions of MCs—one pro-inflammatory and one anti-inflammatory—distinguish MCs as master regulators of immunity at the site of infection. Amongst the first cells to respond to infection or injury, MCs persist for the duration of the infection, modulating the recruitment, activation, and eventual suppression of other immune cells. In this review, we will discuss the immune modulatory roles of MCs over the course of viral infection and propose that the immune suppressive mediators produced by MCs are vital to minimizing immunopathology during influenza infection.

Mast Cell Responses to Viruses and Pathogen Products

Mast cells are well accepted as important sentinel cells for host defence against selected pathogens. Their location at mucosal surfaces and ability to mobilize multiple aspects of early immune responses makes them critical contributors to effective immunity in several experimental settings. However, the interactions of mast cells with viruses and pathogen products are complex and can have both detrimental and positive impacts. There is substantial evidence for mast cell mobilization and activation of effector cells and mobilization of dendritic cells following viral challenge. These cells are a major and under-appreciated local source of type I and III interferons following viral challenge. However, mast cells have also been implicated in inappropriate inflammatory responses, long term fibrosis, and vascular leakage associated with viral infections. Progress in combating infection and boosting effective immunity requires a better understanding of mast cell responses to viral infection and the pathogen products and receptors we can employ to modify such responses. In this review, we outline some of the key known responses of mast cells to viral infection and their major responses to pathogen products. We have placed an emphasis on data obtained from human mast cells and aim to provide a framework for considering the complex interactions between mast cells and pathogens with a view to exploiting this knowledge therapeutically. Long-lived resident mast cells and their responses to viruses and pathogen products provide excellent opportunities to modify local immune responses that remain to be fully exploited in cancer immunotherapy, vaccination, and treatment of infectious diseases.

Impact of Sylvatic Plague Vaccine on Non-target Small Rodents in Grassland Ecosystems

Oral vaccination is an emerging management strategy to reduce the prevalence of high impact infectious diseases within wild animal populations. Plague is a flea-borne zoonosis of rodents that often decimates prairie dog (Cynomys spp.) colonies in the western USA. Recently, an oral sylvatic plague vaccine (SPV) was developed to protect prairie dogs from plague and aid recovery of the endangered black-footed ferret (Mustela nigripes). Although oral vaccination programs are targeted toward specific species, field distribution of vaccine-laden baits can result in vaccine uptake by non-target animals and unintended indirect effects. We assessed the impact of SPV on non-target rodents at paired vaccine and placebo-treated prairie dog colonies in four US states from 2013 to 2015. Bait consumption by non-target rodents was high (70.8%, n = 3113), but anti-plague antibody development on vaccine plots was low (23.7%, n = 266). In addition, no significant differences were noted in combined deer mice (Peromyscus maniculatus) and western harvest mouse (Reithrodontomys megalotis) abundance or community evenness and richness of non-target rodents between vaccine-treated and placebo plots. In our 3-year field study, we could not detect a significant positive or negative effect of SPV application on non-target rodents.

Both CD8+ and CD4+ T Cells Contribute to Corneal Clouding and Viral Clearance following Vaccinia Virus Infection in C57BL/6 Mice

Vaccinia virus (VACV) keratitis is a serious complication following smallpox vaccination and can lead to blindness. The pathological mechanisms involved in ocular VACV infection are poorly understood. Previous studies have used rabbits, but the lack of immune reagents and transgenic or knockout animals makes them less suitable for mechanistic studies. We report that infection of C57BL/6 mice with 1 × 10(7) PFU of vaccinia virus strain WR results in blepharitis, corneal neovascularization, and stromal keratitis. The DryVax strain of VACV was completely attenuated. Infection required corneal scarification and replication-competent virus, and the severity of ocular disease was similar in 4- to 6-week-old and 1-year-old mice. Viral titers peaked at approximately 1 × 10(6) PFU on day 5 postinfection, and virus had not cleared by day 13 postinfection. Neutrophils were found in the peripheral cornea on day 1 after infection and then declined, followed by infiltration of both CD4(+) and CD8(+) T cells, which remained peripheral throughout the infection. Blood vessel growth extended 2 to 5 mm into the cornea from the limbus. Infection of CD4(-/-), CD8(-/-), or antibody-depleted mice resulted in similar disease severity and corneal clouding, indicating that both T-cell subsets were involved in the immunopathological response. Depletion of both CD4(+) and CD8(+) T cells resulted in significantly more severe disease and failure to clear the virus. On the basis of our results, the pathology of VACV keratitis is significantly different from that of herpes simplex virus keratitis. Further studies are likely to reveal novel information regarding virulence and immune responses to viral ocular infection.

IMPORTANCE

Potentially blinding eye infections can occur after vaccination for smallpox. Very little is known about the pathological mechanisms that are involved, and the information that is available was generated using rabbit models. The lack of immunological reagents for rabbits makes such studies difficult. We characterized a mouse model of vaccinia virus ocular disease using C57BL/6 mice and strain WR and show that both CD4(+) and CD8(+) T-cell subsets play a role in the blinding eye disease and in controlling virus replication. On the basis of these results, vaccinia virus keratitis is significantly different from herpes simplex virus keratitis, and further studies using this model should generate novel insights into immunopathological responses to viral ocular infection.

Cationic host defense peptides; novel antimicrobial therapeutics against Category A pathogens and emerging infections

Cationic Host Defense Peptides (HDP, also known as antimicrobial peptides) are crucial components of the innate immune system and possess broad-spectrum antibacterial, antiviral, and immunomodulatory activities. They can contribute to the rapid clearance of biological agents through direct killing of the organisms, inhibition of pro-inflammatory mediators such as lipopolysaccharide, and by modulating the inflammatory response to infection. Category A biological agents and materials, as classified by the United States National Institutes for Health, the US Centers for Disease Control and Prevention, and the US Department of Homeland Security, carry the most severe threat in terms of human health, transmissibility, and preparedness. As such, there is a pressing need for novel frontline approaches for prevention and treatment of diseases caused by these organisms, and exploiting the broad antimicrobial activity exhibited by cationic host defense peptides represents an exciting priority area for clinical research. This review will summarize what is known about the antimicrobial and antiviral effects of the two main families of cationic host defense peptides, cathelicidins, and defensins in the context of Category A biological agents which include, but are not limited to; anthrax (Bacillus anthracis), plague (Yersinia pestis), smallpox (Variola major), tularemia (Francisella tularensis). In addition, we highlight priority areas, particularly emerging viral infections, where more extensive research is urgently required.

Locally Produced IL-10 Limits Cutaneous Vaccinia Virus Spread

Skin infection with the poxvirus vaccinia (VV) elicits a powerful, inflammatory cellular response that clears virus infection in a coordinated, spatially organized manner. Given the high concentration of pro-inflammatory effectors at areas of viral infection, it is unclear how tissue pathology is limited while virus-infected cells are being eliminated. To better understand the spatial dynamics of the anti-inflammatory response to a cutaneous viral infection, we first screened cytokine mRNA expression levels after epicutaneous (ec.) VV infection and found a large increase the anti-inflammatory cytokine IL-10. Ex vivo analyses revealed that T cells in the skin were the primary IL-10-producing cells. To understand the distribution of IL-10-producing T cells in vivo, we performed multiphoton intravital microscopy (MPM) of VV-infected mice, assessing the location and dynamic behavior of IL-10 producing cells. Although virus-specific T cells were distributed throughout areas of the inflamed skin lacking overt virus-infection, IL-10+ cells closely associated with large keratinocytic foci of virus replication where they exhibited similar motility patterns to bulk antigen-specific CD8+ T cells. Paradoxically, neutralizing secreted IL-10 in vivo with an anti-IL-10 antibody increased viral lesion size and viral replication. Additional analyses demonstrated that IL-10 antibody administration decreased recruitment of CCR2+ inflammatory monocytes, which were important for reducing viral burden in the infected skin. Based upon these findings, we conclude that spatially concentrated IL-10 production limits cutaneous viral replication and dissemination, likely through modulation of the innate immune repertoire at the site of viral growth.

Age at Vaccination May Influence Response to Sylvatic Plague Vaccine (SPV) in Gunnison's Prairie Dogs (Cynomys gunnisoni)

Gunnison's prairie dogs (Cynomys gunnisoni) have been considered at greater risk from Yersinia pestis (plague) infection in the montane portion of their range compared to populations at lower elevations, possibly due to factors related to flea transmission of the bacteria or greater host susceptibility. To test the latter hypothesis and determine whether vaccination against plague with an oral sylvatic plague vaccine (SPV) improved survival, we captured prairie dogs from a C. g. gunnisoni or "montane" population and a C. g. zuniensis or "prairie" population for vaccine efficacy and challenge studies. No differences (P = 0.63) were found in plague susceptibility in non-vaccinated animals between these two populations; however, vaccinates from the prairie population survived plague challenge at significantly higher rates (P < 0.01) than those from the montane population. Upon further analysis, we determined that response to immunization was most likely associated with differences in age, as the prairie group was much younger on average than the montane group. Vaccinates that were juveniles or young adults survived plague challenge at a much higher rate than adults (P < 0.01 and P = 0.02, respectively), but no difference (P = 0.83) was detected in survival rates between control animals of different ages. These results suggest that host susceptibility is probably not related to the assumed greater risk from plague in the C. g. gunnisoni or "montane" populations of Gunnison's prairie dogs, and that SPV could be a useful plague management tool for this species, particularly if targeted at younger cohorts.

Mast cells and influenza a virus: association with allergic responses and beyond

Influenza A virus (IAV) is a widespread infectious agent commonly found in mammalian and avian species. In humans, IAV is a respiratory pathogen that causes seasonal infections associated with significant morbidity in young and elderly populations, and has a large economic impact. Moreover, IAV has the potential to cause both zoonotic spillover infection and global pandemics, which have significantly greater morbidity and mortality across all ages. The pathology associated with these pandemic and spillover infections appear to be the result of an excessive inflammatory response leading to severe lung damage, which likely predisposes the lungs for secondary bacterial infections. The lung is protected from pathogens by alveolar epithelial cells, endothelial cells, tissue resident alveolar macrophages, dendritic cells, and mast cells. The importance of mast cells during bacterial and parasitic infections has been extensively studied; yet, the role of these hematopoietic cells during viral infections is only beginning to emerge. Recently, it has been shown that mast cells can be directly activated in response to IAV, releasing mediators such histamine, proteases, leukotrienes, inflammatory cytokines, and antiviral chemokines, which participate in the excessive inflammatory and pathological response observed during IAV infections. In this review, we will examine the relationship between mast cells and IAV, and discuss the role of mast cells as a potential drug target during highly pathological IAV infections. Finally, we proposed an emerging role for mast cells in other viral infections associated with significant host pathology.