PANoptosis in microbial infection

The immune system has evolved multiple mechanisms to restrict microbial infections and regulate inflammatory responses. Without appropriate regulation, infection-induced inflammatory pathology can be deadly. The innate immune system recognizes the microbial molecules conserved in many pathogens and engages a rapid response by producing inflammatory mediators and activating programmed cell death pathways, including pyroptosis, apoptosis, and necroptosis. Activation of pattern recognition receptors, in combination with inflammatory cytokine-induced signaling through death domain-containing receptors, initiates a highly interconnected cell death process called PANoptosis (pyroptosis, apoptosis, necroptosis). Broadly speaking, PANoptosis is critical for restricting a wide range of pathogens (including bacteria, viruses, fungi, and parasites), which we describe in this review. We propose that re-examining the role of cell death and inflammatory cytokines through the lens of PANoptosis will advance our understanding of host-pathogen evolution and may reveal new treatment strategies for controlling a wide range of infectious diseases.

Coronavirus disease 2019-Historical context, virology, pathogenesis, immunotherapy, and vaccine development

The current Coronavirus Disease 2019 (COVID-19) pandemic is causing great alarm around the world. The pathogen for COVID-19 - severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) - is the seventh known coronavirus to cause pneumonia in humans. While much remains unknown about SARS-CoV-2, physicians and researchers have begun to publish relevant findings, and much evidence is available on coronaviruses previously circulating in human and animal populations. In this review, we situate COVID-19 in its context as a transboundary viral disease, and provide a comprehensive discussion focused on the discovery, spread, virology, pathogenesis, and clinical features of this disease, its causative coronaviral pathogen, and approaches to combating the disease through immunotherapies and other treatments and vaccine development. An epidemiological survey revealed a potentially large number of asymptomatic SARS-CoV-2 carriers within the population, which may hamper efforts against COVID-19. Finally, we emphasize that vaccines against SARS-CoV-2, which may be developed by 2021, will be essential for prevention of COVID-19.

Human monoclonal antibodies as candidate therapeutics against emerging viruses

The emergence of new pathogens, such as severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and Ebola virus, poses serious challenges to global public health and highlights the urgent need for novel antiviral approaches. Monoclonal antibodies (mAbs) have been successfully used to treat various diseases, particularly cancer and immunological disorders. Antigen-specific mAbs have been isolated using several different approaches, including hybridoma, transgenic mice, phage display, yeast display, and single B-cell isolation. Consequently, an increasing number of mAbs, which exhibit high potency against emerging viruses in vitro and in animal models of infection, have been developed. In this paper, we summarize historical trends and recent developments in mAb discovery, compare the advantages and disadvantages of various approaches to mAb production, and discuss the potential use of such strategies for the development of antivirals against emerging diseases. We also review the application of recently developed human mAbs against SARS-CoV, MERS-CoV, and Ebola virus and discuss prospects for the development of mAbs as therapeutic agents against emerging viral diseases.

Universal influenza virus vaccines: what can we learn from the human immune response following exposure to H7 subtype viruses?

Several universal influenza virus vaccine candidates based on eliciting antibodies against the hemagglutinin stalk domain are in development. Typically, these vaccines induce responses that target group 1 or group 2 hemagglutinins with little to no cross-group reactivity and protection. Similarly, the majority of human anti-stalk monoclonal antibodies that have been isolated are directed against group 1 or group 2 hemagglutinins with very few that bind to hemagglutinins of both groups. Here we review what is known about the human humoral immune response to vaccination and infection with H7 subtype influenza viruses on a polyclonal and monoclonal level. It seems that unlike vaccination with H5 hemagglutinin, which induces antibody responses mostly restricted to the group 1 stalk domain, H7 exposure induces both group 2 and cross-group antibody responses. A better understanding of this phenomenon and the underlying mechanisms might help to develop future universal influenza virus vaccine candidates.

Trade-Offs for Viruses in Overcoming Innate Immunities in Plants

Plants recognize viral infection via an immune receptor, i.e., nucleotide-binding site (NB)-leucine-rich repeat (LRR) proteins. Another immune receptor, receptor-like kinase proteins, which share an LRR domain with NB-LRRs, perceive conserved molecules of pathogens called pathogen- or microbe-associated molecular patterns, but NB-LRRs generally perceive particular viral proteins. As viruses can evolve more rapidly than the host immune system, how do plant immune systems, which rely on the perception of proteins, remain effective? Viral adaptive evolution may be controlled by penalties that result from mutations in viral proteins that are perceived by NB-LRRs. Our recent studies in pea (Pisum sativum) suggest a penalty of increased susceptibility to another immune system. When a viral protein mutates to evade one immune system, the virus with the mutated protein becomes more susceptible to another. Such antagonistic pleiotropy of a viral protein by two independent plant immune systems may have precedents. Plants may rely on pairs of immune systems to constrain adaptive evolution by viruses and thereby maintain durable antiviral immunity. [Formula: see text] Copyright © 2016 The Author(s). This is an open access article distributed under the CC BY-NC 4.0 International license .

The evolution and genetics of virus host shifts

Emerging viral diseases are often the product of a host shift, where a pathogen jumps from its original host into a novel species. Phylogenetic studies show that host shifts are a frequent event in the evolution of most pathogens, but why pathogens successfully jump between some host species but not others is only just becoming clear. The susceptibility of potential new hosts can vary enormously, with close relatives of the natural host typically being the most susceptible. Often, pathogens must adapt to successfully infect a novel host, for example by evolving to use different cell surface receptors, to escape the immune response, or to ensure they are transmitted by the new host. In viruses there are often limited molecular solutions to achieve this, and the same sequence changes are often seen each time a virus infects a particular host. These changes may come at a cost to other aspects of the pathogen's fitness, and this may sometimes prevent host shifts from occurring. Here we examine how these evolutionary factors affect patterns of host shifts and disease emergence.

MicroRNAs in the regulation of TLR and RIG-I pathways

The innate immune system recognizes invading pathogens through germline-encoded pattern recognition receptors (PRRs), which elicit innate antimicrobial and inflammatory responses and initiate adaptive immunity to control or eliminate infection. Toll-like receptors (TLRs) and retinoic acid-inducible gene I (RIG-I) are the key innate immune PRRs and are tightly regulated by elaborate mechanisms to ensure a beneficial outcome in response to foreign invaders. Although much of the focus in the literature has been on the study of protein regulators of inflammation, microRNAs (miRNAs) have emerged as important controllers of certain features of the inflammatory process. Several miRNAs are induced by TLR and RIG-I activation in myeloid cells and act as feedback regulators of TLR and RIG-I signaling. In this review, we comprehensively discuss the recent understanding of how miRNA networks respond to TLR and RIG-I signaling and their role in the initiation and termination of inflammatory responses. Increasing evidence also indicates that both virus-encoded miRNAs and cellular miRNAs have important functions in viral replication and host anti-viral immunity.

Dynamics of stochastic mutation to immunodominance

Although a virus contains several epitopes that can be recognized by cytotoxic T lymphocytes (CTL), the immune responses against different epitopes are not uniform. Only a few CTLs (sometimes just one) will be immunodominant. Mutation of epitopes has been recognized as an important mechanism of immunodominance. Previous research has studied the influences of sporadic, discrete mutation events. In this work, we introduce a bounded noise term to account for the intrinsic stochastic nature of mutation. Monte Carlo simulations of the stochastic model show abounding complex phenomena, and patterns observed from the numerical simulations shed lights on long term trends of immunodomnance.

Emerging viral infections of the central nervous system: part 2

The first part of this review ended with a discussion of new niches for known viruses as illustrated by viral central nervous system (CNS) disease associated with organ transplant and the syndrome of human herpesvirus 6-associated posttransplant acute limbic encephalitis. In this part, we begin with a continuation of this theme, reviewing the association of JC virus-associated progressive multifocal leukoencephalopathy (PML) with novel immunomodulatory agents. This part then continues with emerging viral infections associated with importation of infected animals (monkeypox virus), then spread of vectors and enhanced vector competence (chikungunya virus [CHIK]), and novel viruses causing CNS infections including Nipah and Hendra viruses and bat lyssaviruses (BLV).