Neutrophils in viral infections: Current concepts and caveats

Abstract

Neutrophils are the first immune cell population recruited to sites of infection, including viral infections, and exhibit both protective and pathologic functions. In antibacterial and antifungal immunity, the role of neutrophils is well defined. However, in antiviral immunity, much less is known. Conventional wisdom suggests that neutrophils enhance antiviral defenses, yet evidence for that is limited. Interaction with other immune cell populations, virus internalization and killing, the release of cytokines, chemokines, and antimicrobial components are all mechanisms by which neutrophils can contribute to pathogen clearance. NET formation, extensively studied during bacterial infection, can further mediate antiviral defense by trapping and inactivating virus. In the present review, we discuss the current understanding of the complex role of neutrophil immunity in viral infections and disease pathogenesis and the potential mechanisms identified to date. We pinpoint the importance of a finely tuned neutrophilic response for achieving effective immune protection while avoiding detrimental tissue damage that can form the basis for the development of novel therapeutics.

Heartland virus infection in hamsters deficient in type I interferon signaling: Protracted disease course ameliorated by favipiravir

“…The presence of neutrophilic inflammation in several hamster organs correlates well with the neutrophilia and was also observed in a related phlebovirus infection model (Gowen et al, 2016). Although the role of neutrophils in the control of viral infections is still unclear (Galani and Andreakos, 2015), it is possible that the neutrophilic inflammatory response induced by HRTV infection may substantially contribute to virus clearance, as supported by the inconsistent and relatively low levels of infectious virus when present in hamster tissues.…”

A Broad-Spectrum Chemokine-Binding Protein of Bovine Papular Stomatitis Virus Inhibits Neutrophil and Monocyte Infiltration in Inflammatory and Wound Models of Mouse Skin

“…In addition, it is now becoming clear that these cells have a role in host defence against viruses. They are crucial for NK cell homeostasis and function, a major cell population involved in the elimination of viruses [57,58]. Neutrophils also produce small peptides called defensins and some of these have recently been shown to have anti-viral activity against such viruses as herpes virus 1 and 2, vesicular stomatitis virus, influenza virus and adenovirus [59].…”

Deletion of <b><i>Irf3</i></b> and <b><i>Irf7</i></b> Genes in Mice Results in Altered Interferon Pathway Activation and Granulocyte-Dominated Inflammatory Responses to Influenza A Infection

“…The genes encoding the proinflammatory cytokines TNF and IL-1 were found to be more highly expressed in DKO compared to WT mice, as well as other granulocyte-attracting chemokines like Cxcl1 , Cxcl2 , Cxcl3 , and Cxcl5 . The role of granulocytes in viral infections is dichotomous, since they can have beneficial and detrimental effects [39][40][41][42] . The release of their toxic substances might be responsible for massive cell damage and tissue necrosis leading to severe pneumonia and acute respiratory distress syndrome.…”