Immunity to Fish Rhabdoviruses

Abstract

Members of the family Rhabdoviridae are single-stranded RNA viruses and globally important pathogens of wild and cultured fish and thus relatively well studied in their respective hosts or other model systems. Here, we review the protective immune mechanisms that fish mount in response to rhabdovirus infections. Teleost fish possess the principal components of innate and adaptive immunity found in other vertebrates. Neutralizing antibodies are critical for long-term protection from fish rhabdoviruses, but several studies also indicate a role for cell-mediated immunity. Survival of acute rhabdoviral infection is also dependent on innate immunity, particularly the interferon (IFN) system that is rapidly induced in response to infection. Paradoxically, rhabdoviruses are sensitive to the effects of IFN but virulent rhabdoviruses can continue to replicate owing to the abilities of the matrix (M) protein to mediate host-cell shutoff and the non‑virion (NV) protein to subvert programmed cell death and suppress functional IFN. While many basic features of the fish immune response to rhabdovirus infections are becoming better understood, much less is known about how factors in the environment affect the ecology of rhabdovirus infections in natural populations of aquatic animals.

Temporal Variation in Viral Hemorrhagic Septicemia Virus Antibodies in Freshwater Drum (Aplodinotus grunniens) Indicates Cyclic Transmission in Lake Winnebago, Wisconsin

“…Increasing weight of the fish was also positively associated with anti-nucleocapsid antibodies. The increase in serum antibodies in older fish indicates increased probability of exposure to the virus with time and, perhaps, increased protection (30,31). The correlation between higher antibody titers and weight likely reflects a similar relationship, where older fish attain higher weights and are exposed to antibodies for a longer time.…”

Inhibition of an Aquatic Rhabdovirus Demonstrates Promise of a Broad-Spectrum Antiviral for Use in Aquaculture

“…We also suspect that virus inactivated by LJ001 may elicit an innate immune response that could be protective to the host, which would potentially decrease viral loads and shedding or block infection completely. Natural IHNV infection stimulates a robust early innate response followed by a long-term specific immune response (28). The speed and magnitude of the response are dependent on a number of variables, including water temperature, virus dose, strain, and other host/virus factors.…”

The Role of Virulence in In Vivo Superinfection Fitness of the Vertebrate RNA Virus Infectious Hematopoietic Necrosis Virus

“…Apparent competition has been described as a refractory state resulting from immune stimulation following primary viral infection (50). For IHNV infection in rainbow trout, it has been thoroughly documented that, within the first few days of infection, the host response is dominated by a strong induction of numerous interferon-stimulated genes, including Mx-1 (51). In addition, pretreatment of rainbow trout with an injection of poly(I·C), a TLR-3 agonist, offers significant protection from infection and mortality following challenge with IHNV (34).…”