Subfamily: Densovirinae
Genus: Penstyldensovirus
Distinguishing features
Penstyldensoviruses were known previously as infectious hypodermal and hematopoietic necrosis viruses (IHHNV) of prawns and shrimp. They have small (~4 kb) monosense genomes that lack discernable PLA2 motifs, and most closely resemble the mosquito-infecting viruses in genus Brevidensovirus (Figures 5. Parvoviridae and 6A. Parvoviridae). The exemplar virus of the type species Decapod penstyldensovirus 1 is Penaeus stylirostris penstyldensovirus 1 (AF273215; PstDV1). Following PCR amplification based on this initial sequence, viruses have been identified from a variety of Penaeus species captured in many parts of the world, but these viruses all appear very similar and are all members of the single species in the genus, Decapod penstyldensovirus 1.
Virion
See discussion under family description and Figures 1. Parvoviridae and 2. Parvoviridae.
Genome organization
Genome organization resembles that of viruses in genus Brevidensovirus (Figure 3. Parvoviridae) (Dhar et al., 2014). The viruses have very short capsid protein sequences, and may only express a single VP protein of 37 kDa, the smallest in the family known to date, 60 copies of which can self-assemble into virus-like particles (VLPs) (Kaufmann et al., 2010).
Biology
These viruses were first identified as pathogens responsible for an economically significant and virulent disease in farmed shrimp (infectious hypodermal and hematopoietic necrosis). They are widespread in nature, but are no longer a major economic problem because tolerant shrimp populations have been developed. PstDV1-related Endogenous Viral Element (EVE) sequences, lacking hairpins, have been detected in the germline of P. monodon in Australia, Madagascar and Thailand (Saksmerprome et al., 2011). These would likely have been eliminated unless they provide beneficial effects, such as EVE-derived immunity (EDI, e.g. mediated by TRIM5a and APOBEC).