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Human hepatitis E virus infections may be caused by zoonotic transmission of virus genotypes 3 and 4. To determine whether rodents are a reservoir, we analyzed the complete nucleotide sequence of a hepatitis E–like virus from 2 Norway rats in Germany. The sequence suggests a separate genotype for this hepatotropic virus.

Herpesviruses specify a ubiquitin-specific protease activity located within their largest tegument protein.Although its biological role is still largely unclear, mutation within the active site abolished deubiquitinating (DUB) activity and decreased virus replication in vitro and in vivo. To further elucidate the role of DUB activity for herpesvirus replication, the conserved active-site cysteine at amino acid position 26 within pUL36 of Pseudorabies virus (PrV) (Suid herpesvirus 1), a neurotropic alphaherpesvirus, was mutated to serine. Whereas one-step growth kinetics of the resulting mutant virus PrV-UL36(C 26 S) were moderately reduced, plaque size was decreased to 62% of that of the wild-type virus. Ultrastructural analysis revealed large accumulations of unenveloped nucleocapsids in the cytoplasm, but incorporation of the tegument protein pUL37 was not abolished. After intranasal infection with PrV-UL36(C 26 S) mice showed survival times two times longer than those of mice infected with wild-type or rescued virus. Thus, the DUB activity is important for PrV replication in vitro and for neuroinvasion in mice.Herpesviruses possess a large double-stranded DNA genome, comprising more than 70 open reading frames (ORFs) encoding viral proteins, of which at least 30 are incorporated into the mature virus particle. The most complex virion component is the tegument, which, in the alphaherpesviruses, contains more than 15 different viral proteins. Operationally, the tegument has been divided into an "inner," capsid-associated part and an "outer," envelope-juxtaposed portion (reviewed in references 42 and 43). The innermost part contains the largest herpesvirus tegument protein, which, in the prototypic alphaherpesvirus herpes simplex virus type 1 (HSV-1), is the product of the UL36 gene. Homologs of this protein, for clarity henceforth named pUL36, are present in all members of the Herpesviridae which have been analyzed in this respect to date.Previous studies revealed two conserved domains within the N termini of pUL36 homologs. One is required for interaction with pUL37, another conserved tegument protein (4,22,33,44,50), whereas the second specifies a ubiquitin-specific cysteine protease activity (20,24,27,47,48,51). This activity is not required for herpesvirus replication, as has been shown for human cytomegalovirus (HCMV) (51) and Marek's disease virus (MDV) (24). Nevertheless, abrogation of deubiquitinating activity resulted in impairment of replication in vitro (51) and in vivo (24).In pseudorabies virus (PrV), pUL36 is the only truly essential tegument protein (14), and its deletion completely blocks viral replication. Interestingly, recent data demonstrated that about one-third of PrV pUL36 located in the C-terminal half can be deleted without drastic impairment of viral replication. In contrast, the extreme C terminus of pUL36 is essential (6, 35), probably due to its association with the capsid-associated pUL25 (10). Moreover, deletion of an N-terminal domain of about 200 amino acids comprising the deubi...

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Proteins of the capsid proximal tegument are involved in the transport of incoming capsids to the nucleus and secondary envelopment after nuclear egress. Homologs of the essential large capsid proximal tegument protein pUL36 are conserved within the Herpesviridae. They interact with another tegument component, pUL37, and contain a deubiquitinating activity in their N termini which, however, is not essential for virus replication.