Infection of mice, ferrets, and rhesus macaques with a clinical mumps virus isolate.

In recent years, many mumps outbreaks have occurred in vaccinated populations worldwide. The reasons for these outbreaks are not clear. Animal models are needed to investigate the causes of outbreaks and to understand the pathogenesis of mumps virus (MuV). In this study, we have examined the infection of three animal models with an isolate of mumps virus from a recent outbreak (MuV-IA). We have found that while both ferrets and mice generated humoral and cellular immune responses to MuV-IA infection, no obvious signs of illness were observed in these animals; rhesus macaques were the most susceptible to MuV-IA infection. Infection of rhesus macaques via both intranasal and intratracheal routes with MuV-IA led to the typical clinical signs of mumps 2 weeks to 4 weeks postinfection. However, none of the infected macaques showed any fever or neurologic signs during the experimental period. Mumps viral antigen was detected in parotid glands by immunohistochemistry (IHC). Rhesus macaques represent the best animal model for the study of mumps virus pathogenesis.

JBP1 and JBP2 proteins are Fe2+/2-oxoglutarate-dependent dioxygenases regulating hydroxylation of thymidine residues in trypanosome DNA.

We have recently demonstrated that O-linked glucosylation of thymine in trypanosome DNA (base J) regulates polymerase II transcription initiation. In vivo analysis has indicated that base J synthesis is initiated by the hydroxylation of thymidine by proteins (JBP1 and JBP2) homologous to the Fe(2+)/2-oxoglutarate (2-OG)-dependent dioxygenase superfamily where hydroxylation is driven by the oxidative decarboxylation of 2-OG, forming succinate and CO(2). However, no direct evidence for hydroxylase activity has been reported for the JBP proteins. We now demonstrate recombinant JBP1 hydroxylates thymine specifically in the context of dsDNA in a Fe(2+)-, 2-OG-, and O(2)-dependent manner. Under anaerobic conditions, the addition of Fe(2+) to JBP1/2-OG results in the formation of a broad absorption spectrum centered at 530 nm attributed to metal chelation of 2-OG bound to JBP, a spectroscopic signature of Fe(2+)/2-OG-dependent dioxygenases. The N-terminal thymidine hydroxylase domain of JBP1 is sufficient for full activity and mutation of residues involved in coordinating Fe(2+) inhibit iron binding and thymidine hydroxylation. Hydroxylation in vitro and J synthesis in vivo is inhibited by known inhibitors of Fe(2+)/2-OG-dependent dioxygenases. The data clearly demonstrate the JBP enzymes are dioxygenases acting directly on dsDNA, confirming the two-step J synthesis model. Growth of trypanosomes in hypoxic conditions decreases JBP1 and -2 activity, resulting in reduced levels of J and changes in parasite virulence previously characterized in the JBP KO. The influence of environment upon J biosynthesis via oxygen-sensitive regulation of JBP1/2 has exciting implications for the regulation of gene expression and parasite adaptation to different host niches.

Identification of quantitative trait loci for susceptibility to mouse adenovirus type 1.

Adult SJL/J mice are highly susceptible to mouse adenovirus type 1 (MAV-1) infections, whereas other inbred strains, including BALB/cJ, are resistant (K. R. Spindler, L. Fang, M. L. Moore, C. C. Brown, G. N. Hirsch, and A. K. Kajon, J. Virol. 75:12039-12046, 2001). Using congenic mouse strains, we showed that the H-2(s) haplotype of SJL/J mice is not associated with susceptibility to MAV-1. Susceptibility of MAV-1-infected (BALB/cJ x SJL/J)F(1) mice was intermediate between that of SJL/J mice and that of BALB/cJ mice, indicating that susceptibility is a genetically controlled quantitative trait. We mapped genetic loci involved in mouse susceptibility to MAV-1 by analysis of 192 backcross progeny in a genome scan with 65 simple sequence length polymorphic markers. A major quantitative trait locus (QTL) was detected on chromosome 15 (Chr 15) with a highly significant logarithm of odds score of 21. The locus on Chr 15 alone accounts for 40% of the total trait variance between susceptible and resistant strains. QTL modeling of the data indicated that there are a number of other QTLs with small effects that together with the major QTL on Chr 15 account for 54% of the trait variance. Identification of the major QTL is the first step in characterizing host genes involved in susceptibility to MAV-1.