We have recently described a method of introducing site-specific mutations into the genome of the coronavirus mouse hepatitis virus (MHV) by RNA recombination between cotransfected genomic RNA and a synthetic subgenomic mRNA (C. A. Koetzner, M. M. Parker, C. S. Ricard, L. S. Sturman, and P. S. Masters, J. Virol. 66:1841-1848. By using a thermolabile N protein mutant of MHV (Alb4) as the recipient virus and synthetic RNA7 (the mRNA for the nucleocapsid protein N) as the donor, we selected engineered recombinant viruses as heat-stable progeny resulting from cotransfection. We have now been able to greatly increase the efficiency of targeted recombination in this process by using a synthetic defective interfering (DI) RNA in place of RNA7. The frequency of recombination is sufficiently high that, with Alb4 as the recipient, recombinants can be directly identified without using thermal selection. The synthetic DI RNA has been used to demonstrate that the lesion in another temperature-sensitive and thermolabile MHV mutant, Albl, maps to the N gene. Sequencing of the Albl N gene revealed two closely linked point mutations that fall in a region of the N molecule previously noted as being the most highly conserved region among all of the coronavirus N proteins. Analysis of revertants of the Albl mutant revealed that one of the two mutations is critical for the temperature-sensitive phenotype; the second mutation is phenotypically silent.

BTBR T+tf/J (BTBR) mice have recently been reported to have behaviors that resemble those of autistic individuals, in that this strain has impairments in social interactions and a restricted repetitive and stereotyped pattern of behaviors. Since immune responses, including autoimmune responses, are known to affect behavior, and individuals with autism have aberrant immune activities, we evaluated the immune system of BTBR mice, and compared their immunity and degree of neuroinflammation with that of C57BL/6 (B6) mice, a highly social control strain, and with F1 offspring. Mice were assessed at postnatal day (pnd) 21 and after behavioral analysis at pnd70. BTBR mice had significantly higher amounts of serum IgG and IgE, of IgG anti-brain antibodies (Abs), and of IgG and IgE deposited in the brain, elevated expression of cytokines, especially IL-33 IL-18, and IL-1β in the brain, and an increased proportion of MHC class II-expressing microglia compared to B6 mice. The F1 mice had intermediate levels of Abs and cytokines as well as social activity. The high Ab levels of BTBR mice are in agreement with their increased numbers of CD40hi/I-Ahi B cells and IgG-secreting B cells. Upon immunization with KLH, the BTBR mice produced 2–3 times more anti-KLH Abs than B6 mice. In contrast to humoral immunity, BTBR mice are significantly more susceptible to listeriosis than B6 or BALB/c mice. The Th2-like immune profile of the BTBR mice and their constitutive neuroinflammation suggests that an autoimmune profile is implicated in their aberrant behaviors, as has been suggested for some humans with autism.

We demonstrate that among the three monofunctional catalases of Pseudomonas aeruginosa PA14, KatA and, to a lesser extent, KatB, but not KatE, are required for resistance to peroxide and osmotic stresses. KatA is crucial for adaptation to H 2 O 2 stress and full virulence in both Drosophila melanogaster and mice. This dismantling of catalase roles represents a specialized catalytic system primarily involving KatA in responses to adverse environmental conditions.

No abstract

The adaptive response to hydrogen peroxide (H 2 O 2 ) in Pseudomonas aeruginosa involves the major catalase, KatA, and OxyR. However, neither the molecular basis nor the relationship between the aforementioned proteins has been established. Here, we demonstrate that the transcriptional activation of the katA promoter (katAp) in response to H 2 O 2 was abrogated in the P. aeruginosa PA14 oxyR null mutant. Promoter deletion analyses revealed that H 2 O 2 -mediated induction was dependent on a region of DNA ؊76 to ؊36 upstream of the H 2 O 2 -responsive transcriptional start site. This region harbored the potential operator sites (OxyRresponsive element [ORE]) of the Escherichia coli OxyR binding consensus. Deletion of the entire ORE not only abolished H 2 O 2 -mediated induction but also elevated the basal transcription, suggesting the involvement of OxyR and the ORE in both transcriptional activation and repression. OxyR bound to the ORE both in vivo and in vitro, demonstrating that OxyR directly regulates the katAp. Three distinct mobility species of oxidized OxyR were observed in response to 1 mM H 2 O 2 , as assessed by free thiol trapping using 4-acetamido-4-maleimidylstilbene-2,2-disulfonic acid. These oxidized species were not observed for the double mutants with mutations in the conserved cysteine (Cys) residues (C199 and C208). The uninduced transcription of katAp was elevated in an oxyR mutant with a mutation of Cys to serine at 199 (C199S) and even higher in the oxyR mutant with a mutation of Cys to alanine at 199 (C199A) but not in oxyR mutants with mutations in C208 (C208S and C208A). In both the C199S and the C208S mutant, however, katAp transcription was still induced by H 2 O 2 treatment, unlike in the oxyR null mutant and the C199A mutant. The double mutants with mutations in both Cys residues (C199S C208S and C199A C208S) did not differ from the C199A mutant. Taken together, our results suggest that P. aeruginosa OxyR is a bona fide transcriptional regulator of the katA gene, sensing H 2 O 2 based on the conserved Cys residues, involving more than one oxidation as well as activation state in vivo.

Phage therapy against Pseudomonas aeruginosa infections has received renewed attention owing to the increasing prevalence of antibiotic resistance in this bacterium. Here, we isolated and characterized two new potentially lytic bacteriophages (MPK1 and MPK6), which produced large and clear plaques on P. aeruginosa strain PAO1. Based on their morphology, MPK1 belongs to the Myoviridae, while MPK6 belongs to the Podoviridae. The group B polysaccharide of lipopolysaccharide was required for infection, suggesting that their host spectra are associated with the serotypes of P. aeruginosa strains. Intramuscular and intraperitoneal administration of MPK1 and, to a lesser extent, MPK6 significantly protected mice from mortality caused by PAO1-induced peritonitis-sepsis (P < 0.01). Mice treated with either phage also had lower bacterial burdens in their livers, lungs, and spleens. The antibacterial efficacy of MPK1 and MPK6 was also evaluated based on Drosophila melanogaster systemic infection caused by P. aeruginosa, for which phages were administered by feeding. Both phages significantly delayed the PAO1-induced killing of D. melanogaster (P < 0.001), although MPK1 persisted longer than MPK6 in uninfected D. melanogaster tissue samples. These results suggest that a mini-scale experiment using D. melanogaster infection is valid for evaluating the antibacterial efficacy of phage therapy against P. aeruginosa infections.

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The environmental heavy metal toxicant, lead (Pb), has been shown to be more harmful to the central nervous system (CNS) of children than to adults, given that Pb exposure affects the neural system during development. Because growth factors and cytokines play very important roles in development of the CNS, we have examined the impact of Pb exposure on the expression of cytokines during CNS development. Cytokine expression was studied in post-natal-day 21(pnd21) mice by microarray, real-time RT-PCR, Luminex, and ELISA methodologies. BALB/c mouse pups were exposed to Pb through the dam’s drinking water (0.1 mM Pb acetate), from gestation-day 8 (gd8) to pnd21. Two cytokines, interleukin-6 (IL-6) and transforming growth factor-β1 (TGF-β1), displayed significantly changed transcript levels in the presence of Pb. IL-6 and TGF-β1 both have signal transduction cascades that can cooperatively turn on the gene for the astrocyte marker glial-fibrillary acidic protein (GFAP). Microarray results indicated that Pb exposure significantly increased expression of GFAP. Pb also modulated IL-6, TGF-β1, and IL-18 protein expression in select brain regions. The deleterious effects of Pb on learning and long-term memory are posited to result from excessive astrocyte growth and/or activation with concomitant interference with neural connections. Differential neural expression of cytokines in brain regions needs to be further investigated to mechanistically associate Pb and neuroinflammation with behavioral and cognitive changes.