Chlamydia pneumoniae Hides inside Apoptotic Neutrophils to Silently Infect and Propagate in Macrophages

Background

Intracellular pathogens have developed elaborate strategies for silent infection of preferred host cells. Chlamydia pneumoniae is a common pathogen in acute infections of the respiratory tract (e.g. pneumonia) and associated with chronic lung sequelae in adults and children. Within the lung, alveolar macrophages and polymorph nuclear neutrophils (PMN) are the first line of defense against bacteria, but also preferred host phagocytes of chlamydiae.

Methodology/Principal Findings

We could show that C. pneumoniae easily infect and hide inside neutrophil granulocytes until these cells become apoptotic and are subsequently taken up by macrophages. C. pneumoniae infection of macrophages via apoptotic PMN results in enhanced replicative activity of chlamydiae when compared to direct infection of macrophages, which results in persistence of the pathogen. Inhibition of the apoptotic recognition of C. pneumoniae infected PMN using PS- masking Annexin A5 significantly lowered the transmission of chlamydial infection to macrophages. Transfer of apoptotic C. pneumoniae infected PMN to macrophages resulted in an increased TGF-ß production, whereas direct infection of macrophages with chlamydiae was characterized by an enhanced TNF-α response.

Conclusions/Significance

Taken together, our data suggest that C. pneumoniae uses neutrophil granulocytes to be silently taken up by long-lived macrophages, which allows for efficient propagation and immune protection within the human host.     

Closing gaps in the human genome using sequencing by synthesis

The most recent release of the finished human genome contains 260 euchromatic gaps (excluding chromosome Y). Recent work has helped explain a large number of these unresolved regions as 'structural' in nature. Another class of gaps is likely to be refractory to clone-based approaches, and cannot be approached in ways previously described. We present an approach for closing these gaps using 454 sequencing. As a proof of principle, we closed all three remaining non-structural gaps in chromosome 15.     

The metallo-beta-lactamase GOB is a mono-Zn(II) enzyme with a novel active site

Metallo-beta-lactamases (MbetaLs) are zinc-dependent enzymes able to hydrolyze and inactivate most beta-lactam antibiotics. The large diversity of active site structures and metal content among MbetaLs from different sources has limited the design of a pan-MbetaL inhibitor. Here we report the biochemical and biophysical characterization of a novel MbetaL, GOB-18, from a clinical isolate of a Gram-negative opportunistic pathogen, Elizabethkingia meningoseptica. Different spectroscopic techniques, three-dimensional modeling, and mutagenesis experiments, reveal that the Zn(II) ion is bound to Asp120, His121, His263, and a solvent molecule, i.e. in the canonical Zn2 site of dinuclear MbetaLs. Contrasting all other related MbetaLs, GOB-18 is fully active against a broad range of beta-lactam substrates using a single Zn(II) ion in this site. These data further enlarge the structural diversity of MbetaLs.     

Effect of exercise duration on postprandial hypertriglyceridemia in men with metabolic syndrome.

We examined the effect of exercise on postprandial hypertriglyceridemia (PHTG) and insulin resistance in individuals with metabolic syndrome. Subjects were 10 hypertriglyceridemic men with insulin resistance [age = 35.0 +/- 1.8 yr, body weight = 90.7 +/- 3.3 kg, fasting triglyceride (TG) = 2.6 +/- 0.4 mmol/l, peak oxygen consumption ((.)Vo(2peak)) = 36.0 +/- 1.3 ml(-1).kg(-1).min(-1), and homeostatic model assessment of insulin resistance (HOMA-IR)= 3.1 +/- 0.3]. Each participant performed a control trial (Ctr; no exercise) and three exercise trials at 60% of their (.)Vo(2peak) for 30 min (30 min-Ex), 45 min (45 min-Ex) and 60 min (60 min-Ex). All subjects had a fat meal in each trial. In the exercise trials, the subject jogged on a treadmill for a designated duration of 12 h before ingestion of a fat meal. Blood samples were taken at 0 h (before the meal) and at 2, 4, 6, and 8 h after the meal. The plasma TG, area score under TG concentration curve over an 8-h period (TG AUC) after the meal, and HOMA-IR were analyzed. The TG AUC scores in both the 45 min-Ex and 60 min-Ex were 31 and 33% lower, respectively, than Ctr (P < 0.02). There were no significant differences in TG AUC scores between the 30 min-Ex and the Ctr (P > 0.05). There were no trial differences in the fasting plasma glucose concentration (P > 0.05). HOMA-IR values in the 30 min-Ex, 45 min-Ex, and 60 min-Ex trials were lower than the Ctr (P < 0.03), but no significant differences were found in HOMA-IR among the exercise trials. The results suggest that for physically inactive individuals with metabolic syndrome, exercising at moderate intensity for 45 min effectively attenuates PHTG while exercise for 30 min is sufficient to improve insulin action.     

Age and growth estimates for the smooth skate, Malacoraja senta, in the Gulf of Maine

Age and growth estimates for the smooth skate, Malacoraja senta, were derived from 306 vertebral centra from skates caught in the North Atlantic off the coast of New Hampshire and Massachusetts, USA. Males and females were aged to 15 and 14 years, respectively. Male and female growth diverged at both ends of the data range and the sexes required different growth functions to describe them. Males followed a traditional growth scenario and were best described by a von Bertalanffy curve with a set L _o (11 cm TL) where L _inf  = 75.4 cm TL, K = 0.12. Females required the use of back-calculated values to account for a lack of small individuals, using these data they were best described by a von Bertalanffy curve where growth parameters derived from vertebral length-at-age data are L _inf  = 69.6 cm TL, K = 0.12, and L _o  = 10.     

Heterogeneous selection at specific loci in natural environments in Arabidopsis thaliana

Genetic variation for quantitative traits is often greater than that expected to be maintained by mutation in the face of purifying natural selection. One possible explanation for this observed variation is the action of heterogeneous natural selection in the wild. Here we report that selection on quantitative trait loci (QTL) for fitness traits in the model plant species Arabidopsis thaliana differs among natural ecological settings and genetic backgrounds. At one QTL, the allele that enhanced the viability of fall-germinating seedlings in North Carolina reduced the fecundity of spring-germinating seedlings in Rhode Island. Several other QTL experienced strong directional selection, but only in one site and seasonal cohort. Thus, different loci were exposed to selection in different natural environments. Selection on allelic variation also depended upon the genetic background. The allelic fitness effects of two QTL reversed direction depending on the genotype at the other locus. Moreover, alternative alleles at each of these loci caused reversals in the allelic fitness effects of a QTL closely linked to TFL1, a candidate developmental gene displaying nucleotide sequence polymorphism consistent with balancing selection. Thus, both environmental heterogeneity and epistatic selection may maintain genetic variation for fitness in wild plant species.     

Post-thaw functional status of boar spermatozoa cryopreserved using three controlled rate freezers: a comparison

This study compared variation in the quality of cryopreserved boar spermatozoa and the control and accuracy of cooling rates between three semen freezers (CryoLogic Freeze Control CL3000, Planer Products Kryo Save Compact KS1.7/Kryo 10 Control module and a controlled rate 'Watson' freezing machine developed within our laboratory). Five ejaculates were collected from each of 15 boars (five boars from each of three breeds). Semen was diluted into a commercial freezing buffer (700 mOsm/kg, 3% v/v glycerol) and placed into 0.5 ml straws. Three straws per treatment, from each ejaculate were cooled to -5 degrees C at 6 degrees C/min, held at -5 degrees C for 30s while ice crystal formation was induced, then further cooled from -5 to 80 degrees C at either 40 degrees C/min (Kryo Save Compact KS1.7 and Watson) or 6 degrees C/min (Freeze Control CL3000). Precise measurements of temperature fluctuations during the programmed cooling curves were made by inserting thermocouples into the semen filled straws. Semen was assessed for %motile cells, motility characteristics using computer-assisted semen analysis (CASA), plasma membrane integrity (%SYBR-14 positive stained spermatozoa) and acrosome integrity (%FITC-PNA positive stained spermatozoa). Spermatozoa cryopreserved using the Freeze Control CL3000 system (maximum rate of 6 degrees C/min) exhibited reduced post-thaw viability (14.2+/-2.8% mean plasma membrane intact spermatozoa) when compared to both the KS1.7 and Watson freezers (optimal rate of 40 degrees C/min) (18.4+/-3.2 and 25.7+/-3.7% mean plasma membrane intact spermatozoa, respectively). Differences in motility characteristics were observed between spermatozoa cryopreserved at 40 degrees C/min with the Watson apparatus preserving a larger proportion of sperm with progressive motility. Cooling curves in the CL3000 and KS1.7 were interrupted by a pronounced increase in temperature at -5 degrees C that corresponded with the latent heat of fusion released with ice crystal formation. This temperature change was significantly reduced in the cooling curves produced by the Watson freezer. These findings suggest that preserving spermatozoa using the Watson freezer improved post-thaw semen quality, with regard to sperm motility characteristics. Furthermore, that post-thaw semen viability was enhanced by minimising temperature fluctuations resulting from the release of the latent heat of fusion at ice crystal formation.     

A deubiquitinating enzyme encoded by HSV-1 belongs to a family of cysteine proteases that is conserved across the family Herpesviridae

We have discovered a ubiquitin (Ub)-specific cysteine protease encoded within the N-terminal approximately 500 residues of the UL36 gene product, the largest (3164 aa) tegument protein of herpes simplex virus 1 (HSV-1). Enzymatic activity of this fragment, UL36USP, is detectable only after cleavage of UL36USP from full-length UL36 and occurs late during viral replication. UL36USP bears no homology to known deubiquitinating enzymes (DUBs) or Ub binding proteins. Sequence alignment of the large tegument proteins across the family Herpesviridae indicates conservation of key catalytic residues amongst these viruses. Recombinant UL36USP exhibits hydrolytic activity toward Ub-AMC and ubiquitinated branched peptides in vitro. In addition, recombinant UL36USP can cleave polyUb chains and appears to be specific for Lys48 linkages. Mutation of the active site cysteine residue (Cys65) to alanine abolishes this enzymatic activity. The lack of homology between UL36USP and eukaryotic DUBs makes this new family of herpesvirus ubiquitin-specific proteases attractive targets for selective inhibition.     

Genetic divergence does not predict change in ornament expression among populations of stalk-eyed flies

Stalk-eyed flies (Diptera: Diopsidae) possess eyes at the ends of elongated peduncles, and exhibit dramatic variation in eye span, relative to body length, among species. In some sexually dimorphic species, evidence indicates that eye span is under both intra- and intersexual selection. Theory predicts that isolated populations should evolve differences in sexually selected traits due to drift. To determine if eye span changes as a function of divergence time, 1370 flies from 10 populations of the sexually dimorphic species, Cyrtodiopsis dalmanni and Cyrtodiopsis whitei, and one population of the sexually monomorphic congener, Cyrtodiopsis quinqueguttata, were collected from Southeast Asia and measured. Genetic differentiation was used to assess divergence time by comparing mitochondrial (cytochrome oxidase II and 16S ribosomal RNA gene fragments) and nuclear (wingless gene fragment) DNA sequences for c. five individuals per population. Phylogenetic analyses indicate that most populations cluster as monophyletic units with up to 9% nucleotide substitutions between populations within a species. Analyses of molecular variance suggest a high degree of genetic structure within and among the populations; > 97% of the genetic variance occurs between populations and species while < 3% is distributed within populations, indicating that most populations have been isolated for thousands of years. Nevertheless, significant change in the allometric slope of male eye span on body length was detected for only one population of either dimorphic species. These results are not consistent with genetic drift. Rather, relative eye span appears to be under net stabilizing selection in most populations of stalk-eyed flies. Given that one population exhibited dramatic evolutionary change, selection, rather than genetic variation, appears to constrain eye span evolution.     

Shoot organogenesis and plant regeneration in <Emphasis Type="Italic">Pityopsis ruthii</Emphasis>

Pityopsis ruthii is an endangered herbaceous perennial species from the United States. In vitro multiplication of this species can be valuable for germplasm conservation. Flower receptacles of P. ruthii were cultured on Murashige and Skoog medium (MS) supplemented with 11.4 μM indole-3-acetic acid (IAA) in combination with 2.2, 4.4 or 8.8 μM 6-benzyladenine (BA). Shoots were visible within 14–28 days and three plants were successfully rooted on MS medium supplemented with 5.7 μM IAA. A two tailed t-test for paired-variates revealed that shoot regeneration on MS medium amended with 11.4 μM IAA and 2.2 μM BA was significantly higher (P < 0.05) than on other treatments. Leaf explants were also cultured on MS not supplemented with growth regulators or supplemented with 11.4 μM IAA in combination with 0, 2.2, 4.4 or 8.8 μM BA. Shoots were visible within 21–35 days and one plant was successfully rooted on MS medium supplemented with 5.4 μM NAA. Shoot regeneration on MS medium augmented with 11.4 μM IAA and 2.2 μM BA was significantly higher (P < 0.05) than the other treatments according to analysis of variance (ANOVA) with a rank transformation. Hyperhydricity and rooting of shoots was problematic for explants derived from flower receptacles and leaf tissue, but viable plants were regenerated using both explants sources indicating the potential role for micropropagation in the ex situ conservation of the species.