Novel Rickettsiella Bacterium in the Leafhopper Orosius albicinctus (Hemiptera: Cicadellidae)

Bacteria in the genus Rickettsiella (Coxiellaceae), which are mainly known as arthropod pathogens, are emerging as excellent models to study transitions between mutualism and pathogenicity. The current report characterizes a novel Rickettsiella found in the leafhopper Orosius albicinctus (Hemiptera: Cicadellidae), a major vector of phytoplasma diseases in Europe and Asia. Denaturing gradient gel electrophoresis (DGGE) and pyrosequencing were used to survey the main symbionts of O. albicinctus, revealing the obligate symbionts Sulcia and Nasuia, and the facultative symbionts Arsenophonus and Wolbachia, in addition to Rickettsiella. The leafhopper Rickettsiella is allied with bacteria found in ticks. Screening O. albicinctus from the field showed that Rickettsiella is highly prevalent, with over 60% of individuals infected. A stable Rickettsiella infection was maintained in a leafhopper laboratory colony for at least 10 generations, and fluorescence microscopy localized bacteria to accessory glands of the female reproductive tract, suggesting that the bacterium is vertically transmitted. Future studies will be needed to examine how Rickettsiella affects host fitess and its ability to vector phytopathogens.     

Evasion by Stealth: Inefficient Immune Activation Underlies Poor T Cell Response and Severe Disease in SARS-CoV-Infected Mice

Severe Acute Respiratory Syndrome caused substantial morbidity and mortality during the 2002–2003 epidemic. Many of the features of the human disease are duplicated in BALB/c mice infected with a mouse-adapted version of the virus (MA15), which develop respiratory disease with high morbidity and mortality. Here, we show that severe disease is correlated with slow kinetics of virus clearance and delayed activation and transit of respiratory dendritic cells (rDC) to the draining lymph nodes (DLN) with a consequent deficient virus-specific T cell response. All of these defects are corrected when mice are treated with liposomes containing clodronate, which deplete alveolar macrophages (AM). Inhibitory AMs are believed to prevent the development of immune responses to environmental antigens and allergic responses by interacting with lung dendritic cells and T cells. The inhibitory effects of AM can also be nullified if mice or AMs are pretreated with poly I:C, which directly activate AMs and rDCs through toll-like receptors 3 (TLR3). Further, adoptive transfer of activated but not resting bone marrow–derived dendritic cells (BMDC) protect mice from lethal MA15 infection. These results may be relevant for SARS in humans, which is also characterized by prolonged virus persistence and delayed development of a SARS-CoV-specific immune response in individuals with severe disease.     

Long-term effects of dexamethasone and nerve growth factor on adrenal medullary cells cultured from young adult rats

Summary Normal postnatal rat chromaffin cells and rat pheochromocytoma cells are known to show extensive Nerve Growth Factor (NGF)-induced process outgrowth in culture, and this outgrowth from the postnatal chromaffin cells is abolished by the corticosteroid dexamethasone. To determine whether adult rat chromaffin cells respond to NGF and dexamethasone, dissociated adrenal medullary cells from 3-month-old rats were cultured for 30 days in the presence or absence of these agents. Such cultures contained typical chromaffin cells, chromaffin cells with processes, and neurons. Fewer than 2 % of normal adult chromaffin cells formed processes under any of the conditions studied, and statistically significant changes in this proportion were not detectable in the presence of NGF or dexamethasone. Adrenal medullary neurons, however, were observed only in the presence of NGF, in cultures with or without dexamethasone, and thus appear to be previously unreported NGF targets which require NGF for survival or process outgrowth. Dexamethasone markedly increased total catecholamine content, total content of epinephrine, and tyrosine hydroxylase activity in cultures with or without NGF. In contrast, postnatal rat chromaffin and rat pheochromocytoma cells which have been studied in culture do not produce epinephrine under any of these conditions. It is concluded that rat adrenal chromaffin cells undergo age-related changes in both structural and functional plasticity. The in vitro characteristics of rat pheochromocytoma cells more closely resemble those of postnatal than of adult rat chromaffin cells, but may not entirely reflect the properties of the majority of chromaffin cells in either age group.     

HSV-2 Co-Infection as a Driver of HIV Transmission among Heterosexual Non-Injecting Drug Users in New York City

Objective

To examine herpes simplex virus 2 (HSV-2)/HIV co-infection as a contributing factor in the increase in HIV infection among non-injecting heroin and cocaine users in New York City.

Methods

Subjects were recruited from the Beth Israel Medical Center drug detoxification and methadone maintenance programs in New York City in 1995–1999 and 2005–2011. All reported current heroin and/or cocaine use and no injection drug use. A structured questionnaire was administered and serum samples collected for HIV and HSV-2 testing. Population-attributable risk percentages (PAR%s) were estimated for associations between HSV-2 and increased susceptibility to and increased transmissibility of HIV among female NIDUs.

Results

785 subjects were recruited from 1995–1999, and 1764 subjects from 2005–2011. HIV prevalence increased from 7% to 13%, with nearly uniform increases among all demographic subgroups. HSV-2/HIV co-infection was common in both time periods, with an average (over the two time periods) of 80% of HIV negative females infected with HSV-2, an average of 43% of HIV negative males infected with HSV-2; an average of 97% of HIV positive females also infected with HSV-2 and an average of 67% of HIV positive males also infected with HSV-2. The increase in HIV prevalence was predominantly an increase in HSV-2/HIV co-infection, with relatively little HIV mono-infection in either time period. The estimated PAR%s indicate that approximately half of HIV acquisition among females was caused by HSV-2 infection and approximately 60% of HIV transmission from females was due to HSV-2 co-infection.

Conclusions

The increase in HIV infection among these non-injecting drug users is better considered as an increase in HSV-2/HIV co-infection rather than simply an increase in HIV prevalence. Additional interventions (such as treatment as prevention and suppressing the effects of HSV-2 on HIV transmission) are needed to reduce further HIV transmission from HSV-2/HIV co-infected non-injecting drug users.     

The fermentation of L-sorbose by Gluconobacter melanogenus. I. General characteristics of the fermentation

Growing cultures, washed cells, and cell-free preparations of Gluconobacter melanogecnus IFO 3293 converted L -sorbose to 2-keto-L -gulonic acid, to D -sorbitol (which was metabolized further) and to 5-keto-D -fructose.     

Mutational bisection of the mitochondrial DNA stability and amino acid biosynthetic functions of ilv5p of budding yeast

Ilv5p is a bifunctional yeast mitochondrial enzyme required for branched chain amino acid biosynthesis and for the stability of mitochondrial DNA (mtDNA) and its parsing into nucleoids. The latter occurs when the general amino acid control (GAC) pathway is activated. We have isolated ilv5 mutants that lack either the enzymatic (a(-)D(+)) or the mtDNA stability function (a(+)D(-)) of the protein. The affected residues in these two mutant classes cluster differently when mapped to the 3-D structure of the spinach ortholog of Ilv5p. a(-)D(+) mutations map to conserved internal domains known to be important for substrate and cofactor binding, whereas the a(+)D(-) mutations map to a C-terminal region on the surface of the protein. The a(+)D(-) mutants also have a temperature-sensitive phenotype when grown on a glycerol medium, which correlates with their degree of mtDNA instability. Analysis of an a(+)D(-) mutant with a strong mtDNA instability phenotype shows that it is also unable to parse mtDNA into nucleoids when activated by the GAC pathway. Finally, the wild-type Escherichia coli ortholog of Ilv5p behaves like a(+)D(-) mutants when expressed and targeted to mitochondria in ilv5Delta yeast cells, suggesting that yeast Ilv5p acquired its mtDNA function after the endosymbiotic event.     

The emerging diversity of Rickettsia

The best-known members of the bacterial genus Rickettsia are associates of blood-feeding arthropods that are pathogenic when transmitted to vertebrates. These species include the agents of acute human disease such as typhus and Rocky Mountain spotted fever. However, many other Rickettsia have been uncovered in recent surveys of bacteria associated with arthropods and other invertebrates; the hosts of these bacteria have no relationship with vertebrates. It is therefore perhaps more appropriate to consider Rickettsia as symbionts that are transmitted vertically in invertebrates, and secondarily as pathogens of vertebrates. In this review, we highlight the emerging diversity of Rickettsia species that are not associated with vertebrate pathogenicity. Phylogenetic analysis suggests multiple transitions between symbionts that are transmitted strictly vertically and those that exhibit mixed (horizontal and vertical) transmission. Rickettsia may thus be an excellent model system in which to study the evolution of transmission pathways. We also focus on the emergence of Rickettsia as a diverse reproductive manipulator of arthropods, similar to the closely related Wolbachia, including strains associated with male-killing, parthenogenesis, and effects on fertility. We emphasize some outstanding questions and potential research directions, and suggest ways in which the study of non-pathogenic Rickettsia can advance our understanding of their disease-causing relatives.     

Length changes in the joining segment between domains 5 and 6 of a group II intron inhibit self-splicing and alter 3' splice site selection.

Domain 5 (D5) and domain 6 (D6) are adjacent folded hairpin substructures of self-splicing group II introns that appear to interact within the active ribozyme. Here we describe the effects of changing the length of the 3-nucleotide segment joining D5 to D6 [called J(56)3] on the splicing reactions of intron 5 gamma of the COXI gene of yeast mitochondrial DNA. Shortened variants J(56)0 and J(56)1 were defective in vitro for branching, and the second splicing step was performed inefficiently and inaccurately. The lengthened variant J(56)5 had a milder defect-splicing occurred at a reduced rate but with correct branching and a mostly accurate 3' splice junction choice. Yeast mitochondria were transformed with the J(56)5 allele, and the resulting yeast strain was respiration deficient because of ineffective aI5 gamma splicing. Respiration-competent revertants were recovered, and in one type a single joiner nucleotide was deleted while in the other type a nucleotide of D6 was deleted. Although these revertants still showed partial splicing blocks in vivo and in vitro, including a substantial defect in the second step of splicing, both spliced accurately in vivo. These results establish that a 3-nucleotide J(56) is optimal for this intron, especially for the accuracy of 3' splice junction selection, and indicate that D5 and D6 are probably not coaxially stacked.