Male Age and Wolbachia Dynamics: Investigating How Fast and Why Bacterial Densities and Cytoplasmic Incompatibility Strengths Vary

Wolbachia bacteria are the most common animal-associated endosymbionts due in large part to their manipulation of host reproduction. Many Wolbachia cause cytoplasmic incompatibility (CI) that kills uninfected host eggs.

Schistosoma mansoni infection reprograms the metabolic potential of the myeloid lineage in a mouse model of metabolic syndrome

SummaryDespite evidence that helminths protect from metabolic disease, a major gap exists in understanding the underlying mechanism(s). Here we demonstrate that bone marrow derived macrophages (BMDM) from S. mansoni infected male ApoE-/- mice have dramatically increased mitochondrial respiration compared to those from uninfected mice. This change associates with increased glucose and palmitate shuttling into TCA cycle intermediates and decreased accumulation of cellular cholesterol esters. Moreover, systemic metabolic modulation by schistosomes is a function of biological sex, where infection protects ApoE-/- male, but not female, mice from obesity and glucose intolerance. Sex-dependence extends to myeloid cells, where reprogramming leads to opposite cholesterol phenotypes in BMDM from females and males. Finally, the metabolic reprogramming of male myeloid cells is transferrable via bone marrow transplantation to an uninfected host, indicating maintenance of reprogramming in the absence of sustained antigen exposure. This work reveals that S. mansoni systemic reprograming of myeloid metabolism is sex-dependent.

How pirate phage interferes with helper phage: Comparison of the two distinct strategies

Pirate phages use the structural proteins encoded by unrelated helper phages to propagate. The best-studied example is the pirate P4 and helper P2 of coliphages, and it has been known that theStaphylococcus aureuspathogenicity islands (SaPIs) that can encode virulence factors act as pirate phages, too. When alone in the host, the pirate phages act as a prophage, but when the helper phage gene is also in the same host cell, the pirate phage has ability to exploit the helper phages structural proteins to produce pirate phage particles and spread, interfering with the helper phage production. The known helper phages in these systems are temperate phages. Interestingly, the interference of the pirate phage to the helper phage occurs in a different manner between the SaPI-helper system and the P4-P2 system. SaPIs cannot lyse a helper lysogen upon infection, while when a helper phage lyse a SaPI lysogen, most of the phage particles produced are the SaPI particles. On the contrary, in the P4-P2 system, a pirate phage P4 can lyse a helper P2 lysogen to produce mostly the P4 particles, while when P2 phage lyses a P4 lysogen, most of the produced phages are the P2 particles. Here, the consequences of these different strategies in the pirate and helper phage spreading among uninfected host is analyzed by using mathematical models. It is found that SaPI’s strategy interferes with the helper phage spreading significantly more than the P4’s strategy, because SaPI interferes with the helper phage’s main reproduction step, while P4 interferes only by forcing the helper lysogens to lyse. However, the interference is found to be weaker in the spatially structured environment than in the well-mixed environment. This is because, in the spatial setting, the system tends to self-organize so that the helper phages take over the front of propagation due to the need of helper phage for the pirate phage spreading.Competing interestsThe author declares no competing interest.

Gallid Herpesvirus 1 Initiates Apoptosis in Uninfected Cells through Paracrine Repression of p53

ABSTRACTApoptosis is a common innate defense mechanism of host cells against viral infection and is therefore suppressed by many viruses, including herpes simplex virus (HSV), via various strategies. A recentin vivostudy reported the apoptosis of remote uninfected cells during Gallid herpesvirus 1 (GaHV-1) infection, yet little is known about this previously unknown aspect of herpesvirus-host interactions. The aim of the present study was to investigate the apoptosis of uninfected host cells during GaHV-1 infection. The present study usedin vitroandin ovomodels, which avoided potential interference by host antiviral immunity, and demonstrated that this GaHV-1–host interaction is independent of host immune responses and important for both the pathological effect of viral infection and early viral dissemination from the primary infection site to distant tissues. Further, we revealed that GaHV-1 infection triggers this process in a paracrine-regulated manner. Using genome-wide transcriptome analyses in combination with a set of functional studies, we found that this paracrine-regulated effect requires the repression of p53 activity in uninfected cells. In contrast, the activation of p53 not only prevented the apoptosis of remote uninfected cells and subsequent pathological damage induced by GaHV-1 infection but also delayed viral dissemination significantly. Moreover, p53 activation repressed viral replication bothin vitroandin ovo, suggesting that dual cell-intrinsic mechanisms underlie the suppression of GaHV-1 infection by p53 activation. This study uncovers the mechanism underlying the herpesvirus-triggered apoptosis of remote host cells and extends our understanding of both herpesvirus-host interactions and the roles of p53 in viral infection.IMPORTANCEIt is well accepted that herpesviruses suppress the apoptosis of host cells via various strategies to ensure sustained viral replication during infection. However, a recentin vivostudy reported the apoptosis of remote uninfected cells during GaHV-1 infection. The mechanism and the biological meaning of this unexpected herpesvirus-host interaction are unclear. This study uncovers the mechanisms of herpesvirus-triggered apoptosis in uninfected cells and may also contribute to a mechanistic illustration of paracrine-regulated apoptosis induced by other viruses in uninfected host cells.

Ex Situ Propagation of Philippine Rafflesia in the United States: Challenges and Prospects

The large-flowered parasitic genus Rafflesia R.Br. (Rafflesiaceae) has long fascinated naturalists and scientists and is an iconic symbol for plant conservation. Techniques to effectively propagate members of the genus outside of their natural habitat are sparse, and grafting infected Tetrastigma K.Schum.(Vitaceae) host plants has previously been reported as a successful strategy for ex situ conservation of Rafflesia. Here we report our attempts in the United States to propagate host cuttings infected with Rafflesia speciosa Barcelona & Fernando and R. lagascae Blanco collectedfrom the Philippines, as well as uninfected host material. We also describe efforts to germinate R. speciosa seeds in vitro using various plant growth regulators (PGRs). After rooting, infected host cuttings survived for a maximum of 11 months, but did not produce shoots. However, an uninfected cutting of T. cf. magnum grafted onto an established Malaysian species of Tetrastigma in June 2017 has succeeded in the commencement of new growth. Three propagules of a second potential host, T. harmandii Planch., have also been vigorously growing at the United States Botanic Garden since June 2017. However, Rafflesia seeds did not germinate with the application of PGRs, even though the seeds were viable according to tetrazolium (TZ) testing.These ex situ propagation attempts have revealed challenges in propagating these species outside of their native ranges, but our incremental success in rooting infected Tetrastigma, as well as grafting interspecific Tetrastigma species, bodes well for further advances. With Philippine host species, T. harmandii and T. cf. magnum in cultivation, we can begin using these specimens for future experimentation involving grafting of infected material and Rafflesia seed inoculation trials.Furthermore, we describe new avenues of propagation techniques for Rafflesia as practised by Marius Gabin, one of the owners of the Vivian Rafflesia garden, which contains a natural Rafflesia forest habitat at Poring Springs, Sabah, Malaysia. Gabin openly shared his successes in artificially inoculating Rafflesia seeds into a mature Tetrastigma vine. Gabin’s willingness to share his experience highlights the importance of collaborating with practitioners who have developed local knowledge of Rafflesia horticulture and conservation.

In vitro Biofilm Formation Ability of Clinical Isolates of Salmonella enterica Serovars Typhi and Paratyphi

In the present study the ability of clinical isolates of Salmonella enterica serovars Typhi (n = 30) and Paratyphi A (n = 11) to form biofilm on abiotic surface was investigated. All isolates were found capable of biofilm formation in a microtitre plate assay. Upon optimization of biofilm formation by the test isolates, Adherence test medium (ATM) was found to be the best medium for biofilm formation by both S. enterica serovars Typhi and Paratyphi. Growth was optimized by incubation at 37°C in an orbital shaker set at 150 rpm for 48-72 hours. Biofilms were best detected when washed with PBS (1X), stained with crystal violet (1%) and subsequently washed with acetone (33%). Optical density (OD) readings were better correlated with growth at 570 nm when compared to 600 nm. Of the 28 Salmonella Typhi isolates, 17 (61%) were very strong biofilm producers, 8 (29%) were strong biofilm producers and 3 (11%) were moderate biofilm producers. On the other hand, out of 13 S. Paratyphi, 9 (69%) were very strong biofilm producers, 3 (23%) were strong biofilm formers and 1 (8%) was a moderate biofilm producer. None of them were weak biofilm producers. The present study raises concern from a public health point of view because the ability of the clinical isolates to form biofilm would indicate their ability of being transmitted from abiotic surface to uninfected host giving rise to disease.Bangladesh J Microbiol, Volume 31, Number 1-2,June-Dec 2014, pp 35-39

Toxoplasma gondii peptide ligands open the gate of the HLA class I binding groove

HLA class I presentation of pathogen-derived peptide ligands is essential for CD8+ T-cell recognition of Toxoplasma gondii infected cells. Currently, little data exist pertaining to peptides that are presented after T. gondii infection. Herein we purify HLA-A*02:01 complexes from T. gondii infected cells and characterize the peptide ligands using LCMS. We identify 195 T. gondii encoded ligands originating from both secreted and cytoplasmic proteins. Surprisingly, T. gondii ligands are significantly longer than uninfected host ligands, and these longer pathogen-derived peptides maintain a canonical N-terminal binding core yet exhibit a C-terminal extension of 1–30 amino acids. Structural analysis demonstrates that binding of extended peptides opens the HLA class I F’ pocket, allowing the C-terminal extension to protrude through one end of the binding groove. In summary, we demonstrate that unrealized structural flexibility makes MHC class I receptive to parasite-derived ligands that exhibit unique C-terminal peptide extensions.

Host Cells Participate in the In Vitro Effects of Novel Diamidine Analogues against Tachyzoites of the Intracellular Apicomplexan Parasites Neospora caninum and Toxoplasma gondii

ABSTRACT The in vitro effects of 19 dicationic diamidine derivatives against the proliferative tachyzoite stages of the apicomplexan parasites Neospora caninum and Toxoplasma gondii were investigated. Four compounds (DB811, DB786, DB750, and DB766) with similar structural properties exhibited profound inhibition of tachyzoite proliferation. The lowest 50% inhibitory concentrations were found for DB786 (0.21 μM against Neospora and 0.22 μM against Toxoplasma) and DB750 (0.23 μM against Neospora and 0.16 μM against Toxoplasma), with complete proliferation inhibition at 1.7 μM for both drugs against both species. DB750 and DB786 were chosen for further studies. Electron microscopy of N. caninum-infected human foreskin fibroblast (HFF) cultures revealed distinct alterations and damage of parasite ultrastructure upon drug treatment, while host cells remained unaffected. For true parasiticidal efficacy against N. caninum, a treatment duration of 3 h at 1.7 μM was sufficient for DB750, while a longer treatment period (24 h) was necessary for DB786. Pretreatment of tachyzoites for 1 h prior to host cell exposure had no effect on infectivity. However, pretreatment of uninfected host cells had a significant adverse effect on N. caninum proliferation: exposure of HFFs to 1.7 μM DB750 for 6, 12, or 24 h, followed by infection with N. caninum tachyzoites and subsequent culture in the absence of DB750, resulted in significantly delayed parasite proliferation. This suggests that either (i) these compounds or their respective active metabolites were still present after the removal of the drugs or (ii) the drug treatments reversibly impaired some functional activities in HFFs that were essential for parasite proliferation and/or survival.

Infection density of Wolbachia endosymbiont affected by co-infection and host genotype

Infection density is among the most important factors for understanding the biological effects of Wolbachia and other endosymbionts on their hosts. To gain insight into the mechanisms of infection density regulation, we investigated the adzuki bean beetles Callosobruchus chinensis and their Wolbachia endosymbionts. Double-infected, single-infected and uninfected host strains with controlled nuclear genetic backgrounds were generated by introgression, and infection densities in these strains were evaluated by a quantitative polymerase chain reaction technique. Our study revealed previously unknown aspects of Wolbachia density regulation: (i) the identification of intra-specific host genotypes that affect Wolbachia density differently and (ii) the suppression of Wolbachia density by co-infecting Wolbachia strains. These findings shed new light on symbiont–symbiont and host–symbiont interactions in the Wolbachia –insect endosymbiosis and strongly suggest that Wolbachia density is determined through a complex interaction between host genotype, symbiont genotype and other factors.