Diversity of Gut Microbiota Metabolic Pathways in 10 Pairs of Chinese Infant Twins.

Early colonization of gut microbiota in human gut is a complex process. It remains unclear when gut microbiota colonization occurs and how it proceeds. In order to study gut microbiota composition in human early life, the present study recruited 10 healthy pairs of twins, including five monozygotic (MZ) and five dizygotic (DZ) twin pairs, whose age ranged from 0 to 6 years old. 20 fecal samples from these twins were processed by shotgun metagenomic sequencing, and their averaged data outputs were generated as 2G per sample. We used MEGAN5 to perform taxonomic and functional annotation of the metagenomic data, and systematically analyzed those 20 samples, including Jaccard index similarity, principle component, clustering, and correlation analyses. Our findings indicated that within our study group: 1) MZ-twins share more microbes than DZ twins or non-twin pairs, 2) gut microbiota distribution is relatively stable at metabolic pathways level, 3) age represents the strongest factor that can account for variation in gut microbiota, and 4) a clear metabolic pathway shift can be observed, which speculatively occurs around the age of 1 year old. This research will serve as a base for future studies of gut microbiota-related disease research.

Spiroplasma spp. biofilm formation is instrumental for their role in the pathogenesis of plant, insect and animal diseases.

Spiroplasma spp. are important phyto and insect pathogens, and candidate causal agent/s of transmissible spongiform encephalopathies (TSE) in man and animals. These filterable wall-less bacteria are widely distributed in nature with an unspecified environmental reservoir. In this study we showed by scanning electron microscopy that spiroplasma form biofilm on an assortment of hard surfaces including mica, nickel and stainless steel. Spiroplasma were stuck to the surfaces by fibrillar threads consistent with curli fibers (an amyloid protein found in bacterial biofilms). After a lengthy time in cultures (6 weeks), spiroplasma in biofilm bound to mica disks lost their spiral shapes and formed coccoid forms interconnected by long (>2 µm) branched membranous nanotubules, therein representing direct conjugate connections between the cells. The affinity of spiroplasma biofilms for mica and nickel, and the membrane communications suggest that soil could be a reservoir for these bacteria. The persistence of clay bound spiroplasma in soil could serve as the mechanism of lateral spread of TSEs by ingestion of soil by ruminants. Spiroplasma binding to stainless steel wire supports bacterial contamination of surgical instruments following surgery on dementia patients as a mechanism of iatrogenic transmission of TSEs, especially with resistance of spiroplasma in biofilms to drying or exposure to 50% glutaraldehyde. The discovery of biofilm formation by spiroplasma addresses questions regarding environmental persistence of these organisms in nature and suggests novel mechanisms of intercellular communication and transmission.

Dementias, neurodegeneration, and viral mechanisms of disease from the perspective of human transmissible encephalopathies.

Our transmission experiments with human CJD emphasize the centrality of an exogenous infectious pathogen that can exist in symbiosis with its host for extended periods. Many latent or persistent viruses can cause neurodegenerative disease and may have a role in late onset dementias. There are reasons to believe that CJD infections may share properties with some of these latent viruses in causing dementia, and several retroviral mechanisms may be operative in CJD. In order to clarify viral-like attributes of the CJD agent we have closely followed infectivity and find the following: 1) the CJD agent has a virus-like size and density, and is biochemically separable from most host-encoded prion protein (PrP); 2) Endogenous retroviral IAP RNA sequences of 5,000 bases, as well as several gag-like nucleic acid binding proteins, co-purify with infectivity in preparations treated with high concentrations of anionic detergents and exhaustive nuclease digestion. They signify the purification of true viral cores rather than aggregation artifacts, and diminish claims that there are no protected nucleic acids of > 50 bases in highly purified infectious preparations; 3) In established hamster CJD, temporal studies show the agent has an effective doubling time of approximately 7.5 days in brain, consistent with complex host-viral interactions common to slow viral infections; 4) PrP-res does not correspond to titered levels of infectivity either in a biochemical or an in vivo setting but may function as a viral receptor that can modulate disease expression. Interestingly, functional changes in glial cells occur earlier than PrP-res changes, and indicate an important role for glial cells in evolving infections; 5) Human-rodent transmission studies suggest that CJD, or a CJD-like variant can be a common but latent infection of humans, with relatively infrequent expression of neurological disease. Susceptibility to disease can rest on host attributes and possibly age-related co-factors. Nonetheless, fundamental viral principles are also operative. Agent strain variants, viral burden, and the routes of infection are critical parameters for latency and disease expression. The properties described above have led me to return to the inclusion of CJD (and scrapie) in the panorama of conventional slow viral infections of the brain, as originally proposed by Sigurdsson. Identification of virus-specific molecules are essential for elucidating the role of these agents in the spectrum of human dementias.

Kinetic analysis of spongiform neurodegenerative disease induced by a highly virulent murine retrovirus.

BACKGROUND: A chimeric murine retrovirus, FrCasE, causes a rapid noninflammatory spongiform neurodegenerative disease of the motor system with an incubation period of 15 to 16 days after neonatal inoculation. Neurovirulence is determined by the viral envelope gene, but the neurodegeneration is an indirect consequence of virus infection, because the neurons that degenerate appear not to be infected. EXPERIMENTAL DESIGN: The current study was undertaken to compare the kinetics of lesion development and the expression of viral envelope protein in the central nervous system (CNS). Neonatal mice were inoculated with FrCasE intraperitoneally and were killed at various times for determination of the kinetics of the CNS infection, the distribution of lesion in the CNS, and the distribution of viral envelope protein. In addition, qualitative features of both viral envelope and gag proteins were followed by immunoblot analysis. RESULTS: The lesions induced by FrCasE consisted of vacuolar degeneration but without associated astrocytosis, the lack of an astroglial response being a consequence of the rapidity of the disease process. Vacuoles were observed primarily in the neuropil of the motor centers of spinal cord, brain stem, and cerebral cortex. Lesions appeared in all of these areas during a narrow window of time (< or = 3 days). Cells in which viral envelope protein was detected by immunohistochemistry before the appearance of spongiform degeneration included premigratory cerebellar cortical granule neurons as well as vascular elements in the regions that would ultimately exhibit spongiform degeneration. Two forms of viral envelope protein were detected in the CNS. A 70-kilodalton species appeared first, followed by an approximately 64-kilodalton species, which was detected coincident with the first appearance of spongiform lesions. CONCLUSIONS: Astrocytosis is a secondary reaction to the neuronal cytopathology induced by FrCasE and appears to be dependent on the developmental state of the CNS. The abrupt, diffuse nature of lesion development in this disease suggests a global effect of the virus infection. Cells of the CNS vasculature (either endothelial cells, perivascular microglial cells, or both) as well as cerebellar granule neurons appear to be seminally involved in the pathogenesis of the spongiform degeneration. The two species of viral envelope protein appear to be expressed by different cell types in the CNS.

Identification of the infected target cell type in spongiform myeloencephalopathy induced by the neurotropic Cas-Br-E murine leukemia virus.

The Cas-Br-E murine leukemia virus (MuLV) induces a progressive hindlimb paralysis accompanied by a spongiform myeloencephalopathy in susceptible mice. In order to better understand the pathological process leading to these neurodegenerative lesions, we have investigated the nature of the cell type(s) infected by the virus during the course of the disease in CFW/D and SWR/J mice. For this purpose, we used in situ hybridization with virus-specific probes in combination with cell-type-specific histochemical (lectin) and immunological markers as well as morphological assessment. In the early stage of infection, endothelial cells represented the main cell type expressing viral RNA in the central nervous system (CNS). With disease progression and the appearance of lesions, microglial cells became the major cell type infected, accounting for up to 65% of the total infected cell population in diseased areas. Morphologically, these cells appeared activated and were frequently found in clusters. Infection and activation of microglial cells were almost exclusively restricted to diseased regions of the CNS. Neurons in diseased regions were not discernibly infected with virus at either early or late times of disease progression. Similarly, the proportion of infected astrocytes was typically < 1%. Although some endothelial cells and oligodendrocytes were infected by the virus, their infection was not limited to diseased CNS regions. These results are consistent with a model of indirect motor neuron degeneration, subsequent to the infection of nonneuronal CNS cells and especially of microglial cells. Infected microglial cells may play a role in the disease process by releasing not only virions or viral env-gene-encoded gp70 proteins but also other factors which may be directly or indirectly toxic to neurons. Parallels between microglial cell infection by MuLV and by lentiviruses, and specifically by human immunodeficiency virus, are discussed.

Neurological disease induced in transgenic mice expressing the env gene of the Cas-Br-E murine retrovirus.

The Cas-Br-E murine leukemia virus induces a spongiform myeloencephalopathy in susceptible mice. We constructed transgenic mice harboring either the viral genome (in a replication-defective form) or only its env gene. Low levels of expression of either transgene resulted in mild neuropathology and/or signs of neurological disease in more than half of these mice. These results indicate that the disease can occur in the absence of virus replication and strongly suggest that the env gp70/p15E complex is sufficient to induce disease.

Hidden amyloidoses.

The pathogenesis as well as the genetic disposition to develop clinical symptoms in transmissible spongiform encephalopathies (e.g. Creutzfeldt-Jakob disease, scrapie, bovine spongiform encephalopathy) relate these diseases to classical noninfectious amyloidoses (familial amyloidotic polyneuropathy as an example) and to Alzheimer's disease. This is not obvious to the nonexpert at first glance. This communication tries to elucidate this association, to reveal which immunochemical techniques have contributed their share.

Amyloidoses of the nervous system in the transmissible dementias.

The transmissible spongiform encephalopathies, both in humans and in animals, are neurodegenerative diseases which do not evoke an immune response in the host. The search for the etiological agent has led to the prion hypothesis, which proposes that a host-encoded protein may be the causal agent itself or a part of it. In humans, a low percentage of these transmissible encephalopathies are familial. Investigations centered on the understanding of the pathogenesis of the transmissible spongiform encephalopathies have implications, not only in basic sciences, but in clinical medicine as well.