Speculations on the karyological relationship of the Old World Primates

Data on number and morphology of chromosomes on the Old World Primates suggest the existence of three major lines of chromosomal evolution. Connection among these three lines are hypothetized on the basis of a comparison of the so-called “marked” chromosomes.     

The Bacterial Symbiont Wolbachia Induces Resistance to RNA Viral Infections in Drosophila melanogaster

Wolbachia are vertically transmitted, obligatory intracellular bacteria that infect a great number of species of arthropods and nematodes. In insects, they are mainly known for disrupting the reproductive biology of their hosts in order to increase their transmission through the female germline. In Drosophila melanogaster, however, a strong and consistent effect of Wolbachia infection has not been found. Here we report that a bacterial infection renders D. melanogaster more resistant to Drosophila C virus, reducing the load of viruses in infected flies. We identify these resistance-inducing bacteria as Wolbachia. Furthermore, we show that Wolbachia also increases resistance of Drosophila to two other RNA virus infections (Nora virus and Flock House virus) but not to a DNA virus infection (Insect Iridescent Virus 6). These results identify a new major factor regulating D. melanogaster resistance to infection by RNA viruses and contribute to the idea that the response of a host to a particular pathogen also depends on its interactions with other microorganisms. This is also, to our knowledge, the first report of a strong beneficial effect of Wolbachia infection in D. melanogaster. The induced resistance to natural viral pathogens may explain Wolbachia prevalence in natural populations and represents a novel Wolbachia–host interaction.     

Cell Surface Measurements in Hydrocarbon and Carbohydrate Fermentations

Acinetobacter calcoaceticus was grown in 11-liter batch fermentations with hexadecane or sodium citrate as the sole source of carbon. Surface and interfacial tension measurements of the microbial broth indicated that surface-active compounds were being produced only during growth on the hydrocarbon substrate. Contact angle measurements of an aqueous drop on a smooth lawn of cells in a hexadecane bath indicated a highly hydrophobic surface of the cells in the initial stages of the hydrocarbon fermentation (120° contact angle). At this stage, the entire cell population was bound to the hydrocarbon-aqueous interface. The contact angle dropped rapidly to approximately 45° after 14 h into the fermentation. This coincided with a shift of the cell population to the aqueous phase. Thus, the cells demonstrated more hydrophilic characteristics in the later stages of the fermentation. Contact angles on cells grown on sodium citrate ranged from 18 to 24° throughout the fermentation. The cells appear to be highly hydrophilic during growth on a soluble substrate. From the contact angle and aqueous-hydrocarbon interfacial tension, the surface free energy of the cells was calculated along with the cell-aqueous and cell-hydrocarbon interfacial tension. The results of these measurements were useful in quantitatively evaluating the hydrophobic nature of the cell surface during growth on hydrocarbons and comparing it with the hydrophilic nature of the cell surface during growth on a soluble substrate.     

甲基化修饰对病毒潜伏感染的调控作用研究进展

病毒在宿主体内所建立的潜伏感染与肿瘤、免疫性疾病等多种疾病的发生和发展密切相关,并直接导致相关疾病很难被彻底治愈.目前,随着潜伏感染调控机制研究的深入,表观遗传修饰在其中扮演的角色也进一步被发现.而甲基化作为其中最重要,也是研究最详尽的调控方式之一,在病毒潜伏感染的建立和维持中也是不可或缺的.本文将分别对DNA、RNA和组蛋白甲基化在病毒潜伏感染中-的调控作用、靶向甲基化修饰的药物在临床治疗中的应用前景等方面进行综述,以期为抗病毒治疗策略的研究提供参考.     

The Role of Anorexia in Resistance and Tolerance to Infections in Drosophila

Most infections induce anorexia but its function, if any, remains unclear. Because this response is common among animals, we hypothesized that infection-induced diet restriction might be an adaptive trait that modulates the host's ability to fight infection. Two defense strategies protect hosts against infections: resistance, which is the ability to control pathogen levels, and tolerance, which helps the host endure infection-induced pathology. Here we show that infected fruit flies become anorexic and that diet restriction alters defenses, increasing the fly's tolerance to Salmonella typhimurium infections while decreasing resistance to Listeria monocytogenes. This suggests that attempts to extend lifespan through diet restriction or the manipulation of pathways mimicking this process will have complicated effects on a host's ability to fight infections.     

A Possible Role of DNA Superstructures in Genome Evolution

The concept of DNA as a simple repository of the gene information has changed in that of a polymorphic macromolecule, which plays a relevant part in the management of the complex biochemical transformations in living matter. As a consequence of the slight stereochemical differences between base pairs, the direction of the DNA double helix axis undergoes deterministic writhing. A useful representation of such sequence-dependent structural distortions is the curvature diagram. Here, it is reported as an evolution simulation obtained by extensive point mutations along a biologically important DNA tract. The curvature changes, consequence of the point mutations. were compared to the related experimental gel electrophoresis mobility. The curvature of most mutants decreases and the mobility increases accordingly, suggesting the curvature of that tract is genetically selected. Moreover, DNA images by scanning force microscopy, show evidence of a sequence-dependent adhesion of curved DNA tracts to inorganic crystal surfaces. In particular, mica shows a large affinity towards the TT-rich dinucleotide sequences. This suggests a possible mechanism of selection of curved DNA regions, characterized by AA.TT dinucleotides in phase with double-helical periodicity, in the very early evolution steps.     

Possible Role of Non-Muscle Alpha-Actinins in Muscle Cell Mechanosensitivity

The main hypothesis suggested that changes in the external mechanical load would lead to different deformations of the submembranous cytoskeleton and, as a result, dissociation of different proteins from its structure (induced by increased/decreased mechanical stress). The study subjects were fibers of the soleus muscle and cardiomyocytes of Wistar rats. Changes in external mechanical conditions were reconstructed by means of antiorthostatic suspension of the animals by their tails for 6, 12, 18, 24 and 72 hours. Transversal stiffness was measured by atomic force microscopy imaging; beta-, gamma-actin, alpha-actinin 1 and alpha-actinin 4 levels in membranous and cytoplasmic fractions were quantified by Western blot analysis; expression rates of the corresponding genes were studied using RT-PCR. Results: In 6 hours, alpha-actinin 1 and alpha-actinin 4 levels decreased in the membranous fraction of proteins of cardiomyocytes and soleus muscle fibers, respectively, but increased in the cytoplasmic fraction of the abovementioned cells. After 6–12 hours of suspension, the expression rates of beta-, gamma-actin, alpha-actinin 1 and alpha-actinin 4 were elevated in the soleus muscle fibers, but the alpha-actinin 1 expression rate returned to the reference level in 72 hours. After 18–24 hours, the expression rates of beta-actin and alpha-actinin 4 increased in cardiomyocytes, while the alpha-actinin 1 expression rate decreased in soleus muscle fibers. After 12 hours, the beta- and gamma-actin content dropped in the membranous fraction and increased in the cytoplasmic protein fractions from both cardiomyocytes and soleus muscle fibers. The stiffness of both cell types decreased after the same period of time. Further, during the unloading period the concentration of nonmuscle actin and different isoforms of alpha-actinins increased in the membranous fraction from cardiomyocytes. At the same time, the concentration of the abovementioned proteins decreased in the soleus muscle fibers.     

Molecular Evolution of Prolactin in Primates

Pituitary prolactin, like growth hormone (GH) and several other protein hormones, shows an episodic pattern of molecular evolution in which sustained bursts of rapid change contrast with long periods of slow evolution. A period of rapid change occurred in the evolution of prolactin in primates, leading to marked sequence differences between human prolactin and that of nonprimate mammals. We have defined this burst more precisely by sequencing the coding regions of prolactin genes for a prosimian, the slow loris (Nycticebus pygmaeus), and a New World monkey, the marmoset (Callithrix jacchus). Slow loris prolactin is very similar in sequence to pig prolactin, so the episode of rapid change occurred during primate evolution, after the separation of lines leading to prosimians and higher primates. Marmoset prolactin is similar in sequence to human prolactin, so the accelerated evolution occurred before divergence of New World monkeys and Old World monkeys/apes. The burst of change was confined largely to coding sequence (nonsynonymous sites) for mature prolactin and is not marked in other components of the gene sequence. This and the observations that (1) there was no apparent loss of function during the episode of rapid evolution, (2) the rate of evolution slowed toward the basal rate after this burst, and (3) the distribution of substitutions in the prolactin molecule is very uneven support the idea that this episode of rapid change was due to positive adaptive selection. In the slow loris and marmoset there is no evidence for duplication of the prolactin gene, and evidence from another New World monkey (Cebus albifrons) and from the chimpanzee and human genome sequences, suggests that this is the general position in primates, contrasting with the situation for GH genes. The chimpanzee prolactin sequence differs from that of human at two residues and comparison of human and chimpanzee prolactin gene sequences suggests that noncoding regions associated with regulating expression may be evolving differently from other noncoding regions.     

Evolution of the antiretroviral restriction factor TRIMCyp in Old World primates

The retroviral restriction factor TRIMCyp, which is a fusion protein derived from the TRIM5 gene, blocks replication at a post-entry step. Among Old World primates, TRIMCyp has been found in four species of Asian macaques, but not in African monkeys. To further define the evolutionary origin of Old World TRIMCyp, we examined two species of baboons (genus Papio) and three additional macaque species, including M. sylvanus, which is the only macaque species found outside Asia, and represents the earliest diverging branch of the macaque lineage. None of four P. cynocephalus anubis, one P. hamadryas, and 36 M. sylvanus had either TRIMCyp mRNA or the genetic features required for its expression. M. sylvanus genomic sequences indicated that the lack of TRIMCyp in this species was not due to genetic homogeneity among specimens studied and revealed the existence of four TRIM5α alleles, all distinct from M. mulatta and Papio counterparts. Together with existing data on macaque evolution, our findings indicate that TRIMCyp evolved in the ancestors of Asian macaques approximately 5-6 million years before present (ybp), likely as a result of a retroviral threat. TRIMCyp then became fixed in the M. nemestrina lineage after it diverged from M. nigra, approximately 2 million ybp. The macaque lineage is unique among primates studied so far due to the presence and diversity of both TRIM5 and TRIMCyp restriction factors. Studies of these antiviral proteins may provide valuable information about natural antiviral mechanisms, and give further insight into the factors that shaped the evolution of macaque species.     

Maintenance of an Old World Betasatellite by a New World Helper Begomovirus and Possible Rapid Adaptation of the Betasatellite

Begomoviruses (family Geminiviridae) cause major losses to crops throughout the tropical regions of the world. Begomoviruses originating from the New World (NW) and the Old World (OW) are genetically distinct. Whereas the majority of OW begomoviruses have monopartite genomes and whereas most of these associate with a class of symptom-modulating satellites (known as betasatellites), the genomes of NW begomoviruses are exclusively bipartite and do not associate with satellites. Here, we show for the first time that a betasatellite (cotton leaf curl Multan betasatellite [CLCuMuB]) associated with a serious disease of cotton across southern Asia is capable of interacting with a NW begomovirus. In the presence of CLCuMuB, the symptoms of the NW cabbage leaf curl virus (CbLCuV) are enhanced in Nicotiana benthamiana. However, CbLCuV was unable to interact with a second betasatellite, chili leaf curl betasatellite. Although CbLCuV can transreplicate CLCuMuB, satellite accumulation levels in plants were low. However, progeny CLCuMuB isolated after just one round of infection with CbLCuV contained numerous mutations. Reinoculation of one such progeny CLCuMuB with CbLCuV to N. benthamiana yielded infections with significantly higher satellite DNA levels. This suggests that betasatellites can rapidly adapt for efficient transreplication by a new helper begomovirus, including begomoviruses originating from the NW. Although the precise mechanism of transreplication of betasatellites by begomoviruses remains unknown, an analysis of betasatellite mutants suggests that the sequence(s) required for maintenance of CLCuMuB by one of its cognate begomoviruses (cotton leaf curl Rajasthan virus) differs from the sequences required for maintenance by CbLCuV. The significance of these findings and, particularly, the threat that betasatellites pose to agriculture in the NW, are discussed.Viruses of the family Geminiviridae are distinct in having genomes of circular, single-stranded DNA (ssDNA) contained within twinned quasi-isometric (“geminate”) virions from which they derive their name. Geminiviruses are divided into four genera based on the organization of their genomes, biological properties, type of insect vector (either whitefly, leafhopper, or treehopper), and host range (either mono- or dicotyledonous hosts) (37). The genus Begomovirus contains the vast majority of the identified geminivirus species, and these are transmitted exclusively by the whitefly Bemisia tabaci (Gennadius) to dicotyledonous plants. All begomoviruses native to the New World (NW) and a small number originating from the Old World (OW) have bipartite genomes (with components known as DNA-A and DNA-B). The majority of the OW begomoviruses have genomes consisting of a single component homologous to the DNA-A component of the bipartite viruses. Begomoviruses from the NW and OW are genetically distinct. They segregate separately in phylogenetic analyses, and the OW viruses show a greater genetic diversity and have an additional, absolutely conserved gene (known as V2 for the monopartite and AV2 for the bipartite viruses) that is absent in the NW begomoviruses.The global trade in agricultural products is leading to the spread of many viruses. The prime example here is tomato yellow leaf curl virus. This monopartite begomovirus has its origins in the Middle East/Mediterranean region but has been inadvertently introduced to the NW, with serious consequences for tomato production across the southern United States (24, 26). Similarly, the NW begomovirus squash leaf curl virus from the southwestern United States has been introduced into the Middle East (2, 20).The majority of OW monopartite begomoviruses are associated with additional ssDNA molecules. The first evidence for this came with the report by Dry et al. (14) of an ssDNA satellite associated with tomato leaf curl virus (ToLCV) occurring in Australia. This molecule was later shown to be a defective (truncated) version of a much larger group of subviral components associated with begomoviruses that are now known collectively as betasatellites (6). Betasatellites are approximately half the size of a begomovirus component (∼1,360 nucleotides [nt]) and are required by the helper begomovirus for efficient infection of some hosts (9, 30, 31). Betasatellites have been shown to be associated with an increasing number of diseases caused by begomoviruses, including many of the most significant, economically damaging diseases occurring in the OW. The most noteworthy of these diseases is cotton leaf curl disease (CLCuD). CLCuD was epidemic during the 1990s across Pakistan and continues to be so in northern India. The disease is caused by a complex consisting of representatives of at least seven distinct begomovirus species and a specific betasatellite (23).Betasatellites have a highly conserved structure although their sequences are highly diverse, with distinct species showing as little as 50% sequence identity (6, 11, 42). They contain a single coding sequence (known as βC1), a region of sequence rich in adenine, and a ∼150-nt region, known as the satellite conserved region (SCR), that is highly conserved between all betasatellites. The SCR contains a predicted hairpin structure that contains within the loop a nonanucleotide sequence (TAATATTAC) that for geminiviruses marks the origin of virion-strand DNA replication. The βC1 gene is a pathogenicity determinant (27, 28, 33) and encodes all satellite functions identified so far, including suppression of RNA-mediated host defense (13) and possibly a role in virus movement (29). For many of the monopartite begomoviruses, the betasatellite is essential for inducing typical disease symptoms in the hosts from which they were isolated (6, 9, 30). However, recently some viruses with less dependence on interaction with their betasatellites have been identified (6).When betasatellites were first identified, their ability to interact with NW begomoviruses was investigated, but no evidence for interaction was found (R.W. Briddon, unpublished results). Here, we report a positive interaction between a betasatellite and the NW cabbage leaf curl virus (CbLCuV). We show that the interaction between the betasatellite and this NW begomovirus leads to rapid sequence changes in the satellite, which enhances its interaction with the virus.     

Lactococcal 949 Group Phages Recognize a Carbohydrate Receptor on the Host Cell Surface

Lactococcal bacteriophages represent one of the leading causes of dairy fermentation failure and product inconsistencies. A new member of the lactococcal 949 phage group, named WRP3, was isolated from cheese whey from a Sicilian factory in 2011. The genome sequence of this phage was determined, and it constitutes the largest lactococcal phage genome currently known, at 130,008 bp. Detailed bioinformatic analysis of the genomic region encoding the presumed initiator complex and baseplate of WRP3 has aided in the functional assignment of several open reading frames (ORFs), particularly that for the receptor binding protein required for host recognition. Furthermore, we demonstrate that the 949 phages target cell wall phospho-polysaccharides as their receptors, accounting for the specificity of the interactions of these phages with their lactococcal hosts. Such information may ultimately aid in the identification of strains/strain blends that do not present the necessary saccharidic target for infection by these problematic phages.     

Possible Role of Macrophage Mediated Nonspecific Cytotoxicity in Tumour Resistance

IN addition to their role in specific tumour immunity^1–3, macrophages seem to be the effector cells in mediating specific and nonspecific resistance to intracellular organisms in mice^4–7, the critical factor being the development of a population of activated macrophages which resist destruction by and are able to destroy intracellular pathogens^4,8. Because resistance to neoplasia seems to be primarily cell mediated, we have investigated whether the nonspecific cell-mediated resistance conferred by chronic intracellular protozoal infection provides protection against tumours. These infections conferred resistance to a variety of autochthonous and transplantable murine tumours^9,10. Since the mechanism of resistance to tumours and unrelated infectious agents in the protozoan-infected mice might be similar, the effect of activated macrophages on target cells was evaluated. The results demonstrated that peritoneal macrophages from mice chronically infected with Toxoplasma have the capacity to non-specifically destroy target cells in vitro by a nonphagocytic mechanism.     

Noninvasive Assessment of Gastrointestinal Parasite Infections in Free-Ranging Primates

Recent evidence of emerging human diseases with origins or likely transmission to humans, or both, that involve primates and a greater recognition of the risk of human pathogen transmission to free-ranging primates have raised awareness of the potential impact of zoonotic pathogen transmission on primate conservation and nonhuman primate and human health. As human population density continues to increase exponentially, speeding the reduction and fragmentation of primate habitats, greater human-primate contact is inevitable and even higher rates of pathogen transmission are likely. Thus interest has grown in collecting baseline data on patterns of parasitic infections in wild primate populations to provide an index of population health and to begin to assess and, to manage disease risks. Primatologists traditionally have been involved with such surveys through noninvasive assessment of gastrointestinal parasites. Unfortunately, previous studies have tended toward divergent methodologies, compromising the potential for longitudinal and comparative work. Here, I provide practical guidelines and standardized methodologies for the noninvasive assessment of gastrointestinal parasites of primates.

RNase L Triggers Autophagy in Response to Viral Infections

Autophagy is a programmed homeostatic response to diverse types of cellular stress that disposes of long-lived proteins, organelles, and invading microbes within double-membraned structures called autophagosomes. The 2′,5′-oligoadenylate/RNase L system is a virus-activated host RNase pathway that disposes of or processes viral and cellular single-stranded RNAs. Here we report that activation of RNase L during viral infections induces autophagy. Accordingly, infections with encephalomyocarditis virus or vesicular stomatitis virus led to higher levels of autophagy in wild-type mouse embryonic fibroblasts (MEF) than in RNase L-null MEF. Similarly, direct activation of RNase L with a 2′,5′-oligoadenylate resulted in p62(SQSTM1) degradation, LC3BI/LC3BII conversion, and appearance of autophagosomes. To determine the effect of RNase L-mediated autophagy on viral replication, we compared viral yields in wild-type and RNase L-null MEF in the absence or presence of either chemical inhibitors of autophagy (bafilomycin A1 or 3-methyladenine) or small interfering RNA (siRNA) against ATG5 or beclin-1. At a low multiplicity of infection, induction of autophagy by RNase L during the initial cycle of virus growth contributed to the suppression of virus replication. However, in subsequent rounds of infection, autophagy promoted viral replication, reducing the antiviral effect of RNase L. Our results indicate a novel function of RNase L as an inducer of autophagy that affects viral yields.     

Host Immune Responses to Chronic Adenovirus Infections in Human and Nonhuman Primates

Recent studies indicate that great apes and macaques chronically shed adenoviruses in the stool. Shedding of adenovirus in the stool of humans is less prevalent, although virus genomes persist in gut-associated lymphoid tissue in the majority of individual samples. Chimpanzees have high levels of broadly reactive neutralizing antibodies to adenoviruses in serum, with very low frequencies of adenovirus-specific T cells in peripheral blood. A similar situation exists in macaques; sampling of guts from macaques demonstrated adenovirus-specific T cells in lamina propria. Humans show intermediate levels of serum neutralizing antibodies, with adenovirus-specific T cells in peripheral blood of all individuals sampled and about 20% of samples from the gut, suggesting a potential role of T cells in better controlling virus replication in the gut. The overall structure of the E3 locus, which is involved in modulating the host''s response to infection, is degenerate in humans compared to that in apes, which may contribute to diminished evasion of host immunity. The impact of adenovirus persistence and immune responses should be considered when using adenoviral vectors in gene therapy and genetic vaccines.Viruses of the Adenoviridae family infect a wide range of vertebrate hosts. Adenoviruses that infect mammals belong to the genus Mastadenovirus and encompass at least seven viral species (formerly called subtypes) that infect primates (5). The molecular biology of human-derived adenoviruses has been characterized extensively for the species C group, for which human adenovirus 2 (HAdV-2) and HAdV-5 serve as prototypes (6). Adenoviruses cause a variety of nonlethal infectious diseases in humans, and lethal disseminated adenovirus infection occurs in immunosuppressed patients (6). Attempts to evaluate the pathogenesis of human adenoviruses in animal models have been difficult since most models demonstrate a very narrow permissiveness for virus replication.The natural history of adenovirus infections in humans was initially evaluated in prospective surveillance studies of family cohorts (7, 8). Self-limited respiratory illnesses in children were the most common syndromes associated with adenovirus infection, although virus was most easily detected in the stool. Excretion of virus in stool usually wanes rapidly following resolution of the infectious syndrome but is prolonged for a subset of individuals. Species C adenoviruses, which are the most prevalent in humans, can establish latency in adenoid and tonsil-derived lymphocytes (9).Adenovirus vectors have been used successfully as vaccine carriers due to their ability to elicit potent cellular and humoral immune response to the encoded transgene product. Recombinant vectors based on HAdV-5 have emerged as a potent platform for activating cytotoxic T lymphocytes against tumor and viral antigens. A problematic response of the host to HAdV-5-based vectors that was not predicted based on animal testing was observed in a clinical trial, namely, there was a paradoxical increased susceptibility to infection with human immunodeficiency virus (HIV) following vaccination with an HIV-based HAdV-5 vector in subjects with evidence of prior exposure to a natural infection with HAdV-5 (2).