Host-parasite interactions in rodent nematode infections

In rodents, Trichinella spiralis and Nippostrongylus brasiliensis infect the small intestine and Trichuris muris resides in the colon. The intestinal host response in these animals is characterized by changes in mucosal architecture and inflammation and is associated with worm expulsion. The requirement of T cell-mediated host response in worm expulsion has been demonstrated over many years. Subsequent studies have shown that Th2-type, but not Th1-type, responses mediate resistance to the nematodes. Investigations using neutralizing antibodies and genetically manipulated mice have characterized the contribution of individual Th2-type cytokines in not only worm expulsion, but also specific cellular changes that occur in the mucosa, such as alterations in epithelial phenotype and smooth muscle. There is also increasing appreciation of the contribution of non-bone marrow-derived cells in innate and adaptive host responses in these models.     

细菌毒素-抗毒素系统在噬菌体流产感染中的作用北大核心CSCD

细菌常受到数量众多的噬菌体感染,宿主细菌在和噬菌体竞赛中进化出多样化的分子策略,流产感染(abortive infection,Abi)是其中之一。毒素-抗毒素系统(toxin-antitoxin system,TA)会在细菌受到压力胁迫时表达并介导细菌的低代谢甚至休眠,还能直接减少子代噬菌体形成。此外,部分毒素序列和结构与Cas蛋白高度同源,噬菌体甚至会编码抗毒素类似物来阻遏对应毒素的活性。这表明流产感染中细菌死亡过程导致的噬菌体感染失败与TA功能高度重合,TA可能是噬菌体侵染宿主的主要阻力和防御力量之一。文中基于TA系统的分类和功能,对参与噬菌体流产感染的TA系统进行了综述,并预测具有流产功能的TA系统和其在抗生素开发和疾病治疗中的应用前景。这有助于认识细菌-噬菌体相互作用,并指导噬菌体治疗和合成生物学。     

PROSITE: recent developments.

PROSITE is a compilation of sites and patterns found in protein sequences; it can be used as a method of determining the function of uncharacterized proteins translated from genomic or cDNA sequences.     

Some recent developments in the molecular epidemiology of Epstein-Barr virus infections

We have applied two different recombinant DNA techniques to the study of the epidemiology of Epstein-Barr virus infections. In the first application, cloned subfragments of viral DNA were used as probes to detect EBV DNA in a variety of lymphoproliferative disorders and in lymphoid cell lines. Patients who are epidemiologically unrelated harbor EBV genotypes which can readily be distinguished from each other. Patients who are epidemiologically related (such as mothers and infants) have similar EBV genotypes. Some patients, especially those who are immunocompromised, are infected with two distinct genotypes. In the second application, we have examined the immune response to specific EBV antigens expressed from small cloned viral DNA subfragments. We have identified a group of patients with presumed chronic EBV infection who selectively fail to recognize one subcomponent of the EB nuclear antigen complex.     

Host-parasite interactions in Staphylococcus aureus keratitis

Ulcerative keratitis is among the leading ocular bacterial infections, and Streptococcus aureus accounts for approximately 25% of cases in some surveys. Although S. aureus expresses numerous virulence factors, many of which are under the control of staphylococcal global regulatory genes, their pathophysiologic roles in keratitis are largely unknown. Similarly, the nature of the host response during S. aureus keratitis is unclear. Following a review of previously published research on the pathophysiology of S. aureus ocular infection, we present the results of a study designed to assess the host-parasite relationship between S. aureus and human corneal epithelial cells (HCECs) in vitro. In this model system, a wild-type S. aureus strain and its isogenic mutants harboring mutations in agr and sar global regulatory genes or fibronectin-binding proteins A and B (fnbAB) were tested for their ability to bind and invade confluent HCEC monolayers. The contribution of host cell factors was assessed by preincubating HCECs with various inhibitory agents. These studies demonstrated that S. aureus not only adhered to the surface of HCECs but was also internalized, as has been previously observed in other nonocular cell lines. Adherence and invasion of HCECs was saturable at 1 h of incubation in the presence of approximately 10(7) CFU per HCEC monolayer (multiplicity of infection approximately 10). A mutant defective in both agr and sar global regulators was not significantly different in invasive capacity compared to its isogenic wild-type parent strain. In contrast, mutations in fibronectin-binding proteins A and B (fnbAB) reduced the invasiveness of S. aureus by 99% compared to the wild-type strain. Pretreatment of HCECs with colchicine had little effect on S. aureus invasion. In sharp contrast, cytochalasin D and genistein were each capable of inhibiting invasion by >99%. In summary, the results of this study point to fibronectin-binding protein as a key S. aureus surface adhesin facilitating invasion of HCECs in vitro. Furthermore, these results suggest an active mechanism for S. aureus internalization by HCECs, likely involving actin polymerization and tyrosine kinase activity. Additional studies are warranted to determine the applicability of these findings in vivo, and to facilitate the rational design of therapeutic agents aimed at blocking the establishment and progression of S. aureus keratitis.     

Host-parasite interactions: an interview with Emily Troemel

Emily Troemel is a Professor at the University of California San Diego, where her lab uses Caenorhabditis elegans to study host–pathogen interactions and the shaping of the immune response. In this interview, Emily shared her thoughts on peer review and its role in training future scientists, and the possibility of a new form of immunity in epithelia.     

Host-parasite interactions and the evolution of gene expression

Interactions between hosts and parasites provide an ongoing source of selection that promotes the evolution of a variety of features in the interacting species. Here, we use a genetically explicit mathematical model to explore how patterns of gene expression evolve at genetic loci responsible for host resistance and parasite infection. Our results reveal the striking yet intuitive conclusion that gene expression should evolve along very different trajectories in the two interacting species. Specifically, host resistance loci should frequently evolve to co-express alleles, whereas parasite infection loci should evolve to express only a single allele. This result arises because hosts that co-express resistance alleles are able to recognize and clear a greater diversity of parasite genotypes. By the same token, parasites that co-express antigen or elicitor alleles are more likely to be recognized and cleared by the host, and this favours the expression of only a single allele. Our model provides testable predictions that can help interpret accumulating data on expression levels for genes relevant to host-parasite interactions.     

Bacterial endophytes: recent developments and applications.

Endophytic bacteria have been found in virtually every plant studied, where they colonize the internal tissues of their host plant and can form a range of different relationships including symbiotic, mutualistic, commensalistic and trophobiotic. Most endophytes appear to originate from the rhizosphere or phyllosphere; however, some may be transmitted through the seed. Endophytic bacteria can promote plant growth and yield and can act as biocontrol agents. Endophytes can also be beneficial to their host by producing a range of natural products that could be harnessed for potential use in medicine, agriculture or industry. In addition, it has been shown that they have the potential to remove soil contaminants by enhancing phytoremediation and may play a role in soil fertility through phosphate solubilization and nitrogen fixation. There is increasing interest in developing the potential biotechnological applications of endophytes for improving phytoremediation and the sustainable production of nonfood crops for biomass and biofuel production.     

Plant signalling peptides: some recent developments.

The subject of this review is plant signalling peptides, peptides of a new generation which regulate growth, differentiation, and other plant physiological functions. These peptides include systemin, the phytosulfokines (PSKs), ENOD40, CLAVATA3, Locus-S, POLARIS, IDA, and ROT4. On the basis of literature data and our own results we discuss their structure, biological properties, and structure/biological function relationship, especially for the more studied systemin and PSK-alpha.     

Nanovaccines: recent developments in vaccination

In the past 100 years, vaccination has contributed immensely to public health by preventing a number of infectious diseases. Attenuated, killed or part of the microorganism is employed to stimulate the immune system against it. Progress in biotechnology has provided protective immunity through DNA vaccines. In recent years, nanovaccine is a novel approach to the methodology of vaccination. Nanomaterials are delivered in the form of microspheres, nanobeads or micro-nanoprojections. Painless, effective and safe needle-free routes such as the intranasal or the oral route, or patches of microprojections to the skin are some of the approaches which are in the experimental stage at present but may have a great future ahead in nanovaccination.     

Auxin receptors: recent developments

Rapid advances have been made in the study of auxin binding proteins (ABPs) in the last five years. In particular, an ABP in maize membranes has been cloned, sequenced and both monoclonal and polyclonal antibodies to this ABP have been developed. Structural and functional analysis has begun and there is good electrophysiological evidence that ABP in the plasma membrane functions as a receptor, probably involved in auxin-induced cell expansion. The role of the large amount of ABP in the endoplasmic reticulum is less clear, as is the relationship to soluble ABPs. At present there is only some circumstantial evidence relating any ABP to cell division. Receptors for synthetic inhibitors of auxin transport (phytotropins) are also of interest in relation to auxin action, but are less well characterised. Identification of new naturally-occurring phytotropins could lead to novel plant growth regulators.     

Single- vs. multiple-set resistance training: recent developments in the controversy

The number of sets in a resistance training program remains a major point of discussion and controversy. Studies prior to 1998 demonstrated inconsistent findings between single-set and multiple-set programs; however, recent evidence suggests that multiple sets promote additional benefits following short- and long-term training. The rationale supporting multiple sets is that the number of sets is part of the exercise volume equation, and the volume of exercise is crucial in producing the stimulus necessary to elicit specific physiological adaptations. The purpose of this paper is to present an overview of recent resistance training studies comparing single and multiple sets. However, it should be noted that studies to date have been conducted in young and middle-aged adults, and it remains to be determined if the additional benefits accrued with multiple-set training also occurs for older adults, especially the frail elderly.