High-Resolution Functional Profiling of the Norovirus Genome

Human noroviruses (HuNoV) are a major cause of nonbacterial gastroenteritis worldwide, yet details of the life cycle and replication of HuNoV are relatively unknown due to the lack of an efficient cell culture system. Studies with murine norovirus (MNV), which can be propagated in permissive cells, have begun to probe different aspects of the norovirus life cycle; however, our understanding of the specific functions of the viral proteins lags far behind that of other RNA viruses. Genome-wide functional profiling by insertional mutagenesis can reveal protein domains essential for replication and can lead to generation of tagged viruses, which has not yet been achieved for noroviruses. Here, transposon-mediated insertional mutagenesis was used to create 5 libraries of mutagenized MNV infectious clones, each containing a 15-nucleotide sequence randomly inserted within a defined region of the genome. Infectious virus was recovered from each library and was subsequently passaged in cell culture to determine the effect of each insertion by insertion-specific fluorescent PCR profiling. Genome-wide profiling of over 2,000 insertions revealed essential protein domains and confirmed known functional motifs. As validation, several insertion sites were introduced into a wild-type clone, successfully allowing the recovery of infectious virus. Screening of a number of reporter proteins and epitope tags led to the generation of the first infectious epitope-tagged noroviruses carrying the FLAG epitope tag in either NS4 or VP2. Subsequent work confirmed that epitope-tagged fully infectious noroviruses may be of use in the dissection of the molecular interactions that occur within the viral replication complex.     

Comparative effects of various classes of mouse interferons on macrophage activation for tumor cell killing

The effects of mouse interferon-alpha (MuIFN-alpha), -beta (MuIFN-beta), and -gamma (MuIFN-gamma) on macrophage activation for tumor cell killing were determined by using proteose peptone-elicited peritoneal macrophages from C3H/HeN and C3H/HeJ mice under conditions that either included or were free of detectable endotoxin. Alone, under the conditions used, none of the interferons was able to activate macrophages directly for tumor cell killing. However, with a second signal provided to responsive macrophages by contaminating endotoxin, added bacterial lipopolysaccharide (LPS), or heat-killed Listeria monocytogenes (HKLM), all three types of interferon induced cytolytic activity, with MuIFN-gamma approximately 500 to 1000-fold more active than either MuIFN-alpha or -beta. Thus, all three interferons were able to prime macrophages for killing but required a second signal before cytolytic activity could be expressed. When MuIFN-gamma was mixed with either MuIFN-alpha or -beta and placed on macrophages, little or no killing developed. Mixtures of MuIFN-gamma with either MuIFN-alpha or -beta did increase the sensitivity of macrophages to triggering by LPS, however, compared with macrophages treated with MuIFN-gamma alone. The results are collectively important because they i) confirm that significant quantitative differences exist between the various interferons with regard to their capacity to prime macrophages for tumor cell killing; ii) indicate that to be an efficient activator each type of interferon must be combined with a second stimulus, such as LPS or HKLM; iii) show that neither MuIFN-alpha nor -beta can provide an efficient second triggering signal for macrophages that are primed by MuIFN-gamma; and iv) document that mixtures of MuIFN-gamma with either MuIFN-alpha or -beta are most efficient at inducing priming, compared with any one of the interferons used alone.     

Genes for serum amyloid A proteins map to Chromosome 7 in the mouse

Summary Several restriction fragment length variants have been detected among inbred strains using a mouse serum amyloid A cDNA clone. Five variants were shown to segregate as a single genetic unit and were mapped to Chromosome 7 between the glucose phosphate isomerase locus (Gpi-1) and the pink eye dilution locus (p) using recombinant inbred and congenic strains. The finding that no major MspI or BclI restriction fragments were shared between digests of DNAs from a Chromosome 7 congenic strain and its inbred partner, indicate that most, and probably all, sequences detected with the probe are clustered on Chromosome 7. Aneuploid mapping was used to show that the serum amyloid A gene complex (Saa) is proximal to the Chromosome 7 breakpoint in T(7;X)1Ct, a translocation in which the middle third of Chromosome 7 is inserted into the X-chromosome. A survey of inbred strains revealed a single common Saa haplotype and eight rare haplotypes. The complex distribution of 14 different variants suggests that recombination may have played a role in haplotype evolution.This work was supported by grants GM18684 and CA33093 from the National Institute of General Medical Sciences and the National Cancer Institute, respectively.     

Paleomicrobiology: Revealing Fecal Microbiomes of Ancient Indigenous Cultures

Coprolites are fossilized feces that can be used to provide information on the composition of the intestinal microbiota and, as we show, possibly on diet. We analyzed human coprolites from the Huecoid and Saladoid cultures from a settlement on Vieques Island, Puerto Rico. While more is known about the Saladoid culture, it is believed that both societies co-existed on this island approximately from 5 to 1170 AD. By extracting DNA from the coprolites, followed by metagenomic characterization, we show that both cultures can be distinguished from each other on the basis of their bacterial and fungal gut microbiomes. In addition, we show that parasite loads were heavy and also culturally distinct. Huecoid coprolites were characterized by maize and Basidiomycetes sequences, suggesting that these were important components of their diet. Saladoid coprolite samples harbored sequences associated with fish parasites, suggesting that raw fish was a substantial component of their diet. The present study shows that ancient DNA is not entirely degraded in humid, tropical environments, and that dietary and/or host genetic differences in ancient populations may be reflected in the composition of their gut microbiome. This further supports the hypothesis that the two ancient cultures studied were distinct, and that they retained distinct technological/cultural differences during an extended period of close proximity and peaceful co-existence. The two populations seemed to form the later-day Taínos, the Amerindians present at the point of Columbian contact. Importantly, our data suggest that paleomicrobiomics can be a powerful tool to assess cultural differences between ancient populations.     

Interactions of ovalbumin and of its putative signal sequence with phospholipid monolayers. Possible importance of differing lateral stabilities in protein translocation.

Surface properties of ovalbumin and of its putative signal sequence, and their interactions with phospholipids at an air-water interface, have been studied. The mature protein can form an interfacial film spontaneously from its bulk solution, whereas the signal sequence cannot. Mature ovalbumin also penetrates phospholipid monolayers from the subphase (independently of the type of phospholipid present), whereas its signal sequence does not. The surface stability of a spread film of the signal sequence is, however, higher than that of a film of mature ovalbumin. Above specific threshold concentrations of signal peptide and of mature ovalbumin in mixed films with phospholipids, two separate phases are formed. In such immiscible films, the signal sequence peptide is also able to support a higher lateral surface pressure than mature ovalbumin, at corresponding areas of peptide and mature protein in the mixed monolayers. It is suggested that the differing lateral stabilities of ovalbumin and of its putative signal sequence may be relevant to the translocation of ovalbumin across the membrane of the endoplasmic reticulum, and a scheme for its translocation is proposed that is based on these properties.     

Nucleotide sequence analysis of tetracycline resistance gene tetO from Streptococcus mutans DL5.

Streptococcus mutans DL5, isolated from the dental plaque of a pig, was resistant to high levels of streptomycin (Sm, 20 mg/ml), erythromycin (Em, 1 mg/ml), and tetracycline (Tc, greater than 100 micrograms/ml), but contained no detectable plasmid DNA. The Smr and Emr determinants were cloned from cellular DNA on the self-replicating 5-kilobase-pair (kbp) EcoRI fragment of pAM beta 1 and the 4.2-kbp cryptic plasmid pVA380-1, respectively, by transformation of Streptococcus sanguis Challis. Helper plasmid cloning, with a Challis host containing pVA380-1, was required to clone the Tcr determinant of strain DL5 on this vector. A single-colony isolate of the original Tcr clone contained a hybrid plasmid, pDL421, composed of 2.6 kbp of vector DNA and 11.4 kbp of S. mutans DNA. Plasmid pDL421 did not hybridize to plasmids containing the streptococcal Tcr determinants tetL, tetM, and tetN. A shortened derivative of this hybrid plasmid, pDL422, missing a 4.9-kbp HincII fragment from the S. mutans DNA but still encoding Tcr, was obtained by subcloning in S. sanguis Challis. The Tcr gene was located in a 1,917-base-pair open reading frame (ORF) corresponding to a 72-kilodalton protein. The ORF exhibited 99.4% sequence identity with the 1,917-base-pair tetO gene from a strain of Campylobacter coli (W. Sougakoff, B. Papadopoulou, P. Nordmann, and P. Courvalin, FEMS Microbiol. Lett. 44:153-160, 1987). A 1.67-kbp NdeI fragment, internal to the ORF from strain DL5, as well as pDL421 hybridized under stringent conditions to DNA from 10 of 10 Tcr strains of C. coli and Campylobacter jejuni from human and animal sources, but not to DNA from Tcs isolates of these two species.     

马立克氏病毒单克隆抗体的研究

获得了4株分泌马立克氏病毒(MDV)特异性单克隆抗体(McAb)的杂交瘤细胞:4BS10对MDV所有毒株呈阳性反应;4CN8 对MDV血清1,3型毒株发生反应;2BN90和4CN24只对MDV血清1型毒株有阳性反应。3个McAb属IgG1,1个为IgG2b,均不中和MDV,免疫扩散试验也无沉淀线。对禽白血病毒(ALV)无交叉反应。 以2BN90和辣根过氧化物酶、异硫氰酸荧光素的结合物进行直接酶联免疫吸附试验和直接荧光抗体试验,均获得成功。抗体滴度前者为1/51,200,后者为1/640。对ALV无交叉反应。