Co-circulation of Peste-des-Petits-Ruminants Virus Asian lineage IV with Lineage II in Nigeria

Peste-des-petits-ruminants (PPR), a major small ruminant transboundary animal disease, is endemic in Nigeria. Strains of the causal agent, peste-des-petits-ruminants virus (PPRV), have been differentiated into four genetically distinct lineages based on the partial sequence of the virus nucleoprotein (N) or fusion (F) genes. Peste-des-petits-ruminants virus strains that were identified initially in Africa were grouped into lineages I, II and III and viruses from Asia were classified as lineage IV and referred to as the Asian lineage. Many recent reports indicate that the Asian lineage is now also present in Africa. With this in mind, this study was conducted to reassess the epidemiology of PPRV in Nigeria. A total of 140 clinical samples from 16 sheep and 63 goats with symptoms suggestive of PPR were collected from different states of Nigeria during a four-year period (2010-2013). They were analysed by the amplification of fragments of the N gene. Results for 33 (42%) animals were positive. The phylogenetic analysis of the N gene sequences with those available in GenBank showed that viruses that were detected belong to both lineage II and IV. Based on an analysis of the N gene sequences, the lineage IV isolates grouped into two clades, one being predominant in the north-eastern part of the country and the other found primarily in the southern regions of the country. This study reports the presence of PPRV Asian lineage IV in Nigeria for the first time.

Detection and Genome Analysis of a Lineage III Peste Des Petits Ruminants Virus in Kenya in 2011

In May 2011 in Turkana County, north-western Kenya, tissue samples were collected from goats suspected of having died of peste des petits ruminant (PPR) disease, an acute viral disease of small ruminants. The samples were processed and tested by reverse transcriptase PCR for the presence of PPR viral RNA. The positive samples were sequenced and identified as belonging to peste des petits ruminants virus (PPRV) lineage III. Full-genome analysis of one of the positive samples revealed that the virus causing disease in Kenya in 2011 was 95.7% identical to the full genome of a virus isolated in Uganda in 2012 and that a segment of the viral fusion gene was 100% identical to that of a virus circulating in Tanzania in 2013. These data strongly indicate transboundary movement of lineage III viruses between Eastern Africa countries and have significant implications for surveillance and control of this important disease as it moves southwards in Africa.

Full genome sequence of a peste des petits ruminants virus (PPRV) from Ghana

The full genome of a peste des petits ruminants virus (PPRV) isolated from a sheep lung sample collected in Ghana, Western Africa, in 2010, has been sequenced. Phylogenetic analysis demonstrated that the virus clustered within the lineage II clade while comparison of its full genome with those of other PPRV strains revealed the highest identity (96.6 %) at a nucleotide level with the PPRV strain Nigeria/76/1. This is the first full genome sequence generated for a PPRV lineage II isolated since 1976.

Phylogenetic analysis of rabies viruses from Burkina Faso, 2007

Genetic characterization of 32 canine rabies viruses circulating in Burkina Faso in 2007 identified two clades both belonging to the Africa 2 lineage. Sequence homology data suggest that transboundary spread is the most likely means of introduction, highlighting an evolving epidemiological situation.

Neutrophil-activating protein (HP-NAP) versus ferritin (Pfr): comparison of synthesis in Helicobacter pylori

We recently reported that the neutrophil-activating protein (HP-NAP) of Helicobacter pylori is capable of binding iron in vitro. To more fully understand the relationship between iron and HP-NAP the synthesis of HP-NAP was compared to that of Pfr, another iron-binding protein of H. pylori. Synthesis of HP-NAP and Pfr in growing cultures of H. pylori was analysed under iron depletion and iron, copper, nickel and zinc overload. The synthesis of HP-NAP and Pfr in H. pylori was also analysed under conditions of varying pH and oxidative stress. In addition, recombinant HP-NAP and Pfr were produced in Escherichia coli to assess the contribution of the two proteins to increased survival of E. coli under heavy metal overload. Our data reveal that both HP-NAP and Pfr accumulate in the stationary phase of growth. HP-NAP synthesis is not regulated by iron depletion or overload or by the presence of copper, nickel or zinc in liquid medium and it does not confer resistance to these metals when produced in E. coli. Except for an increase in the synthesis of Pfr at pH 5.7 neither the pH or oxidative stress conditions investigated had an affect on the synthesis of either protein. An increase in Pfr synthesis was observed under iron overload and a decrease was observed under conditions of copper, nickel and zinc overload confirming previous reports. Recombinant Pfr, as well as conferring resistance to iron and copper as previously reported, also conferred resistance to zinc overload when produced in E. coli.

Virulence factors of Helicobacter pylori

To date a number of virulence factors have been identified and characterised from the gastric pathogen Helicobacter pylori. The vacuolating toxin (VacA) is a major determinant of H. pylori-associated gastric disease. In non-polarised cells, VacA alters the endocytic pathway, resulting in the release of acid hydrolases and the reduction of both extracellular ligand degradation and antigen processing. The toxin forms trans-membrane anion-specific channels and reduces the transepithelial electrical resistance of polarized monolayers. Localization of the VacA channels in acidic intracellular compartments causes osmotic swelling which, together with membrane fusion, leads to vacuole formation. The neutrophil-activating protein of H. pylori (HP-NAP) induces the production of oxygen radicals in human neutrophils via a cascade of intracellular activation events which may contribute to the damage of the stomach mucosa. This protein has recently been shown to be an important antigen in the human immune response to H. pylori infection. In addition, mice vaccinated with recombinant HP-NAP were protected against H. pylori challenge. H. pylori strains that are associated with severe tissue damage and inflammation possess the cag pathogenicity island that contains several genes encoding factors involved in the induction of proinflammatory cytokines/chemokines and of a type IV secretion system involved in the delivery of a highly immunogenic protein, CagA, into eukaryotic cells. Recent advances in our understanding of the involvement of VacA, HP-NAP and the CagA/Type IV secretion system in the H. pylori-associated disease process are discussed in this review.

Helicobacter pylori neutrophil-activating protein stimulates tissue factor and plasminogen activator inhibitor-2 production by human blood mononuclear cells

Helicobacter pylori neutrophil-activating protein (HP-NAP) is a virulence factor that activates phagocytic NADPH-oxidase. The effect of HP-NAP on the production of tissue factor (TF), plasminogen activator inhibitor-2 (PAI-2), and urokinase-type plasminogen activator (u-PA) by human blood mononuclear cells (MNC) was evaluated by using functional and immunological assays and mRNA analysis. HP-NAP induced time- and dose-dependent increases in TF and PAI-2, with a maximal effect at 300 nmol/L (>15-fold increase in antigens). No changes in u-PA were observed. When whole bacteria were used, an H. pylori mutant lacking HP-NAP was significantly less active than the wild-type strain. MNC from a patient with chronic granulomatous disease behaved as do normal cells, which indicates that HP-NAP effects can occur independently of NADPH-oxidase. HP-NAP, by inducing the coordinate expression of cell procoagulant and antifibrinolytic activities, might favor fibrin deposition and contribute to the inflammatory reaction of gastric mucosa elicited by H. pylori.

Virulence factors of Helicobacter pylori

To date a number of virulence factors have been identified and characterised from the gastric pathogen Helicobacter pylori. The vacuolating toxin (VacA) is a major determinant of H. pylori-associated gastric disease. In non-polarised cells, VacA alters the endocytic pathway, resulting in the release of acid hydrolases and the reduction of both extracellular ligand degradation and antigen processing. The toxin forms trans-membrane anion-specific channels and reduces the transepithelial electrical resistance of polarized monolayers. Localization of the VacA channels in acidic intracellular compartments causes osmotic swelling which, together with membrane fusion, leads to vacuole formation. The neutrophil-activating protein of H. pylori (HP-NAP) induces the production of oxygen radicals in human neutrophils via a cascade of intracellular activation events which may contribute to the damage of the stomach mucosa. This protein has recently been shown to be an important antigen in the human immune response to H. pylori infection. In addition, mice vaccinated with recombinant HP-NAP were protected against H. pylori challenge. H. pylori strains that are associated with severe tissue damage and inflammation possess the cag pathogenicity island that contains several genes encoding factors involved in the induction of proinflammatory cytokines/chemokines and of a type IV secretion system involved in the delivery of a highly immunogenic protein, CagA, into eukaryotic cells. Recent advances in our understanding of the involvement of VacA, HP-NAP and the CagA/Type IV secretion system in the H. pylori-associated disease process are discussed in this review.

Population characteristics of Irish Helicobacter pylori isolates: a tRNA-associated locus

BACKGROUND

A strain-variable transfer RNA-associated-locus (trl) was present in 50% of Irish Helicobacter pylori (H. pylori), isolates and did not correlate with the origin of the isolates.

AIM

To associate a particular genotype or phenotype to trl status in H. pylori by further screening the isolates from the original study for the presence of known genotypic and phenotypic characteristics.

METHODS

Forty two clinical isolates were screened for the presence of the cagA, vacA, iceA1 and vapD genes by Southern or DNA dot blot analysis. Western blot analysis was performed using antibodies to CagA, VacA, Lewis X (Le(x)) and Lewis Y (Le(y)). Plasmids were identified by the alkaline lysis method.

RESULTS

The cagA gene was present in 29 (69%) of isolates screened and 21 (50%) produced the CagA protein. The vacA gene was detected in all of the isolates while VacA was expressed in 71.4%. The iceA1 and vapD loci were detected in 73.8% and 71.4% respectively. Le(x) was expressed in 42.9% and Le(y) in 38.1% of the isolates. Expression of both Lewis antigens was detected in 7.1% while in 30.9% neither antigen was detected. Plasmids were present in 47.6%. There was no association between the trl status of isolates and any of the above. There were no significant associations between the phenotypic and genotypic characteristics studied and peptic ulcer disease or non-ulcer dyspepsia.

CONCLUSION

The strain-variable tRNA-associated locus is independent of the vacA/VacA, cagA/CagA, Lewis X, Lewis Y, iceA1, vapD and plasmid status in the population of Irish H. pylori isolates studied.

The Helicobacter pylori neutrophil-activating protein is an iron-binding protein with dodecameric structure

The neutrophil-activating protein (HP-NAP) of Helicobacter pylori is a major 17 kDa antigen of the immune response of infected individuals. Amino acid sequence comparison indicated a high similarity between HP-NAP and both bacterial DNA-protecting proteins (Dps) and ferritins. The structure prediction and spectroscopic analysis presented here indicate a close similarity between HP-NAP and Dps. Electron microscopy revealed that HP-NAP forms hexagonal rings of 9-10 nm diameter with a hollow central core as seen in Dps proteins, clearly different from the 12 nm icositetrameric (24 subunits) ferritins. However, HP-NAP is resistant to thermal and chemical denaturation similar to the ferritin family of proteins. In addition, HP-NAP binds up to 40 atoms of iron per monomer and does not bind DNA. We therefore conclude that HP-NAP is an unusual, small, ferritin that folds into a four-helix bundle that oligomerizes into dodecamers with a central hole capable of binding up to 500 iron atoms per oligomer.