Vaccination against Streptococcus pneumoniae using truncated derivatives of polyhistidine triad protein D

Polyhistidine triad protein D (PhtD) has been described as a promising vaccine candidate for use against Streptococcus pneumoniae, but there has been a lack of examination of its structure and of which region(s) of the protein are targeted by protective immune responses. In this study, we purified recombinant truncated derivatives of PhtD and examined their secondary structural composition, as well as their capacity to bind antibodies from polyclonal murine serum generated against the full length protein. This allowed the identification of a particularly immunogenic fragment of PhtD, which was also purified and characterised. The truncated derivatives were tested as vaccine antigens in mouse models of pneumococcal sepsis and colonisation, using alum and E. coli heat labile toxin B subunit respectively as adjuvants. These experiments revealed that whilst the immunogenic region identified may be a promising candidate to protect against sepsis, the full length PhtD was ineffective at conferring significant protective immunity. These results are significant for the potential for PhtD to be used in novel vaccines, which are currently being tested in clinical trials.Charles D. Plumptre, Abiodun D. Ogunniyi, James C. Pato

Overlapping functionality of the Pht proteins in zinc homeostasis of streptococcus pneumoniae

Streptococcus pneumoniae is a globally significant pathogen that causes a range of diseases, including pneumonia, sepsis, meningitis, and otitis media. Its ability to cause disease depends upon the acquisition of nutrients from its environment, including transition metal ions such as zinc. The pneumococcus employs a number of surface proteins to achieve this, among which are four highly similar polyhistidine triad (Pht) proteins. It has previously been established that these proteins collectively aid in the delivery of zinc to the ABC transporter substrate-binding protein AdcAII. Here we have investigated the contribution of each individual Pht protein to pneumococcal zinc homeostasis by analyzing mutant strains expressing only one of the four pht genes. Under conditions of low zinc availability, each of these mutants showed superior growth and zinc accumulation profiles relative to a mutant strain lacking all four genes, indicating that any of the four Pht proteins are able to facilitate delivery of zinc to AdcAII. However, optimal growth and zinc accumulation in vitro and pneumococcal survival and proliferation in vivo required production of all four Pht proteins, indicating that, despite their overlapping functionality, the proteins are not dispensable without incurring a fitness cost. We also show that surface-attached forms of the Pht proteins are required for zinc recruitment and that they do not contribute to defense against extracellular zinc stress

The first histidine triad motif of phtd is critical for zinc homeostasis in Streptococcus pneumoniae

Streptococcus pneumoniae is the world's foremost human pathogen. Acquisition of the first row transition metal ion zinc is essential for pneumococcal colonization and disease. Zinc is acquired via the ATP-binding cassette transporter AdcCB and two zinc-binding proteins, AdcA and AdcAII. We have previously shown that AdcAII is reliant upon the polyhistidine triad (Pht) proteins to aid in zinc recruitment. Pht proteins generally contain five histidine (His) triad motifs that are believed to facilitate zinc binding and therefore play a significant role in pneumococcal metal ion homeostasis. However, the importance and potential redundancy of these motifs have not been addressed. We examined the effects of mutating each of the five His triad motifs of PhtD. The combination of in vitro growth assays, active zinc uptake, and PhtD expression studies show that the His triad closest to the protein's amino terminus is the most important for zinc acquisition. Intriguingly, in vivo competitive infection studies investigating the amino- and carboxyl-terminal His triad mutants indicate that the motifs have similar importance in colonization. Collectively, our new insights into the contributions of the individual His triad motifs of PhtD, and by extension the other Pht proteins, highlight the crucial role of the first His triad site in zinc acquisition. This study also suggests that the Pht proteins likely play a role beyond zinc acquisition in pneumococcal virulence

Protected apes, unprotected forest: composition, structure and diversity of riverine forest fragments and their conservation value in Uganda

Small forest fragments are common in anthropogenic landscapes in the tropics. These have conservation value if they provide habitat for threatened wildlife and maintain connectivity between larger habitats. Riverine forests have particular ‘corridor’ potential due to their linear shape, but are under-studied in many regions. We surveyed trees in riverine fragments in Bulindi, an anthropogenic landscape 25 km south of the Budongo Forest in western Uganda, to determine their condition and assess their value for wildlife, particularly endangered chimpanzees Pan troglodytes. We assessed tree composition, structure and diversity and compared results with a previous survey made in Budongo, the nearest main forest block. Riverine fragments were considerably less species-dense and species-rich than Budongo. Community composition differed markedly between sites and there was virtually no overlap in common species. Common trees in fragments were characteristic of East African swamp and groundwater forests (e.g. the palm Phoenix reclinata) and the dominant tree family was the Moraceae, members of which produce fleshy fruits attractive to frugivores (e.g. figs). Important fruit foods for chimpanzees differed between habitats. While basal area of important fruit trees was comparable, overall density was greater in fragments. Our data suggest the riverine fragments offer a relatively food-dense habitat for chimpanzees and other frugivores. Small riverine forests have little or no protection regionally and are being extensively logged and cleared for agriculture. Species logged for timber in Bulindi included important chimpanzee fruit trees. Unless conservation projects successfully reverse current trends, the value of the riverine corridors for maintaining connectivity between main forest blocks is limited

Pan troglodytes (errata version published in 2018)

Assessment Information: Although Pan troglodytes is the most abundant and widespread of the great apes, and many populations exist in protected areas, the declines that have occurred are expected to continue, satisfying the criteria for an Endangered listing (Oates 2006). Due to high levels of poaching, infectious diseases, and loss of habitat and habitat quality caused by expanding human activities, this species is estimated to have experienced a significant population reduction in the past 20–30 years and it is suspected that this reduction will continue for the next 30–40 years. Due to their slow life history and a generation time estimated to be 25 years, Chimpanzee populations cannot sustain high levels of mortality, whether disease-induced or caused by poaching. The maximum population reduction over a three-generation (75 year) period from 1975 to 2050 is suspected to exceed 50%, hence qualifying this taxon as Endangered under criterion A. Although conservation efforts directed at Chimpanzees and other wildlife have increased significantly in recent years, the assumption that population reductions will continue is a precautionary approach based on the rapid growth of human populations in sub-Saharan Africa, continuing poaching for bushmeat, the commercial bushmeat trade, the arrival of industrial agriculture (which requires clearcutting of forest), corruption and lack of law enforcement, lack of capacity and resources, and political instability in some range states. At the same time, zoonosis and disease outbreaks present significant risks; there is, for example, evidence that Ebolavirus will continue to spreadin some parts of the Chimpanzee's geographic range(Walshet al.2005)