Evidence for Archaean lamprophyre from the Kaapvaal Craton, South Africa

A suite of mafic dykes occurs as a late component in a wellcharacterized trondhjemite–tonalite–diorite–granodiorite assemblage in the Johannesburg Dome of the central Kaapvaal Craton, southern Africa. The dykes have been subdivided into two sets, based on their orientation, and major and trace element geochemistry. Set 1 dykes are characterized by elevated SiO2, Al2O3 and TiO2, and particularly by enriched LILE and HSFE (e.g. Zr > 200 ppm, Nb > 20 ppm, Ba > 300 ppm), higher than in any of the accompanying felsic rocks. REE and trace element values for Set 1 dykes are similar to those for calc-alkaline lamprophyres. The Set 2 dykes have similar trace element distributions, but are significantly less enriched in general, and are broadly tholeiitic in composition, with enriched MgO (>11 wt. percentage) indicative of an olivine–phyric tholeiitic basaltic protolith. Field relationships and available U–Pb zircon geochronology indicate that the dykes are contemporaneous with components of the trondhjemitic host rocks, and with late granodiorites. The geochemical, geochronological and field petrological setting indicates partial melting of basaltic and eclogitic lithosphere at c. 3120 Myr ago in the basal Kaapvaal Craton, and subsequent emplacement into pre-existing c. 3430 Myr tonalitic to dioritic crust

Evidence for Archaean lamprophyre from the Kaapvaal Craton, South Africa

A suite of mafic dykes occurs as a late component in a wellcharacterized trondhjemite–tonalite–diorite–granodiorite assemblage in the Johannesburg Dome of the central Kaapvaal Craton, southern Africa. The dykes have been subdivided into two sets, based on their orientation, and major and trace element geochemistry. Set 1 dykes are characterized by elevated SiO2, Al2O3 and TiO2, and particularly by enriched LILE and HSFE (e.g. Zr > 200 ppm, Nb > 20 ppm, Ba > 300 ppm), higher than in any of the accompanying felsic rocks. REE and trace element values for Set 1 dykes are similar to those for calc-alkaline lamprophyres. The Set 2 dykes have similar trace element distributions, but are significantly less enriched in general, and are broadly tholeiitic in composition, with enriched MgO (>11 wt. percentage) indicative of an olivine–phyric tholeiitic basaltic protolith. Field relationships and available U–Pb zircon geochronology indicate that the dykes are contemporaneous with components of the trondhjemitic host rocks, and with late granodiorites. The geochemical, geochronological and field petrological setting indicates partial melting of basaltic and eclogitic lithosphere at c. 3120 Myr ago in the basal Kaapvaal Craton, and subsequent emplacement into pre-existing c. 3430 Myr tonalitic to dioritic crust

The Uitkomst intrusion and Nkomati Ni-Cu-Cr-PGE deposit, South Africa: trace element geochemistry, Nd isotopes and high-precision geochronology

The Uitkomst intrusion is a tubular mafic-ultramafic layered body that hosts one of South Africa’s largest Ni-Cu-Cr-PGE deposits, Nkomati. The sulphide ore occurs in the form of massive lenses in the immediate quartzitic footwall and as disseminations within peridotite. The chromite ore forms an up to ∼10-m-thick layer in the lower portion of the intrusion. Uitkomst has generally been interpreted as a magma conduit, possibly related to the Bushveld event. Here, we present a new high-precision U-Pb zircon date of 2057.64 ± 0.69 Ma that overlaps with the age of the Merensky Reef of the Bushveld Complex and thus demonstrates a coeval relationship between the intrusions. Based on incompatible trace elements as well as O- and Nd isotope data (εNd −4.5 to −6.2), we show that the Uitkomst parent magmas were contaminated with up to 20% Archean upper crust prior to emplacement, and with up to 15% dolomitic country rock during emplacement. Ore formation at Nkomati was critically aided by substantial devolatisation and removal of dolomitic floor rocks leading to hydrodynamic concentration of sulphide and chromite during slumping of crystal mushes into the trough-like centre of the subsiding intrusion and its footwall

Novel Vaccines to Human Rabies

Rabies, the most fatal of all infectious diseases, remains a major public health problem in developing countries, claiming the lives of an estimated 55,000 people each year. Most fatal rabies cases, with more than half of them in children, result from dog bites and occur among low-income families in Southeast Asia and Africa. Safe and efficacious vaccines are available to prevent rabies. However, they have to be given repeatedly, three times for pre-exposure vaccination and four to five times for post-exposure prophylaxis (PEP). In cases of severe exposure, a regimen of vaccine combined with a rabies immunoglobulin (RIG) preparation is required. The high incidence of fatal rabies is linked to a lack of knowledge on the appropriate treatment of bite wounds, lack of access to costly PEP, and failure to follow up with repeat immunizations. New, more immunogenic but less costly rabies virus vaccines are needed to reduce the toll of rabies on human lives. A preventative vaccine used for the immunization of children, especially those in high incidence countries, would be expected to lower fatality rates. Such a vaccine would have to be inexpensive, safe, and provide sustained protection, preferably after a single dose. Novel regimens are also needed for PEP to reduce the need for the already scarce and costly RIG and to reduce the number of vaccine doses to one or two. In this review, the pipeline of new rabies vaccines that are in pre-clinical testing is provided and an opinion on those that might be best suited as potential replacements for the currently used vaccines is offered

Efficient immunization of rhesus macaques with an HCV candidate vaccine by heterologous priming-boosting with novel adenoviral vectors based on different serotypes

Efficient vaccination against viral agents requires a strong T-cell-mediated immune response to clear viral-infected cells. Optimal vaccination can be achieved by administration of recombinant viral vectors encoding phatogen antigens. Adenoviral vectors have attracted considerable attention as potential viral vectors for genetic vaccination owing to their favorable safety profile and potent transduction efficiency following intramuscular injection. However, the neutralizing antibody response against adenoviral capsid proteins following adenoviral vectors injection limits the success of vaccination protocols based on multiple administrations of the same adenoviral serotype. In this work, we describe efficient immunization of rhesus macaques, the preferred model for preclinical assessment, with an HCV candidate vaccine by heterologous priming-boosting with adenoviral vectors based on different serotypes. The induced responses are broad and show significant cross-strain reactivity. Boosting can be delayed for over 2 years after priming, indicating that there is long-term maintenance of resting memory cells

Recombinant adenovirus vectors expressing interleukin-5 and -6 specifically enhance mucosal immunoglobulin A responses in the lung

In this study, we have examined the in vivo effects of interleukin-5 (IL-5) and IL-6 over-expression on systemic and mucosal immune responses using recombinant human type 5 adenoviruses capable of expressing these cytokines upon infection. A recombinant adenovirus containing the murine IL-5 gene within the E3 region was constructed and found to express high levels of IL-5 protein both in vitro and in vivo. Intranasal inoculation of mice with this vector or a vector expressing murine IL-6 increased adenovirus-specific immunoglobulin A (IgA) titres in lung lavage fluid threefold compared with those elicited by control virus. The simultaneous expression of both cytokines by co-inoculation altered the kinetics of the mucosal anti-adenovirus IgA response and resulted in a more than additive increase in antibody titres. The co-expression effect on IgA synthesis was not due to an increase in numbers of antigen-specific resident lung tissue lymphocytes. When mucosal IgG responses were examined, IL-6 expression had the largest impact on anti-adenovirus levels, whereas co-expression produced an intermediate response. Systemic immune responses were also affected by IL-6 expression as a twofold increase in serum IgG anti-adenovirus titres was observed after a secondary challenge with wild-type adenovirus. These results demonstrate a relevant role for IL-5 and IL-6 in the development of mucosal immune responses in vivo and suggest that the incorporation of either IL-5 and/or IL-6 into recombinant adenovirus vectors may be a useful tool in the development of mucosal vaccines