Vaccines against toxoplasma gondii : challenges and opportunities

Development of vaccines against Toxoplasma gondii infection in humans is of high priority, given the high burden of disease in some areas of the world like South America, and the lack of effective drugs with few adverse effects. Rodent models have been used in research on vaccines against T. gondii over the past decades. However, regardless of the vaccine construct, the vaccines have not been able to induce protective immunity when the organism is challenged with T. gondii, either directly or via a vector. Only a few live, attenuated T. gondii strains used for immunization have been able to confer protective immunity, which is measured by a lack of tissue cysts after challenge. Furthermore, challenge with low virulence strains, especially strains with genotype II, will probably be insufficient to provide protection against the more virulent T. gondii strains, such as those with genotypes I or II, or those genotypes from South America not belonging to genotype I, II or III. Future studies should use animal models besides rodents, and challenges should be performed with at least one genotype II T. gondii and one of the more virulent genotypes. Endpoints like maternal-foetal transmission and prevention of eye disease are important in addition to the traditional endpoint of survival or reduction in numbers of brain cysts after challenge

Marine macroalgae from the Gulf of Carpentaria, tropical northern Australia

Over the last two decades, CSIRO surveys of the seagrass communities in the south-western Gulf of Carpentaria and at Groote Eylandt, the Northern Territory, have provided opportunities for the collection of marine macroalgae from this poorly explored, remote region. Although the cruises did not concentrate on macroalgal communities which typically grow on rocky substrates, 64 specific and subspecific taxa of marine Chlorophyta, Phaeophyceae and Rhodophyta were collected, including 30 species newly recorded for the Gulf. The majority of Gulf species also occur on the tropical eastern Australian coast. One hundred and thirteen macroalgal taxa are now known to occur in the Gulf of Carpentaria, the number from the present study supplemented by collections from the 1948 Arnhem Land Expedition and from an ethnobiological study on Groote Eylandt during the 1970s. Twelve species are recorded by all three Gulf studies and 23 species are reported by two studies. The relatively low number of species common to more than one study is thought to result from each study's narrow sampling window which fails to adequately document the considerable spatial and temporal variability of macroalgal species. Accordingly, the number of species presently recorded for the Gulf is considered to be an underestimate of macroalgal biodiversity for the region. It is clear that further detailed taxonomic and ecological investigations are urgently required before the full extent of macroalgal biodiversity in tropical Australia can be appreciated

Morphology, flowering and seed production of Zostera capricorni Aschers. in subtropical Australia

The vegetative morphology, flowering characteristics, seed production, and seed distribution in the sediment of the seagrass Zostera capricorni Aschers. were studied for 18 months by monthly sampling. Three seagrass zones were studied. In each of these zones there was a different morphological type of Z. capricorni: small, dense plants in the midshore zone; large, sparse plants in the offshore zone; medium size and medium density plants in the inshore zone. The distribution of seeds in the sediment was also studied in bare areas adjacent to these vegetated zones. Flowering lasted for 8 months, from September to April, with the highest percentage of shoots flowering in September and November. Flowering lasted longest in the midshore zone (7 months), compared with the inshore (3 months) and offshore (4 months) zones. The density of flowering shoots was also higher in the midshore zone (341 ± 14.0 flowering shoots m) than in the inshore (4 ± 1.0) or offshore (12 ± 4.0) zones. Both the mean number of spathes per shoot (3.1 ± 0.07), and the number of female flowers per spathe (4.8 ± 0.20) did not vary significantly between zones. However, there were more male flowers per spathe in the offshore (10.5 ± 1.55) than in the inshore (5.6 ± 1.60) or midshore (5.4 ± 0.88) zones. Although most seeds were found in the midshore zone during the flowering season (177m ± 28.4), some seeds remained in the sediment for 4 months after seed production had ceased. Few seeds were found outside the seagrass beds, of these most were in bare areas long-shore of the seagrass