Zika may be prevented by previous exposure to dengue virus
A recent study, published in Science, has found that previous exposure to the dengue virus could protect against the Zika virus. Both viruses are spread by the same species of mosquito, Aedes aegypti and Aedes albopictus. The dengue virus is genetically similar to the Zika virus and the researchers sought to understand the role of pre-existing dengue immunity in Zika infection.
The team was able to take advantage of an ongoing long-term study of urban slum health to compare results from before and after the 2015 Zika outbreak. During the Brazilian epidemic just under three-quarters of the inhabitants of the studied slum caught the virus. Infection rates varied from as low as 29% in one area to up to 83% in others.
While immunity to the dengue virus had been shown experimentally to protect against infection from the Zika virus, its influence had not been thoroughly studied in a human population. The results of the current study showed that those who had previously been exposed to the dengue virus had antibodies which protected them from Zika. The researchers hypothesised that the high rates of immunity against Zika caused by infection with either Zika or dengue will likely avoid a similar outbreak to that of 2015.
The genetic alphabet has just been expanded. DNA is composed of four letters, or bases, but researchers have recently published a system using eight. The new system, introduced in Science is named Hachimoji DNA, hachi meaning eight and moji meaning letter. One of the paper’s authors, Dr. Benner, has reportedly been working on expanding the DNA alphabet since 1985.
But creating new artificial bases that don’t exist in nature was never going to be easy. They have to fit into the double helix structure of DNA and be read by enzymes in order to create proteins. RNA polymerases – enzymes that transcribe the genetic information from DNA – were able to transcribe information from the Hachimoji nucleotides. The authors reported that the eight nucleotide bases – four natural, four synthetic – can be transcribed into RNA and are have therefore been shown to be structurally similar enough to the four traditional bases to fit requirements needed for ‘Darwinian evolution’. RNA acts as a kind of translator between DNA and proteins and enables cells to produce proteins from their DNA “recipes”. In this case the enzyme the researchers used was an engineered T7 RNA polymerase, which was able to translate the new eight letter code into an RNA strand.
Videos, songs and documents have previously been encoded in DNA, and Hachimoji DNA offers the potential to expand this storage opportunity. Expanding the DNA alphabet has other potential advantages; it is currently unknown whether Hachimoji DNA could support life in the same way the four natural bases do, but it could change the way we think about extra-terrestrial lifeforms and what they are made of.
How the zebra got its stripes
A recent study in Plos One has suggested a plausible reason for the stripes on nature’s most recognisable member of the Equidae family. At a horse farm and conservation centre for zebras near Bristol, UK, the researchers filmed horse flies trying to bite the animals. They observed a lower landing rate on zebras than for horses, and that the flies were unable to fly in a controlled manner, which led to fewer bites. The researchers theorized that the fly’s low-resolution vision might be dazzled by the stark black and white stripes.
To control for the different smells of zebras and horses, seven horses were dressed in a zebra-striped coat. The rate of landing on the exposed head of the horse remained the same while decreasing on the body, confirming the initial results.
However, it is worth noting that these experiments were carried out in England and the native species of flies in Africa may behave differently. In the meantime, perhaps we will see some zebra print-wearing horse riders taking advantage of the results of this study.
Articles written by Isobel Tibbetts