Research Roundup: New insights into Zika virus, using silk to preserve blood samples, and a single dose oral cholera vaccine
Last Wednesday, researchers from the Washington University School of Medicine, the University of São Paulo, and the Chinese Academy of Sciences offered new insights into the impact of the Zika virus on fetal brain development in mice, publishing their findings in Cell, Nature, and Cell Stem Cell, respectively. The first two studies sought to successfully infect pregnant mice with Zika—a feat in itself as mice don’t often fall ill after infection with the virus. Consequently, the team at Washington University used a genetically modified mouse with a weakened immune system as well as a mouse whose immune system was weakened by an antibody, while researchers at the University of São Paulo used a particularly high dose. The team at Washington University detected placental insufficiency in the infected mice—which limits blood flow to the fetus—and the team at University of São Paulo reported intrauterine growth restriction, a condition restricting the growth of the fetus. When the virus reached the fetal brains, both teams witnessed a thinning of brain tissue and cell death. The concentration of the virus in the brain was limited, which inhibited further research on how Zika behaves once in the brain. The team at the Chinese Academy of Sciences, however, injected the virus directly into the brains of fetal mice, and they determined that the virus targets neural progenitor cells and causes the fetal brain to shrink.
Silk has been used in developing heat-stable vaccines and drugs, and now, researchers at Tufts University have demonstrated that silk can be used to maintain blood samples in low-resource settings. Blood-based diagnostics are only effective if certain proteins, which indicate either the presence of a pathogen or the immune system’s response to it, are preserved, however, heat and humidity can directly damage the proteins or cause enzymes in the blood to attack the proteins. Labs prefer that blood samples are refrigerated, although they can also be dried on special filter paper that can withstand heat but which often doesn’t hold enough blood for analysis. The team at Tufts created a silk-based powder and solution, combined it with blood samples, and allowed it to dry. The samples were then stored at high temperatures (72 to 113ºF) and remained viable for 84 days.
GHTC member the International Vaccine Institute (IVI) announced last week that a single dose of the oral cholera vaccine Shanchol, currently administered in two-dose regimens, provides protection against the disease. The two-dose regimen provides 65 percent protection against cholera for at least five years, while the single dose demonstrated 40 percent protection against the disease for at least six months. While the two-dose regimen is preferred, the single dose could be appropriate for epidemics or in settings where the two-dose vaccine schedule is impractical. The study enrolled 204,700 individuals residing in the urban slums of Mirpur in Dhaka, Bangladesh, where cholera is endemic. In addition to reducing cases by 40 percent, the vaccine resulted in a 63 percent decrease in cases of severely dehydrating cholera.