New vaccines for mosquito borne illnesses
Vaccines are an essential tool of public health. New technologies and techniques have increased the speed at which vaccines can be devel- oped and deployed. Two newer vaccines targeting the mosquito-borne viruses malaria and Zika virus highlight the promise and perils of modern vaccine development. Zika Virus Pregnant women infected with Zika virus are at high risk for miscarriages and congenital disabilities in infants, including small heads and aberrant neurological development. The lat- est Zika outbreak was in 2017, but it is expected to be a cyclic virus, with periods of explosive infection and relative quiet. A promising new vaccine made from inactivated Zika particles is safe in nonpregnant humans. In animal models, it appears to be 80-90% effective at preventing congenital malformations when given during pregnancy. Animal testing also reveals the presence of ma- ternal Zika fighting antibodies in the fetuses of females who received vaccines before becoming pregnant. The big question is whether the vaccine protects pregnant humans and their fetuses from the virus. Human trials to confirm these results are difficult to structure because of ethical concerns. Even assessing the potential risks and unintended consequences can be challenging. To date, no studies have examined the impact of Zika vaccines on human fetuses and pregnant people. The race continues to find a safe, effective Zika vaccine before the next large outbreak. Malaria Malaria is caused by a plasmodium passed to humans from an infected mosquito bite. Children living in endemic areas are particularly vulnerable, accounting for a large portion of almost half a million annual deaths. Because
malaria has a multi-stage, multi-host life cycle, producing an effective malaria vaccine has been difficult. RTS,S, a malaria vaccine developed by GlaxoSmithKline ® , was endorsed by the World Health Organization in October 2021. The vaccine induces antibodies that coat the parasites' initial infectious form, preventing them from gaining a foothold in the liver. While only partially effective at preventing malaria infection, the vaccine reduces the likelihood of severe disease, hospitalization, and death. Combin- ing doses with anti-malarial drugs and timing doses to coincide with seasonal rains could increase the vaccine efficacy. Despite its promise for the fight against malaria, ethical con- cerns were raised over RTS,S, including failure to follow bioethical standards during clinical trials. Critics say families were included in pilot vaccination efforts without informed consent. The vaccine was also linked to a significant increase in mortality of girls but not boys. More studies are required to determine if the disproportional female deaths were by chance or if the vaccine caused increased susceptibil- ity to other life-threatening diseases. These two stories illustrate the difficulties of the race to combat deadly pathogens while simultaneously protecting vulnerable people. n REFERENCES: Laurens MB. RTS,S/AS01 vaccine (Mosquirix™): an overview. Hum Vaccin Immunother. (2020) 3;16(3):480-489. DOI 10.1080/21645515.2019.1669415 “WHO recommends groundbreaking malaria vaccine for children at risk.: World Health Organization. 6 October 2021. https://www.who.int/news/item/06-10-2021- who-recommends-groundbreaking-malaria-vaccine-for-children-at-risk Microbiome-friendly food benefits undernourished children New research has uncovered a potential link between the gut bacteria of malnourished children and their ability to recover from the effect of starvation. Using fecal samples, researchers had previously com- pared the intestinal micorbiome of healthy children to those suffere- ing from moderate to severe malnutrition noting the gut biomes of undernourished children appeard 'stunted' in development. When gut micobes from undernourished children were transfeered to mice, the mice developed metabolic dysfunctions.Like the children, the mice broke down amino acids for energy rather than sugars, and their rate of weight gain and bone growth slowed. Researchers then monitored 118 children under age 2 who had moderate malnutrition. Half received the standard calorie-dense supplemental food, the other half received a different supplement containing foods selected to nourish the gut microbiome. Both sup- plemental foods used locally available ingredients, a critical feature for long-term implementation. Even though the microbiota-directed food regime contained fewer total calories, those children gained more weight and grew more rapidly than the group receiving the standard supplement. The microbiome-nourished children also had increased levels of blood proteins associated with bone growth and brain development. n REFERENCE: Chen R.Y et al. A Microbiota-direct Food Intervention for Under- nourished Children. New England J Med (2021) 384:1517-1528 DOI:10.1056/NEJ- Moa2023294.
Genetic trait in caterpillars
Parasitic infections can cause unusual changes in host behavior. For example, toxoplasma causes mice to approach cats, and certain fungal infections turn ants into zombie infection spreaders. How these in- fections cause behavioral changes is poorly understood. Using a rare viral infection in cotton bollworm, scientists are getting clues. A group of insect viruses, nucleopolyhedroviruses (NPV), compel caterpillars to climb to the top of plants before they die. Current thinking is that this aids in the transmission of the virus. When the dying larvae release viral particles over the foliage, there is a higher chance that a new host will become infected. After treating larvae with virally contaminated food, researchers tracked caterpillars’ movement toward the light, a phenomenon called phototaxis. Researchers measured increased phototaxis in infected caterpillars. They also measured changes in gene expression throughout the disease. More than 2,000 genes showed changes in expression levels during infection. Six genes related to light perception and eye function were dramatically upreg- ulated in infected caterpillars. How viral infection causes increased expression of these genes is unknown. This research provides insight into parasite-caused behavioral changes and may also reveal details about the biological basis of behavior. n REFERENCE: Liu, X., et al. Baculoviruses hijack the visual perception of their cat- erpillar hosts to induce climbing behaviour thus promoting virus dispersal. Mol Ecol (2022) 31:2752-2765. DOI: 10.1111/mec.16425
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