Vaccine-bednet interaction in malaria control
Malaria intervention by stage.
The interaction between different intervention methods for malaria is poorly understood, especially due to the complex and transient nature of malaria immunity. Yael Artzy-Randrup et al. (pp. 3014–3019) developed a mathematical model of malaria transmission to examine the interaction between two different forms of malaria intervention: vaccination and insecticide-treated bednets. The authors considered the three leading malaria vaccine classes currently in development, namely preerythrocytic vaccines, which reduce the chance of being infected; blood stage vaccines, which reduce the level of disease severity and fatality; and transmission-blocking vaccines, which disrupt the malaria transmission cycle. The authors found both synergistic and antagonistic interactions when treated bednets were used in combination with different vaccine types. When treated bednets were combined with either blood stage or preerythrocytic vaccines, their interactions reduced levels of natural immunity in the population and increased levels of morbidity in old age groups. In contrast, the combination of transmission-blocking vaccines with treated bednets was synergistic, lowering morbidity and increasing the probability of disease elimination. The authors suggest that transmission-blocking vaccines combined with treated bednets could serve as a highly effective means of malaria control. Future malaria control programs should consider both synergistic and antagonistic interactions between vaccines and other control measures, according to the authors. — S.R.
Asian climate events and European plague
Burial of plague victims at Tournai, Belgium, ca. 1352.
The persistence of a plague pandemic in Europe between the 14th and 19th centuries is generally attributed to the establishment of Yersinia pestis bacterium in European rodent populations following the pathogen’s initial introduction. Searching for reservoirs of recurrent plague reemergence, Boris Schmid et al. (pp. 3020–3025) examined 15 tree-ring climate records from Europe and Asia, as well as a dataset of 7,711 historical plague outbreaks. The authors found no evidence of a persistent rodent reservoir of plague in Europe. Instead, variable climate conditions that are known to affect present-day wildlife outbreaks of plague in Asia were found to occur in juniper tree ring chronologies from the Karakorum Mountains of Pakistan. The authors report that the climate events in Asia consistently preceded plague reintroductions in Europe by approximately 15 years. The results suggest that plague infection may have spread from Asian reservoirs to Europe via trade routes, with the timing of outbreaks related to climatic fluctuations, and that the pathogen may not have resided in European rodent reservoirs, according to the authors. — P.G.
Evolution of herbivory in an insect species
Scaptomyza flava. Image courtesy of Dick Belgers (photographer).
The emergence of new protein families has frequently accompanied evolutionary transitions in behaviors such as feeding or locomotion. Benjamin Goldman-Huertas et al. (pp. 3026–3031) investigated whether changes in olfactory receptor proteins accompanied the evolution of herbivory in the insect Scaptomyza flava, which evolved from ancestors that fed on microbes around 20 million years ago. The authors compared the behavioral responses of S. flava and Drosophila melanogaster, a closely related species that feeds on yeast in decaying plant tissues, to volatile compounds emitted by yeast and the plant Arabidopsis thaliana. D. melanogaster was strongly attracted to yeast volatiles, but S. flava failed to respond to yeast volatiles. Leaf volatiles also stimulated strong antennal responses in S. flava, as measured by electroantennography, whereas yeast volatiles stimulated weak antennal responses. D. melanogaster displayed an opposite pattern of responses. Comparison of the insects’ genomes revealed that genes encoding receptors of yeast volatiles in D. melanogaster had either been deleted or rendered inactive in the S. flava genome. The S. flava genome also displayed evidence of positive selection for a gene that sensitizes neurons to leaf volatiles in other insects. According to the authors, evolutionary changes in olfactory receptor proteins may have supported the emergence of herbivory in S. flava. — J.P.J.
Maternal sounds and prenatal brain plasticity
Ultrasonography of premature infant at 1 month of age, showing auditory cortex (A), frontal horn (B), and corpus callosum (C).
Although exposure to the mother’s voice and heartbeat is one of the first fetal sensory experiences, the impact of prenatal exposure to maternal sounds on the developing brain is unclear. Alexandra Webb et al. (pp. 3152–3157) recorded the voices and heartbeats of the mothers of 21 babies born prematurely, filtered the recordings to simulate womb sounds, and played the sounds to the babies for 3 hours each day during the first month of life. Ultrasonography of the babies’ brains at one month of age showed that the babies exposed to maternal sounds had a significantly larger auditory cortex in both hemispheres than babies exposed to environmental hospital noise alone. The authors found that the effect of maternal sounds on brain development may have been specific to the auditory cortex; measurements of other brain structures, such as the corpus callosum, did not significantly differ between infants exposed to maternal sounds and those exposed to hospital environmental noise. The results suggest a link between maternal womb sounds and the prenatal development of the auditory cortex, according to the authors. — P.G.
Blood-based tumor detection
Illustration of minicircles (dark green) and expressed SEAP reporter (bright green). Image courtesy of Jim Strommer (Stanford University, Stanford, CA).
To be clinically useful, blood-based biomarkers for early tumor detection must display sufficient concentrations, broad applicability to various tumor types, and high specificity to tumor cells. John Ronald et al. (pp. 3068–3073) engineered a minicircle, a circular sequence of DNA activated by a tumor-specific promoter. When activated, a reporter gene on the minicircle produces secreted embryonic alkaline phosphatase (SEAP), which can be detected in the bloodstream. The authors found that administration of the minicircle to mice enabled differentiation between mice bearing human melanoma metastases and tumor-free mice based on blood SEAP levels. Additional experiments in mice with lung tumors found that cumulative SEAP levels correlated with lung tumor burden, suggesting that SEAP levels may serve as an indicator of disease severity. The minicircle system’s modular nature allows for continued improvement to enhance specificity and sensitivity. The results suggest that an early tumor detection system may enable the screening of high-risk populations for tumor appearance or recurrence, according to the authors. — P.G.