Biology subjects

Shiau, J. C.

Publications and source records attributed to Shiau, J. C..

8 recordsLinked to original sources

bioRxiv2024

Type-I IFNs induce GBPs and lysosomal defense in hepatocytes to control malaria

Plasmodium parasites undergo development and replication within the hepatocytes before infecting the erythrocytes and initiating clinical malaria. Although type-I interferons (IFNs) are known to hinder Plasmodium infection within the liver, the underlying mechanisms remain unclear. Here, we describe two IFN-I-driven hepatocyte antimicrobial programs controlling liver-stage malaria. First, oxidative defense by NADPH oxidases 2 and 4 triggers a pathway of lysosomal fusion with the parasitophorous vacuole (PV) to help clear Plasmodium. Second, guanylate-binding protein (GBP) 1 disruption of the PV activates caspase-1 inflammasome, inducing pyroptosis to remove the infected host cells. Remarkably, both human and mouse hepatocytes enlist these cell-autonomous immune programs to eliminate Plasmodium; their pharmacologic or genetic inhibition led to profound malarial susceptibility, and are essential in vivo. In addition to identifying the IFN-I-mediated cell-autonomous immune circuits controlling Plasmodium infection in the hepatocytes, this study extends our understanding of how non-immune cells are integral to protective immunity against malaria.

immunology↗

bioRxiv2024

Thermal variation influences the transcriptome of the major malaria vector Anopheles stephensi.

The abundance and distribution of ectotherms is being shaped at unprecedented scales by human-induced climate change. Unraveling molecular adaptations to thermal variation is prescient. Vector-borne diseases are of particular concern and although mosquitoes are responsible for most of the 621 million cases annually, their response to temperature is not well characterized. We describe the transcriptome of the major vector for human malaria, Anopheles stephensi maintained under a diurnal temperature regime (DTR) totaling 9{degrees}C and daily means of 20{degrees}C, 24{degrees}C and 28{degrees}C respectively. Gene expression profiles were examined in the midguts and carcasses of adult mosquitoes from one to 19 days post-blood meal. Differences in temporal expression profiles at each temperature revealed a total of 3,106 and 3,590 genes in the carcasses and midguts respectively and analyzed further to make three inferences. First, we identified genes with shared temporal expression profiles across all three temperatures, suggesting their indispensability to mosquito life history. Second, tolerance to 20 DTR 9{degrees}C and 28 DTR 9{degrees}C was associated with a larger and more diverse repertoire of gene products compared to 24 DTR 9{degrees}C; assuming physiological costs scale accordingly, this finding could explain the fitness trade-offs underlying the unimodal effect of temperature. Third, the long duration of our study revealed two general trends in gene expression, representative of a coordinated, tissue- and temperature-specific response to blood meal digestion, managing oxidative stress, and reproduction. Our results suggest how temperature could regulate the mosquitos capacity to transmit Plasmodium parasites and offer a reference point for understanding ectotherm adaptation.

molecular biology↗

bioRxiv2024

Oviposition status and sugar availability influence measures of transmission potential in malaria-infected mosquitoes.

BackgroundLike other oviparous organisms, the gonotrophic cycle of mosquitoes is not complete until they have selected a suitable habitat to oviposit. In addition to the evolutionary constraints associated with selective oviposition behavior, the physiological demands relative to an organisms oviposition status also influences their nutrient requirement from the environment. Yet, studies that measure transmission potential (vectorial capacity or competence) of mosquito-borne parasites rarely consider if the rates of parasite replication and development could be influenced by these constraints resulting from whether mosquitoes have completed their gonotrophic cycle. MethodsAnopheles stephensi mosquitoes were infected with Plasmodium berghei the rodent analog of human malaria and maintained on 1% or 10% dextrose and either provided oviposition sites ( oviposited herein) to complete their gonotrophic cycle or forced to retain eggs ( non-oviposited). Transmission potential in the four groups was measured up to 27 days post-infection as 1) the rates of vector survival, 2) rates of sporozoite migration to the salivary glands ( extrinsic incubation period or EIP), and 3), sporozoite densities. ResultsIn the two groups of oviposited mosquitoes, rates of sporozoite migration and densities in the salivary glands were clearly higher in mosquitoes fed 10% dextrose. In non-oviposited mosquitoes however, rates of sporozoite migration and densities were independent of sugar concentrations, although both measures were slightly lower than oviposited mosquitoes fed 10% dextrose. Rates of vector survival were higher in non-oviposited mosquitoes. ConclusionsTaken together, these results suggest vectorial capacity for malaria parasites may be dependent on nutrient availability and oviposition/gonotrophic status and as such, argue for more careful consideration of this interaction when estimating transmission potential; costs to parasite fitness and vector survival were buffered against changes in nutritional availability from the environment in non-oviposited mosquitoes, but not oviposited mosquitoes. In general, however, these patterns suggest parasite fitness may be dependent on complex interactions between physiological (nutrition) and evolutionary (egg-retention) trade-offs in the vector, with potential implications for disease transmission and management. For instance, while reducing availability of oviposition sites and environmental sources of nutrition are key components of integrated vector management strategies, their abundance and distribution is under strong selection pressure from the patterns associated with climate change. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=100 SRC="FIGDIR/small/577126v2_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@152dd45org.highwire.dtl.DTLVardef@13d140forg.highwire.dtl.DTLVardef@efeb93org.highwire.dtl.DTLVardef@15312d7_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2022

Blood meals from 'dead-end' vertebrate hosts enhance transmission potential of malaria-infected mosquitoes

Ingestion of an additional blood meal(s) by mosquitoes can accelerate parasite migration to the salivary glands in infected mosquitoes. Most studies, however, offer blood from the same vertebrate host species as the original challenge (for e.g., human for primary and additional blood meals). Here, we show a second blood meal from bovine and canine hosts can also enhance sporozoite migration in Anopheles stephensi mosquitoes infected with the human- and rodent-restricted Plasmodium falciparum and P. berghei respectively. The extrinsic incubation period (time to sporozoite appearance in salivary glands) showed more consistent reductions with blood from human and bovine donors than canine blood, although the latters effect may be confounded by the toxicity, albeit non-specific, associated with the anticoagulant used to collect whole blood from donors. The complex patterns of enhancement highlight the limitations of a laboratory system but are nonetheless reminiscent of parasite host-specificity and mosquito adaptations, and the genetic predisposition of An. stephensi for bovine blood. We suggest that in natural settings, a blood meal from any vertebrate host could accentuate the risk of human infections by P. falciparum, although our observations should also be applicable to other species of Plasmodium and indeed other vector-borne diseases such as arboviruses for instance. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=185 HEIGHT=200 SRC="FIGDIR/small/521872v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@10ec4d7org.highwire.dtl.DTLVardef@9d0d21org.highwire.dtl.DTLVardef@c92628org.highwire.dtl.DTLVardef@1e83587_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSO_LIPlasmodium falciparum and P. berghei cause malaria in humans and rodents, respectively. C_LIO_LIThey are vectored by Anopheles species that can also imbibe blood from other vertebrate species. C_LIO_LIParasite development is enhanced after another blood meal, usually from the same host (e.g., human). C_LIO_LIHere, bovine, and canine blood also enhanced development of Plasmodium species in An. stephensi. C_LIO_LIIn natural settings, blood from any host could enhance development of vector transmitted parasites. C_LI

ecology↗

bioRxiv2021

Alkyne modified purines for assessing activation of Plasmodium vivax hypnozoites and growth of pre-erythrocytic and erythrocytic stages in Plasmodium spp.

Malaria is a major global health problem which predominantly afflicts developing countries. Although many antimalarial therapies are currently available, the protozoan parasite causing this disease, Plasmodium spp., continues to evade eradication efforts. One biological phenomenon hampering eradication efforts is the parasites ability to arrest development, transform into a drug-insensitive form, and then resume growth post-therapy. Currently, the mechanisms by which the parasite enters arrested development, or dormancy, and later recrudesces or reactivates to continue development, are unknown and the malaria field lacks techniques to study these elusive mechanisms. Since Plasmodium spp. salvage purines for DNA synthesis, we hypothesized that alkyne-containing purine nucleosides could be used to develop a DNA synthesis marker which could be used to investigate mechanisms behind dormancy. Using copper-catalyzed click chemistry methods, we observe incorporation of alkyne modified adenosine, inosine, and hypoxanthine in actively replicating asexual blood stages of P. falciparum and incorporation of modified adenosine in actively replicating liver stage schizonts of P. vivax. Notably, these modified purines were not incorporated in dormant liver stage hypnozoites, suggesting this marker could be used as a tool to differentiate replicating and non-replicating liver forms and, more broadly, a tool for advancing our understanding Plasmodium dormancy mechanisms.

microbiology↗

bioRxiv2021

Altered cleavage of Caspase-1 in hepatocytes limits control of malaria in the liver

Malaria, caused by Plasmodium parasites, is a devastating disease that kills over half a million people each year1. Plasmodium sporozoites inoculated by mosquitoes into mammalian hosts undergo a clinically silent phase of obligatory development and replication in hepatocytes before initiating the life-threatening blood-stage of malaria2. Thus, understanding the immune responses elicited by Plasmodium infection in the liver is key to controlling clinical malaria and transmission3,4. Here, we show that Plasmodium DNA can be detected by AIM2 (absent in melanoma 2) sensors in the infected hepatocytes, resulting in Caspase-1 activation and pyroptotic cell-death. However, Caspase-1 was observed to undergo only partial cleavage in hepatocytes, limiting pyroptosis, and the maturation of pro-inflammatory cytokines classically associated with Caspase-1 activation. We discovered that the extent of Caspase-1 cleavage in cells is determined by the expression of ASC (apoptosis-associated speck-like protein containing a CARD). ASC expression is inherently low in hepatocytes, and transgenically enhancing it in the hepatocytes induced complete processing of Caspase-1, efficient secretion of pro-inflammatory cytokines, enhanced pyroptotic cell-death, and markedly improved control of malaria infection in the liver. In addition to describing a novel pathway of natural immunity to malaria, our findings uncover a key aspect of liver biology that may have been exploited during evolution by successful hepatotropic pathogens.

immunology↗

bioRxiv2019

Field relevant variation in ambient temperature modifies the density-dependent establishment of Plasmodium falciparum in mosquitoes: implications for the infectious reservoir and beyond?

The relationship between Plasmodium falciparum gametocyte density and infections in mosquitoes is central to understanding the rates of transmission with important implications for control. Here, we determined whether field relevant variation in environmental temperature could also modulate this relationship. Anopheles stephensi were challenged with three densities of P. falciparum gametocytes spanning a [~]10-fold gradient, and housed under diurnal/daily temperature range (\"DTR\") of 9{degrees}C around means of 20{degrees}C, 24{degrees}C and 28{degrees}C. At the peak stages of infection for each temperature, the proportion of mosquitoes infected with oocysts in the midguts or infectious with sporozoites in the salivary glands were measured (referred to collectively as vector competence hereon), in addition to oocyst intensities from infected midguts. While vector competence was similar at 20 DTR 9{degrees}C and 24 DTR 9{degrees}C, the proportion of mosquitoes infected and subsequently infectious were also comparable, with evidence, surprisingly, for higher vector competence in mosquitoes challenged with intermediate gametocyte densities. For the same gametocyte densities however, severe reduction in the proportion of infectious mosquitoes was accompanied by a significant decline in vector competence at 28 DTR 9{degrees}C, although density per se showed a positive and linear effect at this temperature. Unlike vector competence, oocyst intensities decreased with increasing temperatures with a predominantly positive and linear association with gametocyte density, especially at 28 DTR 9{degrees}C. Oocyst intensities across individual infected midguts suggested temperature-specific differences in mosquito susceptibility/resistance: at 20 DTR 9{degrees}C and 24 DTR 9{degrees}C, dispersion (aggregation) increased in a density-dependent manner but not at 28 DTR 9{degrees}C where the distributions were consistently random. Limitations notwithstanding, our results have manifold implications in, for instance, how variation in temperature could modify seasonal dynamics of infectious reservoirs and transmission and the contribution of high-/patent- and low-density/sub-patent carriers, to suggestions for design and deployment of transmission-blocking vaccines/drugs, but with a cautionary note suggesting how low efficacy could lead to transmission enhancement in certain environments.

ecology↗

bioRxiv2017

Carry-over effects of larval microclimate on the transmission potential of a mosquito-borne pathogen

Climate shapes the transmission of mosquito-borne pathogens through impacts on both the vector and the pathogen. In addition to direct effects of the environment, carry-over effects from previous life history stages can influence mosquito traits relevant to disease transmission. While this has been explored in a laboratory setting, the net effect of temperature-mediated carry-over effects due to relevant environmental variation in the larval stage is ambiguous. Here, we use data collected from a semi-field experiment investigating dengue dynamics in Aedes albopictus across a natural environmental gradient to parameterize a dengue transmission model. We reared Ae. albopictus across three different land classes characterized by their proportion of impervious surface. Emerged females were offered a dengue infectious bloodmeal, kept at a constant 27 {degrees}C, and assayed for infection, dissemination, and infectiousness 21 days post infection. Incorporating carry-over effects of larval environment on measures of vector competence resulted in lower predicted dengue transmission potential across land class and season, however a strong positive relationship with larval environmental temperature remained. Given the significant impact of carry-over effects, future mechanistic models of disease transmission should include both direct and carry-over effects of environmental temperature.

ecology↗