Favorable Host Research Articles

Effects of Aphids on The Growth of Different Varieties of Indian Mustard

The purpose of the experiment was to determine the prevalence of mustard aphids on various varieties of mustard in the field in Jassowala, Dehradun, Uttarakhand, from January to April of 2022. Three replications and a randomised complete block design were used to set up the experiment. The tolerant variations of eight mustard types, including T1 (RH7859), T2 (RH781), T3 (RH785), T4 (VARDHAN), T5 (RH7847), T6 (RH9006), T7 (RH8546), and T8 (VARUNA), were assessed against aphid infestation on plants, leaves, inflorescence, and pods. Regarding aphid infestation on plants, leaves, inflorescence, and pod, T8 (VARUNA) was shown to be the most favoured host out of the eight varieties of mustard, whereas T1 (RH7859), performed as the least preferred variety. T1 (RH7859), the variety most vulnerable to aphids, yielded the lowest seed yield per plot and T8 (VARUNA) seed yield with the least amount of aphid infestation. According to the study, the T8 (VARUNA) produced the maximum yield and showed the least amount of aphid infestation. On the other hand, T1 (RH7859), yielded the fewest seeds and displayed the most aphid infestation.

Risk of mortality in Fusobacterium species bloodstream infection from a large Australian cohort.

Fusobacterium species are anaerobic Gram-negative bacilli which are uncommon causes of bloodstream infection (BSI). This genus commonly colonises the gastrointestinal tract and can result in significant morbidity. All blood cultures with growth of Fusobacterium species among residents of Queensland, Australia (population ≈ 5million) were retrospectively identified over a 20-year period. Clinical, microbiological and outcome information was obtained from state-wide databases. 377 incident Fusobacterium species BSI among 375 individuals for an age and sex-standardised incidence of 4.4 per million residents per year. Median age was 47 years (IQR, 24.9-65.8) and 156 (42%) incident episodes were in females. There was a bimodal frequency distribution with respect to age with peaks occurring around 20 and 65 years, respectively. The most identified source of infection was the abdominal (17%), followed by head and neck (12%). 8% of patients had a septic thrombus present, and 4% had an abscess associated with their BSI. Most isolates were F. nucleatum (142, 38%) and F. necrophorum (140, 37%). 9% of isolates were resistant to penicillin. Older age (aHR 1.02, 95% CI 1.01-1.05), healthcare-associated hospital onset (aHR 3.16, 95% CI 1.35-7.40), and Charlson Comorbidity index (aHR 1.20, 95% CI 1.06-1.35) were all associated with 30-day all cause case-fatality. Oropharyngeal source appeared to be a protective factor (P = 0.02). Fusobacterium species BSI results in significant morbidity and can cause death in vulnerable patient groups such as the elderly and those with malignancy. An identifiable oropharyngeal source identifies a favourable host.

Population Dynamics and Nutritional Indices of Spodoptera frugiperda (Lepidoptera: Noctuidae) Reared on Three Crop Species.

The fall armyworm (FAW) is an invasive pest that has been rapidly spreading across China since its detection in Yunnan province in January 2019. Although sugarcane and sorghum have been reported as hosts, their effects on FAW's population growth and life table parameters have not been examined in China. Our research shows that FAW's development and life table metrics vary significantly when reared on sorghum, sugarcane, and maize. Notably, the preadult stage, adult preoviposition period, and total preoviposition period of FAW were markedly longer on sugarcane and sorghum compared to maize. FAW reared on these two crops also exhibited reduced survival rates, pupal weight, fecundity, and lower female-to-male ratios. The study highlights that FAW had lower population growth rates, reproductive rates, and longer generation times on sugarcane and sorghum compared to maize. The consumption index and digestibility index were higher on maize, while conversion efficiency and growth rate were greater on sorghum. Although maize is the most favorable host, FAW can still survive and reproduce on sugarcane and sorghum during the nongrowing season, posing a risk to economically important crops in China. Despite being less favorable for population growth, sugarcane and sorghum still support FAW development and spread. Therefore, enhanced surveillance and early warning measures for sugarcane and sorghum are recommended to monitor FAW population dynamics and mitigate its potential impact on primary host plants.

The Role of Inflammation in the Pathogenesis of Viral Respiratory Infections.

Viral respiratory infections (VRIs) are a leading cause of morbidity and mortality worldwide, making them a significant public health concern. During infection, respiratory viruses, including Influenza virus, SARS-CoV-2, and respiratory syncytial virus (RSV), trigger an antiviral immune response, specifically boosting the inflammatory response that plays a critical role in their pathogenesis. The inflammatory response induced by respiratory viruses can be a double-edged sword since it can be initially induced to be antiviral and protective/reparative from virus-induced injuries. Still, it can also be detrimental to host cells and tissues. However, the mechanisms that differentiate the complex crosstalk between favorable host inflammatory responses and harmful inflammatory responses are poorly understood. This review explores the complex interplay between viral pathogens and the host immune response, mainly focusing on the role of inflammation in the pathogenesis of VRIs. We discuss how inflammation can both contain and exacerbate the progression of viral infections, highlighting potential therapeutic targets and emerging drugs for modulating the aberrant inflammatory responses during VRIs.

Adaptive laboratory evolution and metabolic engineering of Cupriavidus necator for improved catabolism of volatile fatty acids

Bioconversion of high-volume waste streams into value-added products will be an integral component of the growing bioeconomy. Volatile fatty acids (VFAs) (e.g., butyrate, valerate, and hexanoate) are an emerging and promising waste-derived feedstock for microbial carbon upcycling. Cupriavidus necator H16 is a favorable host for conversion of VFAs into various bioproducts due to its diverse carbon metabolism, ease of metabolic engineering, and use at industrial scales. Here, we report that a common strategy to improve product titers in C. necator, deletion of the polyhydroxybutyrate (PHB) biosynthetic operon, results in a significant growth defect on VFA substrates. Using adaptive laboratory evolution, we identify mutations to the regulator gene phaR, the two-component response regulator-histidine kinase pair encoded by H16_A1372/H16_A1373, and the tripartite transporter assembly encoded by H16_A2296-A2298 as causative for improved growth on VFA substrates. Deletion of phaR and H16_A1373 led to significantly reduced NADH abundance accompanied by large changes to expression of genes involved in carbon metabolism, balance of electron carriers, and oxidative stress tolerance that may be responsible for improved growth of these engineered strains. These results provide insight into the role of PHB biosynthesis in carbon and energy metabolism and highlight a key role for the regulator PhaR in global regulatory networks. By combining mutations, we generated platform strains with significant growth improvements on VFAs, which can enable improved conversion of waste-derived VFA substrates to target bioproducts.

Effect of Bio-Agents on Enzymatic Activity and Nematode Management in Tomato Plants Infected with Meloidogyne javanica

The tomato (Solanum esculentum Mill.) is one of the most widely cultivated vegetable crops worldwide. It serves as a favorable host for plant-parasitic nematodes, particularly the root-knot nematode (Meloidogyne javanica). Investigations were carried out to determine the effectiveness of bio-agents against root-knot nematodes in pot conditions. The bio-agents included Metarhizium anisopliae, Bacillus subtilis, Verticillium lecanii, Trichoderma harzianum and, Trichoderma asperellum) against root-knot nematode in pot condition. Effect of bio-agents was also estimated for accumulation of PPO and PAL and Root-knot nematode-infected tomato roots containing phenol. The results of the experiment showed that all the bio-agents significantly increased the levels of PPO, PAL, and phenol in tomato roots, improved plant growth parameters, and reduced nematode reproduction compared to the untreated control. The best treatment with the highest PPO, PAL, and phenol activity among the investigated bio-agents was determined to be Trichoderma harzianum at 3 gm/kg soil, followed by Bacillus subtilis and Metarhizium anisopliae. It improves the plant growth parameter and lowers the number of nematodes in the pot.

THE TYPOLOGIES OF THE HOUSES IN THE MEDINA OF ANNABA-ALGERIA

The patio house is a cultural production, it bears witness to the social practices of ancient societies that shaped its spaces by considering their own cultures and needs, this is how it was born and developed into a spontaneous architecture consistent with the environment, the prevailing climate, the culture and interests of the family and its future generations, For years, the Annaba Medina had suffered from the precariousness of unhealthy, over-densified housing. The original families were leaving and lowincome rural immigrants were finding the Medina a favorable host structure, with large empty mansions and a type of house with patios that lent itself to renting by the piece. The unsuitability of this urban fabric for the current standards and practices of the inhabitants, and contemporary development, were the main causes of the changes made by the Medinese throughout the area, mainly affecting the original urban form. Through this research, we have tried to analyze the traditional domestic space to highlight the new typologies of houses in Medina.

Abstract B013: Host phenotype profiling predicts progression to resection in neoadjuvant pancreatic cancer

Abstract Introduction Neoadjuvant chemotherapy offers a modest survival benefit in pancreatic cancer. Current methods for assessing response to chemotherapy are limited to CA19-9 and post- treatment imaging. However, these methods are not without caveats and focus heavily on tumour biology and staging the tumour, without consideration of host biology or staging the host. We sought to explore the relationship between host biology and outcomes in neoadjuvantly- treated pancreatic cancer, and determine the utility of host phenotype profiling as a tool for predicting chemotherapy response and subsequent progression to resection. Methods Host phenotype profiling was performed by measuring body composition (BC) pre- and post- neoadjuvant chemotherapy in a large international pancreatic cancer cohort (n = 301). Patients with resectable or borderline resectable disease were included if they received chemotherapy with neoadjuvant intent. BC was determined with contrast-enhanced CT scans by measuring single-slice L3 cross-sectional area. Results There were significant differences in BC change from baseline to post-treatment between resected (n = 174) and non-resected patients (n = 127). Patients who did not progress to resection exhibited greater loss in all BC compartments vs those who progressed to resection (muscle area -3.4 vs -0.7, visceral fat -10.1 vs -2.1, subcutaneous fat -12.0 vs -1.4, all p < 0.001, median percentage change per 100 days). We used these values to define a adverse and favourable host phenotypes, which significantly correlated with progression to resection (58.8% adverse phenotype, 74.3% favourable phenotype, p < 0.001). The independence of this effect was confirmed in a logistic regression model with well-established clinico-pathological variables including CA19-19 rise (adverse phenotype OR of non-resection 4.57, 95% CI 1.55-13.48, p = 0.006). Conclusion Host phenotype profiling represents a useful addition to an otherwise limited toolbox of methods for assessing treatment response and selecting for surgery in neoadjuvant pancreatic cancer. Clinicians will be familiar with the subjective “gut feeling” of identifying patients in the clinic who are unlikely to be candidates for surgery, and we demonstrate an objective measurement of this. Early identification of patients on an adverse trajectory may highlight those who would benefit from early intervention such as prehabilitation, salvage change of chemotherapy regimen, or nutritional optimization to switch the phenotype from adverse to favourable and reverse adverse host biology. Citation Format: Adam Bryce, Stephan Dreyer, Ross Dolan, Fieke Froeling, Dario Solinas, Alice Cattelani, Antonio Pea, David Chang. Host phenotype profiling predicts progression to resection in neoadjuvant pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B013.

The cosmic rate of pair-instability supernovae

Abstract Pair-instability supernovae (PISNe) have crucial implications for many astrophysical topics, including the search for very massive stars, the black hole mass spectrum, and galaxy chemical enrichment. To this end, we need to understand where PISNe are across cosmic time, and what are their favourable galactic environments. We present a new determination of the PISN rate as a function of redshift, obtained by combining up-to-date stellar evolution tracks from the PARSEC and FRANEC codes, with an up-to-date semi-empirical determination of the star formation rate and metallicity evolution of star-forming galaxies throughout cosmic history. We find the PISN rate to exhibit a huge dependence on the model assumptions, including the criterion to identify stars unstable to pair production, and the upper limit of the stellar initial mass function. Remarkably, the interplay between the maximum metallicity at which stars explode as PISNe, and the dispersion of the galaxy metallicity distribution, dominates the uncertainties, causing a ∼ seven-orders-of-magnitude PISN rate range. Furthermore, we show a comparison with the core-collapse supernova rate, and study the properties of the favourable PISN host galaxies. According to our results, the main contribution to the PISN rate comes from metallicities between ∼10−3 and 10−2, against the common assumption that views very-low-metallicity, Population III stars as exclusive or dominant PISN progenitors. The strong dependencies we find offer the opportunity to constrain stellar and galaxy evolution models based on possible future (or the lack of) PISN observations.

Dormancy of a specialist herbivore, Anthonomus rufipennis (Coleoptera: Curculionidae), in a dry tropical forest.

The life history aspects of dormancy of the weevil Anthonomus rufipennis LeConte (Coleoptera: Curculionidae) were studied a 57-month period in a seasonally dry tropical forest of central Mexico. Weevil populations and their physiological status were monitored on both the reproductive host tree, Senna polyantha (Collad.) H.S: Irwin & Barneby (Fabales: Fabaceae) and the highly favored refuge host, Tillandsia recurvata L. (Poales: Bromeliaceae) or "ball moss." During the dry season, weevils were only found on the refuge host with a mean total density of 1.014 ± 2.532 individuals/ball moss (N = 1,681). Weevil densities on T. recurvata between early and late dry seasons were not significantly different, suggesting that dry season survival was relatively high. Weevils collected during these seasons revealed little reproductive development and relatively high-fat accumulation in both sexes. During 5 of 6 yr, densities of the weevils in T. recurvata dropped significantly during the early rainy seasons, when the reproductive host trees leafed out and began producing oviposition sites (flower buds). At this time, more males than females initially moved to vegetative trees and showed significant signs of reproductive development. Recolonization of ball moss by weevils began during the late rainy season when oviposition sites (flower buds) were still available. A proportion of the weevils remained on the reproductive host, suggesting that A. rufipennis is facultatively multivoltine. The methodologies and results of the study can serve as a model system for future studies of the dormancy of other insects in dry tropical forests and provide insight into the dormancy of other anthonomine weevils of economic importance.

Impact of Different Food Sources on the Developmental Biology and Host Preferences of the Red Flour Beetle Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

An experiment conducted at the seed center laboratory at Tamil Nadu Agricultural University during June 2022 evaluated the host preferences and developmental biology of the red flour beetle (Tribolium castaneum) across three food sources: broken rice with rice flour, broken wheat with wheat flour, and tapioca flour. Beetle development was observed in ventilated containers under controlled conditions (28-30°C, 65% relative humidity) with 25 beetles per container. Significant differences in beetle survival and development. Wheat flour was the most favourable host, with 304 live adults, followed by broken wheat (145 live adults. Rice flour supported 20 adults and 11 larvae, indicating moderate suitability. Whole rice grains and tapioca flour were the least effective, with only dead adults and few larvae. Despite host quality variations, the developmental stages (egg incubation: 4-7 days, larval: 65-70 days, pupal: 6-9 days) were consistent across food sources. Wheat flour is the most supportive environment for T. castaneum development.

Lithological Control to the Gold Mineralization in the Main Ridge Complex of the Bakan Gold District, Northern Sulawesi, Indonesia

Abstract Main Ridge complex is characterized by prominent high sulfidation epithermal-style mineralization with windows of porphyry style mineralization in the deeper zone. Several lithologic features play important controlling role in the occurrences of those mineralization. The oldest rock observed in the Main Ridge complex is unmineralized hornblende diorite (IDO-1) which encompasses the whole Bakan district. Several late intrusive stocks were concealed below the current topographic as mentioned as the microdiorite (IDO-2) and quartz diorite (IDO-3) in which the latter exhibits windows of porphyry-style mineralization. Those intrusive units were then covered by two unconformable volcanic tuff sequences which are andesitic tuff and dacitic tuff in compositions. Dacitic tuff is more favourable unit for gold mineralization compared to andesitic tuff which shown by near-surface ‘mushroom-like’ deposit form. In more peripheral area, the mineralization is also controlled by the bedding features of dacitic tuff which underlain by the less-mineralized andesitic tuff. In the latest stage, diatreme breccia cut all the lithologic units and becomes the most favourable host rock in sub-vertical deposit form. The comprehensive understanding of the lithological features is important to understand the mineralization control for further exploration target.

Oral Myiasis: Case Report of a rare entity!

Background: Floods and severe rainfall are major reasons for the increase in infections like Dengue, malaria, and other parasitic infections. There may be an increase in worm infestations in the immediate post-flood period due to moist conditions. Oral myiasis is one of those rare parasitic infestations that may occur during such events and can be life-threatening to the patient due to its destructive nature. The chances become high if the patient has any underlying condition that can act as a reservoir or favourable host for such infestations. Immediate management of the disease increases the chances of a good prognosis and spread of the disease. Oral Myiasis is still a rare condition caused by larvae of flies called maggots. The following case report is an attempt to highlight the timely recognition of the disease which came to a private clinic with a routine complaint of toothache and its early management led to the complete recovery of the lesion and the patient.

Comparison of gut transcriptome and bacterial composition of the yellow peach moth, Conogethes punctiferalis larvae associated with host plants adaptation

The yellow peach moth, Conogethes punctiferalis, is one of the most destructive polyphagous pests to corn crops in the Huang-Huai-Hai summer corn region of China. However, little is known about the host plant adaptation mechanism of C. punctiferalis. In this study, we analyzed the performance of C. punctiferalis on two of its favorable host plants (corn and sorghum). Then, we used RNA-seq and 16S rRNA sequencing to explore the potential adaptation mechanism of C. punctiferalis on these two host plants. Results showed that C. punctiferalis gained more fresh weight on sorghum while its total lipid and triglyceride content was significantly lower than on corn. In total, 2155 genes weredifferentially expressed (DEGs) between corn and sorghum reared C. punctiferalis. Most of the DEGs were involved in nutritional biosynthesis and metabolism including amino acid biosynthesis, protein digestion and absorption, and glycolysis. Enzymatic analyses revealed that C. punctiferalis reared on corn had higher trypsin activity but lower P450 activity than that reared on sorghum. Meanwhile, C. punctiferalis reared on corn harbored more gut bacteria, while its diversity is lower than that reared on sorghum. The potential functional prediction of the gut bacteria revealed that nutritional metabolism functions were differently enriched between two host plants of C. punctiferalis. Taken together, these findings clarify the impact of host plants on the gene expression and gut bacteria in C. punctiferalis. They also suggest that the plasticity of gene expression and gut bacteria cooperatively contribute to insect host adaptation of insects.

Progressive Optimization of Lanthanide Nanoparticle Scintillators for Enhanced Triple-Activated Radioluminescence Imaging.

Lanthanide nanoparticle (LnNP) scintillators exhibit huge potential in achieving radionuclide-activated luminescence (radioluminescence, RL). However, their structure-activity relationship remains largely unexplored. Herein, progressive optimization of LnNP scintillators is presented to unveil their structure-dependent RL property and enhance their RL output efficiency. Benefiting from the favorable host matrix and the luminescence-protective effect of core-shell engineering, NaGdF4 : 15 %Eu@NaLuF4 nanoparticle scintillators with tailored structures emerged as the top candidates. Living imaging experiments based on optimal LnNP scintillators validated the feasibility of laser-free continuous RL activated by clinical radiopharmaceuticals for tumor multiplex visualization. This research provides unprecedented insights into the rational design of LnNP scintillators, which would enable efficient energy conversion from Cerenkov luminescence, γ-radiation, and β-electrons into visible photon signals, thus establishing a robust nanotechnology-aided approach for tumor-directed radio-phototheranostics.

Progressive Optimization of Lanthanide Nanoparticle Scintillators for Enhanced Triple‐Activated Radioluminescence Imaging

AbstractLanthanide nanoparticle (LnNP) scintillators exhibit huge potential in achieving radionuclide‐activated luminescence (radioluminescence, RL). However, their structure–activity relationship remains largely unexplored. Herein, progressive optimization of LnNP scintillators is presented to unveil their structure‐dependent RL property and enhance their RL output efficiency. Benefiting from the favorable host matrix and the luminescence‐protective effect of core–shell engineering, NaGdF4 : 15 %Eu@NaLuF4 nanoparticle scintillators with tailored structures emerged as the top candidates. Living imaging experiments based on optimal LnNP scintillators validated the feasibility of laser‐free continuous RL activated by clinical radiopharmaceuticals for tumor multiplex visualization. This research provides unprecedented insights into the rational design of LnNP scintillators, which would enable efficient energy conversion from Cerenkov luminescence, γ‐radiation, and β‐electrons into visible photon signals, thus establishing a robust nanotechnology‐aided approach for tumor‐directed radio‐phototheranostics.

Active targeting tumor therapy using host-guest drug delivery system based on biotin functionalized azocalix[4]arene

Host-guest drug delivery systems (HGDDSs) provided a facile method for incorporating biomedical functions, including efficient drug-loading, passive targeting, and controlled drug release. However, developing HGDDSs with active targeting is hindered by the difficult functionalization of popular macrocycles. Herein, we report an active targeting HGDDS based on biotin-modified sulfonated azocalix[4]arene (Biotin-SAC4A) to efficiently deliver drug into cancer cells for improving anti-tumor effect. Biotin-SAC4A was synthesized by amide condensation and azo coupling. Biotin-SAC4A demonstrated hypoxia responsive targeting and active targeting through azo and biotin groups, respectively. DOX@Biotin-SAC4A, which was prepared by loading doxorubicin (DOX) in Biotin-SAC4A, was evaluated for tumor targeting and therapy in vitro and in vivo. DOX@Biotin-SAC4A formulation effectively killed cancer cells in vitro and more efficiently delivered DOX to the lesion than the similar formulation without active targeting. Therefore, DOX@Biotin-SAC4A significantly improved the in vivo anti-tumor effect of free DOX. The facilely prepared Biotin-SAC4A offers strong DOX complexation, active targeting, and hypoxia-triggered release, providing a favorable host for effective breast cancer chemotherapy in HGDDSs. Moreover, Biotin-SAC4A also has potential to deliver agents for other therapeutic modalities and diseases.

Two-Year Preclinical Evaluation of Long-Term Absorbable Poly-4-hydroxybutyrate Scaffold for Surgical Correction of Pelvic Organ Prolapse

Introduction and hypothesisFully absorbable implants may be an alternative to permanent meshes in the correction pf pelvic organ prolapse (POP) as they may reduce adverse events by promoting tissue regeneration and collagen metabolism. This study was aimed at evaluating the long-term host and biomechanical response to a fully absorbable poly-4-hydroxybutyrate (P4HB) scaffold in comparison with polypropylene (PP) mesh.MethodsPoly-4-hydroxybutyrate scaffold (n = 16) and PP mesh (n = 16) were surgically implanted in the posterior vaginal wall of parous female Dohne Merino sheep. Vaginal explants were evaluated in terms of gross necropsy, host response (immune response, collagen deposition, tissue regeneration), biomechanics, and degradation of P4HB at 12 and 24 months post-implantation.ResultsGross necropsy revealed no infection or fluid collection using P4HB or PP. At 12 months, exposures were observed with both P4HB (3 out of 8) and PP (4 out of 8), whereas at 24 months, exposures were observed only with PP (4 out of 8). The tensile stiffness of the P4HB explants was maintained over time despite complete absorption of P4HB. The collagen amount of the vaginal tissue after P4HB implantation increased over time and was significantly higher than PP at 24 months. P4HB scaffolds exhibited significantly lower myofibroblast differentiation than PP meshes at 24 months.ConclusionsThe P4HB scaffold allowed for gradual load transfer to the vaginal wall and resulted in mechanically self-sufficient tissue. P4HB scaffold had a more favorable host response than PP mesh, with higher collagen content, lower myofibroblastic differentiation, and no exposures at 24 months. P4HB scaffolds have potential as an alternative to permanent implants in treating POP.

Morphological, Structural and Optical Properties of Er3+-Doped SiO2-TiO2 Nanofiber

Morphological, Structural and Optical Properties of Er3+-Doped SiO2-TiO2 Nanofiber

Self-consistent modeling of metastable helium exoplanet transits

Absorption of stellar X-ray and extreme ultraviolet (EUV) radiation in the upper atmosphere of close-in exoplanets can give rise to hydrodynamic outflows, which may lead to the gradual shedding of their primordial light element envelopes. Excess absorption by neutral helium atoms in the metastable 2 3S state [He I(2 3S)], at ~10 830 Å, has recently emerged as a viable diagnostic of atmospheric escape. Here we present a public add-on module to the 1D photoionization hydrodynamic code ATES, designed to calculate the He I(2 3S) transmission probability for a broad range of planetary parameters. By relaxing the isothermal outflow assumption, the code enables a self-consistent assessment of the He I(2 3S) absorption depth along with the atmospheric mass-loss rate and the outflow temperature profile, which strongly affects the recombination rate of He II into He I(2 3S). We investigate how the transit signal can be expected to depend upon known system parameters, including host spectral type, orbital distance, and planet gravity. At variance with previous studies, which identified K-type stars as favorable hosts, we conclude that late M dwarfs with Neptune-sized planets orbiting at ~0.05–0.1 AU can be expected to yield the strongest transit signal, well in excess of 30% for near-cosmological He-to-H abundances. More generally, we show that the physics that regulates the population and depletion of the metastable state, combined with geometrical effects, can yield somewhat counterintuitive results, such as a nonmonotonic dependence of the transit depth on orbital distance. These are compounded by a strong degeneracy between the stellar EUV flux intensity and the atmospheric He-to-H abundance, both of which are highly uncertain. Compared with spectroscopy data, now available for over 40 systems, our modeling suggests either that a large fraction of the targets have helium-depleted envelopes or that the input stellar EUV spectra are systematically overestimated. The updated code and transmission probability module are available publicly as an online repository.