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Abstract Under the dual pressure of emerging zoonoses and the difficulty in eliminating conventional zoonoses, the strategic management of bird diseases through vaccination represents a highly efficacious approach to disrupting the transmission of zoonotic pathogens to humans. Immunization with a DNA vaccine yielded limited protection against avian pathogen infection. To improve its immunogenicity, the extracellular domain of duck-derived CD40L (designated as dusCD40L) was employed as a bio-adjuvant. Our findings unequivocally established the evolutionary conservation of dusCD40L across avian species. Notably, dusCD40L exhibited a compelling capacity to elicit robust immune responses from both B and T lymphocytes. Furthermore, when employed as an adjuvant, dusCD40L demonstrated a remarkable capacity to significantly augment the titers of neutralizing antibodies and the production of IFNγ elicited by a DNA vaccine encoding the prM-E region of an avian flavivirus, namely, the Tembusu virus (TMUV). Moreover, dusCD40L could strengthen virus clearance of the prM-E DNA vaccine in ducks post-TMUV challenge. This research study presents a highly effective adjuvant for advancing the development of DNA vaccines targeting TMUV in avian hosts. Additionally, it underscores the pivotal role of duCD40L as a potent adjuvant in the context of vaccines designed to combat zoonotic infections in avian species.

ABSTRACT: Tembusu virus (TMUV), an avian pathogenic flavivirus, has emerged as a significant threat to the duck industry in Southeast Asia, causing substantial economic losses. Due to the antibody-dependent enhancement (ADE) effect of TMUV subneutralizing antibodies, there is a pressing need to further develop new TMUV vaccine target antigens that ensure both safety and efficacy. Here, the TMUV non-structural protein 1 (NS1) as a target for development of effective anti-TMUV vaccines was unveiled. The amino acid sequences of TMUV NS1 exhibit a high degree of conservation across different strains (92.63–100%). To investigate the potential of TMUV NS1 as a vaccine target, the TMUV NS1-based plasmids were constructed and identified the C-terminal 30 amino acids residues of TMUV E (EC30) as an effective signal peptide for promoting NS1 expression and secretion. Subsequently, the plasmid pVAX1-EC30-NS1 was employed to immunize ducks, resulting in specific anti-NS1 IgG responses being stimulated, while without inducing anti-TMUV neutralizing antibodies. Furthermore, the cellular immune responses triggered by the TMUV NS1 were evaluated, observing a notable increase in lymphocyte proliferation at 4 wk and 6 wk postinjection with the pVAX1-EC30-NS1. Additionally, there was a significant up-regulation of NS1-specific Il-4 and Ifnγ levels at these time points. Following this, ducks from different groups were challenged with TMUV, and remarkably, those immunized with the NS1 vaccine displayed significantly lower viral copies both at 3 d postinfection (dpi) and 7 dpi (P < 0.05) compared to ducks immunized with the control vector. Notably, the NS1 demonstrated remarkable protection against TMUV challenge without causing severe gross lesions. Collectively, these findings highlighted the impressive immunogenicity and protectivity of the TMUV NS1. Consequently, NS1 holds great promise as a novel antigen target for the development of efficient and safe TMUV vaccines.

Southwest China is the largest concentrated karst landscape distribution area in the world, with dense river networks and abundant hydroelectric resources in the area, which is an important area for the development of hydroelectric power generation in China. To elucidate the impact of karst reservoirs on the carbon cycle of the river system, this work summarizes the research progress of damming in karst watersheds on different forms of carbon transport transformation and the environment in recent years. Through the study of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate inorganic carbon (PIC) and particulate organic carbon (POC) transport and transformation and their control mechanisms in the river-reservoir system in the karst region by spectroscopy, stability and radioisotopes, this work found that the carbon cycle in karst reservoirs exhibits obvious seasonal distribution characteristics, as well as cascade reservoirs, which may further amplify a single reservoir's environmental influence. These results not only contribute to the understanding of the reservoir carbon cycle but also help to explore the "missing" carbon sinks in the river carbon cycle and to more accurately assess the role of karst reservoirs in the global river carbon cycle. In general, karst reservoirs are likely to be more responsive to increased anthropogenic activities than nonkarst reservoirs, which implies that the role of karst reservoirs in the global warming trend needs to be more accurately assessed, and in future research, a systematic characterization of the carbon transport and transformation of different forms from microscopic to macroscopic levels by different analytical tools will more accurately answer this question.

Carbon dioxide (CO _2 ) emissions from aquatic surface to the atmosphere has been recognized as a significant factor contributing to the global carbon budget and environmental change. The influence of river damming on the CO _2 emissions from reservoirs remains poorly constrained. This is hypothetically due to the change of hydraulic retention time (HRT) and thermal stratification intensity of reservoirs (related to the normal water level, NWL). To test this hypothesis, we quantified CO _2 fluxes and related parameters in eight karst reservoirs on the Wujiang River, Southwest China. Our results showed that there was a significant difference in the values of p CO _2 (mean = 3205.7 μ atm, SD = 2183.4 μ atm) and δ ^13 C _CO2 (mean = −18.9‰, SD = 1.6‰) in the cascade reservoirs, suggesting that multiple processes regulate CO _2 production. Moreover, the calculated CO _2 fluxes showed obvious spatiotemporal variations, ranging from −9.0 to 2269.3 mmol m ^−2 d ^−1 , with an average of 260.1 mmol m ^−2 d ^−1 . Interestingly, the CO _2 flux and δ ^13 C _CO2 from reservoirs of this study and other reservoirs around the world had an exponential function with the reservoir effect index ( R _i , HRT/NWL), suggesting the viability of our hypothesis on reservoir CO _2 emission. This empirical function will help to estimate CO _2 emissions from global reservoirs and provide theoretical support for reservoir regulation to mitigate carbon emission.

Mountainous rivers (MRs) are one of the critical systems in transporting dissolved organic carbon (DOC) from terrestrial environments to downstream ecosystems. However, how geographical factors and anthropogenic impacts control the composition and export of DOC in mountainous rivers remains largely unclear. Here, we explore DOC dynamics in three subtropical mountainous catchments (i.e., the Yinjiang, Shiqian, and Yuqing catchments) in southwest China which are highly influenced by anthropogenic activities. Water chemistry, stable and radioactive carbon isotopes of DOC (δ13CDOC and Δ14CDOC) and optical properties (UV absorbance and fluorescence spectra) for river water were employed to assess the biogeochemical processes and controlling factors of DOC. The radiocarbon ages of the DOC in the Yinjiang River varied widely, ranging from 928 years before present to modern. Both allochthonous and autochthonous sources had an important effect on riverine DOC export. Results from carbon isotopes suggested that in-stream processing of POC is also an important source of DOC. DOC in catchments with higher slope gradients and lower annual air temperature was characterized by lower concentration and more aromatic, which was distinct from those with gentle slopes and higher temperature. Variabilities in DOC concentrations and δ13CDOC were also explained by land use, showing that higher DOC concentrations with 13C-depleted characters were observed in urban and agricultural land use areas. Moreover, DOM was less aromatic, less recently produced and had a higher degree of humification in catchments with a higher proportion of urban and agricultural land use area. This research highlights the significance of incorporating geographical controls and anthropogenic impacts into the MRs to better understand their DOC dynamics and quality of dissolved organic matter (DOM). [ABSTRACT FROM AUTHOR]