The adaptability of marine organisms to changes in salinity has been a significant research area under global climate change. However, the underlying mechanisms of this adaptability remain a debated subject. We hypothesize that neglecting salinity fluctuation properties is a key contributing factor to the controversy. The ciliate Euplotes vannus was used as the model organism, with two salinity fluctuation period sets: acute (24 h) and chronic (336 h). We examined its population growth dynamics and energy metabolism parameters following exposure to salinity levels from 15‰ to 50‰. The carrying capacity (K) decreased with increasing salinity under both acute and chronic stresses. The intrinsic growth rate (r) decreased with increasing salinity under acute stress. Under chronic stress, the r initially increased with stress intensity before decreasing when salinity exceeded 40‰. Overall, glycogen and lipid content decreased with stress increasing and were significantly higher in the acute stress set compared to the chronic one. Both hypotonic and hypertonic stresses enhanced the activities of metabolic enzymes. A trade-off between survival and reproduction was observed, prioritizing survival under acute stress. Under chronic stress, the weight on reproduction increased in significance. In conclusion, the tested ciliates adopted an r-strategy in response to salinity stress. The trade-off between reproduction and survival is a significant biological response mechanism varying with salinity fluctuation properties.

Considering the absence of a widely utilized EBV vaccine, we have developed an EBV gL-gH344-Ferritin nanoparticle vaccine utilizing ferritin as a carrier. The gL-gH344-Ferritin fusion gene was synthesized and inserted into the pET30a plasmid. The expression of the fusion protein in the recombinant plasmid was verified by Western blot. Then, the gL-gH344-Ferritin subunit nanoparticle vaccine was obtained by purification of the fusion protein. BALB/c mice were immunized using a two-dose protocol. The titers of EBV specific antibodies were determined using enzyme-linked immunosorbent assay at 4, 8, and 12 weeks after the initial immunization. Moreover, the levels of EBV gL-gH344 specific splenocytes secreting interferon (IFN)-γ and interleukin (IL)-6 were determined using an enzyme-linked immunospot assay. The pET30a-gL-gH344-Ferritin prokaryotic expression plasmid was successfully constructed. gL-gH344-Ferritin was efficiently expressed in E. coli. Following immunization with gL-gH344-Ferritin, the mice sera demonstrated elevated titers of EBV specific immunoglobulin G. Moreover, after stimulating with EBV gL-gH344 specific peptides, the splenocytes of the immunized mice showed a marked tendency to secrete large amounts of IFN-γ and IL-6. The gL-gH344-Ferritin nanoparticle vaccine carrying the EBV gL-gH344 fusion protein induced robust and sustained specific humoral and cellular immune responses in mice.