Exosomes are a type of extracellular vesicles (EVs) released by cells under normal and pathological conditions. These lipid-enclosed vesicles play a key role in intracellular communication by delivering various molecules, such as proteins, nucleic acids, and lipids, thereby influencing the activity of recipient cells. In recent years, exosomes have attracted considerable attention for their involvement in viral infections and immune system evasion. Many viruses hijack the exosome biogenesis machinery to facilitate their replication, spread infection, and evade immune defenses. Therefore, gaining insights into how exosomes modulate the immune system or contribute to viral infectivity is crucial. This review explores how viral exosomes interact with host mammalian cells, highlighting their unique ability to transfer genetic material and proteins to recipient cells independent of virus-receptor interaction. Additionally, we examine the role of viral exosomes in intercellular communication, particularly how they may both promote viral infectivity and transmission, as well as participate in antiviral defense and immune regulation. Unlike previous reviews, our study integrates findings across both human and animal viral infections, critically discusses methodological standardization in exosome research, and introduces emerging therapeutic approaches such as engineered exosomes and exosome mimetics.

Background/Objectives. One of the pressing challenges in global public health is the rise in infections caused by carbapenem-resistant Enterobacteriaceae. Growing bacterial drug resistance, coupled with the slow development of new antibiotics, highlights the critical need to explore and develop new broad-spectrum antimicrobial agents able to inhibit bacterial growth efficiently. In recent years, antimicrobial peptides (AMPs) have gained significant attention as a promising alternative to conventional drugs, owing to their antimicrobial potency, low toxicity, and reduced propensity for fostering resistance. Our research aims to investigate the antibacterial ability of three amphibian AMPs, namely Hylin-a1, AR-23, and RV-23, against both antibiotic-sensitive and carbapenem-resistant strains of Escherichia coli and Klebsiella pneumoniae. Methods. A 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT) was performed to identify non-cytotoxic concentrations of peptides. A microdilution assay evaluated the antibacterial effect, determining the peptides’ minimum inhibitory concentration (MIC). In addition, the checkerboard test analyzed the compounds’ synergistic effect with meropenem. Results. We demonstrated that peptides with low toxicity profile and resistance to proteolytic activity exhibited strong antibacterial activity, with MIC ranging from 6.25 to 25 μM. The antibiofilm mechanism of action of peptides was also investigated, suggesting that they had a crucial role during the biofilm formation step by inhibiting it. Finally, we highlighted the synergistic effects of peptides with meropenem. Conclusions. Our study identifies Hylin-a1, AR-23, and RV-23 as promising candidates against Gram-negative bacterial infections with a favorable therapeutic profile. This effect could be related to their great flexibility, as evidenced by circular dichroism data, confirming that the peptides could assume an α-helical conformation interacting with bacterial membranes.