Precise biophysical characterization of non-enveloped viruses and virus-like particles (VLPs) is essential for evaluating assembly, structural integrity, and sample heterogeneity — key parameters that influence infectivity, manufacturability, and therapeutic performance. Analytical ultracentrifugation, light scattering, and mass photometry provide complementary information on particle size distributions, empty/full ratios, and assembly quality. Native and charge-detection mass spectrometry extend this, enabling accurate mass determination and genome-loading assessment. Solution-based structural techniques, such as SAXS and spectroscopy, provide dynamics. High-resolution X-ray crystallography, cryogenic electron microscopy, and tomography reveal global architectures, quaternary arrangements, and conformational switching essential for entry and maturation. Besides these methods, atomic force microscopy also allows nanoscale visualization in conjunction with mechanical profiling, linking physical stability with functional behavior. Thermal, chemical, and mechanical stress assays offer insight into unfolding pathways, pH-dependent disassembly, and genome-driven capsid pressurization, informing both viral biology and formulation science. Finally, mass spectrometry-based methods enable site-specific mapping of post-translational modifications and conformational perturbations. Together, these approaches establish a comprehensive framework for characterizing viral particles and VLPs, supporting rational engineering of stable, homogeneous, and functional assemblies for vaccines, gene delivery, and nanobiotechnology. This review summarizes current label-free methods for assessing size, mass, structural organization, and stability of intact viral particles.
Non-circulative transmission of plant viruses relies on rapid and reversible interactions between virions and their vectors, occurring either in the stylets or in the foregut. Stylet-borne viruses are retained in aphid stylets at the surface of the cuticle, especially on the acrostyle, an acellular specialized structure at the distal tip of maxillary stylets. Recent studies have identified a small set of cuticular proteins, called stylins, with domains directly exposed at the virus-acrostyle interface, thus potentially contributing to virus binding. The acrostyle was also shown to retain the salivary effector Mp10, likely via Stylin-03, suggesting that stylins mediate the retention of important molecules for successful aphid feeding. Several stylins are exploited by viruses across diverse genera for transmission. In particular, functional studies using RNAi-mediated gene knockdown and CRISPR-Cas9 mutagenesis in aphids demonstrated that Stylin-01 is required for efficient transmission of both cauliflower mosaic virus and turnip mosaic virus, with Stylin-04/04bis further contributing to the latter. The observation of residual transmission after disrupting individual stylins suggests functional redundancy within the acrostyle. This review highlights stylins as core components of the aphid stylet cuticular acellular interaction platform that enable non-circulative virus transmission.
Hepatitis E virus (HEV) of the species Paslahepevirus balayani is a leading cause of acute viral hepatitis worldwide. Four HEV genotypes frequently infect humans but differ in their geographical distribution, routes of transmission, host range, clinical manifestations, and pathogenesis. HEV genotype 1 (HEV-1), endemic in many low- and middle-income countries, is predominantly transmitted via the fecal-oral route through contaminated water and is associated with severe disease during pregnancy, resulting in high maternal morbidity and mortality. Despite its public health importance, our understanding of the HEV-1 replication cycle and genotype-specific determinants of pathogenicity remains limited. A key bottleneck in the field is the availability of robust, reproducible in vitro and in vivo model systems that accurately recapitulate HEV-1 infection. In this review, we summarize recent advances in the development of HEV-1 model systems and describe available in vitro and in vivo systems. We also outline remaining gaps and potential directions for model refinement that may facilitate future HEV-1 research.
Orthoflaviviruses, including dengue virus, tick-borne encephalitis virus, West Nile virus, Zika virus, Japanese encephalitis virus, and yellow fever virus, cause a wide spectrum of diseases in humans despite sharing a similar genomic organization. These viruses pose a growing global threat as they are spreading widely, treatment options remain limited, and both climate change and expanding mosquito populations increase the risk of outbreaks worldwide. This review summarizes the determinants of their human tropism, the capacity to infect specific cell types, tissues, and organs. We synthesized current knowledge on how viral factors, including host factor utilization and immune cell trafficking, shape tropism across multiple layers. Central to this process are sequential host barriers that govern infection, including viral attachment, internalization, and replication. Understanding these determinants is essential for informing strategies to mitigate the global burden of these medically important pathogens.
Pathogens depend heavily on their hosts, a relationship driven by molecular interactions. Among the diverse molecular classes involved, proteins and protein–protein interactions (PPIs) serve as the pillars of these infectious processes. Driven by opposing natural selection pressures, with one protein adapting to escape the interaction and the other adapting to maintain it, host and pathogen proteins coevolve in this arms race. With the advent of artificial intelligence-driven structural prediction methods, initiated by AlphaFold, highly accurate structural modeling of PPIs has become feasible. Yet, host–pathogen PPIs remain difficult to model with these approaches. In this review, we describe the current state of host–pathogen structural modeling, describe recent studies, and discuss how pushing current methods to their limits might improve success rates.
