Human herpes simplex virus (HSV), a double-stranded DNA virus belonging to the Herpesviridae family and alpha herpesvirus subfamily, is one of the most epidemic pathogens in the population. Cell-to-cell spread is a special intercellular transmission mechanism of HSV that indicates the virulence of this virus. Through numerous studies on mutant HSV strains, many viral and host proteins involved in this process have been identified; however, the mechanisms remain poorly understood. Here, we evaluated the effect of the membrane protein genes US7 and UL56 on cell-to-cell spread in vitro between two HSV-1 (HB94 and HN19) strains using a plaque assay, syncytium formation assay, and the CRISPR/Cas9 technique. US7 knockout resulted in the inhibition of viral cell-to-cell spread; additionally, glycoprotein I (US7) of the HB94 strain was found to promote cell-to-cell spread compared to that of the HN19 strain. UL56 knockout did not affect plaque size and syncytium formation; however, the gene product of UL56 from the HN19 strain inhibited plaque formation and membrane infusion. This study presents preliminary evidence of the functions of US7 and UL56 in the cell-to-cell spread of HSV-1, which will provide important clues to reveal the mechanisms of cell-to-cell spread, and contributes to the clinical drugs development.

Background: The global burden of tick-borne viral diseases (TBVDs) has significantly increased in recent decades, emerging as a critical public health priority due to their diverse pathogenic profiles, severe disease outcomes, and therapeutic challenges. Within the expanding landscape of tick-borne pathogens, the Orthonairovirus genus has gained particular scientific attention for its members’ zoonotic capacity and clinical virulence . Orthonairoviruses are arboviruses that infect humans and animals, posing a serious threat for the spread of zoonotic diseases. Huangpi tick virus 1 (HpTV-1), a member of the genus Orthonairovirus , has been detected in ticks. Methods: Haemaphysalis longicornis collected in 2023 from Central China were pooled for RNA-seq and reverse transcription quantitative polymerase chain reaction (RT-qPCR) screening. Genomes were assembled and viruses isolated in suckling mice and Vero E6. Replication kinetics, mouse pathogenesis, and 223 livestock sera were assessed. Results: In the present study, we isolated HpTV-1 from Haemaphysalis longicornis in Central China. Viral genome and phylogenetic analyses placed HpTV-1 in a distinct clade close to the Songling and Tamdy viruses within the Nairoviridae family. In vitro experiments demonstrated that HpTV-1 infects a wide range of animal and human cell lines. Importantly, all infected C57BL/6 mice survived without overt signs of severe disease while developing only minor pathological lesions in specific organs (liver, spleen, and lungs). Serological surveys revealed HpTV-1 antibodies, including neutralizing antibodies, in 16.1% of the goats, suggesting that HpTV-1 can infect livestock. Conclusions: These findings suggest that HpTV-1 is an Orthonairovirus capable of infecting animals, highlighting its potential risk and the need for enhanced surveillance and research, particularly in Central China and other endemic regions. Graphical