Construction Of HSV-1 Mutant Strains And Analysis Of Their Biological Characteristics And Immunogenicity

Human herpesvirus is a family of DNA virus including eight members,with a high rate of infection in the world.Especially,HSV-1 and HSV-2 infection which can cause oral blisters,genital herpes diseases or herpes simplex encephalitis,have become the important infectious diseases in the youth population and widespread concern of public health.Therefore,the studies of the clinical treatment and prophylactic products related to these pathogens have been promoted in many aspects.To date,despite the use of acyclovir drugs in clinical practice,none clinical trials of HSV-1 and HSV-2 vaccine candidates has provided meaningful results.It is an important research direction to explore the appropriate vaccine form which can induce effective clinical protection efficiency based on the pathogenic characterisitcs of HSV-1 and HSV-2.Our previous work focusing on the molecular mechanism of interplay between HSV-1 and the host and the method of mutant construction,has provided the preliminary data for further investigating the function of tegument proteins in biological characteristics and virulence phenotype determination of HSV-1.Thus,the present study primarily describes the effect of tegument protein UL7 on the HSV-1 virulence phenotype through transcriptional regulation,and its possible mechanism.Based on the biological characteristics of this mutant strain,mutant strains M2 and M3 modified with regulatory molecule Vhs encoding gene u141 and LAT genes that related to latency establishment and maintained were constructed as well,while the biological characteristics and pathogenicity of the mutant strains were studied.Finally,we evaluated the immunogenicity of the M3 strain to provide a preliminary basis for the study of HSV-1 attenuated virus.In the first part of this work,we found that the viral replication capacity in cells and neurovirulence in infected mice of the M1 strain were attenuated compared with the wild type strain.Furthermore,the results from the experiment in vitro showed UL7 may be involved in transcriptional regulation of a-4 gene during HSV-1 infection by participating in chromatinization process of a-4 gene.In the second part of this work,pathological analysis results suggested that these mutants,especially M3 showed attenuated phenotypes with a lower proliferative ratio in various cells,non-lethal infection in mice,a lower viral load in nervous tissues,compared with the wild-type strain.Based on these results,we further immunized the mice with M3 mutant strain,followed by challenging with wild type viruses via nasal infection after 1 or 2 months post immunization.Compared with control groups,mice immunized with M3 mutant strain were observed that it could trigger specific immune responses including the production of neutralizing antibody and the activation of CD8+T cell,with significantly reduced viral load and pathological damage in various mice organs,ameliorated clinical symptoms and restricted latent infection.In conclusion,these findings indicated that M3 mutant strain was an attenuated phenotype of HSV-1 and this attenuated strain might be as a potential candidate for further study of HSV-1 vaccine.