Establishment Of A Model For Herpes Simplex Virus 1 Infection In Rhesus Monkey And Study On Its Pathogenicity

Herpes simplex virus type I (herpes simplex virus type 1, HSV-1) is one of the most prevalent infectious viruses in human. The main charateristic of HSV-1 is to establish latent infection for the lifetime in the infected host and periodically recurrent. Thus, the diseases and complications caused by HSV-1 are difficultly controlled for many years. Study on the pathogenic feature and pathogenesis of HSV-1 became the pivot of clinical epidemic and prevention of HSV-1. HSV-1 infections in humans are difficult to study in many cases because many primary infections are asymptomatic and the neurotropic properties of HSV-1. Therefore, establishing appropriate study carrier-animal model is the main content of this research work.For a long time, animal model is an indispensable tool in studying various diseases in human. The development of animal model promotes the progress of medical biology research. Establishing appropriate animal model has become the major requirements and hot spot of biological sciences research. The previous research work showed that none-human primates are ideal experimental animals for human disease pathogenesis, drug treatment and vaccine development, and has been widely used in studying various infection disease in human since they are closest to human beings on evolutionary relationships. However, the HSV-1 infected primate animal models have not been established so far.Based on advantage of primate animal models in human infectious diseases in the past, in our study, we simulated the process of natural human infection with HSV-1 by infecting rhesus monkeys with 103 CCID50/ml of HSV-1-8F strains through oral mucosal epithelium and corneal epithelium to compare the pathogenic characteristics of rhesus monkeys between the two inoculation methods. Following primary infection, the clinical features of acute infection, body temperature, blood routine index, changes of lymphocyte and serum neutralizing antibody titer were monitored. Quantitative real-time polymerase chain reaction was used to detect virus load in eyes, nose, mouth, urine, anal swab, blood, different tissues and organs to study the virus distribution in the monkeys. The pathological changes in cold sores and neuronal tissue were examined, and HSV-1 antigen in cold sores and neuronal tissue were further detected by using immunohistochemical technique. The result showed that the primary infection of HSV-1 can cause raise in body temperature and clinical symptoms such as oral herpes. Compared those rhesus monkey with corneal scarification, the rhesus monkeys infected through the oral epithelium clinically manifested earlier and more severe. Blood routine test results showed that proportion of monocyte in peripheral blood rise significantly, higher than normal amounts, and the proportion of other blood cells were changed within the normal range. The viral loads detected by Quantitative Real-time PCR in eyes, nose, mouth, urine, anal swabs and the in blood from 1 to 10 days of postinfection showed that the secretions from these sites can sensitively show the change of the viral load. In addition, viral DNA in blood rose significantly at 6 days of postinfection. The viral loads of the swabs and blood were closely associated with the appearance of clinical symptoms. The results of the virus distribution in organs and tissues showed that the virus DNA can be detected in neuronal tissues, lymphatic tissues and other tissues in the infected rhesus monkeys, and that the inoculation method can affect the virus distribution in the rhesus monkey body. The pathological and histological results in neuronal tissues and oral herpes showed that HSV-1 can cause serious oral herpes skin lesions. However, obvious pathological changes in CNS were not observed. At the same time, HSV-1 can be detected in the central nervous tissue by immunohistochemical techniques. The long-term observation from six months to one year showed that the monkeys can appear manifestations similar to latent infection and recurrence of infection in the clinical symptoms, and the virus can be detected in the secretion swabs from the infected monkeys by PCR. Clinical observation indicated that the latent HSV-1 in rhesus monkeys can be activated under certain conditions and results in recrudescent oral lesions. The explant co-cultivation experiment by co-culturing the nerve tissue from the infected rhesus monkeys with HSV-1 to activate the virus confirmed that the virus exists in the trigeminal ganglion and pons, and the latent virus can be activated through co-culturing the homogenizing tissue with foreign cells in vitro. In addition, transcriptome analyses were performed using RNA sequencing technology to analyze the transcripts in the peripheral blood lymphocytes from the rhesus monkeys in 0,4,8,12,60,150 days of postinfection respectively and to compare the change of the transcripts between the monkeys. The results showed that the expression of 52 genes exists significant differences between the monkeys after infection, and the differential genes are involved in immune system, cellular processes, cell communication, regulation of transcription and regulation of transduction. The results indicated that HSV-1 activated rhesus monkey’s immune system after infection, resulting in changes of immune factors cytokines and chemokines in blood.The results implied that a pathological process of rhesus monkeys infected with HSV-1 which can act as an effective animal model of HSV-1 infection. The Rhesus monkey model not only manifested oral herpes in pathological process of primary infection, but showed the existence of the latent HSV-1 in some organs and tissues for long time and recurrent infection under certain conditions. In this sense, it is possible to use rhesus monkeys infected with HSV-1 as model in studying the infection biology of HSV-1.