Human Herpesvirus 8: Infection, Transmission & Diseases

Human herpesvirus 8 (HHV 8) is a virus in the Herpesviridae family. It belongs to the subgroup of gammaherpesviruses. It was discovered in 1994 by virologist Patrick S. Moore and his wife Yuan Chang at Coulumbia University in New York. In addition to Kaposi’s sarcoma, human herpesvirus 8 causes rare malignant lymphomas.

What is human herpesvirus 8?

Human herpesvirus 8 belongs to the order Herpesvirales, the family Herpesviridae, the subfamily Gammaherpesvirinae, and the genus Rhadinoviruses. Human herpesvirus 8 is the only human rhadinovirus known to date. It causes Kaposi’s sarcoma and rare malignant lymphomas.

Occurrence, distribution, and characteristics

The history of the discovery of the virus includes the fact that it had been noticed since the 1980s that certain malignancies were occurring more frequently in AIDS patients. This was particularly noticeable in Kaposi’s sarcoma, which was an extremely rare tumor of the skin before the HIV pandemic occurred. Furthermore, it was striking that Kaposi’s sarcoma occurred more frequently in male than in female AIDS patients. This observation led to the assumption that Kaposi’s sarcoma must have an infectious cause. Furthermore, it could be hypothesized that the pathogen can be transmitted through sex, spread through HIV-related immune deficiency, and ultimately cause Kaposi’s sarcoma. This hypothesis was tested by scientists Moore and Chang. When the DNA sections of the viruses found were examined, it became clear that this was a previously undiscovered virus. This human herpesvirus is rare compared to the high rates of transmission of the other human herpesviruses. In North America and Europe, 1-3% of the population has antibodies to HHV-8. In equatorial Africa, however, the rate is approximately 50%. In contrast, the seroprevalence of other human herpesviruses is well over 50% worldwide. Detection is serological by demonstrating the presence of antibodies to the virus. The virus is transmitted via saliva and other body fluids. A distinction is made between sexual and asexual transmission routes. In the sexual routes of infection, oro-genital, oro-anal, and oro-oral transmission are possible. In the asexual route, the herpes virus can be transmitted through saliva contact. Thus, transmission or infection occurs by the same route as other human herpesviruses.

Diseases and symptoms

Human herpesvirus 8 causes Kaposi’s sarcoma and can also lead to rare malignant lymphomas. Certain forms of Castleman’s disease can also be triggered by human herpesvirus 8. The diseases mentioned do not occur in every person infected with HHV-8. Occurrence is only likely if certain cofactors (e.g. immunodeficiency) are present. Kaposi’s sarcoma is a cancer of the (mucous) skin that occurs mainly in AIDS patients. Presumably, the presence of human herpesvirus 8 and cofactors (including immunodeficiency) are necessary for its development. Furthermore, the cofactors probably include environmental factors as well as oxidative and nitrosative stress. The symptoms of the disease consist in the appearance of brown-bluish tumor nodules on the mucous membranes and in the intestine, and in AIDS patients usually also on the skin. Men are generally more frequently affected than women. The disease is often chronic. It is possible for metastases to occur in various organs and/or the lymph nodes. Rarely, direct involvement of the lymph nodes is also possible. There is also an increased risk of disease after organ transplantation, as immunosuppressive drugs are used in this case. In the therapy of Kaposi’s sarcoma, it is most important to maintain the function of the immune system. For this reason, combination antiviral therapy is of utmost importance in HIV and AIDS patients. Furthermore, various therapeutic procedures such as surgical removal of the affected tissue, radiation therapy, physical therapy and laser therapy are used. Chemotherapy is also used to treat Kaposi’s sarcoma. In addition, experimental therapies are available, but their mode of action is more unpredictable than that of long-established therapies.Together with the following viruses, human herpesvirus 8 forms the group of human carcinogenic viruses: hepatitis B virus, hepatitis C virus, human papilloma virus, Epstein-Barr virus, human T-lymphotropic virus 1. These viruses can cause cancer in humans and are responsible for approximately 10 to 15% of all cancers worldwide. Strikingly, HHV-8 contains many genes that have a high degree of homology to the genes of human cells. This homology can influence the behavior of human cells in complex ways. In all likelihood, this is the reason for its carcinogenicity.