HOPES

Human Herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV), is a virus that belongs to the Herpesviridae family. It is one of the eight known human herpesviruses and is associated with several diseases, most notably Kaposi's sarcoma, a type of cancer that often affects individuals with compromised immune systems, such as those with HIV/AIDS.

Virology

HHV-8 is a double-stranded DNA virus that is part of the Gammaherpesvirinae subfamily. It is closely related to other gammaherpesviruses, such as Epstein-Barr virus (EBV). The virus has a complex structure, consisting of an icosahedral capsid, a tegument layer, and an envelope derived from the host cell membrane.

Genome

The HHV-8 genome is approximately 165 kilobases in length and encodes for over 80 proteins. These proteins are involved in various functions, including viral replication, immune evasion, and cell transformation. Notably, HHV-8 encodes several homologs of cellular proteins, such as cytokines and chemokines, which play a role in its pathogenicity.

Epidemiology

HHV-8 is not as ubiquitous as other herpesviruses, such as Herpes Simplex Virus (HSV) or Varicella Zoster Virus (VZV). Its prevalence varies significantly by geographic region, with higher rates in sub-Saharan Africa, the Mediterranean, and parts of the Middle East. Transmission of HHV-8 can occur through saliva, sexual contact, and possibly through blood transfusions and organ transplants.

Pathogenesis

HHV-8 is associated with several diseases:

• Kaposi's sarcoma: A vascular tumor that can affect the skin, lymph nodes, and internal organs. It is most commonly seen in individuals with HIV/AIDS.
• Primary effusion lymphoma: A rare type of B-cell lymphoma that occurs in body cavities.
• Multicentric Castleman's disease: A lymphoproliferative disorder that can occur in HHV-8 infected individuals.

The virus establishes latency in B cells, endothelial cells, and other cell types, where it can persist for the lifetime of the host. Reactivation of the virus can occur under conditions of immunosuppression.

Diagnosis

Diagnosis of HHV-8 infection can be challenging due to its latent nature. Serological tests can detect antibodies against HHV-8, while PCR can be used to detect viral DNA in blood or tissue samples. Histological examination of affected tissues, such as skin biopsies in Kaposi's sarcoma, can also aid in diagnosis.

Treatment

There is no specific antiviral treatment for HHV-8. Management of HHV-8-associated diseases often involves treating the underlying immunosuppression, such as initiating antiretroviral therapy in HIV-positive individuals. Chemotherapy, radiation therapy, and surgical interventions may be used to treat Kaposi's sarcoma.

Prevention

Preventive measures include safe sexual practices and screening of blood and organ donors. There is currently no vaccine available for HHV-8.

Also see

• Herpesviridae
• Kaposi's sarcoma
• HIV/AIDS
• Epstein-Barr virus
• Primary effusion lymphoma