Microbiology
Summary
Human herpesvirus 8 (HHV-8), a member of Herpesviridae family, is a double-stranded DNA virus endemic to areas of Africa. Transmission of HHV-8 primarily happens via sexual contact, especially amongst men who have sex with men.
HHV-8 causes Kaposi's sarcoma, an AIDS-defining illness. Kaposi's sarcoma manifests as red to purple patches on the nose, extremities, and mucous membranes due to abnormal blood vessel formation in early-stage mesenchymal cells. This aberrant angiogenesis is a result of HHV-8 triggering the dysregulation of vascular endothelial growth factor (VEGF), which in turn leads to the appearance of Kaposi's sarcoma. In addition to cutaneous lesions, Kaposi's sarcoma can present mucosal lesions, most commonly appearing on the hard palate. B-cells can be infected by HHV-8, resulting primary effusion lymphoma, a type of B-cell lymphoma. Finally, KaposiÕs sarcoma lesions can often be mistaken for the lesions in bacillary angiomatosis caused by Bartonella henselae bacteria, emphasizing the necessity of microscopic examination for definitive diagnosis.
Lesson Outline
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FAQs
HHV-8, also known as Kaposi's sarcoma-associated herpesvirus, is a DNA virus that causes Kaposi's sarcoma. It's often transmitted via sexual contact, which integrates into the host's cells and can cause malignancy when the host's immune system is compromised, such as in AIDS patients.
HHV-8 exploits the immunosuppressed state in individuals, such as AIDS patients, to replicate more easily. The virus carries genes that can promote cell growth and blood vessel formation, including vascular endothelial growth factor. This allows it to induce the proliferation of infected cells and the formation of the distinctive vascular lesions of Kaposi's sarcoma.
Kaposi's sarcoma, which is caused by HHV-8 infection, is considered an AIDS-defining illness. This means that its development in a person infected with HIV is a sign that the individual's disease has progressed to full-blown AIDS. Moreover, HHV-8 itself can be more easily transmitted and cause more severe disease in individuals with HIV due to their compromised immune systems.
Yes, besides Kaposi's Sarcoma, HHV-8 is also associated with two types of lymphomas: primary effusion lymphoma, a type of B-cell lymphoma, and multicentric Castleman's disease, a rare lymphoproliferative disorder. These malignancies primarily occur in people with compromised immune systems, particularly those with HIV/AIDS.
