Viruses etiology

Puryear WB, Yu X, Ramirez NP, Reinhard BM, Gummuluru S. HIV-1 incorporation of host-ceU-derived glyco-sphingoHpid GM3 allows for capture by mature dendritic cells. Proc Natl Acad Sci USA. 2012 109(19) 7475-7480. Ball MJ, Lukiw WJ, Kammerman EM, Hill JM. Intracerebral propagation of Alzheimer s disease strengthening evidence of a herpes simplex virus etiology. Alzheimers Dement. 2013 9(2) 169-175. 

Over 20 infectious agents have been incriminated as etiologic agents for many the causal relationship has been disproved, and for others there is conflicting evidence. Human herpesvirus 6 (HHV-6) is currently the most likely causative virus. HHV-6 may initiate the autoimmune processes of MS in one of two ways. First, HHV-6 is structurally similar to myelin basic protein. When T cells become sensitive to HHV-6, the cells may attack myelin basic protein. Second, HHV-6 may directly stimulate the complement cascade, activating autoimmune processes.5 Infection with HHV-6 alone cannot fully explain MS, because HHV-6 is found in 75% of all people, but MS is much more rare. 

For nearly 80% of patients with epilepsy, the underlying etiology is unknown.8 The most common recognized causes of epilepsy are head trauma and stroke. Developmental and genetic defects are the cause of about 5% of cases of epilepsy. Central nervous system (CNS) tumors, central nervous system infections, and neurodegen-erative diseases are other common causes. Other important causes of epilepsy are human immunodeficiency virus infection or neuro-cysticercosis infection, primarily occurring in Latin America. 

DNA viruses modulate the host immune response, e.g., most likely the etiologic agent of Kaposfs sarcoma, KSHV (human herpes vims —8), has captured complement-binding proteins, three cytokines (two macrophage inflammatory proteins and interleukin 6), bcl-2, interferon regulatory factors, interleukin 8 receptor. Certain retroviruses... 

A viral etiology has been implicated in Burkitt s lymphoma, and there is some evidence that Epstein-Barr virus causes infectious mononucleosis in Europe and Burkitt s lymphoma in Africa. It has been suggested that if the cause of the Burkitt s lymphoma is viral, then entry of the virus particles into the lymphoid colls of the body may derange a part of the cell immune process, subsequently affecting the production of the IgM antibody, a theory which is compatible to the dysproteinemia sometimes seen in multiple myeloma and other lymphomas (N2). Also in support of this is the observation that C-reactive protein was markedly elevated in the serum of patients with Burkitt s lymphoma, and disappeared entirely from the blood when they were cured (MIO). The relationship between malarial infection and Burkitt s lymphoma has been dealt with in a previous section on malaria. 

Nearly 40 million people are infected with the human immunodeficiency virus (HIV). Over half of those infected reside in sub-Saharan Africa. Worldwide during 2004, it is estimated that nearly 14,000 people a day were infected. Human immunodeficiency virus type 1 is the primary etiological source for the acquired immunodeficiency syndrome (AIDS). Fortunately, people infected with HIV are leading longer and more productive lives due to the availability of more effective therapies. Better medicines have evolved due to the efforts of scientists worldwide who find targets and compounds that inhibit the virus life-cycle. The current treatment for HIV infection is via a drug cocktail that usually includes a protease inhibitor (PI), a nucleoside reverse transcriptase inhibitor (NRTI), and a non-nucleoside reverse transcriptase inhibitor (NNRTI). 

Poliovirus. A virus of the genus Enterovirus that is the etiological agent of poliomyelitis, separable on the basis of specificity of neutralizing antibody into three serotypes, designated types 1, 2, and 3. 

Hepatitis C virus (HCV) is an RNA virus that is a common cause of parenterally acquired viral hepatitis chronic infection follows acute infection in 80% to 85% of cases. Although liver disease resulting from chronic HCV infection is only slowly progressive, HCV is the most common cause of chronic liver disease in the United States, the most common etiology for hepatocellular carcinoma, and the leading indication for liver transplantation [34-36]. 

The Epstein-Barr viruses play an etiological role in infectious mononucleosis, an acute infections disease that affects lymphoid tissue throughout the body. A strong association of this virus with Burkitf s lymphoma and perhaps nasopharyngeal carcinoma also has been observed. 

Several DNA viruses are associated with, and are important in, the etiology of certain human cancers. For example, chronic infection with hepatitis B or C virus (HBV, HCV) is associated with liver cancer, infection with human papillomavirus (HPV) type 16 and type 18 is associated with cervical cancer, and infection with Epstein-Barr virus (EBV) is associated with Burkitt s lymphoma. About one-fifth of human cancer worldwide is associated with DNA oncogenic viruses. In 2006, the FDA approved a vaccine against HPV 16 and 18, which are responsible for about 70% of cervical cancer cases. 

---