![if !IE]> <![endif]>
Tissue tropism of the specific groups or serotypes of adenovirus strain determine the type of disease caused by adenoviruses in humans.
Adenoviruses are transmitted mainly by respiratory or feco– oral contact between humans. They infect the conjunctiva or the nasal mucosa. They may multiply in conjunctiva, pharynx, or small intestine, and then spread to preauricular, cervical, and mesenteric lymph nodes, where epithelial cells are infected. Adenoviruses may cause three different types of interaction with the infected cells. These are (a) lytic infection, (b) latent infection, and (c) transforming infection.
Lytic phase: Adenoviruses infect mucoepithelial cells in therespiratory tract, gastrointestinal tract, and conjunctiva or cor-nea, causing damage of these cells directly. After local replication of the virus, viremia follows with subsequent spread to visceral organs. Dissemination occurs more commonly in immunocom-promised patients than in the immunocompetent individuals.
Latent infection: The adenovirus has a unique ability tobecome latent in lymphoid and other tissues, such as adenoids, tonsils, and Peyer’s patches. The exact mechanism of latency of adenoviruses in these tissues is not known. These latent infec-tions can be reactivated in patients infected with other agents or in the patients who are immunocompromised.
Oncogenic transformation: Some adenoviruses belonging togroups A and B have the property for oncogenic transforma-tion in rodent cells. During oncogenesis, the multiplication of adenovirus is inhibited followed by integration of viral DNA into the host DNA. After integration, adenoviruses produce EIA proteins, which target rodent cells by altering cellular transcrip-tion, finally leading to transformation of rodent cells. However, oncogenesis of human cells has not been demonstrated.
Adenovirus infection is characterized by development of an effective and long-lasting immunity against reinfection. Both cell-mediated immunity (CMI) and humoral immunity are important. CMI plays an important role in limiting prolifera-tion and outgrowth of adenoviruses. Therefore, different dis-ease is seen in persons whose CMI is immunocompromised. Serum antibodies play an important role for resolving ade-novirus infection. Resistance to clinical disease is believed to be directly related to the presence of circulating neutralizing antibodies. The antibodies protect the person from reinfection with the same serotype but not other serotypes. Moreover, ade-novirus infection confers lasting immunity to reinfection with the same serotype.
Copyright © 2018-2023 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.