Type D oncornaviruses are a group of retroviruses that belong to the family Retroviridae. They are characterized by their ability to cause tumors or cancerous growths in various animal species. These viruses primarily affect primates, including monkeys, apes, and humans. The "D" designation refers to their distinct properties and phylogenetic classification.
Type D oncornaviruses have an enveloped structure and contain two copies of positive-sense, single-stranded RNA as their genetic material. The viral RNA genome is reverse transcribed into DNA by the viral reverse transcriptase enzyme upon infection of host cells. This DNA is then integrated into the host cell's genome, leading to persistent infection.
These oncoviruses are primarily transmitted horizontally via bodily fluids such as blood, saliva, or respiratory secretions. However, they can also be vertically transmitted from mother to offspring during childbirth or through breastfeeding. While some individuals infected with type D oncornaviruses may remain asymptomatic, these viruses are known to cause various diseases, including neoplastic disorders in certain primate species.
The pathophysiological mechanisms underlying type D oncornavirus-related cancers are not fully understood. However, they are thought to involve the expression of viral oncogenes, interference with host immune responses, and disruption of cellular regulatory pathways involved in cell growth and division.
Research on type D oncornaviruses is ongoing, aiming to gain a comprehensive understanding of their biology, transmission dynamics, and potential implications for human and animal health.