Simian-T-lymphotropic virus

Simian T-lymphotropic virus (STLV) is a type of retrovirus that infects non-human primates (NHPs), including various species of monkeys and apes. It is closely related to the Human T-lymphotropic virus (HTLV), a virus that infects humans and can cause a variety of diseases, including adult T-cell leukemia/lymphoma (ATL) and a neurological disorder known as HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). The relationship between STLV and HTLV suggests a zoonotic origin for HTLV, where the virus has been transmitted from non-human primates to humans, leading to the evolution of HTLV.

Classification

STLV belongs to the genus Deltaretrovirus within the family Retroviridae. The virus is classified into several types, mirroring the classification of HTLV in humans. The most well-studied types are STLV-1, STLV-2, and STLV-3, which correspond to HTLV-1, HTLV-2, and HTLV-3 in humans, respectively. Each type is further divided into subtypes based on genetic differences.

Transmission

STLV is primarily transmitted among non-human primates through bodily fluids, such as blood, breast milk, and sexual contact. The close contact within social groups of primates facilitates the transmission of the virus. Vertical transmission from mother to offspring is also a significant route of transmission, similar to HTLV in humans.

Pathogenesis

The pathogenesis of STLV in non-human primates is not fully understood, but it is believed to be similar to that of HTLV in humans. The virus integrates its DNA into the host's genome, which can lead to the clonal expansion of infected cells. In some cases, this can result in malignant diseases such as leukemia or lymphoma. However, the majority of infected individuals remain asymptomatic carriers of the virus.

Zoonotic Potential

The close genetic relationship between STLV and HTLV suggests a zoonotic potential, where the virus can be transmitted from non-human primates to humans, leading to the emergence of HTLV. This cross-species transmission is believed to have occurred multiple times throughout human history, with evidence of STLV/HTLV co-infection in some human populations that are in close contact with non-human primates.

Research and Implications

Research on STLV not only helps in understanding the biology and evolution of retroviruses but also provides insights into the origins and transmission of HTLV in humans. Understanding the mechanisms of STLV transmission and pathogenesis in non-human primates can aid in the development of strategies to prevent the zoonotic transmission of similar viruses to humans.

Prevention and Control

Preventing the zoonotic transmission of STLV involves minimizing direct contact between non-human primates and humans, especially in regions where such contact is common. Public health measures, including education about the risks of zoonotic diseases and the promotion of safe handling and conservation practices, are essential in regions where humans and non-human primates coexist.