Geographic and Molecular Epidemiology of Primate T Lymphotropic Retroviruses: HTLV-I, HTLV-II, STLV-I, STLV-PP, and PTLV-L

Abstract

This chapter presents the main geographic and molecular epidemiological characteristics of primate T lymphotropic (onco)retroviruses (PTLVs) exhibiting common features, including a characteristic and peculiar micro-epidemiology with a puzzling distribution throughout the world, similar modes of transmission, mainly through breast feeding and sexual contact, and a high genetic stability over time, which can be used as a molecular means to follow migrations of infected populations in the recent or distant past. The high stability of the HTLV-1/11 genomes, their integration, and their lifelong latency make the subtle mutations observed unique molecular markers for tracing the geographic path of evolution of such viruses, paralleling the migration of the carriers. The present world repartition of the HTLV-I/STLV-I genotypes is the result of at least three independent events: interspecies transmission from simian to human, evolution in some remote populations, and migration of infected populations. In regard to HTLV-11, its presence in isolated Amerindian populations disseminated throughout the Americas and its apparent absence elsewhere had led some authors to the speculation that this virus was exclusively a “New World virus” endemic in native Amerindians over centuries or millennia. The virus is supposed to have been introduced to the Americas through the successive waves of migrations that occurred from Siberia through the Bering strait area millennia ago.