Human T-lymphotropic virus type 1(HTLV-1)
a complex type C retrovirus belonging to the
genus deltaretrovirus. In addition to adult T-cell leukemia (ATL) and HTLV-I-associated
myelopathy/tropical spastic paraparesis (HAM/TSP), the virus is considered to be
contribute in various inflammatory diseases, most notably
uveitis, arthritis, myositis and alveolitis (2-4). Although the
distribution of HTLV-1 is global but the higher rates of infected individuals
have been observed in Southern part of Japan, Africa, the Caribbean, South
America (5,6). The first infected adults were
detected by Farid in 1993 with 2.1% prevalence in
Mashhad, a populous
city in Northeastern of Iran with more than 25 million pilgrims and visitors annually. In these regions, between 0.5 and 20% of the general population have specific
antibodies against HTLV-1 and are considered to be healthy carriers(7). Most of HTLV-1 infected individuals
remain Asymptomatic carriers (ACs) through their lives and in a few infected subjects, ATL
or HAM/TSP will develop(8).
Although genome similarities among
HTLV-1 strains is very high, a few nucleotide variation seems to be specific of
the geographical origin of patients. Moreover, disease-specific sequences
have not been found from patients with ATL or HAM/TSP, instead the genomic
variability of HTLV-1 appears to depend on geographic origin more than the
pathology. The development rate of HTLV-1 is very low (particularly compared
to HIV). Currently, based on LTR sequence variation 7 subtypes have been characterized
for this virus; the Cosmopolitan subtype (1a) that has distributed globally
and is further divided into subgroups (A–E), 4 African subtypes (1b, 1d, 1e, 1f)
and a Melanesian/Australian subtype (1c).
In 2005 the Cosmopolitan subtype
(1a) was identified in Torbat-e Heydarieh, Sabzevar and Neyshabur by Rafatpanah
et al. based on obtained sequences from infected adults 7.
To examine the molecular epidemiology and identify the features of the local HTLV-1 strains that circulating in Mashhad community, we performed Polymerase chain reaction (PCR) to amplify the LTR region, then the fragments were purified and cloned into TA cloning vector. Furthermore, all specimens were sequenced and phylogenetic analyses describe HTLV-1 subtype a, mostly affecting the individuals from Mashhad., which is the first time this subtype has been reported in HTLV-1-associated diseases.