host genetic factors are major determinants of susceptibility to infectious disease in humans ( 1 ) .
htlv - i is a persistent virus , infecting 10 - 20 million people worldwide .
most infected people remain healthy , but 1 - 2% develops a progressive paralytic myelopathy ( htlv - i - associated myelopathy ; ham / tsp ) and a further 2 - 3% develops an aggressive t cell leukemia / lymphoma .
ham / tsp is a chronic debilitating inflammatory disease of the central nervous system , characterized by axonal damage and demyelination , most pronounced in the midthoracic spinal cord .
furthermore some of the self - immune diseases such as uveitis and polymiositis are found to be resulted from this virus ( 2 - 5 ) .
the endemic regions affected with this virus include the south - west of japan , caribbean islands , and some regions of the usa ( 6 ) .
the other parts with less prevalence of the virus are taiwan and some regions of africa and israel .
mashhad in the north of iran has been recognized as a new endemic region of the virus ( 10 , 11 ) .
the symptoms include weakness or dryness in one or both feet , backache and no control on urine .
one - third of the patients become paralyzed after 10 years and one half of them are not able to walk ( 12 ) . on the contrary to alt
in which the number of the male patients is a little more , ham affects the female disproportionately .
high proviral load and being female are two factors of high risk of ham / tsp and the relative risk of ham / tsp increases when the provrial load becomes clearly more than one copy in any pbmcs ( 13 , 14 ) .
both the class i mhc proteins ( hla - a , -b , and -c ) , which present viral peptides for recognition by virus - specific ctl , and class ii mhc proteins ( hla - dr and -dq ) , which present peptides to cd4 t cells , are likely to be important in the immune response to htlv - i infection ( 15 , 16 and 17 ) .
the results of several previous studies have suggested associations between various hla class i or class ii alleles and susceptibility to t cell leukemia / lymphoma or ham / tsp ( 18 - 22 ) .
however , small sample size , mixed ethnicity , lack of adequate controls , or lack of staging in these studies precluded a definite conclusion .
if the relationship between htlv-1 infection and class ii is considered as the factor of susceptibility to disease , it may help in understanding pathogenesis of ham / tsp .
the supplied peptides of axon antigens bonded to the products of mhc class ii activate cd4+on the surface of t lymphocytes and the activated cd4+can cross the blood - cerebral obstacle and identify the cell affected with virus .
the activated cd4 + causes apoptosis through producing cytokins and damage to the cell affected with virus and the peripheral cells may play a role in cns ( 23 , 24 ) .
both mhc class i and class ii molecules are important in determining the recognition of htlv - i peptides and for the generation of an effective immune response .
the predominant cytotoxic t lymphocyte response ( ctl ) against tax protein , which is necessary for viral expression , can be restricted by a wide variety of mhc class i molecules in htlv - i infected subjects .
it has been suggested that no single mhc class i allele is associated with ham / tsp ( 15 , 25 ) . in japanese htlv - i - infected subjects has been demonstrated that expression of hla - a*02 and hla cw*08 alleles reduced the proviral load of htlv-1 and consequently the risk of ham / tsp , while hla - b*5401 allele increased the proviral load and the risk of ham / tsp in htlv - i carriers .
furthermore , hla - drb1 * 0101 increased the risk of ham / tsp in carriers in the absence of hla - a*02 ( 18 , 21 ) .
the aim of this study was to investigate the frequency of hla - dqb1 alleles in htlv - i - infected individuals and healthy controls resident in mashhad .
the studied subjects were 66 , including 16 ham / ts patients , 20 asymptomatic carriers and 30 healthy controls .
sixteen of 20 ham / tsp patients were female ( 60% ) and 72% of htlv - i carriers were female .
the mean age of patients was 44.1414.62 and the mean age of htlv - i carriers was 51 10.22 .
all patients fulfilled established criteria for ham / tsp when they examined by neurologist and htlv - i carriers had symptoms of htlv - i - associated diseases .
all of the ham / tsp patients , htlv - i carriers and healthy controls had the same ethnic background .
the study protocol was approved by the ethics committee of mashhad university of medical sciences .
10 cc blood was taken from all the subjects for dna extraction and serum preparation .
serum samples were screened for htlv - i antibody by enzyme linked immunosorbent assay ( elisa ) according to the manufactures ' instruction ( diapro , italy ) and reactive samples were confirmed by western blotting ( genelab diagnostic , singapore ) .
dna was extracted by non - enzyme salting out method using biogen kit ( mashhad - iran ) according to manufacturer 's instruction .
polymerase chain reaction with sequence - specific primers ( pcr - ssp ) method was carried out to determine hla - dqb1 alleles according to the previously published method ( 26 ) .
briefly , seven alleles of hladqb1 were detected using specific primers in eight pcr reactions .
this procedure currently detected dqb1 alleles including 0501 - 0504 , 0601 - 0609 , 0201 , 0301 - 0305 , and 0401 - 0402 which corresponding to the serological specificities dq4 , dq5 and dq6 alleles , whereas the dq2 , dq7 , dq8 and dq9 specificities were amplified by two primer mixes .
we used at least 2 primers ( primm - italy ) for each reaction ( table 1 , 2 ) .
the studied subjects were 66 , including 16 ham / ts patients , 20 asymptomatic carriers and 30 healthy controls .
sixteen of 20 ham / tsp patients were female ( 60% ) and 72% of htlv - i carriers were female .
the mean age of patients was 44.1414.62 and the mean age of htlv - i carriers was 51 10.22 .
all patients fulfilled established criteria for ham / tsp when they examined by neurologist and htlv - i carriers had symptoms of htlv - i - associated diseases .
all of the ham / tsp patients , htlv - i carriers and healthy controls had the same ethnic background .
the study protocol was approved by the ethics committee of mashhad university of medical sciences .
10 cc blood was taken from all the subjects for dna extraction and serum preparation .
serum samples were screened for htlv - i antibody by enzyme linked immunosorbent assay ( elisa ) according to the manufactures ' instruction ( diapro , italy ) and reactive samples were confirmed by western blotting ( genelab diagnostic , singapore ) .
dna was extracted by non - enzyme salting out method using biogen kit ( mashhad - iran ) according to manufacturer 's instruction .
polymerase chain reaction with sequence - specific primers ( pcr - ssp ) method was carried out to determine hla - dqb1 alleles according to the previously published method ( 26 ) .
briefly , seven alleles of hladqb1 were detected using specific primers in eight pcr reactions .
this procedure currently detected dqb1 alleles including 0501 - 0504 , 0601 - 0609 , 0201 , 0301 - 0305 , and 0401 - 0402 which
corresponding to the serological specificities dq4 , dq5 and dq6 alleles , whereas the dq2 , dq7 , dq8 and dq9 specificities were amplified by two primer mixes .
we used at least 2 primers ( primm - italy ) for each reaction ( table 1 , 2 ) .
the frequency of hla - dqb1 alleles was calculated in ham / tsp patients , asymptomatic carriers and healthy control groups .
the frequency of hla - dqb1 * 07 was significantly higher in patients with ham / tsp ( 75% ) compared with healthy controls ( 30% ) ( p = 0.004 , or=8.52 ) ( table 1 ) .
the hla - dqb1 * 02 and dqb1 * 05 was positive in 7 ham / tsp patients , while in healthy control group 24 subjects were positive .
the frequency of both hla - dqb1 * 07 and hla - dqb1 * 06 alleles in ham / tsp patients was more than the ones if they infected with more than the ones free of it if they are infected with htlv-1 ( p- value=0.0009 and rr=10.95 ) ( table 3 ) .
in the present study we examined the frequency of hla - dqb1 allele in ham / tsp patients , asymptomatic carriers and healthy controls .
our results indicated that the individuals with dqb1 * 07 allele are susceptible to be affected with this disease 7 times more than the ones lacking this allele , suggesting hla genes play a significant role in the susceptibility to ham / tsp disease . within african population , two antigens determined dr15 and dq1 , occurred at significantly increased frequency among htlv - i carriers compared with seronegative control subjects ( 42% versus 22% for dr15 [ odds ratio { or } = 2.7 ; 95% confidence interval { ci } = 1.0- 7.2 ] and 78% versus 53% for dq1 [ or = 3.1 ; 95% ci = 1.2 - 8.5 ] ) .
asymptomatic carriers were shown to have an hla class ii allele distribution similar to that of patients with atl , and the frequencies of the alleles drb1 * 1501 , drb1 * 1101 , and dqb1 * 0602 were significantly greater in patients with atl and asymptomatic carriers than in patients with ham / tsp .
in addition , haplotypes drb1 * 1101-dqb1 * 0301 and drb1 * 1501-dqb1 * 0602 were significantly increased among patients with atl compared with patients with ham / tsp ( 28 ) .
we also showed that the individuals with hla - dqb1 - 2 and hla - dqb-5 are 1.5 times more susceptible to develop ham / tsp compared with the subjects who lacked these alleles , therefore , these two alleles may be considered as the protective factors .
rafatpanah et al ( 19 , 20 ) demonstrated that the frequency of hla - drb1 * 01 was significantly increased in ham / tsp patients compared with carriers ( p 0.028 ; or=9.4 ) .
the frequency of hla - cw*08 was also significantly increased in ham / tsp patients compared with controls ( p=0.03 ; or=13.5 ) .
it has been showed that there is an association between hla class i , hla - a30 allele and htlv - i infection ( 15 , 20 ) .
kitze et al showed that the ham / tsp patients with particular hla haplotypes ( a24cw7b7dr1dq5 , a2cw7b7dr1dq5 , a24cw - b52dr15dq6 , a11cw1b54dr4dq4 , and a24cw1b54dr4dq4 ) express more frequently intrathecal synthesis of antibodies against htlv-1 synthetic peptides , especially against htlv-1 env gp21 synthetic peptides ( 21 ) .
an association of hla - drb1 * 0101 with disease susceptibility also was identified , which doubled the odds of ham / tsp in the absence of the protective effect of hla - a*02 ( 22 ) . in the present study ,
the frequency of hla - dqb1 * 07 in ham / tsp patients was high .
it seems that there is a correlation between hla - dqb1 * 07 and disease susceptibility .
the genotype of hla - dqb1 * 06 and 07 was more frequent in patients with ham / tsp compared with control group ( 26 ) .
this results is different from the results obtained kitze et al ( 25 ) who reported that there is a higher risk to develop ham / tsp among the individuals with hla - dq-0105 haplotype .
this discrepancy may be associated with the difference in the genetic background of studied population ( 27 ) .
although we find an association between hla - dqb1 alleles and ham / tsp , however the study should be repeated with more sample size .
furthermore , the study of other hla class i and class ii alleles should be taken into account to understand a more comprehensive role of hla alleles in disease susceptibility .
 objective(s ) : htlvi-1 is the first human retrovirus with limited endemic regions in the world . 
 the epidemiological studies have shown that the genetic background and immune response to the virus have a significant role in htlv - i - associated diseases . among the genes 
 are involved in htlv - i infection , the role of human leukocytes antigen ( hla ) have been studied in different population . in the present study we examined the association between hla - dqb1 alleles and htlv - i infection in ham / tsp patients , htlv - i carriers and healthy controls in north east of iran , mashhad.materials and methods : the blood samples of 16 patients with ham / tsp , 20 htlv-1 carriers , and 30 healthy individuals were taken and dna was extracted by salting out method . 
 hla - dqb1 typing was performed using pcr - ssp method and the frequency of hla - dqb1 alleles were compared by fischer exact test.results : there was a significant difference between ham / tsp patients and healthy controls in the frequency of hla - dqb1 * 07 ( p=0.004 , rr=7 ) . 
 furthermore , we found that possession of hla- dqb1 * 02 or hla - dqb1 * 05 increased the risk of disease 1.5 times.conclusion : the data presented here suggest that both hla - dqb1 * 07 and hla - dqb1 * 06 are associated with disease development . 
Introduction
Materials and Methods
Study population
Serological assay
HLA-DQB1 typing
Results
Discussion
Conclusion