chronic viral hepatitis c is one of the most serious chronic infections affecting 170 million people worldwide . in europe the prevalence of hepatitis c virus ( hcv ) infection is also relatively high in latvia . antibodies are found in 2.4% of the population , with hcv - rna prevalence of 1.7% of general population . the outcome of hcv infection varies from spontaneous viral clearance , symptom free - hcv carrier state to chronic hepatitis , cirrhosis , and hepatocellular carcinoma . some individuals have rapidly progressive liver disease while others remain in good health for many years . there are a lot of factors such as viral kinetics , immune mechanisms , environmental factors , and patient - related factors which may be responsible for the various hcv - related outcomes . risk factors for infection include intravenous and intranasal drug use , nonsterile tattooing , manicure and pedicure procedures , as well as virus transmission vertically from mother to child , and during sexual intercourse . dialysis patients appear to be at increased risk of infection as do alcoholics [ 1 , 3 ] . in developing and transitional economy countries , the nosocomial transmission of new hepatitis c virus ( hcv ) infections is a major problem due to reuse of contaminated or inadequately sterilized syringes and needles used in medical , paramedical , and dental procedures ; an estimated 2.34.7 million new infections occur each year . current standard of care treatment involves combination therapy with hopes of effective virus eradication resulting in a sustained virological response ( svr ) and thereby stopping the progression of disease . with the combination of pegylated alpha interferon and ribavirin , they induce inflammatory responses that can lead to tissue injury and serve as antiviral effectors as well . cytokine synthesis is regulated by genetic mechanisms resulting in differences between individuals in their ability to produce cytokines . this individual variability may be due to single - nucleotide polymorphisms within the coding regions of cytokine genes . cytokine genes are polymorphic , and some of these variants modify the production of the specific cytokines thereby affecting the host immune response . in hcv infection , secretion of inappropriate amounts of cytokines may be associated with developments of chronic disease or resistance to interferon ( ifn ) treatment . interleukin-28b ( il-28b ) , named also as interferon -3 , has been shown to be involved in the control of hcv infection , and the genetic polymorphism of the encoding il-28b gene may determine the clearance of hcv . the il-28b gene on human chromosome 19q was discovered in 2003 , using the genomic screening process in which the entire human genome was scanned for putative genes [ 5 , 6 ] . the aim of this study was to detect il-28b gene polymorphism in chronic hepatitis c patients in latvia and to analyze therapy results in patients with different il-28b gene polymorphisms . this is the first study carried out in latvia , in the baltic states and likely in eastern europe for the detection of interleukin 28b gene polymorphism and how it impacts on hepatitis c treatment . all chronic viral hepatitis c patients who came to infectology center of latvia for a hepatologist 's consultation were tested . patients had to sign the informed patients ' consent prior to testing . in order to detect il-28b gene polymorphism  rs12979860 genotype frequency we used molecular biology methods : classical dna separation from blood samples by phenol , amplification by pcr , and standard sequencing by big dye ( applied biosystems ) . 142 patients were treated with the standard of care therapy - pegylated interferon in combination with ribavirin . all patients were divided into 3 subgroups : cc , ct / tc , and tt . different patient factors , laboratory tests , viral kinetics , and treatment response were analyzed . in terms of therapy result patients responders achieved sustained virological response and were hcv - rna negative at the end of therapy and 24 weeks after stopping treatment . nonresponders were hcv - rna positive at week 12 ( null responders ) , at the end of therapy ( partial responders ) or at week 24 after stopping therapy ( relapsers ) . interrupters stopped therapy due to financial reason ( there is 75% drug reimbursement for chronic hepatitis c treatment , 25% of treatment expenses are covered by patient ) or due to unknown reason . hcv - rna was measured using polymerase chain reaction ( pcr ) , amplicor , version 2.0 ; roche , usa . viral load for genotype 1 patients was measured at baseline and at week 12 on treatment . liver biopsy was performed for 126 ( 88.7% ) patients , and morphological assessment was done using knodell 's hai index . there were not statistically significant differences between groups with regard to fibrosis stage and hai index . comparison between groups was performed using pearson chi - square test or fisher 's exact test . study was approved by the independent ethics committee for clinical investigation of drugs and pharmaceutical products in latvia . there were 53 patients ( 33% ) with cc genotype , 84 patients ( 53% ) with ct ( 83 patients ) or tc ( 1 patient ) genotype , and 22 patients ( 14% ) with tt genotype among chronic viral hepatitis c patients in latvia ( figure 1 ) . 142 patients were treated with the standard of care therapy - pegylated interferon in combination with ribavirin table 1 . all included patients were caucasians , a majority of them male ( 59% ) and genotype 1 ( 61% ) patients . 34 patients ( 74% ) in cc genotype subgroup achieved svr versus 50 patients ( 52% ) in non - cc subgroup41 patient in ct / tc and 9 patients in tt subgroups . there were 4 patients ( 8.7% ) nonresponders in cc subgroup ( all were relapsers : 3 of them with hcv genotype 1 , 1 patient hcv genotype 2 ) versus 35 patients ( 36.5% ) in non - cc subgroups ( 7 patients null responders , hcv genotype 1 , 13 patients partial responders : 11 patients hcv genotype 1 , 2 patients hcv genotype 3 , and 15 patients relapsers , hcv genotype 1 ) ; the differences were statistically significant , p = 0.002 , pearson chi - square test ( figure 2 ) . there was statistically significant difference also in patients with genotype 1 hcv infection  svr which was achieved in 16 patients ( 16/19 , 84% ) in cc subgroup versus 30 patients ( 30/63 , 47.6% ) in non - cc subgroups , p = 0.007 , fisher 's exact test ( table 2 ) . the last two decades have seen major advances in hcv treatment options and patient management . however , the standard of care treatment ( peg interferon plus ribavirin ) is effective in less than half of chronically infected hcv genotype 1 treatment nave patients , regardless of the type or dose of peg interferon used [ 810 ] . there are many factors influencing therapy result ; sometimes it is hard to understand which of them is the most essential . during recent years there are publications of interleukin 28b gene polymorphism as a strong predictor of svr in patients treated with pegylated interferon and ribavirin . according to thompson et al . data , published in 2010 , il-28b gene polymorphism between caucasians is distributed as follows : cc 37% , ct 51% , and tt 12% . in latvia majority of people are caucasians . these results are similar to our data : cc33% , ct 53% , and tt 14% . svr rates achieved in thompson 's study are 69% of patients in cc group , 33% in ct group , and 27% in tt group . in our study this difference is probably because of different patient profile : we included all genotype patients ( 61% were 1st genotype ) , but in thompson 's study there were only 1st genotype patients included , and it is already known that svr rates are better in patients with 2nd and 3rd genotypes . have published data in cemed where cc genotype in hcv patients was noted with significantly lower frequency than in healthy controls ( 79/281 , 28.11% versus 54/104 , 51.92% ) , suggesting a protective role of this variant . also patients treated with pegylated interferon and ribavirin with cc genotype achieved svr at significantly higher rates , than those with tt genotype ( 25/46 , 54.34% versus 7/24 , 29.16% ) . if we analyze only hcv genotype 1 patients , our data shows slightly better results in comparison with thompson and par studies . in cc subgroup svr was achieved in 69% ( thompson ) , 54.34% ( par ) , and 84% in our study . in addition , in our study we analyzed other different treatment efficacy factors , including number of missed treatment doses . we have to stress that chronic viral hepatitis c patients are paying 25% of treatment costs themselves in latvia , and 75% is covered by sick fund . actually they are highly motivated to use assigned medicine . in terms of the higher svr on cc genotype patients from the study cohort when compared with thompson et al . ' 2010 study , this cohort had younger patients with lower bmi 's , but with higher advanced fibrosis and steatosis rate . besides that , fibrosis stage was higher in nonresponders group , in comparison to responders group , p = 0.029 , mann - whitney u - test . these factors influence svr rates in hepatitis c patients and could have played a role as well in the difference from virologic responses . our study is the first study in latvia and baltics done on interleukin b28 gene polymorphism with findings similar to other studies involving caucasian patients . while the most prevalent genotype of il-28b in latvia is ct , the most favorable response to treatment and svr is seen in genotype cc patients .