| Abstract: | Hepatitis C virus (HCV) genotype 4 (HCV-4) infection is considered to be difficult to treat and has become increasingly prevalent in European countries, including The Netherlands. Using a molecular epidemiological approach, the present study investigates the genetic diversity and evolutionary origin of HCV-4 in Amsterdam, The Netherlands. Phylogenetic analysis of the NS5B sequences (668 bp) obtained from 133 patients newly diagnosed with HCV-4 infection over the period from 1999 to 2008 revealed eight distinct HCV-4 subtypes; the majority of HCV-4 isolates were of subtypes 4d (57%) and 4a (37%). Three distinct monophyletic clusters were identified, with each one having a specific epidemiological profile: (i) Egyptian immigrants infected with HCV-4a (n = 46), (ii) Dutch patients with a history of injecting drug use infected with HCV-4d (n = 44), and (iii) Dutch human immunodeficiency virus (HIV)-positive men who have sex with men (MSM) infected with HCV-4d (n = 26). Subsequent molecular clock analyses confirmed that the emergence of HCV-4 within these three risk groups coincided with (i) the parenteral antischistosomal therapy campaigns in Egypt (1920 to 1960), (ii) the popularity of injecting drug use in The Netherlands (1960 to 1990), and (iii) the rise in high-risk sexual behavior among MSM after the introduction of highly active antiretroviral therapy (1996 onwards). Our data show that in addition to the influx of HCV-4 strains from countries where HCV-4 is endemic, the local spread of HCV-4d affecting injecting drug users and, in recent years, especially HIV-positive MSM will further increase the relative proportion of HCV-4-infected patients in The Netherlands. HCV-4-specific agents are drastically needed to improve treatment response rates and decrease the future burden of HCV-4-related disease.Hepatitis C virus (HCV) affects an estimated 170 million people worldwide. HCV infection persists in 50 to 85% of those infected and can, over decades, lead to cirrhosis and hepatocellular carcinoma (11). The HCV genome displays considerable sequence divergence, and HCV variants have been classified into seven major genotypes. Genotypes 1, 2, 3, 4, and 6 are further subdivided into numerous subtypes (subtypes a, b, c, etc.) (27). In the absence of complete genome sequences, the designation of a subtype is based mainly on consensus regions in the core/E1 and NS5B regions of the HCV genome (27). The HCV genotype distribution depends on the geographical region and the mode of transmission. As the distribution of HCV genotypes can change over time, genotyping provides a powerful tool that may be used to investigate the spread of HCV within a community (18).In Europe, North America, and Australia, most HCV-infected patients (>80%) are infected with genotype 1, 2, or 3 (10). HCV genotype 4 (HCV-4) is the most common genotype in the Middle East and in northern and central Africa, accounting for more than 20% of all chronic HCV infections worldwide (28). In Egypt, the country with the highest prevalence of HCV in the world, more than 90% of patients are infected with HCV-4 (22). HCV-4 is considered difficult to treat and has a sustained virological response rate of approximately 60% (28), where the rates are 40 to 50% for genotype 1 and 80 to 90% for genotypes 2 and 3 (17).Recent studies emphasize that the prevalence of HCV-4 in Europe has increased in the past few decades due to the immigration of HCV carriers and the subsequent spread of HCV-4 in European populations at risk for HCV infection (2, 5, 16, 24, 25, 30). In southern Europe, HCV-4 is responsible for 10 to 24% of chronic HCV infections. In The Netherlands, HCV-4 accounts for an estimated 10% of chronic HCV infections (6, 32). Currently, the development of new genotype-specific antiviral agents is focused mainly on HCV genotype 1. The emergence of HCV-4 may require agents specific for HCV-4 to improve the response rates and decrease the future burden of HCV-4 disease. The population of the region around Amsterdam, The Netherlands, comprises many ethnicities and diverse groups at risk for HCV infection, providing the opportunity to explore changes in the epidemiology of HCV-4. The aim of the study described here was to increase our understanding of the spread of HCV-4 in The Netherlands by using a molecular epidemiological approach. To our knowledge, this is the second study to have used phylogenetic analysis of HCV-4 isolates from a large cohort to investigate the genetic diversity of HCV-4 in Europe (14) and the first to include evolutionary analysis to describe the origin and spread of these subtypes. |
