Re: REPOST: INFO: Hepatitis C Virus Genotypes and Quasispecies

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I always get what I need from our slayers when i was told about my hepc i was told geno type 1b now they r saing 1b & 1a iam very confussed i have read and read this virus can mutane itself?????????????????/Dannella wrote: Although a great article, it is old, and the following statement has been corrected, the first record of HCV is in 1942, US Military Troops. "It is believed that the hepatitis C virus has evolved over a period of several thousand years. This would explain the current general global patterns of genotypes and subtypes:" Another discrepancy is how many different genotypes , this article states 11 verses the 6 recognized by the CDC. Genotypes

Explained It is much easier to talk of the hepatitis C virus as if it is a single organism but in fact it is a range of viruses, similar enough to be called hepatitis C virus, yet different enough to be classified into subgroups. Viruses are microscopic and no person could ever see them with the naked eye. Indeed, HCV is so small that there's been no confirmed actual sighting of it using any type of microscope yet developed. Consequently, a better way to understand the terms HCV 'genotypes' and 'subtypes' is

to compare them to things that we can more readily relate to. Genotypes The group of birds we call 'raptors' (birds of prey) have evolved into different main types. Imagining raptors as being hepatitis C viruses, you could take one major raptor type, such as eagles, and imagine these as being one of HCV's main types (genotypes). Subtypes But eagles as a group are made up of different sub types such as the American Bald Eagle and Australia's Wedge Tailed Eagle and Sea Eagle. You could imagine each of these as being one of the HCV subtypes that make up an HCV genotype. Quasispecies Within each of above particular types of eagles, there are

further differences. All Wedge Tailed Eagles, for example, differ from each other in regard to wing span, weight, colour, beak size, etc. Similarly, within a hepatitis C sub-type, individual viruses differ from each other ever so slightly. Such viral differences are not significant enough to form another sub-type but instead form what's known as quasi-species. It is believed that within an HCV sub-type, several million quasispecies may exist. Scientists predict that people who have hepatitis C, have billions of actual viruses circulating within their body. Although there may be one or two predominant sub-types, the infection as a whole is not a single entity and is composed of many different quasispecies. Classifications Biologists are generally not known for creativity when it comes to naming things - hence hepatitis C virus. The most commonly used

classification of hepatitis C virus has HCV divided into the following genotypes (main types): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11. As we've highlighted, HCV genotypes can be broken down into sub-types, some of which include: 1a, 1b, 1c2a, 2b, 2c3a, 3b4a, 4b, 4c, 4d, 4e5a6a7a, 7b8a, 8b9a10a11a Genotype patterns It is believed that the hepatitis C virus has evolved over a period of several thousand years. This would explain the current general global patterns of genotypes and subtypes: 1a - mostly found in North & South America; also common in Australia1b - mostly found in Europe and Asia.2a - is the most common genotype 2 in Japan and China.2b - is the most common genotype 2 in the US and

Northern Europe.2c - the most common genotype 2 in Western and Southern Europe.3a - highly prevalent here in Australia (40% of cases) and South Asia.4a - highly prevalent in Egypt4c - highly prevalent in Central Africa5a - highly prevalent only in South Africa6a - restricted to Hong Kong, Macau and Vietnam7a and 7b - common in Thailand8a, 8b & 9a - prevalent in Vietnam10a & 11a - found in Indonesia It's believed that of the estimated 160,000 Australians with HCV, approx. 35% have subtype '1a', 15% have '1b', 7% have '2', 35% have '3' (mostly being 3a). The remaining people would have other genotypes. Genotype and treatment Current scientific belief is that factors such as duration of a person's HCV infection, their HCV viral load, age, grade of liver

inflammation or stage of fibrosis may play an important role in determining response to interferon treatment. Recent studies have suggested that a person's HCV subtype (or subtypes) may influence their possible response to interferon, or interferon-ribaviri n combination treatment. World-wide trials are being conducted which will soon shed more light on this belief. We'll publish any reports as they come to hand. Genotypes and Genetic Variation of Hepatitis C Virusby G. Maerterns & L. Stuyver,reviewed by Dr Greg Doreof the National Centre in HIV Epidemiology & Clinical Research.From The Hep C Review; Ed 23, December 1998; Harvey Genotypes and Quasispecies Hepatitis C Virus Genotypes The term "genotype" refers to HCV isolates from geneticallydistinct groups, which have arisen during the evolution of thisvirus. Hepatitis C virus demonstrates tremendous genetic diversitywhich has wide-ranging implications for diagnosis and treatment ofHCV infection. Currently, there are six known hepatitis Cgenotypes, each with numerous subtypes. Genotype variation can be found worldwide. However, the relativeprevalence of different genotypes differs by geographic region. Inthe United States, for example, genotype 1 is the most prevalentwhereas in Egypt genotype 4 accounts for the majority ofinfections. Clinical Significance of HCV

Genotypes Determining the genotype of an individual patient's HCV isolate mayhave important treatment implications. Of utmost clinicalsignificance is the role that genotypes play in response totreatment and in determining the optimum duration of treatment. Forexample, with all treatments tested to date, patients withgenotypes 2 and 3 are more than twice as likely as patients withgenotype 1 to achieve a sustained virologic response. In addition,when using combination therapy consisting of interferon andribavirin, a 24-week course is recommended for genotypes 2 or 3compared to 48 weeks for patients with genotype 1. Although thesignificance of genotype in treatment response is clear, theinfluence of genotype on the severity of liver damage and the rateof disease progression has not been well defined. Mostinvestigations suggest one viral

genotype is no more virulent thanany other, and that other factors are responsible for the variationseen in medical outcomes of chronic hepatitis C infection. Quasispecies and Viral Mutation Within an individual viral isolate identified as a particulargenotype, further genetic heterogeneity exists. Through spontaneousmutations, closely related yet significantly different viralgenomes evolve over time. These are known as quasispecies.Production of quasispecies is likely to be important in the naturalhistory of hepatitis C infection, since diversification is believedto be one mechanism by which the virus escapes the immune responseof the host. Quasispecies differ from genotypes in that genotypesrepresent major genetic differences that vary in

geographicdistribution and epidemiologic associations, whereas quasispeciesrepresent minor genetic differences in an individual infected witha single genotype. Quasispecies change in an individual over time,whereas genotypes do not. Quasispecies can be measuredquantitatively (viral complexity) and qualitatively (viraldivergence over time) although such tests are not currentlyavailable as clinical tools. Clinical Significance of Quasispecies HCV quasispecies have a number of important implications forpracticing clinicians who treat HCV infection. A recent study1demonstrated that during acute HCV infection, isolates whichdeveloped little genetic diversity in a particular region of theviral genome were associated with self-limited hepatitis, whereasthe

development of persistent infection was associated with theevolution of greater genetic diversity in this region. Thus, thedynamics of quasispecies evolution during acute infection may be animportant determinant of host immune response and the future courseof infection. HCV variants also can be used to prove linkage ofinfections that are associated epidemiologically. For example,molecular analysis has been used to link mother/infant pairs, todefine HCV in apparently concordant sexual couples as virologicallyconcordant or discordant, to prove nosocomial transmission of HCVbetween health care provider and patient, and to link needle stickrecipients with the sources of infection.References Farci P, Shimoda A, Coiana A, et al. The outcome of acute hepatitisC predicted by the evolution of the viral quasispecies. Science2000;288:339-

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