Genotypes (genetic variants) which can affect hepatitis C treatment are of two kinds, HUMAN and VIRAL:
- Human genotypes are HUMAN genetic variants. For example, the type of IL28B ‘allele’ or genetic variant a person has on one part of their DNA is an important predictor of success with interferon-ribavirin treatment. More info on IL28B HERE.
- HCV genotypes are VIRAL genetic variants of the hepatitis C VIRUS. There are 6 main HCV genotypes (1-6).** Each of these has subtypes as well. Genotypes 1-3 are the most common in the Americas, Europe, and Australia. Genotype 4 is very common in North Africa, Genotype 5 is prevalent in South Africa, and some Genotype 6 is seen in Asia (extremely rare in other parts of the world, except among Asian immigrants). The most common types of hepatitis C in the world are: 1a, 1b, 1c, 2a, 2b, 2c, 3a, 3b, 4, and 5. Genotype 1 (a,b,c) is the most difficult to treat — and the most common in the West — while 3a has the best response rate to interferon. It is extremely important to get tested for genotype as this determines which sort of treatment you will get and how long you will need to be on it.
** Update (Dec 2017): According to a study presented at AASLD 2017, there are now 8 known genotypes and 84 subtypes, all of which respond to Vosevi.
(1) Global Distribution of HCV Genotypes – Click here for enlarged version.
Physicians have noted that people of different ethnic and racial groups seemed to respond differently to HCV in terms of how frequently their bodies were able to clear the virus spontaneously, or how well they responded to interferon/ribavirin treatment.
- This difference was irrespective of lifestyle, gender or age. Then scientists discovered that individuals with a particular gene variation, called the “IL28B allele,” respond differently to HCV. Finally they understood that the different ethnic and racial responses to HCV they’d observed could be explained by the different % of the “IL28B allele” within each of the various groups.
- As shown in the chart below, East Asians have the greatest % of the most positive IL28B allele, African Americans have the least %, while Caucasians and Hispanics are somewhere in the middle. This is a direct predictor of each racial group’s response to interferon/ribavirin treatment.
- While the IL28B allele may be a strong predictor of how an individual might respond to treatment with interferon/ribavirin, it is unknown if IL28B will be a factor with the new protease and polymerase inhibitors, or the new treatments without Interferon or Ribavirin. Who knows? There may be other alleles that affect success of the new treatments. Stay tuned.