Unlike the flu virus, which the body is generally able to fight off completely, infection with hepatitis C is often chronic.  That means for most of the three to four million people worldwide who are newly infected each year the virus will persist in the body, where it greatly increases risk for chronic liver diseases including cirrhosis and cancer. The only treatment currently available — an almost year long course of drugs — often causes severe side-effects. Worse yet, it fails in about half of all patients.

Last month, a study published online in the journal Nature showed that DNA variations in and around the IL28B gene influence whether a person chronically infected with the hepatitis C virus will fully respond to the standard treatment regimen. Now three new reports further support the importance of IL28B variations in the body’s response to hepatitis C, a finding that has implications for the future of hepatitis treatment and drug development.

An Australian group headed up by Vijayaprakash Suppiah analyzed the DNA of more than 800 people with European ancestry from Australia, the UK, Germany and Italy infected with hepatitis C.  They found that having one or two copies of the less-common G version of rs8099917, a SNP near the IL28B gene, doubled the odds that a person would fail to have a sustained response to treatment.

A group headed up by Yasuhito Tanaka studied 326 Japanese hepatitis C patients and also found that rs8099917 predicts whether or not a person will respond to treatment.  In this population, however, the effect was much greater.  Carrying a G increased the odds of treatment failure by at least twelve times.

“This SNP has such a strong association with response that, in combination with other parameters, genotyping it and other genetic variants should be a useful part of  clinical management,” write Suppiah et al., who along with Tanaka et al. published their results online this week in the journal Nature Genetics.

Another study, this one published online in Nature, found that variation near IL28B might be part of what allows a minority of people infected with hepatitis C to clear the virus naturally, without any treatment.

David Thomas and colleagues found that individuals with European or African ancestry were about three times more likely to spontaneously clear a hepatitis C infection if they carried two copies of the C version of rs12979860 than if they had CT or TT at this SNP.

Twenty-eight percent of the people with the CT or TT genotypes were able to fight off their hepatitis C infection without treatment, a number very close to the population average.  But 53% of those with the CC genotype were able to become naturally virus-free.

In a commentary published in Nature, Shawn Iadonato and Michael Katze express doubts about the importance of these new discoveries.

“Although these findings raise the tantalizing prospect of a more personalized approach to treating [hepatitis C] by tailoring treatment to patients who are most likely to benefit, the reality is more sobering,” they write.

Iadonato and Katze worry that testing for IL28B variations would not provide doctors with a straightforward yes-or-no answer to the question of whether a patient will respond to hepatitis C treatment.  This is because not all carriers of the advantageous versions of the variants clear the virus, nor do all patients lacking them fail to benefit from treatment.  Furthermore, they point out, there is currently no alternative hepatitis C treatment available.

What they do not consider, however, is how this new research may help change that. In a separate commentary in Nature Genetics, Thomas O’Brien suggests that the current findings could increase the interest in developing hepatitis therapies based on the protein encoded by IL28B, interferon-λ3.  He notes that an early clinical trial testing the effects of a related protein, interferon-λ1, has already had some success.  And certain properties of interferon-λs may cause them to have fewer side effects than current treatments.

O’Brien is still cautious about the findings linking IL28B variations to hepatitis C treatment response.  He says that more research in this area is needed in diverse populations and in people infected with different forms of hepatitis C.  He also stresses that researchers need to consider how these genetic findings fit in with other factors that affect treatment response, including age and gender.

Overall, however, his view is optimistic.  He concludes: “With these caveats, predictive models of HCV treatment response hold the potential to inform treatment decisions for millions of patients who are infected with HCV.”

(Rs12979860 was also described in the original paper linking IL28B to hepatitis C.  23andMe does not currently provide data for this SNP.  As pointed out in the previous Spittoon post on this topic, rs12980275 is very near to this SNP.  The A version of rs12980275 usually corresponds to the C version of rs12979860.  The other SNP discussed in this post, rs8099917, is located close to both rs12979860 and rs12980275.  23andMe customers can look up their data for rs8099917 using the Browse Raw Data feature.  Keep in mind that because all of these SNPs are so closely linked to each other, they are all probably representing the same effect.  More research will be needed to zero in on the exact variation(s) that are important for hepatitis C.)

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

Map: PhilippN

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The exact causes of Crohn’s disease remain a mystery, but scientists do know that genetic factors play an important part. More than 30 variations have been associated with increased risk for the disease, but changes in one gene, NOD2, have been found to be especially critical.  Three different variants in this gene have been associated with significantly increased risk for developing the disease.  It’s estimated that 10-15% of people with Crohn’s disease have two copies of one of these variants.

Because changes in NOD2 are associated with so many cases of Crohn’s disease, medications made to interact with the protein the gene encodes would seem to be obvious candidates for drug development.  But the NOD2 protein doesn’t have the type of function that can be modified by a drug.

A new avenue of drug research may have been opened, however, thanks to a study from Derek Abbott and colleagues at Case Western Reserve University.  In a paper appearing in the August issue of Current Biology, they show for the first time that a protein called ITCH can influence NOD2 biological pathways.  This is important because, in the parlance of pharmaceutical development, ITCH is a  “druggable” target.

NOD2 binds to bacteria that make their way into cells, setting off signals that activate the immune system. Research has shown that the Crohn’s disease-associated NOD2 variants decrease the signals that go through a particular protein called NFkB.  Abbott’s lab found that ITCH also decreases NOD2-dependent NFkB signals.  This is significant because studies have shown that increased NFkB signaling can help slow down the progression of Crohn’s disease.

“The thought is that if you could identify patients with NOD2 polymorphisms who also displayed early gastrointestinal trouble, you could block ITCH to increase NFkB signaling and not let the Crohn’s disease get to the acute stage,” Abbott said in an email.

Abbott and his fellow researchers are in the very early stages of looking for drugs that could be used to inhibit ITCH and possibly be useful in treating Crohn’s disease.  But the road to drug discovery is a long one.  ITCH interacts with many other proteins in cells and it’s not yet clear if blocking it would have unwanted effects on other important biological pathways. However, in the future this research could lead to a valuable drug against Crohn’s disease — at least for the 10 to 15% of patients who have variants that cause decreased NOD2 signaling.

(23andMe customers can check their data for three distinct NOD2 SNPs, as well as nine other Crohn’s disease associated variants, in the Crohn’s Disease Clinical Report.)

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Not surprisingly, there has been intense interest in the genetics of obesity in recent years.  Obesity is a major health problem, resulting in tens of thousands of premature deaths and billions of dollars in healthcare costs each year in the United States, and it is known from twin and family studies that weight is a highly heritable trait.

The genetic mutations and variations identified so far explain only a small percentage of the variability in body mass seen in the population.  Some exciting clues have been found, however, as to why some people are more prone to obesity than others and how this might be counteracted.  But new research, published online this week in the American Journal of Human Genetics, shows that caution must be taken in moving from genetic discoveries to drug development.

Variations in the FTO gene have consistently been associated with obesity. On average, people who carry two copies of the “risky” version of this gene weigh six to eight pounds more than those who carry none. Mice completely lacking the FTO gene were shown to be leaner than their normal littermates, despite being less active.  These results have led some to suggest that inhibiting the FTO protein with a drug could be a good for obesity treatment or prevention.

(23andMe customers can see their FTO data in the Obesity Research Report.)

But an international team of researchers led by Sarah Boissel of the Université Paris Descartes in France has found that a mutation that interferes with the function of the FTO protein is associated with a lethal genetic condition.  Members of a large, inbred Palestinian family born with two copies of this mutation had multiple developmental abnormalities and died before the age of three.  Based on their results, Boissel and her colleagues warn that any research exploring the use of FTO inhibitors as obesity treatments must include a “careful assessment” of the potential to cause birth defects and other toxic side effects.

More about FTO:

SNPwatch: Gene Variant Linked to Obesity Affects Food Choices in Children

It’s Not Genes or Environment, It’s Genes AND Environment

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