Short Communication: Does Interleukin-28B Single Nucleotide Polymorphisms Influence the Natural History of Hepatitis B?

Abstract

Single nucleotide polymorphisms (SNP) nearby the IL28B gene have been associated with spontaneous hepatitis C virus (HCV) clearance and response to interferon-based therapies in both monoinfected and HIV-coinfected patients. However, its impact on spontaneous clearance of HBV (the pathogenesis of which is also related to interferon) is less known. A case-control study was performed. Cases were 49 HIV⁺ patients with chronic hepatitis B (HBsAg⁺ for more than 6 months) who had been genotyped for the rs12979860 SNP (protective CC genotype). One control for each case was chosen among HIV patients with anti-HBs and anti-HBc. Controls were matched for gender and coinfection with HCV. Most patients were male (90%) and the median (IQR) age was 42.6 (39–46.7) years. Eighteen (36.7%) were also coinfected by HCV. Among HBsAg⁺ patients, 19 (41.3%) were HBeAg⁺ and 13 (26.5%) were also infected with hepatitis delta (HDV). No differences were found in the distribution of the CC genotype between patients with chronic hepatitis B and those who spontaneously cured hepatitis B: 59.2% vs. 44.9%; p=0.3. Thus, the interleukin-28B (IL-28B) genotype does not seem to have a role in the development of chronic hepatitis B among HIV-infected patients.

S ingle nucleotide polymorphisms (SNPs) nearby the IL28B (interferon λ3) gene at chromosome 9 have recently been associated with spontaneous hepatitis C virus (HCV) clearance and response to interferon-based therapies in both HCV-monoinfected and HIV/HCV-coinfected patients.^1
–3 However, its impact on other viral infections such as hepatitis B (HBV) has been only scarcely explored so far.^4,5 Around 10% of adult HIV-infected individuals exposed to HBV develop chronic hepatitis B.⁴ Age of infection and severe immune-depression have been related to the development of chronic HBV hepatitis. By contrast, coinfection with HCV is related to spontaneous HBV clearance. As in HCV pathogenesis, endogenous interferons are involved in the clearance and persistence of HBV infection.^6

–9 Thus, IL28B SNPs might also be relevant to the outcome following HBV exposure.

We designed a case-control study comparing 1:1 patients with chronic hepatitis B and individuals who spontaneously had cleared HBV following exposure. All were HIV-positive, mainly represented by white patients exposed to HBV in adulthood following sexual contacts or intravenous drug use. Cases and controls were matched in terms of factors already known to influence HBV clearance, such as gender, age, and HCV exposure (anti-HCV seropositivity).^10,11 Then, the prevalence of the rs12979860 SNPs was examined in the two groups. Patients with serum anti-HBc alone were excluded, given the controversial significance of this serological pattern.¹² All patients were on regular follow-up at Hospital Carlos III, a reference HIV clinic in Madrid, Spain.

Chronic hepatitis B was defined by the presence of serum HBsAg for longer than 6 months. Controls were individuals displaying positive serum anti-HBs and anti-HBc. IL28B rs12979860 SNP genotyping was conducted in a blinded fashion on DNA extracted from peripheral blood mononuclear cells collected from each individual, using the 5′ nuclease assay with allele specific TaqMan probes, as previously described.^2,3 Comparisons between groups were performed using Chi-square or Fisher exact tests, as appropriate. All statistical analyses were performed using the SPSS software version 15.5 (SPSS Inc., Chicago, IL).

A total of 49 cases fit the inclusion criteria. Table 1 records the main characteristics of the study population, comparing cases and controls. Overall, 90% of subjects were male and had a median (IQR) age of 43 (39–47) years. The prevalence of anti-HCV antibodies was 37%. No significant differences were found in any of the considered variables when comparing cases and controls. In patients with chronic hepatitis B, 19 (41.3%) were positive for serum HBeAg and 31 (91.2%) had undetectable serum HBV-DNA, as a result of being exposed to antiretroviral drugs with activity against HBV, such as lamivudine, emtricitabine, and/or tenofovir. Coinfection with hepatitis delta virus was detected in 13 (26.5%) cases. The HBV genotype was available for 29 individuals, being A in 13, D in 11, G in 4, and A/E in 1.

Table 1.

Main Characteristics of the Study Population

Variable	Chronic hepatitis B (n=49)	Spontaneous HBV clearance (n=49)	p
Age (years)	42 (39–45)	45 (39–48)	0.1
Male gender	44 (90%)	44 (90%)	1
IDU	23 (49%)	21 (46%)	0.9
Anti-HCV⁺	18 (37%)	18 (37%)	1
On HAART	48 (98%)	44 (90%)	0.2
Undetectable plasma HIV-RNA	46 (94%)	44 (90)	0.4
HBV genotype
A	13 (45%)	NA
D	11 (38%)	NA
G	4 (14%)	NA
A/E	1 (4%)	NA
Undetectable serum HBV-DNA	31 (91%)	NAP
HBeAg⁺	19 (41%)	NAP
Anti-HDV⁺	13 (27%)	NAP
rs 12979860 IL28B genotype			0.3
CC	29 (59%)	22 (45%)	0.1
CT	17 (35%)	21 (42%)	0.9
TT	3 (6%)	6 (12%)	0.8

Continuous variables are given as median (interquartile range). Qualitative variables are given as absolute number (percentage).

IDU, intravenous drug user; HCV, hepatitis C virus; HDV, hepatitis delta virus; NA, not available; NAP, not applicable.

No significant differences in the distribution of IL28B rs12979860 genotypes were recognized when comparing chronic hepatitis B patients (CC 59.2%, CT 34.7%, and TT 6.1%) with individuals who had cleared HBV spontaneously (CC 44.9%, CT 42.9%, and TT 12.2%) (p=0.3).

Type I interferons (IFN-α and IFN-β) produce direct antiviral activity and are associated with a wide variety of immunomodulatory functions,⁷ which are important for the elimination of hepatitis viruses. IL28B (IFN-λ-3) resembles interferon alfa and activates similar intracellular pathways.⁸ Even more, IFN-λ has shown inhibition of HBV replication in a differentiated murine hepatocyte cell line and is currently undergoing evaluation as a potential new treatment for viral hepatitis.⁹ Considering all these findings, our original hypothesis argued for a potential influence of IL28B polymorphisms on HBV clearance. However, the results of our study did not confirm it, suggesting that IL28B may trigger distinct effects on immune responses against HCV and HBV infections. Considering that the probability of spontaneous control of HBV is much higher than that for HCV, even in patients with HIV infection, it is possible to speculate that the immune mechanisms responsible for the successful control of each of these two virus infections must be different.

Our data confirm the results observed in two recently published studies.^4,5 Martin et al. observed genotype CC in 41% and 44% of patients with HBV recovery and persistent infection, respectively. The prevalence of the CC genotype is higher in our series, probably reflecting the fact that most of our population was white. The C allele is less frequent among African subjects.^1,2

In summary, in contrast with what has been observed in chronic hepatitis C, IL28B rs12979860 SNPs do not seem to play a role in the spontaneous clearance of HBV.

Footnotes

Acknowledgments

We would like to thank all the patients who participated in the study. This work was supported in part by grants from Fundacion Investigacion y Educacion en SIDA (IES), the NEAT (European Union 6th Framework Programme, ref. LSHP-CT-2006-037570), Red de Investigacion en SIDA (RIS, FIS-RD06/0006), and Fondo de Investigación Sanitaria-FIS (CP08/00214).

Author Disclosure Statement

No competing financial interests exist.

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