Interleukin-28B (IL28B)/interferon-λ3 (IFN-λ3) belongs to the IFN type III family, shares functional characteristics with IFN type I  and induces in-vitro protection against hepatitis C virus (HCV) infection . Although several studies have demonstrated a role for single nucleotide polymorphisms (SNPs) nearby the IL28B gene on the spontaneous clearance [3,4], as well on the treatment-induced elimination [4–8] of HCV, it is currently unknown whether IL28B polymorphisms might similarly influence the outcome of other viral infections.
Although, in HIV-1, there is no evidence for spontaneous or treatment-induced cure, a subset of infected individuals, named long-term nonprogressors (LTNPs), demonstrate an intrinsic ability to control HIV-1 replication and defer immunodeficiency in the absence of antiretroviral therapy . Moreover, evidence exists on another subset of individuals who despite being exposed to HIV remain persistently HIV-negative (exposed seronegative, ESN) . A number of studies have been conducted in these special groups to ascertain whether potential immune mechanisms might account for their protection against HIV infection and/or disease progression [10,11]. Given the in-vitro antiviral effect of IFN-λ on HIV replication , it is important to examine the role of IL28B polymorphisms on HIV infection.
Separate cross-sectional case–control studies were conducted in two different well characterized cohorts of patients. The first cohort ‘HIV disease progression’ included 68 individuals with chronic HIV infection in regular follow-up at Hospital Carlos III, Madrid. The second cohort ‘HIV protection’ included 29 HIV-serodiscordant sexual couples who attended Centro Sandoval, a sexually transmitted diseases clinic located in Madrid. To participate in the study, written informed consent for genetic testing was obtained from all individuals. The study protocol was evaluated and approved by the hospital ethics committee. Both plasma and peripheral blood mononuclear cells were drawn and stored for all patients.
IL28B rs12979860 SNP genotyping was conducted on DNA specimens using the 5' nuclease assay with allele-specific TaqMan probes (ABI TaqMan allelic discrimination kit, Applied Biosystems, Carlsbad, California, USA) and the ABI7900HT Sequence Detection System (Applied Biosystems) . The main characteristics of the study population and the different parameters evaluated are expressed as median (interquartile range). Comparisons between groups were carried out using the χ2-test or Fishers's exact test, as appropriate. All statistical analyses were performed using the SPSS software version 13 (SPSS Inc., Chicago, Illinois, USA). All P-values were two-tailed, and were considered as significant only when below 0.05.
The HIV disease progression cohort included 30 LTNPs (cases) and 38 typical progressors (controls). All LTNPs were infected for more than 15 years, had plasma HIV-RNA values below 10 000 copies/ml and always had CD4 cell counts above 500 cells/μl in the absence of highly active antiretroviral therapy. Typical progressor patients were naive to antiretroviral therapy and their median CD4 cell counts were 422 (238–480) cells/μl. Overall, 57% were co-infected with HCV (73% of LTNPs vs. 45% of typical progressors).
The HIV protection cohort  included 29 HIV-ESN individuals (cases) and 29 HIV-infected partners (controls). Median CD4 cell count in HIV-infected partners was 496 (207–705) cells/μl and length of infection was 108 (30–188) months. At inclusion, 65% (19/29) of them had undetectable plasma viremia, ranging in the remaining 10 patients from 68 to 238 131 HIV-RNA copies/ml. Thirty-eight percent of ESN were co-infected with HCV. Fifteen (52%) ESN admitted never using condoms, nine (31%) sporadic use, and five (17%) frequent use. Considering risk behaviours and viral load of HIV-infected partner, ESN were divided into those with low (19; 65%) or moderate-high (10; 35%) level of HIV exposure.
Both cohorts, HIV disease progression and HIV protection, were in Hardy–Weinberg equilibrium, with a C allele frequency of 70 and 72%, respectively. The prevalence of rs12979860 genotypes in the HIV disease progression cohort was CC 50%, CT 40%, and TT 10%. The distribution of IL28B polymorphisms was similar in LTNPs and typical progressors (CC genotype was present in 54 and 47%, respectively, P = 0.63; Table 1). The prevalence of IL28B rs12979860 genotypes in the HIV protection cohort was CC 54%, CT 36%, and TT 10%. Although the distribution of the different IL28B genotypes did not differ significantly between ESN and their HIV-positive partners, the prevalence of the CC genotype tended to be greater in ESN than in their HIV-positive partners (62 vs. 45%, respectively; P = 0.19; Table 1).
The IL28B rs12979860 SNP is one of the most important discoveries of a genetic trait associated with control of a chronic viral infection. The fact that this SNP is located 3 kb upstream the IL28B/IFN-λ3 gene  and that IFN-λ is known to mediate anti-HIV-1 activity  might provide the basis for implicating a role of innate immunity against both HCV and HIV infections. Our results, however, do not support a role for this IL28B SNP in the protection from HIV disease progression in infected persons, as the prevalence of the protective genotype (CC) was similar in LTNPs and typical progressors. Likewise, the IL28B SNP does not seem to confer any protection against HIV acquisition, as the prevalence of the CC genotype did not differ significantly in ESN and their HIV-positive partners.
IFN-λ exerts bioactivities that overlap those of type I IFNs, such as antiviral activity  and upregulates the intracellular expression of type I IFNs and APOBEC3G/3F, a well known anti-HIV-1 cellular factor . Thus, it is somewhat unexpected that the IL28B SNP did not significantly influence HIV control, whereas the effect has shown to be quite strong on HCV infection. Therefore, large differences in the control of HCV and HIV infections may exist. The biological mechanisms involved in the association of the IL28B SNP over HCV control are still unclear. Although the CC genotype might modulate the regulation of IL28B protein expression, and in this way influence innate immunity, in spite of the previously reported IFN-λ-mediated anti-HIV-1 activity , we did not find any significant association between IL28B polymorphisms and HIV disease progression nor HIV protection. Thus, the biological mechanisms underlying the association of the IL28B SNP with HCV control could be other than the direct IL28B-mediated antiviral activity. Alternatively, different mechanisms might be operating in vivo in the control of HCV and HIV infections.
This work was supported in part by grants from Fundación Investigacion y Educacion en SIDA (IES), Red de Investigacion en SIDA (RIS, FIS-RD06/0006), Agencia Lain Entralgo and the European Union 6th Framework Programme (NEAT, LSHP-CT-2006- 037570).
The authors would like to thank all patients who participated in the study.
N.I.R., V.S., J.M.B., S.N., and J.McH. designed the study. N.I.R., C.R., J.M.B., and M.L. did the virological studies and collected the specimens. N.I.R., C.R., D.G. and J.McH. performed SNP genotyping. V.S. and J.R. were responsible for and analysed the demographics, clinical and therapeutic information of the study population. N.I.R., J.M.B., V.S., S.N. and J.McH. wrote the manuscript draft. All authors revised and approved the final submission.
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