Distribution of interferon-alpha 2 genes in humans

Dendritic cells from HIV-1 infected individuals are less responsive to toll-like receptor (TLR) ligands

We compared TLR responsiveness in PBMC from HIV-1-infected and uninfected individuals using the TLR agonists: TLR7 (3M-001), TLR8 (3M-002), and TLR7/8 (3M-011). Activation and maturation of plasmacytoid dendritic cells (pDC) were measured by evaluating CD86, CD40, and CD83 expression and myeloid dendritic cell (mDC) activation was measured by evaluating CD40 expression. All agonists tested induced activation and maturation of pDC in PBMC cultures of cells from HIV+ and HIV- individuals. The TLR7 agonist induced significantly less pDC maturation in cells from HIV+ individuals. Quantitative assessment of secreted IFN-alpha and pro-inflammatory cytokines at the single cell level showed that pDC from HIV+ individuals stimulated with TLR7 and TLR7/8 induced IFN-alpha. TLR8 and TLR7/8 agonists induced IL-12 and COX-2 expression in mDC from HIV+ and HIV- individuals. Understanding pDC and mDC activation and maturation in HIV-1 infection could lead to more rational development of immunotherapeutic strategies to stimulate the adaptive immune response to HIV-1.

Lymphoblastoid interferon alfa-n1 improves the long-term response to a 6-month course of treatment in chronic hepatitis C compared with recombinant interferon alfa-2b: results of an international randomized controlled trial. Clinical Advisory Group for the Hepatitis C Comparative Study

The aim of this study was to compare the short-term and long-term efficacy and safety of lymphoblastoid interferon with a recombinant interferon alfa (IFN-alpha) in a 24-week treatment course for chronic hepatitis C. One thousand seventy-one patients with chronic hepatitis C were randomized to receive lymphoblastoid IFN-alpha n1 or recombinant IFN-alpha2b at the same dosing regimen, 3 million units administered subcutaneously three times a week for 24 weeks. Hepatitis C viral (HCV) genotype (by line probe assay) was determined at baseline, and serum HCV RNA level (by quantitative reverse-transcriptase polymerase chain reaction) was measured at baseline and weeks 24, 48, and 72. Primary end points were normalization of serum alanine aminotransferase (ALT) levels at end of therapy (week 24) and sustained ALT normalization at weeks 48 and 72. Secondary end points were nondetectability of serum HCV RNA at 24, 48, and 72 weeks, and histological improvement at weeks 24 and 72. The two treatment groups were similar with respect to demographic, clinical, and histological variables (10% had cirrhosis at entry), baseline serum HCV RNA levels, and distribution of HCV genotypes. Intent-to-treat analysis showed that ALT response at end of treatment was 35.3% for IFN-alpha n1 and 37.9% for IFN-alpha2b (P = .38). Histological improvement and nondetectability of HCV RNA were also similar between the two treatment groups at the end of treatment, as were the type and frequency of reported adverse experiences. Among treatment responders, post-treatment relapse was significantly less frequent with IFN-alpha n1 than with IFN-alpha2b. Thus, sustained ALT responses (SR) to IFN-alpha n1 were significantly more frequent than SR to IFN-alpha2b (12.0% vs. 7.6% at 48 weeks, P = .02; 10.3% vs. 6.7% at 72 weeks, P = .04). SR were associated with viral loss and histological improvement, and more patients treated with IFN-alpha n1 were HCV RNA negative at week 72 compared with patients treated with IFN-alpha2b (P = .03). SR at week 72 were two- to sixfold better with other HCV genotypes relative to type 1, but the improved long-term efficacy of IFN-alpha n1 compared with IFN-alpha2b was evident for all major HCV genotypes. It is concluded that IFN-alpha n1 and IFN-alpha2b have similar end-of-treatment response rates and safety profiles but the sustained response rate is higher with IFN-alpha n1. SR to IFN-alpha treatment are associated with clearance of HCV RNA, and histological improvement was maximal in patients who exhibited sustained ALT normalization and clearance of HCV RNA.

Novel variants of human IFN-alpha detected in tumor cell lines and biopsy specimens

Interferon-alpha constitutes a complex gene family with 14 genes clustered on the short arm of chromosome 9. More than 50 sequence variants have been described. However, an extensive genetic polymorphism has not been seen in the few population studies reported so far. As many of the sequence variants reported were derived from tumor cell lines, we have investigated whether IFN-alpha genes are unstable in tumor cells. Using fluorescence-assisted mismatch analysis (FAMA), combined with allele-specific primer extension, RFLP analysis, and direct sequencing, we detected in a panel of 14 tumor cell lines two new sequence variants of the IFNA1 and IFNA13 genes. Further two-point mutations were found in tumor samples from leukemias (n = 10) and renal cell carcinomas (n = 17) not seen in normal tissues. In the IFNA17 gene, three new sequence variants were detected, one in a tumor cell line and two in tumor biopsy specimens. Besides these individual point mutations, two new polymorphisms were found in each of the IFNA13 and IFNA17 genes. No new variants were found in the IFNA2 and IFNA10 genes. The results suggest that new sequence variants of the IFN-alpha genes occur relatively frequently in tumors or in tumor cell lines.

Determination of interferon-alpha2 allele composition in the genomic DNA from healthy volunteers and leukemic patients in Japan

The three interferon-alpha2 (IFN-alpha2) sequences identified to date differ from each other in just two nucleotide positions, both of which result in changes in amino acids. Thus, the mature IFN-alpha2a protein product is characterized by a lysine residue at position 23 (AAA) and a histidine at position 34 (CAA), IFN-alpha2b has an arginine at position 23 (AGA) and histidine at position 34 (CAT), and IFN-alpha2c has arginine residues at both positions 23 (AGA) and 34 (CGT). These nucleotide variations in the DNA sequence can be distinguished by selective restriction enzyme analysis. We studied the distributions of the three IFN-alpha2 variants by analyzing chromosomal DNA from 103 Japanese volunteers and 33 patients with hematologic disorders. Fragments of 238 bp and 617 bp of the IFN-alpha2 gene containing codons 23 and 34 were amplified by PCR using specific primers, and the PCR products were analyzed with specific restriction nucleases to identify the IFN-alpha2 variant sequences. Only IFN-alpha2b gene was detected in normal volunteers, and no IFN-alpha2a gene was detected in Japanese subjects. However, IFN-alpha2c was detected in 4 of 33 (12.1%) patients with leukemia.

Epitopes recognized by neutralizing therapy-induced human anti-interferon-alpha antibodies are localized within the N-terminal functional domain of recombinant interferon-alpha 2

During prolonged recombinant interferon (rIFN)-alpha 2 therapy, a minority of patients develop high-titer neutralizing IFN-alpha antibodies. Sera from nine IFN-alpha antibody-positive patients were studied to characterize the specificity of anti-IFN-alpha neutralizing antibodies by their ability to inhibit the antiviral and antiproliferative activity of different rIFN-alpha subtypes and rIFN-alpha 1/alpha 2 hybrids. These therapy-induced antibodies (Tab) were compared with IFN-alpha-specific autoantibodies (Aab) from two patients with systemic lupus erythematosus who had never received any exogenous IFN-alpha. Although IFN-alpha subtypes are closely related in structure, Tab inhibited the antiviral activity of only recombinant (r)IFN-alpha 2 and rIFN-alpha 6, but not or slightly that of rIFN-alpha 1, -alpha 7, -alpha 8 and -alpha 14. Furthermore, of four different rIFN-alpha 1/alpha 2 hybrids tested, Tab inhibited only those which contained the N-terminal residues 17-64 of rIFN-alpha 2. Comparison of the primary sequences of neutralized and not neutralized subtypes suggests an epitope involving the residues 22-31 of IFN-alpha 2 is recognized. Thus, Tab block rIFN-alpha 2 by reacting with only one of two functional domains. In contrast, Aab possessed a broad specificity and neutralized both the antiviral and antiproliferative activity of rIFN-alpha 2, -alpha 6, -alpha 7, -alpha 8, and -alpha 14. They also neutralized all four rIFN-alpha 1/alpha 2 hybrids tested. These data demonstrate that Tab are highly specific for the therapeutic IFN-alpha subtype and specifically neutralize rIFN-alpha 2 by binding to its N-terminal functional domain.

Interferon-alpha 8b is the only variant of interferon-alpha 8 identified in a large human population

Three variants of human interferon (IFN)-alpha 8a gene, that is, IFN-alpha 8b, and IFN-alpha 8c, have been reported previously. They differ from each other by changes in their coding region at nucleotide positions 359-360, 372, and 550. Human genomic DNA obtained from over 28,000 healthy blood donors and from 4 human cell lines was used in the polymerase chain reaction (PCR) designed for specific amplification of the IFN-alpha 8 gene fragments. The resulting PCR product was analyzed by (1) restriction endonuclease digestion, (2) DNA sequencing, and (3) allele-specific secondary PCR amplification. Only one sequence for IFN-alpha 8 was identified, and that was for IFN-alpha 8b. The sequences for IFN-alpha 8a and IFN-alpha 8c were not detected after PCR amplification either in the pooled leukocytes obtained from > 28,000 individuals or in cell lines tested. These data suggest that the naturally occurring variant or allele for IFN-alpha 8 in the population is IFN-alpha 8b. IFN-alpha 8a and IFN-alpha 8c variants were consistently below the level of detection of the assays and, if present at all in the population, are very rare.