Stimulation of human peripheral blood lymphocytes by bioactive peptides derived from bovine milk proteins

The in vitro modulation of the proliferation of human peripheral blood lymphocytes by different synthetic peptides derived from milk proteins was investigated. Therefore, proliferation changes were followed up after incorporation of BrdU into the DNA, and the influence on protein biosynthesis was measured using the [3H]leucine incorporation test. Tyr-Gly and Tyr-Gly-Gly significantly enhanced (maximal 90 and 35%, respectively) the proliferation of PBL. For beta-casomorphin-7 and beta-casomorphin-10,lymphocyte proliferation was suppressed at lower concentrations, but stimulated at higher concentrations (> or = 10(-7) mol/l). Protein synthesis was stimulated (maxima at 25%) only with Tyr-Gly and Tyr-Gly-Gly. The findings point to a need for further studies on the possible function of peptides derived from milk proteins as orally bioavailable immunopotentiatory compounds.

Rational use of diagnostic tools in hepatitis C

Six years after the introduction of serological tests for the detection of antibodies to HCV these diagnostic procedures have been improved significantly. The ELISA's of the third generation contain 4-5 fragments of structural and nonstructural proteins which have increased the sensitivity and specificity for antibody detection. Several confirmatory assays have been established to detect non-specific reactions. Viremia in acute and chronic HCV infection can be detected by RT-PCR. However, studies on the quality of PCR results with serum panels in a large number of diagnostic labs indicate the urgent need to standardize the RT-PCR techniques. Quantification of viral genomes during acute and chronic HCV infection seem to be of major importance to predict the response rat to IFN. Quantitative RT-PCR techniques using internal standards and the branched DNA technology have been established. Techniques for genotyping HCV isolates have been introduced which also seemed to be important for prediction of IFN response. Recently serotyping of HCV isolates has been evaluated and seems to correlate well with genotyping by RT-PCI and specific probes. The detection of quasispecies in the 5'NCR may, in the future, be an additional prospective test for the prognosis of IFN treatment.

Coding strategy of the S and M genomic segments of a hantavirus representing a new subtype of the Puumala serotype

The hantavirus strain Vranica was previously reported to have been isolated from a bank vole in Bosnia-Hercegovina and associated with the occurrence of hemorrhagic fever with renal syndrome (HRFS) in humans. The complete cDNA nucleotide sequences of the small (S) and medium (M) genomic RNA segments of this virus were determined. Major open reading frames were found in the S and M segment between nucleotide positions 43 and 1341 coding for a polypeptide of 433 amino acid residues and between nucleotide positions 41 and 3,484 coding for 1,148 amino acid residues, respectively. The analysis and the alignment of the nucleotide and the derived amino acid sequences with known sequences of other hantavirus strains demonstrate that Vranica resembles Swedish strains and represents a new virus subtype of the Puumala serotype distinct from the subtypes represented by virus strains CG18-20 and Sotkamo.

Genetic characterization of a new hantavirus detected in Microtus arvalis from Slovakia

A new hantavirus, called Malacky, has been identified in lung tissue specimens of a vole, Microtus arvalis, by the reverse transcriptase polymerase chain reaction (RT-PCR). The voles were trapped in a geographical area in Slovakia where hemorrhagic fever with renal syndrome (HFRS) is endemic in the human population. Sequence analysis of a major part of the S segment showed this virus to represent a new subtype within Tula, a new hantavirus genetic group defined very recently.

A novel method for efficient amplification of whole hepatitis B virus genomes permits rapid functional analysis and reveals deletion mutants in immunosuppressed patients

Current knowledge of hepatitis B virus (HBV) sequence heterogeneity is based mainly on sequencing of amplified subgenomic HBV fragments. Here, we describe a method which allows sensitive amplification and simplified functional analysis of full-length HBV genomes with or without prior cloning. By this method, a large number of HBV genomes were cloned from sera of six immunosuppressed kidney transplant patients. Two size classes of HBV genomes, one 3.2 kb and another about 2.0 kb in size, were found in all patients. The genome population from one serum sample was studied in detail by size analysis of subgenomic PCR fragments and sequencing. Regions with deletions and insertions were mapped in the C gene and pre-S region. Up to 100% of HBV genomes in all other immunosuppressed patients also had deletions in the C gene. Our results demonstrate the potential of the established method for the structural and functional characterization of heterogeneous populations of complete virion-encapsidated HBV DNAs and suggest that HBV genomes with C gene deletions can have a selective advantage in immunosuppressed patients.

Transmission of hepatitis C virus to children and husbands by women infected with contaminated anti-D immunoglobulin

In 1978-79 a single-source outbreak of hepatitis C occurred in 2533 women who had received virus-contaminated anti-D immunoglobulin. Children and husbands of 74 women with self-limited, and of 86 women with chronic, hepatitis C were followed up for over 10-15 years. In 3 of 231 investigated children (1.3%) serological evidence for HCV infection was found. However, none of the children developed an apparent or chronic hepatitis. Serum samples of the 94 husbands investigated showed no HCV antibodies or HCV RNA. We consider the risk of intrauterine or perinatal transmission of HCV, as well as that of transmission through close family contacts, to be low. No evidence was found for sexual transmission for women to men.

Seroprevalence of hantavirus antibodies in Germany as determined by a new recombinant enzyme immunoassay

In order to elucidate the epidemiological importance of hemorrhagic fever with renal syndrome in Germany, the prevalence of antibodies against hantaviruses was determined in 13,358 sera from residents of various geographic regions, 1,284 sera from occupational risk groups and 287 sera from chronic hemodialysis patients. Serological investigations were performed using a highly specific transferable solid phase enzyme immunoassay based on the recombinant nucleocapsid proteins of a Hantaan and a Puumala serotype strain. The overall antibody prevalence was found to be 1.68%. In the serum panels from western and southern Germany, it was determined to be 1.83% on average in contrast to only 0.8% in the panel from eastern Germany. An endemic focus revealing an antibody prevalence of 3.12% was detected in a low-mountain area called Suebian Alb, which is located in the federal state of Baden-Württemberg. Occupational risk groups and a group of chronic hemodialysis patients showed a significantly elevated antibody prevalence ranging from 3.3% to 10%. The Puumala serotype was found to be the prevailing virus, but the percentage of sera predominantly recognizing the Hantaan nucleocapsid protein increased towards the south and the east and was significantly elevated in dialysis patients.

Bioactive peptides derived from milk proteins. Structural, physiological and analytical aspects

The primary function of dietary proteins is to supply the body adequately with indispensable amino acids and organic nitrogen. Little attention has been paid up to date to milk proteins, in particular caseins, that are currently the main source of biologically active peptides, although other animal as well as vegetable proteins are known to contain potentially bioactive sequences. Such regulatory peptides can be released by enzymatic proteolysis of caseins in vitro and in vivo and may act as potential physiological modulators of metabolism during the intestinal digestion of the diet. It has been proved that bioactive peptides derived from caseins, such as beta-casomorphins and phosphopeptides, can be released during gastrointestinal passage. It is also evident that peptides originating from food proteins should be taken into account as potential modulators of various regulatory processes in the body. The possible regulatory effects concern nutrient uptake (phosphopeptides, casomorphins), postprandial hormone secretion (casomorphins), immune defense (immunopeptides, casokinins, casomorphins) and neuroendocrine information transfer (casokinins). The advances in the research field of bioactive peptides are driven by a molecular understanding of biological processes, and analytical techniques are a critical component of this understanding. Different up-to-date methods, including peptide synthesis and immunochemistry, have been applied to the chemical characterization of bioactive peptides. Especially casein derived peptides have already found interesting applications, both as dietary supplements (phosphopeptides) and as pharmaceutical preparations (phosphopeptides, beta-casomorphins). The question of 'what kinds of bioactive peptides are beneficial and desirable as food constituents or as drugs' should be always carefully examined. However, the possibilities for the design of dietary products and 'natural' drugs look promising.

Antibodies from egg yolk of immunized hens against a bioactive caseinopeptide (beta-casokinin-10)

Antibodies (IgY) directed against a synthetic, bioactive peptide (beta-casokinin-10) were obtained from egg yolk of immunized chickens. Using a beta-casokinin-10/BSA conjugate for immunization, large quantities of high-titered anti-peptide antibodies were obtained. ELISA standard curves for beta-casokinin-10 were linear in the range 30-22,000 ng/ml. IgY-antibodies against beta-casokinin-10 recognized not only the immunogenic peptide structure but also analogues epitopes in protein preparations containing bovine beta- and alpha s-caseins, respectively, as well as in ovine caseins. The anti-beta-casokinin-10 IgY-antibodies are intended to be used as immunochemical reagents in future structure-activity studies of bioactive casokinins that are inhibitors of the angiotensin-converting enzyme.

Comparison of three different recombinant hepatitis B virus core particles expressed in Escherichia coli

The properties of three different recombinant hepatitis B virus core proteins expressed in Escherichia coli were compared: an N-terminal fusion protein, a C-terminally truncated protein and a sequence-authentic protein. All three proteins assembled into capsid-like particles with typical HBc-antigenicity, sedimentation behavior and distinctive electron microscopical images. Apart from this, however, variant HBc proteins displayed properties different from sequence-authentic HBc protein p21.4. Unlike p21.4, the particles of the N-terminal fusion protein p22.2 were sensitive to proteolytic attack by trypsin at variable sites within its arginine-rich C-terminus but not in its extended N-terminus. We therefore conclude that the C-terminal region is located on the surface of the p22.2 particle. These particles also showed increased HBe-antigenicity, as did the C-terminally truncated core particles p17.6, and to an even greater extent p18* particles which were derived from p22.2 by tryptic digestion. This might be interpreted as evidence for an--albeit minor--structural change. All variant core particles were less stable and contained less RNA. Electron microscopic indication for DNA binding of C-terminal deleted p17.6 particles was obtained using an aqueous spreading technique.

Fine mapping and functional characterization of two immuno-dominant regions from the preS2 sequence of hepatitis B virus

A set of monoclonal antibodies (mAbs) directed against the preS2 region of hepatitis B virus (HBV) surface antigen (HBsAg) was generated by immunization of mice with native HBsAg isolated from the blood of HBV carriers. According to (1) mutual competition binding of mAb to natural HBsAg, (2) recognition of full-length preS2 displayed on hepatitis B core particles, (3) recognition of synthetic partial preS2 peptides, and (4) Western blotting using a fusion protein library of truncated preS2 fragments of different legths, mAbs were assigned to two groups which coincided with groups I and III described by Mimms et al. [Virology 1990; 176:604-619]. All mAbs recognized linear epitopes and were glycosylation independent. Six out of eight fine-mapped mAbs recognized common epitopes located in the amino-terminal part of the preS sequence between amino acids 131 and 144 (group I), and inhibited binding of HBsAg to polymerized human serum albumin. Only two mAbs recognized a carboxy-terminal HBV-genotype-specific epitope covering amino acid residues 162 to 168 (group III). These mAbs bound to the highly variable proteolysis-sensitive hinge of preS2. Although four out of six mAbs targeted to immunodominant region I require the full-length sequence 131-L[Q/L]DPRVRGLY[F/L]PAG-144, two mAbs recognize the shorter and slightly carboxy-terminal-shifted sequences 133-DPRVRGLY[F/L]-141 or 135-PVRGLY[F/L]PAG-144. Together with previously identified preS2 epitopes 133-DPRVRGL-139, 137-RGLYFPA-143, and 132-QDPR-135, these data indicate diversity of the immune response against epitopes within the same immunodominant region. This diversity may be generated by a labile secondary structure. Sequence analysis suggests the transition from an alpha-helix to a loop structure at this site.

Heterogeneity of hepatitis B virus C-gene sequences: implications for amplification and sequencing

Occasionally direct sequencing of amplified hepatitis B virus DNA leads to weak signals on autoradiograms. Using amplified C-gene sequences we investigated whether this is due to sequence heterogeneity of virus populations and use of inappropriate primers for direct sequencing. High C-gene sequence heterogeneity (point mutations, stop codons and a one codon deletion) was observed in HBV genomes from serum of a chronic carrier who underwent interferon treatment. The type of C-gene mutations detected by direct sequencing depended on the type of primers used. Cloning and sequencing of amplified C-gene sequences demonstrated that this was due to mutations in the region complementary to the sequencing primer. These data demonstrate the existence of novel HBV C-gene mutants and imply that multiple or degenerate sequencing and amplification primers are essential for accurate evaluation of the extent of HBV C-gene heterogeneity. Based on comparative sequence analysis of all available completely or incompletely sequenced C-genes, guidelines for optimal primer design are proposed for similar studies.

Low dose alpha interferon treatment in chronic hepatitis B virus infection

Fifty eight patients with chronic viral hepatitis B (HBV) were randomised in a prospectively controlled trial. Thirty patients were treated with 3 million units (MU) of interferon alfa-2b subcutaneously thrice weekly for four months. Twenty eight controls received no treatment. The follow up period after treatment was six months. Twenty eight treated patients and 27 controls completed the protocol. One woman in the treatment group showed a complete response, and eight other treated patients (32%) showed a partial response. Three patients in the control group (11%) lost hepatitis B e antigen and HBV-DNA spontaneously. This finding is statistically significant (p < 0.05). The elimination of HBV markers from the serum was associated with a return to normal of serum aminotransferase activities. Reactivation of hepatitis was not observed after seroconversion.

Frequent and rapid emergence of mutated pre-C sequences in HBV from e-antigen positive carriers who seroconvert to anti-HBe during interferon treatment

Hepatitis B virus (HBV) variants which cannot express e-antigen (HBeAg) are characteristic for many viremic anti-HBe positive chronic carriers who often have particularly severe and fluctuating hepatitis. Whether such variants are selected for and are less amenable to interferon treatment is under dispute. Therefore, by DNA amplification and direct sequencing we have investigated the emergence of HBV pre-C sequence variants in nine e-antigen positive chronic carriers, all of whom seroconverted to anti-HBe or lost HBeAg during interferon treatment, and in three of whom no viral DNA was detectable after interferon treatment. In most, but not all of the patients we found newly emerging pre-C sequences in a subpopulation of the viral genomes that included silent point mutations, amino acid changes, start and stop codon and frameshift mutations. The emergence of these mutations was paralleled by a drastic decrease of viremia during treatment. The observed mutations appeared most frequently during interferon treatment. Some of the mutations appeared or disappeared late after interferon treatment concomitant with anti-HBe antibody development. The appearance or lack of mutations in the pre-C region of a subpopulation of HBV of these patients was independent of successful virus elimination. These data indicate that interferon treatment is frequently associated with the simultaneous fall in titer of viral DNA by several orders of magnitude and the emergence of novel pre-C sequences, some of them preventing HBeAg expression. However, the presumably immune-mediated selection for pre-C mutant viruses and decrease in viremia under interferon treatment appears not to be prognostic for successful or unsuccessful virus elimination.

Heat-induced changes in casein-derived phosphopeptides

Phosphopeptides derived from casein may function as carriers for calcium and trace elements. In regard to such specific nutritive effects, the heat-induced changes in tryptic phosphopeptides liberated from bovine sodium caseinate as a model system were investigated. Both microwave and oven heating resulted in a marked loss of peptide-bound phosphorous (dephosphorylation) and a decrease of casein-phosphopeptides in the soluble part of the tryptic hydrolysate. It is concluded that hydrolysis of phosphoseryl to seryl residues was the prevailing degradation step to soluble proteolytic products, whereas lysinoalanyl-casein is claimed to be present almost exclusively in the pH 4.6-insoluble part of the tryptic digest.

Comparative inhibition of hepatitis B virus DNA polymerase and cellular DNA polymerases by triphosphates of sugar-modified 5-methyldeoxycytidines and of other nucleoside analogs

Of a series of 14 nucleoside 5'-triphosphates, those of 2',3'-dideoxy-3'-fluoro-5-methylcytidine, 3'-azido-2',3'-dideoxy-5-methylcytidine, 2',3'-dideoxy-3'-fluoroguanosine, 2',3'-didehydro-2',3'-dideoxy-5-methylcytidine, 2',3'-dideoxy-3'-fluoro-5-ethylcytidine, and 2',3'-dideoxy-3'-fluoroadenosine emerged as the most potent inhibitors of hepatitis B virus DNA polymerase (50% inhibitory dose, 0.03 to 0.35 microM). In contrast, cellular DNA polymerases proved to be resistant to (alpha) or partially affected by (beta) these analogs. These compounds are among the most effective and selective inhibitors of endogenous hepatitis B virus DNA polymerase recognized to date.

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[Treatment of chronic hepatitis B with interferon alpha-2b]

In a prospective randomized trial 58 patients (46 men, 12 women; mean age 41 [18-65] years) with histologically proven chronic hepatitis B and demonstration of HBs antigen and hepatitis B virus DNA in serum were randomly divided into two groups: 30 patients were treated with recombinant alpha 2b interferon. The interferon was administered subcutaneously, 3 x 10(6) IU, three times weekly for four months. 28 patients served as untreated controls. There was a six-month post-treatment follow-up. Two patients in the treatment group and one in the control group had to be excluded later. In the treatment group one patient responded completely (HBs antigen, HBe antigen and HBV-DNA negative) and eight partially (HBe antigen and HBV-DNA negative). In three patients of the control group, HBe antigen and HBV DNA were no longer demonstrated (P less than 0.05). The loss of HBV features was associated with normalization of serum transaminases activity. Reactivation of liver inflammation after seroconversion was not observed.

Inhibition of hepatitis B virus DNA polymerase by 3'-fluorothymidine triphosphate and other modified nucleoside triphosphate analogs

The 3'-fluoromodified nucleotide analogs 3'-fluorothymidine triphosphate (FdTTP), 2',3'-dideoxy-3'-fluoro-5-chlorouridine triphosphate (F-5CldUTP), 2',3'-dideoxy-3'-fluoro-5-ethyluridine triphosphate (F-5EtdUTP), 2',3'-dideoxy-3'-fluorouridine triphosphate (FdUTP), and 2',3'-dideoxy-3'-fluoro-5-fluorouridine triphosphate (F-5FdUTP) as well as 2',3'-dideoxythymidine triphosphate (ddTTP), 2',3'-didehydro-2',3'-dideoxythymidine triphosphate (ddeTTP), 3'-chlorothymidine triphosphate (CldTTP), and 3'-rhodanothymidine triphosphate (SCNdTTP) were tested for their ability to inhibit hepatitis B virus (HBV)-associated DNA polymerase activity in vitro. The ID50 values of the most potent inhibitors were 0.15 microM for FdTTP, 0.2 microM for ddeTTP, 0.45 microM for ddTTP, and 0.8 microM for F-5CldUTP. SCNdTTP, CldTTP, and F-5EtdUTP were less efficient (ID50 = 3-5 microM), and FdUTP and F-5FdUTP were the least efficient inhibitors (ID50 = 25 microM) of the enzyme activity. Kinetic analysis revealed a competitive type of inhibition for FdTTP and ddeTTP. The Ki values were estimated to be 0.04 microM and 0.08 microM, respectively, compared with a Km value for dTTP of about 0.18 microM.

Treatment of chronic hepatitis B with interferon alfa-2b

A total of 58 patients with histologically confirmed chronic viral hepatitis B and presence of hepatitis B surface antigen and hepatitis B virus DNA (HBV DNA) in the serum were randomized in a prospectively controlled trial. Thirty patients were treated with 3 megaunits of recombinant interferon alfa-2b (INTRON A, R Schering-Plough, Essex Corporation) subcutaneously thrice weekly for 4 months. Twenty-eight controls received no treatment. The post-treatment follow-up period consisted of 6 months. Twenty-eight treated patients and 27 controls completed the protocol. One female patient of the treatment group showed a complete response, and eight other treated patients (32%) showed a partial response to therapy. Three patients in the control group (11%) lost hepatitis B e antigen and HBV DNA spontaneously. This finding is statistically significant (p less than 0.05). The elimination of hepatitis B virus markers from the serum was associated with a normalization of aminotransferase activities in the serum. Reactivation of hepatitis was not observed after seroconversion.

Biologically active peptides in milk proteins

Bioactive peptides have been identified as digestion products of several food proteins. All the bioactive sequences are hidden in an inactive state inside the polypeptide chain of the larger protein. Milk proteins are a rich source of biologically active peptides such as exorphins (casomorphins), phosphopeptides and immunopeptides. Such peptides are released during intestinal digestion of caseins and whey proteins. They may be involved in regulation of nutrient entry and influence the postprandial metabolism via stimulation of the secretion of hormones. Furthermore, they may exert a stimulating effect on the immune system. These findings offer new aspects for evaluating the nutritive value of food proteins. Moreover, bioactive peptides have already found interesting applications as dietary supplements and as pharmaceutical preparations.

Chemical characterization of bioactive peptides from in vivo digests of casein

The in vivo formation of biologically active caseinopeptides was studied. It was proved that bioactive peptides were released in the small intestine of minipigs in the course of luminal digestion of diets containing bovine casein. An opioid peptide and a phosphopeptide were isolated from jejunal chyme and were chemically characterized. The opioid peptide has been identified as a fragment of beta-casein (60-70). This peptide, named beta-casomorphin-11, displayed substantial opioid activity in an opiate receptor-binding assay. The caseinophosphopeptide has been shown to be a fragment of alpha s1-casein (66-74). Casein-derived phosphopeptides exhibit a potent ability to form soluble complexes with Ca and trace elements. Evidence exists that casomorphins and caseinophosphopeptides participate in the regulation of nutrient entry.

Chemical characterization of a caseinophosphopeptide isolated from in vivo digests of a casein diet

The in vivo formation of phosphopeptides derived from bovine casein was proved in small intestinal chyme of minipigs after ingestion of a diet containing casein. The main phosphopeptide was identified as a fragment of alpha s1-casein (f 66-74): SerP-SerP-SerP-Glu-Glu-Ile-Val-Pro-Asn. It is discussed, that caseinophosphopeptides are likely to promote the intestinal absorption of calcium and trace elements.