Chimeric monoclonal antibodies to hypervariable region 1 of hepatitis C virus

Reduction of enterotoxin induced fluid accumulation in ileal loops of neonatal calves with anti-F5 fimbriae recombinant antibody

Neonatal calf colibacillosis caused by enterotoxigenic Escherichia coli (ETEC) is an economically significant problem in most parts of the world. The most common ETEC found in calves express the F5 (K99) fimbriae, which are necessary for the attachment of the bacteria to the ganglioside receptors on enterocytes. It is known that prevention of ETEC F5(+) adhesion to its ganglioside receptors with specific antibodies protects calves from colibacillosis. Previously we have described the development and characterization of a mouse recombinant antibody fragment (moRAb) that prevents F5 fimbrial protein induced agglutination of horse red blood cells (HRBC), which exhibit the same gangloside receptor for F5 fimbriae. Here we demonstrate that this recombinant antibody fragment inhibits in vitro the attachment of ETEC F5(+) bacteria to HRBC as well as isolated calf enterocytes, and in vivo it decreases fluid accumulation in intestinal loops of calves. Thus, correct oral administration of this anti-F5 moRAb may serve as an immunoprophylactic for cost effective control of colibacillosis in calves.

On the meaning of affinity limits in B-cell epitope prediction for antipeptide antibody-mediated immunity

B-cell epitope prediction aims to aid the design of peptide-based immunogens (e.g., vaccines) for eliciting antipeptide antibodies that protect against disease, but such antibodies fail to confer protection and even promote disease if they bind with low affinity. Hence, the Immune Epitope Database (IEDB) was searched to obtain published thermodynamic and kinetic data on binding interactions of antipeptide antibodies. The data suggest that the affinity of the antibodies for their immunizing peptides appears to be limited in a manner consistent with previously proposed kinetic constraints on affinity maturation in vivo and that cross-reaction of the antibodies with proteins tends to occur with lower affinity than the corresponding reaction of the antibodies with their immunizing peptides. These observations better inform B-cell epitope prediction to avoid overestimating the affinity for both active and passive immunization; whereas active immunization is subject to limitations of affinity maturation in vivo and of the capacity to accumulate endogenous antibodies, passive immunization may transcend such limitations, possibly with the aid of artificial affinity-selection processes and of protein engineering. Additionally, protein disorder warrants further investigation as a possible supplementary criterion for B-cell epitope prediction, where such disorder obviates thermodynamically unfavorable protein structural adjustments in cross-reactions between antipeptide antibodies and proteins.

Impact of host responses on control of hepatitis C virus infection in Chinese blood donors

A study was undertaken to explore the molecular mechanisms underlying control of HCV infection in blood donors in China. Factors including clinical information, anti-HCV reactivity (S/CO), IFN-α and IFN-γ, viral loads and genotypes were correlated with 160 index plasma samples at three statuses of 45 recovered, 76 chronic or 39 false positive anti-HCV reactive blood donors. The spontaneous recovery rate was 37.2%. Viral loads of 76 HCV plasmas ranged between 59.8 IU/ml and 2.43 × 10(6)IU/ml (median 3.67 × 10(4)IU/ml). Genotypes 1, 2, 3 and 6 of 63 HCV strains were identified phylogenetically. Recovered donors were significantly younger (p=0.002) and had lower level IFN-γ (p=0.001) than chronically HCV infected donors. Circulating levels of IFN-α and IFN-γ were higher in those with low viral load and were low in middle or high viral load samples. The ratio of IFN-α to IFN-γ (IFN-α/γ) was significantly positively correlated with viral load (p=0.037), and viral load was inversely correlated with IFN-γ in chronic HCV infection regardless of genotype. The study revealed clearly different relationships between IFN-α and IFN-γ in relation to viral load in HCV. A novel measure of IFN-α/γ ratio could be a new approach to evaluate long term outcome of HCV infection.

Characterization of antibody-mediated neutralization directed against the hypervariable region 1 of hepatitis C virus E2 glycoprotein

The hypervariable region 1 (HVR1) comprising the first 27 aa of E2 glycoprotein is a target for neutralizing antibodies against hepatitis C virus (HCV), but the mechanisms of this neutralization in the cell-culture-infectious genotype 2a strain JFH1 HCV virus (HCVcc) system are unknown. Two rabbit polyclonal sera, R1020 and R140, recognizing the HVR1 of the genotype 1a isolates H77c and Glasgow (Gla), respectively, and a Gla HVR1-specific mouse mAb AP213 have been described previously. However, attempts to generate of antibodies to the JFH1 HVR1 were unsuccessful. Therefore, this study produced chimeric JFH1 HCVcc viruses harbouring the H77c or Gla HVR1 to assess the reactivity of antibodies to this region and their effects on virus infectivity. The inter-genotypic HVR1 swap did not significantly affect virus infectivity. The genotype 1a HVR1-specific antibodies neutralized chimeric viruses in an isolate-dependent manner, underlining the role of HVR1 in HCV infection. The neutralizing antibodies reacted mainly with the C-terminal portion of HVR1, and detailed mapping identified A17, F20 and Q21 in the Gla HVR1 sequence and T21 (and possibly L20) in the corresponding H77c sequence as key epitope residues for AP213 and R140, and R1020, respectively. Importantly, none of the antibodies inhibited in vitro binding of viral envelope glycoproteins to the best-characterized HCV receptor, CD81, or to the glycosaminoglycan attachment factors. However, the HVR1 antibodies were capable of post-attachment neutralization. Overall, this study emphasizes the role of HVR1 in HCVcc entry and provides new tools to study this region further in the context of complete virions.

Chimeric antibodies against tick-borne encephalitis virus

Two chimeric antibodies (ch) 13D6 and 10C2 against the glycoprotein E of tick-borne encephalitis virus (TBEV) were constructed by fusing variable regions of murine monoclonal antibodies (Mabs) 13D6 and 10C2 to human constant regions. Monovalent analogues of these antibodies in format of single-chain antibodies (scFv or sc) were developed, as well. The ch13D6, ch10C2, sc13D6 and sc10C2 exhibited binding characteristics similar to parental Mabs. Only the ch13D6 and sc13D6 were able to neutralize TBEV infectivity in vitro. The in vitro neutralization provided by ch13D6 suggests that this antibody can be further developed into a potent prophylaxis and therapy for tick-borne encephalitis (TBE) infection.

MONOCLONAL ANTIBODIES AS TARGETING AND THERAPEUTIC AGENTS: PROSPECTS FOR LIVER TRANSPLANTATION, HEPATITIS AND HEPATOCELLULAR CARCINOMA

1. Monoclonal antibodies (mAbs) of high specificity and stability have become key resources in the therapeutic, diagnostic and drug discovery fields to treat various immunological disorders and malignancies of different organs. 2. The latest genetic engineering technology applied in antibody design and production, such as phage display technology and genetically modified mouse, have revolutionized the clinical applicability and feasibility of the use of mAbs in humans. 3. Innovative antibody products in the forms of single-chain or super-humanized antibody therapeutics having a higher affinity for target antigens and minimal antigenicity in hosts have been introduced for experimental purposes and/or clinical trials. 4. Although there are successful examples of antibody therapeutics in the market, the use of mAbs in treating hepatitis-related disease and hepatocellular carcinoma is rare and remains to be exploited.

Survey of the year 2005 commercial optical biosensor literature

We identified 1113 articles (103 reviews, 1010 primary research articles) published in 2005 that describe experiments performed using commercially available optical biosensors. While this number of publications is impressive, we find that the quality of the biosensor work in these articles is often pretty poor. It is a little disappointing that there appears to be only a small set of researchers who know how to properly perform, analyze, and present biosensor data. To help focus the field, we spotlight work published by 10 research groups that exemplify the quality of data one should expect to see from a biosensor experiment. Also, in an effort to raise awareness of the common problems in the biosensor field, we provide side-by-side examples of good and bad data sets from the 2005 literature.