Monoclonal antibodies: implications for virology. Brief review

How neutron scattering techniques benefit investigating structures and dynamics of monoclonal antibody

Over the past several decades, great progresses have been made for the pharmaceutical industry of monoclonal antibody (mAb). More and more mAb products were approved for human therapeutics. This review describes the state of art of utilizing neutron scattering to investigate mAbs, in the aspects of structures, dynamics, physicochemical stability, functionality, etc. Firstly, brief histories of mAbs and neutron scattering, as well as some basic knowledges and principles of neutron scattering were introduced. Then specific examples were demonstrated. For the structure and structural evolution investigation of in dilute and concentrated mAbs solution, in situ small angle neutron scattering (SANS) was frequently utilized. Neutron reflectometry (NR) is powerful to probe the absorption behaviors of mAbs on various surfaces and interfaces. While for dynamic investigation, quasi-elastic scattering techniques such as neutron spin echo (NSE) demonstrate the capabilities. With this review, how to utilize and take advantages of neutron scattering on investigating structures and dynamics of mAbs were demonstrated and discussed.

Pathogenicity and immunogenicity of influenza viruses with genes from the 1918 pandemic virus

The 1918 influenza A H1N1 virus caused the worst pandemic of influenza ever recorded. To better understand the pathogenesis and immunity to the 1918 pandemic virus, we generated recombinant influenza viruses possessing two to five genes of the 1918 influenza virus. Recombinant influenza viruses possessing the hemagglutinin (HA), neuraminidase (NA), matrix (M), nonstructural (NS), and nucleoprotein (NP) genes or any recombinant virus possessing both the HA and NA genes of the 1918 influenza virus were highly lethal for mice. Antigenic analysis by hemagglutination inhibition (HI) tests with ferret and chicken H1N1 antisera demonstrated that the 1918 recombinant viruses antigenically most resembled A/Swine/Iowa/30 (Sw/Iowa/30) virus but differed from H1N1 viruses isolated since 1930. HI and virus neutralizing (VN) antibodies to 1918 recombinant and Sw/Iowa/30 viruses in human sera were present among individuals born before or shortly after the 1918 pandemic. Mice that received an intramuscular immunization of the homologous or Sw/Iowa/30-inactivated vaccine developed HI and VN antibodies to the 1918 recombinant virus and were completely protected against lethal challenge. Mice that received A/PR/8/34, A/Texas/36/91, or A/New Caledonia/20/99 H1N1 vaccines displayed partial protection from lethal challenge. In contrast, control-vaccinated mice were not protected against lethal challenge and displayed high virus titers in respiratory tissues. Partial vaccine protection mediated by baculovirus-expressed recombinant HA vaccines suggest common cross-reactive epitopes on the H1 HA. These data suggest a strategy of vaccination that would be effective against a reemergent 1918 or 1918-like virus.

A pulmonary influenza virus infection in SCID mice can be cured by treatment with hemagglutinin-specific antibodies that display very low virus-neutralizing activity in vitro

We have previously shown that a pulmonary influenza virus infection in SCID mice can be cured by treatment with monoclonal antibodies (MAbs) specific for the viral transmembrane protein hemagglutinin (HA) but not for matrix 2. Since both types of MAbs react with infected cells but only the former neutralizes the virus, it appeared that passive MAbs cured by neutralization of progeny virus rather than reaction with infected host cells. To prove this, we selected a set of four HA-specific MAbs, all of the immunoglobulin G2a isotype, which reacted well with native HA expressed on infected cells yet differed greatly (>10,000-fold) in virus neutralization (VN) activity in vitro, apparently because of differences in antibody avidity and accessibility of the respective determinants on the HA of mature virions. Since the VN activities of these MAbs in vitro were differentially enhanced by serum components, we determined their prophylactic activities in vivo and used them as measures of their actual VN activities in vivo. The comparison of therapeutic and prophylactic activities indicated that these MAbs cured the infection to a greater extent by VN activity (which was greatly enhanced in vivo) and to a lesser extent by reaction with infected host cells. Neither complement- nor NK cell-dependent mechanisms were involved in the MAb-mediated virus clearance.

Validation of a quantitative ELISA for comparison of monoclonal antibody affinities for isolates of bluetongue virus

The ability of an ELISA-based system to reliably assess the relative affinities of separate monoclonal antibodies (MAbs) for heterologous isolates of bluetongue virus (BTV) was tested. The demonstration that a BTV serogroup-specific MAb (20E9B7G2) possessed equivalent binding properties with the majority of virus isolates tested, permitted a reliable estimation of the relative amount of individual test viruses present in the assay. Subsequent correction for the relative amounts of test viruses and homologous virus present, then allowed monoclonal antibody affinities for heterologous virus isolates to be quantitatively expressed as a function of their homologous binding level and enabled comparisons of individual MAb affinities between virus isolates to be made.

A second envelope glycoprotein mediates neutralization of a pestivirus, hog cholera virus

Several monoclonal antibodies (MAbs) raised against hog cholera virus (HCV) reacted with the HCV structural glycoprotein gp44/48 and neutralized the virus. The presence of HCV gp44/48 on the viral surface was directly demonstrated by immunogold electron microscopy. Eight anti-HCV gp44/48 MAbs were tested by immunoperoxidase assay against a panel of pestivirus strains. Each MAb showed a distinct pattern of reactivity with HCV strains. It is suggested that the MAbs are well suited for epidemiological investigations of HCV outbreaks.

The synergistic neutralization of Rift Valley fever virus by monoclonal antibodies to the envelope glycoproteins

A panel of monoclonal antibodies (MAbs) mapping to different antigenic sites on the RVFV G1 and G2 proteins were used to examine the mechanisms involved in neutralization of the virus. Three types of synergistic neutralization of RVFV were observed on mixing various pairs of MAbs. Firstly, enhanced neutralization occurred for two MAb pairs that showed augmented binding for G2. These comprised a combination of a neutralizing MAb with a non-neutralizing antibody, as well as two antibodies which were non-neutralizing individually. In the second category, synergistic neutralization was observed between combinations of MAbs for which increased binding had not been detected. Lastly, mixtures of G1 and G2-specific MAbs were also capable of enhancing neutralization. Post-adsorption neutralization assays revealed that some MAbs neutralized cell-attached virus efficiently, indicating that they can neutralize by inhibiting the infection process after virus attachment. MAbs mapping to G1 IIe, G2I b and G2I c were unable to neutralize adsorbed virus and thus probably neutralize by preventing virus attachment to cells. Several G1-reactive MAbs displayed low level post-adsorption activity, suggesting they may be capable of inhibiting RVFV infectivity at different stages of the replication cycle.

Effects of specific monoclonal antibodies on La Crosse virus neutralization: aggregation, inactivation by Fab fragments, and inhibition of attachment to baby hamster kidney cells

At high concentrations, several monoclonal antibodies to the G1 glycoprotein of La Crosse (LAC) virus aggregated the virus. To determine whether this accounted for the neutralization, the monoclonal antibodies were digested to make Fab fragments. With one exception, each monovalent antibody neutralized LAC virus to the same extent that bivalent antibody did, although higher concentrations were needed. Fab fragments of synergistic pairs of antibodies also exhibited enhanced binding in a competition binding assay but did not increase neutralization. To determine specific mechanisms for neutralization, the effects of polyclonal or monoclonal antibodies on virus attachment were examined. Polyclonal antibody to LAC virus reduced virus attachment by only 68% although it neutralized 99.99% of the virus. When virus was preincubated with a neutralizing monoclonal antibody to each of seven antigenic regions on G1, only antibody to one region reduced attachment of virus by as much as 92%. Antibodies to two regions that neutralize virus by 90-98% only inhibited attachment by 9 and 13%, respectively. The other antibodies showed intermediate degrees of neutralization and inhibition of attachment. Pairs of antibodies previously shown to be synergistic in neutralizing activity did not inhibit attachment any more than the single antibodies did.

Hydrophobized antiviral antibodies and antisense oligonucleotides

A method of suppressing virus reproduction in cells has been proposed. The approach consists of affecting the cells with antiviral antibodies artificially hydrophobized with fatty acid residues. Reproduction of influenza viruses in MDCK cells and respiratory-synticial virus in HeLa cells was used as a model to demonstrate that poly- and monoclonal antibodies, modified by 1 or 2 stearic acid residues, are potent, unlike the non-modified antibodies, at inhibiting viral reproduction. The observed phenomenon is apparently due to penetration of hydrophobized antibodies into the cells. Thus, in particular, considerable antiviral activity is exhibited by monoclonal antibodies against NP-protein of influenza virus, which is an antigen accessible to antibodies only inside the infected cells. Hydrophobized antibodies do not affect the kinetics of viral protein synthesis; they block the virus withdrawal from the cells, probably by interfering with the assembling and budding of virus particles. To enhance penetration of oligonucleotides ("oligos") into cells, chemical modification of the former at the 5'-end phosphate group by fatty radicals has been suggested. The undecanol-modified oligo namely an oligo complementary to the protein binding sites located at the influenza virus polymerases encoding RNA, was synthesized using a DNA-synthesator. The above modified oligo effectively suppressed the influenza A/PR8/34 virus reproduction and inhibited synthesis of the virus-specific proteins in MDCK cells. The non-modified antisense oligo and the modified nonsense oligo did not affect the virus development under the same conditions.

Structure of viral B-cell epitopes

Four categories of viral epitopes can be distinguished that have been designated cryptotopes, neotopes, metatopes and neutralization epitopes. Specific examples of each epitope type are presented and the methods used for locating their positions in viral proteins are described. The epitopes of four well-characterized viruses, namely poliovirus, foot-and-mouth disease virus, influenza virus and tobacco mosaic virus are briefly described.

Fatty acid acylated antibodies against virus suppress its reproduction in cells

A method for suppression of virus reproduction in cells using fatty acylated antiviral antibodies, which in contrast to non-modified antibodies are capable of intracellular penetration, has been suggested. The addition of stearoylated antiviral antibodies to influenza A/Chili virus-infected cells causes a 100-fold suppression of virus reproduction. Non-modified antibodies do not produce any effect on virus reproduction.

New approaches to animal vaccines utilizing genetic engineering

Control of infectious diseases in livestock is an important determinant in the success of a nation's effort to efficiently meet its need for animal products. Genetic engineering offers many new options in the design of animal vaccines. Monoclonal antibodies, DNA cloning, recombination, and transfection are examples of techniques that facilitate innovative strategies in antigen identification, production, and delivery. This article reviews the use of genetic engineering in the production of vaccines directed against foot-and-mouth disease virus and other important pathogens of animals. The advantages and disadvantages of vaccines produced through the use of genetic engineering are discussed.

Monoclonal antibodies and immobilized antibodies. Patents and literature

Antibodies in both their free and immobilized state have been the object of considerable industrial and academic interest. A variety of methods are used for preparing and immobilizing antibodies. Applications for monoclonal antibodies include the preparation of therapeutics, diagnostics, and in affinity fractionation. Recent US patents on monoclonal and immobilized antibodies and scientific literature on monoclonal antibodies are surveyed. A description of these patents and a list of references are given.

Epitopes on foot-and-mouth disease virus particles. I. Topology

Monoclonal antibodies (MAb) against an O1 Suisse isolate of FMDV were used to identify epitopes on the virus particle and to determine their relative function. Six major antigenic sites containing one or more epitopes were identified using competition ELISA. An epitope relationship is proposed consisting of a trypsin-sensitive sequential site, termed B2/D9, from the codings for the MAb which reacted with it, which was associated with virus infectivity and is probably at or near to the cell-binding site of the virion; a trypsin-resistant, conformational site 1C6/4C9 MAb reaction at which also resulted in neutralization of virus infectivity; a second trypsin-resistant, conformational site 3C8, where again MAb reaction neutralised virus infectivity; a third trypsin-resistant, conformational site 6C3/2G5, at which MAb-dependent neutralisation of virus infectivity was inefficient; a site 3G4, the expression of which was impaired but not destroyed by trypsin treatment, and was not related to virus infectivity; an internal site A8, which appears to be a "12S subunit-specific" site. This work clearly demonstrates for the first time that both trypsin-sensitive and trypsin-resistant neutralisable (infectivity-associated) sites exist on the FMDV particle, and only one of these can be related to the sequential site used to formulate current FMDV peptide vaccines.

Relationship between poliovirus neutralization and aggregation

The interaction of mono- and polyclonal neutralizing antibodies with poliovirus was studied. In all cases, neutralization was due to antibody-mediated virus aggregation, and the unpolymerized virions accounted for the residual infectivity. The effect of papain on previously neutralized virus was to deaggregate the virus to fully infective single virions. With some antibodies, the amount of aggregated virus regressed in the region of greatest antibody excess, even though the virus remained fully neutralized. Under these conditions, noninfective, unaggregated immune complexes were formed. A mutant resistant to one of the monoclonal antibodies was selected. The mutant virions were still bound but no longer aggregated or neutralized by the selecting antibodies.