Construction and characterization of hexon-chimeric adenoviruses: specification of adenovirus serotype

This study has used the strategy of gene replacement to characterize the contribution of the adenovirus (Ad) capsid protein hexon to serotype definition. By replacing the Ad type 5 (Ad5) hexon gene with sequences from Ad2, we have changed the type specificity of the chimeric virus. The type-determining epitopes are primarily associated with loop 1 of hexon and, to a much lesser degree, with loop 2. In spite of the serotype distinctiveness of the chimeric hexon viruses, epitope similarity between the vectors resulted in a low level of cross-reactive neutralizing antibody, which in combination with activated cellular and innate arms of the immune system is sufficient to suppress gene transduction following readministration in vivo.     

Hexon sequence of adenovirus type 7 and comparison with other serotypes of subgenus B

The hexon gene of human adenovirus (AV) type 7 (subgenus B) was sequenced. The determined nucleotide and the predicted amino acid sequences were compared to the corresponding sequences of AV3 and AV16. The hexons of AV7 and AV3 revealed an overall homology of 94.3% at the protein level, whereas the AV7 and AV16 hexons only showed an overall homology of 85.7%. Utilizing the three-dimensional model of the AV2 hexon, the structure of the AV7 hexon was predicted. The major differences between the three subgenus B hexon polypeptides were confined to the I1 and I2 surface loops. The AV7 I4 hexon loop was 100% identical to the other subgenus B I4 loops, but differed from the corresponding regions of other subgenera. This supports the idea that this loop carries a subgenus-specific determinant.     

Human immunodeficiency virus type 1 attachment to HeLa CD4 cells is CD4 independent and gp120 dependent and requires cell surface heparans

The binding of human immunodeficiency virus type 1 (HIV-1) (Hx10) virions to two different cell lines was analyzed by using a novel assay based on the detection, by anti-HLA-DR-specific antibodies, of HLA-DR+ virus binding to HLA-DR- cells. Virion attachment to the CD4+-T-cell line A3.01 was highly CD4 dependent in that it was potently inhibited by CD4 monoclonal antibodies (MAbs), and little virus binding to the CD4- sister A2.01 line was observed. By contrast, virion binding to HeLa cells expressing moderate or high levels of CD4 was equivalent to, or lower than, binding to wild-type CD4- HeLa cells. Moreover, several CD4 MAbs did not reduce, but enhanced, HIV-1 attachment to HeLa-CD4 cells. CD4 was required for infection of HeLa cells, however, demonstrating a postattachment role for this receptor. MAbs specific for the V2 and V3 loops and the CD4i epitope of gp120 strongly inhibited virion binding to HeLa-CD4 cells, whereas MAbs specific for the CD4bs and the 2G12 epitopes enhanced attachment. Despite this, all gp120- and gp41-specific MAbs tested neutralized infectivity on HeLa-CD4 cells. HIV-1 attachment to HeLa cells was only partially inhibited by MAbs specific for adhesion molecules present on the virus or target cells but was completely blocked by polyanions such as heparin, dextran sulfate, and pentosan sulfate. Treatment of HeLa-CD4 cells with heparinases completely eliminated HIV attachment and infection, strongly implicating cell surface heparans in the attachment process. CD4 dependence for HIV-1 attachment to target cells is thus highly cell line specific and may be replaced by other ligand-receptor interactions.     

Characterization of a temperature-sensitive, hexon transport mutant of type 5 adenovirus

Infection of KB cells at 39.5 degrees C with H5ts147, a temperature-sensitive (ts) mutant of type 5 adenovirus, resulted in the cytoplasmic accumulation of hexon antigen; all other virion proteins measured, however, were normally transported into the nucleus. Immunofluorescence techniques were used to study the intracellular location of viral proteins. Genetic studies revealed that H5ts147 was the single member of a nonoverlapping complementation group and occupied a unique locus on the adenovirus genetic map, distinct from mutants that failed to produce immunologically reactive hexons at 39.5 degrees C ("hexon-minus" mutants). Sedimentation studies of extracts of H5ts147-infected cells cultured and labeled at 39.5 degrees C revealed the production of 12S hexon capsomers (the native, trimeric structures), which were immunoprecipitable to the same extent as hexons synthesized in wild type (WT)-infected cells. In contrast, only 3.4S polypeptide chains were found in extracts of cells infected with the class of mutants unable to produce immunologically reactive hexon protein at 39.5 degrees C. Hexons synthesized in H5ts147-infected cells at 39.5 degrees C were capable of being assembled into virions, to the same extent as hexons synthesized in WT-infected cells, when the temperature was shifted down to the permissive temperature, 32 degrees C. Infectious virus production was initiated within 2 to 6 h after shift-down to 32 degrees C; de novo protein synthesis was required to allow this increase in viral titer. If ts147-infected cells were shifted up to 39.5 degrees C late in the viral multiplication cycle, viral production was arrested within 1 to 2 h. The kinetics of shutoff was similar to that of a WT-infected culture treated with cycloheximide at the time of shift-up. The P-VI nonvirion polypeptide, the precursor to virion protein VI, was unstable at 39.5 degrees C, whereas the hexon polypeptide was not degraded during the chase. It appears that there is a structural requirement for the transport of hexons into the nucleus more stringent than the acquisition of immunological reactivity and folding into the 12S form.     

Epitope mapping of anti-troponin I monoclonal antibodies

Two groups of monoclonal antibodies (MAbs) specific to human cardiac troponin I (cTnI) were generated by immunization of mice by isolated cTnI (group I, 16 MAbs) or by the whole troponin complex (group II, 15 MAbs). Two sets of overlapping decapeptides covering the complete sequence of cTnI were prepared and used for epitope mapping by SPOT technique. Majority of MAbs (28 out of 31) interacts with synthetic peptides thus indicating that they recognize liner epitopes. MAbs raised against isolated cTnI preferentially recognize epitopes located at the N- or C-terminal ends of cTnI. Nine out of fifteen MAbs raised against whole troponin complex interact with epitopes located in the N-terminal part of cTnI. Generation of MAbs recognizing both isolated cTnI and cTnI inside of troponin complex and mapping their epitopes provides reliable detection of TnI in serum of patients with acute myocardial infarction.     

Epizootic hemorrhagic disease virus and bluetongue virus serotype distribution in white-tailed deer in Georgia

Assessment of the current incidence of different adenovirus types in local gastroenteritis involved the examination of over 1,000 stool specimens annually from 1988-1992. Adenoviruses were detected by electron microscopy and/or cell culture in 32% of the specimens in which a viral pathogen was detected. The identification of every adenovirus isolate to type by neutralization with specific antisera against the first 6 types and by restriction analysis of nonneutralized isolates was started in 1990. Samples from 1988 and 1989 were examined retrospectively. Adenovirus strains were compared to those isolated in a study between 1980-1983. Enumeration of individual adenovirus types revealed a number of trends, demonstrating that rapid changes in the local incidence of several strains were occurring in Manitoba. The incidence of adenovirus type 40 (Ad40) as a cause of gastroenteritis was found to have fallen dramatically in recent years. The predominant cause of gastroenteritis in Manitoba is a variant strain of Ad41, increasing in predominance each year and now responsible for over a third of the symptomatic cases examined since 1990. The majority of restriction site differences of the Ad41 variant strain from the prototype strain Tak were mapped to the hexon and fiber genes, both of which code for the neutralizable external viral epitopes. The probability of the observed pattern of mutations occurring by chance was calculated as P < 0.0005, indicating a strong pressure for selection of these immunologically significant alterations to the viral proteins responsible for cell attachment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glycoproteins E2 of the Venezuelan and eastern equine encephalomyelitis viruses contain multiple cross-reactive epitopes

Enzyme immunoassay (EIA) with sixty types of monoclonal antibodies (MAbs) was used to study cross-reactive epitopes on the attenuated and virulent strains of the Eastern equine encephalomyelitis (EEE) and Venezuelan equine encephalomyelitis (VEE) viruses. All three structural proteins of the EEE and VEE viruses were demonstrated to have both cross-reactive and specific antigenic determinants. The glycoprotein E1 of EEE and VEE viruses possesses three cross-reactive epitopes for binding to MAbs. The glycoprotein E2 has a cluster of epitopes for 20 cross-reacting MAbs produced to EEE and VEE viruses. Cross-reactive epitopes were localised within five different sites of glycoprotein E2 of VEE virus and within four sites of that of the EEE virus. There are no cross-neutralising MAbs to the VEE and EEE viruses. Only one type of the protective Mabs was able to cross-protect mice against lethal infection by the virulent strains of the VEE and EEE viruses. Eight MAbs blocked the hemagglutination activity (HA) of both viruses. Antigenic alterations of neutralising and protective sites were revealed for all attenuated strains of the VEE and EEE viruses. Comparative studies of the E2 proteins amino acid sequences show that the antigenic modifications observed with the attenuated strains of the VEE virus may be caused by multiple amino acid changes in positions 7, 62, 120, 192 and 209-213. The escape-variants of the VEE virus obtained with cross-reactive MAbs 7D1, 2D4 and 7A6 have mutations of the E2 protein at positions 59, 212-213 and 232, respectively. Amino acid sequences in these regions of the VEE and EEE viruses are not homologous. These observations indicate that cross-reactive MAbs are capable of recognising discontinuous epitopes on the E2 glycoprotein.     

Analysis of autoantibody epitopes on steroid 21-hydroxylase using a panel of monoclonal antibodies

A panel of five mouse monoclonal antibodies (MAbs) to human recombinant steroid 21-hydroxylase (21-OH) were produced, characterized, and used to study the interaction of 21-OH autoantibodies (AAbs) with different epitopes on human 21-OH. AAbs in patients with isolated autoimmune Addison's disease, autoimmune polyglandular syndromes types I and II, and 21-OH antibody-positive patients without overt Addison's disease (25 patients in total) were studied. Four MAbs were IgG1 subclass, one was IgG2a, and all had kappa light chains. The affinities of four of the antibodies were in the range 2.0 x 10(8) M(-1) to 7.0 x 10(8) M(-1), and the affinity of the other was 2.3 x 10(7) M(-1) 21-OH MAbs did not cross-react with 17alpha-hydroxylase (17alpha-OH)) or P450 side chain cleavage enzyme. Studies using a series of 21-OH fragments allowed the identification of short stretches of amino acids (AA) that were involved in forming the MAb binding sites. AA 391-405, defined as epitope region (ER) 1, were found to be important for binding of M21-OH1 and M21-OH2, AA 406-411 (ER2) were important for M21-OH3 and M21-OH4 binding, and AA 335-339 (ER3) for M21-OH5 binding. In addition, MAb Fab or F(ab')2 fragments were used to study 21-OH AAb epitopes in competition experiments. These investigations demonstrated that 21-OH AAbs recognize similar epitopes to the MAbs, with ER2 and ER3 being part of two distinct major epitopes, and ER 1 being part of a minor epitope. Mixtures of M21-OH antibody Fab or F(ab')2 fragments caused almost complete inhibition (80%-95%) of AAb binding in 24 out of 25 sera, and in the case of the remaining serum, the effect was marked but incomplete (67% inhibition). There were no major differences between the binding characteristics of AAbs from patients with different forms of autoimmune adrenal disease. All five 21-OH MAbs reacted with human adrenal tissue in an immunofluorescence test, but only M21-OH1 and M21-OH2 reacted with bovine adrenal tissue in these experiments. None of the MAbs reacted with human ovarian tissue in an immunofluorescence test. Overall, these studies indicate that 21-OH AAbs bind to at least three different epitopes in the C-terminal part of 21-OH, and two of these epitopes appear to be human 21-OH specific.     

Cytotoxic T-lymphocyte target proteins and their major histocompatibility complex class I restriction in response to adenovirus vectors delivered to mouse liver

The activation of cytotoxic T lymphocytes (CTLs) to cells infected with adenovirus vectors contributes to problems of inflammation and transient gene expression that attend their use in gene therapy. The goal of this study was to identify in a murine model of liver gene therapy the proteins that provide targets to CTLs and to characterize the major histocompatibility complex (MHC) class I restricting elements. Mice of different MHC haplotypes were infected with an E1-deleted adenovirus expressing human alkaline phosphatase (ALP) or beta-galactosidase as a reporter protein, and splenocytes were harvested for in vitro CTL assays to aid in the characterization of CTL epitopes. A library of vaccinia viruses was created to express individual viral open reading frames, as well as the ALP and lacZ transgenes. The MHC haplotype had a dramatic impact on the distribution of CTL targets: in C57BL/6 mice, the hexon protein presented by both H-2Kb and H2Db was dominant, and in C3H mice, H-2Dk-restricted presentation of ALP was dominant. Adoptive transfer of CTLs specific for various adenovirus proteins or transgene products into either Rag-I or C3H-scid mice infected previously with an E1-deleted adenovirus verified the in vivo relevance of the adenovirus-specific CTL targets identified in vitro. The results of these experiments illustrate the impact of lr gene control on the response to gene therapy with adenovirus vectors and suggest that the efficacy of therapy with adenovirus vectors may exhibit considerable heterogeneity when applied in human populations.     

Fibronectin of human liver sinusoids binds hepatitis B virus: identification by an anti-idiotypic antibody bearing the internal image of the pre-S2 domain

Anti-idiotypic antibodies (anti-Ids) have been successfully used to characterize and isolate receptors of several cell ligands. To prepare an immunological probe for identification of cellular components interacting with the hepatitis B virus (HBV), polyclonal antisera against a panel of five HBV-specific monoclonal antibodies (MAbs) were produced in syngeneic BALB/c mice. MAbs to HBV used for immunization (Ab1) recognized biologically important and potentially neutralizing epitopes, located in the pre-S1, pre-S2, or S region-encoded domains of HBV proteins. All the anti-Ids (Ab2) were specific to idiotopes of the homologous Ab1 and inhibited their interaction with the corresponding viral epitopes, suggesting that they recognized unique determinants on the paratope of each immunizing Ab1. Therefore, all five generated polyclonal anti-Ids were of the Ab2 beta type and could represent internal images of viral epitopes. Ab2 raised against the pre-S2 region-specific MAb F124 bound to the extracellular matrix fibronectin of human liver sinusoids. Immunohistochemical studies demonstrated the attachment of viral and recombinant (S, M) hepatitis B surface antigen particles with the pre-S2 region-encoded epitopes to the fibronectin of human liver sinusoids. In contrast, recombinant (S, L*) hepatitis B surface antigen particles, in which the epitope recognized by F124 MAb was not expressed, did not show any binding capacity. These findings suggest that human liver fibronectin may bind HBV in vivo by the pre-S2 region-encoded epitopes in a species-restricted manner. Furthermore, binding of the circulating virus to liver sinusoids could facilitate its subsequent uptake by hepatocytes.     

Surface conformational and linear epitopes on HPV-16 and HPV-18 L1 virus-like particles as defined by monoclonal antibodies

A panel of 24 monoclonal antibodies (MAbs) was generated against human papillomavirus (HPV) types 16 and 18 L1 virus-like particles (VLPs). The MAbs were screened for reactivity to a variety of VLPs prepared from HPV-6, -11, -16, -18, -31, -33, -35, and -45, cottontail rabbit papillomavirus, bovine papillomavirus type 1, and a set of 35 overlapping 20-amino-acid peptides spanning the entire HPV-16 L1 gene. Type-specific linear and conformational surface epitopes were detected as well as several cross-reactive linear epitopes that showed various levels of cross-reactivity between different genital HPV and animal papillomavirus L1s. Most of the linear epitopes were mapped using synthetic peptides, and the epitopes were identified as being either surface or buried within the VLP as defined by the pattern of reactivity in ELISA using intact and disrupted VLP antigen. These MAbs may be useful reagents to help define neutralizing epitopes of HPV-16 and -18 when infectivity assays become available, and to define the regions of L1 that are exposed on the surface or buried within the assembled capsid.     

Sequence analysis of equine adenovirus 2 hexon and 23K proteinase genes indicates a phylogenetic origin distinct from equine adenovirus 1

We report the first nucleotide sequence data on equine adenovirus 2 (EAdV2) which corroborate on the molecular level that EAdV2 is distinct from equine adenovirus 1 (EAdV1). Based on sequence homology with Eadv1 the hexon gene of Eadv2 was identified. HindIII restriction fragments containing the hexon and eight other viral genes were cloned into the plasmid pUC19 and the nucleotide sequence of the hexon and the 23K proteinase genes completely determined. Amino acid (aa) comparison of sequence fragments with published adenovirus (AdV) proteins identified the genes for the E1B/19K, IVa2, DNA polymerase, terminal protein, pVI, DNA binding and 100K proteins, usually with highest similarities to human AdV. The nine EAdV2 genes appeared to be in the same relative order as homologous genes of other AdV. The EAdV2 hexon was encoded between the minor capsid precursor protein pVI upstream and the 23K proteinase gene downstream and comprised 2712 nucleotides which translated into 903 aa residues. It was more closely related to the human AdV48 hexon with 71.6% identical and 82.7% functionally similar aa than to the EAdV1 hexon gene with 69.3% aa identity and 80.7% functional similarity. The deduced aa sequence of the EAdV2 23K proteinase gene was 201 residues; it shared 59.7% identical and 75% similar aa residues with the bovine AdV3 23K proteinase as the closest relative. Phylogenetic analysis of the hexon and 23K proteinase genes indicated that EAdV2 does not share an immediate common ancestor with EAdV1 and other AdV.     

Generation of neutralizing human monoclonal antibodies against parvovirus B19 proteins

Infections caused by human parvovirus B19 are known to be controlled mainly by neutralizing antibodies. To analyze the immune reaction against parvovirus B19 proteins, four cell lines secreting human immunoglobulin G monoclonal antibodies (MAbs) were generated from two healthy donors and one human immunodeficiency virus type 1-seropositive individual with high serum titers against parvovirus. One MAb is specific for nonstructural protein NS1 (MAb 1424), two MAbs are specific for the unique region of minor capsid protein VP1 (MAbs 1418-1 and 1418-16), and one MAb is directed to major capsid protein VP2 (MAb 860-55D). Two MAbs, 1418-1 and 1418-16, which were generated from the same individual have identity in the cDNA sequences encoding the variable domains, with the exception of four base pairs resulting in only one amino acid change in the light chain. The NS1- and VP1-specific MAbs interact with linear epitopes, whereas the recognized epitope in VP2 is conformational. The MAbs specific for the structural proteins display strong virus-neutralizing activity. The VP1- and VP2-specific MAbs have the capacity to neutralize 50% of infectious parvovirus B19 in vitro at 0.08 and 0.73 microgram/ml, respectively, demonstrating the importance of such antibodies in the clearance of B19 viremia. The NS1-specific MAb mediated weak neutralizing activity and required 47.7 micrograms/ml for 50% neutralization. The human MAbs with potent neutralizing activity could be used for immunotherapy of chronically B19 virus-infected individuals and acutely infected pregnant women. Furthermore, the knowledge gained regarding epitopes which induce strongly neutralizing antibodies may be important for vaccine development.     

Analysis of the bovine respiratory syncytial virus fusion protein (F) using monoclonal antibodies

Seven monoclonal antibodies (MAbs) directed against bovine respiratory syncytial virus (BRSV) fusion (F) protein were produced and characterized by radioimmunoprecipitation and immunofluorescence assays. These seven MAbs together with the previously described MAbs (Beeler and Van Wyke Coelingh, 1989) to the F protein of human respiratory syncytial virus (HRSV) were used to study the antigenic variation of 12 strains of ungulate RSV. All except one MAbs specific for the HRSV-F protein reacted with ungulate RSV strains less efficiently, indicating that some epitopes are conserved, and others are not conserved on the F proteins of HRSV and BRSV strains. Three MAbs specific to the BRSV-F protein neutralized virus infectivity and reacted with all the ungulate RSV strains, suggesting that these epitopes are well conserved. Based on the reactivity of three other MAbs specific to the BRSV-F protein, ungulate RSVs could be grouped into two subgroups. The results indicated that there are antigenic variations in the F protein among ungulate RSV strains.     

Analysis of adenovirus type 7 hexon hypervariable region]

The isolation of adenovirus type 7 (Ad7) has been rare in Japan in the past. However since April, 1995, many isolates of Ad 7 have been reported. In order to find the cause of Ad 7 re-emergence in Japan, we investigated the genome sequences of Ad 7 by analyzing the hexon hypervariable regions (HVRs). HVRs of genomes isolated before and after this prevalence showed little change and were closely related with each other. It was concluded that adenovirus hexon which contains HVRs is conserved in the same serotype of any genome type. At present, virus genome typing seems more suitable for comparing the differences of genomes than sequencing.     

Adenovirus type 40 virions contain two distinct fibers

Human subgroup F adenoviruses, types 40 and 41, have two genes that could specify different fiber proteins, a long fiber with 21 or 22 pseudorepeat motifs in the shaft, and a short fiber with 12 motifs. We show that for adenovirus type 40, both proteins are expressed from separate late regions of the genome. They are incorporated into the virion with only one fiber per penton base, unlike avian adenoviruses which have two fibers extending from each penton. Comparison of known adenovirus fiber sequences suggests that the two fibers in adenovirus 40 and 41 arose through an external recombination event rather than having evolved from each other directly. Two alternative fibers on the virion may imply the existence of two distinct receptors.     

Monoclonal antibodies against human immunodeficiency virus type 1 integrase: epitope mapping and differential effects on integrase activities in vitro

Human immunodeficiency virus type 1 (HIV-1) integrase (IN) catalyzes the integration of viral DNA into the host chromosome, an essential step in retroviral replication. As a tool to study the structure and function of this enzyme, monoclonal antibodies (MAbs) against HIV-1 IN were produced. Epitope mapping demonstrated that the 17 MAbs obtained could be divided into seven different groups, and the selection of MAbs representing these groups were tested for their effect on in vitro activities of IN. Four groups of MAbs recognized epitopes within the region of amino acids (aa) 1 to 16, 17 to 38, or 42 to 55 in and around the conserved HHCC motif near the N terminus of IN. MAbs binding to these epitopes inhibited end processing and DNA joining and either stimulated or had little effect on disintegration and reintegration activities of IN. Two MAbs binding to epitopes within the region of aa 56 to 102 in the central core or aa 186 to 250 in the C-terminal half of the protein showed only minor effects on the in vitro activities of IN. Three Mabs which recognized on epitope within the region of aa262 to 271 of HIV-1 IN cross-reacted with HIV-2 IN. MAbs binding to this epitope clearly inhibited end processing and DNA joining and stimulated or had little effect on disintegration. In contrast to the N-terminal-specific MAbs, these C-terminal-specific MAbs abolished reintegration activity of IN.     

Rapid detection and serotyping of adenovirus by direct immunofluorescence

Four fluorescent antibody reagents were evaluated for their suitability for the identification of adenovirus isolates by immunofluorescence. The antibodies used in the reagents consist of monoclonal antibodies against adenovirus type 3 (Ad3), Ad4, Ad8, and adenoviruses of subgroup C (Ad1,2,5,6), serotypes known to occur in outbreaks of disease. Most of the monoclonal antibodies employed were reactive against type-specific antigens found on the hexon protein. Reagents employing two noncompeting anti-hexon antibodies were more sensitive than reagents prepared with only one monoclonal antibody, although both types of reagents exhibited a high degree of specificity. Five hundred and seventeen adenovirus isolates (359 of which had previously been typed by other methods) and 46 nonadenovirus isolates were examined with all four type-specific reagents in parallel with an adenovirus group-specific reagent. The results indicate that direct typing of adenovirus isolates is feasible, leading to significant savings in time compared to other typing methods and should contribute to the management of certain adenovirus infections, particularly during outbreaks.     

Receptor binding sites and antigenic epitopes on the fiber knob of human adenovirus serotype 3

The adenovirus fiber knob causes the first step in the interaction of adenovirus with cell membrane receptors. To obtain information on the receptor binding site(s), the interaction of labeled cell membrane proteins to synthetic peptides covering the adenovirus type 3 (Ad3) fiber knob was studied. Peptide P6 (amino acids [aa] 187 to 200), to a lesser extent P14 (aa 281 to 294), and probably P11 (aa 244 to 256) interacted specifically with cell membrane proteins, indicating that these peptides present cell receptor binding sites. Peptides P6, P11, and P14 span the D, G, and I beta-strands of the R-sheet, respectively. The other reactive peptides, P2 (aa 142 to 156), P3 (aa 153 to 167), and P16 (aa 300 to 319), probably do not present real receptor binding sites. The binding to these six peptides was inhibited by Ad3 virion and was independent of divalent cations. We have also screened the antigenic epitopes on the knob with recombinant Ad3 fiber, recombinant Ad3 fiber knob, and Ad3 virion-specific antisera by enzyme-linked immunosorbent assay. The main antigenic epitopes were presented by P3, P6, P12 (aa 254 to 269), P14, and especially the C-terminal P16. Peptides P14 and P16 of the Ad3 fiber knob were able to inhibit Ad3 infection of cells.     

Synergistic neutralization of a chimeric SIV/HIV type 1 virus with combinations of human anti-HIV type 1 envelope monoclonal antibodies or hyperimmune globulins

A panel of 14 human IgG monoclonal antibodies (MAbs) specific for envelope antigens of the human immunodeficiency virus type 1 (HIV-1), 2 high-titer human anti-HIV-1 immunoglobulin (HIVIG) preparations, and 15 combinations of MAbs or MAb/HIVIG were tested for their ability to neutralize infection of cultured human T cells (MT-2) with a chimeric simian immunodeficiency virus (SHIV-vpu+), which expressed HIV-1 IIIB envelope antigens. Eleven MAbs and both HIVIGs were neutralizing. When used alone, the anti-CD4-binding site MAb b12, the anti-gp41 MAb 2F5, and the anti-gp120 MAb 2G12 were the most potent. When combination regimens involving two MAbs targeting different epitopes were tested, synergy was seen in all paired MAbs, except for one combination that revealed additive effects. The lowest effective antibody concentration for 50% viral neutralization (EC50) and EC90 were achieved with combinations of MAbs b12, 2F5, 2G12, and the anti-V3 MAb 694/98D. Depending on the combination regimen, the concentration of MAbs required to reach 90% virus neutralization was reduced approximately 2- to 25-fold as compared to the dose requirement of individual MAbs to produce the same effect. Synergy of the combination regimens implies that combinations of antibodies may have a role in passive immunoprophylaxis against HIV-1. The ability of SHIV to replicate in rhesus macaques will allow us to test such approaches in vivo.