The ability to produce monoclonal antibodies (Mabs) in plants offers the opportunity for the development of an inexpensive method of mucosal immunoprotection against sexually transmitted diseases. To investigate the suitability of plant-expressed Mabs for vaginal preventive applications, we compared a humanized anti-herpes simplex virus 2 (HSV-2) Mab expressed in mammalian cell culture with the same antibody expressed in soybean. We found these Mabs to be similar in their stability in human semen and cervical mucus over 24 h, their ability to diffuse in human cervical mucus, and their efficacy for prevention of vaginal HSV-2 infection in the mouse.

By atomic absorption analysis, we determined that the reovirus outer capsid protein cr3, which binds double-stranded RNA (dsRNA), is a zinc metalloprotein. Using Northwestern blots and a novel zinc blotting technique, we localized the zinc-and dsRNA-binding activities of cr3 to distinct V8 protease-generated fragments. Zinc-binding activity was contained within an amino-terminal fragment that contained a transcription factor IIIA-like zinc-binding sequence, and dsRNA-binding activity was associated with a carboxyterminal fragment. By these techniques, new zinc-and dsRNA-binding activities were also detected in reovirus core proteins. A sequence similarity was observed between the catalytic site of the picornavirus proteases and the transcription factor lIlA-Like zinc-binding site within a3. We suggest that the zinc-and dsRNA-binding activities of cr3 may be important for its proposed regulatory effects on viral and host cell transcription and translation.The mammalian reoviruses represent the prototype of a group of nonenveloped plant and animal viruses whose segmented, double-stranded RNA (dsRNA) genomes are surrounded by an inner capsid core and an outer capsid shell. Three serotypes of mammalian reoviruses have been identified, and the different strains of these viruses studied to date have been found to vary with respect to a number of biochemical markers and biological properties. As a result of these polymorphisms, reoviruses offer an excellent model system for the study of virion morphogenesis and virus-host cell interactions because the genetic analysis of reassortant viruses has provided a means to assign biological phenotypes and biochemical properties to particular viral genome segments. Results of studies with reassortant viruses have suggested that, in addition to playing structural roles, the reovirus outer capsid proteins influence the virus-host cell interaction at a variety of stages in the viral replicative cycle. S4, the smallest of the 10 mammalian reovirus genes, encodes the a3 protein (38, 40), a major component of the virion outer capsid (53). The or3 protein is the only reovirus protein that has been reported to have affinity for dsRNA (27). This is an unusual property for an outer capsid protein which is removed from infecting parental virus by protease digestion early in infection (52, 55), and suggests that this property may be one of newly synthesized a3 that operates in the cell cytoplasm. Results of biochemical and genetic studies have implied a role for the S4 gene product in the regulation of viral transcription (4) and translation (33, 34), the inhibition of host cell RNA and protein synthesis (50), and the establishment of persistent reovirus infection (1). To begin to determine whether the ability of cr3 to bind to dsRNA is mechanistically important for virion morphogenesis or any of the biological properties which have been mapped to the S4 gene segment, we initiated a study to investigate the structural basis for the dsRNA-binding activity of cr3. * Corresponding author. A re...

The monoclonal anti-idiotypic antibody (mAb2) 87.92.6 directed against the 9B.G5 antibody specific for the virus neutralizing epitope on the mammalian reovirus type 3 hemagglutinin was previously demonstrated to express an internal image of the receptor binding epitope of the reovirus type 3. Furthermore, this mAb2 has autoimmune reactivity to the cell surface receptor of the reovirus. The nucleotide and deduced amino acid sequences of the 87.92.6 mAb2 heavy and light chains are described in this report. The sequence analysis reveals that the same heavy chain variable and joining (VH and JH) gene segments are used by the 87.92.6 anti-idiotypic mAb2 and by the dominant idiotypes of the BALB/c anti-GAT (cGAT) and anti-NP (NP3) responses. [GAT; random polymer that is 60% glutamic acid, 30% alanine, and 10% tyrosine. NP; (4-hydroxy-3-nitrophenyl)-acetyl.] Despite extensive homology at the level of the heavy chain variable regions, the NP3 positive BALB/c anti-NP monoclonal antibody 17.2.25 binds neither 9B.G5 nor the cellular receptor for the hemagglutinin. Amino acid sequence comparison between the viral hemagglutinin and the 87.92.6 mAb2 light chain "internal image," reveals an area of significant homology indicating that antigen mimicry by antibodies may be achieved by sharing primary structure.

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A cell-surface receptor for the mammalian reovirus type 3 hemagglutinin was isolated by using antiidiotypic anti-receptor antibodies. The receptor is a glycoprotein with a molecular mass of 67,000 daltons and a pI of 5.9. Evidence that the isolated structure represents the reovirus receptor was obtained by electrophoretic immunoblot studies, which demonstrated that the 67,000-dalton glycoprotein is the only cell-surface structure recognized by both reovirus type 3 and the anti-receptor immunoglobulin. Comparison of the reovirus receptor on murine thymoma (R1.1) and rat neuroblastoma (B104) cells indicated that similar structures on the cell surface are recognized by the reovirus type 3 and the anti-receptor antibodies as previously suggested from cellular and binding studies. This receptor was found on mouse, rat, monkey, and human cells. Furthermore, diverse tissue ypes, including lymphoid and neuronal cells, express the receptor structure. The receptor structure is discussed in terms of its role in mediating viral tropism and as an essential cell-surface protein.