No abstract

The purpose of this study was to investigate the induction of inducible nitric oxide synthase (iNOS) mRNA in the brain tissue of rats and mice under the following experimental conditions: in rats infected with borna disease virus and rabies virus, in mice infected with herpes simplex virus, and in rats after the induction of experimental allergic encephalitis. The results showed that iNOS mRNA, normally nondetectable in the brain, was present in animals after viral infection or after induction of experimental allergic encephalitis. The induction of iNOS mRNA coincided with the severity of clinical signs and in some cases with the presence of inflammatory cells in the brain. The results indicate that nitric oxide produced by cells induced by iNOS may be the toxic factor accounting for cell damage and this may open the door to approaches to the study of the pathogenesis of neurological diseases.The mechanisms involved in the development of central nervous system (CNS) lesions are readily understood only in those pathological conditions in which there is evidence that a virus destroys its target cell as a direct cytopathic consequence of viral replication (e.g., polio virus or other neurotrophic viruses; refs. 1 and 2). However, the effector mechanisms involved in tissue damage associated with a far wider variety of viral infections of the CNS, involving such viruses as the measles and rubella viruses as well as human immunodeficiency virus 1, are unclear. Likewise, the mediators responsible for the CNS damage associated with chronic neurologic diseases such as multiple sclerosis remain the subject of speculation. Interestingly, morphologic analyses have revealed that lesions in affected brain tissues are frequently surrounded by infiltrating inflammatory cell populations. Although the precise role that these cells play in CNS pathology is the subject of ongoing investigation, previous studies have focused on the ability of leukocyte populations to generate proinflammatory cytokines (e.g., interleukin 1, tumor necrosis factor, etc.), neurotoxins (e.g., quinolinic acid), or reactive oxygen intermediates (3). Recently, increased attention has focused on the possibility that reactive nitrogen intermediates (NOI) generated by a family of cytochrome P-450 reductase-like enzymes, the nitric oxide synthases (NOS), directly damage host tissues in a diverse array of pathogenic states (4).To date, at least three NOS genes have been cloned and characterized, and these have been provisionally categorized on the basis of their sensitivity to regulation by Ca2+ transients (4). In this schema, NOS forms that bind calmodulin in a reversible Ca2+-dependent manner are termed the constitutive forms of NOS, and those forms of the enzyme that bind calmodulin tightly at resting [Ca2+] are termed inducible NOSs (iNOSs). After the addition of rapid-acting agonists, the constitutive NOS system generates only low levels of the NOI, nitric oxide (NO), whereas the iNOS system begins to generate NO several hours after exposure to cyto...

This report documenting the transmission of rabies virus from an organ donor to multiple recipients underscores the challenges of preventing and detecting transmission of unusual pathogens through transplantation.

Plant genetic engineering led to the production of plant-derived mAb (mAb P ), which provides a safe and economically feasible alternative to the current methods of antibody production in animal systems. In this study, the heavy and light chains of human anti-rabies mAb were expressed and assembled in planta under the control of two strong constitutive promoters. An alfalfa mosaic virus untranslated leader sequence and Lys-Asp-Glu-Leu (KDEL) endoplasmic reticulum retention signal were linked at the N and C terminus of the heavy chain, respectively. mAb P was as effective at neutralizing the activity of the rabies virus as the mammalianderived antibody (mAb M ) or human rabies Ig (HRIG). The mAb P contained mainly oligomannose type N-glycans (90%) and had no potentially antigenic ␣(1,3)-linked fucose residues. mAb P had a shorter half-life than mAb M . The mAb P was as efficient as HRIG for post-exposure prophylaxis against rabies virus in hamsters, indicating that differences in N-glycosylation do not affect the efficacy of the antibody in this model.

The need to replace rabies immune globulin (RIG) as an essential component of rabies postexposure prophylaxis is widely acknowledged. We set out to discover a unique combination of human monoclonal antibodies (MAbs) able to replace RIG. Stringent criteria concerning neutralizing potency, affinity, breadth of neutralization, and coverage of natural rabies virus (RV) isolates and in vitro escape mutants were set for each individual antibody, and the complementarities of the two MAbs were defined at the onset. First, we identified and characterized one human MAb (CR57) with high in vitro and in vivo neutralizing potency and a broad neutralization spectrum. The linear antibody binding site was mapped on the RV glycoprotein as antigenic site I by characterizing CR57 escape mutants. Secondly, we selected using phage display a complementing antibody (CR4098) that recognized a distinct, nonoverlapping epitope (antigenic site III), showed similar neutralizing potency and breadth as CR57, and neutralized CR57 escape mutants. Reciprocally, CR57 neutralized RV variants escaping CR4098. Analysis of glycoprotein sequences of natural RV isolates revealed that the majority of strains contain both intact epitopes, and the few remaining strains contain at least one of the two. In vitro exposure of RV to the combination of CR57 and CR4098 yielded no escape mutants. In conclusion, a novel combination of human MAbs was discovered suitable to replace RIG.Lethal rabies is prevented by postexposure prophylaxis (PEP) through the combined administration of a rabies vaccine and rabies immune globulin (RIG). Two types of RIG are used: human RIG (HRIG) and equine RIG, both derived from pooled sera of human donors or horses vaccinated against rabies, respectively. The need to replace these hyperimmune serum preparations is widely recognized (29), and monoclonal antibodies (MAbs) that neutralize rabies virus (RV) offer the opportunity to do so.Mouse MAbs, as well as human MAbs, have been shown to protect rodents from a lethal RV challenge (6,9,12,14,20,22,24). One of the most potent human MAbs, SO57, neutralizing a variety of RV strains, was described by Dietzschold et al. (6). A cocktail of three human MAbs including SO57 and SOJA and SOJB showed effective protection of mice from a lethal dose of RV (22). We reformatted these three MAbs (renamed CR57, CRJA, and CRJB) into our own expression system for production in PER.C6 cells (19). However, we showed that the CRJA and CRJB MAbs were not suitable in combination with CR57 for use in PEP (19) because of overlapping epitope recognition, lack of neutralizing potency, and shared escape mutants. Novel anti-RV MAbs were generated using phage display technology and were characterized with special emphasis on CR57 complementarity.We considered several criteria to be of crucial importance for the inclusion of human MAbs into a cocktail aimed at effectively blocking an RV infection in humans. First, the MAbs should target distinct, nonoverlapping epitopes and should not compete for binding to RV glyco...

During 2013, 53 reporting jurisdictions reported 5,865 rabid animals and 3 human rabies cases to the CDC, representing a 4.8% decrease from the 6,162 rabid animals and 1 human case reported in 2012. Ninety-two percent of reported rabid animals were wildlife. Relative contributions by the major animal groups were as follows: 1,898 raccoons (32.4%), 1,598 bats (27.2%), 1,447 skunks (24.7%), 344 foxes (5.9%), 247 cats (4.2%), 86 cattle (1.5%), and 89 dogs (1.5%). One human case was reported from Maryland. The infection was determined to have been transmitted via organ transplantation. Infection in the organ donor, a North Carolina resident, was retrospectively diagnosed. Both the organ donor and the organ recipient were infected with the raccoon rabies virus variant. The third human case, reported by Texas, involved a Guatemalan resident who was detained while crossing the US border. The infection was determined to be caused by a canine rabies virus variant that circulates in Central America.

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Antibodies play a central role in prophylaxis against many infectious agents. While neutralization is a primary function of antibodies, the Fc- and complement-dependent activities of these multifunctional proteins may also be critical in their ability to provide protection against most viruses. Protection against viral pathogens in vivo is complex, and while virus neutralization—the ability of antibody to inactivate virus infectivity, often measured in vitro—is important, it is often only a partial contributor in protection. The rapid fluorescent focus inhibition test (RFFIT) remains the “gold standard” assay to measure rabies virus–neutralizing antibodies. In addition to neutralization, the rabies-specific antigen-binding activity of antibodies may be measured through enzyme-linked immunosorbent assays (ELISAs), as well as other available methods. For any disease, in selecting the appropriate assay(s) to use to assess antibody titers, assay validation and how they are interpreted are important considerations—but for a fatal disease like rabies, they are of paramount importance. The innate limitations of a one-dimensional laboratory test for rabies antibody measurement, as well as the validation of the method of choice, must be carefully considered in the selection of an assay method and for the interpretation of results that might be construed as a surrogate of protection.