A broad-spectrum and highly potent human monoclonal antibody cocktail for rabies prophylaxis

Development of Human Monoclonal Antibodies With Broad Reactivity for Rabies Postexposure Prophylaxis

Rabies is an acute lethal disease causing by the neurotropic virus rabies virus (RABV). Rabies immune globulin (RIG) as an indispensable component of rabies postexposure prophylaxis (PEP) always faces with great challenges in terms of costs, stability and safety. Our objective is to develop a novel and potential fully human monoclonal antibodies (mAbs) cocktail for the improvement of rabies PEP. The neutralizing fully human mAbs were screened by using fully humanized antibody mice (CAMouseHG). Then, two mAbs 26-12 G and 5-7 G were selected with potential neutralizing activity to RABV by using fluorescent antibody virus neutralization test (FAVN), which specifically bind to antigenic sites I and III of RABV-glycoprotein (RABV-G), the key amino acid residues were further identified in position 336, 337 of 5-7 G and 226, 227, 228 of 26-12 G by using cross-linking and mass-spectrometry. Both mAbs are highly conserved across 8 RABV strains (distributing in 3 lineages: Asian, Cosmopolitan and Arctic-related) and 1 IRKV strain, and showed high neutralizing potential. Moreover, the in vivo experiment demonstrated that our cocktail can protect Kunming mice from a lethal RABV challenge. Collectively, we generate two noncompeting fully human mAbs (26-12 G, 5-7 G) and obtained cocktail CAM001 with their mixture. The high-potency and broad-spectrum neutralization of the cocktail supports its utility in human rabies PEP as an efficacious and affordable alternative to RIG products, particularly in endemic areas.

Development of novel canine phage display-derived neutralizing monoclonal antibody fragments against rabies virus from immunized dogs

Animal rabies is a potentially fatal infectious disease in mammals, especially dogs. Currently, the number of rabies cases in pet dogs is increasing in several regions of Thailand. However, no passive postexposure prophylaxis (PEP) has been developed to combat rabies infection in animals. As monoclonal antibodies (MAbs) are promising biological therapies for postinfection, we developed a canine-neutralizing MAb against rabies virus (RABV) via the single-chain variable fragment (scFv) platform. Immunized phage-displaying scFv libraries were constructed from PBMCs via the pComb3XSS system. Diverse canine VHVLκ and VHVLλ libraries containing 2.4 × 108 and 1.3 × 106 clones, respectively, were constructed. Five unique clones that show binding affinity with the RABV glycoprotein were then selected, of which K9RABVscFv1 and K9RABVscFv16 showed rapid fluorescent foci inhibition test (RFFIT) neutralizing titers above the human protective level of 0.5 IU/ml. Finally, in silico docking predictions revealed that the residues on the CDRs of these neutralizing clones interact mainly with similar antigenic sites II and III on the RABV glycoprotein. These candidates may be used to develop complete anti-RABV MAbs as a novel PEP protocol in pet dogs and other animals.

Antiviral mechanisms of two broad-spectrum monoclonal antibodies for rabies prophylaxis and therapy

Rabies is an acute and lethal encephalomyelitis caused by lyssaviruses, among which rabies virus (RABV) is the most prevalent and important for public health. Although preventable through the post-exposure administration of rabies vaccine and immunoglobulins (RIGs), the disease is almost invariably fatal since the onset of clinical signs. Two human neutralizing monoclonal antibodies (mAbs), RVC20 and RVC58, have been shown to be effective in treating symptomatic rabies. To better understand how these mAbs work, we conducted structural modeling and in vitro assays to analyze their mechanisms of action, including their ability to mediate Fc-dependent effector functions. Our results indicate that both RVC20 and RVC58 recognize and lock the RABV-G protein in its pre-fusion conformation. RVC58 was shown to neutralize more potently the extra-cellular virus, while RVC20 mainly acts by reducing viral spreading from infected cells. Importantly, RVC20 was more effective in promoting effector functions compared to RVC58 and 17C7-RAB1 mAbs, the latter of which is approved for human rabies post-exposure treatment. These results provide valuable insights into the multiple mechanisms of action of RVC20 and RVC58 mAbs, offering relevant information for the development of these mAbs as treatment for human rabies.