Monoclonal Antibodies for Detection of Rabies Virus Antigen and Confirmatory Rabies Diagnosis

According to the World Health Organization (WHO), rabies causes greater than 59,000 deaths every year in over 150 countries as of 2017. A rapid and reliable diagnostic test for rabies is critical for prophylaxis considerations in humans bitten by animals as well as for basic surveillance and animal rabies control programs. The World Organization of Animal Health (OIE) and WHO Expert Committee on Rabies recently approved the direct rapid immunohistochemical test (DRIT) for rabies diagnostics. DRIT uses a light microscope and does not require any specialized equipment such as a freezer and incubator. There is a critical need for the reagents used for DRIT, however, as they are not currently available from any commercial source.

To meet this need, CDC researchers developed four murine anti-rabies monoclonal antibodies (mAbs), then prepared two cocktails for use in DRIT as reagents to detect rabies virus (RABV) antigen in just over 1 hour using a light microscope to read slides. The mAbs have demonstrated high sensitivity and specificity for detection of RABV and non-rabies lyssaviruses antigen. The first cocktail has the ability to detect all the RABV variants that circulate in North America, and the second cocktail of two mAbs has the ability to recognize non-rabies lyssaviruses found outside the Americas. The DRIT technique with CDC’s technology can be used for routine rabies diagnosis and enhanced rabies surveillance, particularly in conjunction with oral rabies wildlife vaccination and canine rabies elimination programs. A diagnostic DRIT kit has been designed in quantities compatible with use by low and high volume laboratories without wastage packaged in convenient 10 ml bottles capable of testing 100-200 samples. This technique offers an alternative method to direct fluorescent antibody testing (DFA) for primary diagnosis of RABV infection in infected patients or animals and adaptability for field testing. The mAbs are currently in production.