Antibodies-rich plasma obtained from horses can be used to treat patients infected with coronavirus disease (Covid-19), found an Indian Council of Medical Research (ICMR) pre-print study, following which it has got the regulatory nod to conduct clinical trials in humans.
For the study, 10 healthy horses between age 4 and 10 year were injected with inactivated Sars-CoV-2 antigen subcutaneously (under the skin) at the Hyderabad-based Biologicals E Ltd, and after 21 days of immunisation their plasma samples were tested. Sars-Cov-2 is the virus that causes Covid-19.
The plasma had Covid-19 specific high-quality antibodies with virus neutralising capacity, which is ideal for preventing infection. The results are in line with other studies on equine antisera that reported generation of high antibodies in horses against receptor binding area of the spike protein of the virus.
“With Biologicals E we have developed horse sera which may be considered. We have completed some animal studies where we have a predictive dose… we have got clearance for a clinical trial,” said Dr Balram Bhargava, director general, ICMR.
The virus strain was isolated from throat and nasal swab specimen of Covid-19 positive patient at the maximum containment facility of ICMR-NIV, Pune. Diseases for which equine sera has previously been tried include many viral and bacterial infections such as rabies, hepatitis B, vaccinia virus, tetanus, botulism and diphtheria.
“…This study suggests promising efficacy and therapeutic potential of equine hyper immune sera against SARS-CoV-2. The quality control assessments of the different batches proved to have consistent nAb (antibody) titres (volume of antibodies produced)… that can demonstrate consistent and high neutralization activity,” says the paper.
“Further, in-vivo testing for efficacy of this indigenously developed, cost effective product will pave the way to clinical evaluation. Additionally, being a donor independent method, this may prove as an efficient alternative to convalescent plasma for treatment of Covid-19 patients,” the researchers say.
Virologists agree that animal antisera are a good alternative. “It does have advantages over convalescent plasma as the quality of convalescent plasma is entirely donor dependent. The quality will be different from one donor to the other. Use of antibodies that have been raised in large animals is common, and has worked successfully in past. If animal study has shown promise against Sars-Cov-2 then it is good news,” said T Jacob John, former head, virology department, Christian Medical College, Vellore, Tamil Nadu.
Animal-derived plasma can help overcome the challenge of limited availability of convalescent plasma from recovered patients, and find a cost-effective alternative to monoclonal antibodies (man-made proteins that act like human antibodies in the immune system)that are laborious and expensive to generate.