Horseshoe crab blood may be crucial for development of an effective COVID-19 vaccine

In their desperate bid to come up with a cure, experts are now looking at harvesting horseshoe crab blood. Read on to know more.

By: Jahnavi Sarma | | Updated: July 11, 2020 1:23 pm

Safety tests using horseshoe crab blood is currently the industry standard. Because of this, these crabs may have an important role to play in vaccine development.

The current global health crisis has triggered a desperate search for an effective vaccine that can provide protection against the COVID-19 virus. After suffering numerous setbacks, scientists have now found some hopeful candidates. But if recent reports from the scientific community are to be believed, things seem to have got a bit weirder. In their desperate bid to come up with a cure, experts are now looking at harvesting horseshoe crab blood. Also Read - COVID-19 may have longer incubation period than previously thought

Apparently, the crab’s milky-blue blood is the only known natural source of limulus amebocyte lysate (LAL), a substance that detects a contaminant called endotoxin. Even a minute amount of this bacterial toxin in vaccines and injectable drugs can be fatal for recipients. The blood of horseshoe crabs is extremely sensitive to endotoxin and it turns to gel or clots when it comes in contact with this toxin. In 1956, medical researcher Fred Bang discovered that when horseshoe crab blood interacts with endotoxin, cells called amebocytes clot and form a solid mass. These amebocytes, which are a part of the crab’s ancient immune system, can detect deadly bacterial contaminants in drugs designed to enter the human bloodstream. Eventually, scientists found a way to use the amebocyte lysate to test drugs and vaccines. In 1977, the U.S. Food and Drug Administration (FDA) approved horseshoe crab lysate for this use. Also Read - Moderna’s COVID-19 vaccine is at Phase 3 trial: Preclinical and clinical trials explained

Role of this crab in COVID-19 vaccine development

There are currently more than 400 COVID-19 drugs and vaccines in various stages of development. Safety tests using horseshoe crab blood is currently the industry standard. Because of this, these crabs may have an important role to play in vaccine development. To test for bacterial contamination in medical products, the world almost solely relies on a single source of lysate – the blood of two species of the horseshoe crab family that are endangered. However, acknowledging ecological concerns, many pharmaceutical companies use a synthetic alternative to the blood of horseshoe crabs in safety trials for medical products. Also Read - COVID-19 Live Updates: Cases in India surge to 21,53,010 as death toll reaches 42,518

Will alternatives work just as well?

However, the process of catching and harvesting the blood of these crabs is a time-consuming process. It is also an expensive procedure with the resulting lysate costing $60,000 per gallon. Hence, in 2016, a synthetic alternative to crab lysate, recombinant factor C (rFC), was approved as an alternative in Europe. Following this, a few US drug manufacturers also began using it. But then, recently in June this year, the American Pharmacopeia, which sets the scientific standards for drugs and other products in the US, declined to place rFC on equal footing with crab lysate. According to them, its safety is still not a proven fact. They were unsure if the recombinant factor C (rFC) can be used in the bacterial contamination tests instead of the classic limulus amoebocyte lysate (LAL)-based methods that rely on blood from the crabs.

But according to the European Directorate for the Quality of Medicines and Healthcare (EDQM), when used under appropriate conditions, rFC-based methods provide the same guarantee of a product’s compliance with the test for bacterial endotoxins – and therefore, of its safety for use in patients – as LAL-based methods.

(With inputs from Agencies)

Published : July 11, 2020 1:21 pm | Updated:July 11, 2020 1:23 pm

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