Most modern drugs produced through biotech route could contain animal-derived molecules that can potentially prove lethal to humans, says a new study conducted in the United States.

Sialic acid, the culprit agent, appears on the surfaces of cells and is found in all mammals. This sugar molecule helps the cells interact with each other and within their environment.

Different mammals have different kinds of sialic acid varieties within their cells. However, there are two major types of this sugar -- Neu5Gc and Neu5Ac – that are more common in mammals. Humans lack Neu5Gc which is found in chimpanzees and gorillas.

If the Neu5Gc version of animal sialic acid enters the human body, it could trigger an immune reaction that can have a damaging inflammatory effect in some individuals, say the researchers, who found that many modern biotech drugs derived from animal sources are contaminated with this sugar.

"It is reasonable to suggest that for some patients who have problems with some drugs, this may be part of the reason why," said Professor Ajit Varki, who led the research, and published the results in the latest issue of the journal Nature Biotechnology.

"Sialic acids are required for survival, but they're also used to attack you. They are crucial for things like brain plasticity and kidney function, but lots of pathogens (harmful agents) attach to them, and some even coat themselves with these sugars to avoid detection, says Prof Varki, a scientist with the University of California at San Diego (UCSD).

So, the researchers believe that an immune response triggered by this hostile sialic acid could turn fatal. Previously it was believed that healthy human immune systems will be unaffected by non-human sialic acid.

"Now we know that to be untrue," Prof Varki says adding, "It is part of our diet, and especially abundant in red meat. We all develop antibodies to Neu5Gc, but this immune response varies greatly in people. However, Neu5Gc from animal foods can get incorporated into the human body.’’

For most people, this may not be a problem. But for some, the immune response to incorporated Neu5Gc may exacerbate a chronic inflammation process. While this alone may not be the cause of any disease or condition among the patients, but the study suggests that it might be like adding fuel to an existing fire.

The San Diego scientists studied several currently used biotech drugs derived from animal proteins and discovered non-human sialic acid in almost all of them.