The human immunodeficiency virus (HIV) has proven once again that it is one tough nut to crack. The deadly virus mutated to survive the latest promising HIV cure.

In a previous report, researchers introduced a promising HIV cure that uses the CRISPR/Cas9 gene-editing tool that seeks out, recognizes and snips a particular sequence of the HIV genome, effectively crippling the HIV virus. A team of researchers from McGill University in Montreal, Canada tested the gene-editing tool to an HIV-infected T-Cell and got a positive result.

However, just after a few weeks later, they have discovered that copies of the virus' particles that escaped the CRISPR/Cas9 attack were being pumped by the treated T-Cell, Scientific American reported. Upon DNA sequencing of the escaped virus, researchers learned that the escaped virus has also developed mutations that change the sequence of HIV, making it unrecognizable to CRISPR/Cas9.

According to the study published in the journal Cell Reports, researchers believed that the mutation of the HIV sequence was a result of the insertions and deletions (indels) of DNA letters produced as the cells' repair mechanism to heal itself after the HIV genome was snipped by CRISPR.

These indels are proven to be lethal to the deadly HIV virus, but researchers have discovered that some indels may have contributed to the emergence of replicating competent and unrecognizable virus. However, researchers don't consider this error as a setback to attaining an HIV cure but view it as a stepping stone for success.

"We have a long road toward the goal, and there may be many barriers and limitations that we need to overcome, but we're confident that we will find success," author of the study Chen Liang, Senior Investigator at the Lady Davis Institute at the Jewish General Hospital and the Associate Professor of Medicine at the McGill University AIDS Centre, said in a statement via EurakAlert.

The study was a collaborative effort between researchers at McGill University and the University of Montreal in Canada as well as the Chinese Academy of Medical Sciences and Peking Union Medical College in China.