New Delhi, Sept. 5: The Zika virus which can cause devastating brain damage in unborn foetuses may some day be used to treat glioblastoma, the most common and deadliest of malignant brain tumours, researchers said today.
Two medical research groups in the US have shown through lab studies that the capacity of the Zika virus to infect foetal brain cells may be harnessed to selectively target glioblastoma, currently treated with surgery, chemotherapy and radiation, but considered incurable tumours.
The scientists found that the Zika virus can preferentially infect and kill glioblastoma stem cells which proliferate and give rise to more tumour cells, driving the growth of the tumour. They also found that mice with brain tumours injected with the Zika virus survived much longer than the those that received only saltwater injections as placebo.
The researchers have reported their findings today in The Journal of Experimental Medicine. "We see Zika one day being used in combination with current therapies to eradicate the whole tumour," Milan Chedda, assistant professor medicine and neurology and team member at the Washington University School of Medicine (WUSM), St Louis, said in a release.
The World Health Organisation had declared a public health alert after data from outbreaks in Brazil among other countries since 2015 pointed to an association between the Zika virus infections - which are spread primarily by mosquitoes - and foetal brain disorder called microcephaly.
In September 2016, Lakshmi Rajagopal, an Indian-origin scientist in the US, and her colleagues had for the first time shown direct evidence of foetal brain injury after maternal infection with the Zika virus through studies in pig-tailed macaques. Another research team at the Johns Hopkins University School of Medicine had shown last year that the Zika virus selectively infects stem cells in the brain.
Against the backdrop of such observations, Chedda and his colleagues decided to pit the Zika virus against glioblastoma stem cells. "We found that the Zika virus can kill the kind of glioblastoma cells that tend to be resistant to current treatments and lead to death," Michael Diamond, professor of medicine at WUSM and the paper's senior co-author, said in the release.
The current standard therapy for glioblastoma is surgery in combination with chemotherapy and radiation. But despite the most advanced treatment regimens, doctors have observed that the tumours recur, with less than 10 per cent of patients alive five years after first diagnosis.
The new studies point to a complementary role for the Zika virus with chemotherapy and radiation. While standard treatment kills the main tumour cells, the virus attacks the stem cells which serve as progenitors for fresh tumour cells.
The Zika virus infection remains symptom-less in most adults or causes only mild symptoms such as fever, rash, headache, joint pain or conjunctivitis in some. The strategy of deploying the Zika virus to treat the brain tumours "could be used with acceptable toxicity", said Jeremy Rich, a team member at the University of California, San Diego.
The scientists injected the Zika virus into brain tissue extracted from patients with epilepsy and found that it did not infect non-cancerous brain cells. The researchers introduced two mutations in the virus that would allow it to grow in tumour cells but be quickly eliminated in healthy cells.
If and when such a strategy goes into clinical trials, researchers would need to inject the Zika virus into the brains of patients with glioblastoma, most likely during surgery to remove the primary tumour. If injected elsewhere in the body, the immune system would quickly eliminate the virus.