Several species of cyanobacteria has been recognized for its therapeutic value that can be used for treatment of malnutrition, cancer and viral infection. Many natural occurring cyanobacteria are known to produce toxins, for example, species of the genera Microcystis, Nodularia, Nostoc, Anabaena, Aphanizomenon, Cylindrospermopsis, and Planktothrix (Oscillatoria). Cyanotoxins are classified according to their mode of action in vertebrates as hepatotoxins, neurotoxins, cytotoxins, dermatotoxins, and irritants. Microcystin is a hepatotoxin which commonly found in Microcystis and it was found to be produced by other genera, including Anabaena, Nostoc, Nodularia, and Planktothrix. In the present study cyanobacteria strain isolated from Egyptian soil was purified, characterized and identified as Nostoc sp. and named Nostoc EGY. PCR-based techniques targeting the toxin biosynthesis genes were used verifying absence of toxic genes in the newly purified cyanobacteria. Cell lysate was prepared from the purified strain; the efficacy of this lysate to prevent hepatitis C virus (HCV) replication in vitro was proved qualitatively and quantitatively. Lysate prepared from isolated cyanobacteria after 10 and 25 days of cultivation was able to prevent replication of in vitro cultivated HCV.

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