Resistance to biological and chemical challenge in rodents treated with xerosin II, a natural product of Achromobacter xerosis.

The biological response-modifying activity of acid-precipitable material from Achromobacter xerosis was first described as suppression of viral pneumonia in mice. Later, this acid-precipitable material (xerosin) was found to have antiinflammatory activity and to induce tumor regression in chickens infected with Rous sarcoma virus. Here, we report further purification of xerosin resulting in a product (xerosin II) that retains high biological activity against viral and endotoxin-induced pneumonia in mice. In addition, we describe new activities of xerosin II in two rat tumor systems. Female CD rats received gastric intubations of 7,12-dimethylbenz(a)anthracene; 2 weeks later, half began 4 weeks of treatment with xerosin II, while others received saline only. Xerosin II treatment significantly delayed the appearance of the first palpable mammary tumors per rat. In female F344 rats implanted with the 13762 mammary tumor, 4 weeks of xerosin II treatment prolonged the survival of rats by an average of 5-11 days (12-24%) in two separate trials. Tumor growth and incidence of metastasis appeared unaffected by xerosin II treatment. Thus, this refined bacterial extract proved to be a potent biological response modifier in four different rodent systems.