MOLECULAR AND STRUCTURAL REQUIREMENTS OF A LIPOTEICHOIC ACID FROM ENTEROCOCCUS-HIRAE ATCC-9790 FOR CYTOKINE-INDUCING, ANTITUMOR, AND ANTIGENIC ACTIVITIES

Comparison was made between the immunobiological and antigenic propert ies of two lipoteichoic acid (LTA) fractions (LTA-1 and -2) from Enter ococcus hirae ATCC 9790, their glycolipid portions, and synthetic comp ounds partially mimicking the above bacterial products, The more lipop hilic LTA-2 fraction was capable of inducing serum tumor necrosis fact or alpha and interleukin-6 in muramyldipeptide-primed mice and serum g amma interferon in those primed with Propionibacterium acnes. The LTA- 2 fraction also induced tumor necrosis factor alpha, interleukin-6, an d thymocyte-activating factor (essentially interleukin-l) in murine pe ritoneal macrophage cultures, Consecutive intravenous injections of mu ramyldipeptide and the LTA-2 fraction in Meth A fibrosarcoma-bearing B ALB/c mice caused hemorrhagic necrosis and marked regression leading t o complete regression of the tumor with no accompanying weakening or l ethal effects. The LTA-2 fraction was at least 10,000-fold less pyroge nic in rabbits than a reference endotoxic lipopolysaccharide. The more hydrophilic LTA-1 fraction, on the other hand, showed at most margina l activity in the in vivo and in vitro assays. Natural glycolipids (NG L-1 and -2) which were prepared from a chloroform-methanol extract of Streptococcus pyogenes and E. hirae cells, and comparable in structure to the lipid moieties of the LTA-1 and -2 fractions, respectively, we re practically inactive in all of the assays. None of the test synthet ic compounds was immunobiologically active, although synthetic partial counterparts of the structure of LTA proposed by W. Fischer (Handb. L ipid Res. 6:123-234, 1990) reacted with murine monoclonal antibody TS- 2, which was raised against OK-432, a penicillin-killed S.pyogenes pre paration, and capable of neutralizing the cytokine-inducing activities of the LTA-2 fraction.