The complementary DNA sequence encoding the Mr 28,000 antigen of Schistosoma mansoni has been isolated and expressed in Escherichia coli. Experimental vaccination of rats, hamsters and monkeys with a recombinant fusion protein induces a strongly cytotoxic antibody response. Immunization of rats and hamsters with this protein leads to significant protection against a natural challenge infection with live cercariae.

A protective Mr28K antigen of Schistosoma mansoni, expressed from its cDNA, has been purified in a single step and shown to possess glutathione (GSH) transferase activity as predicted from sequence homologies with two mammalian GSH transferase multigene families. It is notable for its high 1‐chloro‐2,4‐dinitrobenzene GSH transferase and linoleic acid hydroperoxide GSH peroxidase activities. The major GSH transferase of S. mansoni has been purified and its subunit is identical to this Mr28K antigen by criteria of Mr, immunochemistry, substrate specificity and peptide sequence analysis. In the parasite, the antigen is present in the tegument, protonephridial cells and subtegumental parenchymal cells. No significant immunological cross‐reactivity between the S.mansoni and mammalian (human and rat) GSH transferases was observed.

Interaction of human V-interferon (IFN-y) with a cell-surface receptor is known to be essential for the cell to become resistant to viral infection. Here we demonstrate that IFN-y, when present inside the cell, is also capable of inducing a permanent antiviral state. Mouse cells transformed with a truncated human cDNA encoding a mature IFN-y protein lacking the signal peptide accumulate high levels of intracellular human IFN-y. Not only do these cells acquire a permanent resistance to viral infection, they also exhibit all the biochemical characteristics normally observed after exposure to exogenous IFN. The observed loss of species specificity normally associated with IFN-y suggests that this restriction is strictly dependent on the interaction of the molecule with the cell-surface receptor.It is generally accepted that the first and obligatory step for interferon (IFN) to exert its antiviral effect resides in its binding to specific receptors located on the cell membrane (1). Some evidence demonstrates that IFN acts from outside the cell in the same manner as many polypeptide hormones (2). In this model after viral infection, those cells that produce IFN would not become resistant to the virus but secrete the molecule, thus protecting other uninfected cells exhibiting the IFN receptor.The availability of important amounts of homogeneous IFN has made it feasible to study the nature of these receptor complexes. As a result, two different receptors have been reported (3, 4): one specific for the two antigenically distinct IFN-a and IFN-,B, and a second one that is recognized specifically by IFN-y.Two models for the mechanism of action of IFN are postulated: interaction with the IFN receptor is sufficient to generate the primary signal(s), or internalization of IFN is required to trigger the cellular response.Recently, it has been shown that the initial receptor-ligand complex was rapidly internalized under physiological conditions by virtue of a well-documented phenomenon known as receptor-mediated endocytosis (5).The internalization of IFN-a (6) is followed by its subsequent degradation, presumably after transportation into lysosomes. Similar results have been observed for human IFN-y (HuIFN-y) (7). However, murine IFN-y (MuIFN-y) appears to be stable in L1210 cells for as long as 12 hr after uptake of the molecule (8).It has recently been demonstrated that specific receptors for both IFN-f3 and IFN-y could be detected on the nuclear membrane of L cells (9, 10). This would suggest that the internalized MuIFN is able to modulate regulatory functions of the nucleus as well as the expression of specific genes.

Parameters influencing the efficiency of expression of the human immune interferon (IFN-gamma) gene in E. coli were studied by comparing a series of eight in vitro-derived gene variants. These contained all possible combinations of silent mutations in the first three codons of the mature IFN-gamma polypeptide coding sequence. Expression levels varied up to 50-fold among the different constructions. Comparison of messenger RNA secondary structure models for each variant suggested that the presence of stem-loop structures blocking the translation initiation signals could drastically decrease the efficiency of IFN-gamma synthesis. With variants displaying no stable mRNA secondary structure in the region, a C----U transition at position +11 after the AUG resulted in a 5-fold increase in expression indicating that RNA primary structure also plays an important role in expression. In addition we demonstrate that, in this system, a spacing of 8 nucleotides between the Shine-Dalgarno region and AUG was optimal for gene expression and that the steady-state production level of IFN-gamma rose exponentially with increasing rate of synthesis.

A full-size cDNA sequence coding for insulin-like growth factor I (IGF-I) was isolated from a human liver library. For the construction of this bank, a new method was developed which anneals dG-tailed cDNA with a synthetic adaptor 5'-AATTCCCCCCCCCCC-3' followed by ligation into the EcoRI site of a lambda immunity-insertion vector. Based on the sequence analysis of the complete IGF-I messenger we concluded that the protein is synthesized as a precursor containing a signal peptide of 22 or 25 amino acid residues. In addition, the sequence extended in the 3'-direction and showed the presence of multiple polyadenylation sites in the IGF-I message.insulin-like growth factor I cDNA