This study was designed to test the hypothesis that T-cell effector mechanisms are required for protective immunity to malaria sporozoites. Administration of neutralizing monoclonal antibodies against gamma interferon (gamma IFN) to immune hosts, reversed sterile immunity to sporozoite challenge, by allowing the growth of exoerythrocytic forms (EEF) and thus the development of parasitaemia. Immune animals also developed infections when depleted in vivo of their suppressor/cytotoxic T cells expressing the CD8 antigen (CD8+) but not when depleted of helper T cells expressing CD4 antigen (CD4+), before sporozoite challenge. Passive transfer of immune immunoglobin alone, or adoptive transfer of immune T cells alone, conferred partial protection to naive recipients. Transfer of both immune components resulted in significantly greater protection. This transferred immunity was reversed by the in vivo neutralization of gamma IFN. Thus, sterile immunity to sporozoite challenge requires the neutralization of sporozoites by antibodies and the inhibition of EEF development by gamma IFN with the participation of CD8+ cells.

A specific DNA probe was used to study the effect of recombinant rat, mouse, and human γ-interferon (γ-IFN) on the course of sporozoite-induced malaria infections. In mice and rats infected with sporozoites of Plasmodium berghei , mouse and rat γ-IFN's strongly inhibited the development of the exoerythrocytic forms in the liver cells of the hosts, but not the development of the erythrocytic stages. The degree of inhibition of the exoerythrocytic forms was proportional to the dose of γ-IFN administered, but was independent of the number of sporozoites used for challenge. A 30 percent reduction in the development of exoerythrocytic forms in rat liver was achieved when 150 units (about 15 nanograms of protein) of rat γ-IFN were injected a few hours before sporozoite challenge; the reduction was 90 percent or more with higher doses of γ-IFN. The effect was less pronounced if the γ-IFN was administered 18 hours before or a few hours after challenge. Human γ-IFN also diminished the parasitemia in chimpanzees infected with sporozoites of the human malaria parasite Plasmodium vivax . The target of γ-IFN activity may be the infected hepatocytes themselves, as shown by in vitro experiments in which small doses of the human lymphokine inhibited the development of exoerythrocytic forms of Plasmodium berghei in a human hepatoma cell line. These results suggest that immunologically induced interferon may be involved in controlling malaria infection under natural conditions.

Human C4 and mouse Ss proteins show extensive structural homologies. They are antigenically related (1) and are composed of three polypeptide chains of similar molecular weights, linked by disulfide bonds (2, 3). In addition, it is very likely that the major histocompatibility complex of these species contains structural genes for beth proteins (3-5). However, some functional differences between the Ss protein and the C4 hemolytic activity of mouse serum have been reported (6).We recently described a new protein in mouse serum which forms complexes with the Ss protein, and also with C4 of human or guinea pig origin (7, 8). Because of the remarkable specificity of its interaction with Ss (C4) we named this protein Ss-or C4-binding protein, and suggested it ~might be a new complement component. This question could not be appropriately studied in mouse serum, whose complement system is still poorly characterized. Therefore we approached the problem by searching for a C4-binding protein (C4-bp)' analogue in human serum.In this paper we report the isolation and characterization of a human serum protein that differs from all known complement components, which has properties very similar to those of mouse C4-bp. Materials and MethodsMaterials. Dimethyl suberimidate, Aldrich Chemical Co., Inc., Milwaukee, Wis.; agarose and human transferrin, Behring Diagnostics, American Hoechst Corp., Sommerville, N. J.; Biorex 70, N, acrylamide, N,N,N',, ammonium persulfate, sodium dodecyl sulfate (SDS), Bio-Rad Laboratories, Richmond, Calif.; diisopropylfluorophosphate (DFP), Calbiochem, San Diego, Calif.; sucrose, Fisher Scientific Co.,

Rabbit liver metallothionein depleted of Cd(II) and Zn(II) was fully reconstituted using a Cu(I)-GSH complex under strictly anaerobic conditions. Anaerobic fluorescence titration, using an emission band at 625 nm which is diagnostic of the correct insertion of Cu(I) into the thiolate clusters of metallothionein, showed that the fluorescence maximum was obtained on addition of as many Cu(I) equivalents as the available Cu(I)-binding sites in the protein (i.e. 12). Binding was nearly complete within 1 min, and Cu(I)-GSH was much more efficient than Cu(I)-thiourea or Cu(I)-acetonitrile in metallothionein reconstitution. In air, full reconstitution was obtained with stoichiometric copper only when an excess of GSH was present in the reaction mixture. Cu(I)-GSH was also able to displace Zn(II) and Cd(II) from natural metallized thionein. It is concluded that: (a) Cu(I)-GSH is a potential physiological Cu(I) carrier, not only for Cu2+/Zn2+ superoxide dismutase [Ciriolo, Desideri, Paci and Rotilio (1990) J. Biol. Chem. 265, 11030-11034] but also for metallothionein; (b) in the case of metallothionein, physiological concentrations of GSH protect the protein from autoxidation in air and facilitate Cu(I)-thiolate exchange; (c) the natural metal composition of metallothionein may be related to metal bioavailability rather than to evolutionary changes in protein structure.