Monoclonal antibodies (MAbs) to the capsular polysaccharide of the pathogenic fungus Cryptococcus neoformans can prolong survival and decrease organ fungal burden in experimental murine cryptococcosis. To investigate the mechanism of antibody-mediated protection, the interaction of C. neoformans and murine macrophage-like J774.16 cells was studied in the presence and absence of MAbs differing in isotype. Immunoglobulin G2a (IgG2a) and IgG2b isotype switch variants were isolated from an IgM hybridoma to complete the IgG subclass set. IgM, IgG1, IgG2a, IgG2b, IgG3, and IgA MAbs were studied for their ability to promote phagocytosis and reduce the number of CFU in C. neoformans and J774.16 cell cocultures. The MAbs in this set had similar if not identical fine specificities and were derived from a single B cell. All isotypes promoted phagocytosis; however, the IgG subclasses were more effective opsonins than IgM or IgA. All isotypes enhanced J774.16 anti-C. neoformans activity in vitro, as measured by a reduction in the number of CFU. The IgG1 MAbs were consistently more active in promoting opsonization and reducing the number of CFU. Addition of IgG1 MAb to C. neoformans and J774.16 cocultures resulted in rapid reduction in the number of CFU, which is consistent with fungal killing. Electron microscopy revealed that MAb-opsonized C. neoformans cells were internalized and appeared damaged. Administration of IgM, IgG1, IgG2a, and IgG2b isotype switch variant MAbs revealed that the IgG2a and IgG2b subclasses were the most and least effective isotypes, respectively, in prolonging survival in an intraperitoneal murine infection model. The results indicate that murine antibody subclasses differ in their ability to enhance macrophage anti-C. neoformans activity and suggest that antibody enhancement of macrophage function is a mechanism by which antibodies modify infection in vivo.

Immunoglobulin Gl (IgGl) monoclonal antibodies (MAbs) to the capsular glucuronoxylomannan (GXM) were studied for their ability to modify the course of intravenous Cryptococcus neoformans infection in mice. A/J mice were given intraperitoneal injection of 1.0 mg of either a GXM-binding IgGl MAb (2H1 or 2DlOyl) or the irrelevant isotype-matched control MAb 36-65 prior to intravenous infection. Parameters used to study antibody efficacy were lung and brain tissue fungal burden, lung and brain weights, serum GXM levels, and histopathological examination of lung, brain, heart, kidney, and spleen tissues. Mice given GXM-binding MAb had significantly reduced lung tissue fungal burden as measured by CFU. In contrast to the reduction in lung tissue burden, the reduction in brain tissue burden was small and did not achieve statistical significance. Serum GXM levels were reduced in mice receiving GXM-binding MAb. Histopathological examination revealed reduced numbers of granulomas and C. neofornans organisms in the lungs, brains, and kidneys of MAb 2H1-treated mice relative to control mice. The lungs and brains of mice receiving GXM-binding MAb weighed significantly less than those of control animals, consistent with the reduced inflammation noted histologically. Subendocardial inflammation and kidney cortical infarctions were present in control infected mice but not in MAb 2H1-treated mice. Immunocytochemical staining for polysaccharide antigen revealed a marked reduction in the amount of tissue polysaccharide in mice treated with MAb 2H1 relative to control mice. The results support an useful role for passive antibody administration in C. neoformans infections.

Passive antibody administration is a potentially useful approach for the therapy of human Cryptococcus neoformans infections. To evaluate the efficacy of the human immunoglobulin Gl (IgGl) constant region against C. neoformans and to construct murine antibody derivatives with reduced immunogenicities and longer half-lives in humans, two mouse-human IgGl chimeric antibodies were generated from the protective murine monoclonal antibodies 2D10 (IgM) and 18B7 (IgGl). The 2D10 mouse-human IgGl chimeric antibody (ch2D10) had significantly lower binding affinity than its parent murine antibody (m2D10), presumably because of a loss of avidity contribution on switching from IgM to IgG. The 18B7 mouse-human IgGl chimeric antibody (chl8B7) had higher affinity for cryptococcal polysaccharide antigen than its parent murine antibody (ml8B7). chl8B7 and ch2D10 promoted phagocytosis of C. neoformans by primary human microglial cells and the murine J774.16 macrophage-like cell line. chl8B7 and m18B7 enhanced fungistatic or fungicidal activity ofJ774.16 cells and prolonged the survival of lethally infected mice. We conclude that the human IgGl constant chain can be effective in mediating antifungal activity against C. neoformans. chl8B7 or similar antibodies are potential candidates for passive antibody therapy of human cryptococcosis.Immunosuppressed individuals are particularly susceptible to infections with the fungus Cryptococcus neoformans. In recent years the prevalence of cryptococcal infections has increased dramatically because this fungal infection occurs in up to 10% of patients with AIDS (72). In the setting of AIDS C. neoformans infections are particularly difficult to treat because antifungal therapy does not eradicate the infection (67) despite in vitro susceptibility to drugs used in therapy (12).AIDS patients who survive the initial presentation undergo lifelong antifungal suppression therapy to decrease the likelihood of relapse. The difficulty of treating C. neoformans infections in immunocompromised patients has led to interest in the potential of passive antibody therapy as a means to enhance residual cellular immunity (8, 23, 51-53, 55, 63). Limited experience with the use of rabbit polyclonal antibody in humans suggests that the combination of antibody with amphotericin B may improve therapy (29,31,47). Experimental support for a combined approach includes the finding that antibody can potentiate the antifungal effect of amphotericin B in murine models of cryptococcosis (22,30,54).The ability of passive antibody to mediate protection in murine models of C. neoformans infection is dependent on the quantity (23), isotype (53,63), and fine specificity (53) of the antibody reagent and the animal model used (23-25, 35, 53). Antibody to C. neoformans capsular polysaccharide does not inhibit the fungus in the absence of effector cells (24), and antibody-mediated protection is most likely the result of enhanced cellular and nonspecific immune mechanisms (10,19,20,40,42,57,63). Antibodies to the capsular polysacchar...

We report dual ion beam sputtering fabrication of an Al/ZnO/Al memristor displaying forming-free bipolar resistive switching characteristics with memristive behavior without necessitating any post-processing steps. A nearly amorphous ZnO thin film and an appropriate concentration of oxygen vacancies play a significant role in imparting forming-free, stable, and reliable behavior to memory cells. Besides, sufficient non-lattice oxygen ions in the film play a crucial role in the resistive switching process. The AlOx interface layer is observed to strongly affect the switching mechanism in the memory device by altering the barrier at the Al/ZnO interface. The device shows stable switching behavior for >250 cycles with good retention and stable set/reset voltages.

Single synaptic device with inherent learning and memory functions is demonstrated based on a forming-free amorphous YO (yttria) memristor fabricated by dual ion beam sputtering system. Synaptic functions such as nonlinear transmission characteristics, long-term plasticity, short-term plasticity and 'learning behavior (LB)' are achieved using a single synaptic device based on cost-effective metal-insulator-semiconductor (MIS) structure. An 'LB' function is demonstrated, for the first time in the literature, for a yttria based memristor, which bears a resemblance to certain memory functions of biological systems. The realization of key synaptic functions in a cost-effective MIS structure would promote much cheaper synapse for artificial neural network.