No abstract

Simian virus 40 (SV40) can be disassembled under mild conditions by reducing disulfide bonds in the capsid and removing calcium ions. The nucleoprotein complexes formed, analyzed by electron microscopy, were circular and made up of 59 4 subunits, each with a diameter of about 10 nm. The complexes contained the viral DNA, histones, and the viral capsid proteins. The complexes had much-reduced infectivities compared with intact SV40. Addition of calcium ions to the disrupted virus caused the nucleoprotein complexes to refold into virus-like structures which sedimented at the same rate as intact SV40 and regained infectivity. Treatment of the disrupted SV40 with a high concentration of salt dissociated the viral proteins from the DNA. Lowering stepwise the salt concentration, removing the reducing agent, and adding calcium ions allowed structures to be reformed, and these structures sedimented, like SV40, at 240S and were infectious. The plaque-forming ability 2779

Characterization of the specific antimicrobial function of intravenous immunoglobulin G (i.v. IgG) preparations against particular microbial pathogens can assist in determining their therapeutic potential for specific infectious diseases. i.v. IgGs have been reported to contain antibodies directed against several viruses (24). However, the functionality of such antibodies against viral infections remains to be fully characterized.Measles virus (MV) causes an acute disease that still kills more than 1 million children in the less well developed world every year (29). The severity of measles in the young is mainly due to secondary infections (2, 9) as a result of immune suppression. The mechanism of immune suppression is due to apoptosis of infected hemopoietic cells (13) and interference with dendritic and T-cell functions (16).Measurable parameters of the immune response to MV infection include neutralization by antibody, antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent complement-mediated lysis, and cytotoxic T-lymphocyte activity (14, 15). The neutralizing antibody titer correlates well with protection from MV infection (6, 15).NK cell activity is crucial against infection by Epstein-Barr virus (EBV). Low NK cell cytotoxic activity is linked with increased human sensitivity to severe disseminating herpesvirus group infections, including those caused by herpes simplex virus (3, 7) and EBV (22,26). ADCC is thought to play a major role in controlling the spread of EBV in an infected individual.The viral membrane glycoprotein gp350/220, which is expressed at the surface of the virus-producing cell, was identified as a target for ADCC reactions (21). Sera from EBVpositive individuals provide antibodies for EBV-specific ADCC reactions (21). In individuals affected by X-linked lymphoproliferative disease, both the spontaneous NK cell cytotoxicity against EBV-infected cells and also EBV-infected cell lysis induced via CD16 are blocked (5,8,28,30,32,34). These individuals have a severe mononucleosis when they are infected with EBV. The gene modified in these patients codes for an NK cell coreceptor that is crucial for activation of cytotoxicity in NK and CD8 ϩ T cells. This demonstrates the importance that cytotoxic responses have for the control of EBV infections.i.v. IgG preparations contain significant levels of anti-MV and anti-EBV antibodies (24). However, the functionality of these antiviral antibodies has not been fully characterized. In the present work we have investigated the capacity of i.v. IgG to neutralize MV infectivity and to activate ADCC activity against an EBV-transformed cell line. The results indicate that i.v. IgG preparations contain a full capacity to neutralize MV and are also able to activate ADCC on lymphocyte preparations against the EBV-infected cell line Raji. MATERIALS AND METHODSReagents. Sorbitol (5%; pH 5 to 6) and human albumin (20%) were provided by Instituto Grifols S.A. (Parets, Spain). Dulbecco's phosphate-buffered saline (DPBS) and phosphate-buffered salin...

No abstract