REVIEW OF TRANSAMERICA DELAVAL INC. DIESEL GENERATOR OWNERS' GROUP ENGINE REQUALIFICATION PROGRAM

In December 1983, 13 nuclear utilities that own TDI diesel generators formally established an Owners• Group to address concerns regarding the reliability and operability of these engines. The Owners' Group program for engine requalification consisted of four major elements: 1) resolution of known problems with potentially generic implications, 2) a design review and quality revalidation (DR/QR) effort aimed at identifying and correcting potential problems with the important engine components, 3) expanded engine testing and inspection, and 4) enhanced engine maintenance and surveillance (M/S) to maintain the qualification of the diesel engines for the lifetime of the nuclear plants that they service. In providing technical support to NRC, the PNL project staff, assisted by a number of diesel engine consultants, focused on the four major elements of the Owners' Group engine requalification program, addressing both generic and plant-specific areas

Cell-Cell Transmission Enables HIV-1 to Evade Inhibition by Potent CD4bs Directed Antibodies

HIV is known to spread efficiently both in a cell-free state and from cell to cell, however the relative importance of the cell-cell transmission mode in natural infection has not yet been resolved. Likewise to what extent cell-cell transmission is vulnerable to inhibition by neutralizing antibodies and entry inhibitors remains to be determined. Here we report on neutralizing antibody activity during cell-cell transmission using specifically tailored experimental strategies which enable unambiguous discrimination between the two transmission routes. We demonstrate that the activity of neutralizing monoclonal antibodies (mAbs) and entry inhibitors during cell-cell transmission varies depending on their mode of action. While gp41 directed agents remain active, CD4 binding site (CD4bs) directed inhibitors, including the potent neutralizing mAb VRC01, dramatically lose potency during cell-cell transmission. This implies that CD4bs mAbs act preferentially through blocking free virus transmission, while still allowing HIV to spread through cell-cell contacts. Thus providing a plausible explanation for how HIV maintains infectivity and rapidly escapes potent and broadly active CD4bs directed antibody responses in vivo