Morphological,biochemical, and serological studies on a viral agent (CFA) which replicates in and causes fusion of Aedes albopictus (singh) cells

The cell fusing agent described earlier (Stollar and Thomas, 1975) has been studied in greater detail. By electron microscopy it is spherical, measures between 45 and 52 nm in diameter and contains a core structure between 23 and 28 nm in diameter. Viral morphogenesis can be detected by 30 hr after infection, generally in association with membranous structures and cytoplasmic vesicles. Conditions were found (low Ca²⁺ in the medium, or high cell density) which did not depress yields of CFA from infected cells but did inhibit cell fusion.The CFA contains a 40–42 S ssRNA which is infectious under appropriate conditions. In infected cells, a 40–42 S ssRNA and a 22 S dsRNA are the predominant viral RNA species.The CFA particle contains three structural polypeptides, VP-1 (MW 13,000), VP-2 (MW 16,500), and VP-3 (MW 49,000). VP-2 and VP-3 are glycosylated and are envelope-associated, whereas VP-1 is not glycosylated and is associated with the viral RNA.No antigenic cross reaction could be demonstrated between the CFA, and a variety of flavivirus (group B) antigens. The CFA appears to be an ungrouped togavirus.     

Age changes in hepatic metabolic characteristics and their modulation by dietary manipulation

Enlargement of the popliteal lymph node (PLN) of 6-week-old mice were elicited by the footpad injection of spleen cells of sex-matched, syngeneic, older mice, but not of 6-week-old mice, in a fashion of host-vs.-graft reaction. Effective stimulating cells in the inoculum seem to be Ia-bearing adherent cells. On the other hand, neither B and T cells nor immunoglobulin-secreting cells were effective for host T cell stimulation. Among nonlymphocytic adherent cells, only those attached to plastic dishes after a 24 h-incubation, enriched in macrophages, showed the stimulatory activity for the young recipients, while cells which had adhered once but detached and became non-adherent during a 24 h-incubation or a crude non-macrophage fraction did not induce the PLN response. Thus, the age-related antigenic change may occur on macrophages but not on dendritic cells. The effective cells should be alive, heat-killed cells being impotent to elicite the response. Such spleen adherent cells of aged mice were found to be also stimulative for age-matched recipients, when they are older than 3 months. Autostimulation by macrophages might be responsible, at least in part, for the age-related change of immune functions.     

M protein instability and lack of H protein processing associated with nonproductive persistent infection of HeLa cells by measles virus

Persistent infections such as subacute sclerosing panencephalitis (SSPE) which do not produce infectious virus particles (nonproductive persistence) are often accompanied by a reduced steady-state amount of the viral matrix (M) protein and/or reduced hemadsorption activity. The possible causes of these aberrations associated with nonproductive persistence were investigated by following changes in the viral proteins with time in pulse-chase experiments. Three HeLa cell lines persistently infected with measles virus; K11, K11A, and HG111; were compared to each other and to acutely infected HeLa cells. K11 produces infectious virions at a low level (productive persistence). K11A and HG111 are both nonproductive persistently infected cell lines derived from K11. K11A cells have a reduced steady-state amount of viral M protein and reduced hemadsorption activity. HG111 cells have reduced hemadsorption but a normal level of viral M protein. As such, these cell lines serve as good model systems for the study of nonproductive persistent infection associated with SSPE. The reduced amount of M protein in K11A was found to result from rapid degradation of the protein. Degradation of the protein resulted from changes in the protein itself rather than from cellular changes. The hemagglutination (H) protein was found to be present at a low level in K11A cells. In addition, in both K11A and HG111 cells, conversion of the sugar moiety of the H glycoprotein from the high mannose form to the complex sugar form did not take place. Such modification usually occurs concomitant with transport of glycoproteins onto the cell surface. As such, lack of processing could preclude the appearance of functional H proteins on the cell surface. This could account for the reduced hemadsorption activity in these cells. The roles that these changes may play in the generation of nonproductive persistence are discussed.     

Regulation of herpesvirus thymidine kinase activity in LM(TK) cells transformed by ultraviolet light-irradiated herpes simplex virus.

The content and composition of Semliki Forest virus polypeptides were not affected by a change of the host from BHK 21 cells to Aedes albopictus cells. Galactose and sialic acid were, however, lost from the viral oligosaccharides in the change; most of the cholesterol was also lost and the phospholipid composition was profoundly changed. The morphology of the virions was not changed.