AN ENZYMATIC FUNCTION ASSOCIATED WITH TRANSFORMATION OF FIBROBLASTS BY ONCOGENIC VIRUSES : I. CHICK EMBRYO FIBROBLAST CULTURES TRANSFORMED BY AVIAN RNA TUMOR VIRUSES

Chick embryo fibroblast cultures develop fibrinolytic activity after transformation by Rous sarcoma virus (RSV). This fibrinolytic activity is not present in normal cultures, and it does not appear after infection with either nontransforming strains of avian leukosis viruses or cytocidal RNA and DNA viruses. In cultures infected with a temperature sensitive mutant of RSV the onset of fibrinolysis appears after exposure to permissive temperatures and precedes by a short interval the appearance of morphological evidence of transformation. See PDF for Structure The rate of fibrinolysis in transformed cultures depends on the nature of the serum that is present in the growth medium: some sera (e.g., monkey or chicken serum) promote high enzymatic activity, while others (calf, fetal bovine) do not. Some sera contain inhibitors of the fibrinolysin. Based on the effect of a small number of known inhibitors, at least one step of the fibrinolytic process shows specificity resembling that of trypsin. The sera of sarcoma-bearing chickens contain an inhibitor of the fibrinolysin, whereas normal chicken sera do not. For general discussion, conclusions, and summary see the accompanying paper, part II, (J. Exp. Med. 137:112)

Trypanosoma cruzi. Surface antigens of blood and culture forms.

Recent studies from this laboratory have shown a striking difference in the ability of mouse macrophages to ingest blood-form trypomastigotes (BFT) 1 of the Y and CL strains of T~ypanosoma cruzi, as compared with metacyclic trypomastigotes grown in culture. This was the result of an anti-phagocytic factor, present on the surface of BFT, that could be either removed by trypsinization or nullified with specific hyperimmune serum. Such treatments were without influence on their intracellular fate when ingested by resident or inflammatory macrophages. However, when taken up by lymphokine-activated macrophages, BFT were readily destroyed, as were the metacyclic trypomastigotes (1). The presence of this antiphagocytic material lead us to investigate the surface components of both culture-form trypomastigotes and BFT. In this article, we report that BFT possess a major 90,000-relative molecular weight (Mr) surface membrane glycoprotein of isoelectric point (pI) 5.0, which is readily cleaved by trypsin and is precipitated by both human and murine immune sera. This component is absent from metacyclic trypomastigotes and epimastigotes from aeellular cultures and may be responsible for the anti-phagocytic effect

Intranasal Immunization with an Archaeal Lipid Mucosal Vaccine Adjuvant and Delivery Formulation Protects against a Respiratory Pathogen Challenge

Archaeal lipid mucosal vaccine adjuvant and delivery (AMVAD) is a safe mucosal adjuvant that elicits long lasting and memory boostable mucosal and systemic immune responses to model antigens such as ovalbumin. In this study, we evaluated the potential of the AMVAD system for eliciting protective immunity against mucosal bacterial infections, using a mouse model of intranasal Francisella tularensis LVS (LVS) challenge. Intranasal immunization of mice with cell free extract of LVS (LVSCE) adjuvanted with the AMVAD system (LVSCE/AMVAD) induced F. tularensis-specific antibody responses in sera and bronchoalveolar lavage fluids, as well as antigen-specific splenocyte proliferation and IL-17 production. More importantly, the AMVAD vaccine partially protected the mice against a lethal intranasal challenge with LVS. Compared to LVSCE immunized and naïve mice, the LVSCE/AMVAD immunized mice showed substantial to significant reduction in pathogen burdens in the lungs and spleens, reduced serum and pulmonary levels of proinflammatory cytokines/chemokines, and longer mean time to death as well as significantly higher survival rates (p<0.05). These results suggest that the AMVAD system is a promising mucosal adjuvant and vaccine delivery technology, and should be explored further for its applications in combating mucosal infectious diseases

Markedly Different Pathogenicity of Four Immunoglobulin G Isotype-Switch Variants of an Antierythrocyte Autoantibody Is Based on Their Capacity to Interact in Vivo with the Low-Affinity Fcγ Receptor III

Using three different Fcγ receptor (FcγR)-deficient mouse strains, we examined the induction of autoimmune hemolytic anemia by each of the four immunoglobulin (Ig)G isotype-switch variants of a 4C8 IgM antierythrocyte autoantibody and its relation to the contributions of the two FcγR, FcγRI, and FcγRIII, operative in the phagocytosis of opsonized particles. We found that the four IgG isotypes of this antibody displayed striking differences in pathogenicity, which were related to their respective capacity to interact in vivo with the two phagocytic FcγRs, defined as follows: IgG2a > IgG2b > IgG3/IgG1 for FcγRI, and IgG2a > IgG1 > IgG2b > IgG3 for FcγRIII. Accordingly, the IgG2a autoantibody exhibited the highest pathogenicity, ∼20–100-fold more potent than its IgG1 and IgG2b variants, respectively, while the IgG3 variant, which displays little interaction with these FcγRs, was not pathogenic at all. An unexpected critical role of the low-affinity FcγRIII was revealed by the use of two different IgG2a anti–red blood cell autoantibodies, which displayed a striking preferential utilization of FcγRIII, compared with the high-affinity FcγRI. This demonstration of the respective roles in vivo of four different IgG isotypes, and of two phagocytic FcγRs, in autoimmune hemolytic anemia highlights the major importance of the regulation of IgG isotype responses in autoantibody-mediated pathology and humoral immunity

Endothelial Cells Support Persistent Gammaherpesvirus 68 Infection

A variety of human diseases are associated with gammaherpesviruses, including neoplasms of lymphocytes (e.g. Burkitt's lymphoma) and endothelial cells (e.g. Kaposi's sarcoma). Gammaherpesvirus infections usually result in either a productive lytic infection, characterized by expression of all viral genes and rapid cell lysis, or latent infection, characterized by limited viral gene expression and no cell lysis. Here, we report characterization of endothelial cell infection with murine gammaherpesvirus 68 (γHV68), a virus phylogenetically related and biologically similar to the human gammaherpesviruses. Endothelial cells supported γHV68 replication in vitro, but were unique in that a significant proportion of the cells escaped lysis, proliferated, and remained viable in culture for an extended time. Upon infection, endothelial cells became non-adherent and altered in size, complexity, and cell-surface protein expression. These cells were uniformly infected and expressed the lytic transcription program based on detection of abundant viral gene transcripts, GFP fluorescence from the viral genome, and viral surface protein expression. Additionally, endothelial cells continued to produce new infectious virions as late as 30 days post-infection. The outcome of this long-term infection was promoted by the γHV68 v-cyclin, because in the absence of the v-cyclin, viability was significantly reduced following infection. Importantly, infected primary endothelial cells also demonstrated increased viability relative to infected primary fibroblasts, and this increased viability was dependent on the v-cyclin. Finally, we provide evidence for infection of endothelial cells in vivo in immune-deficient mice. The extended viability and virus production of infected endothelial cells indicated that endothelial cells provided a source of prolonged virus production and identify a cell-type specific adaptation of gammaherpesvirus replication. While infected endothelial cells would likely be cleared in a healthy individual, persistently infected endothelial cells could provide a source of continued virus replication in immune-compromised individuals, a context in which gammaherpesvirus-associated pathology frequently occurs