Virus

About: Virus is a research topic. Over the lifetime, 136914 publications have been published within this topic receiving 5209107 citations. The topic is also known as: infectious agent & viruses.

B-1 and B-2 Cell–Derived Immunoglobulin M Antibodies Are Nonredundant Components of the Protective Response to Influenza Virus Infection

Abstract: We have studied the role of secreted immunoglobulin (Ig)M in protection from infection with influenza virus and delineated the relative contributions of B-1 versus B-2 cell–derived IgM in this process. Mice deficient in secreted IgM but capable of expressing surface IgM and secreting other Ig classes show significantly reduced virus clearance and survival rates compared with wild-type controls. Irradiation chimeras in which only either B-1 or B-2 cells lack the ability to secrete IgM show mortality rates similar to those of mice in which neither B-1 nor B-2 cells secrete IgM. Dependence on both sources of IgM for survival is partially explained by findings in allotype chimeras that broadly cross-reactive B-1 cell–derived natural IgM is present before infection, whereas virus strain–specific, B-2 cell–derived IgM appears only after infection. Furthermore, lack of IgM secreted from one or both sources significantly impairs the antiviral IgG response. Reconstitution of chimeras lacking B-1 cell–derived IgM only with IgM-containing serum from noninfected mice improved both survival rates and serum levels of virus-specific IgG. Thus, virus-induced IgM must be secreted in the presence of natural IgM for efficient induction of specific IgG and for immune protection, identifying B-1 and B-2 cell–derived IgM antibodies as nonredundant components of the antiviral response.

Murine Leukemia Virus: High-Frequency Activation in vitro by 5-Iododeoxyuridine and 5-Bromodeoxyuridine

Abstract: Cells of embryos of the high leukemic mouse strain AKR can be grown in culture as virus-negative cell lines However, these lines and clonal sublines uniformly have the capacity to initiate synthesis of murine leukemia virus Exposure of the cells to 5-iododeoxyuridine or 5-bromodeoxyuridine induced synthesis of virus in as high as 01 to 05 percent of the cells; many of the cells were producing virus as soon as 3 days after initiation of treatment Induction of virus by these drugs is several orders of magnitude greater than that obtained with any other treatment tested These studies indicate that the full genome of murine leukemia virus is present in an unexpressed form in all AKR cells and provide a potentially powerful technique for activating leukemia virus genomes in other cell systems

The human immunodeficiency virus-1 nef gene product: a positive factor for viral infection and replication in primary lymphocytes and macrophages.

Abstract: Considerable controversy and uncertainty have surrounded the biological function of the Human Immunodeficiency Virus (HIV)-1 nef gene product. Initial studies suggested that this early, nonstructural viral protein functioned as a negative regulatory factor; thus, it was proposed to play a role in establishing or maintaining viral latency. In contrast, studies in Simian Immunodeficiency Virus (SIV)mac-infected rhesus monkeys have suggested that Nef is not a negative factor but rather plays a central role in promoting high-level viral replication and is required for viral pathogenesis in vivo. We sought to define a tissue culture system that would approximate the in vivo setting for virus infection in order to assess the role of HIV-1 Nef in viral replication. We show that infection of mitogen-activated peripheral blood mononuclear cells (PBMC) with Nef+ HIV results in enhanced replication as evidenced by earlier gag p24 expression when compared with infections performed with nef mutant viruses. Moreover, when unstimulated freshly isolated PBMC are infected with Nef+ and Nef- viruses and then subsequently activated with mitogen, the Nef-induced difference in viral replication kinetics is even more pronounced, with the Nef- viruses requiring much more time in culture for appreciable growth. A positive effect of Nef on viral replication was also observed in primary macrophages infected with a recombinant of YU-2, a patient-derived molecular clone with macrophage tropism. These positive effects of Nef on viral replication are dependent on the initial multiplicity of infection (MOI), in that infections of unstimulated PBMC at low MOI are most dependent upon intact nef for subsequent viral growth. We now provide evidence that the Nef+ HIV is more infectious than Nef- HIV from both a tissue culture infectious dose analysis, and a single-cell HIV infection assay. In the latter case, we demonstrate that infection with equivalent doses of HIV based on virion-associated gag p24 yields five- to sixfold more infected cells if Nef+ viral stocks were used. Furthermore, we find that the differential infectivity is not dependent on CD4 down-regulation as Nef+ virus produced from transfected COS cells lacking CD4 is also more infectious. However, normalization of PBMC infections to equivalent infectivity between that of the Nef+ and Nef- viruses continues to reveal delayed viral replication in the absence of Nef, suggesting that secondary viral spread in PBMC is also enhanced in Nef+ infections. We demonstrate this directly by showing a 13-15-fold increase in infectivity of PBMC-derived Nef+ HIC.(ABSTRACT TRUNCATED AT 400 WORDS)

Induction of AIDS in rhesus monkeys by molecularly cloned simian immunodeficiency virus

Abstract: Better understanding of the pathogenesis of acquired immunodeficiency syndrome (AIDS) would be greatly facilitated by a relevant animal model that uses molecularly cloned virus of defined sequence to induce the disease. Such a system would also be of great value for AIDS vaccine research. An infectious molecular clone of simian immunodeficiency virus (SIV) was identified that induces AIDS in common rhesus monkeys in a time frame suitable for laboratory investigation. These results provide another strong link in the chain of evidence for the viral etiology of AIDS. More importantly, they define a system for molecular dissection of the determinants of AIDS pathogenesis.

Epidemiological evidence for causal relationship between Epstein-Barr virus and Burkitt's lymphoma from Ugandan prospective study

Abstract: Results from a prospective sero-epidemiological study initiated in Uganda in 1971 indicate that children with high antibody titres to Epstein-Barr virus structural antigens are at high risk of developing Burkitt's lymphoma. These findings strongly support a causal relationship between the Epstein-Barr virus and Burkitt's lymphoma but suggest that the oncogenic potential of the virus is realised only in exceptional circumstances.