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.

Detection of herpesvirus-like DNA sequences in Kaposi's sarcoma in patients with and those without HIV infection.

Abstract: Background Herpesvirus-like DNA sequences have recently been found in lesions from patients with Kaposi's sarcoma and the acquired immunodeficiency syndrome (AIDS). It is not known whether these sequences are also present in classic Kaposi's sarcoma or in the Kaposi's sarcoma that occurs in homosexual men who are seronegative for the human immunodeficiency virus (HIV). Methods We analyzed DNA in tissue samples from patients with AIDS-associated Kaposi's sarcoma, patients with classic Kaposi's sarcoma, and HIV-seronegative homosexual men with Kaposi's sarcoma. We also analyzed DNA in samples of uninvolved tissue from these patients and in control tissue from healthy subjects. All samples were tested blindly by polymerase chain reaction (PCR) with specific primers to amplify KS330233, a herpesvirus-like DNA sequence. Results The KS330233 PCR product was found in 20 of 21 tissue samples (95 percent) from the patients with Kaposi's sarcoma, including 10 of the 11 samples from the patients with AIDS-associated...

Papillomavirus L1 major capsid protein self-assembles into virus-like particles that are highly immunogenic.

Abstract: Infection by certain human papillomavirus types is regarded as the major risk factor in the development of cervical cancer, one of the most common cancers of women worldwide. Analysis of the immunogenic and structural features of papillomavirus virions has been hampered by the inability to efficiently propagate the viruses in cultured cells. For instance, it has not been established whether the major capsid protein L1 alone is sufficient for virus particle assembly. In addition, it is not known whether L1, L2 (the minor capsid protein), or both present the immunodominant epitopes required for induction of high-titer neutralizing antibodies. We have expressed the L1 major capsid proteins of bovine papillomavirus type 1 and human papillomavirus type 16 in insect cells via a baculovirus vector and analyzed their conformation and immunogenicity. The L1 proteins were expressed at high levels and assembled into structures that closely resembled papillomavirus virions. The self-assembled bovine papillomavirus L1, in contrast to L1 extracted from recombinant bacteria or denatured virions, also mimicked intact bovine papillomavirus virions in being able to induce high-titer neutralizing rabbit antisera. These results indicate that L1 protein has the intrinsic capacity to assemble into empty capsid-like structures whose immunogenicity is similar to infectious virions. This type of L1 preparation might be considered as a candidate for a serological test to measure antibodies to conformational virion epitopes and for a vaccine to prevent papillomavirus infection.

Norwalk Virus: How Infectious Is It?

Abstract: Noroviruses are major agents of viral gastroenteritis worldwide. The infectivity of Norwalk virus, the prototype norovirus, has been studied in susceptible human volunteers. A new variant of the hit theory model of microbial infection was developed to estimate the variation in Norwalk virus infectivity, as well as the degree of virus aggregation, consistent with independent (electron microscopic) observations. Explicit modeling of viral aggregation allows us to express virus infectivity per single infectious unit (particle). Comparison of a primary and a secondary inoculum showed that passage through a human host does not change Norwalk virus infectivity. We estimate the average probability of infection for a single Norwalk virus particle to be close to 0.5, exceeding that reported for any other virus studied to date. Infected subjects had a dose-dependent probability of becoming ill, ranging from 0.1 (at a dose of 10(3) NV genomes) to 0.7 (at 10(8) virus genomes). A norovirus dose response model is important for understanding its transmission and essential for development of a quantitative risk model. Norwalk virus is a valuable model system to study virulence because genetic factors are known for both complete and partial protection; the latter can be quantitatively described as heterogeneity in dose response models.

Production of hepatitis B virus particles in Hep G2 cells transfected with cloned hepatitis B virus DNA.

Abstract: The hepatoblastoma cell line Hep G2 was transfected with a plasmid carrying the gene that confers resistance to G418 and four 5'-3' tandem copies of the hepatitis B virus (HBV) genome positioned such that two dimers of the genomic DNA are 3'-3' with respect to one another. Cells of one clone that grew in the presence of G418 produce high levels of hepatitis B e antigen and of hepatitis B surface antigen. HBV DNA is carried by these cells as chromosomally integrated sequences and episomally as relaxed circular, covalently closed, and incomplete copies of the HBV genome. Viral DNA was detected also in conditioned growth medium at the buoyant densities characteristic for infectious Dane and immature core particles. Finally, HBV-specific components morphologically identical to the 22-nm spherical and filamentous hepatitis B surface antigen particles as well as 42-nm Dane particles were visualized by immunoelectron microscopic analysis. Therefore, we have demonstrated that the Hep G2 cell line can support the assembly and secretion not only of several of the replicative intermediates of HBV DNA but also of Dane-like particles. This in vitro system can now be used to study the life cycle of HBV and the reaction of immunocompetent cells with cells carrying HBV.