The plaque assay is an essential tool for determining virus titers. The concept is simple: virus infection is restricted to neighboring cells by a semisolid overlay. By counting the number of plaques, the virus titer can be calculated in PFU per ml. A key question is: how many viruses are needed to form a single …
One of the most important procedures in virology is measuring the virus titer – the concentration of viruses in a sample. A widely used approach for determining the quantity of infectious virus is the plaque assay. This technique was first developed to calculate the titers of bacteriophage stocks. Renato Dulbecco modified this procedure in 1952 …
The immune response to viral infection comprises innate and adaptive defenses. The innate response, which we have discussed previously, functions continuously in a normal host without exposure to any virus. Most viral infections are controlled by the innate immune system. However, if viral replication outpaces innate defenses, the adaptive response must be mobilized. The adaptive …
During the earliest stages of a virus infection, cytokines are produced when innate immune defenses are activated. The rapid release of cytokines at the site of infection initiates new responses with far-reaching consequences that include inflammation. One of the earliest cytokines produced is tumor necrosis factor alpha (TNF-α), which is synthesized by activated monocytes and …
Mutation is an important source of RNA virus diversity that is made possible by the error-prone nature of RNA synthesis. Viruses with segmented genomes, such as influenza virus, have another mechanism for generating diversity: reassortment. When an influenza virus infects a cell, the individual RNA segments enter the nucleus. There they are copied many times …
The RNA genome of influenza viruses is segmented . The virions of influenza A and B viruses contain 8 different RNAs, while those of influenza C viruses contain 7. How is the correct number of RNA segments inserted into newly synthesized virus particles? During influenza virus assembly, viral RNAs and viral proteins €“ called a …
