Introduction to parvoviruses

Parvoviruses are amongst the smallest known viruses, with virions in the range 18-26 nm in diameter. They derive their name from the Latin parvus ( small). The family Parvoviridae has been divided into two subfamilies the Parvovirinae (vertebrate viruses) and the Densovirinae (invertebrate viruses). Some of the genera and species of the two subfamilies are shown in Table 12.1. The subfamily Parvovirinae includes the genus Dependovirus, the members of which are defective, normally replicating...

HIV virion

The virion has the general characteristics of retro-viruses described in the previous chapter but, in contrast to most retroviruses, the capsid is cone shaped (Figure 17.1), with a diameter of 40-60 nm at the wide end and about 20 nm at the narrow end. Generally, there is one capsid per virion, though virions with two or more capsids have been reported. (b) Negatively stained (c) Cryo-electron microscopy (d) Cut away view of electron cryo-tomographic visualization (d) Cut away view of electron...

Latent herpesvirus infection

When infection of a cell with a herpesvirus results in latency rather than a productive infection, multiple Figure 11.10 Formation of a concatemer. See Figure 7.5 for earlier stages of rolling circle replication of DNA. Colour coding indicates the fates of the two parental strands of DNA.

Introduction to virus vaccines

The term vaccination is derived from the Latin word vacca, meaning cow. This is because the original procedure involved the inoculation of material from cowpox lesions into healthy people. Edward Jenner tried the procedure first in 1796 after he noticed that the faces of most milkmaids were unmarked by pocks this was because milkmaids rarely contracted smallpox. They did, however, commonly contract cowpox, so Jenner inoculated material from a milkmaid's cowpox lesion into the arm of an...

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Escherichia coli cell with phage T4 attached 5 Virology Principles and Applications John B. Carter and Venetia A. Saunders 2007 John Wiley & Sons, Ltd ISBNs 978-0-470-02386-0 (HB) 978-0-470-02387-7 (PB) Viruses are parasites they depend on cells for molecular building blocks, machinery and energy. Virus particles are small dimensions range from approx. 20-400 nm. A virus genome is composed of one of the following Photographs reproduced with permission of 2Animal Sciences Group, Wageningen...

Info

1 Plaques formed by porcine reproductive and respiratory syndrome virus in a cell culture From Lee and Yoo (2005) Journal of General Virology, 86, 3091. Reproduced by permission of the Society for General Microbiology and the author. 2Plaques formed by phage MS2 in Escherichia coli cells 3 Separation of double-layered and triple-layered particles of rotavirus in a caesium chloride gradient From Lopez et al. (2005) Journal of Virology, 79, 184. Reproduced by permission of the American Society...

Mass production of viruses for vaccines

The production of the types of vaccine discussed so far (live attenuated, inactivated, subunit and live recombinant) requires large quantities of virions for most viruses these are produced in cell cultures. John Enders demonstrated in 1949 that poliovirus can be grown in primary monkey cell culture and this led to procedures for the mass production of poliovirus for the Salk and Sabin vaccines. It was subsequently found that some monkey cell cultures used for vaccine production had been...

Live recombinant virus vaccines

Recombinant Vaccine Influenza Virus

A recombinant vaccinia virus engineered to contain the gene for the rabies virus G protein has been used to vaccinate wild mammals against rabies. The use of this vaccine was discussed in Section 15.2.1. Figure 24.3 Outline of production method for influenza virus subunit vaccine. Haemagglutinin (H) and neuraminidase (N) are extracted from inactivated influenza virions and purified by sucrose gradient centrifugation. The bands from the gradient are harvested and incorporated into the vaccine.

Live attenuated virus vaccines

A live attenuated vaccine contains a mutant strain of a virus that has been derived from a wild-type virulent strain. Vaccines of this type have a number of advantages over most other types of vaccine. One advantage is that there are increasing amounts of virus antigen in the body as the virus replicates. Another is that a wide-ranging immune response is induced that involves B cells, CD4 T cells and CD8 T cells. There are two properties that the vaccine virus must possess. First, its antigens...

The nature of prions

There is no evidence that the infectious agents that cause TSEs contain any nucleic acid the agents appear to be misfolded forms of normal cell proteins. This 'protein-only' hypothesis was proposed by Stanley Figure 26.1 Brain section from a sheep with scrapie. The spongiform appearance (holes in the tissue) is evident. Magnification x 500. Courtesy of Dr. R. Higgins, University of California, Davis. Figure 26.1 Brain section from a sheep with scrapie. The spongiform appearance (holes in the...

Virion subunit vaccines

A subunit vaccine contains purified components of virions. In the case of influenza the vaccines contain the haemagglutinin (H) and neuraminidase (N) surface glycoproteins. A typical production method is outlined in Figure 24.3. The infectivity of a batch of influenza virions is inactivated with formaldehyde or P-propiolactone, then the virion envelopes are removed with a detergent, such as Triton X-100. This releases the glycoproteins, which form aggregates of H 'cartwheels' and N 'rosettes'....

New viruses 2151 SARS coronavirus

In 2002 a new human respiratory disease emerged in southern China. The following year one of the doctors who had been treating patients travelled to Hong Kong, where he became ill and died. Subsequently, people who had stayed in the same hotel as the doctor travelled to Singapore, Vietnam, Canada and the US, taking the infectious agent with them. The epidemic of severe acute respiratory syndrome (SARS) was under way. The signs and symptoms of SARS resemble those of influenza and include fever,...

Picornavirus Virion

Picornaviruses are small RNA viruses of relatively simple structure Figure 14.4 . The RNA is enclosed by a capsid, which is roughly spherical and has a diameter of about 25-30 nm. The picornavirus capsid has icosahedral symmetry and is made from 60 copies each of four virus proteins a Virion components b Electron micrograph of negatively stained virions of poliovirus Figure 14.4 The picornavirus virion. VPg virus protein, genome Linked. Electron micrograph courtesy of J. Esposito US Centers for...

Methods used in virology

Animal virus plaques in a cell culture 1 Animal virus plaques in a cell culture 1 Phage plaques in a lawn of bacterial cells 2 Phage plaques in a lawn of bacterial cells 2 Separation of virus particles in a density gradient 3 Separation of virus particles in a density gradient 3 Virus-infected cells detected using a virus-specific antibody labelled with a fluorescent dye 4 Virus-infected cells detected using a virus-specific antibody labelled with a fluorescent dye 4 An endosome labelled red...