Vaccination

During the 1930s attenuated rinderpest vaccines were developed by passage of the virus in nonnatural hosts, e.g. rabbit and embryonated eggs (lapinized avian-ized) or goats (caprinized). The Japanese lapinized avianized vaccine was used extensively to control the disease in Asia. In India and Africa the caprinized virus was used however, this virus was not completely attenuated and it may have been responsible for the circulation of rinderpest in small ruminants in India. In the early 1960s the...

Two Main Requirements of a Vaccine

The safety of a candidate vaccine has become of prime importance. Most of the vaccines listed in Table 1 are very safe, but two in particular are less so. During the eradication campaign, most smallpox vaccines (vaccinia virus) had a level of side effects which made them unacceptable for current use. Safer preparations have since been made by the deletion of specific DNA sequences. Type 3 poliovirus in OPV can revert to virulence, and poliomyelitis occurs at the rate of about 3 X 106 doses of...

Future Perspectives

The use of recombinant DNA technology can be expected to lead to the production of safer, more effective vaccines, as they can be more readily tailor-made to requirements and subsequently modified as required. Genetic engineering also offers the opportunity to construct multivalent vaccines in which the genes for several different antigens can be inserted into the same vector. In addition to the present recombinant vaccines available, which consist of the NDV HN or F gene sequences inserted...

Pathology and Histopathology

The most frequently and consistently observed microscopic lesions in fatal human Lassa fever are focal necrosis of the liver, adrenal glands and spleen. The liver damage is variable in the degree of hepatocytic necrosis. The liver demonstrates cellular injury, necrosis, and regeneration, with any or all present at death. A substantial macrophage response occurs, with little if any lymphocytic inflammatory response. Nevertheless, fatal cases do not exhibit sufficient hepatic damage to implicate...

Genital Cancer

Clinical studies, and especially data from molecular biology, suggest that certain types of human papillomavirus (HPV) are of etiological importance for genital cancer. In developing countries, carcinoma of the cervix uteri is the most frequent type of female cancer. HPV DNA can be found in 80-90 of the tumors, and the early genes E6 and E7 are usually expressed. The most prevalent type in epidermoid carcinomas is HPV 16. HPV 18 may be preferentially associated with adenocarcinomas. Other types...

Virus Transmission

BYV, the type species of the Closterovirus genus, has aphid vectors. However, other types of vectors (mealybugs, whiteflies) have been reported for members of the same genus. In many cases, the mode of transmission or the vector has not been determined (Table 1). Studies have mostly dealt with aphid transmission of BYV and CTV. Information on the transmission of other viruses is still very limited and, in many instances, transmission has only been demonstrated under laboratory conditions. In...

Virus Structure

The tobravirus genome is composed of two single-stranded RNA molecules of positive polarity, which are capped at the 5' termini and which fold into a tRNA-like tertiary structure at the 3' termini. However, this tRNA-like structure cannot be amino-acylated, as is the case in other viruses showing such a structure at the 3' terminus. The RNAs, designated RNA1 and RNA2, are separately encapsidated by coat protein subunits. The structure of the virions is determined by a helical array of coat...

Properties of the Virion

VSV particles are rod-shaped (hence the name rhabdo, from the Greek for rod) enveloped viruses of approximate dimensions 70 X 180 nm (Fig. 1). The virion core consists of a helical ribonucleoprotein (RNP) structure containing the RNA genome. The protein components of RNP cores consist of nucleo-capsid (N) protein, the polymerase-associated phos-phoprotein (P) and the large (L) polymerase protein. Based on studies using electron microscopy it has been estimated that there are 1258,466 and 50...

Lysogeny

Like other temperate phages, P22 can follow either of two pathways following infection of a sensitive host cell it can grow lyrically, or form a lysogen. Which of these pathways is favored depends on a variety of factors, including the multiplicity of infection and the nutritional status of the cell. The key element in the choice between pathways is a transcriptional regulatory protein, the product of gene cl, which is transcribed as a result of antitermination by gene 24 protein. Regulation of...

Introduction

Most viral infections of the nervous system represent serious and potentially life-threatening complications of systemic viral infections. With the possible exception of rabies, viruses are not neurotropic in the literal sense of having a specific affinity for the nervous system. Some viruses frequently invade the nervous system yet seldom cause serious disease for example, mumps virus may cause meningitis but even during uncomplicated mumps parotitis cerebrospinal fluid changes in over 50 of...

History

The nonoccluded baculoviruses (NOB) are a loosely associated group of enveloped, rod-shaped viruses which, in many respects resemble the occluded baculoviruses except that they are not found associated with a protein crystal occlusion body. Only three NOBs have been studied to any significant extent. The first NOB to be identified was the Oryctes virus (Or-lV). The isolation of this virus resulted from a field study conducted throughout Southeast Asia in 1963, to find an agent that could be...

Papillomaviruses HPV

Infections with HPV types are ubiquitous, with over 80 types that cause a variety of wart-associated conditions. While most lesions are benign, some, especially those caused by HPV-16, -18 and other oncogenic HPV types, may progress to premalignant and malignant lesions. Papillomaviruses are causally associated with cervical cancer, which is diagnosed in 15 000 American women annually and causes approximately 4500 deaths. Types 6 and 11 are responsible for common genital infections and also for...

Prevention and Control of Cardiovirus Infections

Given that the introduction of cardioviruses to domestic swine, zoo populations or captive primate colonies can constitute a considerable veterinary and economic problem, it would be desirable to have efficacious cardiovirus vaccines available to prevent epidemics. In 1989, Duke and Palmenberg prepared several Mengo cDNAs in order to determine the nucleotide sequence of the genome. Their enzymatic procedures accidentally truncated the poly(C) tracts in the 5' UTRs of several cDNAs (e.g. C UCxo...

Herpesviruses

The herpes viruses, Cytomegalovirus, Epstein Barr virus, herpes simplex and varicella zoster represent the greatest potential threat to transplant recipients. All four are present in the latent state in a high proportion of individuals, and all four can cause serious or fatal disease in the immunocompromised host. Background In a normal individual, defense against CMV is mediated by specific cytotoxic T lymphocytes, by production of specific antibody and perhaps also by MHC unrestricted...

Host Range and Virus Propagation

Rabies virus infects a very broad array of animal species, perhaps the widest range of any animal virus. Commonly infected are dogs, wolves, foxes, jackals, skunks, raccoons, raccoon dogs, vampire bats, insectivorous bats and mongooses the animals bitten by these species develop sporadic cases of rabies (these include cats, cows, horses, badgers and woodchucks) although the virus in those species rarely becomes enzootic. Humans are mostly infected after bites by rabid dogs. Propagation is...

Hepatitis Viruses

Hepatitis, or inflammation of the liver, can be caused by many different viruses and chemical substances. Viruses may cause acute infection (hepatitis A virus) or acute infection with the possibility for chronic liver infection leading to cirrhosis and hepatocellular carcinoma. Two major causative agents of acute and chronic disease are hepatitis B (HBV) and hepatitis C (HCV) viruses. The World Health Organization estimates the worldwide population of HBV carriers at about 350 million, with 75...

Industries Affected by Phage Infection

Reliable data on the severity of phage infection of industrial fermentations are difficult to obtain. This is primarily because release of this information raises confidentiality concerns of private industry. Therefore, inference must be made from publications citing incidences (although not degrees) of phage infection or reporting developments to cope with phage problems. Such information suggests that phage problems are pervasive, although assignment of an accurate monetary value on lost or...

DNV Disease and Ecology

There have been a number of reports of DNV diseases of economically important insects in Japan and the Peoples' Republic of China. A disease of the silkworm B. mori in the vicinity of Ina City, Japan, in 1968 has led to the discovery of B wDNV. At least two other isolates of DNV from diseased silkworms were later discovered in Japan and in China. Epizootic spread of DNV was observed in Japan in silkworm sericulture farms and in mulberry pyralids in mulberry plantations. The virus isolated from...

Transmission

Cats persistently infected with FeLV shed virus in their saliva, urine and feces but, as the virus is fragile, close contact is required for transmission. The most frequent routes involve saliva and transplacental spread. Kittens infected in utero become persistently infected, but the consequences of infection in older cats depend on a number of factors. There is an age-related resistance to infection such that cats up to 12 weeks of age are highly susceptible but above 16 weeks they are...

Prevention and Control of Pseudorabies

The strategy selected to control PR has depended on (1) the type of operation carried out by the producer (farrow-to-finish, seedstock, feeder pig producer, feeder pig finisher) (2) financial considerations (3) availability of suitable replacements (4) the disease profile of the herd and (5) PRV status in the area. Slaughter of an entire herd and repopulation is considered with single isolated outbreaks in non-infected districts, but may also be necessary when disease is detected in seed stock...

Cyclic Variations of Defective Interference

The dependence of DI genome replication on functions provided by the nondefective genome on the one hand, and the interference exhibited by DI genome on the other hand, result in out-of-phase cyclic variations of both DI and St genome replication. As illustrated in Fig. 2, efficient St genome replication must precede extensive DI genome replication. This in turn establishes conditions of high interference which results in 1. High St genome replication high helper function 3. Low St genome...

Virus Particles

RTBV has bacilliform particles of 30 nm diameter and usually about 130 nm length (Fig. 2). However, in some isolates longer particles in excess of 300 nm are found. The structure of the particles is based on a T 3 icosahedron cut across its threefold axis with the tubular portion being made up of rings of hexamer subunits and a repeat distance of about 10 nm. The particles have an S2ow of approximately 200 and a buoyant density in cesium chloride of approximately 1.36 g ml-1. Figure 2 Electron...

DNA Viruses

Comprising a subfamily of the Parvoviridae, the Densovirinae contains members (DNVs) that are invertebrate-specific viruses, and that have a single-stranded linear DNA genome. Densonucleosis viruses (DNVs) have been shown to cause lethal infections in hosts from the orders Lepidoptera, Diptera and Orthoptera (locusts and crickets). The virions are relatively stable in the environment, but are apparently highly susceptible to ultraviolet (UV) light. Horizontal transmission is either via...

Properties of the Genome

All members of the Hepadnaviridae family have a partially double-stranded DNA genome of about 3 kb that is held in a circular conformation by a short cohesive overlap between the 5' ends of the two DNA strands (Fig. 1). One strand is always complete in virus particles, whereas the second strand is incomplete, with a 3' end that is heterogeneous in location. The incomplete strand is of plus polarity and the complete strand of negative polarity. When these viruses infect a cell, the plus strand...

Genetics

MMTV causes mammary adenocarcinomas by infection of the mammary epithelium with either exogenous or endogenous virus. The genetic factors that influence mammary tumor incidence in mice include B and T cells are infected in small intestine Virally-encodod superamigen expands infected B and T cells B and T cells are infected in small intestine Virally-encodod superamigen expands infected B and T cells (1) the presence or absence of milk-borne virus, (2) the presence of an infectious endogenous...

Perpetuation of Viruses in Nature

Perpetuation of a virus in nature depends on the maintenance of serial infections, i.e. a chain of transmission the occurrence of disease is neither required nor necessarily advantageous. Influence of the clinical status of the host Infection without recognizable disease is called subclinical or clinically inapparent. Overall, subclinical infections are much more common than those that result in disease. Their relative frequency accounts for the difficulty of tracing chains of transmission,...

Viruses of Euryarchaeota Halophages

All of the halophages isolated to date are head and tail phages similar to various coliphages (e.g. T phages and A relatives). Halophages have isometric, icosa-hedral heads of widely differing sizes and tails, which in the case of OH, Hsl, HF1, HF2 and OChl are contractile. In the phages OH and ON tail fibers have been described, in the phages Hh3 and OChl collars. The DNA of halophages is double-stranded and varies between 30 and 60 kb in size, with the exception of Jal which carries an...

Ocular Disease Caused by DNA Viruses

DNA viruses (Table 2) are responsible for most significant ocular viral infections in the industrialized world. Even the protean ocular manifestations of the HIV, an RNA virus, result largely from reduced immunity to DNA viruses. Adenovirus is probably the most common DNA virus to cause eye disease. Three common ocular syndromes have been identified. Simple follicular conjunctivitis occurs with infection by many adenovirus types and may be subclinical. Pharyngoconjunc-tival fever typically...

Info

Figure 3 Heliothis armigera (cotton bollworm) cadaver after infection by HaNPV. Figure 3 Heliothis armigera (cotton bollworm) cadaver after infection by HaNPV. suited of the insect viruses for development as commercial pest control agents. Past and current uses of baculoviruses Baculo-viruses have been used for many years as pest control agents, being exploited both commercially (Table 2) and noncommercially. Early reports of use include the Chinese army using mortars to fire infected larvae...

Epidemiology

There have been at least three panzootics. The first began in 1926 and spread to most countries before it eventually subsided in the late 1950s as the result of widespread vaccination. The second panzootic emerged in the late 1960s in the Middle East and spread rapidly to all continents and most countries by 1973. The third panzootic appears to have emerged in the late 1970s in the Middle East and is thought to have been spread across Europe and then to many other countries by racing pigeons,...

Virus Titration

There is a variety of ways to determine the amount of virus in a preparation. Two types of methods should be distinguished (1) infectivity assays that measure the amount of infectious virions in a preparation and (2) particle assays that determine the number of all virus particles. For lytic viruses, the most commonly used infectivity assay is the plaque assay. Monolayers of highly permissive cells are infected with serial dilutions of the virus suspension to be tested. After infection, the...

Virion Proteins and RNA Segments

The spherical Bunyaviridae virion consists of four structural proteins two internal proteins (N and L) and two (perhaps three in some nairoviruses) external glycoproteins which are inserted in the viral membrane (Fig. 1). By convention, the glycoprotein of greater molecular weight (or slower electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gels) is termed Gl. There is no equivalent of a matrix protein to stabilize the virion structure. The three genomic RNA segments, which are...

Viruses Affecting the Heart

Viruses may affect the heart in a number of different ways. Developmental defects may occur as a result of intrauterine infection by such viruses as rubella, and infection of the myocardium may be induced by a large number of viruses in different groups, although infection by enteroviruses probably represents the commonest cause of acute and chronic heart muscle disease. As yet, there is little evidence to support the role of viruses as a cause of endocardial disease. Although the myocardium is...

Geographic Distribution

Peste Des Petits Ruminants Distribution

Rinderpest is enzootic on the Indian subcontinent and in parts of the Middle East and Eastern Africa. Sporadic outbreaks occur in countries bordering the enzootic regions. Peste des petits ruminants is enzootic in parts of West Africa but in the past few years it has spread across a broad belt of sub-Saharan Africa and eastwards through the Middle East and to southern Asia as far as Bangladesh (Fig. 1). It was thought until recently that India was free from peste des petits ruminants virus and...

Dhfr

A From inserted ORSV coat protein promoter. a From inserted ORSV coat protein promoter. The viral coat protein gene can, in some instances, be manipulated in order to express foreign sequences, though it always leads to lower fitness in terms of systemic spread. Although for some viruses the coat protein is dispensable for cell-to-cell movement (e.g. TMV), this structural protein cannot be omitted for long-distance transport of the inoculated vector (via the vascular system) throughout the...

Prevention and Control

The control of domestic Ae. aegypti mosquitoes is an important measure, but has proven difficult to sustain. The most effective approach to prevention is immunization of the human population in endemic areas. Yellow fever 17D is a live, attenuated vaccine produced in embryonated eggs. Over 300 million people have been immunized with this inexpensive product, which has proven safe and highly effective. Recent efforts have focused on the production of a new vaccine derived from a full-length cDNA...

Peach latent mosaic viroid

Figure 1 Secondary structures of potato spindle tuber and peach latent mosaic viroids. (A) A rod-like secondary structure for PSTVd is supported by a variety of physical studies as well as chemical and enzymatic mapping data. Boundaries of the terminal-left (Tl), pathogenicity, central conserved, variable and terminal-right (TR) domains are indicated by vertical lines. (B) Proposed lowest-free-energy structure of PLMVd. Predicted self-cleavage sites in the plus and minus strands are indicated...

Viruses that Promote Apoptosis DNA viruses

Adenoviridae Adenoviruses encode proteins that promote apoptosis at later stages in the productive cycle. These are encoded in the E3 and E4 regions. The E3 11.6K, Ad death protein (ADP) is expressed at high levels late in infection and may bring on apoptosis, but this has not been demonstrated. It is required at very late stages for efficient cell lysis and virus release. African swine fever virus Monocytes, macrophages and mononuclear cells infected with AFSV undergo apoptosis. This gives...

Transmission and Pathogenicity

Horizontal transmission of MBV is thought to occur through hyphal anastomosis between noninfected mycelium and infected mycelium and basidiospore germlings. MBV can infect A. bisporus singly, but is more commonly found as a double infection with La France isometric virus (LIV), a dsRNA genome virus implicated in the etiology of La France disease. MBV is not required in pathogenesis involving LIV, but it remains to be determined if it is a minor cause of La France disease, the causative agent of...

Enterovirus type 70 EV70 History

EV70 is the second human enterovirus isolated from extensive epidemics where the dominant clinical manifestations are in the eye, the first being coxsackievirus A24 variant CA24v . Together these viruses are universally recognized as causative agents of acute hemorrhagic conjunctivitis AHC . EV70 was first isolated in 1971 during the 1969-1971 wave of AHC in Morocco, Singapore, Hong Kong concurrently with CA24v and Japan. Explosive outbreaks of acute conjunctivitis, thought intitially to be due...

Pyrogenic Exotoxins of Streptococcus Pyogenes and Staphylococcus Aureus

The streptococcal pyrogenic exotoxins also known as erythrogenic toxins or scarlatinal toxins are produced by S. pyogenes and cause the rash of scarlet fever. The enterotoxins of S. aureus cause the symptoms of staphylococcal food poisoning, and toxic shock syndrome toxin of S. aureus is responsible for many manifestations of toxic shock syndrome. These toxins share antigenic properties, amino acid sequences, and biological activities including pyro-genicity, enhancement of sensitivity to...

Virus Capsid Threedimensional Structure

Fmd Virus Structure

X-ray crystallographic analysis of the Mengo virion at 0.3 nm resolution was reported in 1987 by Luo et al. The overall architecture of the capsid follows T 1 icosahedral symmetry, with one asymmetric unit comprising one molecule each of VP1, VP2 and VP3. The 60 VP4 molecules occupy internal positions, extending from under the threefold axes to form part of an annular structure under the fivefold axes there Table 1 Physicochemical properties of the cardiovirion Table 1 Physicochemical...

Genetics and Evolution

The entire genome sequence of several parainfluenza viruses is known Table 1 . Although the gene organization is very similar in these viruses, divergence of individual protein sequence is variable. P protein is the most variable. Interestingly, the V protein encoded in the same gene is relatively conserved at the C-terminus. NP and M are relatively less variable. L protein has four to five regions of significant amino acid conservation. These regions are believed to be important for a number...

The Reovirus Particle

Reovirus particles consist of a core some 55 nm in diameter which is surrounded by an outer capsid shell that is about 12.5 nm thick Fig. 1 . Since the thickness of the core shell is about 7.5 nm, the central cavity accounts for about 12.5 of the reovirus particle volume, and the core for about 33 . Both the outer capsid and the core shell are composed of capsomers which are arranged with icosa-hedral symmetry. The reovirus particle surface reveals 600 protrusions, presumably capsomers,...

Dfk

Ccmv Virus Symmetry

Nudaurella co capensls virus Ncov - r 4 cowpea chlorotic mottle virus CCMV - 7 3 southern bean mosaic virus SBMV - 7 3 Figure 2 Structure of A vertebrate, B insect and C plant virus protein subunits that assemble into icosahedral shells. The name of the virus appears below the corresponding protein subunit along with the capsid triangulation number T explained in Fig. 3 . The N- and C-termini are labeled with the residue numbers in brackets. Many virus subunit structures determined to near...

History and General Characteristics

Isolation and characterization of bee viruses began in the 1960s, with work on two diseases, sacbrood and paralysis, which have striking symptoms. Sacbrood, although extremely common in Britain, was, until the virus was isolated, dismissed there as a genetic disorder. Similarly, paralysis was ascribed to independent, but accompanying and very common, well-known parasites, especially microsporidia and mites, which do not cause any overt symptoms. Many, if not all, of the viruses of bees persist...

Viruses Occurring in Europe

Tahyna TAH virus is widely distributed in Europe, and has been reported in Africa. TAH virus produces an influenza-like febrile disease, with occasional central nervous system involvement. The virus is a bunyavirus of the California serogroup, in the Bunyaviridae. Like La Crosse virus, small forest mammals are TAH virus reservoirs, and the virus is horizontally and transovarially transmitted by Aedes mosquitoes. There are no effective control measures. Omsk hemorrhagic fever occurs in a...

Viruses Occurring in Australia

Murray Valley encephalitis MVE occurs primarily in southeastern Australia, with cases appearing occasionally in other parts of the country and in Papua New Guinea. Febrile disease leads to encephalitis and, in severe cases, death. Neurologic sequelae are common in survivors. Children are predominantly affected. Large water birds are the main vertebrate amplifying hosts, but mammals are also reservoirs. The virus is transmitted mainly by Culex annuliros-tris mosquitoes. It is maintained in...