Parvovirus
Encyclopedia
Parvovirus, often truncated to "parvo", is both the common name in English casually applied to all the viruses in the Parvoviridae
taxonomic family, and also the taxonomic name of the Parvovirus genus
within the Parvoviridae
family. This creates a confusion of terms, because parvoviruses which causes human and animal diseases are not in genus Parvovirus though they are casually called parvoviruses just as lions and tigers are sometimes called "cats," being also felids. Parvoviruses are typically linear, non-segmented single-stranded DNA virus
es, with an average genome size of 5000 nucleotides. Parvoviruses are some of the smallest viruses (hence the name, from Latin
parvus meaning small) and are 18–26 nm in diameter.
Many types of mammalian species
have a strain of parvovirus associated with them. Parvoviruses tend to be specific about the taxon
of animal they will infect, but this is a somewhat flexible characteristic. Thus, all strains of canine parvovirus
will affect dog
s, wolves, and fox
es, but only some of them will infect cat
s.
No members of the genus Parvovirus are currently known to infect humans, but humans can be infected by viruses within three other genera from the family Parvoviridae, including the one popularly known by the common name Parvovirus B19
. These are the Dependovirus
es (e.g. Adeno-Associated Virus
), the Erythroviruses (e.g. Parvovirus B19
) and the Bocaviruses
.
structure that is resistant to acid
s, base
s, solvents and temperature up to 50°C.
Inside the capsid is a single-stranded DNA
genome. At the 5’ and 3’ ends of this genome are palindromic sequences of approximately 120 to 250 nucleotides, that form hairpins and are essential for viral genome replication
.
in some animal
s. Because the viruses require actively dividing cells in order to replicate, the type of tissue infected varies with the age of the animal. The gastrointestinal tract
and lymphatic system
can be affected at any age, leading to vomiting, diarrhea and immunosuppression
, but cerebellar hypoplasia
is only seen in cats that were infected in the womb or at less than two weeks of age, and disease of the myocardium is seen in puppies infected between the ages of three and eight weeks.
Canine parvovirus
is a particularly deadly disease among young puppies
, about 80% fatal, causing gastrointestinal tract
damage and dehydration
as well as a cardiac syndrome in very young pups. It is spread by contact with an infected dog's feces. Symptoms include lethargy, severe diarrhea, fever, vomiting, loss of appetite, and dehydration. Mouse parvovirus 1, however, causes no symptoms but can contaminate immunology
experiment
s in biological research
laboratories
. Porcine parvovirus
causes a reproductive disease in swine known as SMEDI
, which stands for stillbirth, mummification, embryonic death, and infertility. Feline panleukopenia
is common in kittens and causes fever, low white blood cell
count, diarrhea, and death. Infection of the cat fetus and kittens less than two weeks old causes cerebellar hypoplasia. Mink enteritis virus
is similar in effect to feline panleukopenia, except that it does not cause cerebellar hypoplasia. A different parvovirus causes Aleutian Disease
in mink
s and other mustelids, characterized by lymphadenopathy
, splenomegaly
, glomerulonephritis
, anemia
, and death. The most accurate diagnosis
of parvovirus is by ELISA
. Dog
s, cat
s and swine can be vaccinated
against parvovirus.
Parvovirus B19
, which causes fifth disease
in humans, is a member of the Erythrovirus
genus of the Parvoviridae
.
In humans the P antigen
(also known as globoside) is the cellular receptor for parvovirus B19 virus that causes Erythema infectiosum (fifth disease) in children. This infection is sometimes complicated by severe aplastic anemia caused by lysis of early erythroid precursors.
host cells, parvoviruses bind to a sialic acid
-bearing cell surface receptor. Penetration into the cytoplasm is mediated by a phospholipase A2
activity carried on the amino-terminal peptide of the capsid VP1 polypeptide. Once in the cytoplasm, the intact virus is translocated to the nucleus prior to uncoating. Transcription only initiates when the host cell enters S-phase under its own cell cycle control, at which time the cell's replication machinery converts the incoming single strand into a duplex transcription template, allowing synthesis of mRNA
s encoding the non-structural proteins, NS1 and NS2. The mRNAs are transported out of the nucleus into the cytoplasm
where the host ribosomes translate them into viral proteins. Viral DNA replication proceeds through a series of monomeric and concatemeric duplex intermediates by a unidirectional strand-displacement mechanism that is mediated by components of the cellular fork, aided and orchestrated by the viral NS1 polypeptide. NS1 also transactivates an internal transcriptional promoter that directs synthesis of the structural VP polypeptides. Once assembled capsids are available, replication shifts from synthesizing duplex DNA to displacement of progeny single strands, which are typically negative-sense and are packaged in a 3'-to-5' direction into preformed particles within the nucleus. Mature virions may be released from infected cells prior to cell lysis, which promotes rapid transmission of the virus, but if this fails then the virus is released at cell lysis.
Unlike most other DNA viruses, parvoviruses are unable to activate DNA synthesis in host cells. Thus, in order for viral replication
to take place the infected cells must be non-quiescent (i.e. must be actively mitotic). Their inability to force host cells into S-phase means that parvoviruses are non-tumorigenic. Indeed they are commonly oncolytic, showing a strong tendency to replicate preferentially in cells with transformed phenotypes.
Parvoviridae
The Parvoviridae family includes the smallest known viruses, and some of the most environmentally resistant. They were discovered during the 1960s and affect vertebrates and insects...
taxonomic family, and also the taxonomic name of the Parvovirus genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
within the Parvoviridae
Parvoviridae
The Parvoviridae family includes the smallest known viruses, and some of the most environmentally resistant. They were discovered during the 1960s and affect vertebrates and insects...
family. This creates a confusion of terms, because parvoviruses which causes human and animal diseases are not in genus Parvovirus though they are casually called parvoviruses just as lions and tigers are sometimes called "cats," being also felids. Parvoviruses are typically linear, non-segmented single-stranded DNA virus
DNA virus
A DNA virus is a virus that has DNA as its genetic material and replicates using a DNA-dependent DNA polymerase. The nucleic acid is usually double-stranded DNA but may also be single-stranded DNA . DNA viruses belong to either Group I or Group II of the Baltimore classification system for viruses...
es, with an average genome size of 5000 nucleotides. Parvoviruses are some of the smallest viruses (hence the name, from Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
parvus meaning small) and are 18–26 nm in diameter.
Many types of mammalian species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
have a strain of parvovirus associated with them. Parvoviruses tend to be specific about the taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
of animal they will infect, but this is a somewhat flexible characteristic. Thus, all strains of canine parvovirus
Canine parvovirus
Canine parvovirus type 2 is a contagious virus mainly affecting dogs. The disease is highly contagious and is spread from dog to dog by direct or indirect contact with their feces. It can be especially severe in puppies that are not protected by maternal antibodies or vaccination. It has two...
will affect dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s, wolves, and fox
Fox
Fox is a common name for many species of omnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail .Members of about 37 species are referred to as foxes, of which only 12 species actually belong to...
es, but only some of them will infect cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s.
No members of the genus Parvovirus are currently known to infect humans, but humans can be infected by viruses within three other genera from the family Parvoviridae, including the one popularly known by the common name Parvovirus B19
Parvovirus B19
The B19 virus, generally referred to as parvovirus B19 or sometimes erythrovirus B19, was the first known human virus in the family of parvoviruses, genus erythrovirus...
. These are the Dependovirus
Dependovirus
Dependovirus is a genus of the Parvoviridae viruses, which are Group II viruses according to the Baltimore classification. The Dependovirus is part of the sub family of the Parvoviridae family known as the Parvovirinae...
es (e.g. Adeno-Associated Virus
Adeno-associated virus
Adeno-associated virus is a small virus which infects humans and some other primate species. AAV is not currently known to cause disease and consequently the virus causes a very mild immune response. AAV can infect both dividing and non-dividing cells and may incorporate its genome into that of...
), the Erythroviruses (e.g. Parvovirus B19
Parvovirus B19
The B19 virus, generally referred to as parvovirus B19 or sometimes erythrovirus B19, was the first known human virus in the family of parvoviruses, genus erythrovirus...
) and the Bocaviruses
Human bocavirus
Human bocavirus is a parvovirus that has been suggested to cause human disease. It is a probable cause of lower respiratory tract infections and it has been linked to gastroenteritis, although the role of this emerging infectious disease in human disease has not been firmly established.- History...
.
Structure
The viral capsid of a parvovirus is made up of two or three proteins, known as VP1-3 that form an icosahedralIcosahedron
In geometry, an icosahedron is a regular polyhedron with 20 identical equilateral triangular faces, 30 edges and 12 vertices. It is one of the five Platonic solids....
structure that is resistant to acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
s, base
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
s, solvents and temperature up to 50°C.
Inside the capsid is a single-stranded DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
genome. At the 5’ and 3’ ends of this genome are palindromic sequences of approximately 120 to 250 nucleotides, that form hairpins and are essential for viral genome replication
DNA replication
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance. The process starts with one double-stranded DNA molecule and produces two identical copies of the molecule...
.
Disease information on Parvoviridae
The remainder of this article discusses the disease-causing Parvoviridae viri, rather than the members of the Parvovirus genus.Diseases from Parvoviridae family (but not Parvovirus genus)
Parvoviruses can cause diseaseDisease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
in some animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s. Because the viruses require actively dividing cells in order to replicate, the type of tissue infected varies with the age of the animal. The gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
and lymphatic system
Lymphatic system
The lymphoid system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart. Lymphoid tissue is found in many organs, particularly the lymph nodes, and in the lymphoid follicles associated...
can be affected at any age, leading to vomiting, diarrhea and immunosuppression
Immunosuppression
Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...
, but cerebellar hypoplasia
Cerebellar hypoplasia (non-human)
Cerebellar hypoplasia is a disorder found in cats and dogs in which the cerebellum is not completely mature at birth.-Symptoms:Usually symptoms of cerebellar hypoplasia can be seen immediately at birth in cats, but sometimes can take two months or so to become apparent in dogs. Cerebellar...
is only seen in cats that were infected in the womb or at less than two weeks of age, and disease of the myocardium is seen in puppies infected between the ages of three and eight weeks.
Canine parvovirus
Canine parvovirus
Canine parvovirus type 2 is a contagious virus mainly affecting dogs. The disease is highly contagious and is spread from dog to dog by direct or indirect contact with their feces. It can be especially severe in puppies that are not protected by maternal antibodies or vaccination. It has two...
is a particularly deadly disease among young puppies
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
, about 80% fatal, causing gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
damage and dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
as well as a cardiac syndrome in very young pups. It is spread by contact with an infected dog's feces. Symptoms include lethargy, severe diarrhea, fever, vomiting, loss of appetite, and dehydration. Mouse parvovirus 1, however, causes no symptoms but can contaminate immunology
Immunology
Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...
experiment
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...
s in biological research
Research
Research can be defined as the scientific search for knowledge, or as any systematic investigation, to establish novel facts, solve new or existing problems, prove new ideas, or develop new theories, usually using a scientific method...
laboratories
Laboratory
A laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...
. Porcine parvovirus
Porcine parvovirus
Porcine parvovirus causes reproductive failure of swine characterized by embryonic and fetal infection and death, usually in the absence of outward maternal clinical signs...
causes a reproductive disease in swine known as SMEDI
SMEDI
SMEDI is a reproductive disease of swine caused by porcine parvovirus and porcine enterovirus. The term SMEDI usually indicates porcine enterovirus, but it also can indicate porcine parvovirus, which is a more important cause of the syndrome...
, which stands for stillbirth, mummification, embryonic death, and infertility. Feline panleukopenia
Feline panleukopenia
Feline panleukopenia virus , also known as Feline infectious enteritis, Feline distemper, feline ataxia, or cat plague, is a viral infection affecting cats, both domesticated and wild feline species. It is caused by feline parvovirus, a close relative of both type 2 canine parvovirus and mink...
is common in kittens and causes fever, low white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
count, diarrhea, and death. Infection of the cat fetus and kittens less than two weeks old causes cerebellar hypoplasia. Mink enteritis virus
Mink enteritis virus
Mink enteritis virus is a species of parvovirus that infects mink and causes enteritis. Like all parvoviruses, it is a small , spherical virus, and has a single-stranded DNA genome. The signs and symptoms of enteritis usually appear within 4–7 days after infection...
is similar in effect to feline panleukopenia, except that it does not cause cerebellar hypoplasia. A different parvovirus causes Aleutian Disease
Aleutian Disease
Aleutian Disease or Mink Plasmacytosis is a highly contagious parvovirus affecting mustelids, causing spontaneous abortion and death in minks and ferrets.-History:...
in mink
Mink
There are two living species referred to as "mink": the European Mink and the American Mink. The extinct Sea Mink is related to the American Mink, but was much larger. All three species are dark-colored, semi-aquatic, carnivorous mammals of the family Mustelidae, which also includes the weasels and...
s and other mustelids, characterized by lymphadenopathy
Lymphadenopathy
Lymphadenopathy is a term meaning "disease of the lymph nodes." It is, however, almost synonymously used with "swollen/enlarged lymph nodes". It could be due to infection, auto-immune disease, or malignancy....
, splenomegaly
Splenomegaly
Splenomegaly is an enlargement of the spleen. The spleen usually lies in the left upper quadrant of the human abdomen. It is one of the four cardinal signs of hypersplenism, some reduction in the number of circulating blood cells affecting granulocytes, erythrocytes or platelets in any...
, glomerulonephritis
Glomerulonephritis
Glomerulonephritis, also known as glomerular nephritis, abbreviated GN, is a renal disease characterized by inflammation of the glomeruli, or small blood vessels in the kidneys...
, anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
, and death. The most accurate diagnosis
Medical diagnosis
Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...
of parvovirus is by ELISA
ELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
. Dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s, cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s and swine can be vaccinated
Vaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
against parvovirus.
Parvovirus B19
Parvovirus B19
The B19 virus, generally referred to as parvovirus B19 or sometimes erythrovirus B19, was the first known human virus in the family of parvoviruses, genus erythrovirus...
, which causes fifth disease
Fifth disease
Erythema infectiosum or fifth disease is one of several possible manifestations of infection by erythrovirus, previously called parvovirus B19. The disease is also referred to as slapped cheek syndrome, slapcheek, slap face or slapped face. In Japan the disease is called 'apple sickness' or...
in humans, is a member of the Erythrovirus
Erythrovirus
Erythrovirus is a genus of viruses in the family Parvoviridae.The type species is parvovirus B19.-Virology:Erythroviruses are small , non-enveloped icosahedral viruses...
genus of the Parvoviridae
Parvoviridae
The Parvoviridae family includes the smallest known viruses, and some of the most environmentally resistant. They were discovered during the 1960s and affect vertebrates and insects...
.
In humans the P antigen
P antigen system
P antigen system is a human blood group system based upon genes on chromosome 22. The P antigens are carbohydrate antigens that include P1, P, and Pk. The P antigen is a receptor for the human pathogen Parvovirus B19 and is the target of auto-anti-P IgG antibodies in paroxysmal cold...
(also known as globoside) is the cellular receptor for parvovirus B19 virus that causes Erythema infectiosum (fifth disease) in children. This infection is sometimes complicated by severe aplastic anemia caused by lysis of early erythroid precursors.
Replication as Disease Vector
To enterViral entry
Viral entry is the earliest stage of infection in the viral life cycle, as the virus comes into contact with the host cell and introduces viral material into the cell. The major steps involved in viral entry are shown below. Despite the variation among viruses, the generalities are quite similar...
host cells, parvoviruses bind to a sialic acid
Sialic acid
Sialic acid is a generic term for the N- or O-substituted derivatives of neuraminic acid, a monosaccharide with a nine-carbon backbone. It is also the name for the most common member of this group, N-acetylneuraminic acid...
-bearing cell surface receptor. Penetration into the cytoplasm is mediated by a phospholipase A2
Phospholipase A2
Phospholipases A2 are enzymes that release fatty acids from the second carbon group of glycerol. This particular phospholipase specifically recognizes the sn-2 acyl bond of phospholipids and catalytically hydrolyzes the bond releasing arachidonic acid and lysophospholipids...
activity carried on the amino-terminal peptide of the capsid VP1 polypeptide. Once in the cytoplasm, the intact virus is translocated to the nucleus prior to uncoating. Transcription only initiates when the host cell enters S-phase under its own cell cycle control, at which time the cell's replication machinery converts the incoming single strand into a duplex transcription template, allowing synthesis of mRNA
Messenger RNA
Messenger RNA is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes. Here, the nucleic acid polymer is translated into a polymer of amino acids: a protein...
s encoding the non-structural proteins, NS1 and NS2. The mRNAs are transported out of the nucleus into the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
where the host ribosomes translate them into viral proteins. Viral DNA replication proceeds through a series of monomeric and concatemeric duplex intermediates by a unidirectional strand-displacement mechanism that is mediated by components of the cellular fork, aided and orchestrated by the viral NS1 polypeptide. NS1 also transactivates an internal transcriptional promoter that directs synthesis of the structural VP polypeptides. Once assembled capsids are available, replication shifts from synthesizing duplex DNA to displacement of progeny single strands, which are typically negative-sense and are packaged in a 3'-to-5' direction into preformed particles within the nucleus. Mature virions may be released from infected cells prior to cell lysis, which promotes rapid transmission of the virus, but if this fails then the virus is released at cell lysis.
Unlike most other DNA viruses, parvoviruses are unable to activate DNA synthesis in host cells. Thus, in order for viral replication
Self-replication
Self-replication is any behavior of a dynamical system that yields construction of an identical copy of that dynamical system. Biological cells, given suitable environments, reproduce by cell division. During cell division, DNA is replicated and can be transmitted to offspring during reproduction...
to take place the infected cells must be non-quiescent (i.e. must be actively mitotic). Their inability to force host cells into S-phase means that parvoviruses are non-tumorigenic. Indeed they are commonly oncolytic, showing a strong tendency to replicate preferentially in cells with transformed phenotypes.