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A. Méndez-Vilas (Ed.)
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Diversity of G-type and P-type of human and animal
rotaviruses and its genetic background
N. Kobayashi *,1, M. Ishino1, Y-H. Wang2, M. Chawla-Sarkar3, T. Krishnan3, and T.N.
Naik3
1
Department Hygiene, Sapporo Medical University School of Medicine, S-1 W-17, Chuo-ku, Sapporo,
Japan
2
Section of Virology, Wuhan Centers for Disease Prevention and Control, Wuhan, P.R.China
3
Division of Virology, National Institute of Cholera and Enteric Diseases, Kolkata, India
Rotavirus is a major etiologic agent of gastroenteritis in infants and young children worldwide, and also in
variety of mammals and birds. The most prevalent species of rotavirus, i.e., group A rotavirus is highly
diverse antigenically and genetically. Two major outer capsid proteins of rotavirus, VP7 and VP4, contain
neutralization antigens. Based on the antigenicities and gene sequence diversity of these proteins, two
independent serotypes (G-serotype and P-serotype) and genotypes (G-type and P-type) have been
discriminated. Sixteen G-types and 28 P-types have been reported so far. Prevalence of G-type and P-type
is different depending on animal species, region/country, and seasons/years. A large number of
epidemiologic investigations have revealed occurrence of globally emerging types of rotavirus, and recent
phylogenetic studies have provided suggestions for origin of these viruses and their transmission. Present
status of prevalence, distribution, and diversity of rotavirus G-type and P-type is discussed with molecular
epidemiologic backgrounds.
Keywords; rotavirus, serotype, genotype, G-type, P-type
1. Introduction of Rotavirus
Rotavirus is ubiquitously distributed to humans and animals. Rotavirus has been recognized as a cause
of infantile diarrhea since 1970s, and is now established as the most common cause of gastroenteritis in
infants and young children. It is also recognized that some species of rotavirus cause gastroenteritis in
adults. Before identification of rotaviruses in humans, rotavirus had been found as an important cause of
diarrhea in animals, especially young livestock and poultry.
The genus Rotavirus, a member of the family Reoviridae [1,2], has 11 segments of double-stranded
(ds) RNA as genome. The rotavirus RNA segments which are different in size are separated by
polyacrylamide gel electrophoresis and are observed as an RNA pattern after staining of the RNA in gel.
The RNA patterns are distinct among different rotavirus species and also different strains. Rotavirus
virion, a complete infectious particle, has approximately 70 nm in diameter, and consists of three
concentric layers, i.e., inner core, inner capsid, and outer capsid (Fig.1). Three viral proteins VP1-VP3
constitute the inner core that contains genomic RNA segments inside. Inner capsid is composed of VP6
which is the most abundant vial protein. Outer capsid is composed of two proteins, VP7 and VP4, which
contain neutralization antigens. VP7 constitutes smooth surface of the outer capsid, while VP4 exists as a
spike protein projecting from the surface.
Rotavirus is differentiated into at least seven species, i.e., Rotavirus A-G, based on antigenicity of
VP6 as well as characteristics of genomic RNA. These species have been referred to also as group A-G
rotavirus. Group A rotavirus is found as the most prevalent cause of gastroenteritis in humans and
animals worldwide. Group B rotavirus is unique because this virus causes gastroenteritis primarily in
adults, and has been detected only in some Asian countries. Similar to group A rotavirus, group C
rotavirus causes diarrhea in children, but this virus is extremely less prevalent although it has been
detected in many countries. While only group A, B, C rotaviruses have been found in human diarrheal
*
Corresponding author: e-mail: [email protected], Phone: +81 116112111
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cases so far, a novel human rotaviruses which may not be classified into groups A-C and other known
groups were reported recently [3,4]. The novel rotavirus, designated ADRV-N and B219 which were
detected independently in China and Bangladesh, respectively, were found in adult diarrheal cases. Viral
gene sequences of these two viruses were extremely similar, but distinct from those of group A-C
rotaviruses and the RNA patterns were also different from those of any previously known rotavirus
groups. Therefore, it is probable that these human rotaviruses may belong to a novel group (new
species) of rotavirus.
Fig. 1 Schematic representation of dissection
of rotavirus particle (left) and elctrophoretic
migration pattern of rotavirus RNA segments
(right). RNA segment numbers are indicated
on the left of the RNA pattern. Three structural
proteins that determine serological types of
rotavirus are indicated.
2. Outline of group A rotavirus infection
Group A rotavirus (Rotavirus A) is a major pathogen of severe gastroenteritis in infants and young
children worldwide. It was estimated recently that rotavirus accounts for 39% of hospitalizations for
childhood diarrhea, and causes 611,000 rotavirus diarrhea-related death in the world annually [5].
Although mortality due to rotavirus diarrhea has been recorded mostly in developing countries, rotavirus
infection in children is also common in developed countries causing considerable disease burden due to
the medical and societal costs. For this global issue on public health, necessity of rotavirus vaccine has
been well recognized and attempt to develop rotavirus vaccine has been initiated since 1980’s. In 2006,
two rotavirus vaccines, Rotarix and Rotateq, were developed and the use of them was approved in EU
and/or USA, and many other counties. By this epoch, it is anticipated that the countermeasures against
rotavirus diarrhea will be changed and disease burden due to rotavirus diarrhea will be evidently reduced
globally in the near future.
Efficacy of rotavirus vaccine is essentially related to its antigenicity. Rotavirus is antigenically highly
diverse in nature. Therefore, to investigate diversity, distribution and prevalence of antigenic types of
rotavirus in human population is important and significant to develop effective rotavirus vaccine and also
to evaluate its efficacy.
After entrance orally into gastrointestinal tract, propagation of rotavirus occurs in epithelial cells of
villi of small intestine. Cell lysis occurs finally by the viral propagation, causing curtailment of the villi.
Diarrhea due to rotavirus infection is considered to be caused by some different mechanisms [6].
Destruction of intestinal epithelial cells directly hinders absorption of water and sugars. Rotavirus
infection in the cells also causes changes of metabolism of disaccharides, decreasing absorption of water,
salt and sugar. Diarrhea observed remarkably before destruction of epithelial cells is considered to be
implicated in activation of enteric nervous system via neurotransmitters. In addition, rotavirus non-
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structural protein NSP4 or its peptide fragment has an enterotoxin-like activity which induces high
concentration of intracellular calcium, causing various effects including excretion of water from the cells.
NSP4 which is produced in the infected cells is released outside cells and reach neighbouring noninfected cells, exhibiting the enterotoxin activity.
To prevent rotavirus infection in intestine, secreting IgA directed to rotavirus plays a major role [7].
Although the mechanism is unknown, serum IgG is also related to protection of rotavirus infection.
While cell-mediated immunity to rotavirus also exists and CTL epitopes have been identified in viral
proteins, its significance in protection against acute rotavirus infection is not clear. Most attempts to
develop rotavirus vaccine have aimed at inducing antibody to rotavirus.
Neutralization antibodies to rotavirus are directed to outer capsid proteins VP7 and VP4. Therefore,
these proteins are considered as the most important antigens for immunization, to obtain protective
immunity to rotavirus. Although rotavirus is not neutralized by antibody to VP6, anti-VP6 IgA antibody
is able to inhibit propagation of rotavirus in the infected epithelial cells, by the mechanism designated
“expulsion”[7]. Antibody to NSP4 may reduce severity of diarrhea caused by rotavirus infection,
however, it is unable to protect rotavirus infection.
3. Serotype of group A rotavirus
Serological types of group A rotavirus is determined by inner capsid protein (VP6) and outer capsid
proteins (VP7, VP4). VP6 is encoded by RNA segment 6 and contains group-specific antigen and
subgroup (I or II) specific antigen, both of which are non-neutralization antigens (Fig.1). In contrast,
since outer capsid proteins are exceedingly relevant to protective immunity to rotavirus infection as
described above, serological typing of these proteins is significant, especially for development of
rotavirus vaccine.
Based on antigenicity of outer capsid proteins VP7 and VP4, two independent serotype systems, i.e.
G-serotype and P-serotype have been established. In the early years of rotavirus study, the rotavirus
“serotype” represents serologic type of VP7 only, which corresponds to G-serotype, because VP7 was
highly immunogenic when purified virus is immunized parenterally to animals. Different G-serotypes
have been discriminated when difference in more than 20 times of neutralization titers was observed in
cross neutralization test with hyperimmune antisera to rotaviruses [8]. As more simple and practical
method, enzyme-linked immunosorbent assay (ELISA) with G serotype-specific monoclonal antibodies
was developed for typing of human rotaviruses [9].
Thereafter, importance of anti-VP4 neutralization antibody as protection of rotavirus infection in vivo
was recognized, a serotyping system based on VP4, namely P-serotype, was proposed [10]. However, to
discriminate different P serotypes serologically, preparation of expressed and purified VP4 protein or
reassortant viruses having common VP7 but VP4 from different strains are required as immunogens, to
subtract effect of antibody response to VP7 and to observe net activity of anti-VP4 antibody. By such
complicated procedures, discrimination of rotavirus P-serotypes has not been completely established.
While human rotavirus P-serotypes are able to be determined by ELISA with specific monoclonal
antibodies, this method has not become common. At least 16 different G serotypes and 14 different Pserotypes have been discriminated so far. In some P-serotypes, antigenic variants in a single P-serotypes
are further discriminated as subtypes, e.g., P1A and P1B. Epidemiologic surveillance of the G- and Pserotypes to clarify prevalent types are important to consider rotavirus vaccine.
4. Genotype of group A rotavirus
As the molecular epidemiology of rotavirus developed recently, genetic typing based on VP7 gene and
VP4 gene, G-genotype and P-genotype, respectively, were developed. These are referred to also as “Gtype” and “P-type”. VP7 is encoded by RNA segment 7, 8, or 9 and comprises 326 amino acids. VP7
contains three major variable regions where sequences are divergent among different G-serotypes but
conserved within a single G-serotype [1]. They are regions A (amino acid 87-101), B (amino acid 142152), and C (amino acid 208-221).
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When the whole VP7 sequence is noted, rotaviruses belonging to the same G-serotype generally show
more than 90 % amino acid sequence identity, although there are some exceptions depending on Gserotype. G-type is determined by the sequences of the variable regions as well as sequence identity of
whole VP7 sequences. At present, numbering system of G-type (G1-G16) is identical to that of Gserotype. Although serological characterizations have not been completed for some G-types (G12, G15,
and G16), these are suggested to represent G-serotypes distinct from those described so far.
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VP4 is encoded by RNA segment 4 and comprises 775 amino acids in most of human rotaviruses [1].
VP4 is made up of two portions corresponding to VP8 and VP5 which represent products cleaved by
trypsin. Antigenic epitopes on VP4 resides in both VP8 (e.g., amino acid 87-89) and VP5 (e.g., amino
acid 305, 388-393, 433). Different P-types have been discriminated by presence of less than 89% amino
acid sequence identity in VP4, based on the early finding that VP4 amino acid sequence identity of
identical P-serotype was 89% or more. P-type is usually described as the number in bracket, and has
different numbering system from P-serotype. Sometimes P-type is described with P-serotype, as
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“P[8]1A”. So far, at least 28 different P-types have been reported and a sequence data of a porcine
rotavirus strain (ICB2212) representing a putative novel P-type is deposited in GenBank database.
Because of the complexity of determining P-serotype, genetic typing system (P-type) has more
developed, and thus P-serotype has not been assigned to all the P-types. It should be noted that
discrimination of P-type does not necessarily correspond to P-serotypes. For example, rotavirus strains
69M and H2 that belong to P-types P[10] and P[12], respectively, are grouped into the same P-serotype 4.
VP8 sequence is more divergent than VP5 sequence and contains more P-serotype-specific regions.
Therefore, only VP8 sequence is used for discrimination of some P-types (P[22], P[23]).
Representative G-types and P-types, especially those of human rotaviruses, have been recently
identified by RT-PCR with type-specific primers in epidemiologic surveillance, and the prevalence of
these genetic types are regarded mostly as substitutes of G- and P-serotypes [11,12].
Recently, novel and rare G-types and P-types have been identified in human rotaviruses, in addition to
the predominant types described so far. Some of them have been detected increasingly worldwide and
therefore recognized as emerging types. On the other hand, recent progress in investigation on the
distribution of rotavirus G-types and P-types in various animal species enable us to estimate the ecology
of rotavirus in nature and origin of the emerging types in human rotavirus. Recently, the numbers of Gtype and P-type of rotavirus have increased and many reports have been published on prevalence and
diversity of these types. However, as these findings are accumulated, knowledge on rotavirus types
seems to have become too much complicated to understand its overview. In the following sections,
prevalence and diversity of G-types and P-types in human and various animals, and genetic relatedness
among these types (VP7 and VP4 sequences) are summarized for more concise and essential, and
practical understanding of rotavirus types.
5. Prevalence of G-types and P-types in nature
G-types and P-types found in rotaviruses from various animal species are shown in Table 1. In human
rotaviruses, G1, G2, G3 and G4 have been the most prevalent G-types worldwide, although 11 G-types
were reported. Among the P-type, P[4], P[6], and P[8] are most prevalent. P[4] is usually associated with
G2, while P[8] is associated with G1, G3, or G4. P[6] is found with any of G1 through G4, in human
rotavirus. The rotavirus vaccine Rotarix is composed of a single component, an attenuated human
rotavirus with G1P[8] which is the most prevalent type of human rotavirus. Another rotavirus vaccine,
RotaTeq consists of five reassortant rotavirus strains having major antigenic types of human rotavirus,
i.e., G1-G4, and P[8].
G9 and G12 are recognized as emerging types which have been globally increasing recently. G5 and
G8, which are prevalent in pig and cattle, respectively, are rarely detected in human rotaviruses.
However, some reports described that such rare types have become prevalent in limited regions
(countries). For understanding origin of such unusual G-type, information of prevalent G-types in
individual animal species may be suggestive. G-type and P-type of representative human and animal
rotavirus strains are shown in the Table 2.
Rotaviruses from each animal species have predominant and intrinsic G-type(s) and P-type(s).
Prevalence of G-types and P-types are different depending on animals (Table 1). For example, in pig, G3,
G4, G5, G9, and G11 are prevalent, whereas G6, G8, and G10 are common in bovine rotaviruses. G7 is
highly specific to avian rotaviruses, and similarly G13, G14, and G16 are mostly found in equine
rotavirus. In contrast, G3 rotavirus has been detected in almost all the animal species. Such host
specificity of G-types may suggest extent of transmission of rotavirus among different species in nature.
The predominant G-types in cattle are common to those in sheep/goat, suggesting the high frequency of
rotavirus transmission between these two animal species. However, prevalent G-types are not common
between cattle and pig, suggesting that transmission between these two species may be less frequent. It is
notable that most of human rotavirus G-types have been detected in porcine rotavirus, which suggests
close relatedness of human rotavirus and porcine rotavirus, i.e., occurrence of transmission between
human and pig in nature. G3 is a common type to those in various animals, and G4 was suggested to be
closely related to porcine rotaviruses. However, although G1, G2, G12 were detected in pig and cattle,
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these types are highly prevalent in human and thus they are considered to be originally intrinsic types in
human rotaviruses.
Compared with G-types, P-types seem to be more specific to individual animal species, because each
P-type is prevalent type in only one or two animal species. Similarly to the case of G-type, some
predominant P-types are common between cattle and sheep/goat. Between human rotavirus and porcine
rotavirus, only P[6] was common as a prevalent type. Other prevalent types in human rotavirus, P[4] and
P[8] are rarely found in other animal species, suggesting that these are intrinsic types in human.
6. Phylogenetic relatedness among G-types and P-types
Genetic relatedness of various G-types are evident by phylogenetic tree of VP7 sequence (Fig.2). G7
which is specific to avian rotavirus is genetically far distant from those of mammalian rotaviruses.
Human rotavirus G-types may be grouped into four clusters; G9-G3 cluster, G2-G12 cluster, G1 cluster,
and G4 cluster. Among them, G9-G3 and G4 clusters are also recognized as porcine rotavirus lineages.
Porcine rotaviruses are found in also another main cluster of G5 and G11 which are genetically relatively
close. G6 and G8 are also genetically close and form a cluster of bovine rotaviruses. There are more two
bovine rotavirus lineages (G10 and G15). Although equine rotavirus lineages (G13, G14, G16) are
genetically distant, G14 is relatively close to G3 which is distributed widely to mammalians, and also to
G9, an emerging type as described later.
Fig. 2 Phylogenetic tree of VP7 amino acid sequences of rotavirus strains representing each G-type
constructed by the neighbour-joining method. G-type of the strain and major animal species associated
with individual G-types are indicated. A single or some G-types are grouped as a cluster, based on
animal species. The scale bar indicates 10 % amino acid difference.
In the phylogenetic tree of VP4 (VP8), human rotaviruses are classified into two major lineages
(human cluster 1 and 2 ) and a minor lineage of human and equine rotaviruses (P[10] and P[12]) (Fig.3).
Human cluster 1 includes main P types of human rotavirus, i.e., P[8], P[4], and P[6], and a minor type
P[19]. P[6] and P[19] form a pocine rotavirus lineage. Human cluster 2 includes rare types P[9] and
P[25], and two major lapine rotavirus types, P[14] and P[22]. Therefore, VP4 of human rotavirus may
be partially related to porcine rotavirus, and slightly to lapine and equine rotaviruses. A few lineages are
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found for murine rotaviruses (P[16]-P[20]), equine rotaviruses (P[18], P[10]-P[12]), and simian
rotaviruses ((P[2]-P[3]), P[24]). In contrast, more divergent nature of bovine and porcine rotaviruses
were observed, suggesting that rotavirus has well adapted to these animal species and viruses from
several different clonal origins are circulating in nature. Recently reported two P-types in porcine
rotaviruses, P[27] and P[28] , are genetically very close (90% identity in VP4 sequence) and thus are
possible to belong to a single P-type.
Fig. 3 Phylogenetic tree of VP8 amino acid sequences of rotavirus strains representing each P-type
constructed by the neighbour-joining method. P-type of the strain and major animal species associated
with individual P-types are indicated. A single or some P-types are grouped as a cluster, based on
animal species. The scale bar indicates 10 % amino acid difference.
7. Phylogenetic relatedness of VP7 within a single G-type
Phylogenetic analysis of VP7 (VP4) which defines single G-type (P-type) has been increasingly
employed for molecular epidemiology of rotavirus, especially to estimate transmission route and
dynamic expansion of notable virus strains. Although in human rotavirus, G1-G4 have been generally
predominant types worldwide, the most prevalent type among them is different depending on region
(country) and changes at intervals of several years [13]. Furthermore, increase of emerging types (e.g.,
G5, G9, and G12) have been noted globally or in specific regions. For such emerging types as well as
common types, phylogenetic analysis of VP7 and/or VP4 provides meaningful suggestions on origin and
relatedness to the known strains for the rotavirus strain in question. As examples, molecular
epidemiologic studies of G3 and G9 human rotaviruses recently detected in China are described below.
In China, G1 has been described as a predominant type of human rotavirus in different areas before
2000. However, epidemiologic change in the predominant type of rotavirus occurred since the year 2000
by unknown reason, and G3 has become overwhelmingly predominant type in China, which was
described in our study in Wuhan city between 2000 and 2006 [14], and also in studies conducted in other
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regions in China. In our epidemiologic study on rotavirus in China, prevalence of group A rotavirus in
diarrheal diseases were investigated in adult patients, as well as pediatric patents, to know prevalence of
rotavirus in adults and its relatedness to rotaviruses in children. Rotavirus positive rate in adult patients
was 9.0%, a lower rate than that in children (23.9%). However, it was of note that epidemic season of
rotavirus in adults (November to January) corresponded to that in children, and G3P[8] strain was
predominant (more than 80% ) in both adults and children. To know the genetic relatedness of G3
rotaviruses between adults and children, and to other animal and human rotaviruses reported previously,
VP7 gene of representative strains were determined and phylogenetic analysis was performed.
Fig. 4 Phylogenetic tree of VP7 gene sequences of G3 rotavirus strains constructed by the neighbourjoining method. Animal species, country of isolation, and/or isolation year, and lineage are indicated.
The scale bar indicates 10 % nucleotide difference.
G3 is distributed to most of mammalian species and G3-VP7 gene is genetically most diverse among
the VP7 gene of other G-types analyzed so far. While more than 90% amino acid sequence identity is
usually observed within strains belonging to a single G-type, identity as low as 80% is observed between
strains from different animal species. As shown in Fig.4, at least three lineages of human rotavirus were
identified. In our present study, sequence identity among 6 adult G3 strains and 4 pediatric G3 strains
showed more than 98% identities, and these strains converged into a few branches in the lineage 3 of the
phylogenetic tree. Such high level of sequence identity and phylogenetic convergence in the divergent
G3 sequence indicated that identical G3 rotavirus clone were prevalent among adults and children,
suggesting that transmission of G3 rotavirus might have occurred endemically in adults and children in
Wuhan, China. These G3 rotaviruses analyzed in Wuhan were genetically distant from four Chinese
strains reported in 1980’s and 1990’s (lineage 2), but considerably close to Chinese strains of late 1990’s,
and Malaysian, Thai, and Indian stains. Although more epidenmiologic analyses may be required, it is
possible that recently prevalent G3 rotaviruses might have been originated from Southeastern Asian
countries.
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In the above study, a single strain of G9 rotavirus (L169) was detected in 2004. G9 is recognized as
the emerging type of rotavirus that has been widespread globally since the mid 1990’s. When
phylogenetic relatedness is analyzed among G9 strains reported so far, some lineages are found (Fig.5).
Most of the G9 strains detected recently globally (Asia, Africa, Europe, South America, and USA)
belong to the lineage 3, which is distant from lineage 1 which includes early G9 strains detected in USA
(e.g., strain WI61). This finding suggests that G9 viruses might have been distributed globally, after
original early clones of G9 rotavirus might have been subjected to genomic evolutions. In china, G9 has
been detected at low rate (<5%) since 1997, and VP7 gene sequence was determined for only two strains
and these were not assigned to lineage 3. However, the strain L169 was found to belong to lineage 3 for
the first time as a Chinese strain, which demonstrated that globally spreading clone of G9 rotavirus has
been actually distributed to China. It is noteworthy to investigate whether the G9 virus will predominate
in the near future in China, and for this purpose, continuous epidemiologic surveillance and phylogenetic
study for rotavirus strains will be of great importance.
Fig. 5 Phylogenetic tree of VP7 gene sequences of G9 rotavirus strains constructed by the neighbourjoining method. Country of isolation and lineage are indicated. The scale bar indicates 10 % nucleotide
difference.
8. G12 as an emerging type of human rotavirus
At present, global spread of G12 human rotaviruses is one of the most notable topics on epidemiology
of rotavirus. The first G12 rotavirus represented by L26 was detected in children in Philippines in 1987
[15]. These rotaviruses were detected in many diarrheal cases and described in the original report as
“unusual human rotavirus” because G-serotype was not assigned to G1-G4 and these viruses showed
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subgroup I specificity and “long” RNA patterns which are characteristics of animal rotaviruses. Further
genetic characterization revealed that G-serotype of L26 strain belonged to a novel one [16]. However,
thereafter, G12 had not been detected anywhere for more than 10 years. Unexpectedly in 1998 and 1999,
G12 human rotaviruses were detected in Thailand and USA, respectively. Subsequently, G12 human
rotaviruses were reported in Asian countries including India (1999-2005), Bangladesh (2000-2005),
Japan (2003), Korea (2002-2003), and Nepal (2003-2004), and also in European countries, such as UK
(2002, 2006), Belgium (2003), Hungary (2005), and Slovenia (2006), and in South American countries
(Argentina, 1999-2003; Brazil, 2004). G12 rotaviruses were detected in three different combinations
with P[4], P[6], or P[8], and G12 rotaviruses were proved to be genetically highly diverse population
[17]. These findings suggest that the G12 rotaviruses might have been caused by genetic reassortment, a
similar mechanism to the emergence and expansion of G9 rotaviruses, the fifth major type of human
rotavirus. Although origin of G12 has not been elucidated, porcine rotavirus G12 P[7] was detected in
India recently, for the first time as G12 virus in animal [18]. On the other hand, the first G12 human
rotavirus strain L26 has porcine rotavirus-like NSP2 and NSP5 gene segments [17]. These findings may
suggest that G12 rotavirus might be originated from animal rotavirus, possibly porcine rotavirus. At
present, G12 has been regularly detected in recent surveys in some countries, and thus seems to be
established as the sixth major human rotavirus G-type.
Emergence and expansion of unusual G-type may reduce the efficacy of rotavirus vaccine. Therefore,
surveillance of human rotaviruses, especially identification of rare G-types may be also significant. As
suggested for G9 and G12 rotaviruses, transmission of rotavirus from animal to human, and mixed
infection with animal and human rotaviruses may occur frequently in nature. Therefore, continuous
epidemiologic surveillance of animal rotaviruses may be also important to estimate the origin of the
emerging human rotavirus G-types. Recently, gene sequence data of a number of human and animal
rotavirus strains have been accumulated and available for molecular epidemiologic study of rotavirus.
However, for more reliable and complete study to understand relatedness among various human and
animal rotaviruses, sufficient sequence data has not been yet available. Although there are numerous
sequence information of VP7, VP4, VP6, and NSP4 in GenBank database, sequence data of other viral
proteins are limited in no. of strains and/or animal species. Therefore, whole sequence (11 RNA
segment) should be determined and deposited to the database for rotavirus strains which are intrinsic to
individual animal species, as a source of basic information. Furthermore, it may be preferable that
rotavirus sequence data from the animal species should be determined periodically and accumulated to
observe trends of occurrence of mutations. Such effort will contribute to promote molecular
epidemiologic characterization of unusual rotavirus strains which have been reported recently in many
countries.
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A. Méndez-Vilas (Ed.)
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