Seroepidemiological study of genogroup I and II calicivirus infections in South and southern Africa

Arc protein, a remnant of ancient retrovirus, forms virus-like particles, which are abundantly generated by neurons during epileptic seizures, and affects epileptic susceptibility in rodent models

A product of the immediate early gene Arc (Activity-regulated cytoskeleton-associated protein or Arc protein) of retroviral ancestry resides in the genome of all tetrapods for millions of years and is expressed endogenously in neurons. It is a well-known protein, very important for synaptic plasticity and memory consolidation. Activity-dependent Arc expression concentrated in glutamatergic synapses affects the long-time synaptic strength of those excitatory synapses. Because it modulates excitatory-inhibitory balance in a neuronal network, the Arc gene itself was found to be related to the pathogenesis of epilepsy. General Arc knockout rodent models develop a susceptibility to epileptic seizures. Because of activity dependence, synaptic Arc protein synthesis also is affected by seizures. Interestingly, it was found that Arc protein in synapses of active neurons self-assemble in capsids of retrovirus-like particles, which can transfer genetic information between neurons, at least across neuronal synaptic boutons. Released Arc particles can be accumulated in astrocytes after seizures. It is still not known how capsid assembling and transmission timescale is affected by seizures. This scientific field is relatively novel and is experiencing swift transformation as it grapples with difficult concepts in light of evolving experimental findings. We summarize the emergent literature on the subject and also discuss the specific rodent models for studying Arc effects in epilepsy. We summarized both to clarify the possible role of Arc-related pseudo-viral particles in epileptic disorders, which may be helpful to researchers interested in this growing area of investigation.

The First Molecular Detection of Aichi Virus 1 in Raw Sewage and Mussels Collected in South Africa

Aichi virus 1 (AiV-1) has a worldwide distribution and is associated with gastroenteritis in humans. In this study, raw sewage and mussel samples were analyzed for the presence of AiV-1 using reverse transcription-PCR (RT-PCR). Amplification and sequencing of the 3CD and VP1 genomic regions followed by phylogenetic analysis using selected genome sequences revealed the presence of AiV-1, genotype B. The results highlight the importance of further screening to evaluate the prevalence and epidemiology of this clinically important virus in South Africa.

The First Norovirus Longitudinal Seroepidemiological Study From Sub-Saharan Africa Reveals High Seroprevalence of Diverse Genotypes Associated With Host Susceptibility Factors

Background

Human noroviruses (HuNoVs) are a prominent cause of gastroenteritis, yet fundamental questions remain regarding epidemiology, diversity, and immunity in sub-Saharan African children. We investigated HuNoV seroprevalence and genetic and sociodemographic risk factors in Ugandan children.

Methods

We randomly screened 797 participants of a longitudinal birth cohort (Entebbe, EMaBS) and 378 from a cross-sectional survey (rural Lake Victoria, LaVIISWA), for antibodies against HuNoV genotypes by ELISA. We used linear regression modeling to test for associations between HuNoV antibody levels and sociodemographic factors, and with the human susceptibility rs601338 FUT2 secretor SNP and histo-blood group antigens (A/B/O).

Results

Of EMaBS participants, 76.6% were seropositive by age 1, rising to 94.5% by age 2 years. Seroprevalence in 1 year olds of the rural LaVIISWA survey was even higher (95%). In the birth cohort, 99% of seropositive 2 year olds had responses to multiple HuNoV genotypes. We identified associations between secretor status and genogroup GII antibody levels (GII.4 P = 3.1 × 10-52), as well as ABO and GI (GI.2 P = 2.1 × 10-12).

Conclusions

HuNoVs are highly prevalent in Ugandan children, indicating a substantial burden of diarrhea-associated morbidity with recurrent infections. Public health interventions, including vaccination, and increased surveillance are urgently needed.

Norovirus epidemiology in South African children <5 years hospitalised for diarrhoeal illness between 2009 and 2013

Public health interest in norovirus (NoV) has increased in recent years following improved diagnostics, global burden estimates and the development of NoV vaccine candidates. This study aimed to describe the detection rate, clinical characteristics and environmental features associated with NoV detection in hospitalized children <5 years with diarrhoea in South Africa (SA). Between 2009 and 2013, prospective diarrhoeal surveillance was conducted at four sites in SA. Stool specimens were collected and screened for NoVs and other enteric pathogens using molecular and serological assays. Epidemiological and clinical data were compared in patients with or without detection of NoV. The study detected NoV in 15% (452/3103) of hospitalized children <5 years with diarrhoea with the majority of disease in children <2 years (92%; 417/452). NoV-positive children were more likely to present with diarrhoea and vomiting (odds ratio (OR) 1·3; 95% confidence interval (CI) 1·1-1·7; P = 0·011) with none-to-mild dehydration (adjusted OR 0·5; 95% CI 0·3-0·7) compared with NoV-negative children. Amongst children testing NoV positive, HIV-infected children were more likely to have prolonged hospitalization and increased mortality compared with HIV-uninfected children. Continued surveillance will be important to consider the epidemic trends and estimate the burden and risk of NoV infection in SA.

Norovirus Epidemiology in Africa: A Review

Norovirus (NoV) is recognised as a leading cause of gastroenteritis worldwide across all age groups. The prevalence and diversity of NoVs in many African countries is still unknown, although early sero-prevalence studies indicated widespread early infection. Reports on NoVs in Africa vary widely in terms of study duration, population groups and size, inclusion of asymptomatic controls, as well as genotyping information. This review provides an estimate of NoV prevalence and distribution of genotypes of NoVs in Africa. Inclusion criteria for the review were study duration of at least 6 months, population size of >50 and diagnosis by RT-PCR. As regions used for genotyping varied, or genotyping was not always performed, this was not considered as an inclusion criteria. A literature search containing the terms norovirus+Africa yielded 74 publications. Of these 19 studies from 14 out of the 54 countries in Africa met the inclusion criteria. Data from studies not meeting the inclusion criteria, based on sample size or short duration, were included as discussion points. The majority of studies published focused on children, under five years of age, hospitalised with acute gastroenteritis. The mean overall prevalence was 13.5% (range 0.8–25.5%) in children with gastroenteritis and 9.7% (range 7–31%) in asymptomatic controls, where tested. NoV GII.4 was the predominant genotype identified in most of the studies that presented genotyping data. Other prevalent genotypes detected included GII.3 and GII.6. In conclusion, NoV is a common pathogen in children with diarrhoea in Africa, with considerable carriage in asymptomatic children. There is however, a paucity of data on NoV infection in adults.

Current Status of Norovirus Infections in Children in Sub-Saharan Africa

Noroviruses are a leading cause of acute sporadic gastroenteritis worldwide. In Sub-Saharan Africa, information regarding norovirus infections in children is scarce. A systematic review of studies performed between 1993 and June 2015 was conducted to establish the genotypic distribution and prevalence of norovirus infections in children (≤17) in Sub-Saharan Africa. Analysis of data from 19 studies involving 8,399 samples from children with symptomatic and nonsymptomatic gastroenteritis revealed prevalence of 12.6% (range 4.6% to 32.4%). The prevalence of norovirus infections was higher in symptomatic children (14.2%) than asymptomatic children (9.2%). Genogroup II (GII) was the most prevalent genogroup accounting for 76.4% of all the reported norovirus infections. The rest of the infections were GI (21.7%) and GI/GII (1.9%). The most common genotypes were GII.4 (65.2%), GI.7 (33.3%), and GI.3 (21.3%). These statistics were calculated from studies carried out in 12 out of 48 Sub-Saharan African countries. Therefore, more studies involving several countries are required to determine fully the epidemiology of noroviruses and their contribution to childhood diarrhoea in Sub-Saharan Africa.

Human Norovirus prevalence in Africa: a review of studies from 1990 to 2013

OBJECTIVES

To assess the contribution of Human Norovirus to diarrhoeal diseases in Africa.

METHODS

We conducted a systematic review of the PubMed and EMBASE databases for published articles of Human Norovirus in Africa between 1990 and 2013. Data were extracted from selected studies and analysed.

RESULTS

A total of 208 eligible studies were identified, of which 55 (from 19 countries) met the inclusion criteria. Many cases were of sporadic gastroenteritis (70.9%) in children (82%), 65.4% of which were seen in an outpatient setting. Over half (59.4%) of the affected children were under 5 years of age. The pooled prevalence rate of Human NoV was 11% (95% CI 8-14%), and the meta-analysis indicated significant heterogeneity between the studies. However, the conditional negative binomial regression could not clearly find the factors affecting the Human NoV prevalence rates reported. A close relationship was found between Human Norovirus strains from environmental and clinical samples.

CONCLUSION

Unreported sporadic gastroenteritis cases of Human Norovirus are common in Africa. Most are community-associated infections. Possible environmental transmission routes have been documented. Combined environmental and clinical studies are required for targeted actions to control transmission of Human Norovirus in Africa. Systematic surveillance of Human Norovirus is needed to measure the burden of Norovirus-induced gastroenteritis in Africa and support any requirements for vaccine development.

Seroepidemiology of Norovirus GII.3 and GII.4 Infections in Children with Diarrhea in Xi'an, China

OBJECTIVE

The objective of this study was to investigate the seroepidemiology of immunoglobulin G (IgG) antibodies against Norovirus (NoV) GII.3 and GII.4 genotypes among children younger than 5 years with acute diarrhea in Xi'an, China.

MATERIALS AND METHODS

A total of 362 serum samples were collected from diarrheal children in the Department of Digestive Diseases of Xi'an Children's Hospital between March 2009 and October 2012. Recombinant capsid proteins of NoV genotypes GII.3 and GII.4 were expressed using the baculovirus expression system. The viruslike particles (VLPs) were examined by electron microscopy and Western blot, and VLPs were used as antigens for serological IgG tests using enzyme-linked immunosorbent assays.

RESULTS

The overall seroprevalence for GII.4 (86.2%) was significantly higher (p<0.01) than for GII.3 (67.9%). The seroprevalence remained in a high and stable level (70.9% for GII.3 and 88.7% for GII.4) in children under 1 year of age, then dropped in the age group 12-17 months (49.3% for GII.3 and 68.1% for GII.4), and finally increased to 77.8% for GII.3 and 96.8% for GII.4 in the group >18 months. The seroprevalence in the age group 12-17 months showed more statistically significant differences than the other age groups for both GII.3 and GII.4 (p<0.05).

CONCLUSIONS

In conclusion, seroprevalence of NoV GII.3 and GII.4 was high in young children in Xi'an, China, and the anti-GII.4-positive rates were statistically higher than GII.3 across all the age groups.

Genetic susceptibility to norovirus GII.3 and GII.4 infections in Chinese pediatric diarrheal disease

BACKGROUND

Noroviruses (NoVs) are a leading cause of viral diarrhea in young children. Secretor status has been confirmed to be linked with Norwalk virus (NoV GI.1) infection but there is limited information about whether secretor genotypes are associated with pediatric NoV epidemic strains in vivo.

METHODS

In this study, fecal specimens and serum samples were collected from 124 hospitalized children with acute diarrhea in Xi'an, China. TaqMan real-time reverse transcription polymerase chain reaction was used to detect NoVs in fecal samples, and NoV-positive samples were further verified using conventional reverse transcription polymerase chain reaction and sequenced. DNA was extracted from sera and TaqMan single-nucleotide polymorphism genotyping assay was applied to determine the FUT2 A385T polymorphism.

RESULTS

Only NoV GII.3 and GII.4 genotypes were found in NoV-positive samples, and NoVs were detected in 25% (15/60), 40.5% (17/42) and 9.1% (2/22) of children with homozygous secretor genotype (Se 385 Se 385), heterozygous secretor genotype (Se 385 se 385) and homozygous weak secretor genotype (se 385 se 385), respectively. Children with secretor genotypes Se 385 Se 385 and Se 385 se 385 were significantly (P < 0.05) more susceptible to combined NoV GII.3 and GII.4 infections than children with weak secretor genotype se 385 se 385.

CONCLUSIONS

These findings indicate that secretor positivity is significantly associated with GII.3 and GII.4 infections in Chinese pediatric diarrheal disease and the weak secretor phenotype does not completely protect children from GII.3 and GII.4 infections.

Exposure to human and bovine noroviruses in a birth cohort in southern India from 2002 to 2006

Human and bovine norovirus virus-like particles were used to evaluate antibodies in Indian children at ages 6 and 36 months and their mothers. Antibodies to genogroup II viruses were acquired early and were more prevalent than antibodies to genogroup I. Low levels of IgG antibodies against bovine noroviruses indicate possible zoonotic transmission.

Comparison of age-stratified seroprevalence of antibodies against norovirus GII in India and the United Kingdom

Noroviruses are a common cause of gastroenteritis worldwide, but outbreaks appear to be more common in industrialized countries than in developing countries, possibly reflecting differences in exposure and immunity. In this study, age-stratified sera from India and UK populations were analysed for the presence of norovirus-genogroup II specific IgG by a time resolved immunofluorescence assay and relative levels of antibodies in the two populations were compared. Antibody levels were higher among all age groups in India than in UK and increased with age in India, whereas in the UK, levels of antibody decreased in adulthood. These results indicate different patterns of exposure to noroviruses in the two countries.

Immunology of Norovirus Infection

Noroviruses are the leading cause of epidemic non-bacterial gastroenteritis worldwide. Despite their discovery over three decades ago, little is known about the host immune response to norovirus infection. The purpose of this chapter is to review the field of norovirus immunology and discuss the contributions of outbreak investigations, human and animal challenge studies and population-based studies. This chapter will survey both humoral and cellular immunity as well as recent advances in norovirus vaccine development.

Prevalence of enteropathogenic viruses and molecular characterization of group A rotavirus among children with diarrhea in Dar es Salaam Tanzania

Background

Different groups of viruses have been shown to be responsible for acute diarrhea among children during their first few years of life. Epidemiological knowledge of viral agents is critical for the development of effective preventive measures, including vaccines.

Methods

In this study we determined the prevalence of the four major enteropathogenic viruses – rotavirus, norovirus, adenovirus and astrovirus – was determined in 270 stool samples collected from children aged 0 – 60 months who were admitted with diarrhea in four hospitals in Dar es Salaam, Tanzania, using commercially available ELISA kits. In addition, the molecular epidemiology of group A rotavirus was investigated using reverse transcriptase multiplex polymerase chain reaction (RT-PCR).

Results

At least one viral agent was detected in 87/270 (32.2%) of the children. The prevalence of rotavirus, norovirus, adenovirus and astrovirus was 18.1%, 13.7%, 2.6% and 0.4%, respectively. In most cases (62.1%) of viruses were detected in children aged 7–12 months. The G and P types (VP7 and VP4 genotypes respectively) were further investigated in 49 rotavirus ELISA positive samples. G9 was the predominant G type (81.6%), followed by G1 (10.2%) and G3 (0.2%). P[8] was the predominant P type (83.7%), followed by P[6] (0.4%) and P[4] (0.2%). The following G and P types were not detected in this study population; G2, G4, G8 G10, P[9], P[10] and P[11]. The dominating G/P combination was G9P[8], accounting for 39 (90.7%) of the 43 fully characterized strains. Three (6.1%) of the 49 rotavirus strains could not be typed.

Conclusion

Nearly one third of children with diarrhea admitted to hospitals in Dar es Salaam had one of the four viral agents. The predominance of rotavirus serotype G9 may have implication for rotavirus vaccination in Tanzania.

Humoral immune responses against norovirus infections of children

In 2 infants with gastroenteritis associated with Norovirus (NoV), serum immunoglobulin (Ig) G, IgM, IgA, and fecal IgA antibody responses against NoV were examined by enzyme-linked immunosorbent assay using 11 different antigenic and genetic types of NoV virus-like particles expressed in insect cells. These two cases were putative primary single NoV infections, because antibodies against NoVs were not detected in acute-phase serums. In one of two cases, long-term excretion of virus RNA for 33 days was observed. Serum IgG responses demonstrated strong seroresponse to the homologous type, and weak seroresponse to the heterologous types within the genogroup. After more than 2 years, the IgG antibody titer remained high to the homologous type and low to the heterologous type within the genogroup. IgM and IgA were specific to the homologous type. IgM was short lived and the serum IgA antibody titer remained low to the homologous type for a long period. These results improve our understanding of the humoral immune response to NoV infection.

Characterisation of norovirus strains in rural Ghanaian children with acute diarrhoea

The incidence of calicivirus infection in Ghana and many other African countries is not known. Thirteen (15.9%) of the 82 diarrhoeic stool samples tested for caliciviruses were positive for noroviruses (NoVs). NoVs were present in all age groups and were detected only during the diarrhoea peak that coincided with the peak rotavirus season. Ten (76.9%) of the NoV detected were genogroup II (GII) NoVs and the remaining three (23.1%) genogroup I (GI) NoVs. The predominant GII detected was GII-4 (60%, 6/10). Three of the GII NoVs were determined to be recombinants of GII-8/GII-14 as deduced from the sequencing of the region spanning the Orf1/2 junction. The GII genotypes formed four clusters with published GII sequences. The data shown enhances understanding of NoV diversity in Ghanaian children and demonstrate the global spread of distinct common genotypes to African countries.

Detection and characterization of human caliciviruses in hospitalized children with acute gastroenteritis in Blantyre, Malawi

The human caliciviruses (HuCVs), including Norovirus and Sapovirus, are recognized causes of acute gastroenteritis in children and adults. A 1-year study was undertaken in Blantyre, Malawi, to examine the prevalence, and genetic diversity, of human caliciviruses (HuCVs) amongst children under 5 years of age hospitalized with acute gastroenteritis. Using the reverse transcription-polymerase chain reaction (RT-PCR), combined with nucleotide sequencing of the RT-PCR products, HuCVs were detected in 34/398 (8.5%) of children. Twelve (35.3%) of the children were co-infected with additional enteric viruses (predominantly rotavirus). The HuCVs comprised 26 Noroviruses (6.5%) and 8 Sapoviruses (2.0%). Each of the Noroviruses belonged to genogroup II, and could be further classified into six genotypes, including GII/3 (18 strains), GII/4 (2 strains), GII/11 (1 strain), GII/13 (1 strain), GII/16 (2 strains), and a putative new genotype GII/20 (2 strains). Each of the Sapoviruses belonged to genogroup GIII. HuCVs are the second most commonly identified viral enteropathogens (after rotavirus) among hospitalized children with gastroenteritis in Malawi.

Detection of enteric viruses in shellfish from the Norwegian coast

Common blue mussels (Mytilus edulis), horse mussels (Modiolus modiolus), and flat oysters (Ostrea edulis) obtained from various harvesting and commercial production sites along the Norwegian coast were screened for the presence of norovirus by a real-time reverse transcription (RT)-nested PCR assay and for possible indicators of fecal contamination, i.e., for F-specific RNA bacteriophages (F-RNA phages) by plaque assay and for human adenoviruses and human circoviruses by nested PCR assay. The aims were to obtain relevant information for assessing the risk of transmission of enteric viruses by shellfish and to investigate the potential of various indicator viruses in routine screening. Noroviruses were detected in 6.8% of the samples, and the indicators were detected in 23.8% (F-RNA phages), 18.6% (adenoviruses), and 8.0% (circoviruses) of the samples. A seasonal variation was observed, with the exception of circoviruses, with more positive samples in the winter. A positive correlation was found between F-RNA phages and noroviruses. However, F-RNA phages were present in only 43% of the norovirus-positive samples. The results show that mussels from the Norwegian coast can constitute a risk of infection with enteric viruses and that routine testing of samples may be justified. Advantages and disadvantages of various options for screening are discussed.

Molecular epidemiology of caliciviruses causing outbreaks and sporadic cases of acute gastroenteritis in Spain

The molecular epidemiology of human caliciviruses (HuCVs) causing sporadic cases and outbreaks of acute gastroenteritis around eastern Spain (Catalonia and the Valencian Community) was studied by reverse transcription-PCR (RT-PCR) and by sequencing part of the RNA polymerase gene in open reading frame 1. HuCVs were detected in 44 of 310 stool specimens (14.19%) negative for other enteric pathogens obtained from children with acute gastroenteritis. Norwalk-like viruses (NLVs) were the most common cause of the gastroenteritis outbreaks investigated here. They were detected in 14 out of 25 (56%) outbreaks with an identified pathogen. Genotypes producing both sporadic cases and outbreaks were diverse, with a predominance of GGII strains related to genotypes Melksham and Lordsdale. Five strains clustered with a "new variant" designated GGIIb, which was detected circulating throughout quite a few European countries in the years 2000 and 2001. The emergence mechanism of these strains might be the occurrence of intertypic recombinations between different viruses. The nucleotide sequence of part of the capsid gene (ORF2) from three of these strains demonstrated their relationship with Mexico virus.

Human caliciviruses in Europe

Caliciviruses are single-stranded RNA viruses, which are divided into four genera based on their morphology and genomic structure. Viruses from two genera, the Norwalk like viruses and Sapporo like viruses, are a common cause of acute, nonbacterial gastroenteritis in humans. Although the first human calicivirus discovered nearly 30 years ago, much of the epidemiological and biological character of these viruses is only now beginning to unfold. Investigation has been difficult due to a number of factors, the viruses cannot be amplified by in vitro cell culture or animal models and electron microscopy (EM) is often not sensitive enough to detect the viruses in stool samples. Recent advances in molecular diagnostic techniques and the advent of a baculovirus expression system have highlighted the clinical and public health importance of calicivirus in all age groups, their ability to cause infection via a number of transmission routes as well as their considerable genetic diversity. These characteristics, in conjunction with the inability of humans to develop long-term immunity make HuCV an important public health issue in Europe and worldwide.

Diagnosis of noncultivatable gastroenteritis viruses, the human caliciviruses

Gastroenteritis is one of the most common illnesses of humans, and many different viruses have been causally associated with this disease. Of those enteric viruses that have been established as etiologic agents of gastroenteritis, only the human caliciviruses cannot be cultivated in vitro. The cloning of Norwalk virus and subsequently of other human caliciviruses has led to the development of several new diagnostic assays. Antigen detection enzyme immunoassays (EIAs) using polyclonal hyperimmune animal sera and antibody detection EIAs using recombinant virus-like particles have supplanted the use of human-derived reagents, but the use of these assays has been restricted to research laboratories. Reverse transcription-PCR assays for the detection of human caliciviruses are more widely available, and these assays have been used to identify virus in clinical specimens as well as in food, water, and other environmental samples. The application of these newer assays has significantly increased the recognition of the importance of human caliciviruses as causes of sporadic and outbreak-associated gastroenteritis.