Erwin de Bruin

Natural History of Human Calicivirus Infection: A Prospective Cohort Study

We investigated the natural history of human Calicivirus infection in the community. Clinical information was obtained from 99 subjects infected with Norwalk-like viruses (NLV) and 40 subjects infected with Sapporo-like viruses (SLV) in a prospective, community-based cohort study. NLV infection was common in all age groups, whereas SLV infection was mainly restricted to children aged <5 years. Symptoms lasted for a median of 5 and 6 days for NLV and SLV infections, respectively. Disease was characterized by diarrhea during the first 5 days (87% of patients with NLV infection and 95% of patients with SLV infection) and vomiting on the first day (74% for NLV and 60% for SLV). Vomiting was less common in children aged <1 year (59% for NLV and 44% for SLV) than it was among children aged >/=1 year (>75% for NLV and >67% for SLV). Overall, NLV was detected in 26% of patients up to 3 weeks after the onset of illness. This proportion was highest (38%) for children aged <1 year. SLV shedding subsided after 14 days. These data show that the durations of disease and viral shedding of caliciviruses are longer than has been described elsewhere. Therefore, the impact of these infections may have been underestimated.

Epochal Evolution of GGII.4 Norovirus Capsid Proteins from 1995 to 2006

ABSTRACT Noroviruses are the causative agents of the majority of viral gastroenteritis outbreaks in humans. During the past 15 years, noroviruses of genotype GGII.4 have caused four epidemic seasons of viral gastroenteritis, during which four novel variants (termed epidemic variants) emerged and displaced the resident viruses. In order to understand the mechanisms and biological advantages of these epidemic variants, we studied the genetic changes in the capsid proteins of GGII.4 strains over this period. A representative sample was drawn from 574 GGII.4 outbreak strains collected over 15 years of systematic surveillance in The Netherlands, and capsid genes were sequenced for a total of 26 strains. The three-dimensional structure was predicted by homology modeling, using the Norwalk virus (Hu/NoV/GGI.1/Norwalk/1968/US) capsid as a reference. The highly significant preferential accumulation and fixation of mutations (nucleotide and amino acid) in the protruding part of the capsid protein provided strong evidence for the occurrence of genetic drift and selection. Although subsequent new epidemic variants differed by up to 25 amino acid mutations, consistent changes were observed in only five positions. Phylogenetic analyses showed that each variant descended from its chronologic predecessor, with the exception of the 2006b variant, which is more closely related to the 2002 variant than to the 2004 variant. The consistent association between the observed genetic findings and changes in epidemiology leads to the conclusion that population immunity plays a role in the epochal evolution of GGII.4 norovirus strains.

Etiological role of viruses in outbreaks of acute gastroenteritis in The Netherlands from 1994 through 2005.

ABSTRACT Acute gastroenteritis is one of the most common diseases worldwide. In developed countries, viruses, particularly noroviruses, are recognized as the leading cause. In The Netherlands, the surveillance of gastroenteritis outbreaks with suspected viral etiologies (as determined by Kaplan criteria) was established by the National Institute for Public Health and the Environment in 1994. This paper presents an overview of viral gastroenteritis outbreaks reported from 1994 through 2005. A minimum epidemiological data set consisting of the associated setting(s), the probable transmission mode, the date of the first illness and the date of sampling, the number of persons affected, and the number of hospitalizations was requested for each reported outbreak. Stool samples were tested for the presence of norovirus, sapovirus, rotavirus, astrovirus, adenovirus, and Aichi virus by electron microscopy, enzyme-linked immunosorbent assay, and/or reverse transcription-PCR. A total of 6,707 stool samples from 941 gastroenteritis outbreaks were investigated. Noroviruses were detected as the causative agent in 735 (78.1%) of the outbreaks, and rotaviruses, adenoviruses, and astroviruses were found to be responsible for 46 (4.9%), 9 (1.0%), and 5 (0.5%) outbreaks, respectively. Among the gastroenteritis outbreaks in which a mode of transmission was identified, most outbreaks (38.1%) were associated with person-to-person transmission, and the majority (54.9%) of the outbreaks investigated were reported by residential institutions. Since 2002, the total number of outbreaks reported and the number of unexplained outbreaks have increased. Furthermore, the number of rotavirus-associated outbreaks has increased, especially in nursing homes. Despite thorough testing, 115 (12.2%) outbreaks suspected of having viral etiologies remain unexplained. Increases in numbers of reported outbreaks may indicate undefined changes in the criteria for reporting or the emergence of new pathogens.

International Collaborative Study To Compare Reverse Transcriptase PCR Assays for Detection and Genotyping of Noroviruses

ABSTRACT To allow more rapid and internationally standardized assessment of the spread of noroviruses (previously called Norwalk-like viruses [NLVs]) as important food-borne pathogens, harmonization of methods for their detection is needed. Diagnosis of NLVs in clinical diagnostic laboratories is usually performed by reverse transciptase PCR (RT-PCR) assays. In the present study, the performance of five different RT-PCR assays for the detection of NLVs was evaluated in an international collaborative study by five laboratories in five countries with a coded panel of 91 fecal specimens. The assays were tested for their sensitivity, detection limit, and ease of standardization. In total, NLVs could be detected by at least one RT-PCR assay in 69 (84%) of the samples that originally tested positive. Sensitivity ranged from 52 to 73% overall and from 54 to 100% and 58 to 85% for genogroup I and II viruses, respectively. In all, 64% of the false-negative results were obtained with a set of diluted stools (n = 20) that may have lost quality upon storage. Sensitivity was improved when these samples were excluded from analysis. No one single assay stood out as the best, although the p1 assay demonstrated the most satisfactory overall performance. To promote comparability of data, this assay will be recommended for newly starting groups in future collaborative studies.

Prevalence of Human Parechovirus in The Netherlands in 2000 to 2007

ABSTRACT Infection with human parechovirus 3 (HPeV3) was described for the first time in Japan in 2004 and reportedly is more often associated with severe disease than infection with HPeV1 or HPeV2. In 2004, infections with HPeV3 were observed for the first time in The Netherlands. Genetic analysis showed several different lineages, suggesting endemic circulation. We analyzed 163 cell culture isolates from the same number of patients tested in routine virological laboratories as part of the national enterovirus surveillance program. Isolates were collected between 2000 and 2007 and could not be characterized by routine methods. In total, 155 isolates (95%) were found positive for HPeV by a reverse transcription-PCR assay targeting the 5′ untranslated region, explaining the majority of the diagnostic deficit in enterovirus surveillance for these years. Typing of the isolates by use of partial genome sequencing of the VP1/2A region revealed the presence of 55 HPeV1, 2 HPeV2, 89 HPeV3, 1 HPeV4, and 8 HPeV5 isolates. We compared isolation dates, age groups affected, and clinical pictures, which were reported as part of the routine surveillance. Clear differences in epidemiology were observed, with HPeV3 occurring at intervals of 2 years and in the spring-summer season, whereas HPeV1 was observed in small numbers throughout each year, with a low in the summer months. HPeV3 infection affected younger children than HPeV1 infection and was significantly more often associated with fever, meningitis, and viremia.

European Multicenter Evaluation of Commercial Enzyme Immunoassays for Detecting Norovirus Antigen in Fecal Samples

ABSTRACT A total of 2,254 fecal samples were tested in a European multicenter evaluation of commercially available norovirus antigen detection assays. Two commercial enzyme immunoassays, IDEIA Norovirus (Oxoid; Thermo Fisher Scientific, Ely, United Kingdom) and RIDASCREEN Norovirus (R-Biopharm, Darmstadt, Germany), were included in the evaluation, and their performance was compared with the results of reverse transcription-PCR (RT-PCR). Included in the evaluation were samples collected in sporadic cases of gastroenteritis, samples from outbreaks in which two or more samples were collected, well-characterized samples representing genotypes currently cocirculating within Europe, and samples collected from patients with gastroenteritis caused by a pathogen other than norovirus. The sensitivities and specificities of the IDEIA Norovirus and RIDASCREEN Norovirus assays were 58.93 and 43.81% and 93.91 and 96.37%, respectively, compared with RT-PCR. The sensitivities of both assays for outbreak investigations improved when six or more samples from an outbreak were examined. The IDEIA Norovirus assay exhibited reactivity to a broader range of norovirus genotypes than the RIDASCREEN Norovirus assay, which showed genotype-dependent sensitivities. The results indicate that, if used, these assays should serve as screening assays and the results should be confirmed by RT-PCR.

Glycan-Dependent Immunogenicity of Recombinant Soluble Trimeric Hemagglutinin

ABSTRACT Recombinant soluble trimeric influenza A virus (IAV) hemagglutinin (sHA3) has proven an effective vaccine antigen against IAV. Here, we investigate to what extent the glycosylation status of the sHA3 glycoprotein affects its immunogenicity. Different glycosylation forms of subtype H5 trimeric HA protein (sH53) were produced by expression in insect cells and different mammalian cells in the absence and presence of inhibitors of N-glycan-modifying enzymes or by enzymatic removal of the oligosaccharides. The following sH53 preparations were evaluated: (i) HA proteins carrying complex glycans produced in HEK293T cells; (ii) HA proteins carrying Man9GlcNAc2 moieties, expressed in HEK293T cells treated with kifunensine; (iii) HA proteins containing Man5GlcNAc2 moieties derived from HEK293S GnTI(−) cells; (iv) insect cell-produced HA proteins carrying paucimannosidic N-glycans; and (v) HEK293S GnTI(−) cell-produced HA proteins treated with endoglycosidase H, thus carrying side chains composed of only a single N-acetylglucosamine each. The different HA glycosylation states were confirmed by comparative electrophoretic analysis and by mass spectrometric analysis of released glycans. The immunogenicity of the HA preparations was studied in chickens and mice. The results demonstrate that HA proteins carrying terminal mannose moieties induce significantly lower hemagglutination inhibition antibody titers than HA proteins carrying complex glycans or single N-acetylglucosamine side chains. However, the glycosylation state of the HA proteins did not affect the breadth of the antibody response as measured by an HA1 antigen microarray. We conclude that the glycosylation state of recombinant antigens is a factor of significant importance when developing glycoprotein-based vaccines, such as recombinant HA proteins.

Population-Level Antibody Estimates to Novel Influenza A/H7N9

Abstract There are no contemporary data available describing human immunity to novel influenza A/H7N9. Using 1723 prospectively collected serum samples in southern Vietnam, we tested for antibodies to 5 avian influenza virus antigens, using a protein microarray. General-population antibody titers against subtype H7 virus are higher than antibody titers against subtype H5 and lower than titers against H9. The highest titers were observed for human influenza virus subtypes. Titers to avian influenza virus antigens increased with age and with geometric mean antibody titer to human influenza virus antigens. There were no titer differences between the urban and the rural location in our study.

Profiling of humoral response to influenza A(H1N1)pdm09 infection and vaccination measured by a protein microarray in persons with and without history of seasonal vaccination

Background The influence of prior seasonal influenza vaccination on the antibody response produced by natural infection or vaccination is not well understood. Methods We compared the profiles of antibody responses of 32 naturally infected subjects and 98 subjects vaccinated with a 2009 influenza A(H1N1) monovalent MF59-adjuvanted vaccine (Focetria®, Novartis), with and without a history of seasonal influenza vaccination. Antibodies were measured by hemagglutination inhibition (HI) assay for influenza A(H1N1)pdm09 and by protein microarray (PA) using the HA1 subunit for seven recent and historic H1, H2 and H3 influenza viruses, and three avian influenza viruses. Serum samples for the infection group were taken at the moment of collection of the diagnostic sample, 10 days and 30 days after onset of influenza symptoms. For the vaccination group, samples were drawn at baseline, 3 weeks after the first vaccination and 5 weeks after the second vaccination. Results We showed that subjects with a history of seasonal vaccination generally exhibited higher baseline titers for the various HA1 antigens than subjects without a seasonal vaccination history. Infection and pandemic influenza vaccination responses in persons with a history of seasonal vaccination were skewed towards historic antigens. Conclusions Seasonal vaccination is of significant influence on the antibody response to subsequent infection and vaccination, and further research is needed to understand the effect of annual vaccination on protective immunity.

MERS-CoV Infection of Alpaca in a Region Where MERS-CoV is Endemic

To the Editor: Accumulating evidence indicates that dromedaries (Camelus dromedarius) are a reservoir for zoonotic transmission of Middle East respiratory syndrome coronavirus (MERS-CoV). Although numerous studies have looked at other livestock in the Middle East region, evidence for MERS-CoV infection has only been found in dromedaries (1). Extensive and continuous circulation of MERS-CoV occurs in the Al Shahaniya region of Qatar, most likely because of the presence of an international camel racing track and numerous barns holding camels (2,3). In April 2015, we investigated the MERS-CoV infection status of 15 healthy alpacas (Vicugna pacos) in a herd of 20 animals and 10 healthy dromedaries in a herd of 25 animals at a farm in this region (Technical Appendix). The herds were located at a distance of ≈200 m from each other within the barn complex and were cared for by the same animal workers, who lived in a common house between the herds at the complex. Both the alpacas and camels were kept as hobby animals. Serum samples were collected from all 25 animals. Nasal swabs were collected from all camels, whereas nasal, rectal, and oral swab specimens were collected only from a subset of the alpacas (Technical Appendix) because of logistical constraints. The serum samples were tested for IgG antibodies reactive with the S1 antigens of MERS-CoV and severe acute respiratory syndrome coronavirus (SARS-CoV), and titers were calculated as described previously (4,5). MERS-CoV reactivity was confirmed by using a 90% plaque-reduction neutralization test (PRNT90) (3). Swab specimens were analyzed for MERS-CoV RNA by a screening PCR targeting the upE gene (6). MERS-CoV–specific antibodies were detected in all alpacas and all but 1 camel by protein microarray; reciprocal titers ranged from 49 to 773 for the alpacas and were >1,280 for the camels (Figure, panel A). PRNT90 testing confirmed the presence of MERS-CoV–specific antibodies; reciprocal neutralizing titers ranged from 80 to 320 for the alpacas and from 80 to >2,560 for 9 camels (Figure, panel B). All swab specimens were negative by PCR (Technical Appendix). None of the serum samples were reactive to SARS-CoV S1. The microarray was also conducted for bovine CoV and human CoV-229E antigens, which were used as a proxy for the serologically closely related dromedary betacoronavirus-1 HKU23 and 229E-related camelid alphacoronaviruses, respectively (7). Positive binding was detected for both antigens in alpaca and dromedary (data not shown). Figure Column scatterplots of MERS-CoV reactivity of serum samples from alpaca (n = 15) and dromedaries (n = 10) in the Al Shahaniya region of Qatar, April 2015. A) Plot of alpaca and dromedary serum titers of antibodies specific for S1 antigens of 2 coronaviruses ... Our observations prove the susceptibility of alpacas for natural MERS-CoV infection and lay the foundation for future studies to determine the potential of alpacas as another livestock reservoir for MERS-CoV. The alpacas in this study were the only alpacas in Qatar at the time and were located in a region where MERS-CoV is endemic. In a previous study, by using the same microarray technology, we found no evidence for MERS-CoV infection in alpacas from regions where MERS-CoV is not endemic (4). Although a study by Eckerle et al. demonstrated the potential of MERS-CoV to infect alpaca kidney cells in vitro (8) and alignment of mammalian DPP4 indicate that the 14 residues interacting with the MERS-CoV receptor binding domain of alpaca DPP4 are identical to that of dromedary DPP4 (Technical Appendix), the in vivo susceptibility of alpacas remained to be determined. The observed natural susceptibility of alpacas to MERS-CoV infection potentiates a broadening of the geographic range of MERS-CoV circulation to areas with large populations of alpacas. Alpacas are New World camelids, and the worldwide population of alpacas is estimated at 3 million animals, with ≈94% living in the high Andean regions of South America (Peru, Bolivia, Chile and Argentina), of which most are in Peru (constituting ≈88% of the world alpaca population) (http://lib.icimod.org/record/23682). Alpacas are increasingly being kept outside South America, mainly for their fleece, with estimated numbers in 2014 reaching 230,000 in the United States (http://lib.icimod.org/record/23682), 35,000 in the United Kingdom (http://www.bas-uk.com), and 150,000 in Australia (http://www.alpaca.asn.au). Although MERS-CoV has not been found in camelids other than dromedaries outside the Arabian Peninsula so far (9), our observations raise the question of whether other camelids could become infected if MERS-CoV were introduced to regions with large populations of alpacas and possibly other closely related camelids of the genera Lama, Vicugna, and Camelus. Because the date of infection of the alpacas and camels in this study is not known, we cannot speculate on the level of susceptibility of alpacas versus dromedaries based on the observed differences in antibody titers, which were lower in alpacas. It remains to be determined whether alpacas, in parallel with dromedaries, will actually shed MERS-CoV and are capable of independent maintenance of the virus in their population. Differences in susceptibility to viral pathogens between New and Old World camelids have been observed before (10). Therefore, understanding the risk requires further assessment of the reservoir competence of alpacas for MERS-CoV (e.g., through experimental infections) and an assessment of MERS-CoV–related viruses present in alpacas and other camelids in different parts of the world. Technical Appendix. Overview of background data and study results of alpaca and dromedary cohorts. Click here to view.(394K, pdf)