GloPID-R report on chikungunya, o'nyong-nyong and Mayaro virus, part 2: Epidemiological distribution of o'nyong-nyong virus

The GloPID-R (Global Research Collaboration for Infectious Disease Preparedness) chikungunya (CHIKV), o'nyong-nyong (ONNV) and Mayaro virus (MAYV) Working Group has been established to identify gaps of knowledge about the natural history, epidemiology and medical management of infection by these viruses, and to provide adapted recommendations for future investigations. Here, we present a report dedicated to ONNV epidemiological distribution. Two large-scale ONNV outbreaks have been identified in Africa in the last 60 years, interspersed with sporadic serosurveys and case reports of returning travelers. The assessment of the real scale of ONNV circulation in Africa remains a difficult task and surveillance studies are necessary to fill this gap. The identification of ONNV etiology is made complicated by the absence of multiplex tools in co-circulation areas and that of reference standards, as well as the high cross-reactivity with related pathogens observed in serological tests, in particular with CHIKV. This is a specific obstacle for seroprevalence studies, that necessitate an improvement of serological tools to provide robust results. The scarcity of existent genetic data currently limits molecular epidemiology studies. ONNV epidemiology would also benefit from reinforced entomological and environmental surveillance. Finally, the natural history of the disease deserves to be further investigated, with a specific attention paid to long-term complications. Considering our incomplete knowledge on ONNV distribution, GloPID-R CHIKV, ONNV and MAYV experts recommend that a major effort should be done to fill existing gaps.

Laboratory preparedness and response with a focus on arboviruses in Europe

BACKGROUND

The global health burden of arboviruses is continuously rising, which results in increasing pressure on local and (inter)national laboratory infrastructures. Timely and accurate diagnosis of cases is one of the main pillars for public health and clinical responses to an arbovirus emergence.

AIMS AND SOURCES

This narrative review aims to summarize recent advances and to identify needs in laboratory preparedness and response activities, with a focus on viruses transmitted by arthropods in Europe. The review is based on evidence extracted from PubMed searches, Public Health and clinical laboratory experiences from the authors and the authors' opinions substantiated by peer-reviewed scientific literature.

CONTENT

We illustrate the importance of inter-epidemic laboratory preparedness activities to ensure adequate Public Health and clinical responses. We describe the status of arbovirus endemicity and emergence in Europe thereby highlighting the need for preparedness for these viruses. We discuss the components and pitfalls of an adequate laboratory preparedness and response and the broader context of the current landscape of international research, clinical and laboratory preparedness networks. The complexity of arbovirus laboratory preparedness and response is described.

IMPLICATIONS

Outbreak preparedness plans need to look beyond national reference laboratories, to include first-line responding onsite hospital laboratories and plans for strengthening of such local capacity and capability as required depending on the nature of the outbreak. In particular, the diagnosis of arbovirus infections is complicated by the existence of geographic overlap of circulation of numerous arboviruses, the overlap in clinical manifestation between many arboviruses and other aetiologies and the existence of cross-reactivity between related arboviruses in serology testing. Inter-epidemic preparedness activities need strong national and international networks addressing these issues. However, the current mushrooming of European preparedness networks requires governance to bring the European preparedness and response to a next level.

The hanta hunting study: underdiagnosis of Puumala hantavirus infections in symptomatic non-travelling leptospirosis-suspected patients in the Netherlands, in 2010 and April to November 2011

Leptospirosis and haemorrhagic fever with renal syndrome (HFRS) are hard to distinguish clinically since these two important rodent-borne zoonoses share hallmark symptoms such as renal failure and haemorrhage. Leptospirosis is caused by infection with a spirochete while HFRS is the result of an infection with certain hantaviruses. Both diseases are relatively rare in the Netherlands. Increased incidence of HFRS has been observed since 2007 in countries that border the Netherlands. Since a similar rise in incidence has not been registered in the Netherlands, we hypothesise that due to overlapping clinical manifestations, hantavirus infections may be confused with leptospirosis, leading to underdiagnosis. Therefore, we tested a cohort of non-travelling Dutch patients with symptoms compatible with leptospirosis, but with a negative diagnosis, during 2010 and from April to November 2011. Sera were screened with pan-hantavirus IgG and IgM enzyme-linked immunosorbent assays (ELISAs). Sera with IgM reactivity were tested by immunofluorescence assay (IFA). ELISA (IgM positive) and IFA results were confirmed using focus reduction neutralisation tests (FRNTs). We found hantavirus-specific IgG and/or IgM antibodies in 4.3% (11/255) of samples taken in 2010 and in 4.1% (6/146) of the samples during the 2011 period. After FRNT confirmation, seven patients were classed as having acute Puumala virus infections. A review of hantavirus diagnostic requests revealed that at least three of the seven confirmed acute cases as well as seven probable acute cases of hantavirus infection were missed in the Netherlands during the study period.

Middle East respiratory syndrome coronavirus (MERS-CoV) RNA and neutralising antibodies in milk collected according to local customs from dromedary camels, Qatar, April 2014

Antibodies to Middle East respiratory syndrome coronavirus (MERS-CoV) were detected in serum and milk collected according to local customs from 33 camels in Qatar, April 2014. At one location, evidence for active virus shedding in nasal secretions and/or faeces was observed for 7/12 camels; viral RNA was detected in milk of five of these seven camels. The presence of MERS-CoV RNA in milk of camels actively shedding the virus warrants measures to prevent putative food-borne transmission of MERS-CoV.

Middle East Respiratory Syndrome coronavirus (MERS-CoV) serology in major livestock species in an affected region in Jordan, June to September 2013

Between June and September 2013, sera from 11 dromedary camels, 150 goats, 126 sheep and 91 cows were collected in Jordan, where the first human Middle-East respiratory syndrome (MERS) cluster appeared in 2012. All sera were tested for MERS-coronavirus (MERS-CoV) specific antibodies by protein microarray with confirmation by virus neutralisation. Neutralising antibodies were found in all camel sera while sera from goats and cattle tested negative. Although six sheep sera reacted with MERS-CoV antigen, neutralising antibodies were not detected.

Replication of alfalfa mosaic virus RNA 3 with movement and coat protein genes replaced by corresponding genes of Prunus necrotic ringspot ilarvirus

Alfalfa mosaic virus (AMV) and Prunus necrotic ringspot virus (PNRSV) are tripartite positive-strand RNA plant viruses that encode functionally similar translation products. Although the two viruses are phylogenetically closely related, they infect a very different range of natural hosts. The coat protein (CP) gene, the movement protein (MP) gene or both genes in AMV RNA 3 were replaced by the corresponding genes of PNRSV. The chimeric viruses were tested for heterologous encapsidation, replication in protoplasts from plants transformed with AMV replicase genes P1 and P2 (P12 plants) and for cell-to-cell transport in P12 plants. The chimeric viruses exhibited basic competence for encapsidation and replication in P12 protoplasts and for a low level of cell-to-cell movement in P12 plants. The potential involvement of the MP gene in determining host specificity in ilarviruses is discussed.

Mutations in coat protein binding sites of alfalfa mosaic virus RNA 3 affect subgenomic RNA 4 accumulation and encapsidation of viral RNAs

The 3'-untranslated regions (3'-UTRs) of the three RNAs of alfalfa mosaic virus (AMV) contain a specific binding site for coat protein (CP) and act as a promoter for minus-strand RNA synthesis by the purified AMV RNA-dependent RNA polymerase (RdRp) in an in vitro assay. Binding of CP to the viral RNAs is required to initiate infection. The sequence of the 3'-terminal 39 nucleotides of AMV RNA 3 can be folded into two stem-loop structures flanked by three single-stranded AUGC sequences and represents a CP binding site. Mutations in this sequence that are known to interfere with CP binding in vitro were introduced into an infectious clone of RNA 3, and mutant RNA transcripts were used as templates in the in vitro RdRp assay and to infect protoplasts and plants. Mutation of AUGC motif 2 or disruption of the stem of the 3'-proximal hairpin 1 interfered with CP binding in vitro but not with minus-strand promoter activity in vitro or replication of RNA 3 in vivo. However, hairpin 1 appeared to be essential for encapsidation of RNA 3. Reversion of three G-C base pairs in hairpin 1 had no effect on CP binding but interfered with minus-strand promoter activity in vitro and with RNA 3 replication in vivo. It is concluded that the viral RdRp and CP recognize different elements in the 3'-UTRs of AMV RNAs. Moreover, several mutations that interfered with CP binding in vitro interfered with the accumulation in vivo of RNA 4, the subgenomic messenger for CP, but not with the accumulation of RNA 3.

The 3' untranslated region of alfalfa mosaic virus RNA3 contains a core promoter for minus-strand RNA synthesis and an enhancer element

The 3' untranslated regions (UTRs) of the three genomic RNAs of alfalfa mosaic virus consist of a 3' homologous sequence of 145 nt and upstream unique sequences 18-34 nt in length. Mutations were made in the 3' UTR of a cDNA clone of RNA3. Point mutations in five AUGC motifs which interfere with specific binding of coat protein to the 3' UTR had no effect on template activity of RNA3 for minus-strand RNA synthesis in vitro by purified viral RNA-dependent RNA polymerase (RdRp). Deletion analysis showed that the 3' homologous sequence of 145 nt was sufficient for a low level of template activity in the in vitro RdRp assay and a similarly low level of RNA3 accumulation in plants. The presence of an additional sequence of nucleotides 145-165 from the 3' end of RNA3 enhanced template recognition by RdRp in vitro and accumulation of RNA3 in vivo to wild-type levels.

Structural elements of the 3'-terminal coat protein binding site in alfalfa mosaic virus RNAs

The 3'-terminal of the three genomic RNAs of alfalfa mosaic virus (AIMV) and ilarviruses contain a number of AUGC-motifs separated by hairpin structures. Binding of coat protein (CP) to such elements in the RNAs is required to initiate infection of these viruses. Determinants for CP binding in the 3'-terminal 39 nucleotides (nt) of AIMV RNA 3 were analyzed by band-shift assays. From the 5'- to 3'-end this 39 nt sequence contains AUGC-motif 3, stem-loop structure 2 (STLP2), AUGC-motif 2, stem-loop structure 1 (STLP1) and AUGC-motif 1. A mutational analysis showed that all three AUGC-motifs were involved in CP binding. Mutation of the A- and U-residues of motifs 1 or 3 had no effect on CP binding but similar mutations in motif 2 abolished CP binding. A mutational analysis of the stem of STLP1 and STLP2 confirmed the importance of these hairpins for CP binding. Randomization of the sequence of the stems and loops of STLP1 and STLP2 had no effect on CP binding as long as the secondary structure was maintained. This indicates that the two hairpins are not involved in sequence-specific interactions with CP. They may function in a secondary structure-specific interaction with CP and/or in the assembly of the AUGC-motifs in a configuration required for CP binding.

cis-preferential stimulation of alfalfa mosaic virus RNA 3 accumulation by the viral coat protein

RNA 3 of alfalfa mosaic virus (AIMV) encodes the movement protein P3 and the viral coat protein (CP) which is translated from the subgenomic RNA 4. RNA 3 is able to replicate in tobacco plants transformed with the AIMV replicase genes P1 and P2 (P12 plants). Frameshifts or deletions in the P3 gene have little effect on RNA 3 accumulation in P12 protoplasts whereas such mutations in the CP gene result in a 100-fold reduction of plus-strand RNA 3 accumulation. When P12 protoplasts were inoculated with a mixture of a RNA 3 mutant with a deletion in the P3 gene and a mutant with a deletion in the CP gene, CP expressed by the P3 mutant was unable to upregulate plus-strand RNA accumulation of the CP mutant. However, when a wild-type CP gene and subgenomic promoter were inserted in a RNA 3 mutant with a defective CP gene, the mutant accumulated at wild-type levels. It is concluded that the function of CP in plus-strand RNA 3 accumulation acts in cis and cannot be complemented in trans. In P12 plants, P3 and CP mutants were able to complement each other at low and variable levels. This complementation in plants appeared to be correlated with the occurrence of recombination to wild-type RNA 3.

Ability of tobacco streak virus coat protein to substitute for late functions of alfalfa mosaic virus coat protein

The coat protein (CP) of tobacco streak virus (TSV) can substitute for the early function of alfalfa mosaic virus (AIMV) CP in genome activation. Replacement of the CP gene in AIMV RNA 3 with the TSV CP gene and analysis of the replication of the chimeric RNA indicated that the TSV CP could not substitute for the function of AIMV CP in asymmetric plus-strand RNA accumulation but could encapsidate the chimeric RNA and permitted a low level of cell-to-cell transport.

Specificity of baculovirus p10 functions

Three functional domains in baculovirus p10 proteins have been postulated for aggregation, nuclear disintegration, and fibrillar structure formation (Van Oers et al., J. Gen. Virol. 74, 563-574, 1993). To study the specificity of these functions, a recombinant Autographa californica nuclear polyhedrosis virus (AcCR1) was constructed in which the coding sequence of the p10 gene was replaced with the p10 sequence of the distantly related Spodoptera exigua (Se) MNPV. In AcCR1-infected cells the SeMNPV p10 protein was produced at similarly high levels as AcMNPV p10 in wild type (wt) AcMNPV infections. Formation of fibrillar structures occurred in a similar fashion in SeMNPV and AcCR1-infected cells. Hence, the SeMNPV p10 protein retained the ability to associate into fibrillar structures when expressed in an otherwise AcMNPV context. Mixed infection with wt AcMNPV and AcCR1 indicated that only p10 proteins of the same species aggregate and that these aggregates associate into fibrillar structures. In contrast to S. exigua cells infected with AcMNPV or SeMNPV, S. exigua cells infected with AcCR1 failed to release polyhedra. This result indicated that interaction of p10 with at least one virus-specific factor is required for nuclear disintegration.

The 3'-untranslated region of alfalfa mosaic virus RNA 3 contains at least two independent binding sites for viral coat protein

The 3'-termini of the three genomic RNAs of alfalfa mosaic virus contain a common sequence of 145 nucleotides (nt) with a specific binding site for coat protein (CP). This sequence consists of several stem/loop structures interspersed with single-stranded AUGC-motifs; in RNA 3 this folding pattern is extended to a region upstream of the homologous sequence. By band-shift assays a minimum of two specific binding sites for CP were identified near the 3'-end of RNA 3. Site 1 consists of the region between nt 11 and 127 from the 3'-end and contains two AUGC-motifs. Site 2 is located between nt 133 and 208 from the 3'-end in a sequence that is largely unique to RNA 3 and contains also two AUGC-motifs. Deletion studies revealed that the two sites could bind CP independently of each other and permitted the identification of sequence elements that are essential for the activity of each site. By site-directed mutagenesis it was shown that the AUGC-motifs are important for binding of CP to both sites. These binding sites may play a role in the phenomenon that each genomic RNA has to be complexed with a few CP molecules to initiate infection. Later in the replication cycle they may act as origins for the assembly of virus particles.

Functional domains of the p10 protein of Autographa californica nuclear polyhedrosis virus

Distinct functional domains in the Autographa californica nuclear polyhedrosis virus p10 protein were identified by analysis of p10 mutants. When up to 15 amino acids from the carboxy terminus were deleted, truncated p10 proteins were found in both the nucleus and the cytoplasm of infected cells, but formed no fibrillar structures. This suggested that the positively charged carboxy terminus is not required for nuclear or cytoplasmic localization of p10 protein, but is involved in protein-protein interactions leading to assembly of the p10 protein into fibrillar structures. Absence of the p10 protein prevented the release of polyhedra from infected cells, caused by impaired nuclear disintegration. This function of the p10 protein appears to be located between amino acid residues 52 and 79. The amino-terminal half of the p10 protein has already been implicated in the self-aggregation of this protein. Thus fibrillar structure formation, nuclear disintegration and intermolecular p10 protein interactions seem to be three separate functions of the p10 protein and these functions are located in distinct domains of the protein. The mutants expressing truncated p10 proteins were impaired in electron-dense spacer formation but polyhedron envelopes were still formed. This result suggested that the formation of electron-dense spacers is not a prerequisite for the formation of polyhedron envelopes.