Caution in interpretation of SARS-CoV-2 quantification based on RT-PCR cycle threshold value.

RT-PCR is the reference method for diagnosis of a Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) infection. During the setting up of 6 SARS-CoV-2 RT-PCR assays in our laboratory, comparative evaluations were systematically undertaken and allowed to evidence major discrepancies on cycle threshold RT-PCR results between techniques. These tendencies were confirmed in routine application when analyzing sequential samples from the same patients. Our aim was to examine the impact of the technique among factors influencing RT-PCR result, a far surrogate of 'viral load' in the heterogeneous environment of respiratory specimens.

Prevalence of herpesviruses at onset of idiopathic nephrotic syndrome.

BACKGROUND: Idiopathic nephrotic syndrome (INS) is likely a primary immune disorder, but viruses might also be involved in the mechanisms of the disease. Here, we investigate the link between herpesvirus infection and the first manifestation of INS in children. METHODS: A prospective, multicentre, and population-based case-control study called NEPHROVIR included 164 patients, aged 6 months to 15 years old, newly diagnosed with INS, and 233 controls matched for gender, age, and period of sample. The analysis was done on 124 patients and 196 controls. Epstein-Barr virus (EBV), cytomegalovirus (CMV), human herpesvirus-6 (HHV-6), and human herpesvirus-7 (HHV-7) DNA prevalence at diagnosis were assessed from whole peripheral blood samples, as well as EBV and CMV viral load and seroprevalence. RESULTS: EBV DNA was significantly more prevalent in cases than in controls (50.8 vs 29.1 %; OR = 2.6; p = 0.0002), with no difference in viral load. A significant difference was also found for CMV (11.3 vs 3.6 %; p = 0.02) and HHV-7 (83 vs 72 %; p = 0.02) DNA prevalence between cases and controls. There were significantly more EBV and CMV recent infections or reactivations based on VCA-IgM and CMV IgM in cases than controls, while there were no differences in IgG seroprevalence. CONCLUSION: The prevalence of positive EBV DNA detection and recent infection or reactivation is higher in children at onset of INS compared to a population matched for age, gender, and time of sampling.

Rapid molecular diagnosis of measles virus infection in an epidemic setting.

During the 2011 measles outbreak in Paris (France), patients with clinical suspicion of measles were tested for virological confirmation of measles virus (MV) infection. To assess the practical value of molecular diagnosis in an epidemic setting, 171 oral fluid samples and 235 serum samples collected from 270 patients were tested prospectively for MV-RNA using a novel one-step real-time RT-PCR assay including an internal control. Serum samples were also tested for MV-specific IgG and IgM antibodies. MV infection was confirmed by detection of MV-RNA and/or MV-IgM for 229 of the 270 patients. The results for the 102 cases with both serum and oral fluid samples available were used to compare the techniques. The detection rate of MV-RNA by RT-PCR was 98% (100/102) for oral fluid and 95% (97/102) for serum samples. The detection rate of MV-IgM was 85% (87/102). Negative MV-IgM results were observed mostly for serum samples collected early after the onset of the rash. A MV-RNA standard of known concentration obtained by in vitro transcription was used to quantify MV-RNA in samples. MV-RNA copy numbers were significantly higher in oral fluid than in serum samples, but did not correlate with time of sampling (within 1 week after the onset of the rash), patient age, or vaccination status. During the early stage of infection, the MV-RNA viral load in serum was lower in patients positive than in those negative for MV-IgG. In conclusion, the one-step real-time RT-PCR assay is a simple and sensitive tool suitable for MV diagnosis within hours.

Mononeuropathy multiplex associated with acute parvovirus B19 infection: characteristics, treatment and outcome.

To describe the characteristics of peripheral neuropathy related to acute parvovirus B19 (B19V) infection. We reviewed clinical, electrophysiological and histological data of three patients with peripheral neuropathy and positive B19V detection (IgG, IgM and PCR) compatible with acute infection. The neuropathy fulfilled criteria for mononeuropathy multiplex (MM). It could be preceded by or concurrent with a limited purpuric eruption, but systemic manifestations were absent. The first neurological symptoms were always sensory and localized in a hand. Neuropathy was initially limited to a restricted sensory part of a nerve trunk territory. The course was subacute with successive and asymmetric injury of the limb and cranial nerves. Electromyographic study confirmed the diagnosis of MM with multifocal asymmetric sensory and motor axonal loss in two patients, whereas the neuropathy was purely sensory and limited to two nerves in the other patient. Nerve biopsies showed no evidence of necrotizing vasculitis but, in one patient, revealed a lymphocytic perivascular infiltrate evocative of hypersensitivity vasculitis secondary to an infectious agent. Intravenous immunoglobulin (IVIg) was systematically administered. Long-term outcome was good but with incomplete sensory recovery and, for one patient, persistence of a functional disability. B19 V infection should be considered in the etiological assessment of MM, especially in the event of a progressive sensory disorder in the hands and a concomitant history of rash. IVIg may be an effective treatment for this inflammatory disorder.

Papular-purpuric gloves and socks syndrome associated with B19V infection in a 6-year-old child.

A 6 year-old girl was admitted for evaluation of a fever associated with a petechial rash of 2 days' duration. She was in good general condition with no acute distress. Inspection of the skin revealed an amazing papular and purpuric rash of predominantly acral and symmetrical distribution and sharply demarcated on the ankles. All laboratory tests were found normal. Rash and fever completely resolved in less than 3 days. Serological testing for parvovirus B19 (B19V) antibodies was positive for IgM but negative for IgG. Moreover, B19V DNA was detected in serum with a viral load of 2.24 x 10(8) copies per mL. So we concluded of a paediatric case of popular-purpuric gloves and socks syndrome (PPGSS) associated with B19V infection. PPGSS is an idiosyncratic reaction to viral infection. The syndrome has been associated with several viruses such as HHV6, measles, coxsackie B6, and above all B19V. PPGSS occurs mostly in young adults. It is characterised by a typical papular and purpuric rash with an acral distribution and a sharp demarcation on the wrists and ankles. The rash is often pruritic and can be accompanied by mucosal lesions and/or systemic symptoms such as fever, asthenia and lymphadenopathy. Most of the time, the disease is self-limited with a short course and a benign prognosis. A very similar disease has been described in some children. The distinctive clinical characteristics of PPGSS in children should be recognized by paediatrician in particular at the emergency room in order to avoid superfluous explorations.

Prospective identification of HEV-B enteroviruses during the 2005 outbreak.

Enteroviruses (EVs) represent the main etiological agents of epidemics of viral meningitis and especially the serotypes related to the human enterovirus B species. Genetic typing by sequencing a PCR-amplified portion of the genome has proved to be useful for identifying EVs and is more rapid than standard seroneutralization tests. However, prospective genotyping has not been reported in routine practice within a clinical diagnostic laboratory. A genetic typing assay using two sets of primers was developed for the amplification and sequencing of the VP1 coding sequence of the HEV-B serotypes. Identification was carried out by sequence comparisons with EV sequences in GenBank using the BLAST search tool and confirmed by phylogenetic analysis. This method was used to identify prospectively the 48 enteroviruses isolated in patients with either enterovirus-proved meningitis (n = 41) or other clinical manifestations (n = 7) admitted to the University Hospital of Clermont-Ferrand (France) in 2005. The assay was also used to type retrospectively EVs isolated in cerebrospinal fluid specimens of 25 patients admitted to the Trousseau Paediatric Hospital in Paris (France) between February and August 2005. In both prospective and retrospective investigations of meningitis, echovirus 30 (E30) was the most frequent serotype, followed in decreasing order by E18, E13, coxsackievirus B5, B3, E6, E4, E7, E11, E33, and coxsackievirus A9. In patients with other manifestations, coxsackievirus B3, B5, and E3 were each identified twice, and E2 once. In E30 infected patients, nine different lineages were demonstrated by phylogenetic analysis. Genetic typing allowed the prospective, effective and rapid identification of all EV isolates involved in the 2005 outbreak. Molecular typing in combination with phylogenetic analysis will be a reliable means to confirm the emergence of new EV variants, and is of interest of both individual patients and public health.

Comparison of the capacity of different viral internal ribosome entry segments to direct translation initiation in poly(A)-dependent reticulocyte lysates.

Polyadenylation stimulates translation of capped eukaryotic mRNAs and those carrying picornaviral internal ribosome entry segments (IRESes) in vivo. Rabbit reticulocyte lysates (RRL) reproduce poly(A)-mediated translation stimulation in vitro after partial depletion of ribosomes and ribosome-associated factors. Here, we have evaluated the effects of varying different parameters (extent of extract depletion, cleavage of eIF4G, concentrations of KCl, MgCl(2) and programming mRNA) on IRES-driven translation efficiency and poly(A)-dependency in ribosome-depleted RRL. For comparison, the study included a standard capped, polyadenylated mRNA. Dramatic differences were observed in the abilities of the different IRESes to direct translation in ribosome-depleted extracts. While the hepatitis A virus IRES was incapable of driving translation in physiological conditions in depleted RRL, mRNAs carrying the foot-and-mouth disease virus and hepatitis C virus IRESes were translated significantly better than a standard cellular mRNA in the same conditions. Indeed, the capacities of these IRESes to direct translation in ribosome-depleted RRL were similar to those reported previously in certain cell lines. Both the abilities of the IRESes to drive translation and their individual salt optima in ribosome-depleted extracts suggest that these elements have dramatically different affinities for some component(s) of the canonical translation machinery. Finally, using poliovirus as an example, we show that the ribosome-depleted system is well suited to the study of the translational capacity of naturally occurring IRES variants.

Free poly(A) stimulates capped mRNA translation in vitro through the eIF4G-poly(A)-binding protein interaction.

The 5' cap and 3' poly(A) tail of classical eukaryotic mRNAs functionally communicate to synergistically enhance translation initiation. Synergy has been proposed to result in part from facilitated ribosome recapture on circularized mRNAs. Here, we demonstrate that this is not the case. In poly(A)-dependent, ribosome-depleted rabbit reticulocyte lysates, the addition of exogenous poly(A) chains of physiological length dramatically stimulated translation of a capped, nonpolyadenylated mRNA. When the poly(A):RNA ratio approached 1, exogenous poly(A) stimulated translation to the same extent as the presence of a poly(A) tail at the mRNA 3' end. In addition, exogenous poly(A) significantly improved translation of capped mRNAs carrying short poly(A(50)) tails. Trans stimulation of translation by poly(A) required the eIF4G-poly(A)-binding protein interaction and resulted in increased affinity of eIF4E for the mRNA cap, exactly as we recently described for cap-poly(A) synergy. These results formally demonstrate that mRNA circularization per se is not the cause of cap-poly(A) synergy at least in vitro.