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BackgroundCOVID-19 is a complex multisystem disease, frequently associated with kidney injury. Since the beginning of the COVID-19 pandemic, we observed a striking increase in the incidence of acute tubulointerstitial nephritis (aTIN) without or with uveitis (TINUs) among children. This prompted us to examine whether SARS-CoV-2 might be the underlying trigger.MethodsWe conducted a French nationwide retrospective cohort study. We included all consecutive children diagnosed with aTIN or TINUs of undetermined cause between April-2020 and March-2021. SARS-CoV-2 antibody responses were tested by a luciferase immunoprecipitation system and compared to age-matched controls. Immunohistochemistry, immunofluorescence and molecular microbiology analyses were performed on kidney biopsies.ResultsForty-eight children were included with a median age at diagnosis of 14.7 years (9.4-17.6). aTIN and TINUs incidence rates increased 3-fold and 12-fold, respectively, compared to pre-pandemic years. All patients had impaired kidney function with a median eGFR of 31.9 ml/min/1.73m² at diagnosis. Kidney biopsies showed lesions of acute tubulointerstitial nephritis and 25% of patients had fibrosis. No patient had concomitant acute COVID-19. All 16 children tested had high anti-N IgG titers and one had anti-S IgGs. Next-generation sequencing failed to detect any infectious agents in kidney biopsies. However, SARS-CoV-2 RNA was detected by PCR in two kidney samples supporting a potential direct link between SARS-CoV-2 and aTIN/TINUs.ConclusionsWe describe a novel form of post-acute COVID-19 syndrome in children, unique in its exclusive kidney and eye involvement, and its distinctive anti-SARS-CoV-2 N+/S-serological profile. Our results support a causal association linking SARS-CoV-2 infection to this newly-reported burst of renal/eye inflammation.

International audience; Graft artery stenosis can have a significant short- and long-term negative impact on renal graft function. From the beginning of the COVID-19 pandemic, we noticed an unusual number of graft arterial anomalies following kidney transplant (KTx) in children. Nine children received a KTx at our center between February and July 2020, eight boys and one girl, of median age of 10 years. Seven presented Doppler features suggesting arterial stenosis, with an unusual extensive pattern. For comparison, over the previous 5-year period, persistent spectral Doppler arterial anomalies (focal anastomotic stenoses) following KTx were seen in 5% of children at our center. We retrospectively evidenced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in five of seven children with arterial stenosis. The remaining two patients had received a graft from a deceased adolescent donor with a positive serology at D0. These data led us to suspect immune postviral graft vasculitis, triggered by SARS-CoV-2. Because the diagnosis of COVID-19 is challenging in children, we recommend pretransplant monitoring of graft recipients and their parents by monthly RT-PCR and serology. We suggest balancing the risk of postviral graft vasculitis against the risk of prolonged dialysis when considering transplantation in a child during the pandemic.

International audience; Mycoplasma contamination threatens both the safety of biologics produced in cell substrates as well as the quality of scientific results based on cell-culture observations. Methods currently used to detect contamination of cells include culture, enzymatic activity, immunofluorescence and PCR but suffer from some limitations. High throughput sequencing (HTS) can be used to identify microbes like mycoplasmas in biologics since it enables an unbiased approach to detection without the need to design specific primers to pre-amplify target sequences but it does not enable the confirmation of microbial infection since this could reflect carryover of inert sequences. In order to unambiguously differentiate the presence of live or dead mycoplasmas in biological products, the present method was developed based on metabolic RNA labelling of newly synthetized mycoplasmal RNAs. HTS of labelled RNA detected A549 cell infection with Acholeplasma laidlawii in a manner similar to both PCR and culture and demonstrated that this technique can unambiguously identify bacterial species and differentiates infected cells from cells exposed to a high inoculum of heat-inactivated mycoplasmas. This method therefore combines the advantage of culture (that detects only live microorganisms) with those of molecular tests (rapidity) together with a very broad range of bacterial detection and identification.

International audience; Human Papillomaviruses (HPV) are responsible for over 99% of cervical cancers. Molecular diagnostic tests based on the detection of viral DNA or RNA have low Positive Predictive Values (PPV) for the identification of cancer or precancerous lesions. Triage with the Papanicolaou test lacks sensitivity and even when combined with molecular detection of high-risk HPV results in a significant number of unnecessary colposcopies. We have developed a broad range detection test of HPV transcripts to take a snapshot of the transcriptome of 16 high-risk or putative high-risk HPV in cervical lesions (HPV16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, 68, 73, and 82). The purpose of this novel molecular assay is to detect and type HPV-positive samples and to determine a combination of HPV reads at certain specific viral spliced junctions that can better correlate with high-grade cytology, reflecting the presence of precancerous cells. In a proof-of-concept study conducted on 55 patients, starting from cervical smears, we have shown that (i) HPV RNA-Seq can detect papillomaviruses with performances comparable to a widely used HPV reference molecular diagnostic kit, and (ii) a combination of the number of sequencing reads at specific early vs late HPV transcripts can be used as a marker of high-grade cytology, with encouraging diagnostic performances as a triage test.

Background: Lao PDR has low reported COVID-19 cases but it is unclear whether this masks silent transmission. A nationwide seroprevalence study was done between August and September 2020 to determine SARS-CoV-2 exposure. Methods: Participants were from the general community/healthcare workers in five provinces. Bat/wildlife contacts were from Vientiane province. ELISAs detected anti-Nucleoprotein (N; n=3173 tested) and anti-Spike (S; n=1417 tested) SARS-CoV-2 antibodies. Double-positive samples were checked by IgM/IgG rapid tests. Positive controls were confirmed COVID-19 cases and negative controls were pre-COVID-19 samples. Findings: In pre-COVID-19 samples, 14/265 (5·3%, [95% CI=3·1-8·7%]) were anti-N antibody single-positive and 3/265 (1·1% [0·3-3·5%]) were anti-S antibody single positive. None were anti-N and anti-S antibody double positive. Anti-N and anti-S antibodies were detected in 131/2417 (5·4% [4·5-6·3%]) and 19/1061 (1·8% [1·1-2·8%]) of the general population, 13/666 (2·0% [1·1-3·3%]) and 4/282 (1·4% [0·5-3·7%]) of healthcare workers and 15/74 (20·3% [12·6-31·0%]) and 5/74 (6·8% [2·8-15·3%]) of bat/wildlife contacts. Only 2/3173 (0·1% [0·02-0·3%]) were double positive for anti-N and anti-S antibodies (rapid test negative). Interpretation: We find no evidence for significant circulation of SARS-CoV-2 in Lao PDR during or before September 2020. This likely results from decisive measures taken by the government early in the pandemic, social behavior, and low population density. High anti-N antibodies/low anti-S antibodies in bat/wildlife contacts may indicate exposure to cross-reactive animal coronaviruses with threat of emerging novel viruses. Funding: Core; Agence Francaise de Developpement. Additional support; Institut Pasteur du Laos, Institute Pasteur, Paris and Luxembourg Ministry of Foreign and European Affairs (“PaReCIDS II”). Declaration of Interests: The authors have no conflict of interest to declare. Ethics Approval Statement: The study protocol was approved by all participating institutes and by the Lao National Ethics Committee for Health Research (NECHR) (Ref #052/2020).

Background: The Oise department in France has been heavily affected by COVID-19 in early 2020. Methods: Between 30 March and 4 April 2020, we conducted a retrospective closed cohort study among pupils, their parents and siblings, as well as teachers and non-teaching staff of a high-school located in Oise. Participants completed a questionnaire that covered history of fever and/or respiratory symptoms since 13 January 2020 and had blood tested for the presence of anti-SARS-CoV-2 antibodies. The infection attack rate (IAR) was defined as the proportion of participants with confirmed SARS-CoV-2 infection based on antibody detection. Blood samples from two blood donor centres collected between 23 and 27 March 2020 in the Oise department were also tested for presence of anti-SARS-CoV-2 antibodies. Findings: Of the 661 participants (median age: 37 years), 171 participants had anti-SARS-CoV-2 antibodies. The overall IAR was 25.9% (95% confidence interval (CI) = 22.6-29.4), and the infection fatality rate was 0% (one-sided 97.5% CI = 0 - 2.1). Nine of the ten participants hospitalised since mid-January were in the infected group, giving a hospitalisation rate of 5.3% (95% CI = 2.4 –9.8). Anosmia and ageusia had high positive predictive values for SARS-CoV-2 infection (84.7% and 88.1%, respectively). Smokers had a lower IAR compared to non-smokers (7.2% versus 28.0%, P

Introduction La plupart des agents pathogenes infectieux contiennent un genome d’ADN ou d’ARN ce qui fait du sequencage a haut debit une approche seduisante pour la detection des agents infectieux. Aussi le cout du sequencage a considerablement diminue depuis 2010 ce qui rend cette technique compatible avec une realisation en routine. C’est dans ce contexte que notre laboratoire de microbiologie clinique recoit depuis novembre 2019 des prelevements pour la recherche d’agents pathogenes par metagenomique. Materiels et methodes L’analyse des prelevements par metagenomique est declenchee par la prescription medicale et realisee apres l’accord des biologistes du service de microbiologie. Selon le contexte clinique tous les prelevements peuvent etre analyses. L’acheminement vers le laboratoire est effectue dans la carboglace. Les resultats sont disponibles en 2 a 3 semaines. Le sequencage a haut debit est realise sur la plateforme illumina NextSeq. Sur la base des sequences produites, 3 outils bioinformatiques sont utilises en parallele pour la detection des bacteries, levures et champignons: Kraken2 et Centrifuge sont des outils bases sur l’identification de sequence par composition de k-mers, ils utilisent les bases de sequence NCBI RefSeq et RVDB. MetaPhlAn2 utilise une base de marqueurs developpes par bowtie2. L’identification des virus utilise l’outil original Microseek qui traduit toutes les sequences d’acides nucleiques en sequences proteiques et interroge les bases de donnees RVDB-prot et NCBI NR/NT. Resultats Nous avons analyse 223 prelevements entre novembre 2019 et mars 2021. Au moins un agent pathogene a ete identifie dans 87 (39 %) prelevements, tandis que 136 (61 %) sont restes negatifs ou ont permis l’identification d’une flore bacterienne ou virale. 137 (61 %) etaient des biopsies et 86 (39 %) des liquides biologiques. Parmi 87 prelevements positifs, 13 (15 %) etaient positifs dans un premier temps uniquement en metagenomique avant d’etre confirmes par une technique conventionnelle. Parmi ces cas: un cas d’encephalite a European Bat lyssavirus, un cas d’encephalite a Astrovirus de la clade neurotrope et un cas de granulome post-rubeole. Aussi l’approche metagenomique a permis d’identifier deux virus probablement en cause pour deux series de patients immunodeprimes avec des tableaux cliniques similaires : – cytolyse hepatique inexpliquee ; – encephalites avec perte de la vue progressive. Conclusion Le diagnostic clinique par metagenomique est une methode de diagnostic sans a priori qui permet de detecter des agents pathogenes : – connus qui ne sont pas detectes dans nos laboratoires hospitaliers en routine ; – connus qui n’ont pas ete cherches car inconnus dans le syndrome explore ; – inconnus a ce jour. Le sequencage a haut debit est une technologie qui ameliore significativement notre capacite a diagnostiquer les maladies infectieuses.

Introduction Le role du virome cutane dans les dermatoses inflammatoires reste mal connu du fait de contraintes techniques specifiques. De plus, sa description reste qualitative car la correlation entre le nombre de reads obtenus apres une amplification random + un sequencage haut-debit (HTS) et le nombre de copies de genome viral n’est pas demontree. Objectif Decrire qualitativement et quantitativement l’evolution topographique et temporelle des papillomavirus et polyomavirus humains cutanes (HPV et HPyV) chez 2 patients souffrant de dermatite atopique (DA) et de psoriasis (Pso). Materiel et methodes Nous avons extrait l’ADN de prelevements cutanes effectues sur peau lesionnelle (PL) et non lesionnelle (PNL) chez ces 2 patients a M0, M1 et M3. A M0, un traitement par methotrexate (MTX) etait instaure chez le patient DA et par dermocorticoides seulement chez la patiente Pso. L’utilisation d’une technique de PCR multiplex AmpliSeq® a precede le HTS. Les resultats etaient compares a une PCR quantitative (qPCR) pour etude de correlation. Discussion Les resultats de l’association AmpliSeq®+ HTS et ceux de la qPCR etaient significativement correles (coefficient κ 0,95), demontrant que l’association AmpliSeq®+ HTS permet la quantification les charges virales, avec cependant davantage de sensibilite que la qPCR. Chez les 2 patients, 31 et 32 souches virales ont ete detectees respectivement, principalement des b et g HPV mais egalement du Polyomavirus de Merkel (MCPyV). La composition de la flore virale etait variable selon la topographie et au fil du temps. Cependant chez le patient DA, les bHPV107 et 120 predominaient en PL (70,95 %), tandis que le gHPV134 predominait en PNL (93,1 %). Chez le patient Pso, le bHPV12 et le MCPyV (65,4 %) predominaient en PL, tandis que le gHPV50 predominait en PNL (92,6 %). Parallelement a l’amelioration clinique, la composition de la flore virale a varie au fil du temps en PL, tandis qu’elle est restee plus stable dans la PNL chez les 2 patients. Chez le patient DA, le bHPV107 n’etait plus surrepresente a M3 en PL (10,3 %) tandis que le gHPV134 continuait de predominer de M0 a M3 en PNL. Chez le patient Pso, en PL, le bHPV12 diminuait a M3 (0,05 %) tandis que le MCPyV devenait predominant (37,7 %). Au contraire, le gHPV50 restait predominant en PNL de M0 a M3. Conclusion Malgre de grandes variations intra et interindividuelles de la flore virale, des signatures virales individuelles qualitatives et quantitatives ont pu etre detectees dans la PNL et dans la PL en fonction de l’evolution de l’activite de la DA et du Pso : la flore virale d’un individu semble peu varier quantitativement et qualitativement en PNL dans le temps, meme sous MTX, contrairement a celle de la PL.

International audience; Ticks transmit more pathogens-including bacteria, parasites and viruses-than any other arthropod vector. Although the epidemiological status of many tick-borne bacteria is very well characterized, tick-borne viruses are still relatively under-studied. Recently, several novel tick-borne viruses have been isolated from human febrile illnesses following tick bites, indicating the existence of other potential new and unknown tick-borne viruses. We used high-throughput sequencing to analyse the virome of Ixodes ricinus, the main vector of tick-borne pathogens in Europe. The majority of collected viral sequences were assigned to two potentially novel Nairovirus and Phlebovirus viruses, with prevalence rates ranging from 3.95% to 23.88% in adults and estimated to be between 0.14% and 72.16% in nymphs. These viruses could not be isolated from the brains of inoculated immunocompromised mice, perhaps indicating that they are unable to infect vertebrates. Within the I. ricinus virome, we also identified contigs with >90% identity to the known Eyach virus. Initially isolated in the 1980s, this virus was indirectly associated with human disease, but had never been extensively studied. Eyach virus prevalence varied between 0.07% and 5.26% in ticks from the French Ardennes and Alsace regions. Eyach virus was successfully isolated following intracerebral inoculation of immunocompromised mice with Eyach virus-positive tick extracts. This virus was also able to multiply and persist in the blood of immunocompetent mice inoculated by intraperitoneal injection, and caused brain infections in three of nine juveniles, without any obvious deleterious effects.

International audience; Fetal bovine serum (FBS) and trypsin are reagents used in cell culture and have been the source of viral contamination of pharmaceutical products. We performed high throughput sequencing (HTS) of two pools of commercial batches of FBS and three commercial batches of trypsin. Taxonomies were assigned by comparing sequences of contigs and singletons to the entire NCBI nucleic acid and protein databases. The same major viral species were evidenced between batches of a given reagent but the proportion of viral reads among total reads varied markedly between samples (from 0.002% to 22.7%). In FBS, the sequences found were mainly from bovine viral diarrhea virus (BVDV) 1 to 3 and bovine parvovirus 3 (BPV3). The BVDV sequences derived from FBS showed only minor discrepancies with primers generally used for the screening of BVDV. Viral sequences in trypsin were mainly from porcine circovirus type 2. Other known viral sequences at lower read counts and potential new viral species (bovine parvovirus and bovine pegivirus) were evidenced. The load of some known and new viruses detected by FITS could be quantified by qPCR. Results of HTS provide a framework for evaluating the pertinence of control measures including the design of PCRs, bioassays and inactivation procedures.

In order to analyze the role of αvβ3 and αvβ5 integrins in gene transfer by adenovirus-based vectors, an RGD4C motif was inserted into the HI-loop of wild type or shortened fiber protein of human adenovirus of serotype 5, thereby creating Ad5RGD4C and Ad5Δ639RGD4C vectors, respectively. Infection by the latter is independent of the Coxsackie B adenovirus receptor. Internalization and transduction of these vectors and were investigated in several stably transfected cell clones derived from a human laryngeal carcinoma cell line (HEp2) expressing different ratios of αvβ5 and αvβ3 integrins. We show that αvβ3 is more successful than αvβ5 in: (i) mediating adenovirus internalization and transduction when the RGD motif is present only in the penton base and (ii) mediating internalization and transduction by RGD4C-fiber modified adenoviruses. The highest amount of internalized virus was found in the cell clone in which αvβ3 integrin predominated over αvβ5 integrin (as judged by the % of cells expressing αvβ3 and αvβ5 integrins). However the level of transgene expression in this cell line was even lower than that in parental HEp2 cells which do not express αvβ3 integrin. This discrepancy between internalization and transgene expression (transduction) is likely due to the crucial role of αvβ5 in membrane permeabilization, indicating that αvβ5 integrin is a limiting factor for Ad5-mediated gene transfer. We conclude that αvβ3 integrin is an efficient adenovirus internalization receptor, but cannot functionally replace αvβ5 in endosomal release.

The coxsackie B virus and adenovirus receptor (CAR) functions as an attachment receptor for multiple adenovirus serotypes. It has been shown that apart from virus-cellular receptor interactions, the fiber shaft length also influences viral tropism. We therefore generated Ad5FbDelta639 virus with 8beta-repeats in the shaft, instead of the 22beta-repeats present in the wild-type. Here, we show that the extent of attachment of the virus with shortened fiber to CAR-expressing cells was three- to fivefold lower than that of the wild-type. Transduction studies, however, clearly showed that infection of CAR-expressing cells with Ad5FbDelta639 was strongly impaired by comparison with the wild-type virus. Since this impairment was not linked to a proportional reduction in binding to cells, it appeared to be linked to subsequent/later events in infection. A similar decrease in efficacy of postbinding steps was also evidenced in cells that did not express CAR.

Replication-defective human adenoviruses type 5 (HAd5) expressing the bovine herpesvirus type 1 (BHV-1) glycoprotein gC or gD under the control of the human cytomegalovirus immediate-early promoter/enhancer (AdCMVgC or AdCMVgD) or the 5′ regulatory region of the human desmin gene (AdDESMgC or AdDESMgD) were generated. A preliminary experiment performed on rabbits showed that the intranasal administration of AdCMV elicited higher levels of BHV-1 neutralizing antibodies than the intramuscular administration of AdDESM. The obtained results allowed to select the replication-defective AdCMVgC and AdCMVgD for further assessment of their potential as a recombinant vaccine in cattle. Calves were injected intranasally twice 3 weeks apart with either AdCMVgC or AdCMVgD or a combination of these two recombinants or a commercially available live vaccine for comparison. The highest BHV-1 neutralizing antibody titres were obtained with AdCMVgD followed by the live vaccine and to a lower extent with the combination of the two recombinants (AdCMVgC+AdCMVgD). Calves were protected against intranasal BHV-1 challenge performed 3 weeks after the second immunization. In view of the obtained results, recombinant HAd5 may be developed as an intranasal vaccine vector in cattle administrated either alone or sequentially with non-human adenovirus-based vectors.

International audience; Objective: Infections are the major cause of morbidity and mortality in immunocompromised patients. Improving microbiological diagnosis in these patients is of paramount clinical importance. Methods: We performed this multicentre, blinded, prospective, proof-of-concept study, to compare untargeted next-generation sequencing with conventional microbiological methods for first-line diagnosis of infection in 101 immunocompromised adults. Patients were followed for 30 days and their blood samples, and in some cases nasopharyngeal swabs and/or biological fluids, were analysed. At the end of the study, expert clinicians evaluated the results of both methods. The primary outcome measure was the detection rate of clinically relevant viruses and bacteria at inclusion. Results: Clinically relevant viruses and bacteria identified by untargeted next-generation sequencing and conventional methods were concordant for 72 of 101 patients in samples taken at inclusion (k test ¼ 0.2, 95% CI 0.03-0.48). However, clinically relevant viruses and bacteria were detected in a significantly higher proportion of patients with untargeted next-generation sequencing than conventional methods at inclusion (36/101 (36%) vs. 11/101 (11%), respectively, p

The study of the prion protein (PrP) physiological functions or its specific role in transmissible spongiform encephalopathies (TSE) requires new tools, particularly those able to induce PrP overexpression in a large range of cells, in vivo as well as in vitro. Here we describe the construction of two recombinant adenoviruses encoding the human PrP either with a valine at position 129 (AdTRVal) or a methionine (AdTRMet). Both genes were put under the control of the tetracycline-responsive promoter, allowing tight regulation of PrP expression. AdTRVal and AdTRMet induced high expression of the human PrP in CHO-KI cells and in organotypic brain slices in culture. The proteins expressed from these viruses exhibited a glycosylphosphatidyl inositol (GPI) anchor, proper glycosylation and sensitivity to proteinase K digestion. AdTRVal and AdTRMet will allow future studies on the human PrP and on the role of the codon 129 polyphormism in human TSE.

Application of gene therapy to the field of cardiovascular disorders has been the subject of intensive work over the recent period. Gene therapy for cardiovascular disorders is now fast developing with most therapies being devoted to the consequences (ischemia) rather than the causes of atherosclerotic diseases. Recent human clinical trials have shown that injection of naked DNA encoding vascular endothelial growth factor promotes collateral vessel development in patients with critical limb ischemia or chronic myocardial ischemia. Promising studies in animals have also fueled enthusiasm for treatment of human restenosis by gene therapy, but clinical applications are warranted. Application of gene transfer to other cardiovascular diseases will require the coordinated development of a variety of new technologies, as well as a better definition of cellular and gene targets.

Atrial natriuretic peptide (ANP) exhibits relaxant and growth-inhibiting effects on vascular smooth muscle cells (VSMCs). To obtain ANP gene expression in VSMCs, we built a recombinant adenovirus containing the ANP cDNA controlled by the adenovirus major late promotor (AdMLP-ANP). After pulmonary VSMC treatment with AdMLP-ANP at a multiplicity of infection ranging from 5 to 100 TCID 50 /cell, immunoreactive ANP was detectable in the cell culture medium at a level that reached 101 ± 27 pmol/well after 2 days. The newly expressed ANP was biologically active, as evidenced by its ability to induce cyclic guanosine monophosphate accumulation in target cells and to mimic the effect of exogenous ANP (10 –8 to 10 –7 mol/L). Cell growth and survival of AdMLP-ANP–infected cells were decreased and were associated with the promotion of VSMC apoptosis. These effects, which occurred at a multiplicity of infection of 10 to 100 TCID 50 /cell, were observed neither in cells infected with the control adenoviral constructs (AdMLP-βGAL and AdMLP-gD) nor in cells treated with exogenous ANP (10 –7 to 10 –6 mol/L). These results showing VSMC apoptosis in response to ANP gene expression may have important implications for the prevention of vascular remodeling by gene therapy. (J Lab Clin Med 2001;137:155-64)

Adenovirus and poxvirus recombinant vectors are more and more used as live experimental vaccines. In order to compare the efficacy of these vectors to elicit serological response and protection against challenge, two recombinants carrying the same gene (pseudorabies virus gD) were used as experimental vaccines in mice, a permissive species to pseudorabies infection. Two routes were tested: intramuscular (i.m.) and intranasal (i.n.) in order to try to stimulate general and mucosal immune responses. Several doses ranging from 10(2.9) to 10(8.9) TCID50, depending on the vaccines were tested. The estimated log 10 (PD50) for the i.m. route were 7.1 +/- 0.2 for the adenovirus vector (Ad-gD), and 7.6 +/- 0.2 for the Nyvac vector (vP900). For the i.n. route, log 10 (PD50) of Ad-gD was 7.1 +/- 0.2, and was higher than 7.9 for vP900. While the adenovirus vector proved more efficient than the poxviral vector to elicit antibody response, only a slight difference was observed when comparing the survival times of animals after challenge. Adenovirus was found better only for the 10(7.9) TCID50 dose, when inoculated i.m. Intranasal vaccination appeared efficient only with the adenovirus vector for the TCID50 10(8.9) dose.

A summary is given on the 4 topics which were discussed during the round table and which represent current knowledge on the molecular biology of Aujeszky's disease (pseudorabies) virus. They include a review on 1. the genome and gene products of the virus; 2. the viral genes associated with virulence; 3. the immunological role of the viral gene products and 4. studies intended to compare the efficacy of several commercially available vaccines and to establish a possible correlation between antibodies against individual structural viral proteins and degree of protection. It was concluded that gI deleted vaccines appear to be the best choice for use in intensive vaccination programmes towards eradication of Aujeszky's disease virus. However, there remains a need for development of more potent vaccines which induce strong humoral and cell mediated immune responses and afford complete protection, virological protection included. It is often observed that live vaccine strains which are completely avirulent lose much capacity to replicate and spread within the vaccinated animal. It is, however, not excluded that a certain degree of dissemination may be needed to be fully efficacious. Loss of virulence may thus be accompanied by too much loss of immunogenicity. An improved genetic stability of live vaccine strains when they are obtained by genetic manipulation, possibly justifies a more widespread dissemination of the vaccine strain in the body compared to that with conventionally developed strains or compared to what is presently allowed.

Un modele theorique permettant d'estimer la sensibilite de la technique Elisa appliquee au lait de melange dans le cadre du depistage de la leucose bovine enzootique a ete propose. Ses parametres ont ete estimes a partir de l'etude de 121 laits individuels. Sa validite a ete etudiee sur un echantillon de 47 etables infectees. Enfin, sa valeur prospective a ete abordee par la comparaison des resultats predits a ceux effectivement enregistres lors d'une enquete concernant 325 etables du departement des Landes.