Reliability of the rapid antigen test for diagnosis of SARS-CoV-2 in Tunisia.

Background: Early and accurate diagnosis is crucial for preventing the spread of SARS-CoV-2 infection. The rapid antigen test was developed for testing infection, and it was necessary to assess its performance before widespread use in Tunisia. Aim: To evaluate the effectiveness of a rapid antigen test for the detection of SARS-CoV-2 in nasopharyngeal swabs in Tunisia. Methods: Nasopharyngeal samples were taken from COVID-19 suspected cases between October and December 2020 and tested using the Standard Q COVID-19 Ag test (SD-Biosensor, Republic of Korea) and real-time reverse transcription polymerase chain reaction (RT­PCR). Results: Overall, 4539 patients were tested. Of the total study population (N = 4539), 82.5% of positive samples remained positive with the rapid antigen test, while 20.2% (470/2321) of samples that were negative with rapid antigen test were confirmed positive with RT-PCR, giving a negative predictive value of 79.8% for the rapid antigen test. The sensitivity and negative predictive value of the rapid antigen test were 70.2% and 65.8%, respectively. These results improved to 96.4% and 92.8%, respectively, when considering the cycle threshold value by RT-PCR below 25. Conclusion: Although the rapid antigen test was less sensitive than RT-PCR, its ability to rapidly detect individuals with high viral loads makes it suitable for use during an epidemic.

Large spontaneous HBV DNA fluctuations and potential usefulness of a single-point measurement of combined HBV DNA and quantitative HBsAg for the exclusion of HBeAg-negative chronic hepatitis B: A prospective Tunisian cohort study.

BACKGROUND AND STUDY AIM: During the natural course of HBeAg-negative chronic hepatitis B (CHB), fluctuations in hepatitis B virus (HBV) DNA and alanine aminotransferase (ALT) levels are often observed, making the classification of patients difficult. We aimed to describe spontaneous short-term HBV DNA level fluctuations and to assess the usefulness of qHBsAg in Tunisian patients with HBeAg-negative chronic HBV infection. PATIENTS AND METHODS: We included 174 treatment-naive Tunisian patients with HBeAg-negative chronic HBeAg-negative HBV infection. A prospective 1-year follow-up was conducted with serial determinations of HBV DNA, ALT levels, and qHBsAg. The patients were classified into three groups: inactive carriers (G1), patients with negative HBeAg CHB (G2), and patients with an "indeterminate state" (G3). For the latter group, a liver biopsy was indicated. RESULTS: Only genotype D was detected. During follow-up, 21.6% and 19.5% of patients with a low initial (<2,000 IU/ml) and intermediate viral load (2,000-20,000 IU/ml) experienced a subsequent increase in their HBV DNA levels above 2,000 and 20,000 IU/ml, respectively. Significant variations in viral load were observed in 61.1% of patients at 6-month intervals. Among the 174 patients, 89 (51.1%) belonged to G1, 33 (19%) to G2, and 52 (29.9%) to G3. Fourteen patients have undergone a liver biopsy, of whom seven showed moderate to severe liver disease. Combination of HBV DNA < 2,000 IU/ml and qHBsAg < 832 IU/ml excluded CHB in 98.4% of cases. A cutoff point for qHBsAg < 100 IU/ml associated with an annual decline of > 0.5 log 10 IU/ml is a good predictor marker of functional cure for hepatitis B. CONCLUSIONS: This study highlights the large short-term fluctuations in HBV DNA in patients with HBeAg-negative chronic HBeAg-negative HBV infection with genotype D. Thus, using the cutoff value of 832 for qHBsAg combined with that of 2,000 for HBV DNA makes it possible to exclude CHB for most patients.

The value of West Nile virus RNA detection by real-time RT-PCR in urine samples from patients with neuroinvasive forms.

INTRODUCTION: Routine laboratory screening is based on the detection of WNV specific IgM and IgG in blood and cerebrospinal fluid. Confirmation is then classically applied by real time RT-PCR (rRT-PCR) in Cerebrospinal fluid (CSF), which often gives negative results due to too short virorachia and late sampling. rRT-PCR was applied-for the first time for routine diagnosis purpose-on urine samples. METHODS: During 2018 outbreak in Tunisia, 107 patients presented WNV neurologic symptoms and were positive for WNV serology. Of them, 95 patients were sampled for urine and 35 were sampled for CSF. Qualitative rRT-PCR was performed on both type of samples. RESULTS: WNV RNA was detected in 50.5% of urine samples (48/95) and in 2.8% of CSF samples (1/35). WNV RNA was detectable from day 1 to day 41 from symptom onset, however, positive urine rate was 53.1% during the first 10 days from symptom onset. The proportions of urine-positive and urine-negative samples, based on day of collection, showed no statistical difference (p > 0.005). Cycle threshold (Ct) values ranged from 12 to 39, with no correlation with the day of collection. The lowest Ct value was detected for urine sampled on day 5 after symptom onset. A statistically significant difference was found between age groups of confirmed and non confirmed cases (p < 0.001). DISCUSSION/CONCLUSION: Our study reported the use of rRT-PCR on urine samples as a confirmatory diagnostic tool for WNV "probable cases" during an outbreak. Our findings underlined the reliability and the rapidity of this confirmatory tool, even late, and showed its superiority on CSF investigation.

Clinical characteristics and outcomes of critically ill COVID-19 patients in Sfax, Tunisia.

BACKGROUND: Africa, like the rest of the world, has been impacted by the coronavirus disease 2019 (COVID-19) pandemic. However, only a few studies covering this subject in Africa have been published. METHODS: We conducted a retrospective study of critically ill adult COVID-19 patients-all of whom had a confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection- admitted to the intensive care unit (ICU) of Habib Bourguiba University Hospital (Sfax, Tunisia). RESULTS: A total of 96 patients were admitted into our ICU for respiratory distress due to COVID-19 infection. Mean age was 62.4±12.8 years and median age was 64 years. Mean arterial oxygen tension (PaO2)/fractional inspired oxygen (FiO2) ratio was 105±60 and ≤300 in all cases but one. Oxygen support was required for all patients (100%) and invasive mechanical ventilation for 38 (40%). Prone positioning was applied in 67 patients (70%). Within the study period, 47 of the 96 patients died (49%). Multivariate analysis showed that the factors associated with poor outcome were the development of acute renal failure (odds ratio [OR], 6.7; 95% confidence interval [CI], 1.75-25.9), the use of mechanical ventilation (OR, 5.8; 95% CI, 1.54-22.0), and serum cholinesterase (SChE) activity lower than 5,000 UI/L (OR, 5.0; 95% CI, 1.34-19). CONCLUSIONS: In this retrospective cohort study of critically ill patients admitted to the ICU in Sfax, Tunisia, for acute respiratory failure following COVID-19 infection, the mortality rate was high. The development of acute renal failure, the use of mechanical ventilation, and SChE activity lower than 5,000 UI/L were associated with a poor outcome.

The Delta variant wave in Tunisia: Genetic diversity, spatio-temporal distribution and evidence of the spread of a divergent AY.122 sub-lineage.

Introduction: The Delta variant posed an increased risk to global public health and rapidly replaced the pre-existent variants worldwide. In this study, the genetic diversity and the spatio-temporal dynamics of 662 SARS-CoV2 genomes obtained during the Delta wave across Tunisia were investigated. Methods: Viral whole genome and partial S-segment sequencing was performed using Illumina and Sanger platforms, respectively and lineage assignemnt was assessed using Pangolin version 1.2.4 and scorpio version 3.4.X. Phylogenetic and phylogeographic analyses were achieved using IQ-Tree and Beast programs. Results: The age distribution of the infected cases showed a large peak between 25 to 50 years. Twelve Delta sub-lineages were detected nation-wide with AY.122 being the predominant variant representing 94.6% of sequences. AY.122 sequences were highly related and shared the amino-acid change ORF1a:A498V, the synonymous mutations 2746T>C, 3037C>T, 8986C>T, 11332A>G in ORF1a and 23683C>T in the S gene with respect to the Wuhan reference genome (NC_045512.2). Spatio-temporal analysis indicates that the larger cities of Nabeul, Tunis and Kairouan constituted epicenters for the AY.122 sub-lineage and subsequent dispersion to the rest of the country. Discussion: This study adds more knowledge about the Delta variant and sub-variants distribution worldwide by documenting genomic and epidemiological data from Tunisia, a North African region. Such results may be helpful to the understanding of future COVID-19 waves and variants.

Focus on hepatitis C virus genotype distribution in Tunisia prior to elimination: a 16-year retrospective study.

With the introduction of direct-acting antiviral treatment (DAA), Tunisia has committed to achieving the international goal of eliminating viral hepatitis. Because the specific DAA prescribed depends on viral genotype, viral genotyping remains of great importance. The aim of the present study was to outline the trends in the distribution of HCV genotypes from 2002 to 2017 in the Tunisian general population in order to guide authorities towards the most appropriate therapeutic strategies for preventing HCV infection. A total of 2532 blood samples were collected over a 16-year period and from all regions of Tunisia. Genotyping showed that genotype 1 (subtype 1b) was the most prevalent genotype in the country (n = 2012; 79.5%), followed by genotype 2 (n = 339; 13.3%). Genotypes 3, 4 and 5 were detected in 4.8%, 2.2% and 0.1% of the country's population, respectively. Mixed infections with different HCV genotypes were detected in 0.1% of the population (one case each of genotypes 1b + 4, 1b + 2 and 2 + 4). Interestingly, a significant increase in genotypes 2, 3 and 4 was observed over time (p = 0.03). Sixteen different subtypes were detected over the study period, most of which were subtypes of genotype 2, and some of these subtypes appeared to be new. Patients infected with genotypes 1a, 3 and 4 were significantly younger than those infected with genotypes 1b and 2 (p < 0.01). Furthermore, genotypes 1b and 2 were detected more often in women than men, while genotypes 1a and 3 were detected mostly in men (P < 0.01). Our study confirms a large predominance of genotype1/subtype1b in Tunisia and shows a significant increase in the prevalence of other genotypes over time. These findings reinforce the need for an additional HCV genotype survey to improve the design of treatment strategies in Tunisia.

Genetic characterization of West Nile Virus strains during neuroinvasives infection outbreak in Tunisia, 2018.

West Nile Virus (WNV) is an arbovirus transmitted by mosquito bite involving birds as reservoirs, humans and equines as accidental hosts. Eight distinct lineages (WNV-1 to WNV-8) have been identified: WNV-1 and WNV-2 infect humans and animals, and WNV-3 to WNV-8 have been identified only in vectors. WNV has been implicated in neuroinvasives infections, especially meningitis and encephalitis. Tunisia experienced three epidemics in 1997, 2003 and 2012. Serological studies on humans, equines and birds as well as the detection of the virus in the vector favour a fairly frequent circulation in the country. A new epidemic has been observed in Tunisia between August and November 2018. The obtained sequences of the VWN from Tunisia 2018 grouped in a distinct monophyletic group within the Mediterranean subtype in Cluster 1, with a maximum of 2% nucleotide divergence. These sequences were clearly distinct from the Tunisia 1997, which grouped with sequences mainly from USA in Cluster 2. This work reports the genetic characterization of the Tunisia 2018 strain in comparison with the previously identified strains in Tunisia and worldwide. The epidemic virus Tunisia 2018 was genetically close to the Mediterranean basin and Eastern Europe sequences but distinct from the Tunisia 1997 closely related to the American sequences.

The intrathecal polyspecific antiviral immune response (MRZ reaction): A potential cerebrospinal fluid marker for multiple sclerosis diagnosis.

We tested the performance of MRZ-reaction, an intrathecal humoral immune response against-Measles (M), Rubella (R) and Varicella Zoster (Z) viruses, in multiple sclerosis (MS) diagnosis. The MRZ-reaction was significantly more positive in MS than in non-MS group with a specificity of 91.9%. In MS group, the RZ-profile was the most prevalent and the R-specific antibody-index was correlated to the number of oligoclonal bands (OCB) in CSF. Interestingly, the MRZ-reaction was detected in 53% of OCB-negative-MS patients. The MRZ-reaction seems to be a relevant CSF diagnostic marker of MS disease. The likely relation between its positivity and the vaccination status deserves to be investigated.

Childhood rubella encephalitis: diagnosis, management, and outcome.

We to report clinical biological and radiologic features of rubella encephalitis in childhood and assess its prognostic impact. Our retrospective study was conducted in an intensive care unit of a university hospital in Sfax, Tunisia. Twenty-one children (age range, 1-15 years) were included. Median age was 9 years (lower and upper quartiles, 7-11 years). On admission, generalized maculopapular eruption was found in 17 cases (81%). Median Glasgow Coma Scale score was 7 (lower and upper quartiles, 7-8). Twenty patients (95.2%) experienced at least 1 episode of seizures. Sixteen patients (76.2%) developed a status epilepticus. The result for enzyme-linked immunosorbent assay detecting anti-rubella immunoglobulin (M) was positive in the serum and in the cerebrospinal fluid samples for all our patients. Magnetic resonance imaging (MRI) of the brain was performed on admission for 3 patients (14.3%) and within a median of 4 days (lower and upper quartiles, 2-6 days) for 8 patients. The test was normal in 6 cases. Two deaths were recorded (9.5%). Survivors had no neurological sequelae 6 months after intensive care unit discharge.

HLA association with nasopharyngeal carcinoma in southern Tunisia.

In order to study the association of HLA-A, -B and/or DRB1, DQB1 and the nasopharyngeal carcinoma (NPC), 141 patients affected with NPC were typed for the HLA class I by serology method of microlymphocytotoxicity. Among these patients 101 were genotyped for HLA class II system by the PCR-SSP technique. HLA typing results were compared to those of 116 controls. We found that the HLA-A31 and -A33 antigens were significantly more expressed in patients than in the controls (P = 0.016 and 0.010, respectively) and the HLA-A19 antigen, was significantly more frequent in patients when compared to the controls (P = 0.007). The HLA-DRB1*03 and DRB1*13 alleles were significantly more frequent in patients as compared to the controls. The DRB1*01 allele was expressed with a frequency of 20.69% in the controls whereas it was only detected in 3.96% of the NPC patients. Furthermore, the DQB1*05 allele was expressed at a frequency which was significantly less important in affected patient (P = 0.03), whereas, the DQB1*02 allele was more frequent in patients (P = 0.643 x 10(-4)). Thus our study revealed a significant increase of HLA-A31, A33, A19, B16, B53 and DRB1*03, DRB1*13 and DQB1*02 alleles in our patients. These markers could play a predisposing role in the development of NPC. In contrast, a decrease of HLA-B14, -B35 and DRB1*01 and DQB1*05 alleles was found suggesting a likely protective effect.

Lipid peroxidation and antioxidant system in the tumor and in the blood of patients with nasopharyngeal carcinoma.

Reactive oxygen species play a key role in cancer development by inducing and maintaining the oncogenic phenotypes of cancer cells. In this study, we examined lipid peroxidation and antioxidant enzymes activities in the blood and in the tumor of nasopharyngeal carcinoma patients. Plasma malondialdehyde, conjugated dienes, erythrocytes catalase, and superoxide dismutase activities have been measured in 30 untreated nasopharyngeal carcinoma patients and 30 controls on one hand. On the other hand, tumor malondialdehyde level, catalase, and superoxide dismutase activities have been measured in five nasopharyngeal carcinoma patients and compared with four controls. The lipid peroxidation was confirmed in the plasma by the high levels of malondialdehyde and conjugated dienes (p<0.001, respectively). Additionally, significantly higher concentrations of malondialdehyde were found in biopsies compared to the control group (p<0.001). In erythrocytes, superoxide dismutase activity was higher in patients than in controls (p<0.05), while it was unchanged in the tumor (p>0.05). Both erythrocytes and tumor catalase activities were significantly lower in patients than in controls (p<0.001, respectively). Statistical studies have shown a positive correlation between malondialdehyde level and IgA antibodies level against Epstein­Barr virus capsid antigen (p<0.05). In conclusion, we reported the presence of an oxidative stress in the blood and in the biopsies of nasopharyngeal carcinoma patients where Epstein­Barr virus seems to play a role.

Epstein-Barr virus-targeted immunotherapy for nasopharyngeal carcinoma.

Epstein-Barr virus (EBV) is constantly present in undifferentiated and poorly-differentiated nasopharyngeal cancer. Thus, tumour-associated viral antigens are potential targets for immunotherapy. Recently, both preclinical and early clinical studies have shown that various strategies can enhance EBV-specific immunity. Moreover, significant anti-tumour effect has been observed, and was generally correlated with biological response. The present review discusses the rational for EBV-targeted immunotherapy and summarises the latest developments in this area.

EBV latent membrane protein 1 abundance correlates with patient age but not with metastatic behavior in north African nasopharyngeal carcinomas.

BACKGROUND: Undifferentiated nasopharyngeal carcinomas are rare in a majority of countries but they occur at a high incidence in South China and to a lesser extent in North Africa. They are constantly associated with the Epstein-Barr virus (EBV) regardless of patient geographic origin. In North Africa, the distribution of NPC cases according to patient age is bi-modal with a large group of patients being around 50 years old (80%) and a smaller group below 25 years old. We and others have previously shown that the juvenile form of NPC has distinct biological characteristics including a low amount of p53 and Bcl2 in the tumor tissue and a low level of anti-EBV IgG and IgA in the peripheral blood. RESULTS: To get more insight on potential oncogenic mechanisms specific of these two forms, LMP1 abundance was assessed in 82 NPC patients of both groups, using immuno-histochemistry and semi-quantitative evaluation of tissue staining. Serum levels of anti-EBV antibodies were simultaneously assessed. For LMP1 staining, we used the S12 antibody which has proven to be more sensitive than the common anti-LMP1 CS1-4 for analysis of tissue sections. In all NPC biopsies, at least a small fraction of cells was positively stained by S12. LMP1 abundance was strongly correlated to patient age, with higher amounts of the viral protein detected in specimens of the juvenile form. In contrast, LMP1 abundance was not correlated to the presence of lymph node or visceral metastases, nor to the risk of metastatic recurrence. It was also independent of the level of circulating anti-EBV antibodies. CONCLUSION: The high amount of LMP1 recorded in tumors from young patients confirms that the juvenile form of NPC has specific features regarding not only cellular but also viral gene expression.

[Nonresponse to hepatits B vaccine in health care workers]. / La non reponse a la vaccination antihepatitique chez le personnel soignant.

The authors report the results of an investigation of witness cases realised in collaboration between Occupational Medecine Service and Immunology Laboratory of Hedi CHAKER University Hospital SFAX during the year 2000. The purpose was to search the genetic control of the HLA class I system for the non-response to hepatitis B vaccine and to evaluate the contribution of other favorite factors as tabac, sex, age. Thus, in a population of 32 healthy agents found nonresponders to hepatitis B vaccine by the titers of anti HBs antibody, we have performed the HLA-A, -B phenotypes by the technique of complement dependent microcytotoxicity. The frequency of studied HLA class I antigens, was compared for the non-responders group, to the frequency observed in witnesses group, done with 52 responders healthy agents. The rate of nonresponsiveness hepatitis B vaccine was evaluated up to 5 %. Statistically significant difference was observed for HLA A1 and-B44 markers showing fraquencies which were considerably higher in the non-responders than in witnesses.