Presence of neutralizing SARS-CoV-2 antibodies in asymptomatic population of N'Djamena, Chad

INTRODUCTION

Neutralizing antibodies (NAbs) are an important specific defence against viral infections, as these antibodies bind to specific receptor(s) and block the viral entry. NAbs assessments are therefore useful in determining individual or herd immunity to SARS-CoV-2. This study aims to deepen the investigation by assessing the positivity rate of neutralizing anti-spike antibodies to understand the real protection of the studied population against SARS-CoV-2.

METHODS

This study involved 260 plasma samples from a larger cohort of 2,700 asymptomatic volunteer donors, enrolled between August and October 2021 in health facilities of N'Djamena. In this study four different kits and techniques including the pseudotype assay have been used and compared with detect the SARS-CoV-2 antibodies. Pseudotyped vesicular stomatitis virus (VSV), was used both the identify and measure the NAbs that to evaluate the performance of two cheaper and easy to use commercial kits, specific for the detection of receptor-binding domain antibodies (anti-RBD) against the SARS-CoV-2 spike protein.

RESULTS

The VSV spike neutralization assay showed that 59.0% (n = 59) samples were positive for NAbs with titers ranging from 1:10 to 1:4800. While 23 out the 41 negative NAbs samples were detected positive using anti-RBD (Abbott) test. Furthermore, a direct and significant strong correlation was found between NAbs and anti-RBD, specifically with Abbott kit. Taken together, the Roche and Abbott methods indicated agreement at the high concentrations of antibodies with the VSV-pseudovirus method. Abbott and Roche indicated a good sensitivity, but the Abbott system test appeared to have better specificity than the Roche test.

CONCLUSION

Our findings indicated a high presence of NAbs against SARS-CoV-2 spike protein among asymptomatic individuals in N'Djamena. This could be one of the reasons for the low severity of Covid-19 observed in this area, given the key role of NAbs in blocking SARS-CoV-2 infection.

[Clinical, diagnostic and evolutionary profile of peritoneal tuberculosis at the national reference general hospital of Ndjamena about 69 cases]

INTRODUCTION

Peritoneal tuberculosis is not uncommon in Chad. Its diagnosis of certainty is difficult and is based on the analysis of ascites fluid and abdominal ultrasound. Our aim was to contribute to the study of the various clinical, diagnostic and progressive aspects of peritoneal tuberculosis in the internal medicine department of the HGRN.

METHODOLOGY

This is a retrospective and prospective study spread over 39 months covering the period from January 2014 to March 2017 including all patients hospitalized for peritoneal tuberculosis in the internal medicine department of the HGRN. The diagnosis was made, on a bundle of anamnestic, clinical, ultrasound, cytological and evolutionary arguments.

RESULTS

During the study period, 69 patients were included, or 9.77% of all hospital admissions. The average age was 42 years (range 18 to 83 years). The female sex represented 52.2% of the cases. The main reasons for hospitalization were ascites (87% of cases), associated with fever (92.5% of cases). The clinical signs were dominated by abdominal pain, deterioration of general condition and transit disorders. The ascites fluid was citrus yellow, rich in lymphocytes (81.6% of cases) and protein (94.2% of cases). Abdominal ultrasound, performed in all patients, demonstrated ascites with deep, mesenteric lymphadenopathy, portal in 62.3% of cases and compartmentalized in 37.7% of cases. Tuberculosis treatment was started in all patients and the outcome was favorable in 65.2% of cases. We deplored 20.3% mortality; all were patients who were severely immunosuppressed with HIV.

CONCLUSION

Peritoneal involvement in tuberculosis is common in Chad. The diagnosis is not always easy, but the clinic associated with the exudative and lymphocytic characters of the ascites fluid as well as the abdominal ultrasound are elements which can direct towards a peritoneal localization of tuberculosis. The course is generally favorable under early treatment and well conducted.

[Clinical-Biological analyses and electrocardiographic follow-up of 104 cases of plasmodium falciparum malaria treated at Camp Kosseï in N'Djamena (Tchad)]

OBJECTIVE

The aim of this study was to assess the commonly accepted potential effects of Artemisinin-based combinaison therapy (ACT) on repolarization and QT.

METHOD

We realized a retrospective study, evaluating epidemiologic, clinical, biological and electrocardiographic data for patients treated for falciparum malaria, between August 31^st and November 3^rd, 2017 in the Pôle de santé unique on the Camp Kosseï of N'Djamena.

RESULTS

One hundred and four patients were included (28,6 years old [0 - 75 years], 72% male). All had fever (38,4 °C [36,6 - 41,5 °C]), asthenia, and main symptoms were headache and arthromyalgia (58%). No significant difference was noted after treatment concerning biological data (especially kaliemia: 3.81 versus 3.91 mmol/l, p = 0.154). There was no significant increase of QTc (415.8 versus 421.4 ms, p = 0.89) with the two ACT treatment used and no adverse events.

DISCUSSION

Population is essentially composed of Chadian men, often partly immunized, that can modify clinical presentation. French soldiers' medical follow up in military operations decreases contra-indications of ACT.

CONCLUSIONS

These results are in favor of a good cardiac tolerance of ACT with piperaquine and it should be proposed not to realize systematic ECG for the French soldiers in external operation when treated with ACT.