Validation of Commercial SARS-CoV-2 Immunoassays in a Nigerian Population

Validated assays are essential for reliable serosurveys; however, most SARS-CoV-2 immunoassays have been validated using specimens from China, Europe, or U.S. populations. We evaluated the performance of five commercial SARS-CoV-2 immunoassays to inform their use in serosurveys in Nigeria. Four semiquantitative enzyme-linked immunosorbent assays (ELISAs) (Euroimmun anti-SARS-CoV-2 nucleocapsid protein [NCP] immunoglobulin G [IgG], Euroimmun spike SARS-CoV-2 IgG, Mologic Omega COVID-19 IgG, Bio-Rad Platelia SARS-CoV-2 Total Ab) and one chemiluminescent microparticle immunoassay (Abbott Architect SARS-CoV-2 IgG) were evaluated. We estimated the analytical performance characteristics using plasma from 100 SARS-CoV-2 PCR-positive patients from varied time points post-PCR confirmation and 100 prepandemic samples (50 HIV positive and 50 hepatitis B positive). The Bio-Rad assay failed the manufacturer-specified validation steps. The Euroimmun NCP, Euroimmun spike, and Mologic assays had sensitivities of 73.7%, 74.4%, and 76.9%, respectively, on samples taken 15 to 58 days after PCR confirmation and specificities of 97%, 100%, and 83.8%, respectively. The Abbott assay had 71.3% sensitivity and 100% specificity on the same panel. Parallel or serial algorithms combining two tests did not substantially improve the sensitivity or specificity. Our results showed lower sensitivity and, for one immunoassay, lower specificity compared to the manufacturers' results and other reported validations. Seroprevalence estimates using these assays might need to be interpreted with caution in Nigeria and similar settings. These findings highlight the importance of in-country validations of SARS-CoV-2 serological assays prior to use to ensure that accurate results are available for public health decision-making to control the COVID-19 pandemic in Africa. IMPORTANCE This study used positive and negative sample panels from Nigeria to test the performance of several commercially available SARS-CoV-2 serological assays. Using these prepandemic and SARS-CoV-2-positive samples, we found much lower levels of sensitivity in four commercially available assays than most assay manufacturer reports and independent evaluations. The use of these assays with suboptimal sensitivity and specificity in Nigeria or countries with population exposure to similar endemic pathogens could lead to a biased estimate of the seroprevalence, over- or underestimating the true disease prevalence, and limit efforts to stop the spread of SARS-CoV-2. It is important to conduct in-country validations of serological SARS-CoV-2 assays prior to their widespread use, especially in countries with limited representation in published assay validations

Cross-Reactivity of Two SARS-CoV-2 Serological Assays in a Setting Where Malaria Is Endemic

Background: Accurate SARS-CoV-2 serological assays are critical for COVID-19 serosurveillance. However, previous studies have indicated possible cross-reactivity of these assays, including in malaria-endemic areas.Methods: We tested 213 well-characterized pre-pandemic samples from Nigeria using two SARS-CoV-2 serological assays: Abbott Architect IgG and Euroimmun NCP IgG assay, both targeting SARS-CoV-2 nucleocapsid protein. To assess antibody binding strength, an avidity assay was performed on these samples and on plasma from SARS-CoV-2 PCR-positive persons.Results: Thirteen (6.1%) of 212 samples run on the Abbott assay and 38 (17.8%) of 213 run on the Euroimmun assay were positive. Anti-Plasmodium IgG levels were significantly higher among false-positives for both Abbott and Euroimmun; no association was found with active P. falciparum infection. An avidity assay using various concentratIons of urea wash in the Euroimmun assay reduced loosely-bound IgG: of 37 positive/borderline pre-pandemic samples, 46%, 86%, 89%, and 97% became negative using 2M, 4M, 5M, and 8M urea washes, respectively. The wash slightly reduced avidity of antibodies from SARS-CoV-2 patients within 28 days of PCR confirmation; thereafter avidity increased for all urea concentrations except 8M.Conclusions: This validation found moderate to substantial cross-reactivity on two SARS-CoV-2 serological assays using samples from a malaria-endemic setting. A simple urea wash appeared to alleviate issues of cross-reactivity

Possible Impact of Co-infections of Tuberculosis and Malaria on the CD4+ Cell Counts of HIV Patients in Nigeria

Background: This study focused on evaluating the possible impact of co-infections of tuberculosis and malaria on the CD4+ cell counts in HIV infected subjects. Methods: This is a cross sectional study. The subjects were drawn from three hospitals and a blood bank in LagosState. After due consent, blood samples were obtained from 69 subjects with single infections (HIV, TB, and Malaria), 34 subjects with multiple infections (HIV/Malaria, HIV/TB, Malaria/TB, HIV/TB/Malaria) and 24 blood donors (controls). The CD4+ cell counts of all the 127 blood samples were estimated using a FACS count. Results: Data obtained were analysed and a comparison of the results showed that the median CD4+ counts in all groups of subjects with HIV infections (whether single or co-infection) were similar and significantly lower than the median counts for the healthy control group as well as groups without HIV infection (malaria, TB and malaria/TB). Conclusion: Overall data further confirmed the progressive depletion of CD4+ cells in HIV infection while co-infections with TB and malaria did not have any impact on the CD4+ cells of HIV infected subjects. A larger prospective study is needed.Fond: Cette \ue9tude a \ue9t\ue9 consacr\ue9e \ue1 l'\ue9valuation de l'impact possible de co-infections de tuberculose et le paludisme sur les comptes de cellule CD4+ des sujets infect\ue9s du VIH. M\ue9thode: Ceci est une \ue9tude transversale. Les sujets ont \ue9t\ue9 choisis de trois diff\ue9rents h\uf4pitaux et une banque du sang dans l'Etat de Lagos. Apr\ue8s le consentement n\ue9cessaire, les \ue9chantillons de sang ont \ue9t\ue9 obtenus de 69 sujets avec les mono-infections (VIH, TB, et le Paludisme), 34 sujets avec les infections multiples (le VIH/PALUDISME, LE VIH/TB, LE Paludisme/TB, VIH/TB/le Paludisme) et 24 donneurs de sang (les contr\uf4les). les comptes de cellule CD4+ de tous les 127 \ue9chantillons de sang ont \ue9t\ue9 estim\ue9s utilisant une compte FACS. R\ue9sultats: les donn\ue9es obtenues ont \ue9t\ue9 analys\ue9es et une comparaison des r\ue9sultats a d\ue9montr\ue9 que le m\ue9dian des comptes CD4+ dans tous les groupes de sujets avec les infections de VIH (soit mono ou co-infection) \ue9taient similaires et significativement plus bas que les comptes m\ue9dianes pour le groupe de contr\uf4le sain de m\ueame que les groupes sans l'infection de VIH (le paludisme, TB et le paludisme/TB). Conclusion: les donn\ue9es g\ue9n\ue9rales ont confirm\ue9 le plus l'\ue9puisement progressif des cellules CD4+ dans l'infection de VIH pendant que les co-infections avec TB et le paludisme n'ont pas eu aucun impact sur les cellules CD4+ des sujets infect\ue9s de VIH. Une plus profonde \ue9tude sera n\ue9cessaire

Validation of xMAP SARS-CoV-2 Multi-Antigen IgG assay in Nigeria

Objective: There is a need for reliable serological assays to determine accurate estimates of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence. Most single target antigen assays have shown some limitations in Africa. To assess the performance of a multi-antigen assay, we evaluated a commercially available SARS-CoV-2 Multi-Antigen IgG assay for human coronavirus disease 2019 (COVID-19) in Nigeria. / Methods: Validation of the xMAP SARS-CoV-2 Multi-Antigen IgG assay was carried out using well-characterized SARS-CoV-2 reverse transcription polymerase chain reactive positive (97) and pre-COVID-19 pandemic (86) plasma panels. Cross-reactivity was assessed using pre-COVID-19 pandemic plasma specimens (213) from the 2018 Nigeria HIV/AIDS Indicator and Impact Survey (NAIIS). / Results: The overall sensitivity of the xMAP SARS-CoV-2 Multi-Antigen IgG assay was 75.3% [95% CI: 65.8%– 82.8%] and specificity was 99.0% [95% CI: 96.8%– 99.7%]. The sensitivity estimate increased to 83.3% [95% CI: 70.4%– 91.3%] for specimens >14 days post-confirmation of diagnosis. However, using the NAIIS pre-pandemic specimens, the false positivity rate was 1.4% (3/213). / Conclusions: Our results showed overall lower sensitivity and a comparable specificity with the manufacturer’s validation. There appears to be less cross-reactivity with NAIIS pre-pandemic COVID-19 specimens using the xMAP SARS-CoV-2 Multi-Antigen IgG assay. In-country SARS-CoV-2 serology assay validation can help guide the best choice of assays in Africa

Fluconazole resistant opportunistic oro-pharyngeal candida and non-candida yeast-like isolates from HIV infected patients attending ARV clinics in Lagos, Nigeria.

Background: Oro-Pharyngeal Candidiasis (OPC) continues to be considered the most common opportunistic fungal disease in HIV/AIDS patients globally. Azole antifungal agent has become important in the treatment of mucosal candidiasis in HIV patients. Presently, antifungal drug resistance is fast becoming a major problem particularly with the immune depleted population. Objectives: This study was designed to investigate the: existence of OPC, species distribution fluconazole susceptibility profile of yeast cells isolated from oral specimens of HIV/AIDS patients from Lagos Nigeria, between Oct. 2004 and June, 2005. Methodology: The venous blood samples were screened for HIV antibodies using the Cappillus HIV I and II test kit (Trinity Biotech Plc UK), and Genie II HIV I and II EIA kit (Bio-Rad France). The positive results were subsequently confirmed at the laboratory attached to each of the clinics, using the Nigerian Federal Ministry of Health approved algorithm. The samples from 213 (108 females and 105 males) HIV positive patients were plated onto SD agar. The isolates were identified by morphotyping, microscopy and speciated using germ tube test and battery of biochemical sugar fermentation and assimilation tests. Fluconazole agar diffusion susceptibility testing was carried out on each isolates. Results: Seventy-four (34.7%) isolates were recovered including one person with double isolates. Only 70(94.6%) of the isolates could be adequately speciated. Candida albicans 30 (40.5%) was the most frequently isolated species, the rest were non-albicans species, with the frequency of C. tropicalis › C. Krusei › C. glabrata and C. neoformans for species for species having up to 4 isolates. Four (30.8%) out of 13 isolates of C. tropicalis showed germ tube formation. While one C. albicans was germ-tube negative. Out of the 74 isolates tested for fluconazole sensitivity, 58(78.4%) were sensitive, MIC d” 8μg/ml, 9(12.1%) were susceptible Dose Dependant (SDD), MIC 16-32 μg/ml and 7(9.5%) were resistant, MICs e” 64μg/ml. Among the C. albicans isolates, 26(86.7%) were sensitive to fluconazole. The rank of susceptibility was C. albicans > C. tropicalis > C. Krusei for the most prevalent species. Conclusion: We conclude that fluconazole resistant strains of oro-pharyngeal yeast-like cells exist in about 9.5% of HIV/AIDS patients with the above stated species distribution. We therefore, highlight the need for routine antifungal susceptibility testing on HIV patients with cases of initial or repeat episodes of OPC. Keywords: Oropharyngeal Candida (yeast-like cells), HIV/AIDS and Fluconazole Resistance. African Health Sciences Vol. 8 (3) 2008: pp. 142-14

Fluconazole resistant opportunistic oro-pharyngeal candida and non-candida yeast-like isolates from HIV infected patients attending ARV clinics in Lagos, Nigeria

Background: Oro-Pharyngeal Candidiasis (OPC) continues to be considered the most common opportunistic fungal disease in HIV/AIDS patients globally. Azole antifungal agent has become important in the treatment of mucosal candidiasis in HIV patients. Presently, antifungal drug resistance is fast becoming a major problem particularly with the immune depleted population. Objectives: This study was designed to investigate the: existence of OPC, species distribution fluconazole susceptibility profile of yeast cells isolated from oral specimens of HIV/AIDS patients from Lagos Nigeria, between Oct. 2004 and June, 2005. Methodology: The venous blood samples were screened for HIV antibodies using the Cappillus HIV I and II test kit (Trinity Biotech Plc UK), and Genie II HIV I and II EIA kit (Bio-Rad France). The positive results were subsequently confirmed at the laboratory attached to each of the clinics, using the Nigerian Federal Ministry of Health approved algorithm. The samples from 213 (108 females and 105 males) HIV positive patients were plated onto SD agar. The isolates were identified by morphotyping, microscopy and speciated using germ tube test and battery of biochemical sugar fermentation and assimilation tests. Fluconazole agar diffusion susceptibility testing was carried out on each isolates. Results: Seventy-four (34.7%) isolates were recovered including one person with double isolates. Only 70(94.6%) of the isolates could be adequately speciated. Candida albicans 30 (40.5%) was the most frequently isolated species, the rest were non-albicans species, with the frequency of C. tropicalis > C. Krusei > C. glabrata and C. neoformans for species for species having up to 4 isolates. Four (30.8%) out of 13 isolates of C. tropicalis showed germ tube formation. While one C. albicans was germ-tube negative. Out of the 74 isolates tested for fluconazole sensitivity, 58(78.4%) were sensitive, MIC d" 8µg/ml, 9(12.1%) were susceptible Dose Dependant (S-DD), MIC 16-32 µg/ml and 7(9.5%) were resistant, MICs e" 64µg/ml. Among the C. albicans isolates, 26(86.7%) were sensitive to fluconazole. The rank of susceptibility was C. albicans > C. tropicalis > C. Krusei for the most prevalent species. Conclusion: We conclude that fluconazole resistant strains of oro-pharyngeal yeast-like cells exist in about 9.5% of HIV/AIDS patients with the above stated species distribution. We therefore, highlight the need for routine antifungal susceptibility testing on HIV patients with cases of initial or repeat episodes of OPC

Impact of Tuberculosis Co-Infection on the Level of PCV in HIV Infected Patients.

Background: It has been documented that HIV causes anemia in HIV infected patients. One of the commonest opportunistic infection in HIV patients is TB, and this has also been documented to cause anemia. In Nigeria, several cases of HIV and TB co-infections have been diagnosed. This study was carried out to determine any possible impact of TB co-infection on the level of HIV induced anemia. Methods: Anemia in this study was defined as PCV values below 30%. Three categories of subjects were recruited: 22 patients who had HIV infection only, 12 with HIV and co-infected with TB and 29 who are infected with TB only. A group of 10 apparently healthy subjects who were negative for HIV and TB were used as controls. These subjects were recruited from the Lagos University Teaching Hospital (LUTH), the Main land Hospital Yaba and the staff clinic of the Nigeria Institute of Medical Research all in Lagos, Nigeria . Blood samples were obtained from each of the enrolled subjects and the PCV levels were determined by the microhaematocrit method. All patients with TB diagnosis were sputum positive for AFB. CD4 cell count was determined for all HIV infected subjects using a FACScount. Results: PCV was significantly lower in all categories of subjects when compared with the control (0.05) from those co infected with HIV.Conclusion: Co-infection of HIV with TB did not worsen anemia in studied subjects. Keywords: HIV, Tuberculosis, Co-infection, Anemia.NQJHM Vol. 14 (2) 2004: pp. 115-11

POSSIBLE IMPACT OF CO-INFECTIONS OF TUBERCULOSIS AND MALARIA ON THE CD4+ CELL COUNTS OF HIV PATIENTS IN NIGERIA

Background: This study focused on evaluating the possible impact of co-infections of tuberculosis and malaria on the CD4+ cell counts in HIV infected subjects. Methods: This is a cross sectional study. The subjects were drawn from three hospitals and a blood bank in LagosState. After due consent, blood samples were obtained from 69 subjects with single infections (HIV, TB, and Malaria), 34 subjects with multiple infections (HIV/Malaria, HIV/TB, Malaria/TB, HIV/TB/Malaria) and 24 blood donors (controls). The CD4+ cell counts of all the 127 blood samples were estimated using a FACS count. Results: Data obtained were analysed and a comparison of the results showed that the median CD4+ counts in all groups of subjects with HIV infections (whether single or co-infection) were similar and significantly lower than the median counts for the healthy control group as well as groups without HIV infection (malaria, TB and malaria/TB). Conclusion: Overall data further confirmed the progressive depletion of CD4+ cells in HIV infection while co-infections with TB and malaria did not have any impact on the CD4+ cells of HIV infected subjects. A larger prospective study is needed

Comparison of one single-antigen assay and three multi-antigen SARS-CoV-2 IgG assays in Nigeria

Objectives: Determining an accurate estimate of SARS-CoV-2 seroprevalence has been challenging in African countries where malaria and other pathogens are endemic. We compared the performance of one single-antigen assay and three multi-antigen SARS-CoV-2 IgG assays in a Nigerian population endemic for malaria. Methods: De-identified plasma specimens from SARS-CoV-2 RT-PCR positive, dried blood spot (DBS) SARS-CoV-2 RT-PCR positive, and pre-pandemic negatives were used to evaluate the performance of the four SARS-CoV-2 assays (Tetracore, SARS2MBA, RightSign, xMAP). Results: Results showed higher sensitivity with the multi-antigen (81% (Tetracore), 96% (SARS2MBA), 85% (xMAP)) versus the single-antigen (RightSign (64%)) SARS-CoV-2 assay. The overall specificities were 98% (Tetracore), 100% (SARS2MBA and RightSign), and 99% (xMAP). When stratified based on <15 days to ≥15 days post-RT-PCR confirmation, the sensitivities increased from 75% to 88.2% for Tetracore; from 93% to 100% for the SARS2MBA; from 58% to 73% for RightSign; and from 83% to 88% for xMAP. With DBS, there was no positive increase after 15-28 days for the three assays (Tetracore, SARS2MBA, and xMAP). Conclusion: Multi-antigen assays performed well in Nigeria, even with samples with known malaria reactivity, and might provide more accurate measures of COVID-19 seroprevalence and vaccine efficacy