Evaluation of the Impact of the COVID-19 Pandemic on Cystic Echinococcosis Indirect Hemagglutination Test Dynamics: A Single-center Experience.

OBJECTIVE: Cystic echinococcosis (CE) is one of the neglected tropical diseases announced by the World Health Organization. In the period entered with the Coronavirus disease-2019 pandemic, the fight against such diseases has become even more difficult. In our study, we aimed to make inferences about the effects of the pandemic on the diagnosis of the disease by evaluating the number and results of CE indirect hemagglutination test (IHA) before and during the pandemic. METHODS: The number of IHA test requests and positivity rates in the 30-month periods before and after March 11, 2020, when the first case was seen in our country, were evaluated retrospectively. Statistical analysis was made with SPSS version 23 (SPSS, Chicago, IL, USA) program. RESULTS: The results of 1444 patients before the pandemic and 870 patients during the pandemic period were examined. The difference between IHA positivity rates, which was found to be 18.49% before the pandemic and 14.6% during the pandemic, was statistically significant (p=0.016). The positivity rates of women and men were found to be statistically similar in both periods (pbefore=0.621, pafter=0.238). The age group with the highest IHA positivity rate was 20-39 in both periods, and the difference between the positivity rates of the age groups was statistically significant (p<0.001). CONCLUSION: A significant decrease was observed in the rate of IHA positivity during the pandemic period. The status of no increase in positivity rates despite a significant decrease in IHA tests makes us think that the diagnosis may be missed in some patients or that there could be disruptions in their follow-up. For this reason, in order to continue the fight successfully against CE, which is an important public health problem for our country, early diagnosis and regular follow-ups should be emphasized with educations, and the laboratory-clinician communication should be strengthened in order to use tests more efficiently.

[Latex Agglutination as an Alternative to the Hemagglutination Reaction of Influenza Viruses].

As an alternative to the classical method of erythrocyte hemagglutination, a latex agglutination assay based on the interaction of influenza viruses with the sialoglycoprotein fetuin immobilized on the surface of polystyrene microspheres has been developed. Twelve influenza A virus strains of different subtypes and two influenza B viruses of different lines were tested. Simultaneous titration of viruses using the classical hemagglutination test and the proposed latex agglutination assay showed similar sensitivity and a high degree of correlation (R = 0.94). The obtained microspheres can be used for titration of viruses that recognize and bind sialylated glycans as receptors. In particular, latex aggregation was also induced by the Newcastle disease virus.

The modulating effect of food composition on the immune system in growing ring-necked pheasants (Phasianus colchicus).

The decline in the population of ring-necked pheasants (Phasianus colchicus) in northwestern Germany since 2007 raises questions about the underlying causes. We therefore studied the growth and immune status of ring-necked pheasant chicks dependent on different feed composition. Here, 490 ring-necked pheasant chicks were raised in five groups up to nine weeks. While control groups C1 and C2 received sufficient crude protein (28%) and energy (12.5 MJ/Kg feed) according to current standards, group C2 was treated with cyclosporine eight hours prior to phythemagglutination (PHA) testing, serving as a positive immune suppressed control. Group V1 was fed with reduced protein (20%) but optimal energy content (12.5 MJ/Kg feed), group V2 was fed with sufficient protein (28%) and reduced energy content (10 MJ/kg feed) whereas group V3 was fed reduced crude protein (20%) and reduced energy content (10MJ/kg feed). On all chicks, health status was checked each week, and 20 birds of each group were weighed randomly per week. PHA-testing was performed on 12 birds of each group to study the in vivo non-specific activation of lymphocytes at week 2, 4, 6, 7, 8 and 9. In addition, hemolysis-hemagglutination-assay (HHA) was performed on each of the PHA-tested chicks, which were subsequently euthanized and dissected. Histopathologic examinations of 5 birds that were randomly chosen were performed. The PHA-test results demonstrate significant differences between control (C1, C2) and experimental groups (V1-V3) in several developmental stages. According to the HHA results, weekly testing detected a significant increase of titres per week in all groups without significant differences. Here, only hemagglutination and no lysis of samples was observed. It seems appropriate to conclude that during their first weeks of life, protein content is of higher importance in ring-necked pheasant chicks than energy intake. In particular T-cell response is significantly reduced, which indicate a weaker immune system resulting in a higher risk for clinical diseases. Therefore, we assume that protein i.e. insect availability is a highly important co-factor in the free-ranging population dynamics, and is linked to declines of the northwestern German population.

Evaluation of serum indirect haemagglutination test results of suspected cystic echinococcosis cases from 2009-2017.

OBJECTIVE: This study aims to evaluate the serological, radiological and epidemiological analysis of suspected cystic echinococcosis patients, and to assess the positivity rate in the region. Methods: The retrospective study was conducted at Bursa Uludag University Hospital, Turkey and comprised data from January 2009 to December 2017 related to patients of either gender with suspected cystic echinococcosis who underwent indirect haemagglutination testing. Demographic and clinical data of patients who tested positive were analysed. Statistical analysis was done using SPSS 23. RESULTS: Of the 3910 patients with a mean age of 41.6±19.35 years (range: 0-93 years) who underwent indirect haemagglutination testing, 692(17.7%) tested positive; 390(56.4%) females, and 302(43.6%) males. The highest seropositivity rate 107(15.5%) was observed in 2011, followed by 104(15%) in 2016. Seropositive cases were predominantly seen in those aged 40-49 years 131 (18.9%), followed by those aged 50-59 years 124 (17.9%). CONCLUSIONS: Cystic echinococcosis was found to be a public health problem in South Marmara region of Turkey.

Retrospective Determination of the Prevelense of Anti-Echinococcus granulosus Antibodies in Cystic Echinococcosis Pre-diagnosed Patients at Erciyes University Faculty of Medicine

Objective: Cystic echinococcosis (CE) is a parasitic disease that has been known for years in helminth diseases and it is important as human and animal health problem in many parts of the world and in our country due to economic losses. In this study, it was aimed to retrospectively evaluate the distribution of anti-E. granulosus-IgG antibodies in patients with pre-diagnosis of CE that referred to parasitology laboratory between January 2013-December 2018. Methods: Commercial kit was used for indirect hemaglutination (IHA), indirect fluorescent antibody test (IFAT) and Western blot (WB) methods using sera from patient samples was applied according to the kit proposal. In addition, patient materials for CAM, CSF and blood for which polymerase chain reaction (PCR)/QPCR tests were requested were examined. Results: Sera of the patients who were tested with at least one of the IHA, IFAT and WB methods or a combination of these methods, and 443 cases out of 2.283 cases were found to be E. granulosus seropositive. It was determined that 369 (62.03%) of 443 positive patients were female and 330 (37.97%) were male patients. Among these patients, 87 patients whose IFAT and/or IHA tests were negative were found to have positive results with the WB method. IFAT or IHA test results of 13 patients with negative WB tests were found to be positive. Four patients were identified with both tests positive but WB test results negative. In addition, 36 of 72 patients who underwent PCR/QPCR tests were found to be positive. Conclusion: As a result of a six-year retrospective screening, 22% of the cases were found to be positive, and it was concluded that the prevalence of CE is high and the use of a single test may be insufficient in the diagnosis of CE, therefore, test combinations will increase the sensitivity and reliability in reaching the correct diagnosis.

Correlation of Treponemal Chemiluminescent Microparticle Immunoassay Screening Test Signal Strength Values With Reactivity of Confirmatory Testing.

BACKGROUND: Automated chemiluminescent microparticle immunoassays (CMIAs) are the most common first step at high-volume laboratories for syphilis screening. If the initial screening test is reactive, 1 more treponemal test is required, resulting in increased cost. In this multicenter study, we aimed to determine the correlation between the CMIA signal-to-cutoff ratio (S/Co) and the confirmatory tests to reduce unnecessary confirmatory testing. METHODS: Eight hospitals from 5 provinces participated in this study. All laboratories used Architect Syphilis TP CMIA (Abbott Diagnostics, Abbott Park, IL) for initial screening. Treponema pallidum hemagglutination (TPHA), rapid plasma reagin (RPR), and fluorescent treponemal antibody absorption (FTA-ABS) were used as confirmatory tests according to the reverse or European Centre for Disease Prevention and Control algorithms. A receiver operating characteristic analysis was used to determine the optimal S/Co ratio to predict the confirmation results. RESULTS: We evaluated 129,346 serum samples screened by CMIA between January 2018 and December 2020. A total of 2468 samples were reactive; 2247 (91%) of them were confirmed to be positive and 221 (9%) were negative. Of the 2468 reactive specimens, 1747 (70.8%) had an S/Co ratio ≥10.4. When the S/Co ratios were ≥7.2 and ≥10.4, the specificity values were determined to be 95% and 100%, respectively. In a subgroup of 75 CMIA-positive patients, FTA-ABS was performed and 62 were positive. Among these FTA-ABS-positive patients, 24 had an S/Co ratio <10.4, and negative TPHA and RPR. CONCLUSIONS: We propose a potentially cost-effective reverse screening algorithm with a treponemal CMIA S/Co ratio ≥10.4, obviating the need for secondary treponemal testing in about 71% of the screening-reactive samples. This would substantially reduce the confirmatory testing volume and laboratory expenses. However, in high-risk group patients with CMIA positive results, S/Co ratio <10.4, and negative TPHA and RPR, FTA-ABS may be used for confirmation.

Evaluation and Correlation of Rabies Vaccine Potency Using the National Institute of Health, Rapid Focus Fluorescent Inhibition, and Passive Hemagglutination Tests.

Rabies vaccine preparations are quantitatively assayed for potency using the in-vivo challenge National Institute of Health (NIH), the main test that consumes a high number of animals, takes a long time, and has wide variability. The Rapid focus fluorescent inhibition (RFFIT) and the passive hemagglutination (PHA) tests, the two serologically based tests, were also used for such purpose. In this study, we aimed to evaluate and correlate the potency of the NIH, RFFIT, and PHA tests according to the World Health Organization (WHO) validity criteria, aiming to validate the use of RFFIT or PHA test as a substitute to the NIH test for determining the potency of commercially available Rabies vaccine preparations. The results showed that, the three tests can be successfully used; however, a higher correlation between RFFIT and NIH than PHA and NIH was recorded (Pearson correlation = 1). The potency of rabies vaccine preparations using NIH, RFFIT, and PHA were 3.73, 3.51, and 4.50, respectively. NIH is the main test for the determination of vaccine potency carried out by conducting 25 experiments and consuming about 5,000 mice compared to 1,200 mice used with RFFIT and 1,000 mice used with PHA test. Taken together, we concluded that (i) in some tested preparations, both RFFIT and PHA tests gave comparable results, and they can be used interchangeably; (ii) RFFIT could successfully replace NIH test, but not PHA; (iii) RFFIT and PHA tests are faster, more accurate, more economic, and more sensitive than NIH; nevertheless, PHA needs further investigations; and (iv) both RFFIT and NIH tests complement and reinforce each other as they provide a comprehensive picture of the product potency.

Assessment of the hemagglutinating activity of the Porcine orthorubulavirus.

Blue eye disease (BED) in pigs is caused by Porcine orthorubulavirus (PRV) of the Paramyxoviridae family. It is an endemic disease in swine production in the central region of Mexico and causes nervous signs and high mortality in suckling pigs, pneumonia in growing pigs, orchitis in boars and mummification during gestation. PRV hemagglutinates most red blood cells (RBCs) of domestic species. For serological diagnosis, the hemagglutination inhibition test is used, and in this test, guinea pig, bovine and chicken RBCs have been commonly used. In this investigation, hemagglutination with PRV was evaluated using the RBCs of seven domestic species (chicken, bovine, horse, pig, dog, guinea pig and rabbit). In the hemagglutination test, the following parameters were evaluated: temperature (25 °C and 37 °C), bottoms of the wells (V and U), erythrocyte concentration (0.5%, 0.75%, and 1%), and reading time (15, 30, 45, 60 and 90 min). Significant differences (P < 0.001) were found in most of the evaluated treatments. The best hemagglutination results were obtained with chicken, bovine and horse RBCs. The hemagglutination titer is higher (2 dilutions) when using chicken RBCs than when using bovine or horse RBCs. If chicken RBCs are used in the inhibition of hemagglutination, the test will be more sensitive, while it is more specific when bovine or horse RBCs are used. The hemagglutination readings are imprecise when using RBCs from dogs, pigs, guinea pigs and rabbits. RBCs from these species should not be used for the diagnosis or investigation of PRV.

A rapid and affordable point of care test for antibodies against SARS-CoV-2 based on hemagglutination and artificial intelligence interpretation.

Diagnostic tests that detect antibodies (AB) against SARS-CoV-2 for evaluation of seroprevalence and guidance of health care measures are important tools for managing the COVID-19 pandemic. Current tests have certain limitations with regard to turnaround time, costs and availability, particularly in point-of-care (POC) settings. We established a hemagglutination-based AB test that is based on bi-specific proteins which contain a dromedary-derived antibody (nanobody) binding red blood cells (RBD) and a SARS-CoV-2-derived antigen, such as the receptor-binding domain of the Spike protein (Spike-RBD). While the nanobody mediates swift binding to RBC, the antigen moiety directs instantaneous, visually apparent hemagglutination in the presence of SARS-CoV-2-specific AB generated in COVID-19 patients or vaccinated individuals. Method comparison studies with assays cleared by emergency use authorization demonstrate high specificity and sensitivity. To further increase objectivity of test interpretation, we developed an image analysis tool based on digital image acquisition (via a cell phone) and a machine learning algorithm based on defined sample-training and -validation datasets. Preliminary data, including a small clinical study, provides proof of principle for test performance in a POC setting. Together, the data support the interpretation that this AB test format, which we refer to as 'NanoSpot.ai', is suitable for POC testing, can be manufactured at very low costs and, based on its generic mode of action, can likely be adapted to a variety of other pathogens.

Melioidosis: Laboratory Investigations and Association with Patient Outcomes.

Melioidosis is an infection caused by the bacterium Burkholderia pseudomallei. The most common presentation is bacteremia occurring in 38-73% of all patients, and the mortality rate ranges from 9% to 42%. Although there is abundant data representing risk factors for infection and patient outcomes, there is limited information regarding laboratory investigations associated with bacteremia and mortality. We assessed a range of baseline and diagnostic investigations and their association with patient outcomes in a retrospective cohort study in Townsville, Australia. 124 patients' medical and laboratory records were reviewed between January 1, 1997 and December 31, 2020. Twenty-seven patients died and 87 patients were bacteremic. The presence of lymphopenia (< 1.5 × 109 cells/L) was the highest risk for bacteremia (relative risk [RR] 2.2; 95% CI: 1.3-3.7, P < 0.001). Factors associated with mortality included lymphopenia, (RR: 1.4; 95% CI: 1.2-1.6, P = 0.004); uremia (RR: 1.7; 95% CI: 1.1-2.5, P = 0.03); and an elevated international normalized ratio (RR: 1.5; 95% CI: 1.2-2.0, P = 0.006). Median incubation to positive blood culture result was 28 hours with 15/82 (18%) positive in ≤ 24 hours. For serological testing during admission only 53/121 (44%) were indirect hemagglutination assay positive, 67/120 (56%) enzyme immunoassay IgG positive, and 23/89 (26%) IgM positive. Simple baseline investigations at time of presentation may be used to stratify patients at high risk for both bacteremia and mortality. This information can be used as a decision aid for early intensive management.

A Hemagglutination-Based Semiquantitative Test for Point-of-Care Determination of SARS-CoV-2 Antibody Levels.

Serologic point-of-care tests to detect antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are an important tool in the COVID-19 pandemic. The majority of current point-of-care antibody tests developed for SARS-CoV-2 rely on lateral flow assays, but these do not offer quantitative information. To address this, we developed a novel antibody test leveraging hemagglutination, employing a dry card format currently used for typing ABO blood groups. Two hundred COVID-19 patient and 200 control plasma samples were reconstituted with O-negative red blood cells (RBCs) to form whole blood and added to dried viral-antibody fusion protein, followed by a stirring step and a tilting step, 3-min incubation, and a second tilting step. The sensitivities of the hemagglutination test, Euroimmun IgG enzyme-linked immunosorbent assay (ELISA), and receptor binding domain (RBD)-based CoronaChek lateral flow assay were 87.0%, 86.5%, and 84.5%, respectively, using samples obtained from recovered COVID-19 individuals. Testing prepandemic samples, the hemagglutination test had a specificity of 95.5%, compared to 97.3% and 98.9% for the ELISA and CoronaChek, respectively. A distribution of agglutination strengths was observed in COVID-19 convalescent-phase plasma samples, with the highest agglutination score (4) exhibiting significantly higher neutralizing antibody titers than weak positives (2) (P < 0.0001). Strong agglutinations were observed within 1 min of testing, and this shorter assay time also increased specificity to 98.5%. In conclusion, we developed a novel rapid, point-of-care RBC agglutination test for the detection of SARS-CoV-2 antibodies that can yield semiquantitative information on neutralizing antibody titer in patients. The 5-min test may find use in determination of serostatus prior to vaccination, postvaccination surveillance, and travel screening.

Laboratory Results of Cystic Echinococcosis in 2017 and 2018

Objective: This study aimed to retrospectively examine the indirect haemagglutination (IHA) test results of patients suspected of cystic echinococcosis (CE) and admitted to Bursa Uludag University Health Practice and Research Center Hospital. Methods: Serum samples in the serology laboratory of our hospital were evaluated using the commercial Cellognost® echinococcosis IHA (Siemens Healthcare Diagnostics, Marburg, Germany) test based on the manufacturer's recommendations. In the IHA test, ≥1:64 serum titres were accepted as positive. Results: Seropositivity was determined in 213 (19.9%) of 1.072 patients suspected of having CE by the IHA method. Of the patients with seropositivity, 120 (56.3%) were female and 93 (43.7%) were male. The highest positivity rate in both sexes was found in patients aged 20-29 years (22.5% in women; 14.1% in men). Conclusion: The results indicate that CE maintains its importance as a public health problem in Bursa as in Turkey.

[Conversion of serum anti-Schistosoma japonicum antibodies detected by immunological tests following treatment with praziquantel: a meta-analysis].

OBJECTIVE: To evaluate the conversion of serum antibodies against Schistosoma japonicum in humans and livestock detected by immunological tests following treatment with praziquantel. METHODS: The studies pertaining to serological tests of schistosomiasis japonica published from 1991 to 2020 were retrieved in electronic databases, including Chinese National Knowledge Infrastructure, WanFang Data, PubMed and ScienceDirect. Data were extracted from included studies. The publication bias was assessed with funnel plots using the software RevMan version 5.3, and the conversion of antibodies against S. japonicum was evaluated through meta-analysis. RESULTS: A total of 40 publications were included in the final meta-analysis, consisting of 33 Chinese publications and 7 English publications, and all immunological tests were performed with indirect hemagglutination test (IHA) and enzyme-linked immunosorbent assay (ELISA). Pooled analysis showed that the negative rates of serum anti-S. japonicum antibody were 45.36% [95% confidential interval (CI): (43.96%, 46.76%)] and 20.83% [95% CI: (19.69%, 21.97%)] detected by ELISA and IHA within 6 months post praziquantel treatment, 62.95% [95% CI: (61.59%, 64.31%)] and 55.61% [95% CI: (54.21%, 57.01%)] within 6 to 12 months after treatment and 85.92% [95% CI: (84.94%, 86.90%)] and 86.90% [95% CI: (85.95%, 87.85%)] over 12 months after treatment, respectively. CONCLUSIONS: The negative rate of the serum anti-S. japonicum antibody by IHA and ELISA increased with the time of post-treatment with praziquantel. The overall negative rates of anti-S. japonicum antibody detected by IHA and ELISA are low within 12 months post praziquantel treatment. However, a high negative rate of anti-S. japonicum antibody is detected if there is no new contact with infested water after 12 months of praziquantel treatment.

Genetic and Antigenic Characterization of Avian Avulavirus Type 6 (AAvV-6) Circulating in Canadian Wild Birds (2005-2017).

We describe for the first time the genetic and antigenic characterization of 18 avian avulavirus type-6 viruses (AAvV-6) that were isolated from wild waterfowl in the Americas over the span of 12 years. Only one of the AAvV-6 viruses isolated failed to hemagglutinate chicken red blood cells. We were able to obtain full genome sequences of 16 and 2 fusion gene sequences from the remaining 2 isolates. This is more than double the number of full genome sequences available at the NCBI database. These AAvV-6 viruses phylogenetically grouped into the 2 existing AAvV-6 genotype subgroups indicating the existence of an intercontinental epidemiological link with other AAvV-6 viruses isolated from migratory waterfowl from different Eurasian countries. Antigenic maps made using HI assay data for these isolates showed that the two genetic groups were also antigenically distinct. An isolate representing each genotype was inoculated in specific pathogen free (SPF) chickens, however, no clinical symptoms were observed. A duplex fusion gene based real-time assay for the detection and genotyping of AAvV-6 to genotype 1 and 2 was developed. Using the developed assay, the viral shedding pattern in the infected chickens was examined. The chickens infected with both genotypes were able to shed the virus orally for about a week, however, no significant cloacal shedding was detected in chickens of both groups. Chickens in both groups developed detectable levels of anti-hemagglutinin antibodies 7 days after infection.

A haemagglutination test for rapid detection of antibodies to SARS-CoV-2.

Serological detection of antibodies to SARS-CoV-2 is essential for establishing rates of seroconversion in populations, and for seeking evidence for a level of antibody that may be protective against COVID-19 disease. Several high-performance commercial tests have been described, but these require centralised laboratory facilities that are comparatively expensive, and therefore not available universally. Red cell agglutination tests do not require special equipment, are read by eye, have short development times, low cost and can be applied at the Point of Care. Here we describe a quantitative Haemagglutination test (HAT) for the detection of antibodies to the receptor binding domain of the SARS-CoV-2 spike protein. The HAT has a sensitivity of 90% and specificity of 99% for detection of antibodies after a PCR diagnosed infection. We will supply aliquots of the test reagent sufficient for ten thousand test wells free of charge to qualified research groups anywhere in the world.

Comparative Evaluation of the Efficacy of Indirect Hemagglutination Test and Radiological Methods in the Pre-diagnosis of Cystic Echinococcosis

Objective: Cystic echinococcosis (CE) is a common public health concern in Turkey. In this study, we investigated the agreement between the results of radiological imaging methods and serological tests through a 5-year retrospective evaluation in patients admitted to a university hospital with a suspicion of CE so as to determine the frequency of CE in the study region. Methods: The indirect hemagglutination test (IHA) results of 1.046 patients obtained from various clinics with the suspicion of CE between January 2014 and December 2018 were retrospectively analysed. Of these, patients with at least one radiological imaging report in the system (938 patients) were included in the study. Radiological imaging findings and IHA test results were compared and examined. Results: Seropositivity was detected by IHA test in 143 (15.2%) of 938 patients included in the study. The CE findings were recorded in at least one radiological imaging report in 130 (90.9%) of 143 patients with positive IHA test. At least one of the radiological imaging reports suggested presence of CE in 362 (38.5%) of all the patients. Conclusion: Thus, serological test and radiological imaging methods should be used in combination for the diagnosis of CE.

Clinical and laboratory impact of concomitant syphilis infection during acute HIV.

INTRODUCTION: Cognitive impairment has been reported in people living with HIV-1 (PLWH) with prior syphilis, while PLWH who present with incident syphilis have reduced blood CD4 T-lymphocyte and elevated HIV-1 RNA levels. However, the clinical, virological and neurocognitive effects of syphilis during acute HIV-1 (AHI) remain unknown. METHODS: Pre-antiretroviral therapy laboratory outcomes and neurocognitive performance in a four-test battery in the SEARCH10/RV254 AHI cohort were compared according to syphilis status, determined by serum Treponema pallidum haemagglutination (TPHA), Venereal Disease Research Laboratory (VDRL) and syphilis treatment history. Impaired cognitive performance was defined as having z-scores ≤ -1 in at least two tests or ≤ -2 in at least one test. RESULTS: Out of 595 AHI participants (97% male, median age of 26 years and estimated duration of HIV-1 infection of 19 days), 119 (20%) had history of syphilis (TPHA-positive), of whom 51 (9%) had untreated syphilis (TPHA-positive/VDRL-positive/without prior treatment). Compared with those without syphilis (TPHA-negative), individuals with untreated syphilis had higher CD8 T-lymphocyte levels but not higher plasma HIV-1 RNA or lower CD4 T-lymphocyte levels. Taking into account estimated duration of HIV-1 infection (P < 0.001), and later Fiebig stages (III-V) (P < 0.001), those with untreated syphilis had higher CD8 T-lymphocyte levels (P = 0.049). Individuals with any syphilis (TPHA-positive), but not untreated syphilis, had higher odds of impaired cognitive performance than those without (P = 0.002). CONCLUSIONS: During AHI, individuals with any history of syphilis (TPHA-positive) had poorer cognitive performance than those without syphilis. However, syphilis was not associated with worsened HIV disease measures as described in chronic infection.

A rapid, point-of-care red blood cell agglutination assay detecting antibodies against SARS-CoV-2.

The COVID-19 pandemic has caused significant morbidity and mortality. There is an urgent need for serological tests to detect antibodies against SARS-CoV-2, which could be used to assess past infection, evaluate responses to vaccines in development, and determine individuals who may be protected from future infection. Current serological tests developed for SARS-CoV-2 rely on traditional technologies such as enzyme-linked immunosorbent assays (ELISA) and lateral flow assays, which have not scaled to meet the demand of hundreds of millions of antibody tests so far. Herein, we present an alternative method of antibody testing that depends on one protein reagent being added to patient serum/plasma or whole blood with direct, visual readout. Two novel fusion proteins, RBD-2E8 and B6-CH1-RBD, were designed to bind red blood cells (RBCs) via a single-chain variable fragment (scFv), thereby displaying the receptor-binding domain (RBD) of SARS-CoV-2 spike protein on the surface of RBCs. Mixing mammalian-derived RBD-2E8 and B6-CH1-RBD with convalescent COVID-19 patient serum and RBCs led to visible hemagglutination, indicating the presence of antibodies against SARS-CoV-2 RBD. B6-CH1-RBD made in bacteria was not as effective in inducing agglutination, indicating better recognition of RBD epitopes from mammalian cells. Given that our hemagglutination test uses methods routinely used in hospital clinical labs across the world for blood typing, we anticipate the test can be rapidly deployed at minimal cost. We anticipate our hemagglutination assay may find extensive use in low-resource settings for detecting SARS-CoV-2 antibodies.