A hemagglutination-based, semi-quantitative test for point-of-care determination of SARS-CoV-2 antibody levels

Serologic, point-of-care tests to detect antibodies against 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. 200 COVID-19 patient and 200 control plasma samples were reconstituted with O-negative RBCs to form whole blood and added to dried viral-antibody fusion protein, followed by a stirring step and a tilting step, 3-minute incubation, and a second tilting step. The sensitivity for the hemagglutination test, Euroimmun IgG ELISA test and RBD-based CoronaChek lateral flow assay was 87.0%, 86.5%, and 84.5%, respectively, using samples obtained from recovered COVID-19 individuals. Testing pre-pandemic 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 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 minute 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 semi-quantitative information on neutralizing antibody titer in patients. The five-minute test may find use in determination of serostatus prior to vaccination, post-vaccination surveillance and travel screening.

Development of new antigens for serologic diagnosis of animal trypanosomosis and their use for epizootic monitoring

The purpose of the research is developing a method for obtaining erythrocyte antigens containing and not containing Trypanosoma equiperdum and T. evansi DNA, which can later be used in serological reactions to differentiate these types of Trypanosoma.Materials and methods. The studies were conducted in the Protozoology Laboratory and the Vyshnevolotsk Branch of the Federal State Budget Scientific Institution “Federal Scientific Centre VIEV RAS”, as well as livestock farms of the Russian Federation and other countries using clinical, microscopic, hematological, parasitological, biomolecular and serological methods.Results and discussion. Studies carried out for the first time have shown that it is possible to use erythrocyte antigens containing the T. equiperdum and T. evansi DNA obtained after 3-fold administration to mice and rabbits of a mixture of trypanosomal antigen with addition of 1.0 ml of an adjuvant (aluminum hydroxide), and bleeding of animals at 25 to 30 days. The formed precipitate was used as an antigen for serological tests. Experiments have shown that blood for preparation of positive serum can be taken when antibodies are in titers of 1:20 in the Prolonged Complement Fixation Test, and at least 1:400 in the Indirect Hemagglutination Test and ELISA, and for negative serum when horse blood serum reacts negatively with antigens of T. equiperdum and T. evansi in the Prolonged Complement Fixation Test, Indirect Hemagglutination Test and ELISA. The test systems of the Prolonged Complement Fixation Test, Indirect Hemagglutination Test and ELISA prepared by us with antigens containing and not containing T. equiperdum and T. evansi DNA resulted in creating a universal test system (Indirect Hemagglutination Test) for differentiating T. equiperdum from T. evansi.

Indirect Hemagglutination Test for Detection of Antibodies to Toxoplasma gondii in Venezuelan felids

Current knowledge of Toxoplasma gondii infection in Venezuelan ecosystems is limited. T. gondii is a ubiquitous intracellular protozoan parasite. Mammals and birds are intermediate hosts and felid species are definitive hosts. In most human altered habitats, the domestic cat is the predominant definitive host. Cats are important in the epidemiology of T. gondii infection because they are the only hosts that can excrete the environmentally resistant oocysts. Other carnivores can be infected by the consumption of tissue cysts when feeding on infected animals and by incidental ingestion of oocysts from environmental contamination. This study aimed to quantify the values of antibodies for T. gondii in blood serum of some felids species by means of the technique of Indirect Hemoagglutination. In the present study, seropositivity of T. gondii was determined in serum of 35 animals (22 stray cats and 13 wild cats) from Venezuela, South America. Antibodies to T. gondii were assayed by the indirect hemagglutination test and found in 21 of 22 (95.45 %) stray catstiters of 1:64 in four, 1:128 in four, 1:256 in one, 1:512 in one, 1:1024 in three, and 1:2048 or higher in eight. In 4 of 6 (66.67 %) ocelots titers of 1:64 in one, 1:256 in one, 1:1024 in one, and one with titers 1:2048. In 3 of 4 (75.00 %) jaguars titers of 1:512 in one, and two with titers 1:2048. The Kruskal-Wallis test showed a statistically significant difference between species (H = 6.983, p = 0.03).

Clinical and epidemiological characteristic of chronic brucellosis

Aim. To study clinical epidemiological and laboratory features of chronic brucellosis in the Republic of Tatarstan in ten-year aspect. Methods. 59 patients infected with various forms of brucellosis in 2007-2017 were examined. Clinical laboratory and instrumental diagnosis of brucellosis was confirmed by the immunoassay (EIA) with determination of IgM and IgG antibodies, passive hemagglutination test with a brucellar diagnosticum, Coombs test, Wright and Hedelson agglutination test. Results. Clinically 91 % of patients had asthenic-vegetative syndrome, 55 % - mild intoxication symptoms, 89 % - articular syndrome, 49 % - fibrositis. EIA revealed in 91 % of patients IgG (38 %) and IgM (53 %) antibodies to causative agents of brucellosis, 25 % of patients had positive Wright agglutination test, and 30 % - positive Hedelson agglutination test. In 9 % of cases the diagnosis was confirmed by Coombs test and in 26 % by passive hemagglutination test with brucellar diagnosticum. The retrospective analysis with clinical cases of patients with chronic brucellosis indicates introduced cases in 19 % (from the republics of Central Asia and Transcaucasia), local cases in 81 % (from the Republic of Tatarstan), their occupational character (57 %), the mixed (contact and alimentary) route of infection (21 %), and 64 % with clinically primary involvement of the musculoskeletal system and peripheral nervous system, i.e. prevalence of the mixed form of chronic brucellosis. Conclusion. Chronic brucellosis in the Republic of Tatarstan is characterized by high risk of introduced cases, occupational history, prevalence of the mixed route of infection in females and working-age patients; with the features of systemic disease involving the musculoskeletal and peripheral nervous system against the background of mild syndrome of intoxication and moderate asthenic-vegetative syndrome. Divergence of the results of serological diagnostics requires careful studying of duration of infection, features of the immune response in each case on follow-up.