Avidity Index Research Articles

Immunosorbent assay for detection of Trypanosoma evansi infection in multiple host species using chimeric protein A/G conjugate

Surra caused by an extracellular hemoflagellate, Trypanosoma evansi, leads to severe economic loss to livestock productivity in India. Among the various mammalian pathogenic trypanosomes, T. evansi has the widest host range.Usually, species specific conjugates are used in conventional indirect immunosorbent assay (ELISA) for diagnosis of T. evansi infection in different animal species. The aim of the study was to explore the use of non-species specific conjugates viz., protein A, G and chimeric protein A/G instead of species specific conjugates for development of indirect ELISAs. These assays were used for detection of antibodies against T. evansi infection in multiple animal species viz., equine, cattle, buffalo, dog, pig and camel. The functional affinities of serum immunoglobulins of six different animal species with different conjugates were determined by estimation of relative avidity index (RAI). The species specific conjugate based whole cell lysate- T. evansi antigen ELISA was considered as reference assay for comparison of sensitivity and specificity of non-species specific conjugates based ELISAs optimized in the present study. Data showed that serodiagnosis of T. evansi can be carried out by using chimeric protein A/G conjugate in multiple hosts viz., equine, buffalo, camel, pig and dog; protein G conjugate in equine and buffalo and protein A conjugate in camel, pig and dog. The relative diagnostic sensitivity and specificity for chimeric protein A/G conjugate varied from 60 to 100% and 79–100%, respectively for different livestock species. This approach might be helpful in monitoring and surveillance of T. evansi infection in multiple hosts in particular when host specific secondary antibody conjugates are not available. Investigations should be made in wild animals and other warm-blooded vertebrates to validate this hypothesis.

Herpes Simplex Virus Type 2 (HSV-2) and Cytomegalovirus (CMV) among Women with Macerated Stillbirth: A Cross-Sectional Hospital-Based Study from Mwanza, Tanzania.

Background Stillbirth adversely affects pregnancy outcomes in low- and middle-income countries (LMICs). Viral infections have been implicated as one of the causes of stillbirths. Despite high rates of stillbirths and high viral prevalence in LMICs, there is limited information regarding their association. This study investigated the magnitude of herpes simplex 2 virus (HSV-2) and human cytomegalovirus (HCMV) among women with macerated stillbirth. Methods A cross-sectional hospital-based study was conducted involving 279 women with macerated stillbirth between July and August 2018 at different health facilities in Mwanza, Tanzania. Detection of HSV-2 was done by immunochromatographic test while that of HCMV was done using enzyme-linked immunosorbent assay (ELISA). Descriptive data analysis was done using STATA version 13. Results A total of 28 (10.04%, 95% CI: 6.8-13.9) tested positive for HSV-2 IgG antibodies with only 4 (1.43%, 95% CL: 0.3-2.8) testing positive for HSV-2 IgM antibodies. HCMV IgG antibodies were detected in 131 (77.98%, 95% CI: 71-84) of 168 women tested. By multivariate logistic regulation analysis, advanced age (OR: 0.93, 95% CI: 0.87-0.99, p = 0.025) was significantly associated with negative HSV-2 IgG antibodies. By log multinomial regression analysis, only urban residence (RRR.4.43: 95% CI 1.53-12.80, p = 0.006) independently predicted HCMV IgG seropositivity among women with stillbirth. Twenty-one (30.9%) of women with positive HCMV IgG antibodies had low avidity index (<40%) indicating recent infection. Conclusion Significant proportion of women with macerated stillbirth residing in urban and with low age have HCMV and HSV antibodies, respectively. This calls for the need to consider introducing screening of these infections in the Tanzanian antenatal package and further studies to explore the role of these viruses in causing stillbirth in Tanzania.

Humoral immunity in reconvalescents and persons vaccinated against COVID-19: a comparative assessment of the main indices of the humoral immune response

Specific humoral immunity to SARS-CoV-2 develops due to the formation of neutralizing IgG, which can primarily block the receptor-binding domain of the viral S-protein. The duration of post-infection immunity, as well as avidity of circulating antibodies, play an important role in this process. The aim of this work was to evaluate the amounts of antibodies to SARS-CoV 2 S-protein, their avidity and neutralizing activity in the studied samples of the post-COVID patients versus vaccinated seropositive individuals. Materials and methods. A sample of 113 individuals was studied, which consisted of three experimental groups, i.e.: recovered, vaccinated, as well as recovered and vaccinated persons. Blood serum specimens of the individuals were studied for specific IgG to SARS-CoV-2, along with determination of their quantities (BAU/mL) using Vector-Best kits (Novosibirsk, Russia). The avidity index was determined using a kit manufactured by MedipalTech (Dubna, Russia). Neutralizing ability of the antibodies was assayed by means of ELISA with diagnostic kits from MedipalTech (Dubna, Russia), which resulted into percentage of neutralized S-proteins to RBD. Results. The average levels of IgG did not show significant differences between reconvalescents and vaccinated persons. However, both indicators were significantly lower than those from the groups who recovered from the disease and were vaccinated. A cyclic change in the numbers of antibodies was observed, along with most intensive drop in the level of immunoglobulins over first four months after the illness or vaccination. Despite initially similar levels of immune parameters in both groups, the decline of this index in vaccinated group was significantly higher than in the recovered group, thus allowing us to conclude that the amounts of specific antibodies in this group was shown to be decreased to zero levels as soon as by the 10th month. IgG index among the recovered and vaccinated groups remained unchanged for the entire anamnestic period. Avidity index of the antibodies in vaccinated individuals was higher than in recovered individuals. Meanwhile, this index in both groups was characterized by stable increase over the observation period of 7 to 11 months. The highest levels of antibodies and their avidity were noted in the group of recovered and vaccinated individuals, due to the most complete activation of the immune system. A straight-line trend was revealed for the decreasing index of neutralizing activity during the considered time period. The overall pattern of thee results shows that the neutralizing activity of antibodies is largely determined by the amounts of SARS-CoV-2-specific immunoglobulins. Thus, the time dynamics of antibodies to SARS-CoV-2 in various groups of examined individuals was revealed. Direct correlation was established between the neutralizing activity and amounts of immunoglobulins, as well as the role of vaccination for increased avidity of antibodies.

Low quantity and quality of anti-spike humoral response is linked to CD4 T-cell apoptosis in COVID-19 patients

In addition to an inflammatory reaction, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)-infected patients present lymphopenia, which we recently reported as being related to abnormal programmed cell death. As an efficient humoral response requires CD4 T-cell help, we hypothesized that the propensity of CD4 T cells to die may impact the quantity and quality of the humoral response in acutely infected individuals. In addition to specific immunoglobulins (Ig)A, IgM, and IgG against SARS-CoV-2 nucleocapsid (N), membrane (M), and spike (S1) proteins, we assessed the quality of IgG response by measuring the avidity index. Because the S protein represents the main target for neutralization and antibody-dependent cellular cytotoxicity responses, we also analyzed anti-S-specific IgG using S-transfected cells (S-Flow). Our results demonstrated that most COVID-19 patients have a predominant IgA anti-N humoral response during the early phase of infection. This specific humoral response preceded the anti-S1 in time and magnitude. The avidity index of anti-S1 IgG was low in acutely infected individuals compared to convalescent patients. We showed that the percentage of apoptotic CD4 T cells is inversely correlated with the levels of specific IgG antibodies. These lower levels were also correlated positively with plasma levels of CXCL10, a marker of disease severity, and soluble Fas ligand that contributes to T-cell death. Finally, we found lower S-Flow responses in patients with higher CD4 T-cell apoptosis. Altogether, these results demonstrate that individuals with high levels of CD4 T-cell apoptosis and CXCL10 have a poor ability to build an efficient anti-S response. Consequently, preventing CD4 T-cell death might be a strategy for improving humoral response during the acute phase, thereby reducing COVID-19 pathogenicity.

Intranasal and Intramuscular Immunization with Outer Membrane Vesicles from Serogroup C Meningococci Induced Functional Antibodies and Immunologic Memory

ABSTRACT Background Immunization is the key to prevent invasive meningococcal disease (IMD), caused by Neisseria meningitidis. Outer membrane vesicles (OMVs) can be used as meningococcal antigens. Methods Isogenic mice A/Sn (H2a) were immunized with low antigenic doses of OMVs of an N. meningitidis C:2a:P1.5 strain, via intranasal/intramuscular route, adjuvanted by cholera toxin subunit B (CTB) or via intramuscular route only, adjuvanted by aluminium hydroxide (AH). Mice were followed until old age and humoral and cellular responses were assessed by ELISA, Immunoblotting, Dot-blot, Serum-bactericidal assay, Immunohistochemistry and ELISpot. Results OMV+CTB and OMV+AH groups presented statistically higher antibodies titers, which persisted until middle and old ages. IgG isotypes point to a Th2 type of response. Avidity indexes were considered high, regardless of adjuvant use, but only groups immunized with OMVs and adjuvants (OMV+CTB and OMV+AH) presented bactericidal activity. The antibodies recognized antigens of molecular weights attributed to porin and cross-reactivity proteins. Although the spleen of old mice did not present differences in immunohistochemistry marking of CD68+, CD4+, CD79+ and CD25+ cells, splenocytes of immune groups secreted IL-4 and IL-17 when stimulated with OMVs and meningococcal C polysaccharide. Conclusion We concluded that both adjuvants, CTB and AH, improved the immunogenicity of low doses of OMVs and contributed to a persistent immune response. Even though AH is well established in the vaccinology area, CTB seems to be a promising adjuvant candidate for meningococcal vaccines: it is suitable for mucosal delivery and supports a Th2 type of response. Therefore, OMVs are still a relevant vaccine platform.

Human cytomegalovirus (HCMV) long-term shedding and HCMV-specific immune response in pregnant women with primary HCMV infection.

Human cytomegalovirus (HCMV) shedding has been extensively investigated in newborns and in young children, however, much less is known about it in immunocompetent adults. Shedding of HCMV was investigated in saliva, vaginal secretions and urine of pregnant women experiencing primary infection along with the development of the HCMV-specific immune response. Thirty-three pregnant women shed HCMV DNA in peripheral biological fluids at least until one year after onset of infection, while in blood HCMV DNA was cleared earlier. Significantly higher levels of viral load were found in vaginal secretions compared to saliva and urine. All subjects examined two years after the onset of infection showed a high avidity index, with IgM persisting in 36% of women. Viral load in blood was directly correlated with levels of HCMV-specific IgM and inversely correlated with levels of IgG specific for the pentameric complex gH/gL/pUL128L; in addition, viral load in blood was inversely correlated with percentage of HCMV-specific CD4+ and CD8+ expressing IL-7R (long-term memory, LTM) while viral load in biological fluids was inversely correlated with percentage of HCMV-specific CD4+ and CD8+ effector memory RA+(TEMRA). In conclusion, viral shedding during primary infection in pregnancy persists in peripheral biological fluids for at least one year and the development of both antibodies (including those directed toward the pentameric complex) and memory T cells are associated with viral clearance.

Spontaneous abortion among Toxoplasma gondii IgG seropositive women: Molecular detection, genotype identification, and serological assessment with conventional ELISA and avidity ELISA.

It has been generally believed that women who exposed to Toxoplasma gondii before pregnancy and have anti-T. gondii IgG antibody are immunized and their newborns will be protected from congenital infection. This study is aimed to investigate the role of T. gondii infection in spontaneous abortion through serological and molecular methods in southern Iran. Blood samples were taken from 50 spontaneously aborted mothers and anti-T. gondii antibodies were assessed using conventional enzyme-linked immunosorbent assay (ELISA) and avidity ELISA methods. The placenta and blood samples of aborted women were used for detection of the parasite's DNA by polymerase chain reaction (PCR) method targeting the RE gene. The parasite genotypes were determined by PCR-restriction fragment length polymorphism (RFLP) method using SAG3 and GRA6 genes. IgG antibody was detected in 28% (14/50) of mothers, but all samples were negative for IgM antibody. In the avidity ELISA test, 26% (13/50) of the samples had a high avidity index, suggesting chronic infection, while a low avidity index was detected in one case (2%), which suggests acute infection. The parasite's DNA was detected in 18% (9/50) and 14% (7/50) of blood and placenta samples, respectively. All DNA positive samples were IgG positive. All isolates were belonged to the T. gondii type III genotype. The results suggest that T. gondii seropositive women are not protected from congenital transmission. However, the results should be interpreted cautiously until further studies will be confirmed these results.

Different levels of humoral and cellular immunity to varicella-zoster virus in seropositive healthcare workers

BackgroundThere have been occasional reports on varicella infection among healthcare workers (HCWs) despite varicella-zoster virus (VZV) seropositivity. We compared the levels of humoral and cellular immunity to VZV in seropositive HCWs who had acquired immunity by natural infection or vaccination. MethodsSeropositive healthy HCWs with an apparent history of varicella or VZV vaccination once or twice were recruited. Their samples were assessed for anti-VZV IgG levels, the relative avidity index (RAI), and the frequencies of VZV-specific cytokine-producing or polyfunctional CD4+ or CD8+ T cells. ResultsA total of 75 seropositive HCWs (29 with a history of varicella, 25 vaccinated once, and 21 vaccinated twice) were assessed for humoral immunity. Cellular responses could be analyzed in 59 (28, 21, and 10 in the respective groups). The anti-VZV IgG level, RAI, and memory CD4+ T cell responses were significantly higher in the past infection group than in the vaccinated once group. The RAI levels were significantly higher in the past infection group than in the vaccinated twice group. ConclusionSeropositive HCWs without a varicella history, especially those who received the vaccine only once, had significantly lower levels of immune responses to VZV. Such HCWs might need to comply with airborne precautions.

The study of flaviviruses and Chikungunya virus seroprevalence in Nicaragua — virus-specific antibody avidity assay as a tool for differential diagnosis

Introduction. Arboviral infections are a rising public health concern not only for some individual countries, but also for the entire world due to the repeated outbreaks over the past decade.The aim was to conduct a seroprevalence study of Dengue (DENV), Zika (ZIKV), Yellow fever (YFV) and Chikungunya (CHIKV) viruses using a limited number of samples in Nicaragua.Materials and methods. Total 200 serum samples collected previously in Nicaragua were analyzed simultaneously. Commercially available diagnostic kits, as well as in-house methods were used. The avidity of antibodies (IgG) in positive serum samples was assessed after the treatment with 8M urea.Results. 85 serum samples (42.5%) contained IgG antibodies to one or several viruses simultaneously. IgG antibodies only to one virus were detected in 46 serum samples (23%) with the avidity index (AI) ≥ 30%. Among 39 samples (19.5%) that contained IgG antibodies to several viruses, only in 19 samples (9.5%) IgG antibodies with high AI (≥ 30%) to several viruses were detected. In 16 serum samples (8.0%), IgG antibodies to DENV with a high AI and antibodies to ZIKV and/or YFV with a low AI 30% were detected.Discussion. The results obtained in ELISA testing were corrected, since only IgG antibodies with a high AI confirm the past infection. The analysis of the specific IgG antibody avidity helped not only to confirm the cases of combined or sequential infection in the past, but also to discriminate the cross-reactive IgG antibodies induced by closely related DENV, ZIKV and YFV. The presence of cross-reactive IgG antibodies, on the one hand, make it difficult to determine the real seroprevalence of flavivirus infections, and, on the other hand, may increase the risk of antibody-dependent enhancement (ADE) of the disease, which is well-known for the secondary Dengue fever and for the consecutive infection with DENV and ZIKV.Conclusion. The analysis of virus-specific antibody avidity made it possible not only to distinguish recent from the past infection, but also to discriminate the cross-reactive antibodies with the low avidity.

Recent HIV infections: evaluation of a simple identification score for newly diagnosed patients.

ABSTRACTOBJECTIVE Recognize incident infection to better characterize the groups that fuel HIV epidemic. We propose a simple score to identify recent infections among newly diagnosed patients as a HIV surveillance tool.METHODS Newly diagnosed patients were defined as recent infections when a negative serological test in the previous year was available. Laboratory tests, such as the avidity index (Bio-Rad, according to the CEPHIA protocol), chemiluminescent intensity (CMIA, architect, Abbott), and the nucleotide ambiguity index of partial pol sequences were used as proxies of recency. A simple score based on clinical symptoms of acute retroviral syndrome during the previous year, CD4+ T cell count, and viral load at admission was tested to assess the predictive power, using receiver operating characteristic (ROC) curves, to identify recent cases of infection.RESULTS We evaluated 204 recently diagnosed patients who were admitted to the Ambulatório de Referência em Moléstias Infecciosas de Santo André (Santo André Reference Infectious Diseases Outpatient Clinic), in the metropolitan region of São Paulo, Brazil, recruited between 2011 and 2018. An HIV-negative test in the year prior to enrollment was documented in 37% of participants. The proportion of cases classified as recent infections (less than one year), according to the laboratory proxies were: 37% (67/181) for an avidity index < 40%, 22% (30/137) for a CMIA < 200, and 68% (124/181) for an ambiguity index < 0.5%. Using different combinations of recency definitions, our score showed an area under the ROC curve from 0.66 to 0.87 to predict recency.CONCLUSIONS Using data from patients’ interviews and routine laboratory tests at admission, a simple score may provide information on HIV recency and thus, a proxy for HIV incidence to guide public policies. This simple for the Brazilian public health system and other low- and middle-income countries.

Australian Aboriginal Otitis-Prone Children Produce High-Quality Serum IgG to Putative Nontypeable Haemophilus influenzae Vaccine Antigens at Lower Titres Compared to Non-Aboriginal Children.

BackgroundNontypeable Haemophilus influenzae (NTHi) is the most common bacterial otopathogen associated with otitis media (OM). NTHi persists in biofilms within the middle ears of children with chronic and recurrent OM. Australian Aboriginal children suffer exceptionally high rates of chronic and recurrent OM compared to non-Aboriginal children. NTHi protein vaccines comprised of antigens associated with both adhesion and persistence in a biofilm are under development and could be beneficial for children with chronic and recurrent OM. Understanding the ontogeny of natural antibody development to these antigens provides insight into the value of vaccinating with particular antigens.MethodsAn in-house multiplex fluorescent bead immunoassay was used to measure serum IgG titres and avidity for three putative vaccine antigens: recombinant soluble PilA (rsPilA), ChimV4, and outer membrane protein 26 (OMP26) in sera from Australian Aboriginal otitis-prone children (n=77), non-Aboriginal otitis-prone children (n=70) and non-otitis-prone children (n=36). Serum IgG titres were adjusted for age, and geometric mean concentrations (GMCs) were compared between groups using a univariate analysis model. Antibody avidity was calculated as a relative avidity index and compared between groups using ANOVA.ResultsAustralian Aboriginal otitis-prone children had lower serum IgG titres to rsPilA and ChimV4 than non-Aboriginal otitis-prone children (p<0.001), and non-otitis-prone children (p<0.020). No differences were observed between serum IgG titres from non-Aboriginal otitis-prone children and non-otitis-prone children. There were also no differences in the proportion of high avidity IgG specific for these antigens between these groups. Serum IgG titres to OMP26 were similar between all groups (p>0.670) although otitis-prone children had a higher proportion of high avidity antibodies to this antigen.ConclusionsAustralian Aboriginal otitis-prone children had lower serum IgG titres to 2/3 major NTHi vaccine candidate antigens, suggesting these children are unable to develop persistent IgG responses due to repeated NTHi exposure. These reduced IgG titres may relate to earlier and more frequent exposure to diverse NTHi strains in Aboriginal children through carriage or infection. These data suggest that Aboriginal children may benefit from immunisation with vaccines containing these antigens to increase titres of protective antibodies.

The effects of simultaneous foot-and-mouth disease and Escherichia coli vaccination on the immunity of pregnant cows and their calves

Fighting against infectious diseases with almost 18 million cattle spread over a wide geographical area is troublesome economically and physically. The administration of different vaccines simultaneously during the foot-and-mouth disease (FMD) vaccination campaign will help reduce both the vaccine stress of animals and the field veterinarians’ workload. Diarrhea due to Escherichia coli (E. coli) is a significant problem and a major cause of mortality in calves, and thus, simultaneous application of FMD and E. coli vaccines to dams would prove efficient in field conditions. This study aimed to investigate the effect of simultaneous administration of four different locally produced gel and oil adjuvant inactivated E. coli vaccines with locally produced oil adjuvant inactivated FMD vaccine on neutralizing antibody levels and the properties of the antibodies in late-term pregnant dams and their calves. For this purpose, seven to eight-month-old pregnant dams (n = 146) were divided into two main groups to receive two doses (single and booster), or only single dose (no booster). FMD neutralizing antibody titers were evaluated by a virus neutralization test against serotype A, O, and Asia1. In addition, the properties of antibodies against serotype A were assessed by isotype and avidity ELISAs. E. coli antibodies were measured by the hemagglutination inhibition test. Results of the study revealed no safety problems in any dams after the vaccinations. On day 42, calves of the dams vaccinated simultaneously had higher neutralizing antibody titers against three serotypes than the calves of only FMD vaccinated dams. IgG1/IgG2 ratio was higher in single-dose groups than booster-dose groups against serotype A in calves. The avidity index was detected over the threshold value (24.5%). A positive correlation was found in the transmission of maternal antibodies from mothers to calves in simultaneous administration groups. In conclusion, during the FMD vaccine campaigns, FMD and E. coli vaccines can be simultaneously applied to dams in the 7th and 8th months of gestation. Results of this study has led to the inclusion of simultaneous application of FMD and E. coli vaccines in the ‘Animal Disease and Animal Movement Control Program-2018′ and these two vaccines have been applied in the field ever since as a solution for field veterinarians to save time and labor during vaccination.

Immunological Memory and Affinity Maturation After Vaccination in Patients With Propionic Acidemia.

Earlier studies have recommended routine childhood immunization in patients with propionic acidemia (PA); however, the literature presents insufficient data on the response to vaccines, notably specific IgG concentrations and avidity maturation, after measles, mumps, rubella (MMR), and diphtheria/tetanus (DiphtTe) vaccinations in this population. In patients with PA, cellular and humoral changes of the immune system (e.g. a decreased CD4+ T cell count, with a reversal of CD4/CD8 T cell ratio, a deficient gamma-globulin fraction, and in one case a decreased lymphocyte blastogenesis) have been reported. Former reports also detected pancytopenias accompanying febrile infections in PA patients. In the current study, we analyzed vaccine-specific IgG concentrations and avidity maturation after MMR and DiphtTe vaccinations in 10 patients with PA. Compared to gender and age matched controls, all 10 had protective IgG concentrations for at least one tested antigen, and in 6 out of 10 patients high relative avidity indices for measles and rubella were detected. In summary, the present study revealed a sufficient immune response and outcome, indicating an acceptable humoral memory in patients with PA after booster vaccinations.

Association Between First-Trimester Maternal Cytomegalovirus Infection and Stillbirth: A Prospective Cohort Study.

BackgroundGiven that the time lag between cytomegalovirus (CMV) screening and diagnosed testing, a better knowledge of the association between pregnant women with CMV screening test positive and stillbirth in an epidemiological perspective was required to assist people being counseled reframe their pregnancy and birth plans based on the magnitude of the risk.MethodsThis study recruited 44048 eligible pregnant women from March 13, 2013 to December 31, 2019. Serological tests including CMV-specific IgM and IgG, and IgG avidity index were used to screen for maternal CMV infection and were measured by automated chemiluminescence immunoassay. The association was assessed using the inverse probability of group-weighted multivariate-adjusted log-binomial models.ResultsA total of 540 infants ended with a stillbirth (12.3 per 1000 pregnancies), and 2472 pregnancies with maternal CMV infection were screened out (56.1 per 1000 pregnancies) among all eligible pregnancies. In the comparison analysis, 326 infants ended with a stillbirth (86.6 per 1000 pregnancies) in the maternal CMV infection group compared with 214 infants (7.8 per 1000 pregnancies) in the group where mothers were not infected with CMV (RR 12.17; 95% CI 9.43–15.71). After excluding the pregnancies of stillbirth with birth defects, a strong association between the two groups was still observed (RR 9.38; 95% CI 6.92–12.70).ConclusionOur findings quantified the risk of a woman having a baby with stillbirth if she had a positive serologic CMV screening test in her first trimester, and supported the value of using CMV serologic tests as part of regular testing in pregnant women.Trial registrationRegistered in Chinese Clinical Trial Registry Center; registration number, ChiCTR1800016635; registration date, 06/14/2018 (Retrospectively registered); URL of trial registry record, https://www.chictr.org.cn/showproj.aspx?proj=28300.

Avidity of IgG to SARS-CoV-2 RBD as a Prognostic Factor for the Severity of COVID-19 Reinfection.

The avidity index (AI) of IgG to the RBD of SARS-CoV-2 was determined for 71 patients with a mild (outpatient) course of COVID-19, including 39 primarily and 36 secondarily reinfected, and 92 patients with a severe (hospital) course of COVID-19, including 82 primarily and 10 secondarily infected. The AI was shown to correlate with the severity of repeated disease. In the group of outpatients with a mild course, the reinfected patients had significantly higher median AIs than those with primary infections (82.3% vs. 37.1%, p < 0.0001). At the same time, in patients with a severe course of COVID-19, reinfected patients still had low-avidity antibodies (median AI of 28.4% vs. 25% in the primarily infected, difference not significant, p > 0.05). This suggests that the presence of low-avidity IgG to RBD during reinfection is a negative prognostic factor, in which a patient’s risk of developing COVID-19 in a severe form is significantly increased. Thus, patients with IgG of low avidity (AI ≤ 40%) had an 89 ± 20.5% chance of a severe course of recurrent COVID-19, whereas the detection of high-avidity antibodies (AI ≥ 50%) gave a probability of 94 ± 7.9% for a mild course of recurrent disease (p < 0.05).

Cytomegalovirus DNA detection in pregnant women with a high IgG avidity index: a valuable tool for diagnosing non-primary infections?

Background/Aim Congenital human cytomegalovirus infection (cCMV) is the commonest congenital infection, and it can result in hearing loss and neurodevelopmental delay. Even if primary infections are more frequent and cause more severe congenital cCMV manifestations compared to NPIs, and despite partial protection from maternal immunity, the highest birth prevalence of cCMV is observed in seropositive women with non-primary CMV infection (NPI). Given that NPI contribute significantly to the overall burden of cCMV, their accurate diagnosis of NPI remains clinically important. Considering that the serological testing for CMV infection is not always reliable, we sought to determine whether detection of CMV DNA in pregnant women with a high IgG avidity index (AI) can help diagnose NPI. Materials and methods Human CMV serology screening (IgG, IgM, and IgG AI) was performed for confirmation of CMV infection in serum samples from mainly pregnant women with indications of CMV infection due to IgG+ and IgM+-positive samples in other laboratories. Pregnant women (or those with termination of pregnancy during the last period) with adequate IgG levels to perform IgG AI were included. Demographic data and mean gestation week at the time of screening were recorded. Serological testing was performed using CE-IVD commercial kits. CMV DNAemia detection by real time PCR (RT-PCR) was applied to confirm suspected CMV infection. Results Nine-hundred and thirty-four pregnant women CMV IgG positive with adequate IgG titers for AI testing were included in the study. The percentage of women with a high AI was 71.8% (671/934); among them, nearly 2.4% (16/671) had presence of CMV DNA. Also, 12.4% of women (116/934) had intermediate IgG AI and 15.7% of women (147/934) had low IgG AI. The presence of CMV DNA was observed in 13.8% (16/116) and 39.5% (58/147) of the groups with intermediate and low IgG AI, respectively. A high CMV IgG AI was associated with a negative CMV PCR status (p-value <.00001). Conclusions CMV DNA was present in 2.4% of seropositive women with high IgG AI, indicating active NPI and thus, harboring the risk of cCMV sequelae to the fetus. Moreover, the incidence of NPI may have been underestimated due to single timepoint testing. In order to detect CMV NPI in a seropositive woman, regular and frequent serology testing as well as detection of CMV DNAemia are required which render the whole diagnostic process impractical and not cost-effective.

Свойства антител к RBD у переболевших COVID-19 и вакцинированных препаратом «Спутник V»

SARS-CoV-2 specific antibody response is a generally accepted measure of postinfection and vaccination-induced immunity assessment. The dynamics of avidity maturation and neutralizing activity of virus-specific immunoglobulins G during the SARS-CoV-2–associated coronavirus infection was studied in cohorts of vaccinated volunteers and COVID-19 patients. 4–6 months after vaccination, neutralization activity was low compared to hospitalized patients (medians 57.4% vs 86.4%). On the opposite, the avidity indices in vaccinated volunteers were significantly higher (median 76.7%) than among hospitalized patients (median 61.4%). During the acute phase of the disease (14–16 days PI), post-vaccination patients have also higher avidity indices than primary patients (medians 43.5% vs 20.4%). Our results suggest that in long-term perspective antibody affinity maturation rate is higher after vaccination than after a natural infection. We demonstrated that Sputnik V vaccination leads to formation of high-avidity IgG, which persists for at least 6 months of observation. These results also indicate the presence of protective efficacy markers for at least 4–6 months after the vaccination or a previous illness and gives grounds for the half-year time period chosen for booster immunization with Sputnik V in Russia.

Seronegative Infection with Toxoplasma gondii in Asymptomatic Human Immunodeficiency Virus Type 1 (HIV-1)-Infected Patients and in Blood Donors.

Background: Toxoplasmosis is a common opportunistic infection in AIDS patients. The routine diagnostics is based on serologic testing and IgG avidity index, but it may have limited utility in immunodeficient patients; thus, it is recommendable to detect T. gondii DNA in subjects with advanced HIV disease. The results of the studies published so far focused on patients with clinical symptoms of toxoplasmosis. Our study encompassed a group of HIV-infected subjects on cART therapy, without immunological disturbances and clinical symptoms of T. gondii infection. Methods: The study was retrospective, and samples were collected between 2013 and 2016. We evaluate the prevalence of serological (IgM, IgG, and avidity IgG) and molecular (DNA) T. gondii infection markers in asymptomatic HIV-infected patients and the control group using serologic (ELISA) and quantitative (real-time PCR) molecular testing. Results: Of 152 HIV-infected in routine follow-up tested for T. gondii IgM and IgG, 6 (3.9%) and 50 (32.9%) were positive, respectively. Of 168 serum samples from blood donors, 1 (0.6%) and 49 (29.2%) were IgM+ and IgG+ positive, respectively. IgM seroprevalence in HIV-infected patients was significantly higher than in blood donors. T. gondii DNA (genotype II) was identified in 47 (30.9%) HIV-infected patients, with 13 (8.6%) IgM−IgG− samples. In blood donors, T. gondii DNA was present in 15 (8.9%) IgM−IgG−. Conclusions: In both groups, T. gondii DNA was detectable in seronegative subjects, implying the need to supplement the routine serological testing via the molecular method. It can help the accurate monitoring of the reactivation of infection in asymptomatic HIV-infected persons, and the quick introduction of specific therapy, in blood donors, would be of high importance for safe blood donations.

Factors Influencing Pneumococcal Vaccination-Induced Total IgG, IgG2, and IgA Levels in Vaccinated Splenectomized Patients

Splenectomy is closely associated with a lifetime risk of pneumococcal and other encapsulated bacterial infections. In this study, it was aimed to investigate the change of antibody levels after vaccination against Streptococcus pneumoniae according to age, gender, years after splenectomy and the possible effect of splenectomy on IgG avidity. In addition the education and awareness levels of the participants about post-splenectomy vaccination and infectious diseases were also analyzed. In the first of the three phases of this study, 32 individuals with splenectomy were enrolled. The awareness of the patients about the possible risks after splenectomy was investigated with a simple questionnaire. Routine laboratory test results were obtained and clinical examinations were performed. In the second stage, total Ig values of 29 splenectomy patients were determined. In the third phase, 14 splenectomy and 5 healthy volunteers were vaccinated according to the Vaccination Practices Advisory Committee (ACIP) guidelines. Pneumococcal-specific antibody levels and IgG avidity were detected by enzyme linked immunosorbent assay (ELISA). It was determined that 68.8% of the splenectomized patients were unaware of their vaccination status and 78.2% of them were unaware of the increased risk of infectious diseases in asplenic conditions. . According to the hospital information management system, all 31 (96.87%) patients, except one, were vaccinated with PPV23. As expected, vaccinated patients exhibited high levels of vaccine-specific antibody production with IgG, IgG2, and IgA antibody concentrations of 321 ± 76.68 mg/l, 73.07 ± 8.273 mg/l, and 117.8 ± 14.94 mg/l, respectively, but unvaccinated patients had very low antibody (IgG, IgG2 and IgA antibody concentrations were 11.5 mg/l, 1.3 mg/l and 1.2 mg/l, respectively) levels. Although there was no correlation between antibody titers and gender, age groups or presence of fever history, the decrease in total IgG, IgG2 and IgA titers were strongly correlated with the time since splenectomy. Antibody titers were found to be significantly lower in splenectomized patients vaccinated more than 10 years ago. Routine laboratory results were at normal levels except for low platelet count. On the other hand, both splenectomized and healthy control subjects displayed similar IgG avidity index values (%61.8 ve %64.4% inhibition in control and splenectomized subjects, respectively) after the vaccination schedule. It was shown that post-splenectomy vaccination with PPV23 induced high levels of pneumococcus-specific antibody production that can last for more than five years. It was determined that more efforts should be made to increase the level of knowledge about pneumococcal and other overwhelming post-splenectomy infections (OPSI) as the awareness of the patients about the risks of infection after splenectomy was poor. In particular, patients with splenectomy operation more than 10 years ago should be very careful about being asplenic as they were determined to have significantly lower level of vaccine-specific antibody production. Our study was also the first to show that splenectomy does not alter IgG avidity induced by pneumococcal vaccination.

A Polylactide-Based Micellar Adjuvant Improves the Intensity and Quality of Immune Response.

Micelles from amphiphilic polylactide-block-poly(N-acryloxysuccinimide-co-N-vinylpyrrolidone) (PLA-b-P(NAS-co-NVP)) block copolymers of 105 nm in size were characterized and evaluated in a vaccine context. The micelles were non-toxic in vitro (both in dendritic cells and HeLa cells). In vitro fluorescence experiments combined with in vivo fluorescence tomography imaging, through micelle loading with the DiR near infrared probe, suggested an efficient uptake of the micelles by the immune cells. The antigenic protein p24 of the HIV-1 was successfully coupled on the micelles using the reactive N-succinimidyl ester groups on the micelle corona, as shown by SDS-PAGE analyses. The antigenicity of the coupled antigen was preserved and even improved, as assessed by the immuno-enzymatic (ELISA) test. Then, the performances of the micelles in immunization were investigated and compared to different p24-coated PLA nanoparticles, as well as Alum and MF59 gold standards, following a standardized HIV-1 immunization protocol in mice. The humoral response intensity (IgG titers) was substantially similar between the PLA micelles and all other adjuvants over an extended time range (one year). More interestingly, this immune response induced by PLA micelles was qualitatively higher than the gold standards and PLA nanoparticles analogs, expressed through an increasing avidity index over time (>60% at day 365). Taken together, these results demonstrate the potential of such small-sized micellar systems for vaccine delivery.