SEROLOGICAL STUDY OF BOVINE LEUKOSIS IN IRAQ LOCAL BREED AND IMPORTED COW

Two hundreds and sixteen blood samples from Iraqi local breed cows in Baghdad, Basrah, Diala provinces and 144 blood samples from imported cows in three large cows stations were collected. All samples were tested by ELISA for the detection of specific antibody to bovine leucosis. Results revealed the presence of antibodies of 8.4 % in imported cows only. Whereas the blood samples from the local animals included in this study were negative.

Impaired neutralisation of SARS-CoV-2 delta variant in vaccinated patients with B cell chronic lymphocytic leukaemia

Background Immune suppression is a clinical feature of chronic lymphocytic leukaemia (CLL), and patients show increased vulnerability to SARS-CoV-2 infection and suboptimal antibody responses. Method We studied antibody responses in 500 patients following dual COVID-19 vaccination to assess the magnitude, correlates of response, stability and functional activity of the spike-specific antibody response with two different vaccine platforms. Results Spike-specific seroconversion post-vaccine was seen in 67% of patients compared to 100% of age-matched controls. Amongst responders, titres were 3.7 times lower than the control group. Antibody responses showed a 33% fall over the next 4 months. The use of an mRNA (n = 204) or adenovirus-based (n = 296) vaccine platform did not impact on antibody response. Male gender, BTKi therapy, prophylactic antibiotics use and low serum IgA/IgM were predictive of failure to respond. Antibody responses after CD20-targeted immunotherapy recovered 12 months post treatment. Post-vaccine sera from CLL patients with Spike-specific antibody response showed markedly reduced neutralisation of the SARS-CoV-2 delta variant compared to healthy controls. Patients with previous natural SARS-CoV-2 infection showed equivalent antibody levels and function as healthy donors after vaccination. Conclusions These findings demonstrate impaired antibody responses following dual COVID-19 vaccination in patients with CLL and further define patient risk groups. Furthermore, humoural protection against the globally dominant delta variant is markedly impaired in CLL patients and indicates the need for further optimisation of immune protection in this patient cohort.

One year landscape of the inactivated virus vaccine triggered RBD-specific IgG, IgM and IgA responses against the Omicron variant

We reported the first map of vaccine stimulated RBD-specific antibody responses (IgG, IgM and IgA) against the Omicron variant. We generated the map using a protein microarray, by analyzing longitudinal sera collected spanning one year from individuals immunized with 3 doses of an inactivated virus vaccine. The IgG response to RBD-Omicron is: 1/3-1/5 that of RBD-wild type; ~6x higher for the booster dose vs. the 2nd dose; and reaches the plateau in about two weeks after the booster dose, then drops ~5x in another two weeks. Similar results were also obtained for IgM and IgA. Because of the high correlation between RBD-specific antibody response and the neutralization activity to authentic virus, we at least indirectly revealed the landscape of antibody protection against the Omicron variant throughout the vaccination stages. Our results strongly support the necessity of booster vaccination. However, post-booster vaccination may need to be considered.

Comparison of IgA, IgG and neutralizing antibody responses following immunization with Moderna, BioNTech, AstraZeneca, Sputnik-V, Johnson and Johnson, and Sinopharm’s COVID-19 vaccines.

BACKGROUNDSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the resulting coronavirus disease 2019 (COVID-19) have afflicted millions of people in a worldwide pandemic. Several vaccines have been developed to prevent infection and illness. However, the safety and efficacy of most of the vaccines currently available are still being questioned by part of the public opinion. Even if vaccine-resistant individuals represent a minority in most countries, their hesitancy is sufficient to delay the highly desired ‘herd-immunity threshold.’ METHODSIn an ongoing multinational trial, we collected blood samples from 365 adults, 18 years of age or older, vaccinated with mRNA vaccines (Moderna, BioNTech), viral DNA-vectored vaccines (AstraZeneca, Sputnik-V, and Johnson and Johnson), or the attenuated virus vaccine from Sinopharm. Out of the 365 vaccinated individuals included in the study, 41 received two doses of Moderna Biotech's Spikevax, 92 received two doses of BioNTech’s Comirnaty, 52 were vaccinated with two doses of Oxford-AstraZeneca’s Vaxzevria, 34 received one dose of Johnson and Johnson’s Jansen, 35 two doses of Gamaleja’s Sputnik-V and 28 two doses of Sinopharm’s BBIBP-CorV. In addition, 40 received a prime dose of AstraZeneca followed by BioNTech as a booster, whereas 43 received Moderna’s vaccine as a booster after a prime dose of AstraZeneca. After collecting reactogenicity data, the expression of S-Protein binding IgG and IgA were analyzed before and after full vaccination in each group using an automated sandwich ELISA system. In addition, the neutralizing capacity of sera from individuals from all groups was investigated using an ACE-2-RBD neutralizing assay. RESULTSThe main side effects reported included short-term mild-to-moderate pain at the injection site, fatigue, and headache. More severe side effects were reported by vaccinees in the Moderna (10%), AstraZeneca (11%), Johnson and Johnson (5.9%), and Sputnik-V (7.2%) groups. No severe adverse reaction was reported in the BioNTech group, and the Sinopharm vaccinees presented the mildest reactogenicity profile, with 93.8% of the vaccinees declaring no adverse reactions. Moderna’s vaccine induced the highest amounts of SARS-CoV-2 specific IgG, IgA, and serum neutralization activity compared to the other groups. In contrast, people vaccinated with Sinopharm and Johnson and Johnson’s vaccines have the lowest SARS-CoV-2-specific antibody titers. Vaccinees from the Johnson and Johnson group presented significant levels of SARS-CoV-2 specific IgA but not IgG compared to the controls before vaccination. In the Sinopharm group, neither IgG nor IgA expression was significant. In addition, sera from vaccinees of these two groups presented no significant neutralization potential compared to the unvaccinated controls. Significant negative correlations between age and SARS-CoV-2- specific IgG expression were observed in the Johnson and Johnson (r=-0.4414, p=0.009) and Sinopharm (r=-0.6108, p=0.0006) groups. Remarkably, younger vaccinees (18-60 years old) in both Sinopharm and Johnson and Johnson groups produced substantial SARS-CoV-2 specific antibody expression and exhibited significant neutralization potential. While the AstraZeneca vaccine alone induced moderate IgG and IgA expression, the combination with Moderna or BioNTech mRNA vaccines induced higher antibody levels than a double dose of AstraZeneca and similar IgG expression and neutralization potential compared to Moderna, or BioNTech used alone. CONCLUSIONThe results suggest that the Moderna vaccine is the most immunogenic after two doses. AstraZeneca and Sputnik-V presented moderate but significant antibody expression and virus neutralizing properties. Low antibody and neutralization potential was observed in the elderly vaccinated with Sinopharm or Johnson and Johnson vaccines. The data also suggest that heterologous vaccination strategies combining the AstraZeneca DNA vectored vaccines and mRNA vaccines Moderna or BioNTech booster induced more robust antibody and virus neutralization potential compared to their homologous counterparts.

Preserved Omicron Spike specific antibody binding and Fc-recognition across COVID-19 vaccine platforms

Despite the dramatic spread of Omicron globally, even among highly vaccinated populations, death rates have not increased concomitantly. These data argue that alternative immune mechanisms, beyond neutralization, may continue to confer protection against severe disease. Beyond their ability to bind and block infection, antibodies contribute to control and clearance of multiple infections via their ability to direct antiviral immunity via Fc-effector mechanisms. Thus, here we probed the ability of vaccine induced antibodies, across three COVID-19 vaccines, to drive Fc-effector activity against Omicron. Despite the significant loss of IgM, IgA and IgG binding to the Omicron Receptor Binding Domain (RBD) across BNT162b2, mRNA-1273, and CoronaVac vaccines, stable isotype binding was observed across all of these vaccines to the Omicron Spike. Compromised RBD binding IgG was accompanied by a significant loss of cross RBD-specific antibody Fcγ-receptor binding by the CoronaVac vaccine, but preservation of RBD-specific FcγR2a and Fcγ3a binding across the mRNA vaccines. Conversely, Spike-specific antibodies exhibited persistent binding to Fcγ-receptors, across all three vaccines, albeit higher binding was observed with the mRNA vaccines, marked by a selective preservation of FcγR2a and Fcγ3a binding antibodies. Thus, despite the significant to near complete loss of Omicron neutralization across several vaccine platforms against Omicron, vaccine induced Spike-specific antibodies continue to recognize the virus and recruit Fc-receptors pointing to a persistent capacity for extra-neutralizing antibodies to contribute Omicron disease attenuation.

Detection of Antibody Responses Against SARS-CoV-2 in Plasma and Saliva From Vaccinated and Infected Individuals

Antibodies (Abs) are essential for the host immune response against SARS-CoV-2, and all the vaccines developed so far have been designed to induce Abs targeting the SARS-CoV-2 spike. Many studies have examined Ab responses in the blood from vaccinated and infected individuals. However, since SARS-CoV-2 is a respiratory virus, it is also critical to understand the mucosal Ab responses at the sites of initial virus exposure. Here, we examined plasma versus saliva Ab responses in vaccinated and convalescent patients. Although saliva levels were significantly lower, a strong correlation was observed between plasma and saliva total Ig levels against all SARS-CoV-2 antigens tested. Virus-specific IgG1 responses predominated in both saliva and plasma, while a lower prevalence of IgM and IgA1 Abs was observed in saliva. Antiviral activities of plasma Abs were also studied. Neutralization titers against the initial WA1 (D614G), B.1.1.7 (alpha) and B.1.617.2 (delta) strains were similar but lower against the B.1.351 (beta) strain. Spike-specific antibody-dependent cellular phagocytosis (ADCP) activities were also detected and the levels correlated with spike-binding Ig titers. Interestingly, while neutralization and ADCP potencies of vaccinated and convalescent groups were comparable, enhanced complement deposition to spike-specific Abs was noted in vaccinated versus convalescent groups and corresponded with higher levels of IgG1 plus IgG3 among the vaccinated individuals. Altogether, this study demonstrates the detection of Ab responses after vaccination or infection in plasma and saliva that correlate significantly, although Ig isotypic differences were noted. The induced plasma Abs displayed Fab-mediated and Fc-dependent functions with comparable neutralization and ADCP potencies, but a greater capacity to activate complement was elicited upon vaccination.

Predictive Potential of Flow Cytometry Crossmatching in Deceased Donor Kidney Transplant Recipients Subjected to Peritransplant Desensitization

Recipient sensitization is a major risk factor of antibody-mediated rejection (ABMR) and inferior graft survival. The predictive effect of solid-phase human leukocyte antigen antibody testing and flow cytometry crossmatch (FCXM) in the era of peritransplant desensitization remains poorly understood. This observational retrospective single-center study with 108 donor-specific antibody (DSA)-positive deceased donor kidney allograft recipients who had undergone peritransplant desensitization aimed to analyze variables affecting graft outcome. ABMR rates were highest among patients with positive pretransplant FCXM vs. FCXM-negative (76 vs. 18.7%, p < 0.001) and with donor-specific antibody mean fluorescence intensity (DSA MFI) > 5,000 vs. <5,000 (54.5 vs. 28%, p = 0.01) despite desensitization. In univariable Cox regression, FCXM positivity, retransplantation, recipient gender, immunodominant DSA MFI, DSA number, and peak panel reactive antibodies were found to be associated with ABMR occurrence. In multivariable Cox regression adjusted for desensitization treatment (AUC = 0.810), only FCXM positivity (HR = 4.6, p = 0.001) and DSA number (HR = 1.47, p = 0.039) remained significant. In conclusion, our data suggest that pretransplant FCXM and DSA number, but not DSA MFI, are independent predictors of ABMR in patients who received peritransplant desensitization.

Epitope profiling using computational structural modelling demonstrated on coronavirus-binding antibodies

Identifying the epitope of an antibody is a key step in understanding its function and its potential as a therapeutic. Sequence-based clonal clustering can identify antibodies with similar epitope complementarity, however, antibodies from markedly different lineages but with similar structures can engage the same epitope. We describe a novel computational method for epitope profiling based on structural modelling and clustering. Using the method, we demonstrate that sequence dissimilar but functionally similar antibodies can be found across the Coronavirus Antibody Database, with high accuracy (92% of antibodies in multiple-occupancy structural clusters bind to consistent domains). Our approach functionally links antibodies with distinct genetic lineages, species origins, and coronavirus specificities. This indicates greater convergence exists in the immune responses to coronaviruses than is suggested by sequence-based approaches. Our results show that applying structural analytics to large class-specific antibody databases will enable high confidence structure-function relationships to be drawn, yielding new opportunities to identify functional convergence hitherto missed by sequence-only analysis.

SARS-CoV-2 Antibodies Are Persisting in Saliva for More Than 15 Months After Infection and Become Strongly Boosted After Vaccination

SARS-CoV-2 antibodies in saliva serve as first line of defense against the virus. They are present in the mucosa, more precisely in saliva, after a recovered infection and also following vaccination. We report here the antibody persistence in plasma and in saliva up to 15 months after mild COVID-19. The IgG antibody response was measured every two months in 72 participants using an established and validated in-house ELISA assay. In addition, the virus inhibitory activity of plasma antibodies was assessed in a surrogate virus neutralization test before and after vaccination. SARS-CoV-2-specific antibody concentrations remained stable in plasma and saliva and the response was strongly boosted after one dose COVID-19 vaccination.