B-Cell Memory Responses to Variant Viral Antigens

The NFκB signaling system in the generation of B-cell subsets: from germinal center B cells to memory B cells and plasma cells

Memory B cells and antibody-secreting cells are the two prime effector B cell populations that drive infection- and vaccine-induced long-term antibody-mediated immunity. The antibody-mediated immunity mostly relies on the formation of specialized structures within secondary lymphoid organs, called germinal centers (GCs), that facilitate the interactions between B cells, T cells, and antigen-presenting cells. Antigen-activated B cells may proliferate and differentiate into GC-independent plasmablasts and memory B cells or differentiate into GC B cells. The GC B cells undergo proliferation coupled to somatic hypermutation of their immunoglobulin genes for antibody affinity maturation. Subsequently, affinity mature GC B cells differentiate into GC-dependent plasma cells and memory B cells. Here, we review how the NFκB signaling system controls B cell proliferation and the generation of GC B cells, plasmablasts/plasma cells, and memory B cells. We also identify and discuss some important unanswered questions in this connection.

Assessment of the formation and intensity of adaptive immunity in patients with COVID-19

The study of adaptive immunity in survivors of a new coronavirus infection is an important task, since there is no consensus on whether the severity of the disease affects the formation and intensity of the immune response to COVID-19. In this regard, a comparative assessment of the presence and duration of preservation of cellular and humoral immunity in patients with COVID-19 of varying severity was carried out. The study involved volunteers who had been ill with a new coronavirus infection asymptomatically (n=30), in moderate severity (n=21) and in severe form (n=12). The average age of the subjects was 47.312.5 years. The formation of cellular immunity was judged by an increase in the synthesis of IFN- in response to stimulation of lymphocytes for 16-20 hours by glycoprotein S(RBD) of the causative agent COVID-19. To determine IFN- products, the gamma InterferonIFA-BEST test system, manufactured by Vector-Best JSC, Russia, was used. The humoral immune response was recorded by detecting class G antibodies using the "SARS-CoV-2RBD-ELISA-Gamalei" test system (FSBI "N.F. Gamalei NITSEM" of the Ministry of Health of the Russian Federation). The results obtained indicate that patients from all groups have both humoral and cellular immunity to the causative agent of a new coronavirus infection. However, the number of people with adaptive immunity to COVID-19 and the duration of its preservation depends on the severity of the infection. A significant decrease in the number of people with cellular immunity was revealed in the group of seriously ill. At the same time, the majority of volunteers in this group registered the presence of class G immunoglobulins before the end of observation. In this group, unlike the other two, no patients were identified in whom only the cellular link of the immune response was activated. Volunteers who did not retain adaptive immunity to the causative agent of a new coronavirus infection appeared only by the end of the observation period. Among those who had the disease in an average form 7-8 months after recovery, there was a decrease in the number of people with cellular and humoral immunity. This process started earlier than in the group of patients who were asymptomatic and continued until the end of the study. The proportion of individuals with cellular immunity increased, and at a later date with a humoral immune response. By the end of the study, a high percentage of volunteers remained asymptomatically infected, having cellular and humoral immunity to SARS-CoV-2. Their number remained statistically higher than in the group of those who had a new coronavirus infection of moderate severity, but lower than in the group of those who were seriously ill. Also in this group, by the end of the experiment, an increase in the number of volunteers with only a cellular immune response was recorded. According to the data obtained, at the end of the observation period, the number of volunteers with humoral immunity to the causative agent of a new coronavirus infection is higher compared to those with a cellular immune response

The neutrophil-to-lymphocyte and monocyte-to-lymphocyte ratios are independently associated with clinical outcomes of viral encephalitis

Background

The neutrophil-to-lymphocyte ratio (NLR) and monocyte-to-lymphocyte ratio (MLR) are used as prognostic biomarkers for many diseases. In this study, we aimed to explore the possibility of using ratios of NLR and MLR to predict the prognosis of viral encephalitis (VE).

Methods

A total of 81 patients with an initial diagnosis of VE who were admitted to our hospital from January 2018 to January 2021 were retrospectively analyzed. A routine blood test within 24 h of admission was utilized to determine the ratios of NLR and MLR for each patient. The modified Rankin Scale (mRS) at 12 months after discharge was used to evaluate patients' clinical prognosis and the patients were divided into the group of good prognosis (mRS ≤ 1) and the group of poor prognosis (mRS ≥ 2) according to the mRS scores. Univariate and multivariable regression analyses were used to differentiate and assess independent prognostic factors for the prognosis of VE.

Results

Neutrophil-to-lymphocyte ratio and MLR of the poor prognosis group were significantly higher than that of the good prognosis group. Multivariate logistic regression analysis results showed that NLR [odds ratio (OR): 1.421, 95% confidence interval (CI): 1.105-1.827; P < 0.05] and MLR (OR: 50.423, 95% CI: 2.708-939.001; P < 0.05) were independent risk factors for the poor prognosis of VE. NLR > 4.32 and MLR > 0.44 were suggested as the cutoff threshold for the prediction of the poor prognosis of VE.

Conclusion

Neutrophil-to-lymphocyte ratio and MLR obtained from blood tests done at hospital admission have the potential to predict poor prognosis in patients with VE.

Adaptive Immunity to Viruses: What Did We Learn from SARS-CoV-2 Infection?

The SARS-CoV-2 virus causes various conditions, from asymptomatic infection to the fatal coronavirus disease 2019 (COVID-19). An intact immune system can overcome SARS-CoV-2 and other viral infections. Defective natural, mainly interferon I- and III-dependent, responses may lead to the spread of the virus to multiple organs. Adaptive B- and T-cell responses, including memory, highly influence the severity and outcome of COVID-19. With respect to B-cell immunity, germinal centre formation is delayed or even absent in the most severe cases. Extrafollicular low-affinity anti-SARS-CoV-2 antibody production will occur instead of specific, high-affinity antibodies. Helper and CD8+ cytotoxic T-cells become hyperactivated and then exhausted, leading to ineffective viral clearance from the body. The dysregulation of neutrophils and monocytes/macrophages, as well as lymphocyte hyperreactivity, might lead to the robust production of inflammatory mediators, also known as cytokine storm. Eventually, the disruption of this complex network of immune cells and mediators leads to severe, sometimes fatal COVID-19 or another viral disease.

COVID-19 vaccination elicits an evolving, cross-reactive antibody response to epitopes conserved with endemic coronavirus spike proteins

The COVID-19 pandemic has triggered the first widespread vaccination campaign against a coronavirus. Many vaccinated subjects are previously naive to SARS-CoV-2; however, almost all have previously encountered other coronaviruses (CoVs), and the role of this immunity in shaping the vaccine response remains uncharacterized. Here, we use longitudinal samples and highly multiplexed serology to identify mRNA-1273 vaccine-induced antibody responses against a range of CoV Spike epitopes, in both phylogenetically conserved and non-conserved regions. Whereas reactivity to SARS-CoV-2 epitopes shows a delayed but progressive increase following vaccination, we observe distinct kinetics for the endemic CoV homologs at conserved sites in Spike S2: these become detectable sooner and decay at later time points. Using homolog-specific antibody depletion and alanine-substitution experiments, we show that these distinct trajectories reflect an evolving cross-reactive response that can distinguish rare, polymorphic residues within these epitopes. Our results reveal mechanisms for the formation of antibodies with broad reactivity against CoVs.

COVID-19 vaccination recruits and matures cross-reactive antibodies to conserved epitopes in endemic coronavirus Spike proteins.. [PMID: 35118479 PMCID: PMC8811912 DOI: 10.1101/2022.01.24.22269542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The COVID-19 pandemic has triggered the first widespread vaccination campaign against a coronavirus. Most vaccinated subjects are naïve to SARS-CoV-2, however almost all have previously encountered other coronaviruses (CoVs) and the role of this immunity in shaping the vaccine response remains uncharacterized. Here we use longitudinal samples and highly-multiplexed serology to identify mRNA-1273 vaccine-induced antibody responses against a range of CoV Spike epitopes and in both phylogenetically conserved and non-conserved regions. Whereas reactivity to SARS-CoV-2 epitopes showed a delayed but progressive increase following vaccination, we observed distinct kinetics for the endemic CoV homologs at two conserved sites in Spike S2: these became detectable sooner, and decayed at later timepoints. Using homolog-specific depletion and alanine-substitution experiments, we show that these distinctly-evolving specificities result from cross-reactive antibodies as they mature against rare, polymorphic residues within these epitopes. Our results reveal mechanisms for the formation of antibodies with broad reactivity against CoVs.

A systematic review of Vaccine Breakthrough Infections by SARS-CoV-2 Delta Variant

Vaccines are proving to be highly effective in controlling hospitalization and deaths associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, as shown by clinical trials and real-world evidence. However, a deadly second wave of coronavirus disease 2019 (COVID-19), infected by SARS-CoV-2 variants, especially the Delta (B.1.617.2) variant, with an increased number of post-vaccination breakthrough infections were reported in the world recently. Actually, Delta variant not only resulted in a severe surge of vaccine breakthrough infections which was accompanied with high viral load and transmissibility, but also challenged the development of effective vaccines. Therefore, the biological characteristics and epidemiological profile of Delta variant, the current status of Delta variant vaccine breakthrough infections and the mechanism of vaccine breakthrough infections were discussed in this article. In addition, the significant role of the Delta variant spike (S) protein in the mechanism of immune escape of SARS-CoV-2 was highlighted in this article. In particular, we further discussed key points on the future SARS-CoV-2 vaccine research and development, hoping to make a contribution to the early, accurate and rapid control of the COVID-19 epidemic.

Identification and Characterization of Swine Influenza Virus H1N1 Variants Generated in Vaccinated and Nonvaccinated, Challenged Pigs

Influenza viruses represent a continuous threat to both animal and human health. The 2009 H1N1 A influenza pandemic highlighted the importance of a swine host in the adaptation of influenza viruses to humans. Nowadays, one of the most extended strategies used to control swine influenza viruses (SIVs) is the trivalent vaccine application, whose formulation contains the most frequently circulating SIV subtypes H1N1, H1N2, and H3N2. These vaccines do not provide full protection against the virus, allowing its replication, evolution, and adaptation. To better understand the main mechanisms that shape viral evolution, here, the SIV intra-host diversity was analyzed in samples collected from both vaccinated and nonvaccinated animals challenged with the H1N1 influenza A virus. Twenty-eight whole SIV genomes were obtained by next-generation sequencing, and differences in nucleotide variants between groups were established. Substitutions were allocated along all influenza genetic segments, while the most relevant nonsynonymous substitutions were allocated in the NS1 protein on samples collected from vaccinated animals, suggesting that SIV is continuously evolving despite vaccine application. Moreover, new viral variants were found in both vaccinated and nonvaccinated pigs, showing relevant substitutions in the HA, NA, and NP proteins, which may increase viral fitness under field conditions.

Advances in understanding the formation and fate of B-cell memory in response to immunization or infection

Immunological memory has the potential to provide lifelong protection against recurrent infections. As such, it has been crucial to the success of vaccines. Yet, the recent pandemic has illuminated key gaps in our knowledge related to the factors influencing effective memory formation and the inability to predict the longevity of immune protection. In recent decades, researchers have acquired a number of novel and powerful tools with which to study the factors underpinning humoral memory. These tools have been used to study the B-cell fate decisions that occur within the germinal centre (GC), a site where responding B cells undergo affinity maturation and are one of the major routes for memory B cell and high-affinity long-lived plasma cell formation. The advent of single-cell sequencing technology has provided an enhanced resolution for studying fate decisions within the GC and cutting-edge techniques have enabled researchers to model this reaction with more accuracy both in vitro and in silico. Moreover, modern approaches to studying memory B cells have allowed us to gain a better appreciation for the heterogeneity and adaptability of this vital class of B cells. Together, these studies have facilitated important breakthroughs in our understanding of how these systems operate to ensure a successful immune response. In this review, we describe recent advances in the field of GC and memory B-cell biology in order to provide insight into how humoral memory is formed, as well as the potential for generating lasting immunity to novel pathogens such as severe acute respiratory syndrome coronavirus 2.