An Update on Protective Effectiveness of Immune Responses After Recovery From COVID-19

Immunomodulatory functions of algal bioactive compounds

Algae, a crucial constituent of marine systems, serve an indispensable function as primary producers, supporting the marine food web, contributing to carbon sequestration, and providing habitats that sustain biodiversity. This review focuses on the bioactive constituents of algae, including polysaccharides, polyphenols, polypeptides, and terpenoid compounds, and discusses their potential applications in treating immune-related diseases, as well as the mechanisms through which they modulate immune responses. The bioactive substances derived from algae, including polyphenols, bioactive peptides, terpenes, polysaccharides and other compounds, may play a preventive role by modulating allergic responses and reducing the incidence of inflammation and cancer.

Surface Plasmon Resonance Immunosensor for Direct Detection of Antibodies against SARS-CoV-2 Nucleocapsid Protein

The strong immunogenicity of the SARS-CoV-2 nucleocapsid protein is widely recognized, and the detection of specific antibodies is critical for COVID-19 diagnostics in patients. This research proposed direct, label-free, and sensitive detection of antibodies against the SARS-CoV-2 nucleocapsid protein (anti-SCoV2-rN). Recombinant SARS-CoV-2 nucleocapsid protein (SCoV2-rN) was immobilized by carbodiimide chemistry on an SPR sensor chip coated with a self-assembled monolayer of 11-mercaptoundecanoic acid. When immobilized under optimal conditions, a SCoV2-rN surface mass concentration of 3.61 ± 0.52 ng/mm2 was achieved, maximizing the effectiveness of the immunosensor for the anti-SCoV2-rN determination. The calculated KD value of 6.49 × 10-8 ± 5.3 × 10-9 M confirmed the good affinity of the used monoclonal anti-SCoV2-rN antibodies. The linear range of the developed immunosensor was from 0.5 to 50 nM of anti-SCoV2-rN, where the limit of detection and the limit of quantification values were 0.057 and 0.19 nM, respectively. The immunosensor exhibited good reproducibility and specificity. In addition, the developed immunosensor is suitable for multiple anti-SCoV2-rN antibody detections.

Association of Prior COVID-19 Infection with Risk of Breakthrough Infection Following Vaccination: A Cohort Study in Isfahan, Iran

Background

Many people worldwide have developed a combination of natural and vaccine-induced immunity to COVID-19. This study investigated whether exposure to SARS-CoV-2 before full vaccination promotes protection against a breakthrough infection.

Methods

We studied a total of 2,902,545 people in the Isfahan COVID-19 Registry. All the participants had received two doses of either Sinopharm BIBP, ChAdOx1-nCoV-19, Gam-COVID-Vac, or BIV1-CovIran vaccines. A cohort study examined the association between prior COVID-19 infection and the risk of a breakthrough infection for each vaccine. Cohorts in each pair were matched by gender, age group, calendar week of the first dose, the interval between the first and second doses, and the proportion of healthcare workers. The probable virus variant for the previous infections was also considered. Each individual's follow-up started 14 days after their second vaccine dose until either the end of the study censoring date, occurrence of a COVID-19 infection, or death. The breakthrough infection risk was compared between each cohort pair by using the hazard ratio (HR) and incidence rate ratio (IRR).

Results

Total breakthrough HRs (95% confidence interval) (previously infected over infection-naïve matched cohort) were 0.36 (0.23-0.55), 0.35 (0.32-0.40), 0.37 (0.30-0.46), and 0.43 (0.32-0.56) for the BIV1-CovIran, Sinopharm BIBP, Gam-COVID-Vac, and ChAdOx1-nCoV-19 vaccine groups, respectively. The breakthrough infection IRRs were approximately similar to the total HRs mentioned above.

Conclusion

Prior SARS-CoV-2 infection conferred additive immunity against breakthrough after vaccination, no matter which vaccine brand was injected. Such a result could guide health authorities to codify low-cost high-benefit vaccination protocols and protect the community's well-being.

Protective effectiveness of previous infection against subsequent SARS-Cov-2 infection: systematic review and meta-analysis

Background

The protective effectiveness provided by naturally acquired immunity against SARS-CoV-2 reinfection remain controversial.

Objective

To systematically evaluate the protective effect of natural immunity against subsequent SARS-CoV-2 infection with different variants.

Methods

We searched for related studies published in seven databases before March 5, 2023. Eligible studies included in the analysis reported the risk of subsequent infection for groups with or without a prior SARS-CoV-2 infection. The primary outcome was the overall pooled incidence rate ratio (IRR) of SARS-CoV-2 reinfection/infection between the two groups. We also focused on the protective effectiveness of natural immunity against reinfection/infection with different SARS-CoV-2 variants. We used a random-effects model to pool the data, and obtained the bias-adjusted results using the trim-and-fill method. Meta-regression and subgroup analyses were conducted to explore the sources of heterogeneity. Sensitivity analysis was performed by excluding included studies one by one to evaluate the stability of the results.

Results

We identified 40 eligible articles including more than 20 million individuals without the history of SARS-CoV-2 vaccination. The bias-adjusted efficacy of naturally acquired antibodies against reinfection was estimated at 65% (pooled IRR = 0.35, 95% CI = 0.26-0.47), with higher efficacy against symptomatic COVID-19 cases (pooled IRR = 0.15, 95% CI = 0.08-0.26) than asymptomatic infection (pooled IRR = 0.40, 95% CI = 0.29-0.54). Meta-regression revealed that SARS-CoV-2 variant was a statistically significant effect modifier, which explaining 46.40% of the variation in IRRs. For different SARS-CoV-2 variant, the pooled IRRs for the Alpha (pooled IRR = 0.11, 95% CI = 0.06-0.19), Delta (pooled IRR = 0.19, 95% CI = 0.15-0.24) and Omicron (pooled IRR = 0.61, 95% CI = 0.42-0.87) variant were higher and higher. In other subgroup analyses, the pooled IRRs of SARS-CoV-2 infection were statistically various in different countries, publication year and the inclusion end time of population, with a significant difference (p = 0.02, p < 0.010 and p < 0.010), respectively. The risk of subsequent infection in the seropositive population appeared to increase slowly over time. Despite the heterogeneity in included studies, sensitivity analyses showed stable results.

Conclusion

Previous SARS-CoV-2 infection provides protection against pre-omicron reinfection, but less against omicron. Ongoing viral mutation requires attention and prevention strategies, such as vaccine catch-up, in conjunction with multiple factors.

Specific immune responses after BNT162b2 mRNA vaccination and COVID-19 infection

Although vaccines against COVID-19 are effective tools in preventing severe disease, recent studies have shown enhanced protection after vaccine boosters. The aim of our study was to examine the dynamics and duration of both humoral and cellular immune responses following a three-dose regimen of the BNT162b2 mRNA vaccine. In a longitudinal prospective study we enrolled 86 adults who received the BNT162b2 vaccine, 35 unvaccinated individuals with a history of mild COVID-19 and a control group of 30 healthy SARS-CoV-2 seronegative persons. We assessed the SARS-CoV-2-specific T cell responses and IgG production up to 12 months post the third BNT162b2 dose in 24 subjects. The vaccinated group had significantly higher IgG antibody levels after two doses compared to the convalescent group (p<0.001). After the third dose, IgG levels surged beyond those detected after the second dose (p<0.001). Notably, these elevated IgG levels were maintained 12 months post the third dose. After two doses, specific T cell responses were detected in 87.5% of the vaccinated group. Additionally, there was a significant decrease before the third dose. However, post the third dose, specific T cell responses surged and remained stable up to the 12-month period. Our findings indicate that the BNT162b2 vaccine induces potent and enduring humoral and cellular responses, which are notably enhanced by the third dose and remain persistant without a significant decline a year after the booster. Further research is essential to understand the potential need for subsequent boosters.

Following Natural Autoantibodies: Further Immunoserological Evidence Regarding Their Silent Plasticity and Engagement in Immune Activation

Contradictory reports are available on vaccine-associated hyperstimulation of the immune system, provoking the formation of pathological autoantibodies. Despite being interconnected within the same network, the role of the quieter, yet important non-pathological and natural autoantibodies (nAAbs) is less defined. We hypothesize that upon a prompt immunological trigger, physiological nAAbs also exhibit a moderate plasticity. We investigated their inducibility through aged and recent antigenic triggers. Anti-viral antibodies (anti-MMR n = 1739 and anti-SARS-CoV-2 IgG n = 330) and nAAbs (anti-citrate synthase IgG, IgM n = 1739) were measured by in-house and commercial ELISAs using Croatian (Osijek) anonymous samples with documented vaccination backgrounds. The results were subsequently compared for statistical evaluation. Interestingly, the IgM isotype nAAb showed a statistically significant connection with anti-MMR IgG seropositivity (p < 0.001 in all cases), while IgG isotype nAAb levels were elevated in association with anti-SARS CoV-2 specific seropositivity (p = 0.019) and in heterogeneous vaccine regimen recipients (unvaccinated controls vector/mRNA vaccines p = 0.002). Increasing evidence supports the interplay between immune activation and the dynamic expansion of nAAbs. Consequently, further questions may emerge regarding the ability of nAAbs silently shaping the effectiveness of immunization. We suggest re-evaluating the impact of nAAbs on the complex functioning of the immunological network.

COVID-19 recurrence is related to disease-early profile T cells while detection of anti-S1 IgG is related to multifunctional T cells

COVID-19 is caused by SARS-CoV-2 infection and leads from asymptomatic to severe outcomes. The recurrence of the COVID-19 has been described, however, mechanisms involved remains unclear. Thus, the work aimed to investigate the role of multifunctional T cells in patients with recurrent COVID-19. We evaluated clinical characteristics, presence of anti-S1 and anti-Nucleocapsid IgG in patients' sera, and multifunctional T cells (for IFN-γ, IL-2, and TNF-α) in patients with multiple episodes of COVID-19 and controls. Data demonstrate that patients with recurrent COVID-19 have a T cell pattern predominantly related to IFN-γ production. Also, patients with COVID-19 history and absence of anti-S1 IgG had lower levels of CD4+ IFN + IL-2 + TNF + T cells independently of number of disease episodes. Complementary, vaccination changed the patterns of T cells phenotypes and induced IgG seroconversion, despite not induce higher levels of multifunctional T cells in all patients. In conclusion, the data suggest that recurrent disease is related to early-disease T cell profile and absence of anti-S1 IgG is related to lower multifunctional CD4 T cell response, what suggests possibility of new episodes of COVID-19 in these patients.

Acute and long-term immune responses to SARS-CoV-2 infection in unvaccinated children and young adults with inborn errors of immunity

Purpose

To describe SARS-CoV-2 infection outcome in unvaccinated children and young adults with inborn errors of immunity (IEI) and to compare their specific acute and long-term immune responses with a sex-, age-, and severity-matched healthy population (HC).

Methods

Unvaccinated IEI patients up to 22 years old infected with SARS-CoV-2 were recruited along with a cohort of HC. SARS-CoV-2 serology and ELISpot were performed in the acute phase of infection (up to 6 weeks) and at 3, 6, 9, and 12 months.

Results

Twenty-five IEI patients (median age 14.3 years, min.-max. range 4.5-22.8; 15/25 males; syndromic combined immunodeficiencies: 48.0%, antibody deficiencies: 16.0%) and 17 HC (median age 15.3 years, min.-max. range 5.4-20.0; 6/17 males, 35.3%) were included. Pneumonia occurred in 4/25 IEI patients. In the acute phase SARS-CoV-2 specific immunoglobulins were positive in all HC but in only half of IEI in whom it could be measured (n=17/25): IgG+ 58.8% (10/17) (p=0.009); IgM+ 41.2% (7/17)(p<0.001); IgA+ 52.9% (9/17)(p=0.003). Quantitative response (index) was also lower compared with HC: IgG IEI (3.1 ± 4.4) vs. HC (3.5 ± 1.5)(p=0.06); IgM IEI (1.9 ± 2.4) vs. HC (3.9 ± 2.4)(p=0.007); IgA IEI (3.3 ± 4.7) vs. HC (4.6 ± 2.5)(p=0.04). ELISpots positivity was qualitatively lower in IEI vs. HC (S-ELISpot IEI: 3/11, 27.3% vs. HC: 10/11, 90.9%; p=0.008; N-ELISpot IEI: 3/9, 33.3% vs. HC: 11/11, 100%; p=0.002) and also quantitatively lower (S-ELISpot IEI: mean index 3.2 ± 5.0 vs. HC 21.2 ± 17.0; p=0.001; N-ELISpot IEI: mean index 9.3 ± 16.6 vs. HC: 39.1 ± 23.7; p=0.004). As for long term response, SARS-CoV-2-IgM+ at 6 months was qualitatively lower in IEI(3/8, 37.5% vs. 9/10 HC: 90.0%; p=0.043), and quantitatively lower in all serologies IgG, M, and A (IEI n=9, 1.1 ± 0.9 vs. HC n=10, 2.1 ± 0.9, p=0.03; IEI n=9, 1.3 ± 1.5 vs. HC n=10, 2.9 ± 2.8, p=0.02; and IEI n=9, 0.6 ± 0.5 vs. HC n=10, 1.7 ± 0.8, p=0.002 -respectively) but there were no differences at remaining time points.

Conclusions

Our IEI pediatric cohort had a higher COVID-19 pneumonia rate than the general age-range population, with lower humoral and cellular responses in the acute phase (even lower compared to the reported IEI serological response after SARS-CoV-2 vaccination), and weaker humoral responses at 6 months after infection compared with HC.

Herd Immunity to Fight Against COVID-19: A Narrative Review

The advent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its consequent illness, coronavirus disease 2019 (COVID-19), has revealed the severe impact of new, contagious pathogens on the population throughout the globe. Here, we describe the fundamental notions of herd immunity and discuss their consequences from the perspective of COVID-19, along with the obstacles to acquiring herd immunity. SARS-CoV-2 causes COVID-19, a contagious respiratory infection. It is a major global health issue, with more than 179 million positive cases and 3.8 million deaths globally. It has impacted more than 159 countries; hence, the World Health Organization designated it a pandemic. Different vaccines have been developed against coronavirus to slow the spread of this deadly virus. Immunizing people against coronavirus is the key to getting through this infectious virus. The central concept of this review article is the effect of vaccinating a large population to achieve herd immunity and the reasons for the delay in developing herd immunity. Herd immunity can prove highly beneficial for dealing with reinfection. Moreover, it can reduce the severity of the reinfection in many people who are twice infected with COVID-19. Herd immunity can prevent people in the high-risk group such as immunocompromised individuals; those on immunosuppressants; organ transplant recipients; particular age groups such as neonates, infants, toddlers, and elderly; those with impaired immunity; those with anaphylaxis reactions; and people with chronic diseases. However, due to repeated mutations of the virus, it is evolving into new strains with more severity. Its consequences on the immune system and response to a vaccine are still a big challenge to overcome. How new variants of COVID-19 impacted herd immunity needs to be investigated. The duration required for the development of herd immunity and how long it would last is still under research, along with the number of doses needed, booster doses, and the proportion of the population to be vaccinated.

SARS-CoV-2 Monitoring in Wastewater Reveals Novel Variants and Biomarkers of Infection

Wastewater-based epidemiology (WBE) is a popular tool for the early indication of community spread of infectious diseases. WBE emerged as an effective tool during the COVID-19 pandemic and has provided meaningful information to minimize the spread of infection. Here, we present a combination of analyses using the correlation of viral gene copies with clinical cases, sequencing of wastewater-derived RNA for the viral mutants, and correlative analyses of the viral gene copies with the bacterial biomarkers. Our study provides a unique platform for potentially using the WBE-derived results to predict the spread of COVID-19 and the emergence of new variants of concern. Further, we observed a strong correlation between the presence of SARS-CoV-2 and changes in the microbial community of wastewater, particularly the significant changes in bacterial genera belonging to the families of Lachnospiraceae and Actinomycetaceae. Our study shows that microbial biomarkers could be utilized as prediction tools for future infectious disease surveillance and outbreak responses. Overall, our comprehensive analyses of viral spread, variants, and novel bacterial biomarkers will add significantly to the growing body of literature on WBE and COVID-19.

Infection with SARS-CoV-2 Omicron Variant 24 Days after Non-Omicron Infection, Pennsylvania, USA

A 42-year-old man, with up-to-date COVID-19 vaccination, experienced symptomatic SARS-CoV-2 infection in December 2021. Mutation tests suggested a non-Omicron variant. After his recovery, and 24 days after the first positive SARS-CoV-2 test, he had onset of symptomatic infection with the BA.1.1 (Omicron) variant, which was confirmed by whole-genome sequencing.