SARS-CoV-2 reinfections: Overview of efficacy and duration of natural and hybrid immunity

Seroprevalence surveys suggest that more than a third and possibly more than half of the global population has been infected with SARS-CoV-2 by early 2022. As large numbers of people continue to be infected, the efficacy and duration of natural immunity in terms of protection against SARS-CoV-2 reinfections and severe disease is of crucial significance for the future. This narrative review provides an overview on epidemiological studies addressing this issue. National surveys covering 2020-2021 documented that a previous SARS-CoV-2 infection is associated with a significantly reduced risk of reinfections with efficacy lasting for at least one year and only relatively moderate waning immunity. Importantly, natural immunity showed roughly similar effect sizes regarding protection against reinfection across different SARS-CoV-2 variants, with the exception of the Omicron variant for which data are just emerging before final conclusions can be drawn. Risk of hospitalizations and deaths was also reduced in SARS-CoV-2 reinfections versus primary infections. Observational studies indicate that natural immunity may offer equal or greater protection against SARS-CoV-2 infections compared to individuals receiving two doses of an mRNA vaccine, but data are not fully consistent. The combination of a previous SARS-CoV-2 infection and a respective vaccination, termed hybrid immunity, seems to confer the greatest protection against SARS-CoV-2 infections, but several knowledge gaps remain regarding this issue. Natural immunity should be considered for public health policy regarding SARS-CoV-2.

COVID-19 optimal vaccination policies: A modeling study on efficacy, natural and vaccine-induced immunity responses

About a year into the pandemic, COVID-19 accumulates more than two million deaths worldwide. Despite non-pharmaceutical interventions such as social distance, mask-wearing, and restrictive lockdown, the daily confirmed cases remain growing. Vaccine developments from Pfizer, Moderna, and Gamaleya Institute reach more than 90% efficacy and sustain the vaccination campaigns in multiple countries. However, natural and vaccine-induced immunity responses remain poorly understood. There are great expectations, but the new SARS-CoV-2 variants demand to inquire if the vaccines will be highly protective or induce permanent immunity. Further, in the first quarter of 2021, vaccine supply is scarce. Consequently, some countries that are applying the Pfizer vaccine will delay its second required dose. Likewise, logistic supply, economic and political implications impose a set of grand challenges to develop vaccination policies. Therefore, health decision-makers require tools to evaluate hypothetical scenarios and evaluate admissible responses. Following some of the WHO-SAGE recommendations, we formulate an optimal control problem with mixed constraints to describe vaccination schedules. Our solution identifies vaccination policies that minimize the burden of COVID-19 quantified by the number of disability-adjusted years of life lost. These optimal policies ensure the vaccination coverage of a prescribed population fraction in a given time horizon and preserve hospitalization occupancy below a risk level. We explore "via simulation" plausible scenarios regarding efficacy, coverage, vaccine-induced, and natural immunity. Our simulations suggest that response regarding vaccine-induced immunity and reinfection periods would play a dominant role in mitigating COVID-19.

T Cells Primed by Live Mycobacteria Versus a Tuberculosis Subunit Vaccine Exhibit Distinct Functional Properties

Despite inducing strong T cell responses, Mycobacterium tuberculosis (Mtb) infection fails to elicit protective immune memory. As such latently infected or successfully treated Tuberculosis (TB) patients are not protected against recurrent disease. Here, using a mouse model of aerosol Mtb infection, we show that memory immunity to H56/CAF01 subunit vaccination conferred sustained protection in contrast to the transient natural immunity conferred by Mtb infection. Loss of protection to re-infection in natural Mtb memory was temporally linked to an accelerated differentiation of ESAT-6- and to a lesser extent, Ag85B-specific CD4 T cells in both the lung parenchyma and vasculature. This phenotype was characterized by high KLRG1 expression and low, dual production of IFN-γ and TNF. In contrast, H56/CAF01 vaccination elicited cells that expressed low levels of KLRG1 with copious expression of IL-2 and IL-17A. Co-adoptive transfer studies revealed that H56/CAF01 induced memory CD4 T cells efficiently homed into the lung parenchyma of mice chronically infected with Mtb. In comparison, natural Mtb infection- and BCG vaccine-induced memory CD4 T cells exhibited a poor ability to home into the lung parenchyma. These studies suggest that impaired lung migratory capacity is an inherent trait of the terminally differentiated memory responses primed by mycobacteria/mycobacterial vectors.

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Differentiation state of M. tuberculosis (Mtb)-specific CD4 memory T cells differ depending on their initial priming

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Live mycobacteria prime fully differentiated CD4 memory T cells with lower lung homing capacity than subunit vaccination

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Lung parenchymal Mtb memory CD4 T cells produce fewer & less cytokines, express more KLRG1 and cannot sustain protection

People latently infected with M. tuberculosis or successfully treated for Tuberculosis are not protected against recurrent disease, even in the presence of strong T cell responses. Here, using a well-established mouse model, we show that in contrast to subunit vaccination, live mycobacteria prime CD4 T cells that are highly differentiated, have an inferior lung homing capacity and show impaired function once in the parenchyma leading to lack of sustained protection against challenge. This indicates a central shortcoming of natural immunity that needs to be addressed in order to develop improved vaccines against TB.

The influence of age and genetics on natural resistance to experimentally induced feline infectious peritonitis

Naturally occurring feline infectious peritonitis (FIP) is usually fatal, giving the impression that immunity to the FIP virus (FIPV) is extremely poor. This impression may be incorrect, because not all cats experimentally exposed to FIPV develop FIP. There is also a belief that the incidence of FIP may be affected by a number of host, virus, and environmental cofactors. However, the contribution of these cofactors to immunity and disease incidence has not been determined. The present study followed 111 random-bred specific pathogen free (SPF) cats that were obtained from a single research breeding colony and experimentally infected with FIPV. The cats were from several studies conducted over the past 5 years, and as a result, some of them had prior exposure to feline enteric coronavirus (FECV) or avirulent FIPVs. The cats were housed under optimized conditions of nutrition, husbandry, and quarantine to eliminate most of the cofactors implicated in FIPV infection outcome and were uniformly challenge exposed to the same field strain of serotype 1 FIPV. Forty of the 111 (36%) cats survived their initial challenge exposure to a Type I cat-passaged field strains of FIPV. Six of these 40 survivors succumbed to FIP to a second or third challenge exposure, suggesting that immunity was not always sustained. Exposure to non-FIP-inducing feline coronaviruses prior to challenge with virulent FIPV did not significantly affect FIP incidence but did accelerate the disease course in some cats. There were no significant differences in FIP incidence between males and females, but resistance increased significantly between 6 months and 1 or more years of age. Genetic testing was done on 107 of the 111 infected cats. Multidimensional scaling (MDS) segregated the 107 cats into three distinct families based primarily on a common sire(s), and resistant and susceptible cats were equally distributed within each family. Genome-wide association studies (GWAS) on 73 cats that died of FIP after one or more exposures (cases) and 34 cats that survived (controls) demonstrated four significant associations after 100k permutations. When these same cats were analyzed using a sib-pair transmission test, three of the four associations were confirmed although not with genome-wide significance. GWAS was then done on three different age groups of cases to take into account age-related resistance, and different associations were observed. The only common and strong association identified between the various GWAS case configurations was for the 34.7-45.8Mb region of chromosome A3. No obvious candidate genes were present in this region.

Evaluation of immune response to single dose of quadrivalent HPV vaccine at 10-year post-vaccination

BACKGROUND

The recent World Health Organization recommendation supporting single-dose of HPV vaccine will significantly reduce programmatic cost, mitigate the supply shortage, and simplify logistics, thus allowing more low- and middle-income countries to introduce the vaccine. From a programmatic perspective the durability of protection offered by a single-dose will be a key consideration. The primary objectives of the present study were to determine whether recipients of a single-dose of quadrivalent HPV vaccine had sustained immune response against targeted HPV types (HPV 6,11,16,18) at 10 years post-vaccination and whether this response was superior to the natural antibody titres observed in unvaccinated women.

METHODS

Participants received at age 10-18 years either one, two or three doses of the quadrivalent HPV vaccine. Serology samples were obtained at different timepoints up to 10 years after vaccination from a convenience sample of vaccinated participants and from age-matched unvaccinated women at one timepoint. The evolution of the binding and neutralizing antibody response was presented by dose received. 10-year durability of immune responses induced by a single-dose was compared to that after three doses of the vaccine and in unvaccinated married women.

RESULTS

The dynamics of antibody response among the single-dose recipients observed over 120 months show stabilized levels 18 months after vaccination for all four HPV types. Although the HPV type-specific (binding or neutralizing) antibody titres after a single-dose were significantly inferior to those after three doses of the vaccine (lower bounds of GMT ratios < 0.5), they were all significantly higher than those observed in unvaccinated women following natural infections (GMT ratios: 2.05 to 4.04-fold higher). The results correlate well with the high vaccine efficacy of single-dose against persistent HPV 16/18 infections reported by us earlier at 10-years post-vaccination.

CONCLUSION

Our study demonstrates the high and durable immune response in single-dose recipients of HPV vaccine at 10-years post vaccination.

Imazapyr+imazapic herbicide determines acute toxicity in silver catfish Rhamdia quelen

Imazapyr (IMY) and imazapic (IMI) are imidazolinone herbicides which have been associated in a commercial formulation (Kifix(®)). To date, there are no studies on the toxicity of an IMY+IMI herbicide in fish. This work aimed to assess the acute toxicity (24 and 96 h) of IMY+IMI (0, 0.488 and 4.88 µg/L) towards Rhamdia quelen through hematological, biochemical, immunological, ionoregulatory and enzymatic indexes. Red blood cell count was lower at 4.88 than at 0.488 µg/L (24 and 96 h); mean corpuscular volume was lower than control at both concentrations (24 h) and at 0.488 µg/L (96 h); lymphocytes declined at 4.88 µg/L comparing to control (96 h); and monocytes increased at 4.88 µg/L (96 h) in comparison with the respective control and with 4.88 µg/L at 24h. Aspartate aminotransferase was higher at 0.488 µg/L (96 h) than the respective control and the respective concentration at 24 h; uric acid reduced at 4.88 µg/L comparing with 0.488 µg/L (96 h); and cortisol was lower at 4.88 µg/L compared to 0.488 µg/L and control (96 h). Herbicide exposure lowered plasma bactericidal activity at both concentrations (24 h) and at 0.488 µg/L (96 h); and plasma complement activity declined at 4.88 µg/L comparing with 0.488 µg/L and control (96 h), and was lower at all concentrations at 96 h than at 24 h. Plasma K(+) levels were higher at 4.88µg/L than in the remaining groups (24 and 96h); and Na(+) levels decreased at 4.88 µg/L compared to control (96 h). Na(+)/K(+)-ATPase and H(+)-ATPase activities in gills were lower at 4.88 µg/L comparing with control (24 h) and with the respective concentration at 96 h; and AChE activity in brain was higher at 0.488 and 4.88 µg/L than control (24 h) and the respective concentrations at 96 h, while in muscle it was higher at 0.488 and 4.88 µg/L than control (96 h) and the respective concentrations at 24 h. The present findings demonstrate that, despite IMY+IMI targets the animal-absent AHAS enzyme, such formulation displayed an acute toxic effect upon R. quelen homeostasis by impacting on vital functions such as immune defense, metabolism, ionoregulation and neurotransmission.

Significance of SARS-CoV-2 specific antibody testing during COVID-19 vaccine allocation

OBJECTIVE

To assess the value of using SARS-CoV-2 specific antibody testing to prioritize the vaccination of susceptible individuals as part of a COVID-19 vaccine distribution plan when vaccine supply is limited.

METHODS

An extended susceptible-infected-recovered (SIR) compartmental model was used to simulate COVID-19 spread when considering diagnosis, isolation, and vaccination of a cohort of 1 million individuals. The scenarios modeled represented 4 pandemic severity scenarios and various times when the vaccine becomes available during the pandemic. Eligible individuals have a probability p of receiving antibody testing prior to vaccination (p = 0, 0.25, 0.5, 0.75, and 1). The vaccine was modeled as a single dose vaccine with 90% and 70% efficacy. The value of serology testing was evaluated by comparing the infection attack rate, peak infections, peak day, and deaths.

RESULTS

The use of antibody testing to prioritize the allocation of limited vaccines reduces infection attack rates and deaths. The size of the reduction depends on when the vaccine becomes available relative to the infection peak day. The largest percentage reduction in cases and deaths occurs when the vaccine is deployed before and close to the infection peak day. The reduction in the number of cases and deaths diminishes as vaccine deployment is delayed.

CONCLUSIONS

Antibody testing as part of the vaccination plan is an effective method to maximize the benefit of a COVID-19 vaccine. Decision-makers need to consider relative timing between the infection peak day and when the vaccine becomes available.

A novel HIV vaccine targeting the protease cleavage sites

HIV preferentially infects activated CD4+ T cells and mutates rapidly. The classical vaccine approach aimed to generate broad immune responses to full HIV proteins largely failed to address the potential adverse impact of increased number of activated CD4+ T cells as viral targets. Learning from natural immunity observed in a group of HIV resistant Kenyan female sex workers, we are testing a novel vaccine approach. It focuses immune response to the highly conserved sequences surrounding the HIV protease cleavage sites (PCS) to disrupt viral maturation, while limiting excessive immune activation. Our pilot studies using nonhuman primate SIV infection models suggest that this approach is feasible and promising.

Antihypertensive therapy increases natural immunity response in hypertensive patients

AIMS

The aim of this work was to evaluate the effects of treatment of hypertension on the autoantibodies to apolipoprotein B-derived peptides (anti-ApoB-D peptide Abs) response, inflammation markers and vascular function.

MAIN METHODS

Eighty-eight patients with hypertension (stage 1 or 2) were recruited and advised to receive perindopril (4mg), hydrochlorothiazide (25mg), or indapamide (1.5mg) for 12weeks in a blinded fashion. Office and 24-h ambulatory blood pressure monitoring (24h ABPM), flow-mediated dilatation (FMD), nitrate-induced dilatation (NID), titers of IgG and IgM anti-ApoB-D peptide Abs, hsCRP, and interleukins (IL-8 and IL-10) were evaluated at baseline and 12weeks after therapies.

KEY FINDINGS

All treatments reduced office BP, and improved FMD (P<0.05 vs. baseline). The NID was improved only in the perindopril arm (P<0.05 vs. baseline). The 24h-ABPM was reduced with perindopril and hydrochlorothiazide therapies (P<0.05 vs. baseline), but not with indapamide, and this effect was followed by increase in titers of IgM Anti-ApoB-D peptide Abs (P<0.05 vs. baseline), without modifications in titers IgG Anti-ApoB-D peptide Abs and interleukins. Multivariable regression analysis has shown that change in the titers of IgM anti-ApoB-D peptide was associated with the changes in FMD (β -0.347; P<0.05).

SIGNIFICANCE

These findings shed light to a possible modulator effect of the antihypertensive therapy on the natural immunity responses and vascular function.

Infection resisters: targets of new research for uncovering natural protective immunity against Mycobacterium tuberculosis

“Infection resisters” are broadly defined as individuals who despite significant exposure to Mycobacterium tuberculosis remain persistently unreactive to conventional detection assays, suggesting that they remain uninfected or rapidly clear their infection early on following exposure. In this review, we highlight recent studies that point to underlying host immune mechanisms that could mediate this natural resistance. We also illustrate some additional avenues that are likely to be differently modulated in resisters and possess the potential to be targeted, ranging from early mycobacterial sensing leading up to subsequent killing. Emerging research in this area can be harnessed to provide valuable insights into the development of novel therapeutic and vaccine strategies against M. tuberculosis.

Wasteosomes (corpora amylacea) of human brain can be phagocytosed and digested by macrophages

Background

Corpora amylacea of human brain, recently renamed as wasteosomes, are granular structures that appear during aging and also accumulate in specific areas of the brain in neurodegenerative conditions. Acting as waste containers, wasteosomes are formed by polyglucosan aggregates that entrap and isolate toxic and waste substances of different origins. They are expelled from the brain to the cerebrospinal fluid (CSF), and can be phagocytosed by macrophages. In the present study, we analyze the phagocytosis of wasteosomes and the mechanisms involved in this process. Accordingly, we purified wasteosomes from post-mortem extracted human CSF and incubated them with THP-1 macrophages. Immunofluorescence staining and time-lapse recording techniques were performed to evaluate the phagocytosis. We also immunostained human hippocampal sections to study possible interactions between wasteosomes and macrophages at central nervous system interfaces.

Results

We observed that the wasteosomes obtained from post-mortem extracted CSF are opsonized by MBL and the C3b complement protein. Moreover, we observed that CD206 and CD35 receptors may be involved in the phagocytosis of these wasteosomes by THP-1 macrophages. Once phagocytosed, wasteosomes become degraded and some of the resulting fractions can be exposed on the surface of macrophages and interchanged between different macrophages. However, brain tissue studies show that, in physiological conditions, CD206 but not CD35 receptors may be involved in the phagocytosis of wasteosomes.

Conclusions

The present study indicates that macrophages have the machinery required to process and degrade wasteosomes, and that macrophages can interact in different ways with wasteosomes. In physiological conditions, the main mechanism involve CD206 receptors and M2 macrophages, which trigger the phagocytosis of wasteosomes without inducing inflammatory responses, thus avoiding tissue damage. However, altered wasteosomes like those obtained from post-mortem extracted CSF, which may exhibit waste elements, become opsonized by MBL and C3b, and so CD35 receptors constitute another possible mechanism of phagocytosis, leading in this case to inflammatory responses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00915-2.

Analysis of individual strategies for artificial and natural immunity with imperfectness and durability of protection

As protection against infectious disease, immunity is conferred by one of two main defense mechanisms, namely (i) resistance generated by previous infection (known as natural immunity) or (ii) by being vaccinated (known as artificial immunity). To analyze, a modified SVIRS epidemic model is established that integrates the effects of the durability of protection and imperfectness in the framework of the human decision-making process as a vaccination game. It is supposed that immunized people become susceptible again when their immunity expires, which depends on the duration of immunity. The current theory for most voluntary vaccination games assumes that seasonal diseases such as influenza are controlled by a temporal vaccine, the immunity of which lasts for only one season. Also, a novel perspective is established involving an individual's immune system combined with self-interest to take the vaccine and natural immunity obtained from infection by coupling a disease-spreading model with an evolutionary game approach over a long period. Numerical simulations show that the longer attenuation helps significantly to control the spread of disease. Also discovered is the entire mechanism of active and passive immunities, in the sense of how they coexist with natural and artificial immunity. Thus, the prospect of finding the optimal strategy for eradicating a disease could help in the design of effective vaccination campaigns and policies.

Fucoidans Stimulate Immune Reaction and Suppress Cancer Growth

BACKGROUND/AIM

Fucoidans are gaining popularity as natural immunomodulators. The aim of this study was to compare the immunological activities or both purified samples and commercially available mixtures containing fucoidan.

MATERIALS AND METHODS

We evaluated the effects of various samples on phagocytosis, mitogenic response, natural killer (NK) activity, antibody formation and inhibition of breast cancer growth.

RESULTS

We found significant immunostimulating activity, but the strength of these effects was different among individual samples.

CONCLUSION

Fucoidans have strong immunostimulating potential, including inhibition of cancer, with isolated samples offering better activity than commercial mixtures.

Outcomes associated with SARS-CoV-2 reinfection in individuals with natural and hybrid immunity

BACKGROUND

Studies comparing SARS-CoV-2 reinfection outcomes among individuals with previous infection (natural immunity) and previous infection plus vaccination (hybrid immunity) are limited.

METHODS

Retrospective cohort study comparing SARS-CoV-2 reinfection among patients with hybrid immunity (cases) and natural immunity (controls) from March 2020 to February 2022. Reinfection was defined as positive PCR > 90 days after initial laboratory-confirmed SARS-CoV-2 infection. Outcomes included time to reinfection, symptom severity, COVID-19-related hospitalization, critical COVID-19 illness (need for intensive care unit, invasive mechanical ventilation, or death), length of stay (LOS).

RESULTS

A total of 773 (42%) vaccinated and 1073 (58%) unvaccinated patients with reinfection were included. Most patients (62.7%) were asymptomatic. Median time to reinfection was longer with hybrid immunity (391 [311-440] vs 294 [229-406] days, p < 0.001). Cases were less likely to be symptomatic (34.1% vs 39.6%, p = 0.001) or develop critical COVID-19 (2.3% vs 4.3%, p = 0.023). However, there was no significant difference in rates of COVID-19-related hospitalization (2.6% vs 3.8%, p = 0.142) or LOS (5 [2-9] vs 5 [3-10] days, p = 0.446). Boosted patients had longer time to reinfection (439 [IQR 372-467] vs 324 [IQR 256-414] days, p < 0.001) and were less likely to be symptomatic (26.8% vs 38%, p = 0.002) compared to unboosted patients. Rates of hospitalization, progression to critical illness and LOS were not significantly different between the two groups.

CONCLUSIONS

Natural and hybrid immunity provided protection against SARS-CoV-2 reinfection and hospitalization. However, hybrid immunity conferred stronger protection against symptomatic disease and progression to critical illness and was associated with longer time to reinfection. The stronger protection conferred by hybrid immunity against severe outcomes due to COVID-19 should be emphasized with the public to further the vaccination effort, especially in high-risk individuals.

Rubella natural immunity among adolescent girls in Tanzania: the need to vaccinate child bearing aged women

BACKGROUND

Rubella primary infection during early stages of pregnancy is associated with high risk of congenital Rubella syndrome (CRS). Prevention of CRS in the resource-limited countries requires multiple strategies. Here, we document the data on the magnitude of Rubella natural immunity among adolescent girls which is a crucial group in devising effective control strategies to prevent CRS.

METHODS

A cross sectional study involving 397 adolescent girls was conducted in the city of Mwanza involving five secondary schools. Socio-demographic and other relevant information were collected using pre-tested data collection tool. Rubella IgG antibodies were determined using enzyme immunoassay. The presence of Rubella IgG titers of >10 IU/ml indicated natural immunity.

RESULTS

The mean age of the study participants was 15.18 ± 1.48 years. Of 397 girls, 340 (85.6%) and 57 (14.4%) were from secondary schools representing peri-urban and rural areas, respectively. Out of 397 girls, 90.4% (95% CI: 87-93) were found to be naturally immune with median Rubella IgG antibodies titers of 56.7 IU/ml interquartile range (IQR): 40.8-137. The median Rubella IgG antibodies titers were significantly high in adolescent girls from families with high socio-economic status (63.96 vs. 47.13 IU/ml, P < 0.001) and in adolescent girls from peri-urban areas of the city (63.33 vs. 39.9 IU/ml, P < 0.001).

CONCLUSION

The majority of adolescent girls in the city of Mwanza are naturally immune to Rubella virus. There is a need to compare the effectiveness of screening and vaccinating susceptible adolescent girls with the effectiveness of vaccinating all women of childbearing in controlling CRS in low-income countries.

A longitudinal study of natural antibody development to pneumococcal surface protein A families 1 and 2 in Papua New Guinean Highland children: a cohort study

BACKGROUND

Pneumococcal surface protein A (PspA), a conserved virulence factor essential for Streptococcus pneumoniae attachment to upper respiratory tract (URT) epithelia, is a potential vaccine candidate for preventing colonisation.

METHODS

This cohort study was conducted in the Asaro Valley in the Eastern Highlands Province of Papua New Guinea, of which Goroka town is the provincial capital. The children included in the analysis were participants in a neonatal pneumococcal conjugate vaccine trial (ClinicalTrials.gov NCT00219401) that was conducted between 2005 and 2009. We investigated the development of anti-PspA antibodies in the first 18 months of life relative to URT pneumococcal carriage in Papua New Guinean infants who experience one of the earliest and highest colonisation rates in the world. Blood samples and nasopharyngeal swabs were collected from a cohort of 88 children at ages 3, 9, and 18 months to quantify immunoglobulin G (IgG) levels to PspA families 1 and 2 using an enzyme-linked immunosorbent assay and to determine URT carriage.

RESULTS

Seventy-three per cent (64/88) of infants carried S. pneumoniae at age 3 months; 85 % (75/88) at 9 months, and 83 % (73/88) at 18 months. PspA-IgG levels declined between ages 3 and 9 months (p < 0.001), then increased between 9 and 18 months (p < 0.001). At age 3 months, pneumococcal carriers showed lower PspA1-IgG levels (geometric mean concentration [GMC] 602 arbitrary units [AU]/ml, 95 % confidence interval [CI] 497-728) than non-carriers (GMC 1058 AU/ml [95 % CI 732-1530]; p = 0.008), while at 9 months, PspA1- and PspA2-IgG levels were significantly higher in carriers (PspA1: 186 AU/ml, 95 % CI 136-256; PspA2: 284 AU/ml, 95 % CI 192-421) than in non-carriers (PspA1 87 AU/ml, 95 % CI 45-169; PspA2 74 AU/ml, 95 % CI 34-159) (PspA1: p = 0.037, PspA2: p = 0.003).

CONCLUSION

Our findings confirm that PspA is immunogenic and indicate that natural anti-PspA immune responses are acquired through exposure and develop with age. PspA may be a useful candidate in an infant pneumococcal vaccine to prevent early URT colonisation.

Estimating the cumulative incidence of SARS-CoV-2 infection in Costa Rica: modelling seroprevalence data in a population-based cohort

Background

The true incidence of SARS-CoV-2 infection in Costa Rica was likely much higher than officially reported, because infection is often associated with mild symptoms and testing was limited by official guidelines and socio-economic factors.

Methods

Using serology to define natural infection, we developed a statistical model to estimate the true cumulative incidence of SARS-CoV-2 in Costa Rica early in the pandemic. We estimated seroprevalence from 2223 blood samples collected from November 2020 to October 2021 from 1976 population-based controls from the RESPIRA study. Samples were tested for antibodies against SARS-CoV-2 nucleocapsid and the receptor-binding-domain of the spike proteins. Using a generalized linear model, we estimated the ratio of true infections to officially reported cases. Applying these ratios to officially reported totals by age, sex, and geographic area, we estimated the true number of infections in the study area, where 70% of Costa Ricans reside. We adjusted the seroprevalence estimates for antibody decay over time, estimated from 1562 blood samples from 996 PCR-confirmed COVID-19 cases.

Findings

The estimated total proportion infected (ETPI) was 4.0 times higher than the officially reported total proportion infected (OTPI). By December 16th, 2021, the ETPI was 47% [42-52] while the OTPI was 12%. In children and adolescents, the ETPI was 11.0 times higher than the OTPI.

Interpretation

Our findings suggest that nearly half the population had been infected by the end of 2021. By the end of 2022, it is likely that a large majority of the population had been infected.

Funding

This work was sponsored and funded by the National Institute of Allergy and Infectious Diseases through the National Cancer Institute, the Science, Innovation, Technology and Telecommunications Ministry of Costa Rica, and Costa Rican Biomedical Research Agency-Fundacion INCIENSA (grant N/A).

High vaccine effectiveness against severe COVID-19 outcomes and population preventable fraction during the Omicron era in Luxembourg: A nationwide retrospective risk factor analysis

BACKGROUND

Luxembourg experienced major consecutive SARS-CoV-2 infection waves due to Omicron variants during 2022 while having achieved a high vaccination coverage in 2021. We investigated the risk factors associated to severe outcomes (i.e., hospitalisation, deaths) and estimated vaccine effectiveness (VE) as well as the role of immunity conferred by prior infections against severe outcomes in adults.

METHODS

We linked reported SARS-CoV-2 cases among residents aged ≥ 20 years with vaccination data and SARS-CoV-2 related hospitalisations and deaths. Cases were followed-up until day 14 for COVID-19 related hospital admission and up to day 28 for mortality after a positive test. We analysed the association between the vaccination status and severe forms using proportional Cox regression, adjusting for previous infection, age, sex and nursing homes residency. VE was measured as 1-adjusted hazard ratio of vaccinated vs unvaccinated individuals. The population preventable fraction was computed using the adjusted hazard ratio and the proportion of cases within the vaccination category.

RESULTS

Between December 2021, and March 2023, we recorded 187143 SARS-CoV-2 cases, 1728 (0.93%) hospitalizations and 611 (0.33%) deaths. The risk of severe outcomes increased with age, was higher among men and nursing home residents. Compared to unvaccinated adults, VE against hospitalization was 38.8% (95%CI: 28.1%-47.8%) for a complete primary cycle of vaccination, 62.1% (95%CI: 57.0%-66.7%) for one booster, and 71.6% (95%CI: 66.7%-76.2%) for two booster doses. VE against death was respectively 49.5% (95%CI: 30.8%-63.3%), 69.0% (95%CI: 61.2%-75.3%) and 76.2% (95%CI: 68.4%-82.2%). Previous infection was not associated with lower risk of hospitalisation or mortality. The vaccination lowered mortality by 55.8 % (95%CI: 46.3%-62.8%) and reduced hospital admissions by 49.1% (95%CI: 43.4%-54.4%).

CONCLUSIONS

Complete vaccination and booster but not previous infection were protective against hospitalization and death. The vaccination program in Luxembourg led to substantial reductions in SARS-CoV-2-related mortality and hospitalizations at the population level.

An exploration of the natural and acquired immunological mechanisms to high-risk human papillomavirus infection and unmasking immune escape in cervical cancer: A concise synopsis

The most common STD that triggers cervical cancer is the human papillomavirus. More than 20 types of human papillomavirus (HPV) can induce uterine cervical cancer. Almost all women acquire genital HPV infection soon after their first intercourse, with most of them clearing the virus within 3 years. An immune response is necessary to clear. The first responders to HPV infection are the innate immune system elements composed of macrophages, keratinocytes, natural killer cells, and natural killer T-lymphocytic (NKT) cells. Cytotoxic T lymphocytes (CTLs) comprise the second line of defense and kill HPV16-infected cells expressing various peptides derived from their transforming early viral oncoproteins, mainly E2•E6. Even though HPV can manage to trick away our immune systems, first of all, it is important to emphasize that HPV replication does not kill the host cells. It does not replicate viral antigens or cause inflammation. The HPV16 E6 and E7 genes suppress host cell type 1 interferons (IFNs), which are detectable after infection. The patient may have immunological tolerance; hence, there are no costimulatory signals from inflammatory cytokines like IFNs during antigen recognition. Evidence shows that HlA class I generations have been inhibited by HPV16 E5, which could protect this tumor cell from CTL attack. HPV16 E7 is responsible for initiating immunotolerance and increasing regulatory T cells (Treg) to repress immunological regression. Evasion from immune system protection plays a critical role in the outcome of persistent HPV infection and the development of cervical cancer. Vaccination against HPV16 and 18 during adolescence is the most effective method for preventing cervical cancer in women, considering the immunological processes involved.

Reduced SARS-CoV-2 Infection Rates in Lab Workers Conducting Nucleic Acid Testing: Controlling for the Healthy Worker Effect

BACKGROUND

During the COVID-19 outbreak in December 2022 in China, some laboratory workers in SARS-CoV-2 nucleic acid testing (NAT) laboratories remained uninfected.

OBJECTIVES

To evaluate if the incidence of SARS-CoV-2 infection was reduced in laboratory workers who performed SARS-CoV-2 NAT, and whether this reduction resulted from the healthy worker effect.

METHODS

This retrospective cohort study included 423 laboratory workers from 14 SARS-CoV-2 NAT laboratories in Xiamen, China. The incidence of SARS-CoV-2 infection among laboratory workers was analysed based on whether and how long they were engaged in NAT. The healthy worker effect among the laboratory workers engaged in NAT was examined.

RESULTS

The incidence of SARS-CoV-2 infection was lower in workers engaged in SARS-CoV-2 NAT, with a gradual reduction observed as the cumulative time of SARS-CoV-2 NAT increased. A healthy worker effect was observed and eliminated after matching and stratification based on gender, age, education level, and vaccination. Workers who had ever participated in SARS-CoV-2 NAT had a lower cumulative probability of SARS-CoV-2 infection and a longer duration from vaccination to SARS-CoV-2 infection, and this trend was found to be more prominent with a longer cumulative time to SARS-CoV-2 NAT.

CONCLUSIONS

A reduction in SARS-CoV-2 infections was observed among laboratory workers conducting SARS-CoV-2 NAT after controlling for the healthy worker effect. This finding has broader implications for understanding the role of natural immunity and its interaction with vaccine immunity in defending against SARS-CoV-2 infection.

Therapeutic landscape in systemic lupus erythematosus: mtDNA activation of the cGAS-STING pathway

Mitochondrial DNA (mtDNA) serves as a pivotal immune stimulus in the immune response. During stress, mitochondria release mtDNA into the cytoplasm, where it is recognized by the cytoplasmic DNA receptor cGAS. This activation initiates the cGAS-STING-IRF3 pathway, culminating in an inflammatory response. The cGAS-STING pathway has emerged as a critical mediator of inflammatory responses in microbial infections, stress, autoimmune diseases, chronic illnesses, and tissue injuries. Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by connective tissue involvement across various bodily systems. Its hallmark is the production of numerous autoantibodies, which prompt the immune system to target and damage the body's own tissues, resulting in organ and tissue damage. Increasing evidence implicates the cGAS-STING pathway as a significant contributor to SLE pathogenesis. This article aims to explore the role of the mtDNA-triggered cGAS-STING pathway and its mechanisms in SLE, with the goal of providing novel insights for clinical interventions.

Primary biliary cirrhosis and natural immunity

Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterized by the destruction of small intrahepatic bile ducts. Complicated autoreactive responses participate in the development and progression of PBC, which involve various types of immune cells and inflammatory mediators. However, the mechanism of PBC pathogenesis is not yet clear. In this paper, we summarize the recent advances in research of PBC pathogenesis at the cellular level based mainly on the innate immunity.

Association of naturally acquired type-specific HPV antibodies and subsequent HPV re-detection: systematic review and meta-analysis

BACKGROUND

Understanding the role of naturally acquired (i.e., infection-induced) human papillomavirus (HPV) antibodies against reinfection is important given the high incidence of this sexually transmitted infection. However, the protective effect of naturally acquired antibodies in terms of the level of protection, duration, and differential effect by sex remains incompletely understood. We conducted a systematic review and a meta-analysis to (1) strengthen the evidence on the association between HPV antibodies acquired through past infection and subsequent type-specific HPV detection, (2) investigate the potential influence of type-specific HPV antibody levels, and (3) assess differential effects by HIV status.

METHODS

We searched Embase and Medline databases to identify studies which prospectively assessed the risk of type-specific HPV detection by baseline homologous HPV serostatus among unvaccinated individuals. Random-effect models were used to pool the measures of association of naturally acquired HPV antibodies against subsequent incident detection and persistent HPV positivity. Sources of heterogeneity for each type were assessed through subgroup analyses stratified by sex, anatomical site of infection, male sexual orientation, age group, and length of follow-up period. Evidence of a dose-response relationship of the association between levels of baseline HPV antibodies and type-specific HPV detection was assessed. Finally, we pooled estimates from publications reporting associations between HPV serostatus and type-specific HPV detection by baseline HIV status.

RESULTS

We identified 26 publications (16 independent studies, with 62,363 participants) reporting associations between baseline HPV serostatus and incident HPV detection, mainly for HPV-16 and HPV-18, the most detected HPV type. We found evidence of protective effects of baseline HPV seropositivity and subsequent detection of HPV DNA (0.70, 95% CI 0.61-0.80, NE = 11) and persistent HPV positivity (0.65, 95% CI 0.42-1.01, NE = 5) mainly for HPV-16 among females, but not among males, nor for HPV-18. Estimates from 8 studies suggested a negative dose-response relationship between HPV antibody level and subsequent detection among females. Finally, we did not observe any differential effect by baseline HIV status due to the limited number of studies available.

CONCLUSION

We did not find evidence that naturally acquired HPV antibodies protect against subsequent HPV positivity in males and provide only modest protection among females for HPV-16. One potential limitation to the interpretation of these findings is potential misclassification biases due to different causes.