Validation of a double-color ELISpot assay of IFN-γ and IL-4 production in human peripheral blood mononuclear cells

The Enzyme-Linked ImmunoSpot (ELISpot) assay detects cytokines secreted during T cell-specific immune responses against pathogens. As this assay has acquired importance in the clinical setting, standard bioanalytical evaluation of this method is required. Here, we describe a formal bioanalytical validation of a double-color ELISpot assay for the evaluation of IFN-γ and IL-4 released by T helper 1 and T helper 2 cells, respectively. As recommended by international guidelines, the parameters assessed were: range and detection limits (limit of detection, LOD; upper and lower limit of quantification, ULOQ and LLOQ), Linearity, Relative Accuracy, Repeatability, Intermediate Precision, Specificity and Robustness. The results obtained in this validation study demonstrate that this assay meets the established acceptability criteria. ELISpot is therefore a reliable technique for measuring T cell-specific immune responses against various antigens of interest.

SARS-CoV-2 epidemiological trend before vaccination era: a seroprevalence study in Apulia, Southern Italy, in 2020

Aim

The present study aimed at assessing the prevalence of antibodies against SARS-CoV-2 in the general population in the province of Bari (Apulia region, Southern Italy) during the year 2020.

Subject and methods

In this study, 1325 serum samples collected from January to December 2020 were tested for the presence of IgM and IgG antibodies against whole-virus SARS-CoV-2 antigen by commercial ELISA. Positive samples were further tested by in-house ELISA for the detection of anti-receptor binding domain (RBD) IgM and IgG antibodies and by micro-neutralization (MN) assay for the detection of neutralizing antibody.

Results

One hundred (7.55%) samples had the presence of at least one antibody class against SARS-CoV-2 by commercial ELISA, of which 88 (6.6%) showed IgG and 19 (1.4%) showed IgM antibodies. The proportion of samples with IgG antibodies increased from 1.9% in January-February to 9.6% in November-December, while no significant increase was observed for IgM. When tested by in-house ELISA and MN assay, 17.0% and 31.6% were found positive to RBD IgG and RBD IgM, respectively, while 12.0% showed neutralizing antibody.

Conclusion

The proportion of samples with SARS-CoV-2 IgG antibodies increased during 2020, especially in the second half of the year, consistent with data reported by the routine epidemiological surveillance of SARS-CoV-2 cases. Despite the high number of reported cases, the seroprevalence values are relatively low, and only a small proportion of samples had neutralizing antibodies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10389-023-01834-3.

SARS-CoV-2 Seroconversion and Pregnancy Outcomes in a Population of Pregnant Women Recruited in Milan, Italy, between April 2020 and October 2020

The possible link between SARS-CoV-2 infection and adverse pregnancy outcomes has so far demonstrated heterogeneous results in terms of maternal, fetal, and neonatal complications. We aim to investigate the correlation between SARS-CoV-2 seroconversion and/or neutralization titer and pregnancy outcomes. We analyzed a population of 528 pregnant women followed up from the first trimester of gestation until delivery. For each woman, we collected a first blood sample between 11 and 13 weeks of gestation and a second sample in the perinatal period (between peripartum and puerperium) to assess the presence of SARS-CoV-2 antibodies and/or microneutralization titer (MN titer). Data on pregnancy outcomes (gestational age at delivery, preterm birth before 34 weeks, hypertensive disorders, gestational diabetes, and abnormal fetal growth) were collected. We observed that serologic status per se is not associated with major pregnancy complications. On the contrary, the MN titer was associated with increased odds of gestational diabetes. Although we mainly reported asymptomatic SARS-CoV-2 infections and the absence of severe maternal and neonatal adverse outcomes, SARS-CoV-2 infection might challenge the maternal immune system and explain the moderate increase in adverse outcome odds.

A serological investigation in Southern Italy: was SARS-CoV-2 circulating in late 2019?

In March 2020, the first pandemic caused by a coronavirus was declared by the World Health Organization. Italy was one of the first and most severely affected countries, particularly the northern part of the country. The latest evidence suggests that the virus could have been circulating, at least in Italy, before the first autochthonous SARS-COV-2 case was detected in February 2020. The present study aimed to investigate the presence of antibodies against SARS-CoV-2 in human serum samples collected in the last months of 2019 (September–December) in the Apulia region, Southern Italy. Eight of 455 samples tested proved positive on in-house receptor-binding-domain-based ELISA. Given the month of collection of the positive samples, these findings may indicate early circulation of SARS-CoV-2 in Apulia region in the autumn of 2019. However, it cannot be completely ruled out that the observed sero-reactivity could be an unknown antigen specificity in another virus to which subjects were exposed containing an epitope adventitiously cross-reactive with an epitope of SARS-CoV-2.

The neutralizing response to SARS-CoV-2 Omicron variants BA.1 and BA.2 in COVID-19 patients and homologous and heterologous vaccinees

The rapid replacement of Omicron BA.1 by BA.2 sublineage is very alarming, raising the question of whether BA.2 can escape the immunity acquired after BA.1 infection. We compared the neutralizing activity toward the Omicron BA.1 and BA.2 sub-lineages in five groups: COVID-19 patients; subjects who had received two doses of mRNA vaccine; subjects naturally infected with SARS-CoV-2 who had received two doses of mRNA; and subjects who had received three doses of homologous or heterologous vaccine. The results obtained highlight the importance of vaccine boosters in eliciting neutralizing antibody responses against Omicron sub-lineages, and suggest that the adenovirus vectored vaccine elicits a lower response against BA.1 than against BA.2 sub-lineage.

Immune response to SARS-CoV-2 Omicron variant in patients and vaccinees following homologous and heterologous vaccinations

The SARS-CoV-2 Omicron variant has rapidly replaced the Delta variant of concern. This new variant harbors worrisome mutations on the spike protein, which are able to escape the immunity elicited by vaccination and/or natural infection. To evaluate the impact and susceptibility of different serum samples to the Omicron variant BA.1, samples from COVID-19 patients and vaccinated individuals were tested for their ability to bind and neutralize the original SARS-CoV-2 virus and the Omicron variant BA.1. COVID-19 patients show the most drastic reduction in Omicron-specific antibody response in comparison with the response to the wild-type virus. Antibodies elicited by a triple homologous/heterologous vaccination regimen or following natural SARS-CoV-2 infection combined with a two-dose vaccine course, result in highest neutralization capacity against the Omicron variant BA.1. Overall, these findings confirm that vaccination of COVID-19 survivors and booster dose to vaccinees with mRNA vaccines is the correct strategy to enhance the antibody cross-protection against Omicron variant BA.1.

SARS-CoV-2 Circulation during the First Year of the Pandemic: A Seroprevalence Study from January to December 2020 in Tuscany, Italy

Italy was the second country affected by the SARS-CoV-2 pandemic; the virus spread mainly in Northern Italy with a subsequent diffusion to the center and southern part of the country. In this study, we aimed to assess the prevalence of antibodies against SARS-CoV-2 in the general population of the Siena province in the Tuscany region (Central Italy) during 2020. A total of 2480 serum samples collected from January to December 2020 were tested for IgM and IgG antibodies against SARS-CoV-2 by a commercial ELISA. Positive and borderline samples were further tested for the presence of anti-receptor-binding domain (RBD) IgM and IgG antibodies by an in-house ELISA and by a micro-neutralization assay. Out of the 2480 samples tested by the commercial ELISA, 81 (3.3%) were found to be positive or borderline for IgG and 58 (2.3%) for IgM in a total of 133 samples (5.4%) found to be positive or borderline for at least one antibody class. When the commercial ELISA and in-house ELISA/micro-neutralization assay results were combined, 26 samples (1.0%) were positive for RBD IgG, 11 (0.4%) for RBD IgM, and 23 (0.9%) for a neutralizing antibody. An increase in seroprevalence was observed during the year 2020, especially from the end of summer, consistent with the routine epidemiological surveillance of COVID-19 cases.

Epidemic Preparedness-Leishmania tarentolae as an Easy-to-Handle Tool to Produce Antigens for Viral Diagnosis: Application to COVID-19

To detect and prevent emerging epidemics, discovery platforms are urgently needed, for the rapid development of diagnostic assays. Molecular diagnostic tests for COVID-19 were developed shortly after the isolation of SARS-CoV-2. However, serological tests based on antiviral antibody detection, revealing previous exposure to the virus, required longer testing phases, due to the need to obtain correctly folded and glycosylated antigens. The delay between the identification of a new virus and the development of reliable serodiagnostic tools limits our readiness to tackle future epidemics. We suggest that the protozoan Leishmania tarentolae can be used as an easy-to-handle microfactory for the rapid production of viral antigens to face emerging epidemics. We engineered L. tarentolae to express the SARS-CoV-2 receptor-binding domain (RBD) and we recorded the ability of the purified RBD antigen to detect SARS-CoV-2 infection in human sera, with a sensitivity and reproducibility comparable to that of a reference antigen produced in human cells. This is the first application of an antigen produced in L. tarentolae for the serodiagnosis of a Coronaviridae infection. On the basis of our results, we propose L. tarentolae as an effective system for viral antigen production, even in countries that lack high-technology cell factories.

Biocompatible pectin-based hybrid hydrogels for tissue engineering applications

Hybrid hydrogels made of chemically modified pectin, gelatin and xanthan gum have been formulated and processed through a double crosslinking step, aimed at wound healing applications.

Development of a yeast-based system to identify new hBRAFV600E functional interactors

BRAFV600E is a mutant Ser-Thr protein kinase that plays a crucial role in many types of cancer, including melanoma. Despite several aspects of BRAFV600E biology have been already elucidated, the proteins that regulate its expression and activity remain largely unknown, hampering our capacity to control its unrestrained effects. Here, we propose yeast Saccharomyces cerevisiae as a model system that can be used to achieve a better understanding of the regulation of human BRAFV600E.By showing that in osmotic stress conditions hBRAFV600E can rescue the growth of strains carrying a double or triple deletion in MAPKKK belonging to the HOG pathway, we demonstrate that this oncogenic kinase is active in yeast even if it does not have an ortholog. Moreover, we report that, in the yeast ptp3∆ptc1∆ strain that is deleted in the genes encoding for two phosphatases responsible for Hog1 de-phoshorylation, hBRAFV600E mimics the toxicity observed in the presence of constitutive Hog1 activation. Finally, we exploit such a toxicity to perform a functional screening of a human cDNA library, looking for cDNAs able to rescue yeast growth. In this way, we identify SMIM10, a mitochondrial protein that in melanoma cells selectively downregulates BRAFV600E RNA and protein levels, by acting indirectly at the post-transcriptional level. Upon SMIM10 overexpression, BRAFV600E melanoma cells show disrupted mitochondrial structure/function and undergo senescence. They also show decreased ability to proliferate and form colonies, as well as increased sensitivity to the BRAF inhibitor vemurafenib. Interestingly, the analysis of TCGA melanoma samples indicates that patients with higher SMIM10 levels have a better prognosis. Therefore, these data suggest that SMIM10 exerts an oncosuppressive role in melanoma cells.Taken together, our results unveil the potential of S. cerevisiae to study hBRAFV600E, to populate the network of its functional interactors and, in doing so, to uncover new cancer-associated genes with therapeutic potential.

MAPK15 is part of the ULK complex and controls its activity to regulate early phases of the autophagic process

Autophagy, a pathway for bulk protein degradation and removal of damaged organelles, represents one of the major responses of cells to stress, thereby exerting a strict control on their correct functioning. Consequently, this process has been involved in the pathogenesis and therapeutic responses of several human diseases. Mitogen-activated protein (MAP) kinase 15 (MAPK15) is an atypical member of the MAP kinase family that recently emerged as a key modulator of autophagy and, through this, of cell transformation. Still, no information is available about signaling pathways mediating the effect of MAPK15 on this process, nor is it known which phase of autophagosome biogenesis is affected by this MAP kinase. Here, we demonstrate that MAPK15 stimulated 5'-AMP-activated protein kinase-dependent activity of UNC-51-like kinase 1 (ULK1), the only protein kinase among the ATG-related proteins, toward downstream substrates and signaling intermediates. Importantly, MAPK15 directly interacted with the ULK1 complex and mediated ULK1 activation induced by starvation, a classical stimulus for the autophagic process. In turn, ULK1 and its highly homologous protein ULK2 are able to transduce MAPK15 signals stimulating early phases of autophagosomal biogenesis in a multikinase cascade that offers numerous potential targets for future therapeutic intervention in cancer and other autophagy-related human diseases.

Targeted inhibition of Hedgehog-GLI signaling by novel acylguanidine derivatives inhibits melanoma cell growth by inducing replication stress and mitotic catastrophe

Aberrant activation of the Hedgehog (HH) signaling is a critical driver in tumorigenesis. The Smoothened (SMO) receptor is one of the major upstream transducers of the HH pathway and a target for the development of anticancer agents. The SMO inhibitor Vismodegib (GDC-0449/Erivedge) has been approved for treatment of basal cell carcinoma. However, the emergence of resistance during Vismodegib treatment and the occurrence of numerous side effects limit its use. Our group has recently discovered and developed novel and potent SMO inhibitors based on acylguanidine or acylthiourea scaffolds. Here, we show that the two acylguanidine analogs, compound (1) and its novel fluoride derivative (2), strongly reduce growth and self-renewal of melanoma cells, inhibiting the level of the HH signaling target GLI1 in a dose-dependent manner. Both compounds induce apoptosis and DNA damage through the ATR/CHK1 axis. Mechanistically, they prevent G2 to M cell cycle transition, and induce signs of mitotic aberrations ultimately leading to mitotic catastrophe. In a melanoma xenograft mouse model, systemic treatment with 1 produced a remarkable inhibition of tumor growth without body weight loss in mice. Our data highlight a novel route for cell death induction by SMO inhibitors and support their use in therapeutic approaches for melanoma and, possibly, other types of cancer with active HH signaling.