Durability of the humoral immune response in recovered COVID-19 patients

BackgroundThe immunological factors involved in protection against the disease caused by SARS-CoV-2 are insufficiently defined and understood. However, previous knowledge pertaining to the related SARS virus and other human coronaviruses may prove useful. Population-based serosurveys measuring anti-SARS-CoV-2 antibodies may provide a pattern for estimating infection degrees and observing the development of the epidemic. In this study, we aimed to investigate the persistence of antibody against the SARS-CoV-2 in recovered patients in Al Madinah region of Saudi Arabia.Materials and methodsA total of 150 recovered COVID-19 patients participated in this study. All the patients tested positive for the presence of SARS-CoV-2 RNA, using qualitative RT-PCR. An ELISA was used to measure anti-Spike (S) IgG antibodies in serum samples and screen for their persistence at various time points post-infection.ResultsThe patients were categorized as asymptomatic (27.3%), mild (28%) and moderate (44.7%) according to the disease severity. Amongst them, 35.3% were females (n = 53) and 64.7% were males (n = 97). Significant anti-S IgG antibody levels were observed among the different groups, with the patients in moderate group exhibiting the highest levels followed by the mild group; while the lowest levels were detected among the asymptomatic. There was a significant positive correlation between the patients’ age and anti-S IgG antibody concentrations (Pearson r = 0.45; p < 0.001).ConclusionOur findings provide a solid evidence to support the use of an anti-S IgG ELISA as a diagnostic tool to indicate SARS-CoV-2 infection. IgG seropositivity was sustained in recovered patients up to a hundred days' post-infection, the latest time point for antibody measurement in our study. Ours is the first report in Saudi Arabia to investigate the durability of humoral immune response in recovered COVID-19 patients.     

Emergency response for evaluating SARS-CoV-2 immune status,seroprevalence and convalescent plasma in Argentina

We report the emergency development and application of a robust serologic test to evaluate acute and convalescent antibody responses to SARS-CoV-2 in Argentina. The assays, COVIDAR IgG and IgM, which were produced and provided for free to health authorities, private and public health institutions and nursing homes, use a combination of a trimer stabilized spike protein and the receptor binding domain (RBD) in a single enzyme-linked immunosorbent assay (ELISA) plate. Over half million tests have already been distributed to detect and quantify antibodies for multiple purposes, including assessment of immune responses in hospitalized patients and large seroprevalence studies in neighborhoods, slums and health care workers, which resulted in a powerful tool for asymptomatic detection and policy making in the country. Analysis of antibody levels and longitudinal studies of symptomatic and asymptomatic SARS-CoV-2 infections in over one thousand patient samples provided insightful information about IgM and IgG seroconversion time and kinetics, and IgM waning profiles. At least 35% of patients showed seroconversion within 7 days, and 95% within 45 days of symptoms onset, with simultaneous or close sequential IgM and IgG detection. Longitudinal studies of asymptomatic cases showed a wide range of antibody responses with median levels below those observed in symptomatic patients. Regarding convalescent plasma applications, a protocol was standardized for the assessment of end point IgG antibody titers with COVIDAR with more than 500 plasma donors. The protocol showed a positive correlation with neutralizing antibody titers, and was used for clinical trials and therapies across the country. Using this protocol, about 80% of convalescent donor plasmas were potentially suitable for therapies. Here, we demonstrate the importance of providing a robust and specific serologic assay for generating new information about antibody kinetics in infected individuals and mitigation policies to cope with pandemic needs.     

In vitro cell culture model of human nasal-associated lymphoid tissue (NALT) to evaluate the humoral immune response to SARS-CoV-2 spike proteins

To date, coronavirus disease 2019 (COVID-19) continues to be considered a pandemic worldwide, with a mild to severe disease presentation that is sometimes associated with serious complications that are concerning to global health authorities. Scientists are working hard to understand the pathogenicity of this novel virus, and a great deal of attention and effort has been focused on identifying therapeutics and vaccines to control this pandemic.MethodsThis study used tonsils removed from twelve patients who underwent an elective tonsillectomy in the ear, nose, and throat (ENT) department at Saudi Germany Hospital, Madinah, Saudi Arabia. Tonsillar mononuclear cells (MNCs) were separated and co-cultured in RPMI complete medium in the presence and absence of viral spike (S) proteins (the full-length S, S1 subunit, and S2 subunit proteins). Enzyme-linked immunosorbent assay (ELISA) was used to measure secreted antibody concentrations following stimulation.ResultsThe in vitro human nasal-associated lymphoid tissue (NALT) cell culture model was successfully used to evaluate the humoral immune response against SARS-CoV-2- S protein. Significant (p < 0.0001, n = 12) levels of specific, anti-S IgG, IgM, and IgA antibody responses were detected in cells culture supernatanat folloeing stimulation with the full-length S protein compared with unstimulated cells. In contrast, S1 and S2 subunit proteins alone failed to induce a mucosal humoral immune response following tonsillar MNC stimulation.ConclusionWe demonstrated a successful human NALT in vitro cell culture model that was used to study the mucosal humoral immune response to the SARS-CoV-2 S protein. This model could be advantageous for the in-depth study of cellular immune responses to the S protein and other viral antigens, such as nucleocapsid and matrix antigen. The S protein appears to be the important viral protein that may be able to mimic the natural infection process intranasally and should be studied as a component of a candidate vaccine.     

Identification of target proteins of clinical immunity to Plasmodium falciparum in a region of low malaria transmission

The target molecules of antibodies against falciparum malaria remain largely unknown. Recently we have identified multiple proteins as targets of immunity against Plasmodium falciparum using African serum samples. To investigate whether potential targets of clinical immunity differ with transmission intensity, we assessed immune responses in residents of low malaria transmission region in Thailand. Malaria asymptomatic volunteers (Asy: n = 19) and symptomatic patients (Sym: n = 21) were enrolled into the study. Serum immunoreactivity to 186 wheat germ cell-free system (WGCFS)-synthesized recombinant P. falciparum asexual-blood stage proteins were determined by AlphaScreen, and subsequently compared between the study groups. Forty proteins were determined as immunoreactive with antibody responses to 35 proteins being higher in Asy group than in Sym group. Among the 35 proteins, antibodies to MSP3, MSPDBL1, RH2b, and MSP7 were significantly higher in Asy than Sym (unadjusted p < 0.005) suggesting these antigens may have a protective role in clinical malaria. MSP3 reactivity remained significantly different between Asy and Sym groups even after multiple comparison adjustments (adjusted p = 0.033). Interestingly, while our two preceding studies using African sera were conducted differently (e.g., cross-sectional vs. longitudinal design, observed clinical manifestation vs. functional activity), those studies similarly identified MSP3 and MSPDBL1 as potential targets of protective immunity. This study further provides a strong rationale for the application of WGCFS-based immunoprofiling to malaria vaccine candidate and biomarker discovery even in low or reduced malaria transmission settings.     

Seroprevalence and asymptomatic carrier status of SARS-CoV-2 in Wuhan City and other places of China

Wuhan City (WH) in China was the first place to report COVID-19 in the world and the outbreak of COVID-19 was controlled in March of 2020 in WH. It is unclear what percentage of people were infected with SARS-CoV-2 and what percentage of population is carriers of SARS-CoV-2 in WH. We retrospectively analyzed the SARS-CoV-2 IgG and IgM antibody positive rates in 63,107 healthy individuals from WH and other places of China using commercial colloidal gold detection kits from March 6 to May 3, 2020. Statistical approaches were utilized to explore the difference and correlation for the seropositive rate of IgG and IgM antibody on the basis of sex, age group, geographic region and detection date. The total IgG and IgM antibody positive rate of SARS-CoV-2 was 1.68% (186/11,086) in WH, 0.59% (226/38,171) in Hubei Province without Wuhan (HB), and 0.38% (53/13,850) in the nation except for Hubei Province (CN), respectively. The IgM positive rate was 0.46% (51/11,086) in WH, 0.13% (51/38,171) in HB, and 0.07% (10/13,850) in CN. The incidence of IgM positive rates in healthy individuals increased from March 6 to May 3, 2020 in WH. Female and older age had a higher probability of becoming infected than males (OR = 1.34; 95% CI: 1.08–1.65) or younger age (OR = 2.25; 95% CI: 1.06–4.78). The seroprevalence of SARS-CoV-2 was relatively low in WH and other places of China, but it is significantly high in WH than other places of China; a large amount of asymptomatic carriers of SARS-CoV-2 existed after elimination of clinical cases of COVID-19 in Wuhan City. Therefore, SARS-CoV-2 may exist in a population without clinical cases for a long period.     

Primary alveolar echinococcosis: Course of larval development and antibody responses in intermediate host rodents with different genetic backgrounds after oral infection with eggs of Echinococcus multilocularis

We investigated parasite establishment, subsequent larval development and antibody responses in gerbils, cotton rats and 4 inbred mouse strains until 16 weeks post inoculation (p.i.) with 200 eggs of Echinococcus multilocularis. The rate of parasite establishment in the liver determined at 4 weeks p.i. was highest in DBA/2, followed by AKR/N, C57BL/10 and C57BL/6 mice, whereas gerbils harboured few parasite foci. The accurate number of liver lesions in cotton rats could not be determined due to rapid growth and advanced multivesiculation of the parasite observed at 2 weeks p.i. The course of larval development was most advanced in DBA/2 mice with mature protoscolex formation at 16 weeks p.i., followed by AKR/N harbouring metacestodes with sparsely distributed immature protoscoleces. On the other hand, C57BL/6 and C57BL/10 mice had infertile metacestodes without any protoscolex formation. The parasite growth in mice was totally slower than those in gerbils and cotton rats. Specific IgG and IgM responses against 3 types of native crude antigens of larval E. multilocularis were evaluated using somatic extracts of and vesicle fluid of metacestode, and somatic extracts from purified protoscoleces. The 4 mouse strains demonstrated basically similar kinetics with apparent IgG and IgM increases at 9 weeks p.i. and thereafter, except C57BL/10, exhibited higher levels of IgM against crude antigens at some time point of infection. On the other hand, a follow-up determination of specific IgG and IgM levels against recombinant antigens from larval E. multilocularis revealed that each mouse strain showed different antibody-level kinetics. The findings in the present study demonstrate that the course of host–parasite interactions in primary alveolar echinococcosis, caused by larval E. multilocularis, clearly varies among intermediate host rodents with different genetic backgrounds.     

Characterization of altered genomic landscape of SARS-CoV-2 variants isolated in Saudi Arabia in a comparative in silico study

SARS-CoV-2 has become one of the unprecedented global health challenge for human population. Genomic signature studies of SARS-CoV-2 reveals relation between geographical location of the isolates and genetic diversity. The present work is an in silico, cross sectional study aimed to determine the genetic heterogeneity of SARS-CoV-2 variants isolated in Saudi Arabia compared to the first isolated strain NC_045512 (reference sequence). Each sequence was aligned against the reference sequence using local alignment search tool (NCBI) Nucleotide-BLAST. A total of 58 SARS-CoV-2 genomes were isolated in KSA and retrieved from NCBI. Our study shows that KSA variants demonstrated homology ranging between 99.96 and 99.98 % compared to the reference strain. There are 89 nucleotide changes that have been identified among the KSA variants; the most common nucleotide change was C: T accounting for 50.6% (45/89). These nucleotides changes resulted in 53.9% (48/89) missense mutations and 42.7% (38/89) silent mutations; while the majority of mutations- 48.3% (43/89) occurred in ORF1ab gene. All structural genes displayed mutations; N gene harbored 16.9% (15/89) mutations, S gene displayed 15.7% (14/89) mutations, M gene exhibited 2.2% (2/89) mutations and E gene showed only 1 mutation which was silent. The most frequently changed nucleotide was C3037T (silent mutation) and A23403G (D614G), each of which occurred in 57 variants out of 58 followed by C14408T (P4715L) and C241T (5′UTR) which were found in 56 and 55 variants respectively. The Phylogenetic trees showed that SARS-CoV-2 variants isolated in Saudi Arabia clustered together closely.     

A preliminary study on serological assay for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 238 admitted hospital patients

In this study, we aimed to evaluate the diagnostic value of serological assay for SARS-CoV-2. A newly-developed ELISA assay for IgM and IgG antibodies against N protein of SARS-CoV-2 was used to screen the serums of 238 admitted hospital patients between February 6 and February 14, 2020 with confirmed or suspected SARS-CoV-2. SARS-CoV-2 RNA was detected on pharyngeal swab specimens using real time RT-PCR. 194 (81.5%) of the serums were detected to be antibody (IgM and/or IgG) positive, significantly higher than the positive rate of viral RNA (64.3%). There was no difference in the positive rate of antibodies between the confirmed patients (83.0%, 127/153) and the suspected patients (78.8%, 67/85), whose nucleic acid tests were negative. The antibody positive rates were very low in the first five days after initial onset of symptoms, and then rapidly increased as the disease progressed. After 10 days, the antibody positive rates jumped from below 50% to over 80%. However, the positive rates of viral RNA maintained above 60% in the first 11 days after initial onset of symptoms, and then rapidly decreased. Overall, the suspected patients were most likely infected by SARS-CoV-2. Before the 11th day after initial onset of symptoms, nucleic acid test is key for confirmation of viral infection. The combination of serological assay can greatly improve the diagnostic efficacy. After the 11th day post-disease onset, the diagnosis for viral infection should be majorly dependent on serological assay.     

Affinity chromatographic purification of human immunoglobulin M from human B lymphocyte cell culture supernatant

Compared to immunoglobulin G purification with extensively studied affinity ligands such as protein A and protein G, little work has been done on affinity chromatographic purification of immunoglobulin M. Hexamer peptide ligand HWRGWV, previously shown to bind specifically to the Fc fragment of IgG, also demonstrated potential for IgM purification. This study presents further characterization and investigation of this ligand for its potential for purification of IgM. Different running conditions were employed in order to improve the recovery and purity of IgM. The final recovery and purity of the antibody is feedstock dependent, but can reach levels of both recovery and purity as high as 95%. The dependence of the recovery and purity on total loading amount and initial IgM concentration were investigated and discussed. Although relatively low dynamic binding capacities (DBC) in the range of 4.6–13.1 mg IgM/mL resin at linear flow rates from 173 to 35 cm/h were obtained for IgM compared to IgG because of the large molecular weight of IgM, the DBC value of HWRGWV for IgM is much greater than protein-based IgM affinity ligands found in the literature and is competitive with current commercially available affinity ligands, such as KAPTIVE-M, CaptureSelect IgM and Ultralink Immobilized Mannan Binding Protein.     

Salivary DNA,lipid, and protein oxidation in nonsmokers with periodontal disease

Reactive oxygen species (ROS) are implicated in the destruction of the periodontium during periodontitis. The imbalance in oxidant activity may be a key factor.The aim of this paper is to determine whether periodontitis is associated with increased oxidative damage to DNA, lipids, and proteins and modification of total antioxidant capacity (TAC) in saliva. Saliva was collected from 58 periodontitis patients and 234 healthy controls, all nonsmokers. Periodontal disease status was characterized using the Community Periodontal Index of Treatment Needs (CPITN). Assays for 8-OHdG (ELISA), 8-epi-PGF2α (ELISA), and total protein carbonyls (ELISA), and oxy-blotting (Western)/mass spectrometry were performed to quantify oxidative damage to nucleic acids, lipids, total and individual proteins, respectively, in whole nonstimulated saliva. Salivary TAC was measured by inhibition of ABTS oxidation by metmyoglobin. We observed (i) significantly higher levels of 8-OHdG, 8-epi-PGF2α, and carbonylated proteins in saliva of periodontal patients as compared with controls (P = 0.0003, < 0.0001 and < 0.0001); (ii) 8-OHdG, 8-epi-PGF2α, and carbonylated proteins were independently negatively associated with CPITN (P = 0.004, 0.02, and < 0.0001); (iii) a positive correlation between salivary TAC and periodontal disease status in the study group (P < 0.0001); and (iv) specific oxidation of transferrin, human IgG1 heavy chain fragment, and salivary amylase in periodontitis. Periodontal disease is associated with increased oxidative modification of salivary DNA, lipids, and proteins. Augmented salivary total antioxidant capacity may represent an adaptive response to oxidative stress. Salivary amylase, transferrin, and human IgG1 heavy chain fragments are particularly prone to enhanced oxidation in periodontitis.     

Comparison of diagnostic performances of ten different immunoassays detecting anti-CCHFV IgM and IgG antibodies from acute to subsided phases of Crimean-Congo hemorrhagic fever

Crimean-Congo Hemorrhagic Fever Virus (CCHFV) is a geographically widespread tick-borne arbovirus that has been recognized by the WHO as an emerging pathogen needing urgent attention to ensure preparedness for potential outbreaks. Therefore, availability of accurate diagnostic tools for identification of acute cases is necessary.A panel comprising 121 sequential serum samples collected during acute, convalescent and subsided phase of PCR-proven CCHFV infection from 16 Kosovar patients was used to assess sensitivity. Serum samples from 60 healthy Kosovar blood donors were used to assess specificity. All samples were tested with two IgM/IgG immunofluorescence assays (IFA) from BNITM, the CCHFV Mosaic 2 IgG and IgM indirect immunofluorescence tests (IIFT) from EUROIMMUN, two BlackBox ELISAs for the detection of CCHFV-specific IgM and IgG antibodies (BNITM), two Anti-CCHFV ELISAs IgM and IgG from EUROIMMUN using recombinant structural proteins of CCHFV antigens, and two ELISAs from Vector-Best (IgM: μ-capture ELISA, IgG: indirect ELISA using immobilized CCHFV antigen). Diagnostic performances were compared between methods using sensitivity, specificity, concordance and degree of agreement with particular focus on the phase of the infection.In early and convalescent phases of infection, the sensitivities for detecting specific IgG antibodies differed for the ELISA test. The BlackBox IgG ELISA yielded the highest, followed by the EUROIMMUN IgG ELISA and finally the VectorBest IgG ELISA with the lowest sensitivities. In the subsided phase, the VectorBest IgM ELISA detected a high rate of samples that were positive for anti-CCHFV IgM antibodies. Both test systems based on immunofluorescence showed an identical sensitivity for detection of anti-CCHFV IgM antibodies in acute and convalescent phases of infection.Available serological test systems detect anti-CCHFV IgM and IgG antibodies accurately, but their diagnostic performances vary with respect to the phase of the infection.     

Clinical and genomic data of sars-cov-2 detected in maternal–fetal interface during the first wave of infection in Brazil

Brazil has the highest SARS-CoV-2 case-fatality rate in pregnant women in the Americas. In this study, clinical and virological findings of five mildly symptomatic pregnant women and their infected fetuses/newborns treated at a referral hospital for COVID19-pregnant women in Midwestern Brazil are reported. Mother and fetal samples were tested by RT-qPCR, ECLIA and Illumina MiSeq sequencing. From the five cases, one resulted in spontaneous abortion, one was stillborn, two were preterm births and one full-term birth. Maternal and fetal placenta, newborn and stillborn secretions were SARS-CoV-2+; one neonate developed ground-glass opacities in his lungs. One neonate's umbilical cord was IgG+ and all were IgM negative upon hospital discharge. Genomes recovered from two placentas belong to the B.1.1.28 and B.1.1.33 lineages and present nonsynonymous mutations associated with virus fitness and infectivity; other not frequently reported mutations (B.1.1.33: NSP3 V2090G, M A2S and ORF3ab S253P and Y264N; B.1.1.28: NSP3 E995D, NSP12 R240K, NSP14H1897Y and in ORF7b V21F) were found in proteins involved in viral replication, viral induction of apoptosis, viral interference on interferon and on NF-Κβ pathways. Phylogeny indicates the south of Brazil as the possible origin of these lineages circulating in Mato Grosso State. These findings contribute to describe SARS-CoV-2 infection and outcomes in pregnant women and their fetuses, at any stage of gestation and even in mild symptomatic cases.     

Molecular dynamic and bioinformatic studies of metformin-induced ACE2 phosphorylation in the presence of different SARS-CoV-2 S protein mutations

The SARS-CoV-2 infection activates host kinases and causes high phosphorylation in both the host and the virus. There were around 70 phosphorylation sites found in SARS-CoV-2 viral proteins. Besides, almost 15,000 host phosphorylation sites were found in SARS-CoV-2-infected cells. COVID-19 is thought to enter cells via the well-known receptor Angiotensin-Converting Enzyme 2 (ACE2) and the serine protease TMPRSS2. Substantially, the COVID-19 infection doesn’t induce phosphorylation of the ACE2 receptor at Serin-680(s680). Metformin's numerous pleiotropic properties and extensive use in medicine including COVID-19, have inspired experts to call it the “aspirin of the twenty-first century”. Metformin's impact on COVID-19 has been verified in clinical investigations via ACE2 receptor phosphorylation at s680. In the infection of COVID-19, sodium-dependent transporters including the major neutral amino acid (B⁰AT1) is regulated by ACE2. The structure of B⁰AT1 complexing with the COVID-19 receptor ACE2 enabled significant progress in the creation of mRNA vaccines. We aimed to study the impact of the interaction of the phosphorylation form of ACE2-s680 with wild-type (WT) and different mutations of SARS-CoV-2 infection such as delta, omicron, and gamma (γ) on their entrance of host cells as well as the regulation of B⁰AT1by the SARS-CoV-2 receptor ACE2. Interestingly, compared to WT SARS-CoV-2, ACE2 receptor phosphorylation at s680 produces conformational alterations in all types of SARS-CoV-2. Furthermore, our results showed for the first time that this phosphorylation significantly influences ACE2 sites K625, K676, and R678, which are key mediators for ACE2-B⁰AT1 complex.     

Disease characteristics and serological responses in patients with differing severity of COVID-19 infection: A longitudinal cohort study in Dhaka,Bangladesh

BackgroundCOVID-19 caused by SARS-CoV-2 ranges from asymptomatic to severe disease and can cause fatal and devastating outcome in many cases. In this study, we have compared the clinical, biochemical and immunological parameters across the different disease spectrum of COVID-19 in Bangladeshi patients.Methodology/Principal findingsThis longitudinal study was conducted in two COVID-19 hospitals and also around the community in Dhaka city in Bangladesh between November 2020 to March 2021. A total of 100 patients with COVID-19 infection were enrolled and classified into asymptomatic, mild, moderate and severe cases (n = 25/group). In addition, thirty age and sex matched healthy participants were enrolled and 21 were analyzed as controls based on exclusion criteria. After enrollment (study day1), follow-up visits were conducted on day 7, 14 and 28 for the cases.Older age, male gender and co-morbid conditions were the risk factors for severe COVID-19 disease. Those with moderate and severe cases of infection had low lymphocyte counts, high neutrophil counts along with a higher neutrophil-lymphocyte ratio (NLR) at enrollment; this decreased to normal range within 42 days after the onset of symptom. At enrollment, D-dimer, CRP and ferritin levels were elevated among moderate and severe cases. The mild, moderate, and severe cases were seropositive for IgG antibody by day 14 after enrollment. Moderate and severe cases showed significantly higher IgM and IgG levels of antibodies to SARS-CoV-2 compared to mild and asymptomatic cases.Conclusion/SignificanceWe report on the clinical, biochemical, and hematological parameters associated with the different severity of COVID-19 infection. We also show different profile of antibody response against SARS-CoV-2 in relation to disease severity, especially in those with moderate and severe disease manifestations compared to the mild and asymptomatic infection.     

Human 14-3-3 Proteins Site-selectively Bind the Mutational Hotspot Region of SARS-CoV-2 Nucleoprotein Modulating its Phosphoregulation

Phosphorylation of SARS-CoV-2 nucleoprotein recruits human cytosolic 14-3-3 proteins playing a well-recognized role in replication of many viruses. Here we use genetic code expansion to demonstrate that 14-3-3 binding is triggered by phosphorylation of SARS-CoV-2 nucleoprotein at either of two pseudo-repeats centered at Ser197 and Thr205. According to fluorescence anisotropy measurements, the pT205-motif, present in SARS-CoV-2 but not in SARS-CoV, is preferred over the pS197-motif by all seven human 14-3-3 isoforms, which collectively display an unforeseen pT205/pS197 peptide binding selectivity hierarchy. Crystal structures demonstrate that pS197 and pT205 are mutually exclusive 14-3-3-binding sites, whereas SAXS and biochemical data obtained on the full protein-protein complex indicate that 14-3-3 binding occludes the Ser/Arg-rich region of the nucleoprotein, inhibiting its dephosphorylation. This Ser/Arg-rich region is highly prone to mutations, as exemplified by the Omicron and Delta variants, with our data suggesting that the strength of 14-3-3/nucleoprotein interaction can be linked with the replicative fitness of the virus.     

Comparison of naturally acquired antibody responses against the C-terminal processing products of Plasmodium vivax Merozoite Surface Protein-1 under low transmission and unstable malaria conditions in Sri Lanka

We report here, for the first time, a comparison of naturally acquired antibody responses to the 42 and 19 kDa C-terminal processing products of Plasmodium vivax Merozoite Surface Protein-1 assayed by ELISA using p42 and p19 baculovirus-derived recombinant proteins, respectively. Test populations comprised patients with microscopy confirmed acute P. vivax infections from two regions endemic for vivax malaria where low transmission and unstable malaria conditions prevail, and a non-endemic urban area, in Sri Lanka. The antibody prevalence to the two proteins, both at the individual and population levels, tend to respond more to p42 than to p19 in all test areas, where >14% of individuals preferentially recognized p42, compared with <2% for p19. In patients with no previous exposure to malaria, 21% preferentially recognized p42, whereas none exclusively recognized p19. A significantly lower prevalence of anti-p19 IgM, but not anti-p42 IgM, was observed among residents from endemic areas compared with their non-endemic counterparts. Individuals from both endemic areas produced significantly less anti-p19 IgM compared with anti-p42 IgM. IgG1 was the predominant IgG isotype for both antigens in all individuals. With increasing exposure to malaria in both endemic areas, anti-p19 antibody responses were dominated by the functionally important IgG1 and IgG3 isotypes, with a concurrent reduction in IgM that was lacking in the non-endemic residents. This antibody switch was also reflected for PvAMA-1 as we previously reported with the identical battery of sera. In contrast, the antibody switch for p42 was restricted to endemic residents with more extensive exposure. These results suggest that an IgM-dominated antibody response against the p42 polymorphic region in endemic residents may interfere with the development of an IgG-dominated "protective" isotype shift to p19, that may complicate vaccine development.     

Genetic variations of NOD2 and MD2 genes in hepatitis B virus infection

Objectives: Nucleotide oligomerization domain 2 (NOD2) and myeloid differentiation protein 2 (MD-2) have crucial roles in the innate immune system. NOD2 is a member of the NOD-like receptor (NLR) family of pattern recognition receptors (PRRs), while MD-2 is a co-receptor for Toll-like receptor 4 (TLR4), which comprises another group of PRRs. Genetic variations in the NOD2 and MD-2 genes may be susceptibility factors to viral pathogens including hepatitis B virus (HBV). We investigated whether polymorphisms at NOD2 (rs2066845 and rs2066844) or at MD-2 (rs6472812 and rs11466004) were associated with susceptibility to HBV infection and advancement to related liver complications in a Saudi Arabian population. Methods: A total of 786 HBV-infected patients and 600 healthy uninfected controls were analyzed in the present study. HBV-infected patients were categorized into three groups based on the clinical stage of the infection: inactive HBV carriers, active HBV carriers, and patients with liver cirrhosis + hepatocellular carcinoma (HCC). Results: All four SNPs were significantly associated with susceptibility to HBV infection although none of the SNPs tested in NOD2 and MD-2 were significantly associated with persistence of HBV infection. We found that HBV-infected patients that were homozygous CC for rs2066845 in the NOD2 gene were at a significantly increased risk of progression to HBV-related liver complications (Odds Ratio = 7.443 and P = 0.044). Furthermore, haplotype analysis found that the rs2066844-rs2066845 C-G and T-G haplotypes at the NOD2 gene and four rs6472812-rs11466004 haplotypes (G-C, G-T, A-C, and A-T) at the MD-2 gene were significantly associated with HBV infection in the affected cohort compared to those found in our control group. Conclusion: We found that the single nucleotide polymorphisms rs2066844 and rs2066845 at NOD2 and rs6472812 and rs11466004 at MD-2 were associated with susceptibility to HBV infection in a Saudi population.     

Immunogenicity,effectiveness and safety of COVID-19 vaccine in older adults living in nursing homes: A real-life study

IntroductionBNT162b2 (BioNTech and Pfizer) is a nucleoside-modified mRNA vaccine that provides protection against SARS-CoV-2 infection and is generally well tolerated. However, data about its efficacy, immunogenicity and safety in people of old age or with underlying chronic conditions are scarce.PurposeTo describe BNT162b2 (BioNTech and Pfizer) COVID-19 vaccine immunogenicity, effectiveness and reactogenicity after complete vaccination (two doses), and immunogenicity and reactogenicity after one booster, in elders residing in nursing homes (NH) and healthy NH workers in real-life conditions.MethodsObservational, ambispective, multicenter study. Older adults and health workers were recruited from three nursing homes of a private hospital corporation located in three Spanish cities. The primary vaccination was carried out between January and March 2021. The follow-up was 13 months. Humoral immunity, adverse events, SARS-CoV-2 infections, hospitalizations and deaths were evaluated. Cellular immunity was assessed in a participant subset.ResultsA total of 181 residents (mean age 84.1 years; 89.9% females, Charlson index ≥2: 45%) and 148 members of staff (mean age 45.2 years; 70.2% females) were surveyed (n:329). After primary vaccination of 327 participants, vaccine response in both groups was similar; ≈70% of participants, regardless of the group, had an antibody titer above the cut-off considered currently protective (260 BAU/ml). This proportion increased significantly to ≈ 98% after the booster (p < 0.0001 in both groups). Immunogenicity was largely determined by a prior history of COVID-19 infection. Twenty residents and 3 workers were tested for cellular immunity. There was evidence of cellular immunity after primary vaccination and after booster. During the study, one resident was hospitalized for SARS-CoV-2. No SARS-CoV-2-related deaths were reported and most adverse events were mild.ConclusionsOur results suggest that the BNT162b2 mRNA COVID-19 vaccine is immunogenic, effective and safe in elderly NH residents with underlying chronic conditions.