A Multifunctional Neutralizing Antibody-Conjugated Nanoparticle Inhibits and Inactivates SARS-CoV-2.

The outbreak of 2019 coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in a global pandemic. Despite intensive research, the current treatment options show limited curative efficacies. Here the authors report a strategy incorporating neutralizing antibodies conjugated to the surface of a photothermal nanoparticle (NP) to capture and inactivate SARS-CoV-2. The NP is comprised of a semiconducting polymer core and a biocompatible polyethylene glycol surface decorated with high-affinity neutralizing antibodies. The multifunctional NP efficiently captures SARS-CoV-2 pseudovirions and completely blocks viral infection to host cells in vitro through the surface neutralizing antibodies. In addition to virus capture and blocking function, the NP also possesses photothermal function to generate heat following irradiation for inactivation of virus. Importantly, the NPs described herein significantly outperform neutralizing antibodies at treating authentic SARS-CoV-2 infection in vivo. This multifunctional NP provides a flexible platform that can be readily adapted to other SARS-CoV-2 antibodies and extended to novel therapeutic proteins, thus it is expected to provide a broad range of protection against original SARS-CoV-2 and its variants.

ATP stabilised and sensitised calcium phosphate nanoparticles as effective adjuvants for a DNA vaccine against cancer.

Cancer vaccines based on DNA encoding oncogenes have shown great potential in preclinical studies. However, the efficacy of DNA vaccines is limited by their weak immunogenicity because of low cellular internalisation and insufficient activation of dendritic cells (DCs). Calcium phosphate (CP) nanoparticles (NPs) are biodegradable vehicles with low toxicity and high loading capacity of DNA but suffer from stability issues. Here we employed adenosine triphosphate (ATP) as a dual functional agent, i.e. stabiliser for CP and immunological adjuvant, and applied the ATP-modified CP (ACP) NPs to the DNA vaccine. ACP NP-enhanced cellular uptake and improved transfection efficiency of DNA vaccine, and further showed the ability to activate DCs that are critical for them to prime T cells in cancer immunotherapy. As a result, a higher level of antigen-specific antibody with stronger tumour growth inhibition was achieved in mice immunised with the ACP-DNA vaccine. Overall, this one-step synthesised ACP NPs are an efficient nano-delivery system and nano-adjuvant for cancer DNA vaccines.

Cross-Reactivity and Sequence Homology Between Alpha-Synuclein and Food Products: A Step Further for Parkinson's Disease Synucleinopathy.

INTRODUCTION: Parkinson's disease is characterized by non-motor/motor dysfunction midbrain neuronal death and α-synuclein deposits. The accepted hypothesis is that unknown environmental factors induce α-synuclein accumulation in the brain via the enteric nervous system. MATERIAL AND METHODS: Monoclonal antibodies made against recombinant α-synuclein protein or α-synuclein epitope 118-123 were applied to the antigens of 180 frequently consumed food products. The specificity of those antibody-antigen reactions was confirmed by serial dilution and inhibition studies. The Basic Local Alignment Search Tool sequence matching program was used for sequence homologies. RESULTS: While the antibody made against recombinant α-synuclein reacted significantly with 86/180 specific food antigens, the antibody made against α-synuclein epitope 118-123 reacted with only 32/180 tested food antigens. The food proteins with the greatest number of peptides that matched with α-synuclein were yeast, soybean, latex hevein, wheat germ agglutinin, potato, peanut, bean agglutinin, pea lectin, shrimp, bromelain, and lentil lectin. Conclusions: The cross-reactivity and sequence homology between α-synuclein and frequently consumed foods, reinforces the autoimmune aspect of Parkinson's disease. It is hypothesized that luminal food peptides that share cross-reactive epitopes with human α-synuclein and have molecular similarity with brain antigens are involved in the synucleinopathy. The findings deserve further confirmation by extensive research.

Preparation of the peroxisome proliferator-activated receptor α polyclonal antibody: Its application in fatty liver hemorrhagic syndrome.

Peroxisome proliferator-activated receptor α (PPARα) play a key role in the regulation of metabolic homeostasis, inflammation, cellular growth, and differentiation. To further explore the potential role of PPARα in the energy homeostasis of fatty liver hemorrhagic syndrome (FLHS), we reported the prokaryotic expression and purification of chicken PPARα subunit protein, and successfully prepared a polyclonal antibody against PPARα recombinant protein. The 987 bp PPARα subunit genes were cloned into the pEASY-T3 clone vector. Then the plasmid PCR products encoding 329 amino acids were ligated to pEASY-Blunt E2 vector and transformed into BL21 to induce expression. The recombinant PPARα subunit protein, containing His-tag, was purified by affinity column chromatography using Ni-NTA affinity column. Rabbit antiserum was generated by using the concentration of recombinant PPARα subunit protein as the antigen. The results of western blotting showed that the antiserum can specifically recognize chicken endogenous PPARα protein. Immunohistochemistry and immunofluorescence showed that the PPARα mainly existed in the nucleus of hepatocytes, renal epithelial cells and hypothalamic endocrine nerve cells. More importantly, western blotting and real-time quantitative PCR indicated that FLHS significantly decreased the expression of PPARα.

Effects of heat treatment on the antigenicity, antigen epitopes, and structural properties of ß-conglycinin.

In this study, the effects of heat treatment on antigenicity, antigen epitopes, and structural changes in ß-conglycinin were investigated. Results showed that the IgG (Immunoglobulin G) binding capacity of heated protein was inhibited with increased temperature, although IgE (Immunoglobulin E) binding capacity increased. Linear antigen epitopes generally remained intact during heat treatment. After heat treatment, ß-conglycinin was more easily hydrolyzed by digestive enzymes, and a large number of linear epitopes was destroyed. In addition, heat denaturation of ß-conglycinin led to the formation of protein aggregates and reduction of disulfide bonds. The contents of random coils and ß-sheet of heated ß-conglycinin decreased, but the contents of ß-turn and α-helix increased. Moreover, the protein structure of heated ß-conglycinin unfolded, more hydrophobic regions were exposed, and the tertiary structure of ß-conglycinin was destroyed. Heat treatment affected the antigenicity and potential sensitization of ß-conglycinin by changing its structure.

ANTIGENIC STIMULATION DURING PREGNANCY MODIFIES SPECIFIC IGA1 AND IGA2 SUBCLASSES IN HUMAN COLOSTRUM ACCORDING TO THE CHEMICAL COMPOSITION OF THE ANTIGEN.

BACKGROUND: Several studies have evaluated the effect of infectious diseases and vaccine protocols during pregnancy on maternal milk immunoglobulin (Ig) levels, to understand the protection conferred by lactation on newborns. Colostrum is the primary source of maternal IgA for the newborn. IgA participates in protection mechanisms in the neonate's mucosa. In humans, IgA has two subclasses with differential anatomical distribution among mucosal compartments. Total IgA levels in maternal milk vary after antigen stimulation and have differential affinities in function of the chemical composition of the antigens. We studied the effect of antigenic stimulation during pregnancy on the concentrations of specific IgA1 and IgA2 subclasses in human colostrum. METHODS: We analyzed data from 113 women in Mexico City and compared the amount of IgA subclasses in colostrum against three antigens: two from vaccine protocols (tetanus toxoid and pneumococcal polysaccharides) and lipopolysaccharide, a ubiquitous antigen in the gastrointestinal tract. RESULTS: In agreement with the previous reports, we showed that IgA1 from colostrum mainly recognized protein antigens; in sharp contrast, IgA2 was mostly directed against polysaccharide antigens. These levels increased in women who had previous contacts through vaccination or infections during pregnancy. CONCLUSIONS: Antigen interaction during pregnancy increased the amount of specific IgA subclasses, depending on the chemical composition of the antigen.

Antigenic stimulation during pregnancy modifies specific iga1 and iga2 subclasses in human colostrum according to the chemical composition of the antigen

ABSTRACT Background: Several studies have evaluated the effect of infectious diseases and vaccine protocols during pregnancy on maternal milk immunoglobulin (Ig) levels, to understand the protection conferred by lactation on newborns. Colostrum is the primary source of maternal IgA for the newborn. IgA participates in protection mechanisms in the neonate's mucosa. In humans, IgA has two subclasses with differential anatomical distribution among mucosal compartments. Total IgA levels in maternal milk vary after antigen stimulation and have differential affinities in function of the chemical composition of the antigens. We studied the effect of antigenic stimulation during pregnancy on the concentrations of specific IgA1 and IgA2 subclasses in human colostrum. Methods: We analyzed data from 113 women in Mexico City and compared the amount of IgA subclasses in colostrum against three antigens: two from vaccine protocols (tetanus toxoid and pneumococcal polysaccharides) and lipopolysaccharide, a ubiquitous antigen in the gastrointestinal tract. Results: In agreement with the previous reports, we showed that IgA1 from colostrum mainly recognized protein antigens; in sharp contrast, IgA2 was mostly directed against polysaccharide antigens. These levels increased in women who had previous contacts through vaccination or infections during pregnancy. Conclusions: Antigen interaction during pregnancy increased the amount of specific IgA subclasses, depending on the chemical composition of the antigen.

Asymmetric mesoporous silica nanoparticles as potent and safe immunoadjuvants provoke high immune responses.

Asymmetric mesoporous silica nanoparticles with a head-tail structure are potent immunoadjuvants for delivering a peptide antigen, generating a higher antibody immune response in mice compared to their symmetric counterparts.

Simultaneous determination of glycyrrhizin and liquiritin in licorice roots and Kampo medicines by combination enzyme-linked immunosorbent assay using anti-glycyrrhizin and anti-liquiritin monoclonal antibodies.

Immunoassay systems using monoclonal antibodies (mAbs) are one of the most useful techniques in the analytical, biochemical, and clinical fields. In this study, a combination enzyme-linked immunosorbent assay (ELISA) using both anti-glycyrrhizin and anti-liquiritin mAbs (anti-GL/Liq mixture mAbs) was developed for quality control of licorice and its products. The combination ELISA demonstrated high sensitivity, reproducibility, and specificity for the total content of GL and Liq by a single assay. The developed ELISA was effective and useful as the first screening method in the selection of high-quality licorice from the Glycyrrhiza species and in confirming the quality of licorice-containing Kampo medicines.

Structural studies of novel glycoconjugates from polymerized allergens (allergoids) and mannans as allergy vaccines.

Immunotherapy for treating IgE-mediated allergies requires high doses of the corresponding allergen. This may result in undesired side effects and, to avoid them, hypoallergenic allergens (allergoids) polymerized with glutaraldehyde are commonly used. Targeting allergoids to dendritic cells to enhance cell uptake may result in a more effective immunotherapy. Allergoids coupled to yeast mannan, as source of polymannoses, would be suitable for this purpose, since mannose-binding receptors are expressed on these cells. Conventional conjugation procedures of mannan to proteins use oxidized mannan to release reactive aldehydes able to bind to free amino groups in the protein; yet, allergoids lack these latter because their previous treatment with glutaraldehyde. The aim of this study was to obtain allergoids conjugated to mannan by an alternative approach based on just glutaraldehyde treatment, taking advantage of the mannoprotein bound to the polymannose backbone. Allergoid-mannan glycoconjugates were produced in a single step by treating with glutaraldehyde a defined mixture of allergens derived from Phleum pratense grass pollen and native mannan (non-oxidized) from Saccharomyces cerevisae. Analytical and structural studies, including 2D-DOSY and (1)H-(13)C HSQC nuclear magnetic resonance spectra, demonstrated the feasibility of such an approach. The glycoconjugates obtained were polymers of high molecular weight showing a higher stability than the native allergen or the conventional allergoid without mannan. The allergoid-mannan glycoconjugates were hypoallergenic as detected by the IgE reactivity with sera from grass allergic patients, even with lower reactivity than conventional allergoid without mannan. Thus, stable hypoallergenic allergoids conjugated to mannan suitable for using in immunotherapy can be achieved using glutaraldehyde. In contrast to mannan oxidation, the glutaraldehyde approach allows to preserve mannoses with their native geometry, which may be functionally important for its receptor-mediated recognition.

Polysialic acid as an antigen for monoclonal antibody HIgM12 to treat multiple sclerosis and other neurodegenerative disorders.

CNS regeneration is a desirable goal for diseases of brain and spinal cord. Current therapeutic strategies for the treatment of multiple sclerosis (MS) aim to eliminate detrimental effects of the immune system, so far without reversing disability or affecting long-term prognosis in patients. Approachable molecular targets that stimulate CNS repair are not part of the clinical praxis or have not been identified yet. The purpose of this study was to identify the molecular target of the human monoclonal antibody HIgM12. HIgM12 reverses motor deficits in chronically demyelinated mice, a model of MS. Here, we identified polysialic acid (PSA) attached to the neural cell adhesion molecule (NCAM) as the antigen for HIgM12 by using different NCAM knockout strains and through PSA removal from the NCAM protein core. Antibody binding to CNS tissue and primary cells, antibody-mediated cell adhesion, and neurite outgrowth on HIgM12-coated nitrocellulose was detected only in the presence of PSA as assessed by western blotting, immunoprecipitation, immunocytochemistry, and histochemistry. We conclude that HIgM12 mediates its in vivo and in vitro effects through binding to PSA and has the potential to be an effective therapy for MS and neurodegenerative diseases. The human antibody HIgM12 stimulates neurite outgrowth in vitro and promotes function in chronically demyelinated mice, a model of multiple sclerosis. The cellular antigen for HIgM12 was undetermined. Here, we identified polysialic acid attached to NCAM (neural cell adhesion molecule) as the cellular target for HIgM12. This includes glial fibrillary acidic protein (GFAP)-positive mouse astrocytes (GFAP, red; HIgM12, green; DAPI, blue) among other cell types of the central nervous system. These findings indicate a new strategy for the treatment of neuro-motor disorders including multiple sclerosis.

Introducing a new method for evaluation of the interaction between an antigen and an antibody: single frequency impedance analysis for biosensing systems.

This paper illustrates the application of an antibody, anti-parathyroid hormone (anti-PTH), as a bioreceptor in a biosensor system for the first time, and demonstrates how this biosensor can be used in parathyroid hormone (PTH) determination. The interaction between the biosensor and parathyroid hormone was firstly investigated by a novel electrochemical method, single frequency impedance analysis. The biosensor was based on the gold electrode modified by cysteine self-assembled monolayers. Anti-PTH was covalently immobilized onto cysteine layer by using an EDC/NHS couple. The immobilization of anti-PTH was monitored by cyclic voltammetry and electrochemical impedance spectroscopy techniques. The performance of the biosensor was evaluated in terms of linearity, sensitivity, repeatability and reproducibility, after a few important optimization studies were carried out. In particular, parathyroid hormone was detected within a linear range of 10-60 fg/mL. Kramers-Kronig transform was also performed on the impedance data. The specificity of the biosensor was also evaluated. The biosensor was validated by using a complementary reference technique. Lastly the developed biosensor was used to monitor PTH levels in artificial serum samples.

An intravenous exposure mouse model for prediction of potential drug-sensitization using reporter antigens popliteal lymph node assay.

Immune-mediated drug hypersensitivity is a particularly concerning health-safety issue among clinicians given its unpredictability and potentially life-threatening effects, especially with exposure to intravenous drugs. Therefore, the development of intravenous drug-exposure models for drug-hazard assessments has garnered increasing interest in recent years. In this study, we used reporter antigens popliteal lymph node assay to investigate the potential value of intravenous exposure to a selected variety of allergenic compounds, including ovalbumin (OVA), concanavalin A (ConA) and diclofenac. The trinitrophenyl (TNP)-specific antibody-forming cells were used to assess the systemic immune responses to a bystander antigen. Mice were subsequently sensitized by TNP-OVA, and then intravenous exposure to one of the selective compounds. As expected, all positive compounds induced significant popliteal lymph node (PLN) proliferation compared with the control. OVA significantly increased Cluster of Differentiation 4 receptors (CD4)⁺ interleukin-4 (IL-4)⁺ T-helper 2 (Th2) cells and, consequently, increased the ratios of IL-4/interferon-γ (IFN-γ) antibody-forming cells (AFCs) in PLNs, while bringing about a dose-dependent increase in immunoglobulin G1 (IgG1) AFCs; these findings indicate that a Th2 hypersensitivity response was induced. A Th2 response was also observed in diclofenac sodium-treated groups, and for ConA, a more mixed Th1/Th2 immune response appeared to be induced. In addition, there was no marked reaction with the negative compound. Together, it seems likely that the intravenous exposure model may be useful for drug-induced systemic hypersensitivity assessments.

Development and characterization of immuno-nanocarriers targeting the cancer stem cell marker AC133.

In the context of targeted therapy, we addressed the possibility of developing a drug delivery nanocarrier capable to specifically reach cancer cells that express the most prominent marker associated with cancer stem cell (CSC) phenotype, AC133. For this purpose, 100nm lipid nanocapsules (LNCs) were functionalized with a monoclonal antibody (mAb) directed against AC133 according to two distinct methods: firstly, post-insertion within 100nm LNCs of a lipid poly(ethylene glycol) functionalized with reactive-sulfhydryl maleimide groups (DSPE-PEG(2000)-maleimide) followed by thiolated mAb coupling, and, secondly, creation of a thiolated lipo-immunoglobulin between DSPE-PEG(2000)-maleimide and AC133, then post-inserted within LNCs. Due to the reduced number of purification steps, lower amounts of DSPE-PEG(2000)-maleimide that were necessary as well as lower number of free maleimide functions present onto the surface of immuno-LNC, the second method was found to be more appropriate. Thus, 126nm AC133-LNC with a zeta potential of -22mV while keeping a narrow distribution were developed. Use of the IgG1κ isotype control-immunoglobulins produced similar control IgG1-LNCs. Micro-Bradford colorimetric assay indicated a fixation of about 40 immunoglobulins per LNC. Use of human Caco-2 cells that constitutively express AC133 (Caco-2-AC133(high)) allowed addressing the behavior of the newly functionalized immuno-LNCs. siRNA knockown strategy permitted to obtain Caco-2-AC133(low) for comparison. Immunofluorescence-combined flow cytometry analysis demonstrated that the epitope-recognition function of AC133 antibody was preserved when present on immuno-LNCs. Although grafting of immunoglobulins onto the surface of LNCs repressed their internalization within Caco-2 cells as evaluated by flow cytometry, AC133-specific cellular binding was obtained with AC133-LNC as assessed by computer-assisted fluorescence microscopy. In conclusion, interest of AC133-LNCs as niche carriers is discussed toward the development of CSC targeted chemo- or radio-nanomedicines.

Pollen and plant food profilin allergens show equivalent IgE reactivity.

BACKGROUND: Profilins are commonly involved in polysensitization of allergic patients; therefore, appropriate markers should be used in component-resolved diagnosis. OBJECTIVE: To evaluate the immunological equivalence between profilins from pollens and plant-derived foods, to be used in component-resolved diagnosis. METHODS: Specific immunoglobulin (Ig) G antibodies against pollen and fruit profilins, as well as sera from patients allergic to mustard, melon, or olive pollen, were used. Purified profilins from mustard seeds, fruit melon, and chenopod and birch pollen were assayed in immunoblotting, enzyme-linked immunosorbent assay (ELISA), and ELISA inhibition assays. RESULTS: Significant correlation was found in the response of purified profilins by ELISA and immunoblotting for both specific IgG and IgE. The highest levels of IgE binding were obtained for olive pollen-allergic patients, which could be related to the route of sensitization. The responses of individual patients to profilins were also similar and independent of the sensitizing source. The inhibition between pairs of allergens was generally higher than 70%, indicating that profilins share most of the IgE epitopes. Modeling of mimotopes in the conformational structure of the implicated profilins supports their strong cross-reactivity obtained experimentally. CONCLUSIONS: No correlation exists between the level of IgE response of individual patients to specific profilins and the corresponding theoretical sensitizing source, suggesting that the sensitization could be attributable to any profilin present in the environment of the patients. This would bear out the use of most profilins as a common marker for polysensitization in component-resolved diagnosis and for therapeutic approaches.

Can immunoglobulin E-measurement replace challenge tests in allergic rhinoconjunctivits to grass pollen?

BACKGROUND: There is minimal data available concerning the dose-response relationship between allergen exposure and clinical reactivity for outdoor aeroallergens, such as timothy grass pollen. Timothy pollen-specific IgE (sIgE) determinations might assist in predicting the clinical reactivity in patients with allergic rhinoconjunctivitis (ARC). METHODS: Allergen-sIgE antibody levels of timothy grass pollen were correlated with individual threshold doses eliciting allergic reactions in skin prick test (SPT), conjunctival (CPT) and nasal (NPT) provocation tests in patients suffering from pollen-induced rhinoconjunctivitis and healthy controls. RESULTS: One hundred and four patients with ARC (median age: 27 years; range: 18-64; females: 58%) and 36 controls (25 years (22-77); females: 70%) were included in the study. Ninety-six percent of the patients showed a positive reaction in the nasal and 57% showed a positive reaction in the conjunctival provocation. With regarding to titrated SPT, 98% of the patients showed a positive skin test reaction; correlating with the level of sIgE for timothy (P < 0.001). For both provocation protocols, there was no correlation between the provocation concentration at the reaction and the level of sIgE for timothy. The ratio of sIgE/total IgE correlated with the dilution level of SPT (P < 0.002) and CPT (P < 0.01), respectively. CONCLUSION AND CLINICAL RELEVANCE: A dose-response relationship between the levels of sIgE and clinical outcome of timothy allergen exposure could not be established. Although IgE-determination remains an important key element in allergy diagnosis, provocation tests are procedures of choice if the clinical relevance of an allergen has to be confirmed.

Identification of a new allergen from Amaranthus retroflexus pollen, Ama r 2.

BACKGROUND: Pollinosis from Amaranthus retroflexus pollen is a common cause of respiratory allergy in Iran with a high positive rate (68.8%) among Iranian allergic patients. The aim of the present study was to evaluate the allergenicity of the A. retroflexus pollen profilin. METHODS: Using sera from twelve patients allergic to A. retroflexus pollen, IgE-binding proteins from the A. retroflexus pollen extract was identified by immunoblotting. The cDNA of A. retroflexus pollen profilin was amplified, then cloned into the pET-21b (+) vector, expressed in Escherichia coli, and finally purified by metal affinity chromatography. The IgE-binding capacity of the recombinant protein was then analyzed by the ELISA, immunoblotting, and inhibition assays, as well as by the skin prick test (SPT). RESULTS: Immunoblotting results indicated a 14.6kDa protein with IgE-reactivity to 33% (4/12) among A. retroflexus pollen-allergic patients. Nucleotide sequencing of the cDNA revealed an open reading frame of 399 bp encoding for 133 amino acid residues which was belonged to the profilin family and designated as Ama r 2. A recombinant Ama r 2 (rAma r 2) was then produced in E. coli as a soluble protein which showed a strong IgE-reactivity via ELISA confirmed by the SPT. Inhibition experiments revealed high IgE cross-reactivities with the profilins from other plants. CONCLUSIONS: The profilin from the A. retroflexus pollen, Ama r 2, was firstly identified as an allergen. Moreover, rAma r 2 was produced in E. coli as a soluble immunoreactive protein with an IgE-reactivity similar to that of its natural counterpart.

Isolation of 5-(hydroxymethyl)furfural from Lycium chinense and its inhibitory effect on the chemical mediator release by basophilic cells.

The effect of hot water extracts of LYCIUM CHINENSE fruits (LCF) on the ß-hexosaminidase (ß-hexo) release by IgE sensitized BSA stimulated rat basophilic leukemia (RBL-2H3) cells was investigated. The ethylacetate (EtOAc) layer of the extract has shown an inhibitory effect on ß-hexo release from RBL-2H3 cells at the antigen antibody binding stage. The water (H2O) fraction (EFW) of the chloroform (CHCl3) extract from the EtOAc layer also inhibited ß-hexo release at the same stage in a dose-dependent manner. With column chromatography preparation, proton and carbon nuclear magnetic resonance (¹H and ¹³C NMR) spectra, electron ionization mass spectrometer (EI-MS) spectra, and high-performance liquid chromatography (HPLC) analysis, the active component was determined to be 5-(hydroxymethyl)furfural (5-HMF). Thus, the 5-HMF showed an inhibitory effect on ß-hexo release at the antigen-antibody binding stage and the antibody-receptor binding stage. Furthermore, 5-HMF suppressed [Ca²+] I influx in the IgE-sensitized BSA-stimulated RBL-2H3 cells. Our results show that 5-HMF may be useful for the treatment or prevention of type I allergic diseases.

Frequency domain detection of biomolecules using silicon nanowire biosensors.

We demonstrate a new protein detection methodology based upon frequency domain electrical measurement using silicon nanowire field-effect transistor (SiNW FET) biosensors. The power spectral density of voltage from a current-biased SiNW FET shows 1/f-dependence in frequency domain for measurements of antibody functionalized SiNW devices in buffer solution or in the presence of protein not specific to the antibody receptor. In the presence of protein (antigen) recognized specifically by the antibody-functionalized SiNW FET, the frequency spectrum exhibits a Lorentzian shape with a characteristic frequency of several kilohertz. Frequency and conventional time domain measurements carried out with the same device as a function of antigen concentration show more than 10-fold increase in detection sensitivity in the frequency domain data. These concentration-dependent results together with studies of antibody receptor density effect further address possible origins of the Lorentzian frequency spectrum. Our results show that frequency domain measurements can be used as a complementary approach to conventional time domain measurements for ultrasensitive electrical detection of proteins and other biomolecules using nanoscale FETs.