Spot Assay Research Articles

Real-Time Void Spot Assay.

Normal voiding behavior is the result of the coordinated function of the bladder, the urethra, and the urethral sphincters under the proper control of the nervous system. To study voluntary voiding behavior in mouse models, researchers have developed the void spot assay (VSA), a method that measures the number and area of urine spots deposited on a filter paper lining the floor of an animal's cage. Although technically simple and inexpensive, this assay has limitations when used as an end-point assay, including a lack of temporal resolution of voiding events and difficulties quantifying overlapping urine spots. To overcome these limitations, we developed a video-monitored VSA, which we call real-time VSA (RT-VSA), and which allows us to determine voiding frequency, assess voided volume and voiding patterns, and make measurements over 6 h time windows during both the dark and light phases of the day. The method described in this report can be applied to a wide variety of mouse-based studies that explore the physiological and neurobehavioral aspects of voluntary micturition in health and disease states.

Antimicrobial Activities and Biopreservation Potential of Lactic Acid Bacteria (LAB) from Raw Buffalo (Bubalus bubalis) Milk.

The aim of this study was to investigate the antimicrobial and biopreservation potential of lactic acid bacteria. The potential probiotic culture inhibited the growth of gram-positive and gram-negative foodborne pathogens in agar spot assay with inhibition zones ranging from 10 to 21 mm in diameter. The strains showed coaggregation capabilities ranging from 7 to 71% with tested food pathogens including Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella enterica subsp. enterica serovar Typhimurium. The effect of cell-free supernatants on the release of 260 nm absorbing material, especially nucleic acids, was evaluated and indicated the antagonistic activity on foodborne pathogens, the highest being Lactobacillus paraplantarum against E. coli (3.77) and S. aureus (3.86) after 60 min. The effect of cell-free supernatant (CFS) on the growth of pathogens showed that Lactobacillus paraplantarum 11 and L. pentosus 93 had the highest inhibitory activity against tested strains. The biopreservation assay indicated that the potential probiotic strains Lactobacillus paraplantarum 11 (BT), Lactiplantibacillus plantarum 19, Lactobacillus pentosus 42, Limosilactobacillus fermentum 60, Lactobacillus pentosus 93, and Limosilactobacillus reuteri 112 were effective in reducing the Listeria monocytogenes population in raw buffalo milk. Complete Listeria monocytogenes inhibition was observed after 6-8 days. This study showed that probiotic LAB from buffalo milk have antimicrobial and biopreservation potential; these strains have the potential to be utilized as biopreservative agents in food products.

Development and Evaluation of Bacteriophage Cocktail to Eradicate Biofilms Formed by an Extensively Drug-Resistant (XDR) Pseudomonas aeruginosa.

Extensive and multiple drug resistance in P. aeruginosa combined with the formation of biofilms is responsible for its high persistence in nosocomial infections. A sequential method to devise a suitable phage cocktail with a broad host range and high lytic efficiency against a biofilm forming XDR P. aeruginosa strain is presented here. Out of a total thirteen phages isolated against P. aeruginosa, five were selected on the basis of their high lytic spectra assessed using spot assay and productivity by efficiency of plating assay. Phages, after selection, were tested individually and in combinations of two-, three-, four-, and five-phage cocktails using liquid infection model. Out of total 22 combinations tested, the cocktail comprising four phages viz. φPA170, φPA172, φPA177, and φPA180 significantly inhibited the bacterial growth in liquid infection model (p < 0.0001). The minimal inhibitory dose of each phage in a cocktail was effectively reduced to >10 times than the individual dose in the inhibition of XDR P. aeruginosa host. Field emission-scanning electron microscopy was used to visualize phage cocktail mediated eradication of 4-day-old multi-layers of XDR P. aeruginosa biofilms from urinary catheters and glass cover slips, and was confirmed by absence of any viable cells. Differential bacterial inhibition was observed with different phage combinations where multiple phages were found to enhance the cocktail's lytic range, but the addition of too many phages reduced the overall inhibition. This study elaborates an effective and sequential method for the preparation of a phage cocktail and evaluates its antimicrobial potential against biofilm forming XDR strains of P. aeruginosa.

P10 Phage-encoded lysins as promising antibacterials against uropathogenic Escherichia coli

Abstract Background Urinary tract infections (UTIs) represent a major public health issue. Uropathogenic Escherichia coli (UPEC) is a pathogen implicated in the vast majority of UTIs. Although treatable, the rampant and indiscriminate use of antibiotics has led to an alarming emergence of MDR strains. This can lead to complications, treatment failure, and increased rates of mortality and morbidity. Given the prevalence of these strains, we are exploring phage encoded-lysins as potential alternatives to antibiotics. Objectives Our study involved the development of an in silico strategy for the discovery and characterization of prophage-derived lysin sequences targeting the E. coli cell wall and evaluating the antibacterial activity of the recombinant lysins using in vitro assays. Methods Novel lysin sequences were searched by BLAST homology and by screening E. coli prophages in the database (using PHASTER). They were computationally characterized and their domain architecture was examined. Based on the desired physicochemical properties of the 16 lysins, 7 were selected for cloning, expression, and purification as recombinant proteins for the in vitro antibacterial activity. Results In silico analysis showed lysozyme-like domain in 9 out of 16 lysins and the predicted structure was either modular or globular. Cationic and hydrophobic residues at the C-terminal end and cationic residues in the catalytic domains indicate intrinsic bactericidal activity. Lysins (7) were cloned in pET28 vector and purified as His-tagged recombinant proteins by Ni-NTA chromatography. Using spot assay, 3 out of 7 lysins (9–12 μg) showed lysis of E. coli cells (BL21 DE3). The most promising was lysin sequence 5, which showed lysis of E. coli cells, both at stationary as well as mid-log phase cells. Turbidity reduction assay showed a 74.94% drop in OD600 in lysin (15 μM) treated cells after 3 h of incubation, at 37°C. Log killing assay showed 4 log10 reduction in the treated cells. Lysozyme assay demonstrates higher than / comparable lysozyme activity of lysin sequence 5 with the positive control. Conclusions Sixteen novel prophage-encoded lysin sequences have been identified to create a lysin bank (to screen against E. coli), and 7 of them have been purified. Screening shows three lysins having intrinsic bactericidal activity and hence did not require the addition of an Outer Membrane Permeabilizer (OMP). Lysin sequence 5 has exhibited the highest activity against E. coli cells. Enzyme stability and kinetics studies and screening of clinical isolates of E. coli from UTI patients is underway. Investigating this bank of lysins is aimed at the identification and development of a lead ‘enzybiotic’ with desired PK/PD characteristics against UTI-causing E. coli.

Nigeria healthcare worker SARS-CoV-2 serology study: Results from a prospective, longitudinal cohort.

Healthcare workers, both globally and in Nigeria, have an increased risk for SARS-CoV-2 infection compared with the general population due to higher risk contacts, including occupational exposures. In addition, primary healthcare workers represent an important group for estimating prior infection to SARS-CoV-2 because they work at the first point-of-contact for most patients yet have not been included in prior COVID-19 seroepidemiology research in Nigeria. We sought to evaluate baseline seroprevalence, rates of seroconversion (IgG- to IgG+) and seroreversion (IgG+ to IgG-), change in IgG concentration at 3- and 6-month follow-up, and factors associated with seropositivity. From June 2020 to December 2020, we conducted a longitudinal seroepidemiology study among frontline health care workers in Nigeria using a validated dried blood spot assay. Among 525 participants, mean (SD) age was 39.1 (9.7) years, 61.0% were female, and 45.1% were community health workers. The six-month follow-up rate was 93.5%. Seropositivity rates increased from 31% (95% CI: 27%, 35%) at baseline to 45% (95% CI: 40%, 49%) at 3-month follow-up, and 70% (95% CI: 66%, 74%) at 6-month follow-up. There was a corresponding increase in IgG levels from baseline (median = 0.18 ug/mL) to 3-month (median = 0.35 ug/mL) and 6-month follow-up (median = 0.59 ug/mL, Ptrend < .0001). A minority of participants reported symptoms from February 2020 until baseline (12.2%) or during 3-month (6.6%) or 6-month (7.5%) follow-up. only 1 participant was hospitalized. This study demonstrated high baseline, 3-month and 6-month follow-up prevalence of IgG antibodies to SARS-CoV-2 during the first two waves of the COVID-19 pandemic in Nigeria among a cohort of unvaccinated frontline healthcare workers, including primary healthcare workers despite low symptomatology. These results may have implications in state- and national-level disease pandemic modeling. Trial registration: NCT04158154.

Antimicrobial Activity of Ligilactobacillus animalis SWLA-1 and Its Cell-Free Supernatant against Multidrug-Resistant Bacteria and Its Potential Use as an Alternative to Antimicrobial Agents.

The emergence of multidrug-resistant (MDR) bacteria and the spread of antimicrobial resistance among various bacteria are major threats to the global community. Due to the increased failure of classical antibiotic treatments against MDR bacterial infections, probiotics and their antimicrobial compounds have been suggested as promising alternatives to deal with MDR bacteria. Various strains of lactic acid bacteria have been reported to produce antagonistic molecules against pathogens. A new strain of Ligilactobacillus animalis, L. animalis SWLA-1, isolated from the feces of healthy dogs, shows strong antimicrobial activity against not only common pathogens but also MDR bacteria. In this study, we compared the antimicrobial activity of L. animalis SWLA-1 with that of other lactobacilli and antibiotics using an agar spot assay. Additionally, a novel spot inhibition index was developed and validated to quantitively evaluate the inhibitory activities of lactobacilli and antibiotics. A competitive coculture assay of L. animalis SWLA-1 with MDR bacteria further demonstrated its antibacterial activity. Furthermore, we evaluated the antimicrobial activity of the cell-free supernatant (CFS) of L. animalis SWLA-1 and its stability under various conditions in vitro. We found that L. animalis SWLA-1 and its CFS are potential alternatives to classic antimicrobial agents.

Molecular identification and cross-immunogenic study on two field isolates of Mycoplasma synoviae isolated from broilers in five districts of Khyber Pakhtunkhwa.

Mycoplasma synoviae (MS) is an important poultry pathogen causing heavy economic losses Worldwide. Subclinical persistence of this pathogen is the major issue to control its prevalence. This study aimed to determine the molecular and cross-immunogenicity of MS among broilers in five Districts of Khyber Pakhtunkhwa (KP). This study was conducted by collecting 434 specimen samples from 40 broiler farms and desi poultry in five districts of KP. Specimen samples from the broiler birds (n = 150), broiler farm environment (n = 264), and desi poultry birds (n = 20) were aseptically collected and serially passaged in Modified Frey's broth. The homologous and heterologous antibody reactions were studied in rabbits. Before inoculation into rabbits, the MS isolates were inactivated by formalin and adjuvanted with Montanide. The overall turbidity prevalence in Frey's broth was observed as 109/434 (25.11%) samples, and these turbidity-positive samples were shifted on Frey's agar. After the appearance of classic fried egg colonies, the Biochemical confirmation was supported by the production of catalase and phosphatase, reduction of tetrazolium, film and spot assay, and fermentation of glucose for species differentiation in avian mycoplasma. The MS prevalence percentage was recorded as 2% (9/434) through biochemical tests. The PCR results showed 0.5% MS prevalence with two field isolates (named MS-1 and MS-2). Both MS-1 and MS-2 field isolates showed similar values (42.2) of homologous geometric mean titer (GMT). While the heterologous GMT for MS-1 serum against MS-2 isolate was lower (27.9) as compared to MS-2 serum against MS1 isolate (38.9). No titer was detected in the control group (Group-III). In conclusion, the results indicated the existence of MS in broiler birds and high homologous titers recorded between field isolates, which is a perpetual menace to poultry.

PS-BPB03-3: MODIFIED ANGIOTENSIN II PEPTIDE VACCINE FOR HYPERTENSION

We and others recently reported that an angiotensin II vaccine for hypertension successfully attenuated elevated blood pressures in an animal model without any immunogenic side effects. In this system, an immunogenic molecule (i.e., KLH) with adjuvants provides an antigen that supports the activation of helper T cells. We recently developed a novel peptide, AJP001, that possesses both a mouse T-cell epitope and adjuvant action. Direct conjugation to the antigen is useful for peptide vaccines without the addition of adjuvants. In this study, the efficacy of an angiotensin II and AJP001-conjugated peptide vaccine (AJP001- angiotensin II) was evaluated in mice. The anti-angiotensin II antibody titer was measured in Balb/C mice following three injections of AJP001-angiotensin II at 2-week intervals. SBP was measured during vaccination of Balb/C mice treated with angiotensin II infusion. AJ-angiotensin II treatment resulted in an increase in the anti-angiotensin II antibody titer in a dose-dependent manner without the addition of adjuvants. In the analysis of the humoral immune response, AJP001-angiotensin II mainly elicited IL-4 and IL-10 production, as measured by an enzyme-linked immune absorbent spot assay, which suggests the induction of a Th2 response. Importantly, cotreatment with purified antibodies attenuated angiotensin II-induced extracellular signal-regulated kinase phosphorylation in cultured vascular smooth muscle cells. The SBP in immunized mice was significantly lower than that in nonimmunized mice (135.9 ± 8.5 vs. 154.9 ± 16.8 mmHg, P = 0.02). Furthermore, angiotensin II-induced perivascular fibrosis in the heart was significantly attenuated in immunized mice, which also exhibited decreased mRNA expression of collagen I/III and transforming growth factor-beta. It may be a simple and useful therapeutic peptide vaccine, and we now further modify the T cell epitope for clinical trials.

Lipid-Based Poly(I:C) Adjuvants Strongly Enhance the Immunogenicity of SARS-CoV-2 Receptor-Binding Domain Vaccine

Abstract Background The outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has greatly threatened public health. Recent studies have revealed that the spike receptor-binding domain (RBD) of SARS-CoV-2 is a potent target for vaccine development. However, adjuvants are usually required to strengthen the immunogenicity of recombinant antigens. Different types of adjuvants can elicit different immune responses. Methods We developed an RBD recombinant protein vaccine with a polyriboinosinic acid–polyribocytidylic acid [poly(I:C)] adjuvant to evoke a strong immune response. The delivery of poly(I:C) was optimized in two steps. First, poly(I:C) was complexed with a cationic polymer, poly-l-lysine (PLL), to form poly(I:C)–PLL, a polyplex core. Thereafter, it was loaded into five different lipid shells (group II, III-1,2-distearoyl-sn-glycero-3-phosphocholine [DSPC], III-1,2-dioleoyl-sn-glycero-3-phosphoethanolamine [DOPE], IV-DOPE, and IV-DSPC). We performed an enzyme-linked immunosorbent assay and enzyme-linked immunosorbent spot assay to compare the ability of the five lipopolyplex adjuvants to enhance the immunogenicity of the SARS-CoV-2 RBD protein, including humoral and cellular immune responses. Finally, the adjuvant with the highest immunogenicity was selected to verify the protective immunity of the vaccine through animal challenge experiments. Results Recombinant RBD protein has low immunogenicity. The different adjuvants we developed enhanced the immunogenicity of the RBD protein in different ways. Among the lipopolyplexes, those containing DOPE (III-DOPE and IV-DOPE) elicited RBD-specific immunoglobulin G antibody responses, and adjuvants with four components elicited better RBD-specific immunoglobulin G antibody responses than those containing three components (P &lt; 0.05). The IC50 and IC90 titers indicated that the IV-DOPE lipopolyplex had the greatest neutralization ability, with IC50 titers of 1/117,490. Furthermore, in the challenge study, IV-DOPE lipopolyplex protected mice from SARS-CoV-2 infection. On the fourth day after infection, the average animal body weights were reduced by 18.56% (24.164 ± 0.665 g vs. 19.678 ± 0.455 g) and 0.06% (24.249 ± 0.683 g vs. 24.235 ± 0.681 g) in the MOCK and vaccine groups, respectively. In addition, the relative expression of viral RNA in the vaccinated group was significantly lower than that in the MOCK group (P &lt; 0.05). Interstitial inflammatory cell infiltration was observed in the MOCK group, whereas no obvious damage was observed in the vaccinated group. Conclusions The IV-DOPE–adjuvanted SARS-CoV-2 recombinant RBD protein vaccine efficiently protected mice from SARS-CoV-2 in the animal challenge study. Therefore, IV-DOPE is considered an exceptional adjuvant for SARS-CoV-2 recombinant RBD protein-based vaccines and has the potential to be further developed into a SARS-CoV-2 recombinant RBD protein-based vaccine.

The Antimicrobial Effect of Various Single-Strain and Multi-Strain Probiotics, Dietary Supplements or Other Beneficial Microbes against Common Clinical Wound Pathogens.

The skin is the largest organ in the human body and is colonized by a diverse microbiota that works in harmony to protect the skin. However, when skin damage occurs, the skin microbiota is also disrupted, and pathogens can invade the wound and cause infection. Probiotics or other beneficial microbes and their metabolites are one possible alternative treatment for combating skin pathogens via their antimicrobial effectiveness. The objective of our study was to evaluate the antimicrobial effect of seven multi-strain dietary supplements and eleven single-strain microbes that contain probiotics against 15 clinical wound pathogens using the agar spot assay, co-culturing assay, and agar well diffusion assay. We also conducted genera-specific and species-specific molecular methods to detect the DNA in the dietary supplements and single-strain beneficial microbes. We found that the multi-strain dietary supplements exhibited a statistically significant higher antagonistic effect against the challenge wound pathogens than the single-strain microbes and that lactobacilli-containing dietary supplements and single-strain microbes were significantly more efficient than the selected propionibacteria and bacilli. Differences in results between methods were also observed, possibly due to different mechanisms of action. Individual pathogens were susceptible to different dietary supplements or single-strain microbes. Perhaps an individual approach such as a 'probiogram' could be a possibility in the future as a method to find the most efficient targeted probiotic strains, cell-free supernatants, or neutralized cell-free supernatants that have the highest antagonistic effect against individual clinical wound pathogens.

1682. An Exciting New Approach: Isolation and characterisation of bacteriophages against MDR Acinetobacter baumannii

Abstract Background The modern advances in the fields of Medicine and Surgery depend entirely on our ability to treat and prevent infections. However, the rising incidence of antimicrobial resitance in both community and hospital settings has proved to be increasingly challenging. In 2017, WHO published a list of ‘priority pathogens’; antibiotic-resistant bacteria which posed the greatest threat to human health. Among them, A. baumannii was recognized as a critical priority pathogen due to its significant role in nosocomial infections. There was a growing call for new avenues in antimicrobial therapy. One such endeavour was to revisit an old therapeutic option against MDRO, viz. bacteriophage therapy. Numerous instances of successful phage therapy have already been published, with many more becoming available each day. Methods A total of fifty (50) multidrug resistant isolates of A. baumannii were collected. We attempted to isolate bacteriophages from hospital sewage water, against these collected strains, using standard procedure. Then the host range of the isolated phages were analysed against those 50 collected isolates. The lytic activity was confirmed using spot and plaque assays, following the techniques used by Newase et al, with some modifications. The isolated phages were then purified and stained following methods of Ellis et al, with some modifications, and visualised by a ThermoScientific Talos L120C transmission electron microscope (TEM). Graphical Workflow This depicts the workflow of the study. Created with BioRender.com Results A total of three (3) bacteriophages were isolated from the hospital sewage, and their lytic activity against A. baumannii strains were confirmed by the spot assay which showed clear zones on bacterial lawns. The phages, named vB_AbaS_SRNAIIMS002, vB_AbaS_SRNAIIMS008 and vB_AbaP_SRNAIIMS010, showed central clear zones surrounded by halos, in the plaque assay. Finally, all 3 bacteriophages were visualised by TEM, and two of them had morphology suggestive of siphoviridae family, with long tails, while the third had a short stubby tail, characteristic of the podoviridae family. Conclusion The study concludes that 3 novel bacteriophages were isolated from sewage water, all of which were active against MDR A. baumannii strains. This provides impetus to further research towards phage therapy as a novel therapeutic option against MDROs. Disclosures All Authors: No reported disclosures.

2158. Monitoring of Varicella specific T-cell mediated immunity in pediatric allogenic hematopoietic stem cell transplant recipients

Abstract Background Varicella-zoster virus (VZV) infection is known to occur in 13-55% of patients within the first year after hematopoietic stem cell transplant (HSCT). The dynamics of recovery of VZV-specific T cell- mediated immunity (CMI) and its role for prevention and control of VZV reactivation are rarely reported in pediatric allogenic HSCT recipients. Methods From April 2019 to February 2020, subjects aged younger than 19 years who underwent allogenic HSCT with at least 1 year of follow up at Asan Medical Center Children`s Hospital were prospectively enrolled. All of them underwent VZV-specific enzyme-linked immune absorbent spot (ELISPOT) assays just before HSCT and then at 1, 3 months following HSCT. Extension study, which measures VZV-specific CMI before and after VZV vaccination at 24 months post-HSCT, is currently underway. Results A total of 32 HSCT recipients with a median age of 11years were enrolled. 37.5% underwent haploidentical HSCT and VZV R+ were in 78.1%. Antiviral prophylaxis was applied to all HSCT recipients, of which 65.6% were applied up to 365 days after HSCT. During this study period, only 1 patient (3.1%) experienced herpes zoster at 23 months following HSCT, whose VZV-specific ELISPOT assay showed 0, 1, and 0 spot-forming cells (SFC)/2.0x105 cells before HSCT, 1 and 3 months following HSCT, respectively. The presence of VZV-specific CMI ≥ 1 SFC/ 2.0 × 105 cells was observed in 62.5 % before HSCT, 65.6 % at 1 month, 59.4 % at 3 months, and 70% at 24 months after HSCT, respectively. However, only 18.8 % ,12.5 % and 21.9 % recovered VZV-specific CMI with ≥ 5 SFC/ 2.0 × 105 cells at 1, 3 and 24 months following HSCT. Meanwhile, all the 4 recipients who got the 1st VZV vaccination at 24 months following HSCT showed recovery of VZV-specific CMI with ≥ 5 SFC/ 2.0 × 105 cell. Recovery of VZV-specific CMI after HSCT was not associated with VZV serostatus, chickenpox history, type of HSCT, conditioning regimens, and GVHD. Conclusion Only a few pediatric allogenic HSCT recipients recovered VZV-specific CMI with ≥ 5 SFC/ 2.0 × 105 cell up to 2 years following HSCT. In addition, the association between VZV-specific CMI and VZV reactivation could not be analyzed because no one experienced VZV reactivation within 1 year after HSCT. More long-term large-scale multicenter study is mandatory to supplement these parts. Disclosures All Authors: No reported disclosures.

611: HOST IMMUNE ENDOTYPING IN PEDIATRIC ACUTE RESPIRATORY FAILURE

Introduction: Acute respiratory failure (ARF) is a common reason for admission to the pediatric intensive care unit (PICU). The ability to immune endotype critically ill children with ARF to understand if adaptive or innate defects belie severity of illness, and then modulate these defects by evaluating therapies in an ex vivo fashion may be paradigm shifting. We have previously shown that T-cell IFN-γ (adaptive) and monocyte TNF-α (innate) production, as quantitated by the Enzyme-Linked Immune Absorbent Spot (ELISpot) assay, reflect immune competence in COVID-19 pneumonia, and illness severity is associated with decreased circulating lymphocytes with innate and adaptive immune suppression, evidenced by decreased IFN-ɣ and TNF-α production. This promising approach may have significant benefits in critically ill children, as it is unknown if specific measures of innate and adaptive immune function correlate with illness severity. We hypothesize that serial quantitative analysis of IFN-γ and TNF-α production by ELISpot will accurately reflect host immune status in critically ill children with ARF. Methods: In this IRB approved prospective cohort study, children admitted to the PICU with ARF had serial blood analysis using ELISpot for IFN-γ and TNF-α production after positive stimulus with CD3/28 and LPS respectively. ELISpot reporting for cytokine production is done as number of cells secreting the relevant cytokine; data was compared to relevant patient metadata and clinical outcomes. Results: We are currently enrolling patients, and have analyzed two patients with ARF secondary to pneumonia. Patient 1 had 19 cells secreting IFN-ɣ on day 1 and 69 cells on day 5; and 582 cells secreting TNF-α on day 1 and 1217 cells on day 5. Patient 2 had 18 cells secreting IFN-ɣ on day 1 and 144 cells on day 5; and 189 cells secreting TNF-α on day 1 and 466 cells on day 5. Conclusions: Preliminary analysis of IFN-γ and TNF-α production by ELISpot shows surprisingly more IFN-γ reduction early in disease course, which may be a driver of viral replication and severity of illness. Over 5 days, both patients had appropriately hyper inflammatory innate responses. With improved power and additional time points, there is potential to introduce adaptive stimulants early in disease trajectory that may alter clinical outcomes.

509. Role of cell-mediated immune monitoring using Interferon-γ Enzyme-linked Immunosorbent Spot Assay to predict CMV infection within six months after kidney transplantation

Abstract Background CMV infection can cause substantial morbidity and mortality in kidney transplant (KT) recipients due to an impairment in cell-mediated immunity (CMI) from immunosuppressive drugs. We investigated the role of CMI monitoring prior to and after transplant to predict CMV infection after KT. Methods A prospective study was performed between December 2020 and December 2021. All adult KT recipients underwent CMI measurement by investigating IFN-γ-producing T cells using enzyme-linked immunosorbent (ELISpot) assay before and one month post-transplant. The incidence of CMV infection within six months after transplant was reported, and predictors of CMV infection were analyzed using the Cox proportional hazard model. Results We included 93 KT recipients with a mean (SD) age of 44 (11) years; 59.1% were male, and 98.9% were CMV seropositivity. Twenty-two (23.7%) participants received anti-thymocyte globulin (ATG) for induction therapy. A median (IQR) of IFN-γ-producing T cells measured one month after transplant was significantly lower compared to before transplant (148 [54-389] vs. 763 [409-1,067] SFUs per 2.5 x 105 PBMCs, p &amp;lt; 0.001). Forty (42.9%) KT recipients who developed CMV infection appeared to have significantly less IFN-γ-producing T cells compared to those did not develop CMV infection (47.1%) (115 [33-237] vs. 238[76-492] SFUs/2.5x105 PBMCs, p=0.019). In univariate analysis, predictors for CMV infection included higher panel-reactive antibody (HR 1.02 [95%CI, 1.01-1.03], p&amp;lt; 0.001), receiving ATG for induction therapy (HR 3.45 [95%CI, 1.82-6.56], &amp;lt; 0.001) and lack of CMI one month after transplant defined as IFN-γ-producing T-cells of &amp;lt; 250 SFUs/2.5x105 PBMCs (HR 3.11 [95%CI, 1.36-7.10], p=0.007). In multivariate analysis, lack of CMI one month after transplant is the only predictor which remained independently associated with CMV infection (HR 3.1 [95%CI 1.2-7.80], p=0.019) (Table 1). Conclusion KT recipients with low IFN-γ-producing T cell responses are more likely to develop CMV infection post-transplant. Quantification of CMI using ELISpot assay could potentially predict those at risk of CMV infection after KT. Disclosures All Authors: No reported disclosures.

Isolation of Lytic Bacteriophage against Some Pathogenic Bacteria from Camel's Urine

Background: Antibiotic resistance has been identified as a major hazard to public health in recent years. Using bacteriophages to control bacterial infections seems to be a safer alternative. Methicillin-resistant Staphylococcus aureus (MRSA) Escherichia coli (E.coli) can cause a variety of infections, ranging in severity from fairly insignificant to potentially fatal. Camels' urine has been utilized for therapeutic purposes and anecdotally hailed as a treatment for a variety of ailments for millennia. Alternative eradication strategies must be taken into consideration because of their increased antibiotic resistance, which frequently causes therapeutic failures. Potential candidates to control MRSA &amp;E.coli infections are bacteriophages and their lytic enzymes, lysins. The goal of the current study is to examine the existence of native bacteriophages in camel urine and determine whether they have any antibacterial properties against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E.coli). As well, as the impact of camel’s status on the presence of bacteriophages. Material and methods: In this study, we collected 80 camel urine samples from 6 different areas in the Taif region. The camel's urine was collected from healthy male and female (virgin, mother) camels aged 1–8 years, it has been divided into two groups with different natural feeding patterns G1:which grazes naturally on wild plants ( wild feeding)&amp;G2: which grazes naturally on wild plants, fodder, and barley(mixed feeding). Bacteriophages were isolated by spot assay Results: The phages had good lytic activity against Methicillin-resistant Staphylococcus aureus (MRSA) enterotoxigenic Escherichia coli (E.coli). When evaluated in vitro the greatest activity occurred 24 hours after phage infection. The highest activity of about 100% was achieved by virgin females out of eighty males and female samples. While the ratio represented in male and mother female, 70% 60% respectively. Conclusi

Cellular assays to evaluate B-cell function

Inborn errors of immunity (IEI) that present with recurrent infections are largely due to antibody (Ab) deficiencies. Therefore, assessment of the B-cell and Ab compartment is a major part of immunologic evaluation. Here we provide an overview about cellular assays used to study B-cell function and focus on lymphocyte proliferation assay (LPA), opsonophagocytic assay (OPA), and the Enzyme-linked Immunosorbent Spot Assay (ELISPOT) including clinical applications and limitations of these techniques. LPAs assess ex-vivo cell proliferation in response to various stimuli. Clinically available LPAs utilize peripheral blood mononuclear cells and mostly assess T-cell proliferation with pokeweed mitogen considered the most B-cell specific stimulus. In the research setting, isolating B cells or using more B-cell specific stimuli such as CD40L with IL-4/IL-21 or the TLR9 ligand CpG can more specifically capture the proliferative ability of B cells. OPAs are functional in-vitro killing assays used to evaluate the ability of IgG Ab to induce phagocytosis applied when assessing the potency of vaccine candidates or along with avidity assays to evaluate the quality of secreted IgG. The B-cell ELISPOT assesses Ab production at a cellular level and can characterize the Ab response of particular B-cell subtypes. It can be used in patients on IgG therapy by capturing specific Abs produced by individual B cells, which is not affected by exogenous IgG from plasma donors, and when assessing the vaccine response in patients on immunomodulatory drugs that can affect memory B-cell function. Emerging approaches that are only available in research settings are also briefly introduced.

Betulinic acid mitigates oxidative stress-mediated apoptosis and enhances longevity in the yeast Saccharomyces cerevisiae model

Betulinic acid (BA), a pentacyclic triterpenoid found in certain plant species, has been reported to have several health benefits including antioxidant and anti-apoptotic properties. However, the mechanism by which BA confers these properties is currently unknown. Saccharomyces cerevisiae, a budding yeast with a short life cycle and conserved cellular mechanism with high homology to humans, was used as a model for determining the role of BA in aging and programmed cell death (PCD). Treatment with hydrogen peroxide (H2O2) exhibited significantly increased (30–35%) survivability of antioxidant (sod1Δ, sod2Δ, cta1Δ, ctt1Δ, and tsa1Δ) and anti-apoptotic (pep4Δ and fis1Δ) mutant strains when cells were pretreated with BA (30 µM) as demonstrated in spot and CFU (Colony forming units) assays. Measurement of intracellular oxidation level using the ROS-specific dye H2DCF-DA showed that all tested BA-pretreated mutants exhibited decreased ROS than the control when exposed to H2O2. Similarly, when mutant strains were pretreated with BA and then exposed to H2O2, there was reduced lipid peroxidation as revealed by the reduced malondialdehyde content. Furthermore, BA-pretreated mutant cells showed significantly lower apoptotic activity by decreasing DNA/nuclear fragmentation and chromatin condensation under H2O2-induced stress as determined by DAPI and acridine orange/ethidium bromide staining. In addition, BA treatment also extended the life span of antioxidant and anti-apoptotic mutants by ∼10–25% by scavenging ROS and preventing apoptotic cell death. Our overall results suggest that BA extends the chronological life span of mutant strains lacking antioxidant and anti-apoptotic genes by lowering the impact of oxidative stress, ROS levels, and apoptotic activity. These properties of BA could be further explored for its use as a valuable nutraceutical.

In Vitro Bactericidal Activity of An Environmentally Isolated Phage Cocktail Against a Characterized Recombinant Endolysin Lysecd7 on Clinical Bacterial Isolates

Background: Antimicrobial resistance (AMR) is rapidly spreading, which is pushing humanity into a “post-antibiotic era” where most antibiotics are no longer effective. Scientists are researching bacteriophages as a potential therapy against ESKAPE pathogens, which are a problem in hospital settings, as a result of the development of bacterial resistance to antibiotics. This study assessed the antibacterial efficacy of recombinant LysECD7 and environmental bacteriophage cocktail on bacterial isolates. Materials and Methods: Environmental water and soil samples were examined for the presence of bacteriophages that were capable of killing the bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterobacter cloacae. Utilizing environmental isolates, a bacteriophage cocktail was created and its ability to effectively lyse bacterial growth cultures in vitro was examined. A synthetically generated Myoviridae lytic enzyme named LysECD7 was cloned, produced, and demonstrated wide bactericidal efficacy against gram-negative bacterial pathogens. The bacteriophage cocktail and endolysin’s (0.203mg/ml) antibacterial activity were assessed using a spot assay and an antibacterial activity assay in broth culture. Phage and endolysin bacteria samples were taken and their OD600 levels were checked every 30 minutes for phages and every 30 seconds for endolysin. Results: The average antibacterial activity of isolated bacteriophages was 43.58%, as opposed to the recombinant endolysin’s 31.48%. Bacterial absorbance declined steadily with each subsequent phage replication cycle, however, after six hours, there was a minor improvement in bacterial growth. The Gram-negative E. coli ATCC 25922 and E. cloacae NCTC 134565 exhibited the highest activity for both treatments, while the S. aureus and P. aeruginosa had the lowest activity. Conclusion: A single dose of low endolysin concentration had a very significant antibacterial activity, bacteriophage treatment of bacterial isolates varied greatly per each species under the same conditions. Under the same circumstances, bacteriophage and endolysin activity change within bacterial isolates, demonstrating that activity is independent of concentration. Lysin activity was highest in E. coli and lowest in the other bacterial species, but it should be emphasized that lysin and bacteriophage activity and efficacy differ with each treatment.f

Evaluation of In Vitro Activity of Double-Carbapenem Combinations against KPC-2-, OXA-48- and NDM-Producing Escherichia coli and Klebsiella pneumoniae.

Double-carbapenem combinations have shown synergistic potential against carbapenemase-producing Enterobacterales, but data remain inconclusive. This study evaluated the activity of double-carbapenem combinations against 51 clinical KPC-2-, OXA-48-, NDM-1, and NDM-5-producing Escherichia coli and Klebsiella pneumoniae and against constructed E. coli strains harboring genes encoding KPC-2, OXA-48, or NDM-1 in an otherwise isogenic background. Two-drug combinations of ertapenem, meropenem, and doripenem were evaluated in 24 h time-lapse microscopy experiments with a subsequent spot assay and in static time-kill experiments. An enhanced effect in time-lapse microscopy experiments at 24 h and synergy in the spot assay was detected with one or more combinations against 4/14 KPC-2-, 17/17 OXA-48-, 2/17 NDM-, and 1/3 NDM-1+OXA-48-producing clinical isolates. Synergy rates were higher against meropenem- and doripenem-susceptible isolates and against OXA-48 producers. NDM production was associated with significantly lower synergy rates in E. coli. In time-kill experiments with constructed KPC-2-, OXA-48- and NDM-1-producing E. coli, 24 h synergy was not observed; however, synergy at earlier time points was found against the KPC-2- and OXA-48-producing constructs. Our findings indicate that the benefit of double-carbapenem combinations against carbapenemase-producing E. coli and K. pneumoniae is limited, especially against isolates that are resistant to the constituent antibiotics and produce NDM.

Long-Term CD4+ T-Cell and Immunoglobulin G Immune Responses in Oncology Workers following COVID-19 Vaccination: An Interim Analysis of a Prospective Cohort Study.

We conducted a prospective study to evaluate immune responses to SARS-CoV-2 in oncology workers in which we collected blood and clinical data every 6 months. Spike-specific CD4+ T-cells and immunoglobulin G responses were measured using interferon-gamma enzyme-linked immunosorbent spot and enzyme-linked immunosorbent assay, respectively. Sixty (81%) vaccinated and 14 (19%) unvaccinated individuals were enrolled. CD4+ T-cell responses of those individuals currently naturally infected were comparable to those who were 6 months from receiving their last dose of the vaccine; both responses were significantly higher than among those who were unvaccinated. Unvaccinated participants who became vaccinated while in the study showed a significant increase in both types of spike-specific immune responses. Previously vaccinated individuals who received a third dose (booster) showed a similar response to the spike protein. However, this response decreases as soon as 3 months but does not dip below the established response following two doses. Response to variants of concern B.1.617.2 (Delta) and B.1.1.529 (Omicron) also increased, with the Omicron variant having a significantly lower response when compared to Delta and the wild type. We conclude that antibody and T-cell responses increase in oncology workers after serial vaccination but can wane over time.