Uncovering the diversity of pathogenic invaders: insights into protozoa, fungi, and worm infections

Post COVID-19, there has been renewed interest in understanding the pathogens challenging the human health and evaluate our preparedness towards dealing with health challenges in future. In this endeavour, it is not only the bacteria and the viruses, but a greater community of pathogens. Such pathogenic microorganisms, include protozoa, fungi and worms, which establish a distinct variety of disease-causing agents with the capability to impact the host's well-being as well as the equity of ecosystem. This review summarises the peculiar characteristics and pathogenic mechanisms utilized by these disease-causing organisms. It features their role in causing infection in the concerned host and emphasizes the need for further research. Understanding the layers of pathogenesis encompassing the concerned infectious microbes will help expand targeted inferences with relation to the cause of the infection. This would strengthen and augment benefit to the host's health along with the maintenance of ecosystem network, exhibiting host-pathogen interaction cycle. This would be key to discover the layers underlying differential disease severities in response to similar/same pathogen infection.

Cell-specific housekeeping role of lncRNAs in COVID-19-infected and recovered patients

A plethora of studies have demonstrated the roles of lncRNAs in modulating disease severity and outcomes during infection. However, the spatio-temporal expression of these lncRNAs is poorly understood. In this study, we used single-cell RNA-seq to understand the spatio-temporal expression dynamics of lncRNAs across healthy, SARS-CoV-2-infected, and recovered individuals and their functional role in modulating the disease and recovery. We identified 203 differentially expressed lncRNAs, including cell type-specific ones like MALAT1, NEAT1, ZFAS1, SNHG7, SNHG8, and SNHG25 modulating immune function in classical monocyte, NK T, proliferating NK, plasmablast, naive, and activated B/T cells. Interestingly, we found invariant lncRNAs (no significant change in expression across conditions) regulating essential housekeeping functions (for example, HOTAIR, NRAV, SNHG27, SNHG28, and UCA1) in infected and recovered individuals. Despite similar repeat element abundance, variant lncRNAs displayed higher Alu content, suggesting increased interactions with proximal and distal genes, crucial for immune response modulation. The comparable repeat abundance but distinct expression levels of variant and invariant lncRNAs highlight the significance of investigating the regulatory mechanisms of invariant lncRNAs. Overall, this study offers new insights into the spatio-temporal expression patterns and functional roles of lncRNAs in SARS-CoV-2-infected and recovered individuals while highlighting the importance of invariant lncRNAs in the disease context.

Understanding bacterial pathogenicity: a closer look at the journey of harmful microbes

Bacteria are the most prevalent form of microorganisms and are classified into two categories based on their mode of existence: intracellular and extracellular. While most bacteria are beneficial to human health, others are pathogenic and can cause mild to severe infections. These bacteria use various mechanisms to evade host immunity and cause diseases in humans. The susceptibility of a host to bacterial infection depends on the effectiveness of the immune system, overall health, and genetic factors. Malnutrition, chronic illnesses, and age-related vulnerabilities are the additional confounders to disease severity phenotypes. The impact of bacterial pathogens on public health includes the transmission of these pathogens from healthcare facilities, which contributes to increased morbidity and mortality. To identify the most significant threats to public health, it is crucial to understand the global burden of common bacterial pathogens and their pathogenicity. This knowledge is required to improve immunization rates, improve the effectiveness of vaccines, and consider the impact of antimicrobial resistance when assessing the situation. Many bacteria have developed antimicrobial resistance, which has significant implications for infectious diseases and favors the survival of resilient microorganisms. This review emphasizes the significance of understanding the bacterial pathogens that cause this health threat on a global scale.

Dynamics of Whole Transcriptome Analysis (WTA) and Surface markers expression (AbSeq) in Immune Cells of COVID-19 Patients and Recovered captured through Single Cell Genomics

Introduction

Single-cell multi-omics studies, such as multidimensional transcriptomics (whole transcriptomic analysis, WTA), and surface marker analysis (antibody sequencing, AbSeq), have turned out to be valuable techniques that offer inaccessible possibilities for single-cell profiling of mRNA, lncRNA, and proteins.

Methods

We used this technique to understand the dynamics of mRNA and protein-level differences in healthy, COVID-19-infected and recovered individuals using peripheral blood mononuclear cells (PBMCs). Our results demonstrate that compared to mRNA expression, protein abundance is a better indicator of the disease state.

Results

We demonstrate that compared to mRNA expression, protein abundance is a better indicator of the disease state. We observed high levels of cell identity and regulatory markers, CD3E, CD4, CD8A, CD5, CD7, GITR, and KLRB1 in healthy individuals, whereas markers related to cell activation, CD38, CD28, CD69, CD62L, CD14, and CD16 elevated in the SARS-CoV-2 infected patients at both WTA and AbSeq levels. Curiously, in recovered individuals, there was a high expression of cytokine and chemokine receptors (CCR5, CCR7, CCR4, CXCR3, and PTGRD2). We also observed variations in the expression of markers within cell populations under different states.

Discussion

Furthermore, our study emphasizes the significance of employing an oligo-based method (AbSeq) that can help in diagnosis, prognosis, and protection from disease/s by identifying cell surface markers that are unique to different cell types or states. It also allows simultaneous study of a vast array of markers, surpassing the constraints of techniques like FACS to query the vast repertoire of proteins.

Single-cell RNA-Seq reveals intracellular microbial diversity within immune cells during SARS-CoV-2 infection and recovery

Intracellular microorganisms, like viruses, bacteria, and fungi, pose challenges in detection due to their non-culturable forms. Transcriptomic analysis at cellular level enables exploration of distributions and the impact of these microorganisms on host cells, a domain that remains underexplored because of methodological limitations. Single-cell technology shows promise in addressing this by capturing polyadenine-tailed transcripts, because recent studies confirmed polyadenylation in microbial transcriptomes. We utilized single-cell RNA-seq from PBMCs to probe intracellular microbes in healthy, SARS-CoV-2-positive, and recovered individuals. Among 76 bacterial species detected, 16 showed significant abundance differences. Buchnera aphidicola, Streptomyces clavuligerus, and Ehrlichia canis emerged significantly in memory-B, Naïve-T, and Treg cells. Staphylococcus aureus, Mycoplasma mycoides, Leptospira interrogans, and others displayed elevated levels in SARS-CoV-2-positive patients, suggesting possible disease association. This highlights the strength of single-cell technology in revealing potential microorganism's cell-specific functions. Further research is essential for functional understanding of their cell-specific abundance across physiological states.

Transcriptomic study reveals lncRNA-mediated downregulation of innate immune and inflammatory response in the SARS-CoV-2 vaccination breakthrough infections

INTRODUCTION

The emergence of multiple variants of concerns (VOCs) with higher number of Spike mutations have led to enhanced immune escape by the SARS-CoV-2. With the increasing number of vaccination breakthrough (VBT) infections, it is important to understand the possible reason/s of the breakthrough infections.

METHODS

We performed transcriptome sequencing of 57 VBT and unvaccinated COVID-19 patients, followed by differential expression and co-expression analysis of the lncRNAs and the mRNAs. The regulatory mechanism was highlighted by analysis towards repeat element distribution within the co-expressed lncRNAs, followed by repeats driven homologous interaction between the lncRNAs and the promoter regions of genes from the same topologically associated domains (TAD).

RESULTS

We identified 727 differentially expressed lncRNAs (153 upregulated and 574 downregulated) and 338 mRNAs (34 up- and 334 downregulated) in the VBT patients. This includes LUCAT1, MALAT1, ROR1-AS1, UGDH-AS1 and LINC00273 mediated modulation of immune response, whereas MALAT1, NEAT1 and GAS5 regulated inflammatory response in the VBT. LncRNA-mRNA co-expression analysis highlighted 34 lncRNAs interacting with 267 mRNAs. We also observed a higher abundance of Alu, LINE1 and LTRs within the interacting lncRNAs of the VBT patients. These interacting lncRNAs have higher interaction with the promoter region of the genes from the same TAD, compared to the non-interacting lncRNAs with the enrichment of Alu and LINE1 in the gene promoter.

DISCUSSION

Significant downregulation and GSEA of the TAD gene suggest Alu and LINE1 driven homologous interaction between the lncRNAs and the TAD genes as a possible mechanism of lncRNA-mediated suppression of innate immune/inflammatory responses and activation of adaptive immune response. The lncRNA-mediated suppression of innate immune/inflammatory responses and activation of adaptive immune response might explain the SARS-CoV-2 breakthrough infections with milder symptoms in the VBT. Besides, the study also highlights repeat element mediated regulation of genes in 3D as another possible way of lncRNA-mediated immune-regulation modulating vaccination breakthroughs milder disease phenotype and shorter hospital stay.

The Adjuvanted Recombinant Zoster Vaccine Co-Administered with the 13-valent Pneumococcal Conjugate Vaccine in Adults Aged ≥50 Years: a Randomized Trial

BACKGROUND

Herpes zoster (HZ) results from reactivation of latent varicella-zoster virus. Adults at increased risk of HZ (due to immunocompromising conditions or older age) are also at risk of pneumococcal disease, both of which are preventable by vaccination. We evaluated simultaneous versus sequential administration of the adjuvanted recombinant zoster vaccine (RZV) and the 13-valent pneumococcal conjugate vaccine (PCV13) in adults aged ≥50 years.

METHODS

In this phase IIIB multinational trial (NCT03439657), participants were randomized 1:1 to receive either the first RZV dose and PCV13 simultaneously followed by the second RZV dose two months later (Co-Ad, N=449), or at two-month intervals, PCV13, the first RZV dose, and the second RZV dose sequentially (Control, N=463). Objectives were to demonstrate that immune responses to both vaccines are non-inferior when co-administered compared to sequential administration and to evaluate the safety of their co-administration.

RESULTS

The RZV vaccine response rate (VRR) in the Co-Ad group was 99.1% (95% confidence interval [CI]: 97.6-99.7), meeting the VRR success criterion. Non-inferiority criteria for the Co-Ad versus Control group were also met for anti-glycoprotein E antibodies (adjusted geometric mean concentration Control/Co-Ad ratio 1.07 [95%CI: 0.99-1.16]) and all PCV13 serotypes (adjusted antibody geometric mean titer Control/Co-Ad ratios 1.02 [95%CI: 0.86-1.22] to 1.36 [95%CI: 1.07-1.73]). Upon co-administration, the frequency of solicited local adverse events was consistent with the known safety profile of each individual vaccine, whereas solicited general adverse events were within the same range as for RZV alone.

CONCLUSIONS

RZV co-administered with PCV13 had an acceptable safety profile. Humoral immune responses to both vaccines were non-inferior when co-administered compared to sequential administration. These results suggest that adults may benefit from receiving RZV and a PCV at the same healthcare visit.

08. Concomitant Administration of the Adjuvanted Recombinant Zoster Vaccine (RZV) with 13-Valent Pneumococcal Conjugate Vaccine (PCV13) Is Safe and Does Not Interfere with Immunogenicity of Either Vaccine in Adults Aged ≥ 50 Years

Background

This study assessed non-inferiority of humoral immunogenicity, reactogenicity, and safety of RZV when the 1st dose was co-administered with PCV13 in adults ≥ 50 years of age (YOA) compared to sequential administration.

Methods

In this phase 3b, open-label, multi-center study (NCT03439657), adults were randomized 1:1 to receive either the 1st RZV dose co-administered with PCV13 at day (D)1 and the 2nd RZV dose at month (M)2 (Co-Ad group), or PCV13 at D1, the 1st RZV dose at M2 and the 2nd RZV dose at M4 (Control group). Co-primary confirmatory objectives were: (i) vaccine response rate (VRR) to RZV at 1 month post-dose 2 in Co-Ad group; (ii) non-inferiority of humoral responses to RZV (1 month post-RZV dose 2) and PCV13 (1 month post-PCV13) in Co-Ad group compared to Control group. Solicited adverse events (AEs) until D7 post-vaccination and unsolicited AEs until D30 post-vaccination were recorded. Serious AEs (SAEs) and potential immune-mediated diseases (pIMDs) were collected through 12 months post-RZV dose 2. Immunogenicity was performed in the per-protocol set (PPS) and safety analyses in the exposed set.

Results

Of 912 vaccinated adults, 863 were included in PPS (Co-Ad: 427; Control: 436). VRR for anti-glycoprotein E antibody concentrations was 99.1% in Co-Ad group. The predefined non-inferiority criteria for the humoral immune responses to RZV and PCV13 were met (Table 1). The overall frequency of solicited local AEs after RZV and PCV13 was comparable between Co-Ad and Control groups. Pain was the most common solicited local AE (Figure 1). The frequency of solicited general AEs was similar for the 1st RZV dose when co-administered with PCV13 or alone (57.4% vs 54.6%). Myalgia and fatigue were the most common solicited general AEs (Figure 2). The frequency (Co-Ad: 21.2%; Control: 23.1%) and nature of unsolicited AEs were balanced between groups. None of the reported SAEs, fatal SAEs, or pIMDs were vaccine-related.

Table 1. Co-primary confirmatory objectives: vaccine response rate (VRR), and non-inferiority of the immune responses to RZV (1 month post-dose 2) and to PCV13 (1 month post-vaccination) in the Co-Ad group vs the Control group (per-protocol set)

Figure 1. The incidence of solicited local adverse events (AEs) occurring within 7 days post-vaccination (overall/adult, exposed set)

Figure 2. The incidence of solicited general adverse events (AEs) post-dose 1 occurring within 7 days post-vaccination (exposed set)

Conclusion

Co-administration of the 1st RZV dose with PCV13 showed non-inferior immune responses to sequential administration. The reactogenicity and safety of RZV in the Co-Ad group were within the range of the established safety profile of RZV. Co-administration of RZV with PCV13 may improve vaccination rates in ≥ 50 YOA population.

Funding

GlaxoSmithKline Biologicals SA

Disclosures

Ji-Young Min, PhD, GSK group of companies (Employee) Agnes Mwakingwe-Omar, MD, PhD, GSK group of companies (Employee) Megan Riley, PhD, GSK group of companies (Employee, Shareholder) Lifeter Yenwo Molo, BsC(hons) MSc(hons), GSK group of companies (Employee) Jyoti Soni, MA, GSK group of companies (Employee) Ginette Girard, MD, Diex Recherche Inc. Sherbrooke (Scientific Research Study Investigator) Jasur Danier, MD, GSK group of companies (Employee, Shareholder)

Association Between Hemagglutination Inhibition Antibody Titers and Protection Against Reverse-Transcription Polymerase Chain Reaction–Confirmed Influenza Illness in Children 6–35 Months of Age: Statistical Evaluation of a Correlate of Protection

Background

Data from a randomized controlled efficacy trial of an inactivated quadrivalent influenza vaccine in children 6–35 months of age were used to determine whether hemagglutination inhibition (HI) antibody titer against A/H1N1 and A/H3N2 is a statistical correlate of protection (CoP) for the risk of reverse-transcription polymerase chain reaction (RT-PCR)–confirmed influenza associated with the corresponding strain.

Methods

The Prentice criteria were used to statistically validate strain-specific HI antibody titer as a CoP. The probability of protection was identified using the Dunning model corresponding to a prespecified probability of protection at an individual level. The group-level protective threshold was identified using the Siber approach, leading to unbiased predicted vaccine efficacy (VE). A case-cohort subsample was used for this exploratory analysis.

Results

Prentice criteria confirmed that HI titer is a statistical CoP for RT-PCR–confirmed influenza. The Dunning model predicted a probability of protection of 49.7% against A/H1N1 influenza and 54.7% against A/H3N2 influenza at an HI antibody titer of 1:40 for the corresponding strain. Higher titers of 1:320 were associated with >80% probability of protection. The Siber method predicted VE of 61.0% at a threshold of 1:80 for A/H1N1 and 46.6% at 1:113 for A/H3N2.

Conclusions

The study validated HI antibody titer as a statistical CoP, by demonstrating that HI titer is correlated with clinical protection against RT-PCR–confirmed influenza associated with the corresponding influenza strain and is predictive of VE in children 6–35 months of age.

Clinical Trials Registration

NCT01439360.

1239. Different Dose Levels of a Respiratory Syncytial Virus Maternal Vaccine Candidate (RSVPreF3) Administered to Non-pregnant Women in a Randomized Clinical Trial Are Immunogenic and Well Tolerated

Background

Respiratory syncytial virus (RSV) is a leading cause of bronchiolitis and pneumonia in childhood. Maternal immunization could help to protect infants from RSV-associated infections in their first months of life. We evaluated the safety, reactogenicity and immunogenicity of the RSV maternal (RSVPreF3) vaccine candidate in non-pregnant women, at different dose levels.

Methods

In this phase I/II, observer-blind, multicenter study (NCT03674177), healthy non-pregnant women aged 18–45 years were randomized (1:1:1:1) and received 1 dose of either 30, 60 or 120 µg of RSVPreF3 vaccine (30/60/120 RSVPreF3 group) or placebo. Solicited adverse events (AEs) (until day 7 [D7] post-vaccination), unsolicited AEs (until D30 post-vaccination), hematological and biochemical laboratory abnormalities (at D8 and D31 post-vaccination) were recorded. Serious AEs (SAEs) were collected until D181 and immune responses until D91 post-vaccination. Exploratory analysis was performed at D31 to compare immunogenicity of different dose levels.

Results

502 women were included in the exposed set. The most frequently reported solicited AEs were pain and headache (Fig 1). Grade 3 solicited AEs were infrequently reported. 180 women experienced unsolicited AEs; 19 reported grade 3 unsolicited AEs, among which 1 was vaccination-related (60 RSVPreF3). 3 SAEs were reported (1 in 120 RSVPreF3; 2 in placebo); none was related to vaccination. No clinically significant changes in laboratory parameters occurred. Geometric mean titers of anti-RSV A neutralizing antibody (≥ 8-fold at D8 and ≥ 5-fold until D91 vs baseline) and geometric mean concentrations of anti-RSVPreF3 IgG antibody (≥ 12-fold at D8 and ≥ 6-fold until D91 vs baseline) were boosted in all RSVPreF3 groups (Fig 2, 3). The 60 and 120 µg dose levels of RSVPreF3 were significantly more immunogenic than the 30 µg one.

Figure 1. Solicited adverse events until day 7 post-vaccination

Figure 2. GMTs of anti-RSV A neutralizing antibody (ED60) until day 91 post-vaccination

Figure 3. GMCs of RSVPreF3 IgG antibody (EU/mL) until day 91 post-vaccination

Conclusion

All RSVPreF3 vaccine dose levels were well tolerated and no safety concerns identified. All 3 dose levels were immunogenic, with higher immune response induced by the 60 and 120 µg dose levels than the 30 µg one. These data support the further investigation of the 60 and 120 µg RSVPreF3 dose levels in pregnant women.

Funding

GlaxoSmithKline Biologicals SA

Acknowledgment

N Bulik/Q Deraedt (Modis c/o GSK) provided writing/editorial support

Disclosures

Tino Schwarz, PhD, GSK group of companies (Scientific Research Study Investigator, Speaker’s Bureau) Christine Grigat, MD, GSK group of companies (Scientific Research Study Investigator) Dan Apter, MD, PhD, GSK group of companies (Research Grant or Support) Peter Csonka, MD, PhD, GSK group of companies (Scientific Research Study Investigator) Thi Lien-Anh Nguyen, PhD, GSK group of companies (Employee, Shareholder) Feng F. Gao, PhD, GSK group of companies (Employee) Jyoti Soni, MA, GSK group of companies (Employee) Antonella Nadia Tullio, Dr., GSK group of companies (Employee) Ilse Dieussaert, IR, GSK group of companies (Employee, Shareholder) Marta Picciolato, PharmD, MSc, GSK group of companies (Employee) Ouzama Henry, MD, GSK group of companies (Employee, Shareholder)

Anamnestic Immune Response and Safety of an Inactivated Quadrivalent Influenza Vaccine in Primed Versus Vaccine-Naïve Children

BACKGROUND

It has not yet been demonstrated whether 2 doses of inactivated quadrivalent influenza vaccine (IIV4) prime a booster response in infants. We evaluated the anamnestic immune response to an IIV4 in children 17-48 months of age.

METHODS

Children were randomized to 2 doses of IIV4 or control in the primary phase III study (NCT01439360). One year later, in an open-label revaccination extension study (NCT01702454), a subset of children who received IIV4 in the primary study (primed group) received 1 IIV4 dose and children who received control in the primary study (unprimed) received 2 IIV4 doses 28 days apart. The primary objective was to evaluate hemagglutination inhibition (HI) antibody titers 7 days after first IIV4 vaccination in the per-protocol cohort (N = 224 primed; N = 209 unprimed). Neutralizing and antineuraminidase antibodies were also measured. Safety was analyzed in the total vaccinated cohort (N = 241 primed; N = 229 unprimed).

RESULTS

An anamnestic response was observed in primed children relative to unprimed controls, measured by age-adjusted geometric mean HI titer ratios against strains homologous (A/H1N1: 9.0; B/Victoria: 3.9) and heterologous (A/H3N2: 2.7; B/Yamagata: 6.7) to those in the primary vaccination series. The anamnestic response in primed children included increases in neutralizing antibodies (mean geometric increase: 5.0-10.6) and antineuraminidase antibodies (4.9-8.8). No serious adverse events related to vaccination were reported.

CONCLUSIONS

In this study, 2-dose priming with IIV4 induced immune memory that was recalled with 1-dose IIV4 the following year to boost HI, antineuraminidase and neutralizing antibodies, even though the IIV4 strain composition partially changed.

Prevention of vaccine-matched and mismatched influenza in children aged 6-35 months: a multinational randomised trial across five influenza seasons

BACKGROUND

Despite the importance of vaccinating children younger than 5 years, few studies evaluating vaccine prevention of influenza have been reported in this age group. We evaluated efficacy of an inactivated quadrivalent influenza vaccine (IIV4) in children aged 6-35 months.

METHODS

In this phase 3, observer-blinded, multinational trial, healthy children from 13 countries in Europe, Central America, and Asia were recruited in five independent cohorts, each in a different influenza season. Participants were randomly assigned (1:1) to either IIV4 (15 μg haemagglutinin antigen per strain per 0·5 mL dose; a single dose on day 0 for vaccine-primed children, and two doses, on days 0 and 28, for vaccine-unprimed children) or to one or two doses of a non-influenza control vaccine. Primary endpoints were moderate-to-severe influenza or all influenza (irrespective of disease severity) confirmed by RT-PCR on nasal swabs. Cultured isolates were further characterised as antigenically matched or mismatched to vaccine strains. Efficacy was assessed in the per-protocol cohort and total vaccinated cohort (time-to-event analysis), and safety was assessed in the total vaccinated cohort.

FINDINGS

Between Oct 1, 2011, and Dec 31, 2014, 12 018 children were recruited into the total vaccinated cohort (6006 children in the IIV4 group and 6012 children in the control group). 356 (6%) children in the IIV4 group and 693 (12%) children in the control group had at least one case of RT-PCR-confirmed influenza. Of these 1049 influenza strains, 138 (13%) were A/H1N1, 529 (50%) were A/H3N2, 69 (7%) were B/Victoria, and 316 (30%) were B/Yamagata. Overall, 539 (64%) of 848 antigenically characterised isolates were vaccine-mismatched (16 [15%] of 105 for A/H1N1; 368 [97%] of 378 for A/H3N2; 54 [86%] of 63 for B/Victoria; 101 [33%] of 302 for B/Yamagata). Vaccine efficacy was 63% (97·5% CI 52-72) against moderate-to-severe influenza and 50% (42-57) against all influenza in the per-protocol cohort, and 64% (53-73) against moderate-to-severe influenza and 50% (42-57) against all influenza in the total vaccinated cohort. There were no clinically meaningful safety differences between IIV4 and control.

INTERPRETATION

IIV4 prevented influenza A and B in children aged 6-35 months despite high levels of vaccine mismatch. Vaccine efficacy was highest against moderate-to-severe disease, which is the most clinically important endpoint associated with greatest burden.

FUNDING

GlaxoSmithKline Biologicals SA.

Immunogenicity and safety of an AS03-adjuvanted H7N1 vaccine in adults 65years of age and older: A phase II, observer-blind, randomized, controlled trial

BACKGROUND

H7 influenza strains can cause severe and often fatal human infections, especially in the elderly. This phase II, observer-blind, randomized trial (www.ClinicalTrials.gov: NCT01949090) assessed the immunogenicity and safety of a novel AS03-adjuvanted H7N1 vaccine that may serve as a model H7-subtype vaccine.

METHODS

360 adults ≥65years of age in stable health received either 1 of 4 adjuvanted A/mallard/Netherlands/12/2000 split virion vaccine formulations (3.75μg or 7.5μg hemagglutinin adjuvanted with either AS03_A or AS03_B) or saline placebo, given as a 2-dose series. Immunogenicity was assessed using hemagglutination-inhibition (HI) and microneutralization (MN) assays for the per-protocol cohort, comprising 332 participants at 21days post-each dose, 332 at month 6, and 309 at month 12 (HI assay only). Safety was assessed up to month 12 for all participants who had received ≥1 dose (360 participants).

RESULTS

For H7N1 HI antibody assessment at day 42 (21days post-dose 2), seroprotection rates (SPR) in the vaccinated groups were 69.6%-88.7%, seroconversion rates (SCR) 69.6%-88.5%, mean geometric increase (MGI) 11.0-18.9, and HI geometric mean titers (GMTs) 55.0-104.8. These parameters declined by month 6 and month 12. Microneutralization GMTs were 46.2-74.7 in the vaccinated groups at day 42, while vaccine response rate (VRR; proportion with ≥4-fold increase in MN titer) was 46.4%-81.5%. For the cross-reactive H7N9 strain, at day 42, HI GMT were 64.3-201.3, SPR 78.6%-96.3%, SCR 79.3%-96.3%, and MGI 14.1-37.7; MN GMTs were 44.0-85.6, and VRR 46.4-85.2%. The most frequent solicited symptom was injection site pain (41.7%-65.0% of vaccine recipients). In total, 40 participants reported 67 serious adverse events; none were considered causally related to vaccination.

CONCLUSIONS

In adults aged ≥65years, the adjuvanted H7N1 vaccine was immunogenic after 2 doses, and had an acceptable safety profile. www.ClinicalTrials.gov: NCT01949090.

Time to Change Dosing of Inactivated Quadrivalent Influenza Vaccine in Young Children: Evidence From a Phase III, Randomized, Controlled Trial

BACKGROUND.

Children under 3 years of age may benefit from a double-dose of inactivated quadrivalent influenza vaccine (IIV4) instead of the standard-dose.

METHODS.

We compared the only United States-licensed standard-dose IIV4 (0.25 mL, 7.5 µg hemagglutinin per influenza strain) versus double-dose IIV4 manufactured by a different process (0.5 mL, 15 µg per strain) in a phase III, randomized, observer-blind trial in children 6-35 months of age (NCT02242643). The primary objective was to demonstrate immunogenic noninferiority of the double-dose for all vaccine strains 28 days after last vaccination. Immunogenic superiority of the double-dose was evaluated post hoc. Immunogenicity was assessed in the per-protocol cohort (N = 2041), and safety was assessed in the intent-to-treat cohort (N = 2424).

RESULTS.

Immunogenic noninferiority of double-dose versus standard-dose IIV4 was demonstrated in terms of geometric mean titer (GMT) ratio and seroconversion rate difference. Superior immunogenicity against both vaccine B strains was observed with double-dose IIV4 in children 6-17 months of age (GMT ratio = 1.89, 95% confidence interval [CI] = 1.64-2.17, B/Yamagata; GMT ratio = 2.13, 95% CI = 1.82-2.50, B/Victoria) and in unprimed children of any age (GMT ratio = 1.85, 95% CI = 1.59-2.13, B/Yamagata; GMT ratio = 2.04, 95% CI = 1.79-2.33, B/Victoria). Safety and reactogenicity, including fever, were similar despite the higher antigen content and volume of the double-dose IIV4. There were no attributable serious adverse events.

CONCLUSIONS.

Double-dose IIV4 may improve protection against influenza B in some young children and simplifies annual influenza vaccination by allowing the same vaccine dose to be used for all eligible children and adults.

Immunogenicity and safety of an AS03-adjuvanted H7N1 vaccine in healthy adults: A phase I/II, observer-blind, randomized, controlled trial

BACKGROUND

H7 influenza strains have pandemic potential. AS03-adjuvanted H7N1 A/mallard/Netherlands/12/2000 split-virion vaccine formulations were evaluated as model H7-subtype vaccine and tested after H7N9 emerged in China, and caused severe human disease with high mortality.

METHODS

In this phase I/II, observer-blind, randomized trial in US and Canada, 420 healthy adults (21-64years) were randomized to receive 1 of 4 H7N1 vaccine formulations (3.75 or 7.5μg hemagglutinin adjuvanted with either AS03_A or AS03_B), 15μg unadjuvanted H7N1 hemagglutinin, or saline placebo, given as 2-dose series. Immunogenicity was assessed using hemagglutination-inhibition (HI) and microneutralization (MN) assays, at day 42 (21days post-dose 2), month 6, and month 12 (HI only) for the per-protocol cohorts (398, 379 and 368 participants, respectively). Safety is reported up to month 12.

RESULTS

Beneficial AS03 adjuvant effect was demonstrated. Committee for Medical Products for Human Use, and Center for Biologics Evaluation and Research (CBER) criteria were met for all adjuvanted formulations at day 42 (H7N1 HI assay); seroprotection (SPR) and seroconversion rates (SCR) were 88.5-94.8%, mean geometric increase (MGI) 19.2-34.9, and geometric mean titers (GMT) 98.3-180.7. Unadjuvanted H7N1 vaccine did not meet CBER criteria. In adjuvanted groups, antibody titers decreased over time; month 12 SPRs and GMTs were low (2.0-18.8% and 8.1-12.2). MN antibodies showed similar kinetics, with titers persisting at higher range than HI at month 6. All adjuvanted groups showed cross-reactivity against H7N9, with HI responses similar to H7N1. The most frequent solicited symptom in adjuvanted groups was injection site pain (71.2-86.7%); grade 3 solicited symptoms were infrequent. Nine participants reported 17 serious adverse events; none were considered causally related to vaccination.

CONCLUSIONS

Adjuvanted H7N1 vaccine formulations had an acceptable safety profile and induced an antibody response after 2 doses with cross-reactivity to H7N9. ClinicalTrials.gov: NCT01934127.

Immunogenicity and safety of Southern Hemisphere inactivated quadrivalent influenza vaccine: a Phase III, open-label study of adults in Brazil

The World Health Organization influenza forecast now includes an influenza B strain from each of the influenza B lineages (B/Yamagata and B/Victoria) for inclusion in seasonal influenza vaccines. Traditional trivalent influenza vaccines include an influenza B strain from one lineage, but because two influenza B lineages frequently co-circulate, the effectiveness of trivalent vaccines may be reduced in seasons of influenza B vaccine-mismatch. Thus, quadrivalent vaccines may potentially reduce the burden of influenza compared with trivalent vaccines.

In this Phase III, open-label study, we assessed the immunogenicity and safety of Southern Hemisphere inactivated quadrivalent influenza vaccine (Fluarix™ Tetra) in Brazilian adults (NCT02369341). The primary objective was to assess hemagglutination-inhibition antibody responses against each vaccine strain 21 days after vaccination in adults (aged ≥18–60 years) and older adults (aged >60 years). Solicited adverse events for four days post-vaccination, and unsolicited adverse events and serious adverse events for 21 days post-vaccination were also assessed.

A total of 63 adults and 57 older adults received one dose of inactivated quadrivalent influenza vaccine at the beginning of the 2015 Southern Hemisphere influenza season. After vaccination, in adults and older adults, the hemagglutination-inhibition titers fulfilled the European licensure criteria for immunogenicity. In adults, the seroprotection rates with HI titer ≥1:40 were 100% (A/H1N1), 98.4% (A/H3N2), 100% (B/Yamagata), and 100% (B/Victoria); in older adults were 94.7% (A/H1N1), 96.5% (A/H3N2), 100% (B/Yamagata), and 100% (B/Victoria). Pain was the most common solicited local adverse events in adults (27/62) and in older adults (13/57), and the most common solicited general adverse events in adults was myalgia (9/62), and in older adults were myalgia and arthralgia (both 2/57). Unsolicited adverse events were reported by 11/63 adults and 10/57 older adults.

The study showed that inactivated quadrivalent influenza vaccine was immunogenic and well-tolerated in Brazilian adults and older adults.

Immunogenicity and Safety of an AS03-Adjuvanted H7N9 Pandemic Influenza Vaccine in a Randomized Trial in Healthy Adults

Background

Almost 700 cases of human infection with avian influenza A/H7N9 have been reported since 2013. Pandemic preparedness strategies include H7N9 vaccine development.

Methods

We evaluated an inactivated H7N9 vaccine in an observer-blind study in healthy adults aged 18–64 years. Participants (420) were randomized to receive 1 of 4 AS03-adjuvanted vaccines (low or medium dose of hemagglutinin with AS03_A or AS03_B), one nonadjuvanted vaccine, or placebo. The coprimary immunogenicity objective determined whether adjuvanted vaccines elicited an immune response against the vaccine-homologous virus, 21 days after the second vaccine dose per US and European licensure criteria in the per-protocol cohort (n = 389).

Results

All adjuvanted vaccines met regulatory acceptance criteria. In groups receiving adjuvanted formulations, seroconversion rates were ≥85.7%, seroprotection rates ≥91.1%, and geometric mean titers ≥92.9% versus 23.2%, 28.6%, and 17.2 for the nonadjuvanted vaccine. The AS03 adjuvant enhanced immune response at antigen-sparing doses. Injection site pain occurred more frequently with adjuvanted vaccines (in ≤98.3% of vaccinees) than with the nonadjuvanted vaccine (40.7%) or placebo (20.0%). None of the 20 serious adverse events reported were related to vaccination.

Conclusions

Two doses of AS03-adjuvanted H7N9 vaccine were well tolerated and induced a robust antibody response at antigen-sparing doses in healthy adults.

Clinical Trials Registration

NCT01999842.

Overview of ion source characterization diagnostics in INTF

INdian Test Facility (INTF) is envisaged to characterize ITER diagnostic neutral beam system and to establish the functionality of its eight inductively coupled RF plasma driver based negative hydrogen ion source and its beamline components. The beam quality mainly depends on the ion source performance and therefore, its diagnostics plays an important role for its safe and optimized operation. A number of diagnostics are planned in INTF to characterize the ion source performance. Negative ions and its cesium contents in the source will be monitored by optical emission spectroscopy (OES) and cavity ring down spectroscopy. Plasma near the extraction region will be studied using standard electrostatic probes. The beam divergence and negative ion stripping losses are planned to be measured using Doppler shift spectroscopy. During initial phase of ion beam characterization, carbon fiber composite based infrared imaging diagnostics will be used. Safe operation of the beam will be ensured by using standard thermocouples and electrical voltage-current measurement sensors. A novel concept, based on plasma density dependent plasma impedance measurement using RF electrical impedance matching parameters to characterize the RF driver plasma, will be tested in INTF and will be validated with OES data. The paper will discuss about the overview of the complete INTF diagnostics including its present status of procurement, experimentation, interface with mechanical systems in INTF, and integration with INTF data acquisition and control systems.

Giant Goos-Hänchen shift in scattering: the role of interfering localized plasmon modes

The longitudinal and transverse beam shifts, namely, the Goos-Hänchen (GH) and the Spin-Hall (SH) shifts are usually observed at planar interfaces. It has recently been shown that the transverse SH shift may also arise due to scattering of plane waves. Here, we show that analogous in-plane (longitudinal) shifts also exist in the scattering of plane waves from micro/nano systems. We study both the GH and the SH shifts in plasmonic metal nanoparticles/nanostructures and dielectric micro-particles employing a unified framework that utilizes the transverse components of the Poynting vector of the scattered wave. The results demonstrate that the interference of neighboring resonance modes in plasmonic nanostructures (e.g., electric dipolar and quadrupolar modes in metal spheres) leads to great enhancement of the GH shift in scattering from such systems. We also unravel interesting correlations between these shifts with the polarimetry parameters, diattenuation and retardance.

Quantitative Mueller matrix fluorescence spectroscopy for precancer detection

Quantitative fluorescence spectroscopic Mueller matrix measurements from the connective tissue regions of human cervical tissue reveal intriguing fluorescence diattenuation and polarizance effects. Interestingly, the estimated fluorescence linear diattenuation and polarizance parameters were considerably reduced in the precancerous tissues as compared to the normal ones. These polarimetry effects of the autofluorescence were found to originate from anisotropically organized collagen molecular structures present in the connective tissues. Consequently, the reduction of the magnitude of these polarimetric parameters at higher grades of precancer was attributed to the loss of anisotropic organization of collagen, which was also confirmed by control experiments. These results indicate that fluorescence spectral diattenuation and polarizance parameters may serve as potentially useful diagnostic metrics.

Design and characterization of a nano-Newton resolution thrust stand

The paper describes the design, calibration, and characterization of a thrust stand capable of nano-Newton resolution. A low uncertainty calibration method is proposed and demonstrated. A passive eddy current based damper, which is non-contact and vacuum compatible, is employed. Signal analysis techniques are used to perform noise characterization, and potential sources are identified. Calibrated system noise floor suggests thrust measurement resolution of the order of 10 nN is feasible under laboratory conditions. Force measurement from this balance for a standard macroscale dielectric barrier discharge (DBD) plasma actuator is benchmarked with a commercial precision balance of 9.8 μN resolution and is found to be in good agreement. Published results of a microscale DBD plasma actuator force measurement and low pressure characterization of conventional plasma actuators are presented for completeness.

Enhancing spin-orbit interaction of light by plasmonic nanostructures

The spin orbit interactions (SOI) of light mediated by single scattering from plasmon resonant metal nanoparticles (nanorods and nanospheres) are investigated using Jones and Mueller matrix polarimetry formalism. The effect of neighboring resonances in plasmonic nanostructures (e.g., orthogonal electric dipolar modes in rods or electric dipolar and quadrupolar modes in spheres) on the individual SOI effects are analyzed and interpreted via the Mueller matrix-derived polarimetry characteristics, namely, diattenuation d and retardance δ. The results clearly reveal that each of these can be controllably tuned and enhanced by exploiting the interference of neighboring modes.

Multiple delivery cesium oven system for negative ion sources

Distribution of cesium in large negative ion beam sources to be operational in ITER, is presently based on the use of three or more cesium ovens, which operate simultaneously and are controlled remotely. However, use of multiple Cs ovens simultaneously is likely to pose difficulties in operation and maintenance of the ovens. An alternate method of Cs delivery, based on a single oven distribution system is proposed as one which could reduce the need of simultaneous operation of many ovens. A proof of principle experiment verifying the concept of a multinozzle distributor based Cs oven has been carried out at Institute for Plasma Research. It is also observed that the Cs flux is not controlled by Cs reservoir temperature after few hours of operation but by the temperature of the distributor which starts behaving as a Cs reservoir.

Rat, ovine and bovine Peyer's patches mounted in horizontal diffusion chambers display sampling function

Freshly excised rat, ovine and bovine ileal Peyer's patch (PP) and non-Peyer's patch tissues (NPP) were mounted in modified horizontal polyethylene diffusion chambers with a range of window areas. Rat tissue was initially used to establish that barrier function and histology were maintained for up to 60 min. Horse-radish peroxidase (HRP) fluxes and S. Typhimurium adherence and invasion were significantly higher in rat PP over NPP. Particle uptake was shown to be a rapid, energy-, time-, and size-dependent process, occurring more readily in PP than NPP tissue in each species. In a kinetic analysis, particles were localized initially in the follicle-associated epithelium and then in the dome region. For NPP uptake, particles were initially localized to villous epithelium, and were then detected in the crypts and lamina propria. Electrophysiological parameters including pharmacologically-stimulated inward short-circuit current responses were determined in isolated PP and NPP from each species mounted under identical conditions in Ussing chambers. In conclusion, comparative functional and histological characteristics of PP from several species were demonstrated in horizontal diffusion chambers. Horizontal diffusion chambers are therefore a useful in vitro model in which a range of functions including transport of particulate formulations by PP may be examined.

Effect of Vitamin E and selenium supplementation on concentrations of plasma cortisol and erythrocyte lipid peroxides and the incidence of retained fetal membranes in crossbred dairy cattle

The objectives were to: (i) determine the effect of prepartum supplementation of Vitamin E (Vit E) and selenium (Se) on plasma cortisol, erythrocyte peroxidation and the incidence of retained fetal membranes (RFM); (ii) estimate myeloperoxidase (MPO), lysozyme, elastase, and acid phosphatase (ACP) enzyme activities in the cotyledons of cows with or without RFM; and (iii) determine the molecular weight (SDS-PAGE) of proteins present in the cotyledons of cows with or without RFM. Fifty dairy (Friesian x Sahiwal) cows were equally allocated to one of two treatments, given as an im injection 3 week before calving: 1100 IU of DL alpha-tocopherol acetate (Vit E) and 30 mg of sodium selenite (Se), or saline (control). Concentrations of plasma cortisol (20 cows) were determined on days 21, 7, 3, 2, 1, and 0 prepartum, and erythrocyte lipid peroxide (all cows) was determined on days 21 and 7 prepartum. Treatment with Vit E and Se did not affect (P = 0.23) the incidence of RFM (12% versus 0%, respectively) but decreased (P < 0.05) erythrocyte lipid peroxide concentrations on day 7 prepartum compared with day 21 prepartum. Plasma cortisol concentration increased (P < 0.05) from day 21 prepartum to the day of parturition in Vit E+Se and control cows. However, on day 0, plasma cortisol concentrations were lower (P<0.05) in cows given Vit E+Se than in control cows (with or without RFM). To investigate enzyme activity and peptides in cotyledons, cotyledons were collected (from cows that were not part of the principal experiment), homogenised with PBS, and the supernatant used for the estimation of cationic peptides. Cotyledons of cows with RFM (n = 8) had lower (P < 0.01) MPO and greater (P < 0.05) lysozyme and ACP enzyme activities than those from non-RFM cows (n = 6). A band at <10 kDa in the SDS-PAGE indicated the presence of cationic peptides. In conclusion, a single treatment of Vit E and Se at 3-week prepartum reduced concentrations of plasma cortisol and erythrocyte peroxide. Altered enzyme activities in the fetal membranes indicated the involvement of leukocytes and trauma at the fetomaternal junction and warrant further investigation.

The use of clock tests in schizophrenia

Though clock drawing tests are well recognized as measures of cognitive function, there is little data on the performance of patients with schizophrenia. We compared 24 patients with schizophrenia to 24 healthy, age-matched controls on clock drawing, copying, and reading. Patients with schizophrenia performed significantly worse on clock drawing and copying despite the fact that the groups had similar scores on the MMSE. Worse performance was associated with higher scores on the BPRS. Clock drawing and copying may be useful for the assessment of cognition in schizophrenia, and the monitoring of cognitive changes associated with antipsychotic medication.

A single i.v. dose of ondansetron 8 mg prior to induction of anaesthesia reduces postoperative nausea and vomiting in gynaecological patients

The effect of a single intravenous dose of ondansetron in preventing postoperative nausea and emesis (retching and vomiting) (PONV) was investigated in a randomized, double-blind, placebo-controlled, multicentre, international study. Women of ASA class I-III, requiring gynaecological laparotomy, vaginal hysterectomy, or major vaginal surgery were selected for study. Two hundred and thirty-five received placebo, 231 received 1 mg ondansetron, 228 received 8 mg ondansetron and 229 received 16 mg ondansetron, as an infusion over five minutes before the induction of anaesthesia. A standardized balanced anaesthetic technique was employed. This consisted of premedication with either diazepam or temazepam, thiopentone induction, maintenance with nitrous oxide in oxygen supplemented with enflurane or isoflurane, intraoperative analgesia with fentanyl, neuromuscular blockade with any choice of agent and reversal with neostigmine and atropine. Postoperative analgesia was achieved with morphine, and prochlorperazine or metoclopramide were given if a rescue antiemetic was required. A greater percentage of patients in the 8 mg and 16 mg ondansetron groups experienced no postoperative emesis (44% and 39% respectively) than in the placebo and 1 mg ondansetron groups (29% and 28% respectively) for the first 24 hr postoperative period (8 mg vs placebo and 1 mg: P < or = 0.001; 16 mg vs placebo: P < 0.05; 16 mg vs 1 mg: P < 0.05). Similarly, the percentage of patients who did not experience postoperative nausea were 20%, 26%, 31% and 28% for the placebo, 1 mg, 8 mg and 16 mg ondansetron treatment groups, respectively (8 mg and 16 mg vs placebo P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[Initial phase of the left ventricular ejection (mesosystole) in coronary artery disease]

In patients with coronary artery disease (CAD), the ventricular ejection is altered specially the initial phase or the mid-systole. We studied such abnormalities through two-dimensional echocardiography and phonocardiography. We studied 40 patients with CAD and 11 normal subjects, we determined the times and volumes of total, initial and end of systole for to calculate the ejection fraction, integrated ejection and mean ejection rate. The measurements of total systole did not show important differences. In contrast, the initial ejection time (IET), the initial integrated ejection (IIE), the mid-systolic stroke volume (MSV), the mid-systolic ejection fraction (MEF) and the mean mid-systolic ejection rate (MMER) showed significant differences. The CAD group compared with normal subjects, had lower values of IET (P less than 0.05), MSV and MEF (P less than 0.01). The presence of myocardial infarction, the number of arteries with significant obstruction and the elevation of the left ventricular enddiastolic pressure had relationship with decrease in IIE (P less than 0.01) and with amount of MSV, MMER and MSV/end systolic stroke volume ratio (P less than 0.01). On the other hand, patients with angina, specially unstable and in those with ventricular aneurysm, the IIE showed higher values (P less than 0.01) and MSV, MMER, the percentage of mid-systolic ejection fraction and MSV/ESV ratio were lower (P less than 0.01). We conclude that in CAD, the mid-systolic changes are more sensitive than those of the whole systole. In presence of heart failure, the reduced stroke volume is ejected almost totally in the initial period or mid-systole. In patients with ventricular aneurysm or in those with unstable angina is the opposite behavior, the mid-systolic ejection is reduced and the small volume is ejected in the end last period or end systole. These observations could be useful to recognize the damage and the severity of it in CAD.

Psychosis resulting in suicide in a patient with primary hyperparathyroidism

A case is reported of a patient presenting to the psychiatric unit of our hospital with symptoms of depression and found to have an organic psychosis. On routine SMA-12 investigation (12 channel auto analyzer), elevated serum calcium was detected on admission leading to the diagnosis of primary hyperparathyroidism (PHPT). The surgical removal of a parathyroid adenoma was followed by a rapid return of biochemical abnormalities to normal ranges. In spite of appropriate psychiatric management and fluctuations in the patient's clinical condition, the organic psychosis was unaltered and culminated in suicide 4 months after admission.

Value of preexisting bundle branch block in the electrocardiographic differentiation of supraventricular from ventricular origin of wide QRS tachycardia

The relation between the morphologic configuration of QRS complexes during wide QRS tachycardia induced during electrophysiologic studies and sinus rhythm was examined in 18 patients who had preexisting left or right bundle branch block. Representative QRS complexes during sinus rhythm and during tachycardia were isolated from each patient and juxtaposed for comparison. The QRS complexes that constituted each pair were judged by 4 observers as being identical, different or, if the decision was equivocal, similar. Nine patients had supraventricular tachycardia (SVT). In 8 of the 9 patients, all 4 observers found the QRS complexes during sinus rhythm and SVT identical in morphologic configuration. In the other patient, 2 observers found the QRS complexes identical and 2 found them similar. In 12 patients ventricular tachycardia (VT) was induced. In 11 of these 12, all 4 observers found the QRS complexes during VT different from their respective sinus beats. In the other patient, 3 observers found the QRS complexes different, whereas the fourth found them similar. During SVT, the QRS duration was unchanged from the corresponding value during sinus rhythm, whereas in patients with VT, QRS width increased by a mean of 56 +/- 20 ms (p less than 0.001). The results of our study suggest that the electrocardiographic differentiation of wide QRS tachycardia in patients with preexisting bundle branch block can be accomplished easily and accurately by comparing the QRS complexes during tachycardia with those during sinus rhythm: If the complexes are identical, the tachycardia is supraventricular, but if they are different, the arrhythmia is ventricular in origin.

Retrograde concealed conduction in the atrioventricular node: differential manifestations related to level of intranodal penetration

Although concealed conduction in the atrioventricular node (AVN) has been the focus of numerous experimental and clinical studies, little is known about the differential effects on AVN functional behavior of prior concealed retrograde impulse penetration alone vs prior anterograde or dual AVN activation. This study was undertaken specifically to investigate this aspect of human AVN physiology in patients without intact ventriculoatrial conduction to provide a model with which to analyze concealed retrograde AVN conduction. In 13 such patients AVN behavior during a subsequent anterograde input was characterized for each of three different manners of prior AVN activation: anterograde alone (method I), simultaneous anterograde and retrograde excitation (method II), or equivalently timed retrograde concealed AVN penetration alone (method III). In all patients evidence for retrograde AVN concealment was documented by longer anterograde conduction in the AVN during method III than that observed when the retrograde impulse was omitted (method IV). Furthermore, in these patients lacking intact ventriculoatrial conduction, anterograde conduction in the AVN was facilitated and refractoriness was decreased during dual excitation vs anterograde activation alone (method II vs method I). However, when each of methods I and II were compared with concealed retrograde AVN penetration alone (method III), two patterns of AVN responses were observed: In 11 of 13 patients (group A) conduction in the AVN was "worse" and refractoriness was greater both in methods I and II compared with method III; in the remaining two patients (group B) the opposite relationships were observed. The results suggest that among patients with no ventriculoatrial AVN conduction there exist at least two subpopulations whose AVN functional characteristics differ markedly when the effects of anterograde and dual excitation are compared with equivalently timed concealed retrograde activation alone. These findings may be related to differences in level of retrograde AVN concealment in groups A and B, which can be unmasked by the outlined pacing techniques.