Reciprocal Geometric Mean Titer Research Articles

An open, non-randomised, phase 1/2 trial on the safety, tolerability, and immunogenicity of single-dose vaccine "Sputnik Light" for prevention of coronavirus infection in healthy adults.

SummaryBackgroundWhile the world is experiencing another wave of COVID-19 pandemic, global vaccination program is hampered by an evident shortage in the supply of licensed vaccines. In an effort to satisfy vaccine demands we developed a new single-dose vaccine based on recombinant adenovirus type 26 (rAd26) vector carrying the gene for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) glycoprotein – “Sputnik Light”.MethodsWe conducted an open label, prospective, non-randomised phase 1/2 trial aimed to assess safety, tolerability, and immunogenicity of “Sputnik Light” vaccine in a single center in Russia. Primary outcome measures were antigen-specific humoral immunity (Anti-RBD-SARS-CoV-2 antibodies measured by ELISA on days 1, 10, 28, and 42) and safety (number of participants with adverse events monitored throughout the study). Secondary outcome measures were antigen-specific cellular immunity (measured by antigen-dependent CD4+ and CD8+ T-cell proliferation, number of antigen-specific interferon-γ-producing cells as well as interferon-γ concentration upon antigen restimulation) and change in neutralizing antibodies (measured in SARS-CoV-2 neutralization assay).FindingsMost of the solicited adverse reactions were mild (66·4% from all vaccinees), few were moderate (5·5%). No serious adverse events were detected. Assessment of Anti-RBD-SARS-CoV-2 antibodies revealed a group with pre-existing immunity to SARS-CoV-2. Upon this finding we separated all safety and immunogenicity data based on pre-existing immunity to SARS-CoV-2. There were notable differences in the vaccine effects on immunogenicity by the groups. Vaccination of seropositive (N=14) volunteers rapidly boosted RBD-specific IgGs from reciprocal geometric mean titer (​GMT) 594·4 at a baseline up to 26899 comparing to 29·09 in seronegative group (N=96) by day 10. By day 42 seroconversion rate reached 100% (93/93) in seronegative group with GMT 1648. At the same time, in the seropositive group, seroconversion rate by day 42 was 92·9% (13/14) with GMT 19986. Analysis of neutralizing antibodies to SARS-CoV-2 showed 81·7% (76/93) and 92·9% (13/14) seroconversion rates by day 42 with median reciprocal GMT 15·18 and 579·7 in the seronegative and seropositive groups, respectively. Antigen-specific T cell proliferation, formation of IFNy-producing cells, and IFNy secretion were observed in 96·7% (26/27), 96% (24/25), and 96% (24/25) of the seronegative group respectively and in 100% (3/3), 100% (5/5), and 100% (5/5) of the seropositive vaccinees, respectively.InterpretationThe single-dose rAd26 vector-based COVID-19 vaccine “Sputnik Light” has a good safety profile and induces a strong humoral and cellular immune responses both in seronegative and seropositive participants.FundingRussian Direct Investment Fund.

An Open, Non-Randomised, 1/2 Phase Study on the Safety, Tolerability, and Immunogenicity of Single Dose 'Sputnik Light' Vaccine for Prevention of Coronavirus Infection in Healthy Adults

Background: While the world is experiencing another wave of COVID-19 pandemic, global vaccination program is hampered by obvious shortage in supply of licensed vaccines. Development of new vaccines that are easy to manufacture and administer is highly desirable to overcome hurdles in vaccine scaling up and distribution, especially in developing countries. In the effort to satisfy vaccine demands we developed a new single dose vaccine based on recombinant adenovirus type 26 (rAd26) vector carrying the gene for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike glycoprotein – “Sputnik Light”.Methods: We conducted an open label, two-stage, prospective, non-randomized phase I-II trial aimed to assess safety, tolerability and immunogenicity of “Sputnik Light” vaccine in a single center in Russia. Primary outcome measures were antigen-specific humoral immunity (Anti-RBD-SARS-Cov2 antibodies measured by ELISA on days 1, 10, 28, and 42) and safety (number of participants with adverse events monitored throughout the study). Secondary outcome measures were antigen-specific cellular immunity (measured by antigen-dependent CD4+ and CD8+ T-cell proliferation, number of antigen-specific interferon-γ-producing cells as well as interferon-γ concentration upon antigen restimulation) and change in neutralizing antibodies (measured in SARS-CoV-2 neutralization assay). The trial is registered at ClinicalTrials.gov (NCT04713488).Findings: Between January 14 and 27, 2021, 150 participants were screened, of whom 110 were enrolled. Most of solicited adverse reactions were mild (66.4% from all vaccinees), few were moderate (5.5%). No serious adverse events were detected. Assessment of Anti-RBD-SARS-Cov2 antibodies revealed group with pre-existing immunity to SARS-CoV-2. Upon this finding we separated all safety and immunogenicity data according to pre-existing immunity to SARS-Cov2. There were notable differences in the vaccine effects on immunogenicity by the groups. Vaccination of seropositive (N=14) volunteers rapidly boosted RBD-specific IgGs from reciprocal geometric mean titer (​GMT) 594.4 at a baseline up to 26899 comparing to 29.09 in seronegative group (N=96) by day 10. By day 42 seroconversion rate reached 100% (93/93) in seronegative group with GMT 1648. At the same time in seropositive group seroconversion rate by day 42 was 92.9% (13/14) with GMT 19986. Analysis of neutralizing antibodies to SARS-CoV-2 showed 81.7% (76/93) and 92.9% (13/14) seroconversion rates by day 42 with median reciprocal GMT 15.18 and 579.7 in the seronegative and seropositive groups, respectively. Each test to assess cell-mediated immune reactions was carried out on a separate group of 30 volunteers on day 10 upon vaccination. Antigen-specific T cell proliferation, formation of IFNy-producing cells, as well as IFNy secretion were detected in 96.7% (26/27), 96% (24/25) and 96% (24/25) seronegative and in 100% (3/3) 100% (5/5) and 100% (5/5) seropositive vaccinees, correspondingly.Interpretation: The single dose rAd26 vector-based COVID-19 vaccine “Sputnik Light” has a good safety profile and induced strong humoral and cellular immune responses both in seronegative and seropositive participants. Further investigation is needed to assess the effectiveness of this vaccine against COVID-19 used for primary and secondary vaccination.Clinical Trial Registration Details: The trial is registered at ClinicalTrials.gov (NCT04713488).Funding Information: Russian Direct Investment Fund.Declaration of Interests: OVZ, TAO, IVD, OP, DVS, DMG, ASD, AIT, DNS, IBE, EAT, AGB, ASE, FMI, NAN, NLL, ASS, SVB, BSN, DYL, ALG report patents for an immunobiological expression vector, pharmaceutical agent, and its method of use to prevent COVID-19. All other authors declare no competing interests.Ethics Approval Statement: The trial was approved by the local ethic committee and was conducted with the approval of the Ministry of Health of Russian Federation in compliance with International Conference on Harmonization and National Good Clinical Practice guidelines and Declaration of Helsinki.

The Thai Phase III HIV Type 1 Vaccine Trial (RV144) Regimen Induces Antibodies That Target Conserved Regions Within the V2 Loop of gp120

The Thai Phase III clinical trial (RV144) showed modest efficacy in preventing HIV-1 acquisition. Plasma collected from HIV-1-uninfected trial participants completing all injections with ALVAC-HIV (vCP1521) prime and AIDSVAX B/E boost were tested for antibody responses against HIV-1 gp120 envelope (Env). Peptide microarray analysis from six HIV-1 subtypes and group M consensus showed that vaccination induced antibody responses to the second variable (V2) loop of gp120 of multiple subtypes. We further evaluated V2 responses by ELISA and surface plasmon resonance using cyclic (Cyc) and linear V2 loop peptides. Thirty-one of 32 vaccine recipients tested (97%) had antibody responses against Cyc V2 at 2 weeks postimmunization with a reciprocal geometric mean titer (GMT) of 1100 (range: 200-3200). The frequency of detecting plasma V2 antibodies declined to 19% at 28 weeks post-last injection (GMT: 110, range: 100-200). Antibody responses targeted the mid-region of the V2 loop that contains conserved epitopes and has the amino acid sequence KQKVHALFYKLDIVPI (HXB2 Numbering sequence 169-184). Valine at position 172 was critical for antibody binding. The frequency of V3 responses at 2 weeks postimmunization was modest (18/32, 56%) with a GMT of 185 (range: 100-800). In contrast, naturally infected HIV-1 individuals had a lower frequency of antibody responses to V2 (10/20, 50%; p=0.003) and a higher frequency of responses to V3 (19/20, 95%), with GMTs of 400 (range: 100-3200) and 3570 (range: 200-12,800), respectively. RV144 vaccination induced antibodies that targeted a region of the V2 loop that contains conserved epitopes. Early HIV-1 transmission events involve V2 loop interactions, raising the possibility that anti-V2 antibodies in RV144 may have contributed to viral inhibition.

C 6 Test as an Indicator of Therapy Outcome for Patients with Localized or Disseminated Lyme Borreliosis

Management of Lyme disease would benefit from a test to assess therapy outcome. Such a test could be employed to ascertain if treatment of early Lyme disease was successful and would be helpful to clinicians assessing patients with lingering posttreatment symptoms. We reported recently that levels of the antibody to C(6), a Borrelia burgdorferi-derived peptide that is used as an antigen in the C(6)-Lyme diagnostic test, declined after successful antibiotic treatment of Lyme borreliosis patients. We assessed retrospectively the change in anti-C(6) antibody titers in 131 patients with either early localized disease (erythema migrans) or disseminated disease. All of these patients were treated with antibiotics and were free of the clinical signs shown at presentation within 12 weeks after the initiation of treatment. Decreases in reciprocal geometric mean titers (rGMT) of the anti-C(6) antibody were quantified for the subpopulation of 45 patients whose baseline rGMT were >/=80 and whose second serum specimens were obtained at least 6 months after the baseline specimen. Eighty percent of this patient group (36 of 45) experienced a >/=4-fold decrease in their rGMT (P < 0.0003). These results suggest that a change in the anti-C(6) antibody titer may serve as an indicator of therapy outcome for patients with localized or disseminated Lyme borreliosis.

Genetic and antigenic characterization of measles viruses that circulated in Korea during the 2000-2001 epidemic.

Despite the marked reduction in the incidence of measles in Korea by the introduction of measles vaccine, a large measles epidemic occurred during 2000-2001. During the epidemic, more than 55,000 measles cases were reported and at least 7 children were dead. In this study, we analyzed the genetic and antigenic properties of 15 measles viruses that isolated during the epidemic. Sequence analyses of entire hemagglutinin (H) and nucleoprotein (N) genes of the viruses indicated that all Korean isolates had a high degree of homology (>99.8%) when compared with each other. They differed from other wild-type viruses by as much as 6.8% in the H gene and 6.5% in the N gene at the nucleotide level. The deduced amino acid variability was up to 6.4% for the H protein and up to 6.5% for the N protein. Phylogenetic analysis of nucleotide sequences and deduced amino acid sequences of the H and N genes revealed that all Korean viruses were grouped into the genotype H1. This strongly demonstrated that single genotype of measles virus has been circulated in Korea during the 2000-2001 epidemic. Plaque reduction neutralizing antibody titers against vaccine strains, Edmonston and Schwarz, and recently isolated Korean strains were measured using sera from vaccinees and recently infected children. Although sera of recently infected children demonstrated higher neutralizing antibody titers against wild-type strains than against vaccine strains, both sera neutralized both strains and the reciprocal geometric mean titers (GMTs) were not significantly different against both strains.

Differences in surface expression of NspA among Neisseria meningitidis group B strains.

NspA is a highly conserved membrane protein that is reported to elicit protective antibody responses against Neisseria meningitidis serogroups A, B and C in mice (D. Martin, N. Cadieux, J. Hanel, and B. R. Brodeur, J. Exp. Med. 185:1173-1183, 1997). To investigate the vaccine potential of NspA, we produced mouse anti-recombinant NspA (rNspA) antisera, which were used to evaluate the accessibility of NspA epitopes on the surface of different serogroup B strains by an immunofluorescence flow cytometric assay and by susceptibility to antibody-dependent, complement-mediated bacteriolysis. Among 17 genetically diverse strains tested, 11 (65%) were positive for NspA cell surface epitopes and 6 (35%) were negative. All six negative strains also were resistant to bactericidal activity induced by the anti-rNspA antiserum. In contrast, of the 11 NspA surface-positive strains, 8 (73%; P < 0.05) were killed by the antiserum and complement. In infant rats challenged with one of these eight strains, the anti-rNspA antiserum conferred protection against bacteremia, whereas the antiserum failed to protect rats challenged by one of the six NspA cell surface-negative strains. Neither NspA expression nor protein sequence accounted for differences in NspA surface accessibility, since all six negative strains expressed NspA in outer membrane preparations and since their predicted NspA amino acid sequences were 99 to 100% identical to those of three representative positive strains. However, the six NspA cell surface-negative strains produced, on average, larger amounts of group B polysaccharide than did the 11 positive strains (reciprocal geometric mean titers, 676 and 224, respectively; P < 0.05), which suggests that the capsule may limit the accessibility of NspA surface epitopes. Given these strain differences in NspA surface accessibility, an rNspA-based meningococcal B vaccine may have to be supplemented by additional antigens.

Attenuated live cholera vaccine strain CVD 103-HgR elicits significantly higher serum vibriocidal antibody titers in persons of blood group O

Persons of blood group O are at increased risk of developing cholera gravis. In a randomized, placebo-controlled, double-blind safety-immunogenicity trial of live oral cholera vaccine CVD 103-HgR in 5- to 9-year-old Chilean children, vibriocidal antibody seroconversion (74% overall) did not differ by blood group. However, the reciprocal geometric mean titer (GMT) in blood group O vaccines (GMT = 486) was higher than that in non-O vaccines (GMT = 179) (P < 0.02).

Measles Vaccine Immunogenicity in 6- Versus 15-Month-Old Infants Born to Mothers in the Measles Vaccine Era

The low titer of measles antibody in infants of mothers with vaccine-induced immunity may allow immunization against measles before 15 months of age. Six- and 15-month-old infants born to mothers < or = 30 years of age with no history of measles were recruited. Infants enrolled at 6 months of age were immunized with monovalent measles vaccine (Attenuvax), and maternal serum and infant pre- and postvaccination sera were obtained. Those enrolled for primary vaccination at 15 months of age received either Attenuvax (N = 12) or M-M-RII (N = 3). Six-month-old infants were revaccinated with M-M-RII at 15 months of age; pre- and postrevaccination sera were again obtained. Three antibody assays were used: a measles neutralizing assay (NT) and two enzyme immunoassays (EIA) for measles IgG and measles IgM. Among primary vaccinees, 14 of 19 infants aged 6 months (74%) developed NT antibody, as did 15 of 15 infants aged 15 months (100%). The reciprocal geometric mean titer of 6-month-old seroresponders was 23.3, significantly lower than that of the 15-month-old primary vaccinees (87.7, P < .001). Primary seroconversion rates by EIA were 53% for 6-month-old infants and 100% for those aged 15 months. Revaccination of infants who had received Attenuvax at 6 months of age resulted in 100% NT positivity; the geometric mean titer rose to equal that of the group given primary immunization at 15 months of age. Measles IgM antibody was detected in 10 of 14 infants tested 1 month after primary vaccination at 15 months, but was not detected in any of the revaccinated infants after the second dose at 15 months of age (P < .001). 1) Immunization with measles vaccine in infants born to vaccine-immune mothers at 6 months of age induced NT antibody in 74% of infants. 2) Revaccination of prior 6-month-old vaccinees at 15 months resulted in antibody titers equivalent to 15-month-old vaccinees. 3) Lack of an IgM response following revaccination suggests that even seronegative infants may be primed to respond on re-exposure to measles.

Naturally occurring antibodies to an epitope on Plasmodium falciparum gametes detected by monoclonal antibody-based competitive enzyme-linked immunosorbent assay

The antibody response to an epitope on gamete antigens of Plasmodium falciparum in persons naturally exposed to malaria has been investigated by competitive enzyme-linked immunosorbent assay. The assay detects antibodies to an epitope on the 48/45-kilodalton (kDa) gamete surface antigen by competition with horseradish peroxidase-labeled monoclonal antibody IIC5-B10. Five sera previously shown to immunoprecipitate the 230- and 48/45-kDa antigens significantly inhibited IIC5-B10 binding to an average of 24.2% of control. The one serum which precipitated only the 48/45-kDa antigen did not inhibit IIC5-B10 binding. For 26 sera which were negative by immunoprecipitation, mean binding in the assay was 112.7% of control (pooled London nonimmune sera). Recognition of both 230-kDa and 48/45-kDa antigens was associated with a titer of 1:9 or greater (reciprocal geometric mean titer, 27.6) for inhibition to more than 2 standard deviations from the mean of the negative sera. The results show that the IIC5-B10 binding site is a naturally immunogenic epitope recognized by the majority of persons who had antibodies to the 48/45-kDa protein. An additional finding was enhancement of binding of IIC5-B10 to an average of 154.4% of control by five sera which recognized only the 230-kDa antigen, presumably due to conformational alteration of the gamete antigen complex.

Age-Related Prevalence of Human Serum IgG and IgM Antibody to the Core Glycolipid of Escherichia coli strain J5, as Measured by ELISA

Administration of antibody to Escherichia coli strain J5 reduces mortality in patients with gram-negative septic shock. Limited evidence suggests that this antibody is present in the serum of healthy individuals and deficient in persons with malignancy; however, the age-related prevalence of serum antibody to strain J5 in normal subjects is unknown. We developed an ELISA method to measure IgG and IgM antibody to purified J5 lipopolysaccharide (LPS) in sera from 33 maternal-newborn cord pairs, 40 neonates, and 253 individuals aged from one day to twenty years. Reciprocal geometric mean titers for serum antibody to strain J5 LPS were as follows: maternal-IgG, 12.3; IgM, 174; one month old or less-IgG, 8.3; IgM, 5.6; one to 24 months old-IgG, 10.5; IgM, 44.7; greater than 24 months old -IgG, 16.2; IgM, 200. We conclude that human serum antibody to J5 LPS is predominantly IgM and that it is usually present by two years of age. The ELISA method should provide a valuable tool in studying the relation of core glycolipid antibody to immunity and therapy of gram-negative bacterial infections.

Antibodies to Epstein-Barr virus-specific antigens in patients with hairy-cell leukemia.

Antibody titers to Epstein-Barr virus (EBV)-specific antigens of 19 patients with hairy-cell leukemia (HCL) were markedly elevated. All patients showed high titers of IgG anti-viral capsid antigen (VCA) reactivity equal to or greater than 320 (reciprocal titer). The anti-VCA reciprocal geometric mean titer (GTM) was 1106 in contrast to a GMT of 80 for healthy controls (p less than 0.001). No IgM anti-VCA antibody was detected, but three patients had IgA anti-VCA antibodies. Fourteen patients had elevated anti-early antigen (EA) titers (GMT = 177) which were indicative of active infections with EBV. Seven of the 14 patients demonstrated the diffuse component antibody of the early antigen (EA) complex at a GMT of 98. Anti-Epstein-Barr virus nuclear antigen (EBNA) was detected in sera of 16 patients (GMT = 64, controls GMT = 79). It is noteworthy that three patients with anti-VCA titers lacked anti-EBNA titers. These anti-body responses suggest that immunodeficiency secondary to HCL allowed reactivation of the virus.