Efficacy of motavizumab for the prevention of respiratory syncytial virus disease in healthy Native American infants: a phase 3 randomised double-blind placebo-controlled trial.

BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections in children. We aimed to assess the safety and efficacy of an anti-RSV monoclonal antibody (motavizumab) in healthy term (≥36 weeks' gestational age) infants for the prevention of medically attended RSV acute lower respiratory tract infections. METHODS: This phase 3, double-blind, placebo-controlled, randomised trial enrolled healthy Native American infants aged 6 months or younger who were born at 36 weeks' gestational age in southwestern USA, on the Navajo Nation, the White Mountain Apache reservation, and the San Carlos Apache Indian reservation. Participants were randomly assigned (2:1) to receive either five monthly intramuscular doses of motavizumab (15 mg/kg) or placebo. They were followed up for 150 days after the first dose, and the primary endpoints were respiratory admission to hospital with a positive result for RSV by RT-PCR and death caused by RSV. Participants were followed up for medically attended wheezing until they reached age 3 years. Analysis was by intention to treat (ITT). This trial is registered with ClinicalTrials.gov, number NCT00121108. FINDINGS: During the autumn seasons (October to December) between 2004 and 2007, 2127 infants of the 2596 infants enrolled were randomly assigned to receive either motavizumab (1417) or placebo (710). After ITT analysis, motavizumab resulted in an 87% relative reduction (relative risk [RR] 0·13, 95% CI 0·08-0·21) in the proportion of infants admitted to hospital with RSV (21 [2%] of 1417 participants who received motavizumab; 80 [11%] of 710 participants who received placebo, p<0·0001). Serious adverse events were less common in particpants taking motavizumab (212 [15%]) than particpants on placebo (148 [21%]). Six deaths occurred in study participants (motavizumab, n=4 [0·3%]; placebo, n=2 [0·3%]); none were deemed to be related to the study product. Hypersensitivity events were more common in patients given motavizumab (208 [14·7%]) than in placebo recipients (87 [12·3%]; p=0·14). There was no effect on rates of medically attended wheezing in children aged 1-3 years (190 [14·9%] of participants randomly assigned to receive motavizumab vs 90 [14·0%] participants randomly assigned to receive placebo). INTERPRETATION: To our knowledge, this is the only trial of an anti-RSV antibody to prevent serious RSV disease in healthy term infants. Motavizumab significantly reduced the RSV-associated inpatient and outpatient burden and set a benchmark for the efficacy of RSV prevention strategies. The findings do not support a direct, generalisable, causal association between RSV lower respiratory tract infection and subsequent long-term wheezing in term infants. FUNDING: MedImmune.

Randomized, Double-Blind Study of the Pharmacokinetics and Safety of Palivizumab Liquid Formulation Compared with Lyophilized Formulation.

OBJECTIVE: To assess the pharmacokinetics and safety of liquid palivizumab compared with lyophilized palivizumab. METHODS: This phase 2, randomized, double-blind crossover study included premature infants aged ≤6 months born ≤35 weeks gestational age. Patients were randomized in a 1:1 ratio to receive a single 15 mg/kg intramuscular dose of liquid (sequence A group) or lyophilized (sequence B group) palivizumab on Day 0. Patients crossed over to receive the alternate formulation on Day 30. Serum palivizumab and antidrug antibody (ADA) levels were measured on Day 0 (predose), Day 30 (before the dose of alternate formulation), and Day 60 (30 days after the dose of alternate formulation). Patients were followed for safety through Day 60 (30 days after the dose of alternate formulation). RESULTS: A total of 153 infants were randomized into the study (sequence A 75; sequence B 78). Sequence A and sequence B trough serum palivizumab levels were similar on Day 30 (51.7 and 49.1 µg/mL, respectively) and Day 60 (84.8 and 87.2 µg/mL, respectively). The ratio of the geometric means using both Day 30 and Day 60 serum concentrations was 1.040 (90% CI 0.998-1.083), which was within the prespecified bioequivalence range of 0.8-1.25. Adverse events (AEs) were similar between the palivizumab liquid and lyophilized groups and within each treatment sequence. Serious AEs (SAEs) were experienced by 3% of infants in both liquid palivizumab and lyophilized palivizumab groups. None of the SAEs were determined to be related to study drug. Among the 124 infants (81% of total) evaluated for ADA, 2 (1.6%) tested positive for ADA at Day 60 (1 in each of sequence A and B). CONCLUSION: Liquid and lyophilized formulations of palivizumab were bioequivalent with similar safety profiles in infants.

Motavizumab treatment of infants hospitalized with respiratory syncytial virus infection does not decrease viral load or severity of illness.

BACKGROUND: This study was conducted to determine whether treatment with motavizumab, an anti-respiratory syncytial virus (RSV) monoclonal antibody, would decrease viral load and improve clinical outcomes in previously healthy term infants hospitalized with RSV lower respiratory tract infection. METHODS: Infants hospitalized with lower respiratory tract infection and a positive RSV test performed locally were randomized to receive 1 intravenous dose of motavizumab (30 or 100 mg/kg) or placebo. Nasal wash samples were tested by real-time reverse transcriptase polymerase chain reaction at a central laboratory to determine viral load. Clinical data were collected during RSV hospitalization and at 12-month follow up. RESULTS: Of 118 infants, 112 were confirmed RSV positive by real-time reverse transcriptase polymerase chain reaction. In each study group, median (range) RSV load (log10 copies/mL) decreased at a similar rate from baseline to study day 7 [motavizumab 30 mg/kg: 8.35 (2.5-9.5) to 5.03 (2.5-6.8); motavizumab 100 mg/kg: 8.22 (5.5-9.7) to 4.25 (2.5-8.0); placebo: 8.02 (6.7-9.8) to 5.17 (2.5-7.3)]. Median (range) duration of hospitalization was 3.05 (0.8-16.0), 2.99 (1.0-25.0) and 2.88 (0.8-11.7) days for the motavizumab 30 mg/kg, motavizumab 100 mg/kg and placebo groups, respectively. Six (8%) motavizumab and 0 placebo recipients were admitted to the intensive care unit and 4 required mechanical ventilation. The incidence of wheezing episodes during the 12-month follow up was comparable for all 3 groups. CONCLUSIONS: Motavizumab had no appreciable effect on RSV viral load measured in the upper respiratory tract of children hospitalized for RSV lower respiratory tract infection. No differences were observed for duration of hospitalization, severity of illness measures or wheezing episodes during 12-month follow up in children treated with motavizumab or placebo.

A novel investigational Fc-modified humanized monoclonal antibody, motavizumab-YTE, has an extended half-life in healthy adults.

The study objective was to evaluate the pharmacokinetics (PK), antidrug antibody (ADA), and safety of motavizumab-YTE (motavizumab with amino acid substitutions M252Y/S254T/T256E [YTE]), an Fc-modified anti-respiratory syncytial virus (RSV) monoclonal antibody. Healthy adults (n = 31) were randomized to receive a single intravenous (i.v.) dose of motavizumab-YTE or motavizumab (0.3, 3, 15, or 30 mg/kg) and followed for 240 days. Clearance of motavizumab-YTE was significantly lower (71% to 86%) and the half-life (t1/2) was 2- to 4-fold longer than with motavizumab. However, similar peak concentrations and volume-of-distribution values, indicative of similar distribution properties, were seen at all dose levels. The sustained serum concentrations of motavizumab-YTE were fully functional, as shown by RSV neutralizing activity that persisted for 240 days with motavizumab-YTE versus 90 days postdose for motavizumab. Safety and incidence of ADA were comparable between groups. In this first study of an Fc-modified monoclonal antibody in humans, motavizumab-YTE was well tolerated and exhibited an extended half-life of up to 100 days. (This study has been registered at ClinicalTrials.gov under registration no. NCT00578682.).

Population pharmacokinetics of palivizumab, a humanized anti-respiratory syncytial virus monoclonal antibody, in adults and children.

Although it has been on the market for over a decade, confusion remains regarding the pharmacokinetics (PK) and optimal dosing of palivizumab, a humanized IgG1κ monoclonal antibody indicated for the prevention of serious lower respiratory tract disease caused by respiratory syncytial virus (RSV) in pediatric patients at high risk of RSV disease. The objectives of this analysis were to characterize the population PK of palivizumab in adults and children using nonlinear mixed-effect modeling, quantify the effects of individual covariates on variability in palivizumab disposition, and compare palivizumab exposures for various dosing scenarios. Palivizumab PK data from 22 clinical studies were used for model development. The model was developed using a two-stage approach: (i) a 2-compartment model with first-order absorption after intramuscular administration was fitted to adult data, and (ii) the same structural model was fitted to the sparse pediatric data using the NONMEM $PRIOR subroutine, with informative priors obtained from the adult analysis. Body weight and an age descriptor that combines gestational age and postnatal age (PAGE) using an asymptotic-exponential model best described palivizumab clearance in pediatric patients. Palivizumab clearance increased slightly from 10.2 ml/day to 11.9 ml/day as a function of PAGE ranging from 7 to 18 months. Covariate analysis indicated a 20% higher clearance in children with chronic lung disease and in children with antidrug antibody titer values of ≥80. These covariates did not substantially explain interindividual variability. In the label-indicated pediatric population, body weight was the primary demographic factor affecting palivizumab PK. Body weight-based dosing of 15 mg/kg yields similar palivizumab concentrations in children of different gestational and postnatal ages. Simulations demonstrated that there was little difference in palivizumab PK between healthy term and premature infants. Simulations also demonstrated that the 5 monthly palivizumab doses of 15 mg/kg, consistent with the label and studied in two randomized, clinical trials, provided greater and more prolonged palivizumab exposure than did an abbreviated dosing regimen of 3 monthly doses.

Prevalence and Characteristics of Human Metapneumovirus Infection Among Hospitalized Children at High Risk for Severe Lower Respiratory Tract Infection.

BACKGROUND: Human metapneumovirus (HMPV) is a significant cause of respiratory tract infections. Little is known about HMPV in children who are at high risk for lower respiratory tract infection (LRTI). METHODS: To determine the prevalence of HMPV in high-risk children and to identify HMPV risk factors, children ≤24 months with prematurity, chronic lung disease, and/or congenital cardiac disease who were hospitalized with LRTI were prospectively enrolled. Nasopharyngeal aspirates were tested for HMPV, respiratory syncytial virus (RSV), influenza A and B, and parainfluenza types 1-3. Demographics, medical history, and outcomes for those with HMPV and RSV were compared. A multivariate analysis was performed to determine HMPV risk factors. RESULTS: Over 4 years, 1126 eligible children were enrolled. Pathogens were identified in 61% of subjects. HMPV was identified in 9.0%, second to RSV (45%). Coinfection with HMPV and RSV occurred in <1% of subjects. Subjects infected with HMPV were older (8.2 vs 4.0 months, P < .001), were born more prematurely (27 vs 33 weeks, P < .001), and more commonly had chronic lung disease (59.3% vs 21.8%, P < .001) compared with subjects infected with RSV. In a multivariate analysis that compared children infected with HMPV to all others, increasing age and household exposure to children ages 6-12 were associated with an increased risk, whereas birth at older gestational age and exposure to children age >12 were associated with a decreased risk. CONCLUSIONS: HMPV was detected in 9% of high-risk children who were hospitalized with lower respiratory tract disease, representing the second most common virus in this population. Compared with all other subjects (including RSV-infected), subjects infected with HMPV were older but were born more prematurely.

A randomized controlled trial of motavizumab versus palivizumab for the prophylaxis of serious respiratory syncytial virus disease in children with hemodynamically significant congenital heart disease.

Children with hemodynamically significant congenital heart disease (CHD) are at risk for serious respiratory syncytial virus (RSV) disease. This study was designed to assess the safety and tolerability of motavizumab versus palivizumab in children with CHD and was not powered for efficacy. Patients (n = 1236) aged ≤24 mo were randomized to receive five monthly doses (15 mg/kg) of motavizumab or palivizumab during the RSV season. Adverse events (AEs) and serious AEs (SAEs) were recorded through 30 d after the last dose. RSV hospitalizations and RSV outpatient medically attended lower respiratory tract infections (MALRI; season 2) were summarized. Approximately 93 and 50% of patients reported an AE or SAE, respectively. Skin events occurred in 19.3% of motavizumab recipients and 16.2% of palivizumab recipients. Rates of hospitalizations and RSV MALRI were similar between treatment groups [relative risk (RR): 0.75; 95% CI, 0.34-1.59 and RR: 0.49; 95% CI, 0.10-1.99, respectively; both p > 0.05]. Motavizumab and palivizumab had similar safety profiles in children with hemodynamically significantly CHD; with the exception of skin events which were increased in motavizumab recipients. Safety and efficacy were consistent with another study comparing motavizumab with palivizumab in premature infants without CHD.

Analysis of respiratory syncytial virus preclinical and clinical variants resistant to neutralization by monoclonal antibodies palivizumab and/or motavizumab.

BACKGROUND: Palivizumab is a US Food and Drug Administration-approved monoclonal antibody for the prevention of respiratory syncytial virus (RSV) lower respiratory disease in high-risk infants. Motavizumab, derived from palivizumab with enhanced antiviral activity, has recently been tested in humans. Although palivizumab escape mutants have been generated in the laboratory, the development of resistant RSV in patients receiving palivizumab has not been reported previously. METHODS: We generated palivizumab and motavizumab escape mutants in vitro and examined the development of resistant mutants in RSV-breakthrough patients receiving immunoprophylaxis. The effect of these mutations on neutralization by palivizumab and motavizumab and in vitro fitness was studied. RESULTS: Antibody-resistant RSV variants selected in vitro had mutations at position 272 of the fusion protein, from lysine to asparagine, methionine, threonine, glutamine, or glutamate. Variants containing mutations at positions 272 and 275 were detected in breakthrough patients. All these variants were resistant to palivizumab, but only the glutamate variant at position 272 demonstrated resistance to motavizumab. Mixtures of wild-type and variant RSV soon lost the resistant phenotype in the absence of selection. CONCLUSIONS: Resistant RSV variants were detected in a small subset (∼ 5%) of RSV breakthrough cases. The fitness of these variants was impaired, compared to wild-type RSV.

A phase 2, randomized, double-blind safety and pharmacokinetic assessment of respiratory syncytial virus (RSV) prophylaxis with motavizumab and palivizumab administered in the same season.

BACKGROUND: Respiratory syncytial virus (RSV) is an important pathogen causing annual epidemics of bronchiolitis and pneumonia among infants worldwide. High-risk infants currently receive RSV prophylaxis with palivizumab, a humanized RSV monoclonal antibody (MAb). In preclinical in vitro and in vivo (cotton-rat model) studies, motavizumab, a new RSV MAb, was shown to have greater anti-RSV activity than palivizumab. Motavizumab is currently under review for licensing approval. Since both MAbs may be available concurrently, this study evaluated their safety and tolerability when administered sequentially during the same RSV season. METHODS: Between April 2006 and May 2006, 260 high-risk infants were randomly assigned 1:1:1 to receive monthly intramuscular injections: 2 doses of motavizumab followed by 3 doses of palivizumab (M/P); 2 doses of palivizumab followed by 3 doses of motavizumab (P/M); or 5 doses of motavizumab (control). Adverse events (AEs, serious AEs [SAEs]), development of antidrug antibody (ADA), and serum drug trough concentrations were assessed. RESULTS: Most children received all 5 doses (246/260 [94.6%]) and completed the study (241/260 [92.7%]). While overall AE rates were similar (mostly level 1 or 2 in severity), SAEs and level 3 AEs occurred more frequently in the M/P group (SAEs: 22.9% M/P, 8.4% P/M, 11.8% motavizumab only; level 3 AEs: 15.7% M/P, 6.0% P/M, 6.5% motavizumab only). This trend in AE rates occurred before and after switching from motavizumab to palivizumab, suggesting a cause other than the combined regimen. Frequencies of AEs judged by the investigator to be related to study drug were similar among groups. Two deaths occurred on study (both in the M/P group, before palivizumab administration); neither was considered by the site investigator to be related to study drug. Mean serum drug trough concentrations were comparable among groups; ADA detection was infrequent (5.1% or less of any group). CONCLUSIONS: The conclusions drawn from this study are limited by the small sample size per group. However, within this small study, overall AE rates, serum drug trough concentrations, and development of ADA associated with administering motavizumab and palivizumab sequentially to high-risk children appear comparable to administering motavizumab alone during the same RSV season. TRIAL REGISTRATION: clinicaltrials.gov NCT00316264.

Motavizumab for prophylaxis of respiratory syncytial virus in high-risk children: a noninferiority trial.

OBJECTIVE: Palivizumab reduces respiratory syncytial virus (RSV) hospitalization in children at high risk by approximately 50% compared with placebo. We compared the efficacy and safety of motavizumab, an investigational monoclonal antibody with enhanced anti-RSV activity in preclinical studies, with palivizumab. METHODS: This randomized, double-blind, multinational, phase 3, noninferiority trial assessed safety and RSV hospitalization in 6635 preterm infants aged

Safety and antiviral activity of motavizumab, a respiratory syncytial virus (RSV)-specific humanized monoclonal antibody, when administered to RSV-infected children.

Previously healthy children hospitalized with respiratory syncytial virus (RSV) received motavizumab (3, 15, or 30 mg/kg intravenously), an RSV-specific monoclonal antibody, or placebo. Safety, tolerability, motavizumab concentrations, and immunogenicity were assessed. Cultivatable RSV in the upper respiratory tract was significantly reduced with motavizumab compared with placebo day 1 post-treatment. No adverse events were considered motavizumab-related by site investigators.

Phase-I study MEDI-534, of a live, attenuated intranasal vaccine against respiratory syncytial virus and parainfluenza-3 virus in seropositive children.

A live, attenuated respiratory syncytial virus and parainfluenza virus type 3 vaccine was evaluated in healthy respiratory syncytial virus/parainfluenza virus type 3 seropositive children aged 1 to 9 years. Three cohorts of 40 children were randomized 1:1 to receive 10, 10, or 10 median tissue culture infectious dose50 MEDI-534 vaccine or placebo. The vaccine's safety profile was similar to placebo, no viral shedding was detected, and the vaccine was minimally immunogenic.

Safety, tolerability, pharmacokinetics, and immunogenicity of motavizumab, a humanized, enhanced-potency monoclonal antibody for the prevention of respiratory syncytial virus infection in at-risk children.

BACKGROUND: : Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection in young children. Motavizumab is an investigational humanized monoclonal antibody for RSV prophylaxis. METHODS: : A dose-escalation study was conducted followed by assessment of safety, tolerability, serum concentrations, and immunogenicity during a second consecutive RSV season. In season 1, premature infants aged < or =6 months or children < or =24 months with chronic lung disease of prematurity received monthly motavizumab (3 or 15 mg/kg). In season 2, children who received > or =3 motavizumab doses in season 1 were randomized to receive monthly motavizumab or palivizumab 15 mg/kg. RESULTS: : Of 217 children enrolled in season 1, 211 (97.2%) received motavizumab 15 mg/kg and 205 (94.5%) patients completed the study through 90 days after the final dose. In season 2, 136 children were randomized to receive motavizumab (n = 66) or palivizumab (n = 70). The most commonly reported related adverse event was transient injection site erythema. In season 1, mean trough motavizumab concentrations were 7.9 and 50.2 microg/mL after the 3- and 15-mg/kg doses, respectively. Trough concentrations increased with repeated motavizumab dosing; a similar pattern was seen in season 2. Antimotavizumab reactivity occurred infrequently (3.3%) in season 1. In season 2, no treatment group-specific antidrug antibody was detected through 90 to 120 days after dosing with either product. CONCLUSIONS: : The pharmacokinetic profile of motavizumab was similar to that of other IgG1 antibodies. Increased adverse reactions or immunogenicity were not observed during and after a second season of treatment with motavizumab. Safety findings from these studies supported the continued development of motavizumab.

Development of a PIV-vectored RSV vaccine: preclinical evaluation of safety, toxicity, and enhanced disease and initial clinical testing in healthy adults.

MEDI-534 is a bivalent live attenuated vaccine candidate against human respiratory syncytial virus (hRSV) and human parainfluenza virus type 3 (hPIV3) that was previously shown to be immunogenic and to protect rodents and African green monkeys from wild-type (wt) hRSV challenge. We performed further preclinical evaluations to address the safety of MEDI-534 prior to human testing. MEDI-534 did not predispose rodents to enhanced RSV disease following wt-RSV challenge, and the tissue tropism of the chimeric virus was confined to the respiratory tract. Representative clinical trial material did not produce toxicity in rats. In adults, MEDI-534 was highly restricted in replication, did not boost RSV and PIV3 antibody titers, and produced no medically significant vaccine-related adverse events thereby warranting further evaluation in pediatric populations.

Humoral, mucosal, and cellular immune responses to oral Norwalk virus-like particles in volunteers.

Norwalk virus-like particles (VLPs), made from recombinant capsid protein, are a promising vaccine. Thirty-six healthy adult volunteers received 250 microg (n = 10), 500 microg (n = 10), or 2000 microg (n = 10) of orally administered VLP or placebo (n = 6). All vaccinees developed significant rises in IgA anti-VLP antibody-secreting cells. Ninety percent who received 250 microg developed rises in serum anti-VLP IgG; neither the rates of seroconversion nor geometric mean titers increased at the higher doses. About 30-40% of volunteers developed mucosal anti-VLP IgA. Lymphoproliferative responses and IFN-gamma production were observed transiently among those who received 250 microg or 500 microg but not 2000 microg of VLP. Studies to increase immunogenicity using a mucosal adjuvant are planned.

Attenuated Salmonella enterica serovar Typhi and Shigella flexneri 2a strains mucosally deliver DNA vaccines encoding measles virus hemagglutinin, inducing specific immune responses and protection in cotton rats.

Measles remains a leading cause of child mortality in developing countries. Residual maternal measles antibodies and immunologic immaturity dampen immunogenicity of the current vaccine in young infants. Because cotton rat respiratory tract is susceptible to measles virus (MV) replication after intranasal (i.n.) challenge, this model can be used to assess the efficacy of MV vaccines. Pursuing a new measles vaccine strategy that might be effective in young infants, we used attenuated Salmonella enterica serovar Typhi CVD 908-htrA and Shigella flexneri 2a CVD 1208 vaccines to deliver mucosally to cotton rats eukaryotic expression plasmid pGA3-mH and Sindbis virus-based DNA replicon pMSIN-H encoding MV hemagglutinin (H). The initial i.n. dose-response with bacterial vectors alone identified a well-tolerated dosage (1 x 10(9) to 7 x 10(9) CFU) and a volume (20 micro l) that elicited strong antivector immune responses. Animals immunized i.n. on days 0, 28, and 76 with bacterial vectors carrying DNA plasmids encoding MV H or immunized parenterally with these naked DNA vaccine plasmids developed MV plaque reduction neutralizing antibodies and proliferative responses against MV antigens. In a subsequent experiment of identical design, cotton rats were challenged with wild-type MV 1 month after the third dose of vaccine or placebo. MV titers were significantly reduced in lung tissue of animals immunized with MV DNA vaccines delivered either via bacterial live vectors or parenterally. Since attenuated serovar Typhi and S. flexneri can deliver measles DNA vaccines mucosally in cotton rats, inducing measles immune responses (including neutralizing antibodies) and protection, boosting strategies can now be evaluated in animals primed with MV DNA vaccines.

Immune responses elicited against multiple enterotoxigenic Escherichia coli fimbriae and mutant LT expressed in attenuated Shigella vaccine strains.

Shigella and enterotoxigenic Escherichia coli (ETEC) continue to be important causes of diarrheal disease in infants and young children in developing countries and are major etiologic agents of traveler's diarrhea. Since attenuated strains of Shigella have been developed as live oral vaccines against shigellosis, we have adapted these attenuated Shigella strains to serve as carriers of ETEC antigens, thereby constituting a hybrid vaccine. Since protective immunity against ETEC is largely directed against fimbrial antigens (of which there are multiple antigenic types), we have individually expressed four different ETEC fimbriae, including CFA/I, CS2, CS3, and CS4, using deltaguaBA attenuated Shigella vaccine strain CVD 1204 as a prototype live vector. Following mucosal (intranasal) immunization of guinea pigs, serum IgG and mucosal IgA responses were elicited against each fimbrial type. An additional strain was constructed expressing a detoxified version of the human ETEC variant of heat labile toxin (LThK63). Following mucosal immunization of guinea pigs with a mixed inoculum containing five Shigella strains each expressing a different ETEC antigen, immune responses were observed against each ETEC antigen plus the Shigella vector.

B cell responses in gastric antrum and duodenum following oral inactivated Helicobacter pylori whole cell (HWC) vaccine and LT(R192G) in H pylori seronegative individuals.

To investigate whether B cell-specific responses could be elicited in the gastric mucosa of Helicobacter pylori (HP) naive subjects, five volunteers ingested three doses of a HP killed whole cell (HWC) vaccine with 25 microg of recombinant heat-labile toxin (LT(R192G)). Two of three subjects had detectable LT(R192G) and HWC IgA antibody secreting cell (ASC) gastric responses. LT(R192G) and HWC responses in duodenal were 5-14-fold higher than those detected in antral biopsies (P<0.01 and P=0.05, respectively). These results provide the first evidence that specific gastric B cell responses can be induced in HP-non-infected individuals following oral immunization.

Standard and alternative regimens of Haemophilus influenzae type b conjugate vaccine (polyribosylribitol phosphate-tetanus toxoid conjugate vaccine) elicit comparable antibody avidities in infants.

BACKGROUND: Haemophilus influenzae type b conjugate vaccines are relatively expensive in the developing world. Previous study of the type b conjugate vaccine polyribosylribitol phosphate-tetanus toxoid conjugate vaccine showed that two dose and fractional three dose schedules elicit protective antibody concentrations equivalent to three full doses. METHODS: Antibody avidity was measured in 73 of these vaccinees with a modified enzyme-linked immunosorbent assay using NH(4) SCN as the chaotrope. Avidity index (AI) is the molarity causing a 50% reduction in OD(405). RESULTS: The postprimary series AI was similar for all dosing regimens. Preboost AI was highest in those receiving three half-doses, although there was no statistical difference among groups. Rises in avidity from age 8 to 12 months were also similar among regimens. Our data support the equivalence of anti-polyribosylribitol phosphate IgG avidity in infants primed with these alternative regimens. CONCLUSIONS: Given the known correlation of avidity with assays of bacterial killing and memory priming, these potentially more economical alternative schedules should be studied in the developing world.

Phase I evaluation of delta virG Shigella sonnei live, attenuated, oral vaccine strain WRSS1 in healthy adults.

We conducted a phase I trial with healthy adults to evaluate WRSS1, a live, oral Delta virG Shigella sonnei vaccine candidate. In a double-blind, randomized, dose-escalating fashion, inpatient volunteers received a single dose of either placebo (n = 7) or vaccine (n = 27) at 3 x 10(3) CFU (group 1), 3 x 10(4) CFU (group 2), 3 x 10(5) CFU (group 3), or 3 x 10(6) CFU (group 4). The vaccine was generally well tolerated, although a low-grade fever or mild diarrhea occurred in six (22%) of the vaccine recipients. WRSS1 was recovered from the stools of 50 to 100% of the vaccinees in each group. The geometric mean peak anti-lipopolysaccharide responses in groups 1 to 4, respectively, were 99, 39, 278, and 233 for immunoglobulin (IgA) antibody-secreting cell counts; 401, 201, 533, and 284 for serum reciprocal IgG titers; and 25, 3, 489, and 1,092 for fecal IgA reciprocal titers. Postvaccination increases in gamma interferon production in response to Shigella antigens occurred in some volunteers. We conclude that WRSS1 vaccine is remarkably immunogenic in doses ranging from 10(3) to 10(6) CFU but elicits clinical reactions that must be assessed in further volunteer trials.