A double-blind, randomized, controlled, multi-center safety and immunogenicity study of a refrigerator-stable formulation of VARIVAX®.

OBJECTIVE: VARIVAX® (varicella virus vaccine, live Oka/Merck, Merck & Co., Inc., Kenilworth, NJ, USA) was originally licensed as a frozen formulation. A refrigerator-stable formulation of VARIVAX was subsequently developed to allow for increased availability of the product around the world. The objective of this study (V210-051) was to demonstrate that the safety, tolerability and immunogenicity profile of the refrigerator-stable formulation of VARIVAX was similar to the frozen formulation. METHODS: In this double-blind, randomized, multicenter study, healthy 12- to 23-month-old children with negative vaccination and clinical histories for measles, mumps, rubella, varicella, and zoster were vaccinated with either a refrigerator-stable formulation of VARIVAX (at two dosage levels; 8000 PFU [N = 320] or 25,000 PFU [N = 315]) or the frozen formulation of VARIVAX (10,000 PFU, N = 323) given concomitantly with M-M-RII® (measles, mumps, and rubella virus vaccine live, Merck & Co., Inc., Kenilworth, NJ, USA). Children were followed for 42 days after vaccination for adverse experiences. Immunogenicity was evaluated 6 weeks after vaccination. RESULTS: The refrigerator-stable formulation of VARIVAX was generally well tolerated. The incidence of adverse experiences was similar between all three groups. No vaccine-related serious adverse experiences were reported with any of the vaccine formulations. The immune response (percentage of subjects with varicella antibody titers ≥5 gpELISA units) for both refrigerator-stable formulations of VARIVAX at 6 weeks postvaccination was similar to that of the frozen formulation. Administration of either refrigerator-stable formulation of VARIVAX with M-M-RII yielded seroconversion rates and GMTs for measles, mumps and rubella that were comparable to those achieved after administration of the frozen formulation of VARIVAX with M-M-RII. CONCLUSION: The safety, tolerability, and immunogenicity profile of the refrigerator-stable varicella vaccine was similar to that of the frozen formulation.

Novel mutations in the TK2 gene associated with fatal mitochondrial DNA depletion myopathy.

Mitochondrial DNA depletion syndromes are a heterogeneous group of childhood neurological disorders characterised by a quantitative abnormality of mitochondrial DNA. We describe two siblings who presented at 8 months and 14 months with myopathy, which rapidly progressed and resulted in death by respiratory failure at age 14 and 18 months, respectively. Muscle biopsy revealed marked respiratory chain defects, with real-time PCR confirming a dramatic depletion of mitochondrial DNA. Sequencing of the thymidine kinase 2 (TK2) gene revealed two, novel heterozygous mutations (p.Q87X and p.N100S) with parental DNA analysis confirming the transmission of mutated alleles.

Endurance training and detraining in mitochondrial myopathies due to single large-scale mtDNA deletions.

At present there are limited therapeutic interventions for patients with mitochondrial myopathies. Exercise training has been suggested as an approach to improve physical capacity and quality of life but it is uncertain whether it offers a safe and effective treatment for patients with heteroplasmic mitochondrial DNA (mtDNA) mutations. The objectives of this study were to assess the effects of exercise training and detraining in eight patients with single, large-scale mtDNA deletions to determine: (i) the efficacy and safety of endurance training (14 weeks) in this patient population; (ii) to determine the effect of more prolonged (total of 28 weeks) exercise training upon muscle and cardiovascular function and (iii) to evaluate the effect of discontinued training (14 weeks) upon muscle and cardiovascular function. Our results show that: (i) 14 weeks of exercise training significantly improved tolerance of submaximal exercise and peak capacity for work, oxygen utilization and skeletal muscle oxygen extraction with no change in the level of deleted mtDNA; (ii) continued training for an additional 14 weeks maintained these beneficial adaptations; (iii) the cessation of training (detraining) resulted in loss of physiological adaptation to baseline capacity with no overall change in mutation load. Patients' self assessment of quality of life as measured by the SF-36 questionnaire improved with training and declined with detraining. Whilst our findings of beneficial effects of training on physiological outcome and quality of life without increases in the percentage of deleted mtDNA are encouraging, we did not observe changes in mtDNA copy number. Therefore there remains a need for longer term studies to confirm that endurance exercise is a safe and effective treatment for patients with mitochondrial myopathies. The effects of detraining clearly implicate physical inactivity as an important mechanism in reducing exercise capacity and quality of life in patients with mitochondrial myopathy.

Experimental strategies towards treating mitochondrial DNA disorders.

An extensive range of molecular defects have been identified in the human mitochondrial genome (mtDNA), causing a range of clinical phenotypes characterized by mitochondrial respiratory chain dysfunction. Sadly, given the complexities of mitochondrial genetics, there are no available cures for mtDNA disorders. In this review, we consider experimental, genetic-based strategies that have been or are being explored towards developing treatments, focussing on two specific areas which we are actively pursuing--assessing the benefit of exercise training for patients with mtDNA defects, and the prevention of mtDNA disease transmission.

Analysis of safety data in children after receiving two doses of ProQuad® (MMRV).

BACKGROUND: In randomized clinical studies, over 11,800 children, 12 months to 6 years of age, were administered ProQuad(®), a combination measles, mumps, rubella, and varicella vaccine (MMRV). This paper describes the safety following a 2-dose regimen of MMRV administered to children in the second year of life. METHODS: Safety data from five clinical studies were combined for all children who were scheduled to receive two doses of MMRV ∼3-6 months apart. All vaccinated children were followed for safety following each dose of MMRV. RESULTS: Of 3112 children who received a first dose of MMRV, 2780 (89.3%) received a second dose of MMRV. Overall, 70.5% and 57.7% of children reported ≥1 adverse experiences following first and second doses of MMRV, respectively. Injection-site redness was statistically significantly higher postdose 2 than postdose 1, while injection-site pain/tenderness was statistically significantly higher postdose 1 compared to postdose 2. Rashes were statistically significantly lower postdose 2 compared to postdose 1. Ten febrile seizures (8 postdose 1, 2 postdose 2) were reported following MMRV vaccination. The incidence of febrile seizures postdose 1 of MMRV was 0.26% (8/3019) compared to 0.07% (2/2695) postdose 2 of MMRV. CONCLUSIONS: Administration of two doses of MMRV has an acceptable safety profile in children 12 to 23 months of age. There is a small increase in the risk of febrile seizures following the first dose of MMRV as compared to the component vaccines, but the risk for any individual child is relatively low.

Immunogenicity and safety of MMRV and PCV-7 administered concomitantly in healthy children.

OBJECTIVE: We assessed the immunogenicity and safety of a combination measles, mump, rubella, and varicella vaccine (MMRV) (ProQuad [Merck & Co, Inc, West Point, PA]) administered to healthy children concomitantly with a pneumococcal 7-valent conjugate vaccine (PCV-7) (Prevnar [Pfizer, Philadelphia, PA]). PATIENTS AND METHODS: Healthy 12- to 15-month-old children who lacked vaccination and clinical histories for measles, mumps, rubella, varicella, and zoster but had written documentation of receipt of a 3-dose primary series of PCV-7 were randomly assigned in a 2:1:1 ratio to receive either the MMRV and PCV-7 (group 1), PCV-7 followed 6 weeks later by MMRV (group 2), or MMRV followed 6 weeks later by PCV-7 (group 3). The primary safety analysis was 56 days (28 days after each visit). Immunogenicity was evaluated 6 weeks after each vaccination. RESULTS: A total of 1027 children were enrolled (group 1: 510; group 2: 258; group 3: 259). For all 3 groups, the antibody response rate was ≥96.8% for measles, mumps, and rubella, ≥88.0% for varicella-zoster virus, and ≥98.3% for all of the 7 Streptococcus pneumoniae serotypes. The immune responses to all antigens present in MMRV and PCV-7 were similar whether administered concomitantly or sequentially. The incidence of local and systemic adverse experiences (AEs) was comparable between group 1 and groups 2 and 3 combined. No vaccine-related serious AEs were reported. CONCLUSIONS: Concomitant administration of the MMRV and PCV-7 is highly immunogenic and generally well tolerated. Similar immune responses between the groups support concomitant administration of the MMRV and PCV-7 to healthy children 12 to 15 months of age.

Familial myopathy: new insights into the T14709C mitochondrial tRNA mutation.

We have defined the genetic defect in a large family first described in one of the earliest reports of suspected mitochondrial myopathy, as the mutation T14709C in the mitochondrial transfer RNA(Glu) (mt-tRNA(Glu)) gene. Extraordinarily, this mutation has attained homoplasmy (100% mutated mt-tRNA(Glu)) on at least three independent occasions in this family and has done so in one individual who remains asymptomatic with no clinical evidence of disease. Heteroplasmy (dual populations of mutated and wild-type mtDNA) usually is regarded as one of the primary diagnostic criteria for pathogenicity and previous reports of the T14709C mutation detail heteroplasmy in a variety of tissues. In contrast, homoplasmy of mt-tRNA mutations generally has been regarded as evidence of a benign nature, with rare exceptions that result in organ-specific phenotypes. Discovering that T14709C, a common and severe mt-tRNA mutation, can attain homoplasmy without symptoms or clinical signs of disease has profound implications for the identification and prevalence of other pathogenic mt-tRNA mutations. Furthermore, variation in phenotype between homoplasmic individuals implies a crucial contribution from the nuclear genetic environment in determining the clinical outcome of mt-tRNA mutations.