Development, clinical evaluation, and post-licensure impact of RotaTeq, a pentavalent rotavirus vaccine.

Rotavirus gastroenteritis (RVGE) is the leading cause of severe diarrhea in children worldwide. This paper provides an overview of the development, clinical evaluation, and postlicensure impact of RotaTeq™(Rotavirus Vaccine, Live, Oral, Pentavalent, Merck & Co., Inc.). RotaTeq, an oral vaccine, is uniquely designed to contain five human-bovine reassortant rotavirus strains expressing the human serotypes G1, G2, G3, G4, and P1A[8], which represent the most common human rotavirus serotypes responsible for ∼85% of RVGE worldwide. The development required novel solutions for manufacturing, testing, and formulation for each of the reassortants. In one of the largest vaccine clinical trials conducted, the vaccine was shown to be well tolerated and highly efficacious against severe RVGE. Efficacy has also been demonstrated in lower-income countries. In large U.S. postlicensure studies, there have been no safety signals identified, and RotaTeq has had a significant impact on reducing RVGE and its associated medical costs since licensure in 2006.

Tissue assembly guided via substrate biophysics: applications to hepatocellular engineering.

The biophysical nature of the cellular microenvironment, in combination with its biochemical properties, can critically modulate the outcome of three-dimensional (3-D) multicellular morphogenesis. This phenomenon is particularly relevant for the design of materials suitable for supporting hepatocellular cultures, where cellular morphology is known to be intimately linked to the functional output of the cells. This review summarizes recent work describing biophysical regulation of hepatocellular morphogenesis and function and focuses on the manner by which biochemical cues can concomitantly augment this responsiveness. In particular, two distinct design parameters of the substrate biophysics are examined--microtopography and mechanical compliance. Substrate microtopography, introduced in the form of increasing pore size on collagen sponges and poly(glycolic acid) (PGLA) foams, was demonstrated to restrict the evolution of cellular morphogenesis to two dimensions (subcellular and cellular void sizes) or induce 3-D cellular assembly (supercellular void size). These patterns of morphogenesis were additionally governed by the biochemical nature of the substrate and were highly correlated to resultant levels of cell function. Substrate mechanical compliance, introduced via increased chemical crosslinking of the basement membrane, Matrigel, and polyacrylamide gel substrates, also was shown to be able to induce active two-dimensional (2-D, rigid substrates) or 3-D (malleable substrates) cellular reorganization. The extent of morphogenesis and the ensuing levels of cell function were highly dependent on the biochemical nature of the cellular microenvironment, including the presence of increasing extracellular matrix (ECM) ligand and growth-factor concentrations. Collectively, these studies highlight not only the ability of substrate biophysics to control hepatocellular morphogenesis but also the ability of biochemical cues to further enhance these effects. In particular, results of these studies reveal novel means by which hepatocellular morphogenesis and assembly can be rationally manipulated leading to the strategic control of the expression of liver-specific functions for hepatic tissue-engineering applications.

Fluid mechanics, cell distribution, and environment in CellCube bioreactors.

Cultivation of MRC-5 cells and attenuated hepatitis A virus (HAV) for the production of VAQTA, an inactivated HAV vaccine (1), is performed in the CellCube reactor, a laminar flow fixed-bed bioreactor with an unusual diamond-shaped, diverging-converging flow geometry. These disposable bioreactors have found some popularity for the production of cells and gene therapy vectors at intermediate scales of operation (2, 3). Early testing of the CellCube revealed that the fluid mechanical environment played a significant role in nonuniform cell distribution patterns generated during the cell growth phase. Specifically, the reactor geometry and manufacturing artifacts, in combination with certain inoculum practices and circulation flow rates, can create cell growth behavior that is not simply explained. Via experimentation and computational fluid dynamics simulations we can account for practically all of the observed cell growth behavior, which appears to be due to a complex mixture of flow distribution, particle deposition under gravity, fluid shear, and possibly nutritional microenvironment.