We have analyzed the GH receptor (GHR) gene in four individuals with Laron syndrome, and a missense mutation was identified for each patient in the extracellular domain of the GHR (D152H, I153T, Q154P, and V155G). The D152H mutation was previously reported. We have reproduced the three novel mutations in the GHR complementary DNA and analyzed their consequences in human 293 transfected cells. In cells expressing the I153T and V155G mutants, binding of [125I]human GH at the cell surface was very low, whereas binding to total membrane fractions was much less affected, suggesting impaired cell surface expression. Binding assays with cells expressing the Q154P mutant revealed severe defects both at the cell surface and in total particulate membrane fractions. Immunofluorescence experiments confirmed that cell surface expression of the three mutants was altered, and colocalization studies suggested that most of the mutant receptors are retained in the endoplasmic reticulum. Endoglycosidase H resistance tests also indicated that the majority of I153T and V155G GHRs are trapped in the endoplasmic reticulum. Thus, mutations on contiguous amino acids of the GHR result in various defects. The I153T, Q154P, and V155G mutations mainly affect intracellular trafficking and binding affinity of the receptor, whereas the D152H mutation affects receptor expression, dimerization, and signaling.
Sixty-eight Saudi children, 17 to 19 months of age, were enrolled in a study to evaluate the safety and immunogenicity of Hemophilus influenzae type B capsular polysaccharide diphtheria toxoid (PRP-D) conjugate vaccine. Adverse reactions to the vaccine were determined through a questionnaire administered to the parents. Local and systemic reactions to the vaccine were mild and resolved within 24 to 48 hours. PRP antibody levels were measured prior to and one to two months following immunization. PRP antibody levels in the pre-immunization sera of 77% of subjects were below the level associated with immediate protection (>/=0.15 microg/ml), and 88% were below the level associated with long-term protection (>/=1 microg/ml) from Hemophilus influenzae type B (HIB) disease. After one dose of PRP-D vaccine, 100% of recipients achieved antibody levels of >/=0.15 microg/ml, and 85% achieved levels of >/=1 microg/ml. The geometric mean level of antibody after immunization (5.66 microg/ml) was significantly higher than that before immunization (0.098 microg/ml). All subjects had a twofold or greater increase in antibody level in response to the vaccine. We conclude that PRP-D is a safe and highly immunogenic vaccine in this age group of Saudi children.
