Differential cytokine and antibody responses to adult and larval stages of Onchocerca volvulus consistent with the development of concomitant immunity.

The possibility of concomitant immunity and its potential mechanisms in Onchocerca volvulus infection were examined by analyzing cytokine and antibody responses to infective larval (third-stage larvae [L3] and molting L3 [mL3]), adult female worm (F-OvAg), and skin microfilaria (Smf) antigens in infected individuals in a region of hyperendemicity in Cameroon as a function of age. Peripheral blood mononuclear cell interleukin 5 (IL-5) responses to F-OvAg and Smf declined significantly with age (equivalent to years of exposure to O. volvulus). In contrast, IL-5 secretion in response to L3 and mL3 remained elevated with increasing age. Gamma interferon responses to L3, mL3, and F-OvAg were low or suppressed and unrelated to age, except for responses to Smf in older subjects. IL-10 levels were uniformly elevated, regardless of age, in response to L3, mL3, and F-OvAg but not to Smf, for which levels declined with age. A total of 49 to 60% of subjects had granulocyte-macrophage colony-stimulating factor responses to all O. volvulus antigens unrelated to age. Analysis of levels of stage-specific immunoglobulin G3 (IgG3) and IgE revealed a striking, age-dependent dissociation between antibody responses to larval antigens (L3 and a recombinant L3-specific protein, O. volvulus ALT-1) which were significantly increased or maintained with age and antibody responses to F-OvAg, which decreased. Levels of IgG1 to L3 and F-OvAg were elevated regardless of age, and levels of IgG4 increased significantly with age, although not to O. volvulus ALT-1, which may have unique L3-specific epitopes. Immunofluorescence staining of whole larvae showed that total anti-L3 immunoglobulin levels also increased with the age of the serum donor. The separate and distinct cytokine and antibody responses to adult and infective larval stages of O. volvulus which are age related are consistent with the acquisition of concomitant immunity in infected individuals.

A common founder for the 35delG GJB2 gene mutation in connexin 26 hearing impairment.

Fifty to eighty percent of autosomal recessive congenital severe to profound hearing impairment result from mutations in a single gene, GJB2, that encodes the protein connexin 26. One mutation of this gene, the 35delG allele, is particularly common in white populations. We report evidence that the high frequency of this allelic variant is the result of a founder effect rather than a mutational hot spot in GJB2, which was the prevailing hypothesis. Patients homozygous for the 35delG mutation and normal hearing controls originating from Belgium, the UK, and the USA were genotyped for different single nucleotide polymorphisms (SNPs). Four SNPs mapped in the immediate vicinity of GJB2, while two were positioned up to 76 kb from it. Significant differences between the genotypes of patients and controls for the five SNPs closest to GJB2 were found, with nearly complete association of one SNP allele with the 35delG mutation. For the most remote SNP, we could not detect any association. We conclude that the 35delG mutation is derived from a common, albeit ancient founder.

Autosomal dominant inherited hearing impairment caused by a missense mutation in COL11A2 (DFNA13).

OBJECTIVE: To analyze the phenotype in a 5-generation DFNA13 family with a missense mutation in the COL11A2 gene that causes autosomal dominant, presumably prelingual, nonsyndromic sensorineural hearing impairment. DESIGN: Family study. SETTING: University hospital department. PATIENTS: Twenty mutation carriers from a large American kindred. METHODS: Cross-sectional analysis using pure-tone threshold measurements at 0.25, 0.5, 1, 2, 4, and 8 kHz. The audiometric configuration was evaluated according to an existing consensus protocol. The significance of features relating to audiometric configuration was tested using 1-way analysis of variance. Progression was evaluated with linear regression analyses of threshold-on-age. RESULTS: Most individuals showed midfrequency (U-shaped) characteristics. The mean threshold in generations IV and V was 44 dB at 1, 2, and 4 kHz (midfrequencies); it was 29 dB at the other frequencies (0.25, 0.5, and 8 kHz). There was no significant progression beyond presbyacusis. CONCLUSION: The trait in this family can be characterized as autosomal dominant, nonprogressive, presumably prelingual, midfrequency sensorineural hearing impairment.

Mutations in COL11A2 cause non-syndromic hearing loss (DFNA13).

We report that mutation of COL11A2 causes deafness previously mapped to the DFNA13 locus on chromosome 6p. We found two families (one American and one Dutch) with autosomal dominant, non-syndromic hearing loss to have mutations in COL11A2 that are predicted to affect the triple-helix domain of the collagen protein. In both families, deafness is non-progressive and predominantly affects middle frequencies. Mice with a targeted disruption of Col11a2 also were shown to have hearing loss. Electron microscopy of the tectorial membrane of these mice revealed loss of organization of the collagen fibrils. Our findings revealed a unique ultrastructural malformation of inner-ear architecture associated with non-syndromic hearing loss, and suggest that tectorial membrane abnormalities may be one aetiology of sensorineural hearing loss primarily affecting the mid-frequencies.

Presymptomatic diagnosis of nonsyndromic hearing loss by genotyping.

BACKGROUND: Nonsyndromic hearing loss (NSHL) is the most common type of hereditary hearing impairment (HHI). It is genetically heterogeneous, and although the exact number of genes is not known, 38 loci have been identified. By cloning the relevant genes and studying the function of the encoded proteins at the molecular level, it may be possible to impact the habitation of persons at risk for HHI. Currently, for select families, presymptomatic diagnosis of NSHL by genotyping is possible. OBJECTIVE: To provide presymptomatic diagnosis of HHI to individuals in select families who have participated in linkage studies. DESIGN: In 2 large families with autosomal dominant HHI, genes for NSHL were mapped to chromosomes 6 (DFNA10) and 19 (DFNA4). In each family, the phenotype is one of progressive sensorineural hearing loss that begins in the individual's mid-30s and progresses to a severe-to-profound loss requiring amplification. Presymptomatic diagnosis was requested by, and provided to, 19 at-risk persons in these kindreds. RESULTS: By reconstructing haplotypes through the use of short tandem repeat polymorphisms tightly linked to the disease gene, risk calculations and genetic counseling were provided to these persons. CONCLUSIONS: By simple Mendelian genetics, the risk of inheriting a fully penetrant autosomal dominant NSHL gene from a single affected parent is 50% for each offspring. However, by reconstructing haplotypes in families in which an HHI gene has been localized, this risk can be changed substantially.