Identification of a single MPV17 nonsense-associated altered splice variant in 24 South African infants with mitochondrial neurohepatopathy.

MPV17-related mitochondrial neurohepatopathy is a rare genetic disorder worldwide. We report on a novel pathogenic variant in the MPV17 gene in 24 unrelated neurohepatopathic infants of non-consanguineous Black South African heritage. Exome sequencing identified homozygosity for a c.106C>T nonsense variant in exon 3 of the human MPV17 gene in 2 unrelated index patients. mRNA analysis revealed transcripts both with and without exon 3, indicating both reduced splice efficiency and premature termination as mechanisms for disease. Carrier frequency in this population was found to be 1 in 68 (95% CI; 1/122-1/38) with an estimated newborn incidence of 1 in 18 496 (95% CI; 1/59 536-1/5776). Affected infants all presented with infantile onset neurohepatopathy with none surviving beyond infancy. This description of a relatively common pathogenic variant underlying a previously uncharacterized severe neurohepatopathy in South Africa will engender increased awareness, earlier diagnosis and possibly improve outcome if preventative or specific therapeutic options can be found.

Quantitative lung T cell responses aid the rapid diagnosis of pulmonary tuberculosis.

BACKGROUND: The diagnosis of smear-negative pulmonary tuberculosis (TB) is problematic. There are limited data on the profile of alveolar TB antigen-specific T cells, and their utility for the rapid immunodiagnosis of pulmonary TB is unclear. METHODS: Antigen-specific interferon gamma (IFNgamma) responses to the RD-1 antigens ESAT-6 and CFP-10 (T-SPOT.TB and QuantiFERON-TB-Gold-In-Tube), heparin-binding haemagglutinin and purified protein derivative were evaluated, using alveolar lavage cells, in 91 consecutively recruited South African patients suspected of having TB. RESULTS: Of 85 evaluable patients (29% HIV+), 24, 11, 48 and 2 had definite TB, probable TB, non-TB and an uncertain diagnosis, respectively. Between 34% (T-SPOT.TB) and 41% (QuantiFERON-TB-Gold-In-Tube) of all test results were inconclusive. Failure of the positive control was significantly higher with the QuantiFERON-TB-Gold-In-Tube than with T-SPOT.TB (85% vs 46% of inconclusive results; p = 0.001). Using staphylococcal enterotoxin B, compared with phytohaemagglutinin, substantially reduced failure of the positive control (25% to 3%; p = 0.02). In evaluable samples, when the definite and non-TB groups were used for outcome analysis, the percentage sensitivity, specificity, positive predictive value and negative predictive value for T-SPOT.TB (> or = 20 spots/million alveolar mononuclear cells) and QuantiFERON-TB-Gold-In-Tube (0.35 IU/ml) were 89, 94, 89 and 94% (n = 55) and 55, 86, 77 and 69% (n = 46), respectively. Rapid diagnosis of TB was achieved more frequently with T-SPOT.TB than with smear microscopy (14/24 (58%) vs. 7/24 (29%) of definite TB cases; p = 0.02). Heparin-binding haemagluttinin and purified protein derivative alveolar lymphocyte IFNgamma responses had poor performance outcomes. CONCLUSION: Provided evaluable results are obtained, the RD-1, but not the heparin-binding haemagglutinin or purified protein derivative, alveolar lymphocyte IFNgamma ELISPOT response is a useful rapid immunodiagnostic test for TB. However, test utility in high-burden settings may be limited by the high proportion of inconclusive results.

Utility of quantitative T-cell responses versus unstimulated interferon-{gamma} for the diagnosis of pleural tuberculosis.

The clinical utility of antigen-specific interferon (IFN)-gamma release assays (IGRAs) using pleural mononuclear cells, for the diagnosis of tuberculosis (TB), requires clarification. We compared the diagnostic utility of unstimulated pleural IFN-gamma levels with several pleural antigen-specific T-cell IGRAs (early secretory antigenic target-6 and culture filtrate protein-10 (T-SPOT.(R)TB, QuantiFERON(R)-TB Gold In-tube), purified protein derivative (PPD) and heparin-binding haemagglutinin (HBHA)) in 78 South African TB suspects. Test results were compared against a clinical score and a reference standard. Out of 74 evaluable subjects 48, seven and 19 had definite, probable and no TB, respectively. 11 (15%) out of 74 pleural samples (nine (19%) out of 48 of the definite TB cases) had total cell counts that were inadequate for T-cell processing. In the remaining 63 samples, the sensitivity, specificity, positive predictive value and negative predictive value of different diagnostic methods were as follows. Maximal bioclinical score: 54, 89, 92 and 43%, respectively; T-SPOT.(R)TB: 86, 60, 84 and 64%, respectively; QuantiFERON(R)-TB Gold In-tube: 57, 80, 87 and 44%, respectively; HBHA-specific IGRA: 59, 31, 64 and 27%, respectively; PPD-specific IGRA: 81, 40, 76 and 46%, respectively; and pleural fluid unstimulated IFN-gamma: 97, 100, 100 and 94%, respectively. Unstimulated IFN-gamma was the most accurate test for distinguishing TB from non-TB effusions in a high-burden setting. The antigen-specific T-cell IGRAs were limited by suboptimal accuracy and the inability to isolate sufficient mononuclear cells to perform the assay.