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.

Endoscopy findings in HIV-infected children from sub-Saharan Africa.

BACKGROUND: The causes of persistent gastro-intestinal symptoms in HIV-infected children from sub-Saharan Africa remain poorly documented. METHODS: The clinical, radiological and endoscopic findings of all HIV-infected children who underwent upper GI endoscopy at Red Cross Children's Hospital, Cape Town, South Africa, from February 2003 to October 2005 were documented. RESULTS: Twenty-six HIV-infected children underwent endoscopy; median age 1 year (range: 0.17-10.9 years). The majority had advanced HIV disease; 18 (69%) were WHO Stage 4; median CD4 10.7% (range: 1-39.8%). Presenting symptoms included persistent vomiting (18), dysphagia (4) and GIT bleed (6). Observational and histological findings showed poor correlation. Pathogens were identified in 10 children: cytomegalovirus infection in seven (two with cryptosporidium co-infection), Candida in two, Helicobacter pylori in one. Age and CD4 count were not associated with the pathogens. Endoscopy findings influenced clinical management in 21 (81%) cases. CONCLUSION: Upper-GI endoscopy identified a diverse spectrum of disease and provided information that would be clinically relevant to most HIV-infected children with upper gastro-intestinal symptoms.

Are children with clefts underweight for age at the time of primary surgery?

Children with clefts, especially those with a cleft palate, have an impaired sucking mechanism and are therefore prone to nutritional problems. This study was undertaken to determine whether children with clefts of the lip and/or palate are underweight for age at the time of primary surgery. Underweight for age was defined as being less than 80 percent of expected weight for age or below the 3rd percentile as plotted on standard percentile charts. The records of all children with clefts seen at the Red Cross Children's Hospital between 1976 and 1996 were reviewed. Of these 740 records, 100 were excluded for inadequate data (47), severe systemic syndrome (27), no operation done (22), or craniofacial cleft (4). The records of 640 children were thus included; 195 (30.5 percent) were underweight for age. By comparison, only 13.7 percent of a similar group of noncleft controls (n = 872) were underweight for age. The difference between these two groups was highly significant (p < 0.01). Factors that influenced weight at the time of primary surgery were type of cleft and age at the time of surgery. Children with cleft palate, whether associated with a cleft lip or not, were found to be more underweight for age than those with an isolated unilateral cleft lip (p = 0.008). Children who had surgery after the age of 1 year were 1.5 times more likely to be underweight for age than children who had surgery under 1 year of age (p < 0.01). Children with isolated cleft palates who were underweight for age had a tendency toward a higher fistula rate (36 percent) than those of normal weight (24 percent) (p = 0.18).

Guillain-Barré syndrome in South Africa associated with Campylobacter jejuni O:41 strains.

Over a 20-month period, 3 adult and 6 pediatric patients were diagnosed with Guillain-Barré syndrome (GBS) at Groote Schuur and Red Cross Hospitals in Cape Town. All 9 GBS patients had Campylobacter jejuni biotype 2, serotype O:41 in their stools. C. jejuni infection was confirmed by ELISA testing of patient sera. Strains of this sero-biotype are rare: Only 12 such strains, including the GBS-associated strains, were recognized among 776 Campylobacter strains isolated and identified at Red Cross Hospital from March 1994 to October 1995. This is the first known association of C. jejuni biotype 2, serotype O:41 with GBS. Patients infected with this Campylobacter strain had a particularly severe form of the infection, requiring hospitalization and ventilation much longer than GBS patients infected with other Campylobacter species and patients with Campylobacter-negative stools. The O:41 Campylobacter isolates from the GBS patients are identical by phenotypic, serologic, and molecular criteria, and they are clonal.

Campylobacter 0:41 isolation in Guillain-Barré syndrome.

Over a period of 15 months, 17 children were admitted to the Red Cross War Memorial Children's Hospital (RCWMCH) in Cape Town with Guillain-Barré syndrome. Stool specimens were collected from 14 children and campylobacter was isolated from nine. Six of the nine isolates of Campylobacter jejuni were further identified as C jejuni biotype 2, serotype 0:41. This biotype 2, serotype 0:41 has been identified in only 12 of the 7119 campylobacter isolates at the RCWMCH over a 19 year period. Eight of the nine patients with campylobacter isolates and one of five with negative stool cultures required ventilation. Patients with C jejuni biotype 2, serotype 0:41 were ventilated for a mean (SD) of 33.5 (19.4) days, whereas patients with other campylobacter isolates were ventilated for 17.3 (3.8) days. This is the first report of campylobacters of serotype 0:41 in Guillain-Barré syndrome and could reflect a geographical isolation of this strain.

The effect of Edmonston-Zagreb and Schwarz measles vaccines on immune response in infants.

The effects of measles immunization on immune responses in infants and the roles of vaccine strain and age of immunization are not known. Eighty-eight children were immunized at 6 or 9 months of age with the Edmonston-Zagreb (EZ) or Schwarz (SW6, SW9) strain of measles vaccine. Children were studied before and 2 weeks and 3 months after immunization. Seroconversion was similar, but geometric mean neutralizing titers at 3 months differed by vaccine group: SW9, 1367 mIU/mL; SW6, 982; and EZ, 303 (P = .003). Mitogen-induced lymphoproliferation was decreased at 2 weeks in the SW9 group and at 3 months in all groups and was negatively correlated with measles antibody level at 3 months (r = -.387, P = .003). CD8 T cells, soluble CD8, neopterin, and beta2-microglobulin were increased at 2 weeks in the SW9 group, and soluble CD8 and beta2-microglobulin remained elevated at 3 months. Therefore, measles immunization resulted in suppression of lymphoproliferation, which was most evident in infants with the highest antibody responses and most immune activation.

Changes within T cell receptor V beta subsets in infants following measles vaccination.

Measles produces immune suppression which contributes to an increased susceptibility to other infections. Recently, high titered measles vaccines have been linked to increased long-term mortality among some female recipients. Because the mechanisms by which wild-type or attenuated live-vaccine strains of measles virus alter subsequent immune responses are not fully understood, this prompted an examination of the changes within the peripheral blood T cell receptor V beta repertoire following measles immunization. Twenty-four 6- and 9-month-old infants were studied at 2 weeks and 3 months following immunization by semiquantitative reverse transcription-polymerase chain reaction. There was a significant increase in V beta 2 expression (P less than 0.05), and a decrease in the V beta 4 subset (P less than 0.03) 2 weeks following vaccination with subsequent return to baselines at 3 months in vaccine recipients who seroconverted. These data suggest that measles virus may affect immune responses in part by altering the T cell receptor repertoire.

Immunoglobulin allotypes and genetic susceptibility to invasive Haemophilus influenzae type b and Staphylococcus aureus infections in South African children.

OBJECTIVE: The purpose of this study was to determine whether the G2m(n), G1m(f) and Km(3) immunoglobulin allotypes have any association with susceptibility to invasive Haemophilus influenzae type b (Hib) and Staphylococcus aureus (S. aureus) infections in children. METHODS: Direct enzyme-linked immunosorbent assays with commercially available monoclonal antibodies were established to quantitate G2m(n) and G1m(f) allotypes. A qualitative enzyme-linked immunosorbent assay with polyclonal rabbit anti-Km(3) antibody was established for Km(3) determination. RESULTS: The G2m(n) marker occurred in 34.4% of the mixed ancestry population and 2.9% of the Black population. There was a significantly decreased frequency of the G2m(n) allotype in mixed ancestry children with Hib meningitis (8.5%) and Hib osteomyelitis/septic arthritis and a decreased frequency of Km(3) in black and mixed ancestry children with Hib meningitis. The frequency of G2m(n), G1m(f) and Km(3) allotypes in patients with S. aureus osteomyelitis/septic arthritis were not significantly different from normal population frequency. CONCLUSIONS: This study shows a clear association between the absence of the G2m(n) allotype in mixed ancestry children and susceptibility to invasive infections caused by H. influenzae and an association between the absence of Km(3) and Hib meningitis in both black and mixed ancestry children.

Mutations in the human mannose-binding protein gene: frequencies in several population groups.

Mannose-binding protein (MBP; mannan-binding protein, mannan-binding lectin) is a member of the collectin family of proteins and is thought to be important in innate immunity. We have previously shown high frequencies of two distinct mutations in codon 54 and codon 57 of exon 1 of the MBP gene in non-African and African populations, respectively. These result in low levels of the protein and an opsonic deficiency but the frequencies also suggest some selective advantage for low MBP levels. A third mutation in codon 52 occurs at a much lower frequency. We have now extended our earlier studies to other populations. In the south-west Pacific (Papua New Guinea and Vanuatu) neither the codon 52 nor the codon 57 mutation was detected and the codon 54 mutation was significantly less common (gene frequencies of 0.07 and 0.01, respectively) than in other non-African populations (gene frequencies 0.11-0.16). This could be explained by relatively recent admixture. The ancestral Melanesian population probably diverged some 50,000-60,000 years ago and our data suggest that the codon 54 mutation may have occurred after that even but before the divergence of European-Asian groups (40,000 years ago). Two further sub-Saharan populations were also studied: a group of Xhosa from South Africa were similar to Gambians, with a high gene frequency for the codon 57 mutation (0.27) and no evidence of the codon 52 or 54 mutations. In contrast, San Bushmen from Namibia had low frequencies of both the codon 57 mutation (0.07) and the codon 54 mutation (0.03). Again the codon 52 mutation was not found. This pattern is unique amongst sub-Saharan populations studied to date and suggests that this population may have been subjected to different selective pressures.

Flow cytometry analysis of OKT4 epitope deficiency in South African black children.

A case of OKT4 epitope deficiency referred for investigation with suspected immunodeficiency is described. Flow cytometry analysis of OKT4 epitope deficiency in a study group of healthy black children showed different manifestations of the lack of OKT4 epitope; a complete lack of OKT4+CD4+ peripheral blood lymphocytes (PBL) with normal numbers of OKT4A+ and Leu3a-CD4+ PBL, decreased percentage OKT4+CD4+ compared with OKT4A+ and Leu-3a+CD4+ PBL, decreased fluorescent staining intensity with OKT4 and a biphasic OKT4 staining pattern associated with a reduced OKT4/Leu-3a ratio. The percentage and fluorescent intensity of OKT4+CD4+ PBL in the study group were significantly lower (P < 0.0001) than Leu-3a+CD4+ and OKT4A+CD4+ PBL. There is thus considerable risk of under-estimating the number of CD4+ cells in black South Africans if the OKT4 MoAb is used.

The management of skin infarction after meningococcal septicaemia in children.

The clinical course and management of 21 children (12 females, 9 males; mean age 2.4 years) with skin necrosis secondary to meningococcal septicaemia is described. Skin necrosis was most commonly sited in the lower limbs (20 patients). Sixteen patients had multiple areas of involvement and amputation of the digits was required in 5 patients. One required an above knee amputation. Small areas of skin necrosis were managed conservatively (4 patients) but larger areas required debridement and grafting. Skin grafting was delayed in 15 patients and graft loss occurred in 8. Multiple grafting procedures were required in 6 patients. Scar revision was required in 6 patients. Nutritional support is also an important component of management.

IgG subclass values from normal children in Cape Town.

Sensitive and reproducible enzyme-linked immunoabsorbent assays (ELISA) have been developed to quantitate IgG subclass levels using monoclonal antibodies. Normal values for serum IgG subclass levels were determined in 300 healthy children between 6 months and 14 years of age and in 80 adults. High levels of IgG1 and delayed maturational development of IgG2 in children from Cape Town are different to results reported from developed countries. Genetic differences may account for this.

Treatment of chronic granulomatous disease with recombinant gamma interferon.

Chronic granulomatous disease is a rare, primary immunodeficiency associated with serious bacterial and fungal infections caused by phagocytic defects of oxidative metabolism. To date the mainstay of management has been aggressive treatment of infections and the use of prophylactic antibiotics. Two patients, who showed remarkable clinical improvement when treated with recombinant gamma interferon, are reported. Both have been on treatment for at least 18 months and have continued to thrive and remain free of infections.

Hyper IgM with combined immunodeficiency.

This report describes a fourteen year old girl with an unusual immunodeficiency characterized by persistent lymphadenopathy and associated with hypogammaglobulinaemia, excessive IgM production and a severe T cell defect. Total T cell and T helper cell numbers were reduced and T cell proliferative responses to mitogens were poor. Serum IgM levels showed marked fluctuations and peaks correlated with acute tender lymphadenopathy. She was treated with intravenous gammaglobulin and prophylactic antibiotics. Although defective isotype switching of B cells into IgA and IgG producing cells has been accepted as the mechanism of the hyper IgM syndrome, it is becoming increasingly evident that T cell function is not uncommonly involved and may be responsible for impaired isotype switching.

X-linked agammaglobulinaemia.

X-linked agammaglobulinaemia (XLA) is a rare immunodeficiency disorder affecting only male subjects. There is an absence of all serum immunoglobulins and circulating B cells. T-cell function and numbers are normal. The clinical characteristics are recurrent pyogenic infections starting in infancy, hypoplasia of lymphoid tissue and a family history in about half the cases. Ten patients with XLA have been seen over the last 14 years at Red Cross War Memorial Children's Hospital, Cape Town. Chronic infections causing significant morbidity occurred in half our patients and 2 have died. Intravenous of gammaglobulin replacement therapy is superior to the intramuscular form. The recommended dose is 200-400 mg/kg/mo., although the optimal dose and frequency of the gammaglobulin infusion should be individualised for each patient.