Karina Butler

IRF8 Mutations and Human Dendritic-Cell Immunodeficiency

BACKGROUND The genetic analysis of human primary immunodeficiencies has defined the contribution of specific cell populations and molecular pathways in the host defense against infection. Disseminated infection caused by bacille Calmette-Guérin (BCG) vaccines is an early manifestation of primary immunodeficiencies, such as severe combined immunodeficiency. In many affected persons, the cause of disseminated BCG disease is unexplained. METHODS We evaluated an infant presenting with features of severe immunodeficiency, including early-onset disseminated BCG disease, who required hematopoietic stem-cell transplantation. We also studied two otherwise healthy subjects with a history of disseminated but curable BCG disease in childhood. We characterized the monocyte and dendritic-cell compartments in these three subjects and sequenced candidate genes in which mutations could plausibly confer susceptibility to BCG disease. RESULTS We detected two distinct disease-causing mutations affecting interferon regulatory factor 8 (IRF8). Both K108E and T80A mutations impair IRF8 transcriptional activity by disrupting the interaction between IRF8 and DNA. The K108E variant was associated with an autosomal recessive severe immunodeficiency with a complete lack of circulating monocytes and dendritic cells. The T80A variant was associated with an autosomal dominant, milder immunodeficiency and a selective depletion of CD11c+CD1c+ circulating dendritic cells. CONCLUSIONS These findings define a class of human primary immunodeficiencies that affect the differentiation of mononuclear phagocytes. They also show that human IRF8 is critical for the development of monocytes and dendritic cells and for antimycobacterial immunity. (Funded by the Medical Research Council and others.).

Mother-to-child transmission of hepatitis C virus: evidence for preventable peripartum transmission.

BACKGROUND Little information is available about the timing of mother-to-child transmission of hepatitis C virus (HCV), and no interventions to decrease transmission rates have been identified. We examined the effect of risk factors, including mode of delivery, on the vertical transmission rate. METHODS Data from HCV-infected women and their infants from three hospitals in Ireland and from a British Paediatric Surveillance Unit study of infants born to HCV-infected mothers were used to estimate the vertical transmission rate and risk factors for transmission. We used a probabilistic model using methods that simultaneously estimated the time to HCV-antibody loss in uninfected infants and the diagnostic accuracy of PCR tests for HCV RNA. FINDINGS 441 mother-child pairs from the UK (227) and Ireland (214) were included. 50% of uninfected children became HCV-antibody negative by 8 months and 95% by 13 months. The estimated specificity of PCR for HCV RNA was 97% (95% CI 96-99) and was unrelated to age; sensitivity was only 22% (7-46) in the first month but rose sharply to 97% (85-100) thereafter. The vertical transmission rate was 6.7% (4.1-10.2) overall, and 3.8 times higher in HIV coinfected (n=22) than in HIV-negative women after adjustment for other factors (p=0.06). No effect of breastfeeding on transmission was observed, although only 59 women breastfed. However, delivery by elective caesarean section before membrane rupture was associated with a lower transmission risk than vaginal or emergency caesarean-section delivery (odds ratio 0 [0-0.87], p=0.04, after adjustment for other factors). INTERPRETATION The low sensitivity of HCV RNA soon after birth and the finding of a lower transmission rate after delivery by elective caesarean section suggest that HCV transmission occurs predominantly around the time of delivery. If the findings on elective caesarean section are confirmed in other studies, the case for antenatal HCV testing should be reconsidered.

Decline in mortality, AIDS, and hospital admissions in perinatally HIV-1 infected children in the United Kingdom and Ireland

Abstract Objective To describe changes in demographic factors, disease progression, hospital admissions, and use of antiretroviral therapy in children with HIV. Design Active surveillance through the national study of HIV in pregnancy and childhood (NSHPC) and additional data from a subset of children in the collaborative HIV paediatric study (CHIPS). Setting United Kingdom and Ireland. Participants 944 children with perinatally acquired HIV-1 under clinical care. Main outcome measures Changes over time in progression to AIDS and death, hospital admission rates, and use of antiretroviral therapy. Results 944 children with perinatally acquired HIV were reported in the United Kingdom and Ireland by October 2002; 628 (67%) were black African, 205 (22%) were aged ≥ 10 years at last follow up, 193 (20%) are known to have died. The proportion of children presenting who were born abroad increased from 20% in 1994-5 to 60% during 2000-2. Mortality was stable before 1997 at 9.3 per 100 child years at risk but fell to 2.0 in 2001-2 (trend P < 0.001). Progression to AIDS also declined (P < 0.001). From 1997 onwards the proportion of children on three or four drug antiretroviral therapy increased. Hospital admission rates declined by 80%, but with more children in follow up the absolute number of admissions fell by only 26%. Conclusion In children with HIV infection, mortality, AIDS, and hospital admission rates have declined substantially since the introduction of three or four drug antiretroviral therapy in 1997. As infected children in the United Kingdom and Ireland are living longer, there is an increasing need to address their medical, social, and psychological needs as they enter adolescence and adult life.

Amphotericin B as a single agent in the treatment of systemic candidiasis in neonates

We conducted a retrospective review of neonates with systemic candidiasis at a Houston hospital during the 5-year period 1982 through 1986. Factors associated with these infections, their clinical features, criteria for their diagnosis and the dose, duration, toxicity and efficacy of amphotericin B therapy were analyzed

Maternal viral load, CD4 cell count and vertical transmission of HIV‐1

HIV load and CD4 cell numbers were measured among 95 HIV infected women during pregnancy in order to determine their value as prognostic markers for transmission of virus from mother to infant. Among the 94 live births, 13 children were infected with HIV, 69 were uninfected and 12 were of unknown infection status. HIV RNA levels, as measured by nucleic acid sequence based amplification, were significantly higher (P < 0.001) in women who transmitted virus than among those who did not transmit and maternal viral load was a stronger predictor of transmission than CD4 cell number. The predicted rate of transmission relative to maternal HIV RNA was 2% at 1,000 copies, 11% at 10,000 copies and 40% at 100,000 copies/ml. Little variation in viral load occurred during pregnancy and there was an association between viral load and prematurity, the mean gestation at delivery decreasing by 1.3 weeks for every 10‐fold increase in maternal HIV RNA (P = 0.007). This study demonstrates that a high level of maternal HIV RNA is a risk factor for transmission of virus to the infant and maternal viral load is of more value as a prognostic marker for transmission risk than CD4 cell number. High viral load is also associated with premature delivery. Maternal viral load is therefore a useful marker on which to base management decisions during pregnancy. J. Med. Virol. 54:113–117, 1998.

Outcomes for human immunodeficiency virus-1-infected infants in the United kingdom and Republic of Ireland in the era of effective antiretroviral therapy.

Background: There are few data about disease progression and response to antiretroviral therapy (ART) in vertically HIV-infected infants in the era of effective therapy. Design: Cohort study. Methods: We examined progression to acquired immunodeficiency syndrome (AIDS) and death over calendar time for infants reported to the National Study of HIV in Pregnancy and Childhood in the United Kingdom/Ireland. The use of ART and CD4 and HIV-1 RNA responses were assessed in a subset in the Collaborative HIV Pediatric Study. Results: Among 481 infants, mortality was lower in those born after 1997 (HR 0.30; P < 0.001), with no significant change in progression to AIDS. Of 174 infants born since 1997 in the Collaborative HIV Pediatric Study, 41 (24%) were followed from birth, 77 (44%) presented pre-AIDS and 56 (32%) presented with AIDS. Of 125 (72%) children on 3- or 4-drug ART by the age of 2 years, 59% had HIV-1 RNA <400 at 12 months; median CD4 percentage increased from 24% to 35%. Among 41 infants followed from birth, 12 progressed to AIDS (5 while ART naive) and 3 died; 1 of 10 infants initiating ART before 3 months of age progressed clinically. Conclusion: Mortality in HIV-infected infants is significantly lower in the era of effective ART, but symptomatic disease rates remain high. Infrequent clinic attendance and poor compliance with cotrimoxazole prophylaxis and/or ART in infants born to diagnosed HIV-infected women and late presentation of infants identified after birth appear to be major contributors. Poor virologic response to ART during infancy is of concern because of increased likelihood of early development of resistance.

Control of a nosocomial outbreak of vancomycin resistant Enterococcus faecium in a paediatric oncology unit: risk factors for colonisation

Abstract In order to determine the extent of vancomycin resistant enterococcus (VRE) colonisation within a paediatric oncology unit, the risk factors for the acquisition of the organism, the molecular epidemiology of the isolates and the impact of infection control measures, extensive patient and environmental surveillance was undertaken with identification, antibiotic susceptibility testing and pulsed-field gel electrophoresis (PFGE) of all VRE isolates. A matched case control study was carried out. Fourteen patients (19% of screened patients) with VRE colonisation were identified (12 with Enterococcus faecium). All isolates manifested the Van A phenotype. Extensive environmental contamination with VRE was present. PFGE of E. faecium isolates from 10 patients and from five of six environmental cultures revealed patterns suggesting genetic relatedness. Following comparison of the 14 cases with 41 controls matched for age (±4 years) and cohabitation on the oncology unit, risk factors for colonisation with VRE included duration of neutropenia, (OR, 3.72; 95% CI, 1.0–13.1), and antibiotic therapy, (OR, 4.07; 95% CI, 1.08–15.3), the number of antibiotic agents received, (OR, 8.4; 95% CI, 1.34–34.3) and the duration of therapy with amikacin, (OR, 10.7; 95% CI, 1.4–81.5), ceftazidime, (OR, 11.5; 95% CI, 2.2–59.9) or teicoplanin, (OR, 12.3; 95% CI, 2.25–67.4). Implementation of stringent infection control measures reduced environmental contamination from 25% of samples in week 1 to none in week 11. Two additional colonised patients were identified during the subsequent 6 months. Conclusion Risk factors for VRE colonization in paediatric oncology patients included duration of neutropenia, duration of any antibiotic therapy, exposure to ceftazidime, amikacin or teicoplanin and the number of antibiotics used. The study suggests that environmental contamination played an important role in patient-to-patient transmission of VRE and interventions including implementation of infection control measures were associated with a decreased incidence of gastro-intestinal colonisation.

Long-Term Excretion of Vaccine-Derived Poliovirus by a Healthy Child

ABSTRACT A child was found to be excreting type 1 vaccine-derived poliovirus (VDPV) with a 1.1% sequence drift from Sabin type 1 vaccine strain in the VP1 coding region 6 months after he was immunized with oral live polio vaccine. Seventeen type 1 poliovirus isolates were recovered from stools taken from this child during the following 4 months. Contrary to expectation, the child was not deficient in humoral immunity and showed high levels of serum neutralization against poliovirus. Selected virus isolates were characterized in terms of their antigenic properties, virulence in transgenic mice, sensitivity for growth at high temperatures, and differences in nucleotide sequence from the Sabin type 1 strain. The VDPV isolates showed mutations at key nucleotide positions that correlated with the observed reversion to biological properties typical of wild polioviruses. A number of capsid mutations mapped at known antigenic sites leading to changes in the viral antigenic structure. Estimates of sequence evolution based on the accumulation of nucleotide changes in the VP1 coding region detected a “defective” molecular clock running at an apparent faster speed of 2.05% nucleotide changes per year versus 1% shown in previous studies. Remarkably, when compared to several type 1 VDPV strains of different origins, isolates from this child showed a much higher proportion of nonsynonymous versus synonymous nucleotide changes in the capsid coding region. This anomaly could explain the high VP1 sequence drift found and the ability of these virus strains to replicate in the gut for a longer period than expected.

Potentiation of vincristine toxicity by itraconazole in children with lymphoid malignancies

Eight consecutive paediatric patients with acute lymphoblastic leukaemia (ALL) (n=7) and T‐cell non‐Hodgkins lymphoma (NHL) (n=1) presenting within a 5‐wk interval were started on a standard induction protocol which included weekly treatment with vincristine for 4 wk. Itraconazole was commenced as antifungal prophylaxis, 1–21 d after the first injection of vincristine. Within 2 to 4 wk, enhanced vincristine neurotoxicity was noted in all patients, abdominal cramps and constipation occurred most frequently, and one patient developed a bowel perforation associated with paralytic ileus. Hyponatraemia associated with SIADH was observed in three patients and four patients developed seizures. An additional patient with B cell NHL developed seizures 5 d after an injection of vincristine. Recovery was complete in all patients and ranged from 2 d to 15 wk.

Complications associated with the bacille Calmette-Guérin vaccination in Ireland.

Introduction: BCG vaccination is currently recommended for all newborns in Ireland except where specifically contraindicated. This paper describes a marked increase in the number of referrals of patients with localised complications after vaccination to two Dublin paediatric hospitals. This increase coincided with the introduction of a new strain of BCG vaccine Methods: A population surveillance study was undertaken to determine the frequency and spectrum of complications associated with the new strain of BCG vaccine introduced in Ireland. Patients were identified though review of the infectious disease service case records and microbiology laboratory culture reports for the two year period from August 2002 to July 2004. Prospectively gathered data were supplemented by retrospective chart review. All infants who had inoculation site abscesses, suppurative adenopathy, or non-suppurative adenopathy with nodes ⩾2 cm were included. Results: Fifty eight patients presented a median of 13 weeks post-inoculation: 32 with suppurative adenitis, 17 with inoculation site abscess, three with both inoculation site abscess and suppurative adenitis, and six with non-suppurative adenopathy. The overall complication rate was estimated at 1/931 vaccinees with 1/1543 developing suppurative adenitis. Twenty six infants required surgery. Discussion: This series illustrates the role of hospitals in sentinel surveillance and highlights the importance of having a well functioning and responsive system of adverse event reporting. These events raise a serious question as to the suitability of this vaccine strain for use in a national immunisation programme in a country where the prevalence of tuberculous disease is 10.4/100 000.