Germline SAMD9L truncation variants trigger global translational repression

SAMD9L is an interferon-induced tumor suppressor implicated in a spectrum of multisystem disorders, including risk for myeloid malignancies and immune deficiency. We identified a heterozygous de novo frameshift variant in SAMD9L in an infant with B cell aplasia and clinical autoinflammatory features who died from respiratory failure with chronic rhinovirus infection. Autopsy demonstrated absent bone marrow and peripheral B cells as well as selective loss of Langerhans and Purkinje cells. The frameshift variant led to expression of a truncated protein with interferon treatment. This protein exhibited a gain-of-function phenotype, resulting in interference in global protein synthesis via inhibition of translational elongation. Using a mutational scan, we identified a region within SAMD9L where stop-gain variants trigger a similar translational arrest. SAMD9L variants that globally suppress translation had no effect or increased mRNA transcription. The complex-reported phenotype likely reflects lineage-dominant sensitivities to this translation block. Taken together, our findings indicate that interferon-triggered SAMD9L gain-of-function variants globally suppress translation.

Multiplexed Functional Assessment of Genetic Variants in CARD11

Genetic testing has increased the number of variants identified in disease genes, but the diagnostic utility is limited by lack of understanding variant function. CARD11 encodes an adaptor protein that expresses dominant-negative and gain-of-function variants associated with distinct immunodeficiencies. Here, we used a "cloning-free" saturation genome editing approach in a diploid cell line to simultaneously score 2,542 variants for decreased or increased function in the region of CARD11 associated with immunodeficiency. We also described an exon-skipping mechanism for CARD11 dominant-negative activity. The classification of reported clinical variants was sensitive (94.6%) and specific (88.9%), which rendered the data immediately useful for interpretation of seven coding and splicing variants implicated in immunodeficiency found in our clinic. This approach is generalizable for variant interpretation in many other clinically actionable genes, in any relevant cell type.

Correction: Chronic Granulomatous Disease-Associated IBD Resolves and Does Not Adversely Impact Survival Following Allogeneic HCT

The original version of this article unfortunately contained the missing author, Caridad Martinez. The authors would like to correct the list. We apologize for any inconvenience that this may have caused. The correct author list is shown above.

HLA-Haploidentical Hematopoietic Cell Transplantation for Treatment of Nonmalignant Diseases Using Nonmyeloablative Conditioning and Post-Transplant Cyclophosphamide

Allogeneic hematopoietic cell transplant (HCT) is often the only curative therapy for patients with nonmalignant diseases; however, many patients do not have an HLA-matched donor. Historically, poor survival has been seen after HLA-haploidentical HCT because of poor immune reconstitution, increased infections, graft-versus-host disease (GVHD), and graft failure. Encouraging results have been reported using a nonmyeloablative T cell-replete HLA-haploidentical transplant approach in patients with hematologic malignancies. Here we report the outcomes of 23 patients with various nonmalignant diseases using a similar approach. Patients received HLA-haploidentical bone marrow (n = 17) or granulocyte colony-stimulating factor-mobilized peripheral blood stem cell (n = 6) grafts after conditioning with cyclophosphamide 50 mg/kg, fludarabine 150 mg/m², and 2 or 4 Gy total body irradiation. Postgrafting immunosuppression consisted of cyclophosphamide, mycophenolate mofetil, tacrolimus, ± sirolimus. Median patient age at HCT was 10.8 years. Day 100 transplant-related mortality (TRM) was 0%. Two patients died at later time points, 1 from intracranial hemorrhage/disseminated fungal infection in the setting of graft failure and 1 from infection/GVHD. The estimated probabilities of grades II to IV and III to IV acute GVHD at day 100 and 2-year National Institutes of Health consensus chronic GVHD were 78%, 26%, and 42%, respectively. With a median follow-up of 2.5 years, the 2-year overall and event-free rates of survival were 91% and 78%, respectively. These results are encouraging and demonstrate favorable disease-specific lineage engraftment with low TRM in patients with nonmalignant diseases using nonmyeloablative conditioning followed by T cell-replete HLA-haploidentical grafts. However, additional strategies are needed for GVHD prevention to make this a viable treatment approach for patients with nonmalignant diseases.

Hematopoietic Cell Transplantation in Patients With Primary Immune Regulatory Disorders (PIRD): A Primary Immune Deficiency Treatment Consortium (PIDTC) Survey

Primary Immune Regulatory Disorders (PIRD) are an expanding group of diseases caused by gene defects in several different immune pathways, such as regulatory T cell function. Patients with PIRD develop clinical manifestations associated with diminished and exaggerated immune responses. Management of these patients is complicated; oftentimes immunosuppressive therapies are insufficient, and patients may require hematopoietic cell transplant (HCT) for treatment. Analysis of HCT data in PIRD patients have previously focused on a single gene defect. This study surveyed transplanted patients with a phenotypic clinical picture consistent with PIRD treated in 33 Primary Immune Deficiency Treatment Consortium centers and European centers. Our data showed that PIRD patients often had immunodeficient and autoimmune features affecting multiple organ systems. Transplantation resulted in resolution of disease manifestations in more than half of the patients with an overall 5-years survival of 67%. This study, the first to encompass disorders across the PIRD spectrum, highlights the need for further research in PIRD management.

SCID genotype and 6-month posttransplant CD4 count predict survival and immune recovery

The Primary Immune Deficiency Treatment Consortium (PIDTC) performed a retrospective analysis of 662 patients with severe combined immunodeficiency (SCID) who received a hematopoietic cell transplantation (HCT) as first-line treatment between 1982 and 2012 in 33 North American institutions. Overall survival was higher after HCT from matched-sibling donors (MSDs). Among recipients of non-MSD HCT, multivariate analysis showed that the SCID genotype strongly influenced survival and immune reconstitution. Overall survival was similar for patients with RAG, IL2RG, or JAK3 defects and was significantly better compared with patients with ADA or DCLRE1C mutations. Patients with RAG or DCLRE1C mutations had poorer immune reconstitution than other genotypes. Although survival did not correlate with the type of conditioning regimen, recipients of reduced-intensity or myeloablative conditioning had a lower incidence of treatment failure and better T- and B-cell reconstitution, but a higher risk for graft-versus-host disease, compared with those receiving no conditioning or immunosuppression only. Infection-free status and younger age at HCT were associated with improved survival. Typical SCID, leaky SCID, and Omenn syndrome had similar outcomes. Landmark analysis identified CD4+ and CD4+CD45RA+ cell counts at 6 and 12 months post-HCT as biomarkers predictive of overall survival and long-term T-cell reconstitution. Our data emphasize the need for patient-tailored treatment strategies depending upon the underlying SCID genotype. The prognostic significance of CD4+ cell counts as early as 6 months after HCT emphasizes the importance of close follow-up of immune reconstitution to identify patients who may need additional intervention to prevent poor long-term outcome.

Clinical efficacy of gene-modified stem cells in adenosine deaminase-deficient immunodeficiency

BACKGROUND

Autologous hematopoietic stem cell transplantation (HSCT) of gene-modified cells is an alternative to enzyme replacement therapy (ERT) and allogeneic HSCT that has shown clinical benefit for adenosine deaminase-deficient (ADA-deficient) SCID when combined with reduced intensity conditioning (RIC) and ERT cessation. Clinical safety and therapeutic efficacy were evaluated in a phase II study.

METHODS

Ten subjects with confirmed ADA-deficient SCID and no available matched sibling or family donor were enrolled between 2009 and 2012 and received transplantation with autologous hematopoietic CD34+ cells that were modified with the human ADA cDNA (MND-ADA) γ-retroviral vector after conditioning with busulfan (90 mg/m2) and ERT cessation. Subjects were followed from 33 to 84 months at the time of data analysis. Safety of the procedure was assessed by recording the number of adverse events. Efficacy was assessed by measuring engraftment of gene-modified hematopoietic stem/progenitor cells, ADA gene expression, and immune reconstitution.

RESULTS

With the exception of the oldest subject (15 years old at enrollment), all subjects remained off ERT with normalized peripheral blood mononuclear cell (PBMC) ADA activity, improved lymphocyte numbers, and normal proliferative responses to mitogens. Three of nine subjects were able to discontinue intravenous immunoglobulin replacement therapy. The MND-ADA vector was persistently detected in PBMCs (vector copy number [VCN] = 0.1-2.6) and granulocytes (VCN = 0.01-0.3) through the most recent visits at the time of this writing. No patient has developed a leukoproliferative disorder or other vector-related clinical complication since transplant.

CONCLUSION

These results demonstrate clinical therapeutic efficacy from gene therapy for ADA-deficient SCID, with an excellent clinical safety profile.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00794508.

FUNDING

Food and Drug Administration Office of Orphan Product Development award, RO1 FD003005; NHLBI awards, PO1 HL73104 and Z01 HG000122; UCLA Clinical and Translational Science Institute awards, UL1RR033176 and UL1TR000124.

Severe combined immunodeficiency (SCID) presenting with neonatal aplastic anemia

Aplastic anemia in the neonate is rare. We report a case of severe combined immunodeficiency (SCID) presenting with neonatal aplastic anemia. This report highlights the importance of considering SCID early in the evaluation of neonatal aplastic anemia prior to the development of infectious complications.

Treosulfan-based conditioning and hematopoietic cell transplantation for nonmalignant diseases: a prospective multicenter trial

Hematopoietic cell transplantation is an effective treatment for patients with nonmalignant diseases and for many is the only known cure. Conventional myeloablative regimens have been associated with unacceptably high early transplant-related mortality (TRM), particularly in patients with comorbid conditions. This prospective multicenter trial was designed to determine the safety and engraftment efficacy of treosulfan-based conditioning in patients with nonmalignant diseases. Thirty-one patients received HLA-matched related (n = 4) or unrelated (n = 27) grafts after conditioning with treosulfan (total dose, 42 g/m(2)), fludarabine (total dose, 150 mg/m(2)), ± thymoglobulin (6 mg/kg; n = 22). Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus and methotrexate. All patients engrafted. Day-100 TRM was 0%. With a median follow-up of 2 years, the 2-year survival was 90%. Three patients died of GVHD, recurrent hemophagocytic lymphohistiocytosis, and a surgical complication, respectively. The cumulative incidences of grades II to IV and III to IV acute GVHD at day 100 and chronic GVHD at 2 years were 62%, 10%, and 21%, respectively. Patients who received thymoglobulin had a significantly lower incidence of grades III to IV acute GVHD (0% versus 33%; P = .005). These results indicate that the combination of treosulfan, fludarabine, and thymoglobulin is effective at establishing donor engraftment with low toxicity and improved survival in patients with nonmalignant diseases and support the need for future disease-specific clinical trials.

Transplantation outcomes for severe combined immunodeficiency, 2000-2009

BACKGROUND

The Primary Immune Deficiency Treatment Consortium was formed to analyze the results of hematopoietic-cell transplantation in children with severe combined immunodeficiency (SCID) and other primary immunodeficiencies. Factors associated with a good transplantation outcome need to be identified in order to design safer and more effective curative therapy, particularly for children with SCID diagnosed at birth.

METHODS

We collected data retrospectively from 240 infants with SCID who had received transplants at 25 centers during a 10-year period (2000 through 2009).

RESULTS

Survival at 5 years, freedom from immunoglobulin substitution, and CD3+ T-cell and IgA recovery were more likely among recipients of grafts from matched sibling donors than among recipients of grafts from alternative donors. However, the survival rate was high regardless of donor type among infants who received transplants at 3.5 months of age or younger (94%) and among older infants without prior infection (90%) or with infection that had resolved (82%). Among actively infected infants without a matched sibling donor, survival was best among recipients of haploidentical T-cell-depleted transplants in the absence of any pretransplantation conditioning. Among survivors, reduced-intensity or myeloablative pretransplantation conditioning was associated with an increased likelihood of a CD3+ T-cell count of more than 1000 per cubic millimeter, freedom from immunoglobulin substitution, and IgA recovery but did not significantly affect CD4+ T-cell recovery or recovery of phytohemagglutinin-induced T-cell proliferation. The genetic subtype of SCID affected the quality of CD3+ T-cell recovery but not survival.

CONCLUSIONS

Transplants from donors other than matched siblings were associated with excellent survival among infants with SCID identified before the onset of infection. All available graft sources are expected to lead to excellent survival among asymptomatic infants. (Funded by the National Institute of Allergy and Infectious Diseases and others.).

Stable hematopoietic cell engraftment after low-intensity nonmyeloablative conditioning in patients with immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome

BACKGROUND

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is characterized by severe systemic autoimmunity caused by mutations in the forkhead box protein 3 (FOXP3) gene. Hematopoietic cell transplantation is currently the only viable option for long-term survival, but patients are frequently very ill and may not tolerate traditional myeloablative conditioning regimens.

OBJECTIVE

Here we present the outcome of hematopoietic cell transplantation using a low-intensity, nonmyeloablative conditioning regimen in 2 patients with IPEX syndrome and significant pretransplant risk factors.

METHODS

Two high-risk patients with IPEX syndrome received HLA-matched related bone marrow or unrelated peripheral blood stem cell grafts following conditioning with 90 mg/m(2) fludarabine and 4 Gy total body irradiation. Postgrafting immunosuppression consisted of mycophenolate mofetil and cyclosporine. Immune reconstitution and immune function was evaluated by measurement of donor chimerism, regulatory T-cell numbers, absolute lymphocyte subsets, and T-cell proliferation assays.

RESULTS

Both patients experienced minimal conditioning toxicity and successfully engrafted after hematopoietic cell transplantation. With a follow-up of 4 and 1 years, respectively, patients 1 and 2 have full immune function and normal FOXP3 protein expression.

CONCLUSION

A low-intensity, nonmyeloablative conditioning regimen can establish stable engraftment and correct the life-threatening immune deficiency and enteropathy of IPEX syndrome despite the presence of comorbidities that preclude conventional hematopoietic cell transplantation.

Subcutaneous immunoglobulin replacement therapy in the treatment of patients with primary immunodeficiency disease

Antibody deficiency is the most frequently encountered primary immunodeficiency disease (PIDD) and patients who lack the ability to make functional immunoglobulin require life-long replacement therapy to prevent serious bacterial infections. Human serum immunoglobulin manufactured from pools of donated plasma can be administered intramuscularly, intravenously or subcutaneously. With the advent of well-tolerated preparations of intravenous immunoglobulin (IVIg) in the 1980s, the suboptimal painful intramuscular route of administration is no longer used. However, some patients continued to experience unacceptable adverse reactions to the intravenous preparations, and for others, vascular access remained problematic. Subcutaneously administered immunoglobulin (SCIg) provided an alternative delivery method to patients experiencing difficulties with IVIg. By 2006, immunoglobulin preparations designed exclusively for subcutaneous administration became available. They are therapeutically equivalent to intravenous preparations and offer patients the additional flexibility for the self-administration of their product at home. SCIg as replacement therapy for patients with primary antibody deficiencies is a safe and efficacious method to prevent serious bacterial infections, while maximizing patient satisfaction and improving quality of life.

Systemic Epstein-Barr virus infection associated with membranous nephropathy in children

Epstein-Barr virus (EBV) infection can cause diverse renal manifestations ranging from microscopic hematuria to acute renal failure. Membranous nephropathy (MN) is an uncommon and usually secondary cause of nephrotic syndrome in children, and has been reported after chronic infections and antigenemia. We report two pediatric cases of secondary MN associated with acute and chronic systemic EBV infection. Patient 1 had a liver transplant for cirrhosis due to biliary atresia and developed chronic EB viremia. Membranous nephropathy occurred 3 years later and with aggressive therapy has partially subsided, in temporal association with a drop in blood EBV PCR levels. The other patient had a primary immunodeficiency and developed a lymphoproliferative disorder attributed to EBV. Nephrotic syndrome developed at initial presentation and was associated with MN on biopsy. The patient cleared the virus from blood, which was associated with eventual resolution of the MN. We postulate that EB viremia in patients lacking a fully competent immune system, but without a renal allograft, may create a susceptible environment for chronic systemic EB antigenemia that can then lead to immune-complex MN in the kidney. The association of EBV with renal histological changes consistent with MN has been suggested but not directly described before.

Persistent perianal abscess in early infancy as a presentation of autoimmune neutropenia

Autoimmune neutropenia of infancy is a primary, usually self-limiting, antineutrophil autoimmune phenomenon seen in infancy and early childhood. These infants are at a higher risk of infection, and early detection, particularly with the availability of newer therapeutic options such as hematopoietic growth factors, can allow close follow-up and, if needed, treatment. We report two infants with autoimmune neutropenia who presented with a persistent perianal abscess, which has not been documented previously in this population.

Pharmacokinetics and tolerability of a new intravenous immunoglobulin preparation, IGIV-C, 10% (Gamunex, 10%)

BACKGROUND AND OBJECTIVES

A new intravenous immunoglobulin (IGIV) process has been developed that integrates efficient inactivation of enveloped virus, using caprylate, with immunoglobulin G (IgG) purification and caprylate removal by column chromatography. Two clinical studies were conducted to compare the pharmacokinetics of the new product, IGIV-C, 10% (Gamunex, 10%), formulated with glycine, with the licensed solvent-detergent (SD)-treated intravenous immunoglobulin IGIV-SD, 10% (Gamimune N, 10%), formulated with glycine, and IGIV-C, 5%, formulated with 10% maltose.

MATERIALS AND METHODS

Both studies were randomized, multicentre crossover trials of 18 and 20 (respectively) adult patients with primary humoral immune deficiency in which patients received one IGIV product for three consecutive periods (3-4 weeks) before crossing over to the other product. Pharmacokinetic parameters were determined after the third infusion of each product.

RESULTS

IGIV-C, 10% was bioequivalent to IGIV-SD, 10%, with half-lives (t1/2) of 35 and 34 days, respectively. IGIV-C, 5%, was bioequivalent to IGIV-C, 10%, with t1/2 of 35 and 36 days, respectively. The products had comparable safety profiles.

CONCLUSIONS

The pharmacokinetic profiles observed in these trials indicate that IGIV-C, 10% may replace, and be administered in a manner similar to, IGIV-SD, 10%.

Pleiotropic defects in lymphocyte activation caused by caspase-8 mutations lead to human immunodeficiency

Apoptosis is a form of programmed cell death that is controlled by aspartate-specific cysteine proteases called caspases. In the immune system, apoptosis counters the proliferation of lymphocytes to achieve a homeostatic balance, which allows potent responses to pathogens but avoids autoimmunity. The CD95 (Fas, Apo-1) receptor triggers lymphocyte apoptosis by recruiting Fas-associated death domain (FADD), caspase-8 and caspase-10 proteins into a death-inducing signalling complex. Heterozygous mutations in CD95, CD95 ligand or caspase-10 underlie most cases of autoimmune lymphoproliferative syndrome (ALPS), a human disorder that is characterized by defective lymphocyte apoptosis, lymphadenopathy, splenomegaly and autoimmunity. Mutations in caspase-8 have not been described in ALPS, and homozygous caspase-8 deficiency causes embryonic lethality in mice. Here we describe a human kindred with an inherited genetic deficiency of caspase-8. Homozygous individuals manifest defective lymphocyte apoptosis and homeostasis but, unlike individuals affected with ALPS, also have defects in their activation of T lymphocytes, B lymphocytes and natural killer cells, which leads to immunodeficiency. Thus, caspase-8 deficiency in humans is compatible with normal development and shows that caspase-8 has a postnatal role in immune activation of naive lymphocytes.

Anti-CD20 monoclonal antibody (rituximab) therapy for acute cardiac humoral rejection: a case report

Humoral or antibody-mediated rejection in cardiac transplant recipients is mediated by donor-specific cytotoxic antibodies and is histologically defined by linear deposits of immunoglobulin and complement in the myocardial capillaries. Antibody-mediated rejection often is accompanied by hemodynamic compromise and is associated with reduced long-term graft survival. Standard immunosuppression, designed to target T cell immune function, is largely ineffective against this B cell-driven process. Current treatment options for humoral rejection are limited by a lack of specific anti-B cell therapies. We present the case of a 50-year-old woman with hemodynamically significant humoral rejection resistant to steroids, cyclophos-phamide, and plasmapheresis who responded to the addition of anti-CD20 monoclonal antibody therapy (rituximab). One year posttransplant, the patient is rejection-free, with normal left ventricular systolic function and coronary arteries.

Treatment of post-transplant lymphoproliferative disease with induction chemotherapy followed by haploidentical peripheral blood stem cell transplantation and Rituximab

Management of monoclonal lymphoproliferative disease following stem cell transplantation is difficult and previous attempts to eradicate tumor using chemotherapy or radiation therapy alone have not been successful. We report successful early eradication of an EBV negative, B cell non-Hodgkin's lymphoma in a child who received a T cell-depleted, maternal haploidentical bone marrow transplant for severe combined immunodeficiency disease. Our treatment strategy involved combining conventional induction chemotherapy with re-transplantation using the paternal donor as a source of peripheral blood stem cells, followed by treatment with anti-CD 20 monoclonal antibody (Rituximab). This strategy exploits the potential graft-versus-tumor activity of the mature T cells in the graft, while providing a source of stem cells to confer long-term immune function. The administration of Rituximab in the early post-transplant course may provide additional anti-tumor activity without affecting the new stem cell compartment.

Distinct T cell developmental consequences in humans and mice expressing identical mutations in the DLAARN motif of ZAP-70

The protein tyrosine kinase, ZAP-70, is pivotally involved in transduction of Ag-binding signals from the TCR required for T cell activation and development. Defects in ZAP-70 result in SCID in humans and mice. We describe an infant with SCID due to a novel ZAP-70 mutation, comparable with that which arose spontaneously in an inbred mouse colony. The patient inherited a homozygous missense mutation within the highly conserved DLAARN motif in the ZAP-70 kinase domain. Although the mutation only modestly affected protein stability, catalytic function was absent. Despite identical changes in the amino acid sequence of ZAP-70, the peripheral T cell phenotypes of our patient and affected mice are distinct. ZAP-70 deficiency in this patient, as in other humans, is characterized by abundant nonfunctional CD4(+) T cells and absent CD8(+) T cells. In contrast, ZAP-70-deficient mice lack both major T cell subsets. Although levels of the ZAP-70-related protein tyrosine kinase, Syk, may be sufficiently increased in human thymocytes to rescue CD4 development, survival of ZAP-70-deficient T cells in the periphery does not appear to be dependent on persistent up-regulation of Syk expression.

Thalidomide in children undergoing bone marrow transplantation: series at a single institution and review of the literature

Thalidomide has one of the most notorious drug histories because of its teratogenicity. Its widespread use in the 1960s led to a worldwide epidemic of phocomelia in inborns; this in turn led to its complete ban in most of the world. However, it has now been licensed for selected indications including graft-versus-host-disease (GVHD) after bone marrow transplantation, wasting associated with tuberculosis and human immunodeficiency virus infection, and leprosy. Little is known, however, about its use in children in these settings. Therefore, we report our experience and review the literature on thalidomide in children for GVHD after bone marrow transplantation. We studied 6 patients, 2 with chronic GVHD, 2 with acute GVHD, and 2 with acute GVHD progressing into chronic disease. One patient with chronic GVHD had a complete response, whereas the other had a partial response. Side effects consisted primarily of sedation and constipation, which are reported previously and well known side effects. None had neuropathy. One patient had rash, eosinophilia, and early pancreatitis that began shortly after initiation of thalidomide, persisted, and resolved only after discontinuation of thalidomide. Eosinophilia and pancreatitis are both previously unreported side effects or associated findings of thalidomide treatment. Review of the literature reveals three major studies of thalidomide in GVHD; of these two included children and adults together, and one in which age range of patients was not mentioned. In addition, four series of children receiving only thalidomide are reported. These series contained 1 to 14 patients each. Results show efficacy in at least 50% of children with chronic GVHD and little or no efficacy in children with exclusively acute GVHD. Side effects are similar to those reported in adults and consisted mostly of sedation and constipation, both of which subsided over time and resolved after discontinuing the drug. We speculate on the reasons for which thalidomide is more effective in chronic, compared with acute, GVHD in children, and make recommendations for future study.

Alpha 1-antitrypsin deficiency in a child with X-linked lymphoproliferative disease

An 18-month-old white male infant with X-linked lymphoproliferative disease was evaluated for persistent hepatic dysfunction following primary Epstein-Barr virus infection. A liver biopsy revealed cirrhosis with a dense mononuclear cell infiltrate. These findings were confounding because cirrhosis is not a typical finding in either normal or immunodeficient individuals following infection with Epstein-Barr virus. An alpha 1-antitrypsin level obtained shortly after biopsy was spuriously within the lower limits of the physiologic range. Further investigation demonstrated a homozygous Z phenotype, the classic protease inhibitor variant described in alpha 1-antitrypsin deficiency. A repeat liver biopsy confirmed the presence of a second hereditary disease. This is a unique concurrence of two uncommon genetic disorders.

CD4+ memory T cells are the predominant population of HIV-1-infected lymphocytes in neonates and children

BACKGROUND

CD4+ memory T cells express CD45RO and are the principal viral reservoir in HIV-infected adults. In infants and children, CD45RO T cells comprise the minority of the CD4+ T-cell population. The majority of blood CD4+ T cells are naive, expressing CD45RA.

OBJECTIVE

To determine the developmental stage at which pediatric CD4+ T cells become susceptible to HIV-1 infection in vivo by determining which T-cell population harbors HIV-1 proviral DNA.

DESIGN

A prospective, cross-sectional analysis of peripheral blood CD8+ T cells, CD45RA, or CD45RO CD4+ T cells obtained from 10 HIV-infected neonates and children were analysed for provirus.

METHODS

Semi-quantitative polymerase chain reaction methods were used to detect HIV-1 proviral DNA within purified lymphocyte populations selected using immunoaffinity magnetic microspheres.

RESULTS

CD8+ T cells harbored no detectable HIV-1, indicating that infection of common thymocytes does not contribute to the population of infected blood T cells. In five children and two of the five neonates, the CD4+ CD45RO memory T lymphocytes contained 10-100-fold greater numbers of infected cells than the CD4+ CD45RA naive T-cell population. Three neonates, who exhibited rapid disease progression, demonstrated high proviral levels in their CD4+ CD45RA T cells. The normal age-related predominance of CD4+ CD45RA T cells was preserved independent of CD4+ T-cell attrition.

CONCLUSIONS

The majority of HIV-1-infected blood CD4+ T cells in infants and children are restricted to the small population of terminally differentiated CD4+ CD45RO memory T cells. Neonates with rapid CD4+ T-cell attrition display high levels of provirus in their CD4+ CD45RA T-cell population.