Neonatal sepsis: Pathogenesis and supportive therapy

Neonatal Sepsis: Pathogenesis and Supportive Therapy Baruch Wolach Bacterial infections remain an important cause of neonatal mortality and morbidity. Pathogenesis of the neonate's predilection to infection are multifactorial. Factors directly attributable to the infant include humoral, phagocytic, and cellular deficiencies. Septic neonates may have reduced neutrophil storage pools that cause profound neutropenia. Both correlate with poor prognosis. Antibiotic administration is mandatory in neonatal sepsis. Supplementary treatments may be useful. Granulocyte transfusions, when available, provide neutrophils, improving the neonate's neutrophil count and neutrophil function. The efficacy of intravenous immunoglobulin ( M G ) is questionable because the prophylactic and therapeutic administration of IVIG fails to reduce the incidence of bacterial infections or affect the overall survival rate. Hyperimmune preparations seem to be more effective. The administration of granulocyte colony-stimulating factor induces myeloid progenitor proliferation, enhances the neutrophil storage pool, produces neutrophilia, and improves neutrophil function. More extensive, well-designed, and carefully control trials are needed to determine the benefit of supportive therapies for neonatal sepsis. Copyright 9 1997 by W.B. Saunders Company ewborn infants, particularly those born N prematurely, are p r o n e to develop overwhelming infections in response to bacterial pathogens. Bacterial infections are an important cause of neonatal mortality and morbidity, with an incidence of 1 to 10 per 1,000 live births. 1'2 However, with improved neonatal care and salvage of preterm and low birth weight infants, the incidence o f infection has increased to 6% in very low birth weight (VLBW) infants. 2'3 In those who require prolonged hospital care, the incidence of infections o f the nosocomial type is 11% to 25%.1'2'4 Early diagnosis and initiation of antibiotic therapy with appropriate m a n a g e m e n t of metabolic and respiratory problems can greatly affect the o u t c o m e of neonatal sepsis. For VLBW infants who survive the early causes of death (extreme prematurity, congenital malformations, respiratory distress syndrome), late-onset sepsis becomes a critical threat to survival. The percentage of deaths attributed to infection increases with age. 4 T h e mortality rate of neonaFrom the Department of Pediatrics & the Pediatric Hematology Unit, Meir General Hospital, Sapir Medical Center, Kfar Saba & the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. Address reprint requests to Baruch Wolach, MD, Department of Pediatrics, Meir General Hospital, Sapir Medical Center, 44281, Kfar Saba, Israel. Copyright 9 1997 by W.B. Saunders Company O146-0005/97/2101-0005505. 00/0 28 tal sepsis varies according to the organism (40% gram-negative, 28% fungal), 4 the immunocompetency of the host, and associated complications. 1-4 The pathogenesis of the neonate's predilection to infection are multifactorial. Obstetric factors, 5'6 monitoring devices, and therapeutic procedures in the ICU may trigger neonatal infections. 7,s Factors directly attributable to the infant, including deficiencies in the various arms o f the i m m u n e system, play major roles in their predilection to infection. A defective reticuloendothelial system, lack of adequate humoral immunity, such as low immunoglobulin and complement levels and functions, impaired cellular and phagocytic activities, have all been shown to be present in neonates. 9-n The basic treatment of neonatal sepsis includes prophylactic measures for the prevention of cross-infection, meticulous umbilical cord and catheter care, 12'1~ and antibiotic administration. 1-4'14 A variety of supplementary therapies may be useful in various clinical settings. Granulocyte transfusions, 15'16 exchange transfusions, 17'1s high-dose M G 19-21 and recently new cytokines 22-24have all been used for prophylaxis and treatment of bacterial neonatal sepsis. This article will update the state of the art of the supportive treatments proposed for bacterial sepsis of the newborn. F o r better understanding ~ of the rationale of the various treatment modal- Seminars in Perinatology, Vol 21, No 1 (February), 1997: pp 28-38 Neonatal Sepsis ities, relevant aspects in the pathogenesis of the disease will be discussed. M y e l o i d K i n e t i c s a n d N e u t r o p e n i a in the Newborn Infant Neutrophils provide a fundamental defense against bacterial infection. Both a reduced number and abnormal function of the neonate's neutrophils contribute to their i m m u n o c o m p r o mised state and their susceptibility to infection. Neutropenia, defined as an absolute neutrophil count less than 2.0 • 10/L, 25 is found in up to 35% of preterm newborn infants. 25'26 Fetal neutrophil numbers have been reported to increase from 0.2 • 109/L at 18 weeks of gestation to 0.8 • 109/L at 31 weeks of gestation, reaching 8.5 • 109/L at the full-term period. 26 In adults, the neutrophil storage pool (NSP), consisting of metamyelocytes, bands and polymorphonuclear neutrophils (PMNs), contains more than 14 times the n u m b e r of neutrophils in the circulating blood, '27 but animal studies suggest that in the neonate this reserve contains only about two times the circulating neutrophil pool. 2s Thus, during bacterial infection, the neonatal neutrophil reserve becomes rapidly exhausted, 29 rendering the newborn neutropenic with an inadequate supply of neutrophils to combat infections. Furthermore, neonatal stem cells may be unable to increase their rate of proliferation during infection, s~ NSP depletion is also a p o o r prognostic sign in bacterial sepsis, sl's'~ However, infection is not the primary cause of neonatal neutropenia. In one study, 3s less than half of the neonatal neutropenic episodes could be attributed to infections per se. The majority of noninfectious neutropenic episodes were related to specific perinatal events or were of unknown cause. In addition, infants weighing less than 2,500 g were more likely to have neutropenia than term infants. However, when infection is present, neutropenia has been found to be associated with a p o o r prognosis. 15's~'s'~ In these cases, the neutropenia may reflect increased margination o f circulating cells or depletion of the neutrophil storage pool. The Phagocytic, Humoral, and Cellular Arms of the Newborn Infant During neonatal sepsis, even adequate numbers of PMNs may be insufficient because of their 29 significant dysfunction. Many neonatal phagocytic functions have been found to be impaired. Table 1 summarizes studies in our laboratory of neutrophil function in healthy full-term newborn infants and adults. 3~-36Mobilization of neutrophils from the circulation involves adhesion to endothelium via molecules called selectins, and response to a chemotactic stimulus. 37 Chemotactic activity of neonatal neutrophils compared with that of adults is impaired (Table 1). 34'35'~8's9 This may result from abnormalities in cell surface adhesion molecules, 4~ decreased actin polymerization, 41 increased cell skeleton rigidity, 42 or alteration of m e m b r a n e fluidity, s4 Impaired surface m e m b r a n e expression of C3bi receptors has also been reported, as The decreased bactericidal activity of neonatal neutrophils (Table 1) is likely secondary to diminished opsonic activity, leading to impaired phagocytosis. Oxidative metabolic abnormalities have also been reported in neonatal phagocytes with a discordance between superoxide generation, which is increased (Table 1), and hydroxyl radical generation, which is diminished. 44 In addition, Shigeoka et al reported that oxidative responses from stressed neonatal neutrophils are defective when c o m p a r e d with neutrophils from healthy, unstressed newborns. 4r' A major function of the c o m p l e m e n t system is to promote opsonization and subsequent neutrophil phagocytosis. Newborn infants, particularly those born prematurely, have a severe quantitative and qualitative impairment of the c o m p l e m e n t system, s6'46This could explain their impaired neutrophil bactericidal activity. This defect can be corrected in vitro in most newborns by incubating their phagocytes with the sera of healthy adult donors, s6 indicating that a humoral defect is responsible for the dimished phagocytic capacity (Table 1). Similarly, opsonic immunoglobulins have also been found to be significantly reduced in preterm infants. 47 This too may affect opsonization and subsequent phagocytosis. Additionally, the lymphocytes o f neonates lack B-cell m e m o r y and the ability to p r o d u c e a secondary i m m u n e response. 11 Certain antigens, such as bacterial polysaccharides, fail to stimulate an adequate antibody response in newborn i n f a n t s , ll'4s T h e r e is also evidence of altered neonatal Tcell function as manifested by decreased cutaneous hypersensitivity, decreased efficacy of allo- 30 Baruch Wolach Table 1. Neutrophil Functions in Healthy Newborn Infants and Adults *Chemotaxis (no. cells) *Random migration (no. cells) t N e t chemotaxis (no. cells) SfMLP-stimulated superoxide production (nM/min/106 cells) SPMA-stimulated superoxide production (nM/min/106 cells) Bactericidal activity with autologous serum (log decrease) w Bactericidal activity with Ilhomologous sera (log decrease) w Full-Term Infant Adult P Value 53 • 18 (n = 30) 30 + 14 (n = 30) 25 -+ 11 (n = 30) 108 • 19 (n = 40) 34 +__14 (n = 40) 70 +_ 14 (n = 40) <.001 2.0 _+ 0.6 (n = 30) 1.4 + 0.4 (n = 40) <.01 6.4 +_ 2 (n = 40) 6.8 +_ 1.5 (n = 40) NS 0.7 +_ 0.2 (n = 20) 2.3 -2_ 0.6 (n = 20) <.001 11.3 + 0.6 (n = 15) #0.3 + 0.3 (n = 20) <.001 NS <.001 * Chemotaxis and random migration were assessed using a 48-well chemotaxis microchamber. The chemoattractant fMLP (Formyl-Methionyl-Leucyl-Phenylalanine) or suspending medium was placed in the bottom wells and the cells in the upper wells, separated by a polycarbonate filter sheet of 3-urn holes. After incubation for 60 min at 37~ in a humidified atmosphere, the filter was removed, wiped, stained and the number of migrating cells was scored microscopically. t Net chemotaxis was derived by subtracting the number of randomly migrating cells (in the absence of tMLP) from that of cells migrating under chemotactic stimulus (tMLP 10.7 M). Superoxide production was measured as superoxide dismutase-inhibitable reduction of ferricytochrome C in a dual beam recording spectrophotometer, in resting and in activated neutrophils with fMLP or PMA (phorbol myristate acetate). wLog decrease of E. coli colonies after 90-minute incubation with PMNs in the presence of either autologous or homologous serum. II Homologous sera: Pool of sera of healthy adults or newborn infants. Neonatal neutrophils plus adult homologous sera. # Adult neutrophils plus neonatal homologous sera. Data from references 34 through 36. g r a f t r e j e c t i o n , a n d r e d u c e d rates o f graft-versushost disease after cord blood transplantation. ~ T-cells d i s p l a y i m m a t u r i t y o f t h e i r s u r f a c e m a r k ers a n d in t h e i r ability to r e s p o n d to c h a l l e n g e s . 49 T-cell cytotoxicity is also d i m i n i s h e d in t h e n e o n a t e , a n d n e o n a t a l n a t u r a l k i l l e r cells (NK) a r e i m p a i r e d in t h e i r cytotoxic capacity. 5~ A d d i t i o n ally, m a n y d e f e c t s in c y t o k i n e p r o d u c t i o n have b e e n r e p o r t e d in n e o n a t e s . 51'~2 T h e s e f u n c t i o n a l d e f i c i e n c i e s m a y e n h a n c e t h e n e o n a t a l susceptibility to c o n g e n i t a l a n d p e r i n a t a l viral, f u n g a l , a n d p r o t o z o a n infections. Therapeutic Considerations S u p p o r t i v e t h e r a p y with g r a n u l o c y t e transfusions, e x c h a n g e transfusions, i n t r a v e n o u s immune globulin (MG) and granulocyte colony s t i m u l a t i n g f a c t o r (G-CSF), have all b e e n u s e d in a n e f f o r t to i m p r o v e t h e q u a n t i t a t i v e a n d qualitative d e f e c t s o f n e o n a t a l i m m u n i t y . Neutrophil Transfusion and Exchange Transfusion as Adjunctive Therapy for Neonatal Sepsis T h e q u a n t i t a t i v e a n d qualitative a b n o r m a l i t i e s in n e o n a t a l m y e l o i d p r e c u r s o r s a n d c i r c u l a t i n g PMNs s u g g e s t t h a t n e u t r o p h i l t r a n s f u s i o n s m i g h t b e b e n e f i c i a l as a d j u n c t i v e t h e r a p y f o r n e o n a t e s with o v e r w h e l m i n g sepsis. PMNs t r a n s f u s i o n s m i g h t i m p r o v e survival o f septic n e o n a t e s by increasing the number of circulating neutrophils, t h e r e b y e n h a n c i n g all p h a g o c y t i c f u n c t i o n s . I n a d d i t i o n , t h e use o f e x c h a n g e t r a n s f u s i o n c o u l d remove endotoxins and improve the neonate's i m p a i r e d o p s o n i c capability. It is difficult to assess t h e p u b l i s h e d l i t e r a t u r e o n t h e use o f g r a n u l o c y t e transfusions. M a n y studies i n c l u d e o n l y a small n u m b e r o f p a t i e n t s . T h e s e studies d i f f e r in t h e i r c r i t e r i a f o r p a t i e n t s e l e c t i o n , m e t h o d s o f o b t a i n i n g P M N s (with varia b l e yields o f P M N s ) , a n d t r a n s f u s i o n p r o t o c o l s . Neonatal Sepsis 31 Table 2. Granulocyte Transfusion in Septic Newborn Infants Author Laurenti ~s Cairo~4 Christensen 31 Baley~5 Wheeler~6 Cell Preparation PMNs PMNs PMNs PMNs PMNs (leukapheresis) (leukapheresis) (leukapheresis) (buffy coat) (buffy coat) Dosage 0.5-1 X 10 9 0.5-1 X 109 0.7 x 109 0.35 X 109 0.3-0.7 X 10 9 The patient outcomes were also significantly different (Table 2). In a n o n r a n d o m i z e d retrospective study, Laurenti et a153 reported successful results in treating 20 neonates with sepsis on two to 15 occasions with 20 m L / k g of leukocyte preparations obtained by continuous flow filtration leukapheresis. The study results were impressive; the mortality rate was 10% in the transfused group versus 28% in the nontransfused group. The survival rate was particularly high in the subgroup of infants less than 1,500 g. Cairo et a154 treated 13 patients with PMNs transfusion and had a 100% survival rate as compared with 60% in 10 nontransfused newborns. However, in this study, patients were not required to undergo both neutropenia and NSP depletion to be included, and only some had positive bacterial cultures, factors which together adversely affect the prognosis more than when there is only neutropenia, s~'s~ Obviously, the criteria for patient selection are critical in the analysis of results in these studies, particularly when the n u m b e r of participants is small. In a controlled, randomized study, Christensen et al sx showed evidence suggesting the benefit of PMN transfusion obtained by continuous flow centrifugation leukapheresis, in neutropenic, storage pool-depleted, septic neonates. The seven newborns who received a single neutrophil transfusion experienced a 100% survival, whereas the survival rate was only 11% in a similar untransfused NSP-depleted control group. In contrast, in a n o t h e r randomized prospective study, Baley et a155 reported on the transfusion of buffy coat cells stored for up to 24 hours before use in the treatment o f neonatal sepsis. All patients were neutropenic, but only 36% had NSP depletion. In this study, no significant difference in survival rates between treated and untreated patients were found. Similarly, Wheeler Patients Transfused Survival Rate 20 13 7 10 4 90% 100% 100% 60% 50% Control Group 18 10 9 7 5 Survival Rate 72% 60% 11% 71% 40% et a156 reported no beneficial effect o f buffy coat transfusions on the survival o f neutropenic, NSPdepleted septic neonates, and there was no increase in peripheral blood neutrophil count with these transfusions. T h e r e are also hazards associated with granulocyte transfusions. These include the possibility o f fluid overload, leukocyte sequestration in the lung causing respiratory distress and hypoxia, graft-versus-host disease, sensitization to d o n o r erythocyte and leukocyte antigens, and the potential risk for transmission o f hepatitis, cytomegalovirus, the h u m a n immunodeficiency virus, and other infectious diseases. ~5a6 Thus, because granulocytes transfused are short-lived (about 6 hours) and donors for PMN acquisition are difficult to recruit, this therapy should be reserved only for severely ill neonates who have neutropenia and evidence of NSP depletion. Exchange transfusion, with fresh blood stored at 4~ for less than 12 hours, has been used in severely septic neonates with sclerema. Improvem e n t in this clinical condition, with reduction o f apneic episodes, hypoxemia, and mortality has been r e p o r t e d J 7'~8'57 T h e treatment induced an increase o f immunoglobulin and c o m p l e m e n t levels, improving the neonate's plasma opsonic activity. 1s'57 T h e transfusion of " f r e s h " blood units also has been reported to increase the recipient's neutrophil c o u n t and improve their phagocytic functionJ a Intravenous Immune Globulin (IVIG) for the Prevention and Treatment of Neonatal Sepsis It has been shown that newborns, particularly prematures, may have both a quantitative and a qualitative immunoglobulin deficiency. 47'4s T h e bulk of IgG crosses the placenta in the last trimester o f pregnancy, thus the IgG level of pre- 32 Baruch Wolach m a t u r e infants is considerably lower than that of term infants. Moreover, i m m u n o g l o b u l i n levels of n e w b o r n infants decline further after birth 47 which is associated with p o o r response to various antigenic stimuli. 11'48 T h e administration of immunoglobulins has b e e n r e p o r t e d to result in neutrophil c o u n t recovery and increased concentrations of serum IgG of all subclasses. ~s F u r t h e r m o r e , the total hemolytic c o m p l e m e n t activity and the opsonizafion of g r o u p B streptococci has also b e e n rep o r t e d to be significantly increased. 58 Acunas et a159 c o m p a r e d the immunological effect of M G with flesh frozen plasma (FFP) infusions in p r e t e r m and t e r m newborn infants with p r o b a b l e sepsis. After infusion of M G , there were significantly elevations in the total serum IgG, all IgG subclasses, a n d in the complem e n t c o m p o n e n t C4. In contrast, FFP infusion did n o t change the total IgG and IgG subclasses, but significantly increased levels of IgA, IgM, and C4. Studies that evaluated the use of M G in neonatal infections are problematic; they were different designs, often nonblinded, with the inadequate controls a n d inappropriate m e t h o d s of statistical analysis. Further, most studies lack evaluation of pathogen-specific antibody levels in both the IVIG preparations and in patients, differ in the source o f immunoglobulins, in the dosing schedule (one to seven doses), a n d in the dose administered (120 to 1,000 m g / k g ) . Additionally, they lack careful recording of short- and long-term assessments as well as detailed o u t c o m e records. Because of these major differences a m o n g the published studies, the data should be viewed with caution. Detailed information of various studies regarding the role of 1VIG in preventing bacterial neonatal sepsis is shown in Table 3. In the largest multicenter study published to date, Fanaroff et a121 r e p o r t e d no overall reduction in proven bacterial infections or in the mortality rate of neonatal sepsis after M G administration. Similar re- Table 3. Results of Standard IVIG in the Prevention of Neonatal Infection in Preterm Newborns Author Study Design Dosage & Schedule No. of Patients M G vs Control Fanaroff21 Randomized, 700-900mg/kg/dose 1,204/1,212 placebo-controlled days 1, 15, 30, q14 (<l,500g)* days until infants weighted 1,800 g Baker 63 Randomized double- 500 mg/kg/dose 287/297 blind, placebodays 3-7, 10-14 and (500-1,750g)* controlled q14 days (total X5) Weisman 6~ Double-blind, 500 mg/kg/dose • 368/376 placebo-controlled 1 (500-2,000g)* Magni 61 Randomized double- 500 mg/kg/dose 115/120 blind, placebodays 0, 1, 2, 3, 17, (GA <32 weeks) controlled 31 Busse164 Double-blind, 1000 mg/kg/dose 61/65 placebo-controlled days 1, 2, 3, 4, 15 (<l,300g)* Chirico 65 Randomized 500 mg/kg/dose 43/40 once a week • (550-1,500g)* Stabile 62 Randomized 500 mg/kg/dose 46/48 days 1, 2, 3, 7, 14, (870-1,790g)* 21, 28 Clapp 66 56/59 Randomized, 500-1,300 m g / k g / double-blind dose day 1, then (600-2,000g)* placebo-controlled to maintain IgG > 700 mg/dL Haque 67 100/50 Randomized 120 mg/kg/dose days 1 or 1, 8 (<1,500g)* * Birth weight. Incidence of SepsisTreated vs Untreated P Value 17.3% 19.1% NS 24% 3.1% 35% 4.0% Relative risk 0.7, 95% confidence interval NS 31% 38% NS 15% 25% <.04 5% 20% <.05 13% 8% NS 0% 12% <.04 4% 16% <.005 Neonatal Sepsis 33 Table 4. Results of Standard IVIG Therapy in Newborn Infants With Sepsis Author Weisman 6~ S i d i r o p o u l o s 69 F r i e d m a n 71 Haque 7~ Study Design Dosage & Schedule Randomized, 500 mg/kg/dose • 1 double-blind, (Sandoglobulin) t placebo-controlled Randomized 500-1,000 mg/kg/dose daily • 6 (Sandoglobulin) t Historical control 800 mg/kg/dose • 1 Up to 4 times until neutropenia resolved (Sandoglobulin) t Randomized, 250 mg/kg/dose daily double-blind, • 4 placebo-controlled (Pentaglobulin) t No. of Patients M G vs Control Mortality Rate (%) P Value 14/17 (500-2,000 g)* 0% 29% <.05 20/15 (770-3,860 g)* 10% 27% .16 12/12 (GA: 24-42 wk) 17% 58% .09 21/23 (850-1,700 g)* (only neonates with proven infection) 5% 17% .35 * Birth weight. t Trade name. sults have been reported by Weisman, 6~ Magny 61 and Stabile. 6~ In contrast, Baker, 63 Bussel, 64 Chirico, 65 Clapp, 66 and Haque 67 reported a protective role for M G in the prevention of sepsis, although the incidence of necrotizing enterocolitis was unaffected. Weisman et al were unable to show a prophylactic effect of a single dose of IVIG on neonates with late-onset sepsis. 68 However, Baker et a163 administered repeated doses of IVIG and showed significant improvement in the prevention of neonatal sepsis in VLBW infants. The IVIG infusion did not affect the incidence of sepsis in neonates weighing more than 1,500 g at birth. Standard IVIG have also been tried in the treatment of established bacterial sepsis of the newborn (Table 4). No definite improvement in neonatal survival has been shown. However, the n u m b e r of patients studied has been insufficient, and antibody analysis for specific bacteria has not been provided for the different lots of Sidiropoulos et a169 reported no overall benefit of IVIG in the treatment o f septic newborns. Nevertheless, the survival o f neonates u n d e r 2,500 g was significantly improved. Long-term follow-up for 1 to 4 years showed no abnormalities in psychomotor development, somatic growth, and immunological evaluations. In contrast, Haque et al 7~ found no significant benefit of WIG in septic neonates. Two patients in this series developed i m m u n e hemolysis with positive direct antiglobulin test (DAT), a finding which had been previously reported after M G infusions. 72'73 Finally, Friedman et al 7~ studied septic neutropenic neonates (PMN counts < 3 , 5 0 0 / uL) treated with WIG, and found rapid postinfusion recovery of the neutropenia. Recently, Lacy and Ohlson, using meta-analysis to determine the effectiveness of IVIG in the prevention and treatment o f sepsis of the newborn, concluded that there is no reduction of I V I G . 69-71 Standard WIG may not be o f benefit in the treatment of neonatal sepsis; h y p e r i m m u n e preparations seem to be much more effective. 2~ Because pathogens vary in the different populations studied, ~7~ it is o f critical importance that the IVIG lot used contains functional antibodies to the appropriate pathogens. 2~ Further, antibodies to specific pathogens may vary from lot to lot. 76 Therefore, it is important to ensure that a particular IVIG preparation contains the desired antibodies directed against a specific organism, according to the epidemiol- Weisman et al 6~ reported that survival was significantly improved at the seventh postinfusion day (P < .05), and was associated with postinfusion IgG serum concentrations of greater than 800 m g / d L . However, at 56 days, survival was not significantly different from that observed in the control group. It should be emphasized that in this study, IVIG was given as a single dose at more than 12 hours of life, and serum levels of postinfused WIG should have been inadequate at 56 days. m o r t a l i t y . 74 34 Baruch Wolach ogy of the area. WIG infusion has proved to be quite safe in neonates, and the incidence of adverse reactions seems to be m u c h less than that r e p o r t e d in adults, a9'2~Presently, there are insufficient data to assess the long-term effect of M G therapy in neonates. Studies suggest that the drug has a potential dose-related suppression on immunity, 77'7s but an adequate dosage o f M G should provide a protective elevation of serum antibody levels. Presently, M G cannot be considered the standard of medical care for the prevention or treatment of neonatal sepsis. Nevertheless, along with appropriate antibiotic therapy, the administration of selected lots of h y p e r i m m u n e IVIG could benefit the high-risk, small premature infants with r e c u r r e n t infections or those with overwhelming bacterial sepsis. Granulocyte-Colony Stimulating Factor (G-CSF) for Neonatal Sepsis H u m a n G-CSF is a low-molecular weight glycoprotein (18,000 daltons). 79 Administration of rhG-CSF increases myeloid progenitor proliferation, enhances the neutrophil storage pool, and induces early peripheral blood neutrophilia (within 24 hours after administration). T h e r e is a sustained increase in the peripheral neutrophil count secondary to stimulation of early bone marrow myeloid progenitor cells, zz's~ G-CSF has been shown to possess synergistic activity with IL3 in the initiation and proliferation of d o r m a n t murine pluripotent stem cells, sl When G-CSF or IL-3 is administered to neutropenic patients, increased neutrophil counts are usually observed, irrespective of the cause of the neutropenia, sz-s4 During states of increased demand, such as bacterial sepsis, G-CSF and IL-3 seem to be the major regulators of increased myeloid proliferation and maturation, s5 G-CSF also improves the function of mature neutrophils, s6 It enhances superoxide production in response to several agonists and specific binding of formyl-methionyl4eucyl-phenylalanine (fMLP) to mature neutrophils, promotes chemotaxis, and augments neutrophil cytotoxicity and antibody-dependent cellular cytotoxicity. Studies have shown that newborn infants produce less G-CSF than adults, s7-89 Further, it has been reported that supernatants from stimulated adult m o n o n u c l e a r cells have significantly higher levels of G-CSF and IL-3 than those found in stimulated neonatal cord monocytes. 9~ The investigators also reported an associated reduction of G-CSF and IL-3 mRNA transcripts in neonatal cells. These findings may have implications in the pathogenesis of neonatal cytopenias during sepsis. T h e r e is evidence that endogenous G-CSF is crucial in granulopoiesis in the neonatal period. 22'87-89 Increasing the neutrophil c o u n t is considered of great importance in neutropenic, NSP-depleted neonates, to improve the survival rate. 15'31'32 Thus, there are promising data regarding the potential role of rhG-CSF as an adjunctive therapeutic modality in the treatment of the neonate with neutropenia and sepsis. 22-24 In preliminary studies, we investigated the in vitro fMLP-stimulated chemotaxis and superoxide production of 25 healthy newborn infants, by priming the cells (15 minutes for chemotaxis and 2 hours for superoxide production) with recombinant rhG-CSF (Filgrastim, Roche) at 10 n g / m L or GM-CSF (Leucomax, Sandoz), and at 1 n g / m L . We found that net neutrophil chemotaxis was improved by 91% and 100% with GCSF and GM-CSF, respectively, in newborns with impaired net chemotaxis and by 17% and 33% in those with normal chemotaxis. The neutrophil superoxide production was also improved by 52% and 89%, respectively, with G-CSF and GMCSF. T h e r e are only a few clinical trials using GCSF therapy for neonates with sepsis. 29-24 Gillan et al, 22 in a randomized study, administered rhGCSF or placebo intravenously to 42 neonates (GA, 26 to 40 weeks) with presumed bacterial sepsis during the first 3 days of life. Complete blood counts, NSP, and C3bi expression were assessed. RhG-CSF at a daily dose of 1 to 10 # g / k g / d • 3 induced a significant increase of the peripheral neutrophil counts and the NSP. Also, the neutrophil C3bi expression increased significantly 24 hours after treatment with 10 # g / k g / d of G-CSF. The half-life of rhG-CSF was 4.4 + 0.4 hours, and n o toxicity was reported. T h e r e were no deaths in a follow-up of 15 months. Cairo et al, 23 in a randomized, placebo-controlled study, sought to determine the safety and the biological response to h u m a n rhuGM-CSF, given via 2-hour intravenous infusion to 20 VLBW neonates (500 to 1,500 g) for 7 days, at a dose of 5 to 10 # g / k g , Within 48 hours of Neonatal Sepsis administration, there was a significant increase in the circulating absolute neutrophil count, which continued for at least 24 hours after discontinuation of therapy. NSP and neutrophil C3bi expression also increased significantly. Additionally, in this study a significant increase of the absolute monocyte and platelet counts was observed after 7 days, suggesting a possible stimulatory effect of rhuGM-CSF (5.0 # g / k g twice per day) on monocyte production and on megakaryocytopoiesis in VLBW neonates. The rhuGM-CSF was well tolerated at all doses. Barak et al, 24 in a nonrandomized, open-label study design, treated 14 newborn infants (GA, 26 to 35 weeks) with suspected sepsis and neutropenia with IV rhG-CSF (5 # g / k g / d for 5 days). They showed a significant increase in bone marrow NSP and in the peripheral neutrophil count compared with an historical control group who did not receive rhG-CSF. No toxicity was recorded on follow-up. However, two neonates died, one of them presumably from an underlying condition rather than from sepsis. In another nonrandomized, non-placebocontrolled study, the effect of 5 / . t g / k g / d • 5 of rhG-CSF on critically ill neutropenic neonates (GA, 24 to 35 weeks) was evaluated. 91 If response was not achieved, the dose was increased to 10 # g / k g / d for an additional 5 days. Neutrophil and monocyte counts increased significandy, as did postinfusion G-CSF levels. In contrast, platelet counts decreased significantly after treatment, but this may have been induced by the primary disorder causing the neutropenia. The promising data from these studies highlight the potential role of rhG-CSF and rhuGMCSF in the treatment of newborn infants with overwhelming bacterial sepsis and neutropenia. Well-designed and carefully controlled trials using sufficient numbers of infants are needed to arrive at valid scientific conclusions. Acknowledgment I would like to t h a n k Professor Alvin Zipursky, w h o m I h a d t h e g o o d f o r t u n e to get to k n o w d u r i n g t h e formative years o f my professional training. Since t h e n , h e has r e p r e s e n t e d to m e the ideal synthesis o f t h e h u m a n i s t , t h e clinician, a n d t h e scientist. I w o u l d also like to t h a n k Professor J a c o b N u s b a c h e r for valiable discussions a n d advice d u r i n g t h e p r e p a r a t i o n o f this m a n u s c r i p t . 35 References 1. 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