**4. Immunoglobulins in neonates**

Immunotherapy was a common method of treatment of infectious diseases in the preantibiotic era with serotherapy being a popular approach to serious infections by use of antisera from large animals. This administration unfortunately was associated with the risk of anaphylaxis and serum sickness. Further on immune globulins obtained from pooled human plasma were used, but antibodies provided by these preparations always represented those common to the donor population, and intravenous injection of early human IgG preparations was complicated by severe allergic reactions (19). The next step was the purification of human immune globulins, and, currently there are multiple formulations of safe, pooled, human immunoglobulins tor the intravenous use.

84 Neonatal Bacterial Infection

of Ballow (17).

Escherichia coli by human granulocytes.

endothelial system

"Neutralize" toxin superantigen

immunity to the specific pathogen (18).

**4. Immunoglobulins in neonates** 

processing and/or T cell activation

Immunomodulation

Modulation of Fc receptor expression or affinity

Restoration of idiotype-antiidiotypic network

Inhibit cytokine/interleukin production/action

Enhancement of T cell suppressor function

**Table 1.** Mechanisms of action of intravenous immune globulins (17)

compared to controls with an effect even lasting ten days after the last infusion. These results suggest that specific IgG titers might be well indicative of its opsonic activity against

The complement-inhibitory activity of different IVIG preparations was assessed in vitro by measurement of the blocking of C1q-, C4-, and C3 deposition on solid-phase aggregated rabbit IgG by enzyme-linked immunosorbent assay (16). Results showed that IgM enrichment of IVIG preparations enhances their effect to prevent the inflammatory effects of complement activation. No IgG preparation negatively affected in vitro phagocytosis of

The mechanisms and effects of IVIGs are summarized in table 1 according to the description

 Fc receptor blockade of reticulo-endothelial cell system and mononuclear phagocytes Competitive interaction of IVIG with anti-platelet antibodies for FC receptor Soluble Fcγ receptors compete with membrane Fc receptors of the reticulo-

Inhibit B cell function and/or antigen-processing cells via Fc receptor

Soluble CD4 and CD8, soluble HLA Class II molecules that modulate antigen

Similar to most immunoglobins, the transplacental transport of IgG from the mother to fetus begins around 32 weeks of gestational age and increases until term. Premature infants born prior to 32 weeks gestation have profound IgG deficiencies. The major function of IgG in host defense is to opsonize bacteria and neutralize viruses. Levels of postnatal IgG are often low due to insufficient production by the immature neonatal immune system and catabolism of maternal IgG. Opsonic activity is also type-specific; therefore humoral immunity transferred to the neonate will be insufficient if the mother does not have

Immunotherapy was a common method of treatment of infectious diseases in the preantibiotic era with serotherapy being a popular approach to serious infections by use of antisera from large animals. This administration unfortunately was associated with the risk

Modify complement-dependent immune damage to tissue and cells

slime-producing *S*. *epidermidis* and might protect against bacteraemia.

The mortality rate of the preterm infants with septicaemia decreased from 44% in the infants receiving only antibiotics to 8% in the infants treated by IVIG together with the same antibiotic following administration of IVIG to preterm neonates (0.3 g/day in neonates below 1000 g; 0.5 g/day in neonates over 1000 g for 6 consecutive days). The IVIG preparation was well-tolerated by all newborns, and no adverse events were observed by monitoring blood gas analysis, clinical examination, monitoring of respiration, pulse and body temperature. Follow-up at an average age of 2.5 years showed no evidence of harmful effects of IVIG treatment in the neonatal period (20).

Cates et al. (21) evaluated the formation of specific and functional antibody in preterm infants born weighing less than 1500 g (mean 1088 g) and less than 32 weeks of gestational age (mean 28.8 weeks). In the presence of complement, the strain of coagulase negative staphylococcus used was opsonized by IgG antibody, and the strain of Escherichia coli by IgM. Geometric mean plasma levels of tetanus and diphtheria IgG antibody fell from birth to 4 months chronological age, but rose significantly by 9 months (approximately 2 months after the third dose of diphtheria, tetanus, pertussis vaccine). However, at 9 months they remained lower than the respective geometric mean levels in 9-month-old term infants. The preterm infants' mean plasma IgG staphylococcal opsonic activity fell from birth to 2.5 months, but by 9 months was comparable to that of term infants of the same age. Mean IgM opsonic activity for Escherichia coli was very low at birth in both preterm and term infants. It rose with chronological age, correlating with the rise in total IgM by 9 months the mean preterm and term infants' levels of IgM opsonic activity for E. coli were comparable.

Sasidharan (22) studied serially IgG levels postnatally in 42 infants of very low birth weight with gestational ages ranging from 23 to 31 weeks (mean birth weight 971 g). Eighteen infants (43%) had IgG levels of less than 100 mg/dl by a mean postnatal age of 71 days. The lowest level was found in a 700g infant with 22 mg/dl. In sixteen cases having cord blood IgG levels determined mean IgG values was 414 mg/dl. This had dropped to a mean of 140 mg/dl by 57 days. As expected, the lowest IgG levels postnatally were a reflection of the degree of prematurity and the length of postnatal age.

To proof the significance of low serum IgG and complement proteins in very low birth neonates Lassiter et al (23) measured serum IgG, C3, C4 and Factor B weekly by rate nephelometry in 15 neonates who developed proven nosocomial bacterial or candidal sepsis and 27 neonates who did not develop sepsis. In the first and second week of life the serum IgG of infected neonates was significantly lower (mean 295 and 270 mg/dl compared to 440 and 473 mg/dl, respectively. If the IgG was less than 350 mg/dl in the first week or less than 230 mg/dl in the second week, the relative risk of acquiring sepsis was greater than or equal to 5 (CI 95% 1.7 to 11.2).

Amato et al. (24) investigated serial IgG and IgM serum levels during the neonatal period in two groups of non-septic, preterm infants treated prophylactic with IVIG. Twenty-two very low birth weight infants (mean gestational age 31.8 weeks and mean birth weight 1265 g with a range of 1001 - 1500g) and 12 extremely low birth weight infants < 1000g (mean gestational age 28.6 weeks and mean birth weight 910g) received at random three standard doses of IVIG (0.5 g/kg/day) or IVIGAM (IgM enriched preparation) (5 ml/kg/day). IgG and IgM concentrations were assayed by rate nephelometry before treatment and at day 3, 5, 7, 14 and 28 of life. At any time IgG levels were higher in the IVIG very low birth weight group and no difference was observed in the extremely low birth weight group. IgM levels were higher at day 3 and 5 in the IVIGAM very low birth weight group and until day 7 in the extremely low birth weight group. The authors concluded that their findings indicate a wide range of IgG and IgM kinetics in the healthy premature infant.

Immunoglobulins in the Prevention and Treatment of Neonatal Sepsis 87

Prophylactic IVIG at a dose of 0.5 g/kg/day was given prospectively in 28 healthy preterm infants with a mean gestational age of 29.4 weeks and weight of 1,387g when they were 3-10 days old (29). Urine samples of the neonates were obtained for analysis on days 1, 2 and 3 following IVIG administration as well as 1 day before; and urinary nitrite levels were 2.77 +/- 1.66 µmol/mmol creatinine before IVIG administration; 4.33 +/- 3.88 µmol/mmol creatinine on the 1st; 3.77 +/- 2.73 µmol/mmol creatinine on the 2nd, and 3.64 +/- 3.28 µmol/mmol creatinine on the 3rd day. The increase of urinary nitrite levels was significant between before and after IVIG administration, thereafter levels did not differ significantly, suggesting that endogenous NO formation might play an important role in both the

**5. Use of immunoglobulins in the treatment of neonatal sepsis** 

Polyvalent immunoglobulin preparations are widely used as adjunctive therapy for sepsis or septic shock, but their efficacy is still a matter of debate. In 2007 Kreymann et al. (30) conducted a systematic review summarizing data on adults and neonates separately. In neonates, 12 trials (31-42) involving 710 patients were published. The estimate of the pooled effect on mortality was RR = 0.56 (95% CI 0.42– 0.74, p <.0001). Five studies (32,35,37,39,41) involving 352 patients were performed with the IgGAM preparation. The range of the cumulative dose of IgG was 0.57– 0.76 g/kg birth weight plus 0.09–0.12 g/kg birth weight IgA and 0.09–0.12 g/kg birth weight IgM. In this subgroup, the estimate of the pooled effect was RR = 0.50 (95% CI 0.34–0.73), equivalent to a 50% relative reduction in mortality (*p* < .0003). The study effects were comparable, and the test of heterogeneity was not significant. The study of El Nawawy (32) reported a significant reduction of mortality, the other four a positive trend (35,37,39,41). Polyvalent immunoglobulin preparations containing only IgG were evaluated in seven trials (31,33,34,36,38,40,42) involving 358 patients. The cumulative dose of IgG was 0.5–3 g/kg birth weight. The estimate of the pooled effect for this subgroup was RR = 0.63 (95% CI 0.42– 0.96), equivalent to a 37% relative reduction in mortality (p < .03). The test of heterogeneity was not significant. One study (38) reported a significant reduction in mortality, three studies reported a positive trend (31,33,42), and two studies (34,40) showed no effect. One trial (36) showed a duplication of mortality; one neonate died in the control group and two in the treatment group. Comparing the two treatment modalities, a small and insignificant difference in favour of IgGAM was observed (z = 0.80, p ≤ .42). Kreymann et al. (30) found a negative correlation with the severity of illness (as measured by the mortality of the control groups) in neonates; however, this held true only when the results reported by Chen (36) were included: In this study, an exceptionally low mortality in the control group was observed (1 of 28, respectively, 3.6%), which was doubled in the treatment group (2 of 28, respectively, 7.1%). If these results were omitted, the correlation lost significance. Additionally the authors found no correlation with the dosage

In adults and children, Kreymann et al. (30) found a strong trend in favour of IgGAM over IgG preparations with a 34% and 15% reduction of the risk to die, respectively, compared to an even higher 50% and 37% relative reduction of mortality in neonates, respectively. In

therapeutic and adverse effects of IVIG (29).

of immunoglobulins administered.

Supplementation of the preterm serum with either intravenous immunoglobulin or IgMenriched immunoglobulin did not change the results of phagocytosis rates (percentage of neutrophils phagocytosing group B streptococci in vitro in infants < 32 weeks of gestation and adult controls) significantly (25).

In a rat model marked neutropenia, complete depletion of the neutrophil storage pool, and death within 48 hours were observed in newborn rats intrapulmonically inoculated with type III group B streptococci (26). Intraperitoneal administration of 225 mg of IVIG immediately after intrapulmonic inoculation of GBS significantly lessened the degree of neutropenia and prevented depletion of the neutrophil storage pool and death. No effect of IVIG on neutrophil production was observed in vitro or in vivo in normal neonatal rats injected with IVIG. IVIG, however, markedly hastened release of neutrophils from the reserves into the blood and hastened the arrival of neutrophils at the site of the bacterial injection. Specific antibody to GBS, as opposed to a nonspecific IgG effect, appeared to be responsible for the improvements in neutrophils kinetics and for survival of the animals.

In animal experiments following administration of IVIGAM endotoxemia was induced by intraperitoneal inoculation of a sublethal dose of Escherichia coli and subsequent intravenous administration of an antimicrobial agent (27). Prophylactic administration of IVIGAM was found to significantly attenuate the antibiotic-induced increase in endotoxin activity as compared to the albumin control group. These experimental results suggested that in endotoxaemia the polyclonal immunoglobulin preparation had a prophylactic protective effect on the acute phase responses and reduced the cardiodepressant effects of Escherichia coli septicaemia.

The pharmacokinetics and safety of IVIG were examined in thirty neonates with suspected sepsis who were randomly assigned either to a treatment (receiving either 250, or 500, or 1,000 mg/kg of IVIG plus antibiotics) or control (antibiotics alone) group (28). The 500 mg/kg dose produced a rise in total IgG for greater than 8 and in group B streptococcus typespecific IgG for greater than 4-14 days. The type-specific antibody elevation varied with the amount of pathogen-specific antibody and dose of IVIG. Pharmacokinetic analysis suggested a biphasic elimination curve and a terminal elimination half-life of 24.2 days. No toxicity was observed (28).

Prophylactic IVIG at a dose of 0.5 g/kg/day was given prospectively in 28 healthy preterm infants with a mean gestational age of 29.4 weeks and weight of 1,387g when they were 3-10 days old (29). Urine samples of the neonates were obtained for analysis on days 1, 2 and 3 following IVIG administration as well as 1 day before; and urinary nitrite levels were 2.77 +/- 1.66 µmol/mmol creatinine before IVIG administration; 4.33 +/- 3.88 µmol/mmol creatinine on the 1st; 3.77 +/- 2.73 µmol/mmol creatinine on the 2nd, and 3.64 +/- 3.28 µmol/mmol creatinine on the 3rd day. The increase of urinary nitrite levels was significant between before and after IVIG administration, thereafter levels did not differ significantly, suggesting that endogenous NO formation might play an important role in both the therapeutic and adverse effects of IVIG (29).
