Lactoferrin Supplementation to Prevent Nosocomial Infections in Preterm Infants

The study by Manzoni and colleagues¹ in this issue of JAMA represents an important step toward preventing infections that currently pose a major hurdle for preterm infants. The findings give insight into the role of lactoferrin in preventing infection, helping to define its importance in breast milk as well as the effect of daily supplementation with bovine lactoferrin (BLF) in preterm infants.

The incidence of late-onset (>72 hours of age) bloodstream infections in very low-birth-weight (VLBW) infants (<1500 g) is approximately 20% and is complicated by high mortality and neurodevelopmental impairment.^{2 - 3} In the United States, nearly 65 000 VLBW infants are born each year, which translates into approximately 13 000 infections, 2300 deaths, and neurodevelopmental impairment in 3000 survivors.⁴ For the smallest infants of extremely low birth weight (ELBW) (<1000 g), neurodevelopmental impairment occurs in 45% of those who survive bacteremia and 57% of those who survive fungemia.³ For VLBW infants, bloodstream infections increase hospital treatment costs and length of stay.⁵

Manzoni and colleagues¹ performed a multicenter, double-blind, placebo-controlled, randomized trial in VLBW infants comparing administration of BLF alone or in combination with Lactobacillus rhamnosus GG (LGG) to placebo. Invasive infections (blood or cerebrospinal or peritoneal fluid) were significantly lower in the treatment groups (5.9% for BLF and 4.6% for BLF plus LGG, vs 17% for placebo). This effect was strongest for infants weighing less than 1000 g (11.3% for BLF and 11.1% for BLF plus LGG, vs 36.7% for placebo). There was an effect on infection-related mortality for both treatment groups (0% for BLF and 0.7% for BLF plus LGG, vs 4.8% for placebo), whereas the incidence of necrotizing enterocolitis was decreased in the BLF plus LGG group only (0% vs 6% in infants receiving placebo).

The effect of BLF and BLF plus LGG was significant for ELBW infants (n = 167), as well as those weighing less than 750 g (n = 39) and of 27 weeks or fewer gestation (n = 118), but not for infants weighing between 1000 and 1500 g (n = 307). This may be explained in part by the dosing used in the study. The infants did not receive dosing based on their weight, but rather all infants received 100 mg per day; therefore, smaller infants received a higher dose per kilogram per day. For example, for infants weighing 500, 1000, and 1500 g, the dose per kg would be 200, 100, and 67 mg/kg, respectively. Extremely low-birth-weight infants also received study drug for 6 weeks compared with only 4 weeks for infants weighing 1000 to 1500 g. Thus, supplementation of BLF between 100 and 200 mg/kg per day and possibly for a longer period may be needed for all patients. Additionally, doses higher than 200 mg/kg per day may have a greater effect and need to be further studied.

Post hoc analysis revealed that BLF decreased gram-positive and fungal infections. This demonstrates the probable interaction of lactoferrin with the gastrointestinal tract microflora effecting common gram-positive skin and central venous catheter bloodstream infections, as central venous catheter days and time to reach full enteral feedings were similar between groups.⁶ While BLF did not change fungal colonization, it prevented progression to infection, thus potentially allowing fungi to maintain their symbiotic role in the gut and helping to maintain a balanced microflora.

Fluconazole prophylaxis has demonstrated efficacy in reducing invasive Candida infections in single and multicenter randomized controlled trials.⁷ However, intravenous immunoglobulin products and colony-stimulating factors have not proven effective in preventing infections, largely because many elements of the immune system are underdeveloped in preterm infants.^{8 - 9} Lactoferrin has many functions and is a key link in several immune processes.⁶ This may in part explain the large effect demonstrated by Manzoni et al.¹

Lactoferrin is the major whey protein in human milk and is involved in innate host defenses having antimicrobial and immunomodulation activities as well as promoting a mature and healthy gut.^{6 ,10 - 11} Bovine lactoferrin has activity against gram-positive and gram-negative bacteria, fungi, and viruses such as rotavirus, enterovirus, and adenovirus.⁶ This includes antilipopolysaccharide (against gram-negative organisms), antilipoteichoic acid (against gram-positive organisms), and anti-Candida cell wall component activity.¹⁰ Lactoferrin passes through the stomach, allowing it to act in the entire gastrointestinal tract, and is largely excreted in the stools unchanged. Furthermore, lactoferrin is converted via pepsin and low pH into a potent antimicrobial peptide, lactoferricin, which can eradicate ingested pathogens and bind endotoxin in the stomach. Indirectly, lactoferrin binds iron, making it unavailable to support microbial growth and preventing bacterial invasion of the bowel by blocking adherence of bacteria to the gut epithelia.

The immunomodulatory properties of lactoferrin include reducing inflammation by decreasing production of tumor necrosis factor α and other proinflammatory molecules and by regulating the immune response, protecting against severe inflammation related to infection and septic shock.^{11 - 12} This may contribute to decreasing the mortality and neurodevelopmental impairment associated with bloodstream infections. Moreover, lactoferrin contributes to intestinal cell proliferation and differentiation, which enhances the gut barrier and promotes the growth of bifidobacteria, helping to establish a favorable microbiome.¹³

Because colostrum contains the highest lactoferrin content (6 g/L, vs 1-5 g/L in mature human milk), nature is providing “added protection” for a short period to full-term infants—but for preterm infants this added protection is needed for weeks or months. Very low-birth-weight infants receiving human milk have inadequate protection because it can take 2 to 3 weeks until they receive full-volume enteral feedings and the full amounts of the protective components in human milk. Even this may not be enough until infants are close to full-term corrected age.

The study by Manzoni et al¹ used BLF rather than human lactoferrin (HLF). Both HLF and BLF have high homology (77%). Industry is currently able to produce highly purified BLF as well as recombinant HLF. Bovine lactoferrin and lactoferricin exhibit higher antimicrobial activity compared with their human counterparts.^{13 - 14} However, the comparative safety and efficacy of BLF compared to HLF in preterm infants will be an important question to answer in future studies, as will be finding the optimal dosing of each.

Future research should be directed at confirming the safety and efficacy of lactoferrin in VLBW infants, including more extremely preterm infants, because they potentially will benefit the most from lactoferrin. Combination strategies,¹⁵ such as the use of BLF plus LGG in the study by Manzoni et al,¹ should be pursued, and substances that might affect lactoferrin activity, such as iron supplementation, should be investigated. The effect of lactoferrin on hematocrit should be monitored, and the effects of lactoferrin on neurodevelopmental outcome, hospital length of stay, and costs should be studied.

The beginnings of further research are under way. A phase 1 multicenter, randomized, placebo-controlled study (clinicaltrials.gov Identifier: NCT00854633) has begun, assessing a recombinant HLF product to prevent neonatal infections in infants weighing 750 to 1500 g, using dosing of 150 mg/kg every 12 hours. Manzoni et al are further studying the effect of BLF alone or in combination with LGG on the primary end point of necrotizing enterocolitis.¹⁶

The results of the current study by Manzoni et al provide the opportunity to make further research on lactoferrin a priority. For this vulnerable population of extremely preterm infants, it is important to move forward in a timely fashion to prevent nosocomial infections, infection-related mortality, and associated neurodevelopmental impairment.