Albumin lavage does not improve the outcome of meconium aspiration syndrome

An Unsettled Promise: The Newborn Piglet Model of Neonatal Acute Respiratory Distress Syndrome (NARDS). Physiologic Data and Systematic Review

Despite great advances in mechanical ventilation and surfactant administration for the newborn infant with life-threatening respiratory failure no specific therapies are currently established to tackle major pro-inflammatory pathways. The susceptibility of the newborn infant with neonatal acute respiratory distress syndrome (NARDS) to exogenous surfactant is linked with a suppression of most of the immunologic responses by the innate immune system, however, additional corticosteroids applied in any severe pediatric lung disease with inflammatory background do not reduce morbidity or mortality and may even cause harm. Thus, the neonatal piglet model of acute lung injury serves as an excellent model to study respiratory failure and is the preferred animal model for reasons of availability, body size, similarities of porcine and human lung, robustness, and costs. In addition, similarities to the human toll-like receptor 4, the existence of intraalveolar macrophages, the sensitivity to lipopolysaccharide, and the production of nitric oxide make the piglet indispensable in anti-inflammatory research. Here we present the physiologic and immunologic data of newborn piglets from three trials involving acute lung injury secondary to repeated airway lavage (and others), mechanical ventilation, and a specific anti-inflammatory intervention via the intratracheal route using surfactant as a carrier substance. The physiologic data from many organ systems of the newborn piglet—but with preference on the lung—are presented here differentiating between baseline data from the uninjured piglet, the impact of acute lung injury on various parameters (24 h), and the follow up data after 72 h of mechanical ventilation. Data from the control group and the intervention groups are listed separately or combined. A systematic review of the newborn piglet meconium aspiration model and the repeated airway lavage model is finally presented. While many studies assessed lung injury scores, leukocyte infiltration, and protein/cytokine concentrations in bronchoalveolar fluid, a systematic approach to tackle major upstream pro-inflammatory pathways of the innate immune system is still in the fledgling stages. For the sake of newborn infants with life-threatening NARDS the newborn piglet model still is an unsettled promise offering many options to conquer neonatal physiology/immunology and to establish potent treatment modalities.

Effects of Natural versus Synthetic Surfactant with SP-B and SP-C Analogs in a Porcine Model of Meconium Aspiration Syndrome

BACKGROUND

Meconium displaces surfactant from the alveolar surface and inhibits its function. The development of active synthetic surfactants is complicated, especially to synthesize the hydrophobic surfactant proteins SP-B and SP-C. A synthetic surfactant, CHF5633 containing SP-B and SP-C analogs, has been designed to act similarly to the natural surfactant poractant alfa.

OBJECTIVE

To test the resistance to meconium inactivation of CHF5633 compared to poractant alfa. Secondary outcome measurements were respiratory and inflammatory parameters.

METHODS

Twenty-six newborn pigs, bodyweight 1.4-2.0 kg were randomized to receive either poractant alfa or CHF5633. After anesthesia, surgery and final stabilization, meconium was instilled endotracheally followed by surfactant. Bronchial lavage fluid was obtained before intervention and every second hour. Respiratory parameters were registered and blood samples drawn before intervention and every hour.

RESULTS

Surfactant was inactivated in both groups 6 h after meconium instillation, but CHF5633 was more resistant than poractant alfa in terms of lipid peroxidation. Respiratory parameters were similar in both groups. Inflammatory and hemostatic parameters differed between groups, suggesting that the surfactants may play different roles in the meconium-induced inflammatory process. Due to the differential effects and complex pattern observed, the data do not indicate that one of the surfactants was superior with respect to inflammatory and hemostatic responses.

CONCLUSION

This study indicates that CHF5633 is as efficient as poractant alfa in experimental meconium aspiration syndrome.

Pathway-specific complement activity in pigs evaluated with a human functional complement assay

BACKGROUND

The complement system is an important part of innate immunity. Complement deficiencies or inappropriate activation of complement may cause severe diseases. The complement functional test, Wielisa, assesses all three complement activation pathways in humans. It is important to have assays available to determine the functional complement activity in research animals. Since the pig is a relevant animal in experimental research, the aim of the present study was to evaluate the applicability of this human complement assay in pigs.

METHODS

Normal pig serum was serially diluted and assayed in the Wielisa test which is based on the activation of complement detected with an antibody against activated C9. The specificity of the three pathways was assessed using purified human MBL and mouse monoclonal antibodies against human C1q and pig factor D. Sera from 103 pigs and 38 newborn pigs were analyzed. Finally, functional activity of all pathways was assessed in vitro and in vivo in the absence and presence of complement inhibitors.

RESULTS

The detection antibody showed cross-reactivity against pig. Normal pig serum showed activity in all pathways however about 10-fold more serum was required to obtain values comparable to human serum. Anti-human C1q and anti-pig factor D antibodies abolished classical and alternative pathway activity, respectively. Sera with low lectin pathway activity reconstituted with purified human MBL, fully recovered this activity. No deficiencies were found in classical or alternative pathway, whereas the lectin pathway showed reduced activity in a substantial number of pigs, similar to the situation in humans. Finally, the assay was successfully used to evaluate and monitor inhibition of pig complement in vitro and in vivo.

CONCLUSIONS

The human complement Wielisa test can be used for functional evaluation of all complement pathways in pig serum.