Cathepsin B Processing Is Required for the In Vivo Efficacy of Albumin-Drug Conjugates.

Targeted drug delivery approaches that selectively and preferentially deliver therapeutic agents to specific tissues are of great interest for safer and more effective pharmaceutical treatments. We investigated whether cathepsin B cleavage of a valine-citrulline [VC(S)]-containing linker is required for the release of monomethyl auristatin E (MMAE) from albumin-drug conjugates. In this study, we used an engineered version of human serum albumin, Veltis High Binder II (HBII), which has enhanced binding to the neonatal Fc (fragment crystallizable) receptor (FcRn) to improve drug release upon binding and FcRn-mediated recycling. The linker-payload was conjugated to cysteine 34 of albumin using a carbonylacrylic (caa) reagent which produced homogeneous and plasma stable conjugates that retained FcRn binding. Two caa-linker-MMAE reagents were synthesized─one with a cleavable [VC(S)] linker and one with a noncleavable [VC(R)] linker─to question whether protease-mediated cleavage is needed for MMAE release. Our findings demonstrate that cathepsin B is required to achieve efficient and selective antitumor activity. The conjugates equipped with the cleavable [VC(S)] linker had potent antitumor activity in vivo facilitated by the release of free MMAE upon FcRn binding and internalization. In addition to the pronounced antitumor activity of the albumin conjugates in vivo, we also demonstrated their preferable tumor biodistribution and biocompatibility with no associated toxicity or side effects. These results suggest that the use of engineered albumins with high FcRn binding combined with protease cleavable linkers is an efficient strategy to target delivery of drugs to solid tumors.

Expanding Transition Metal-Mediated Bioorthogonal Decaging to Include C-C Bond Cleavage Reactions.

The ability to control the activation of prodrugs by transition metals has been shown to have great potential for controlled drug release in cancer cells. However, the strategies developed so far promote the cleavage of C-O or C-N bonds, which limits the scope of drugs to only those that present amino or hydroxyl groups. Here, we report the decaging of an ortho-quinone prodrug, a propargylated ß-lapachone derivative, through a palladium-mediated C-C bond cleavage. The reaction's kinetic and mechanistic behavior was studied under biological conditions along with computer modeling. The results indicate that palladium (II) is the active species for the depropargylation reaction, activating the triple bond for nucleophilic attack by a water molecule before the C-C bond cleavage takes place. Palladium iodide nanoparticles were found to efficiently trigger the C-C bond cleavage reaction under biocompatible conditions. In drug activation assays in cells, the protected analogue of ß-lapachone was activated by nontoxic amounts of nanoparticles, which restored drug toxicity. The palladium-mediated ortho-quinone prodrug activation was further demonstrated in zebrafish tumor xenografts, which resulted in a significant anti-tumoral effect. This work expands the transition-metal-mediated bioorthogonal decaging toolbox to include cleavage of C-C bonds and payloads that were previously not accessible by conventional strategies.

The Epidemiology and Costs of Disease Intervention Specialist Retention.

BACKGROUND: The COVID-19 pandemic changed the environment in which disease intervention specialists (DISs) operate, as their skills were in demand beyond sexually transmitted disease (STD) control programs. Workforce conditions generally have changed in the last 2 years, imposing additional challenges. Retaining STD DIS has become more difficult in the changed environment. MATERIALS AND METHODS: We conducted a landscape scan and obtained data from literature and personal observations to characterize current DIS workforce issues. We used published employment data to characterize current labor market conditions and described how cost-effectiveness analysis could be used to assess potential DIS retention interventions. An example illustrating cost-effectiveness concepts was developed. RESULTS: Many STD control programs faced difficulties in retaining STD DIS, because competing positions often could be done without field work. Economic and crime issues posed additional challenges. General workforce turnover has increased 33% since 2016. Turnover varies by age, sex, and education. Cost-effectiveness analysis can be used to assess DIS retention interventions, but data on costs and outcomes are needed on an ongoing basis. Changes in the workforce environment could impact both retention and the effectiveness of retention interventions. CONCLUSIONS: Workforce changes have impacted employee retention. Increased federal funding makes expansion of the DIS workforce possible, but the labor market environment will continue to pose challenges to recruitment and retention.

Microglial inflammasome activation drives developmental white matter injury.

Injury to the developing brain during the perinatal period often causes hypomyelination, leading to clinical deficits for which there is an unmet therapeutic need. Dysregulation of inflammation and microglia have been implicated, yet the molecular mechanisms linking these to hypomyelination are unclear. Using human infant cerebrospinal fluid (CSF) and postmortem tissue, we found that microglial activation of the pro-inflammatory molecular complex the NLRP3 inflammasome is associated with pathology. By developing a novel mouse brain explant model of microglial inflammasome activation, we demonstrate that blocking the inflammasome rescues myelination. In human and mouse, we discovered a link between the inflammasome product IL1ß and increased levels of follistatin, an endogenous inhibitor of activin-A. Follistatin treatment was sufficient to reduce myelination, whereas myelination was rescued in injured explants upon follistatin neutralization or supplementation with exogenous activin-A. Our data reveal that inflammasome activation in microglia drives hypomyelination and identifies novel therapeutic strategies to reinstate myelination following developmental injury.

Activin receptors regulate the oligodendrocyte lineage in health and disease.

The most prevalent neurological disorders of myelin include perinatal brain injury leading to cerebral palsy in infants and multiple sclerosis in adults. Although these disorders have distinct etiologies, they share a common neuropathological feature of failed progenitor differentiation into myelin-producing oligodendrocytes and lack of myelin, for which there is an unmet clinical need. Here, we reveal that a molecular pathology common to both disorders is dysregulation of activin receptors and that activin receptor signaling is required for the majority of myelin generation in development and following injury. Using a constitutive conditional knockout of all activin receptor signaling in oligodendrocyte lineage cells, we discovered this signaling to be required for myelination via regulation of oligodendrocyte differentiation and myelin compaction. These processes were found to be dependent on the activin receptor subtype Acvr2a, which is expressed during oligodendrocyte differentiation and axonal ensheathment in development and following myelin injury. During efficient myelin regeneration, Acvr2a upregulation was seen to coincide with downregulation of Acvr2b, a receptor subtype with relatively higher ligand affinity; Acvr2b was shown to be dispensable for activin receptor-driven oligodendrocyte differentiation and its overexpression was sufficient to impair the abovementioned ligand-driven responses. In actively myelinating or remyelinating areas of human perinatal brain injury and multiple sclerosis tissue, respectively, oligodendrocyte lineage cells expressing Acvr2a outnumbered those expressing Acvr2b, whereas in non-repairing lesions Acvr2b+ cells were increased. Thus, we propose that following human white matter injury, this increase in Acvr2b expression would sequester ligand and consequently impair Acvr2a-driven oligodendrocyte differentiation and myelin formation. Our results demonstrate dysregulated activin receptor signaling in common myelin disorders and reveal Acvr2a as a novel therapeutic target for myelin generation following injury across the lifespan.

Strategies for Conditional Regulation of Proteins.

Design of the next-generation of therapeutics, biosensors, and molecular tools for basic research requires that we bring protein activity under control. Each protein has unique properties, and therefore, it is critical to tailor the current techniques to develop new regulatory methods and regulate new proteins of interest (POIs). This perspective gives an overview of the widely used stimuli and synthetic and natural methods for conditional regulation of proteins.

Controlled masking and targeted release of redox-cycling ortho-quinones via a C-C bond-cleaving 1,6-elimination.

Natural products that contain ortho-quinones show great potential as anticancer agents but have been largely discarded from clinical development because their redox-cycling behaviour results in general systemic toxicity. Here we report conjugation of ortho-quinones to a carrier, which simultaneously masks their underlying redox activity. C-benzylation at a quinone carbonyl forms a redox-inactive benzyl ketol. Upon a specific enzymatic trigger, an acid-promoted, self-immolative C-C bond-cleaving 1,6-elimination mechanism releases the redox-active hydroquinone inside cells. By using a 5-lipoxygenase modulator, ß-lapachone, we created cathepsin-B-cleavable quinone prodrugs. We applied the strategy for intracellular release of ß-lapachone upon antibody-mediated delivery. Conjugation of protected ß-lapachone to Gem-IgG1 antibodies, which contain the variable region of gemtuzumab, results in homogeneous, systemically non-toxic and conditionally stable CD33+-specific antibody-drug conjugates with in vivo efficacy against a xenograft murine model of acute myeloid leukaemia. This protection strategy could allow the use of previously overlooked natural products as anticancer agents, thus extending the range of drugs available for next-generation targeted therapeutics.

Photo-transformation of aqueous nitroguanidine and 3-nitro-1,2,4-triazol-5-one: Emerging munitions compounds.

Two major components of insensitive munition formulations, nitroguanidine (NQ) and 3-nitro-1,2,4-triazol-5-one (NTO), are highly water soluble and therefore likely to photo-transform while in solution in the environment. The ecotoxicities of NQ and NTO solutions are known to increase with UV exposure, but a detailed accounting of aqueous degradation rates, products, and pathways under different exposure wavelengths is currently lacking. Here, we irradiated aqueous solutions of NQ and NTO over a 32-h period at three ultraviolet wavelengths (254 nm, 300 nm, and 350 nm) and analyzed their degradation rates and transformation products. NQ was completely degraded by 30 min at 254 nm and by 4 h at 300 nm, but it was only 10% degraded after 32 h at 350 nm. Mass recoveries of NQ and its transformation products were ≥80% for all three wavelengths, and consisted of large amounts of guanidine, nitrate, and nitrite, and smaller amounts of cyanamide, cyanoguanidine, urea, and ammonium. NTO degradation was greatest at 300 nm with 3% remaining after 32 h, followed by 254 nm (7% remaining) and 350 nm (20% remaining). Mass recoveries of NTO and its transformation products were high for the first 8 h but decreased to 22-48% by 32 h, with the major aqueous products identified as ammonium, nitrate, nitrite, and a urazole intermediate. Environmental half-lives of NQ and NTO in pure water were estimated as 4 and 6 days, respectively. We propose photo-degradation pathways for NQ and NTO supported by observed and quantified degradation products and changes in solution pH.

Apolipoprotein E e4 and its prevalence in early childhood death due to sudden infant death syndrome or to recognised causes.

BACKGROUND: Specific genetic polymorphisms have been shown to be more common in unexplained infant death. The APOE genotype exhibits opposite effects at the extremes of age with protective effects of e4 on perinatal mortality but detrimental effects as age progresses. OBJECTIVE: To determine whether the APOE e4 allele is associated with early childhood (1 week-2 years) unexplained death ('sudden infant death syndrome', SIDS) or with recognised causes (non-SIDS) and to compare these cohorts with published perinatal and adult data. METHODS: DNA was extracted from spleen tissue of children dying in South East Scotland between 1990 and 2002. APOE alleles (e2, e3, e4) were determined using PCR. Comparisons of allele frequencies between groups were made. RESULTS: There were 167 SIDS cases and 117 non-SIDS cases. Allele distributions of SIDS cases were similar to healthy newborns. Allele distributions of non-SIDS cases were more similar to adults than to healthy newborns. The percentage of children with at least one e4 allele was significantly lower in non-SIDS compared to SIDS (p = 0.016). Non-SIDS cases had a higher frequency of e3 compared to SIDS cases (p = 0.01) and to healthy newborns (0.005). CONCLUSIONS: Children dying from identified causes have different APOE allele distributions from SIDS cases, but are similar to adults. Children dying from SIDS have an allele distribution comparable to healthy newborns. The prevalence of e4 in SIDS is not of an order to contribute significantly to the age-related decline in e4.

Sudden unexpected postnatal collapse.

This review of Sudden Unexpected Postnatal Collapse (SUPC) highlights the challenges in definition and nomenclature that currently exist. In comparing SUPC with Sudden Unexpected Death in Infancy (SUDI), the potentially avoidable nature of many SUPC is emphasised and the role of positioning and public awareness explored. The article focusses on the implementation of preventative strategies in the immediate postnatal period and the role of therapeutic hypothermia in ameliorating long term neurological injury.

Dose-dependent relationship between acidosis at birth and likelihood of death or cerebral palsy.

BACKGROUND: The acid-base status of infants around birth can provide information about their past, current and future condition. Although umbilical cord blood pH <7.0 or base deficit ≥12 mmol/L is associated with increased risk of adverse outcome, there is uncertainty about the prognostic value of degree of acidosis as previous studies have used different variables, thresholds, outcomes and populations. METHODS: Retrospective review of routinely collected clinical data in all live-born inborn infants of 35 weeks gestation or more delivered between January 2005 and December 2013 at the Simpson Centre for Reproductive Health, Edinburgh, UK. Infants were included if their lowest recorded pH was <7 and/or highest base deficit ≥12 mmol/L on either umbilical cord blood and/or neonatal blood gas within 1 hour of birth. Neurodevelopmental outcome of the infants with encephalopathy was collected from the targeted follow-up database. RESULTS: 56 574 infants were eligible. 506 infants (0.9%) met inclusion criteria. Poor condition at birth and all adverse outcomes increased with worsening acidosis. Combined outcome of death or cerebral palsy was 3%, 10% and 40% at lowest pH of 6.9-6.99, 6.8-6.89 and <6.8, respectively, and 8%, 14% and 59% at a base deficit of 12-15.9, 16-19.9 and 20 mmol/L or more, respectively. CONCLUSIONS: There is a dose-dependent relationship between the degree of acidosis within an hour of delivery, and the likelihood of adverse neonatal and later neurodevelopmental outcome in infants born at 35 weeks gestation or more.

Reducing Antibiotic Exposure in Suspected Neonatal Sepsis.

Prolonged antibiotic therapy is associated with antimicrobial resistance and increased mortality in preterm infants. We evaluated the impact of an automatic stop order (ASO) and C-reactive protein (CRP) on the duration of antibiotics and level of intervention in infants screened for early-onset sepsis who had negative cultures. We introduced an ASO for low-risk infants, then, consequently, for all infants treated for suspected sepsis. We subsequently introduced a single CRP measurement at 36 hours. Between 2011 and 2014, 4 time periods were studied, at baseline and after each intervention. The proportion of infants receiving ≤48 hours of antibiotics increased from 19% to 72.5% ( P < .0001), whereas that of infants receiving avoidable doses (>48 hours and <5 days) fell from 50% to 0.8% ( P < .0001). The use of an ASO decreased the proportion receiving avoidable doses from 26/92 (28.3%) to 9/293 (3.1%); P < .0001. There was a reduction in lumbar punctures performed, from 35% to 20%; P = .015.

Oxygen flux reduces Cux1 positive neurons and cortical growth in a gestational rodent model of growth restriction.

BACKGROUND: The mammalian cerebral cortex forms in an inside-out manner, establishing deep cortical layers before superficial layers and is regulated by transcription factors which influence cell differentiation. Preterm birth interrupts the trajectory of normal neurodevelopment and adverse perinatal exposures have been implicated in cortical injury. We hypothesise that growth restriction (GR) and fluctuating hyperoxia (ΔO2) impair cortical laminar development. METHODS: Sprague-Dawley rats received 18% (non-restricted, NR) or 9% (growth restricted, GR) protein diet from E15-P7. Litters were reared in air or fluctuating hyperoxia (circa 10kPa) from P0 to P7. Cortical laminae were stained and measured. Neuronal subtypes were quantified using immunofluorescence for subtype-specific transcription factors (Satb2, Cux1, Ctip2, Tbr1). RESULTS: ΔO2 did not affect brain weight at P7 but reduced cortical thickness in both NR (p<0.05) and GR groups (p<0.001). ΔO2 resulted in superficial cortical thinning in both groups and in the deep layers of GR pups (p<0.001). Cell density was preserved. ΔO2 did not affect proportions of callosal, corticothalamic and corticospinal neurons but resulted in a reduction of neurons expressing Cux1 (p<0.01) implicated in dendritic branching and synapse formation. CONCLUSION: Postnatal ΔO2, a modifiable factor in neonatal care, impairs cortical development in a rodent model with preferential disadvantage to superficial neurons.

Photo-degradation of 2,4-dinitroanisole (DNAN): An emerging munitions compound.

The US military is developing insensitive munitions (IM) that are less sensitive to shock and high temperatures to minimize unintentional detonations. DNAN (2,4-dinitroanisole) is one of the main ingredients of these IM formulations. During live-fire training, chunks of IM formulations are scattered by partial detonations and, once on the soil, they weather and dissolve. DNAN changes color when exposed to sunlight suggesting that it photodegrades into other compounds. We investigated the photo-degradation of DNAN both as a pure solid and as part of solid IM formulations, IMX101, IMX104 and PAX21. The concentrations of degradation products found were small, <1%, relative to DNAN concentrations. We saw transient peaks in the chromatograms indicating intermediate, unstable products but we consistently found methoxy nitrophenols and methoxy nitroanilines. We also found one unknown in most of the samples and other unknowns less frequently.

Going social: Success in online recruitment of men who have sex with men for prevention HIV vaccine research.

OBJECTIVE: To compare the use of four different social media sites to recruit men who have sex with men (MSM) and transgender women to a phase 2b HIV prevention vaccine trial, HVTN 505. DESIGN: Retrospective, observational study. METHODS: The University of Pennsylvania HIV Vaccine Trials Unit (Penn HVTU) employed street outreach and online recruitment methods to recruit participants for HVTN 505 using a combination of national recruitment images/messages with Philadelphia-specific language and imagery. We compared the efficiency (number of enrolled participants per number of completed phone screens) and effectiveness (number of enrolled participants per time interval employed) of each strategy, as well as the demographics and risk behaviors of the populations. RESULTS: Online recruitment strategies populated 37% (71/191) of trial participants at our site. Among the four social media strategies employed, 45.1% (32/71) were enrolled through Facebook, 16.9% (12/71) through Craigslist, 15.5% (11/71) through a web-based marketing company (WBMC), and 22.5% (16/71) via GRINDR. The number of participants enrolled per month of strategy and the months the strategy was employed were Facebook - 32(33months), Craigslist - 12(33months), WBMC - 11(6months), and GRINDR - 16(0.56months). In-person and online recruitment strategies yielded participants of similar demographics and levels of risk behavior. CONCLUSION: Use of several social media recruitment modalities produced large numbers of MSM engaging in high risk behavior and willing to participate in an HIV prevention vaccine trial. In comparison to other social media and online strategies, recruitment via GRINDR was the most effective.

The neuropathology of stillbirth - correlation with apolipoprotein genotype in a Scottish population based study.

BACKGROUND: The neuropathology of stillbirths has been widely studied but rarely on a population basis. Whether foetal apolipoprotein E (APOE) genotype exerts any influence has been little investigated, despite well known effects in adult brains. AIMS: To establish the neuropathology of a population cohort of stillbirths and compare with the APOE genotype. STUDY DESIGN AND SUBJECTS: The brains of 191 stillbirths (≥24weeks of gestation) were recruited from a Scottish population cohort and grouped by clinical history. APOE genotype was available for 97%. RESULTS AND CONCLUSIONS: One or more neuropathological features, most appearing relatively recent, were found in 54% of 157 antepartum singletons, 44% of 9 abruption-associated stillbirths, 85% of 13 in multiple pregnancies but in only 19% of 12 intrapartum stillbirths. White matter injury (WMI) occurred in 36% of preterm and 21% mature stillbirths. Fresh petechial haemorrhages were common in all groups (29%) but germinal matrix haemorrhage (GMH) (7%) and periventricular leucomalacia (1%) were confined to preterm. GMH was significantly associated with WMI (p=0.003). Placental inflammation was common in intrapartum stillbirths (50%), compared with antepartum (15%), multiple pregnancy (23%) and abruption (0%). ß-Amyloid precursor protein (ßAPP) positive axons (36% stillbirths overall) correlated closely with WMI (p<0.0001), justifying future routine inclusion in foetal neuropathological investigation. This study highlights the paucity of brain damage in intrapartum stillbirths. While APOE2 was significantly overrepresented in stillbirths, there was no correlation between APOE genotype and neuropathological findings. We conclude that APOE does not influence neuropathological outcomes in stillbirths.

Stridor in asphyxiated neonates undergoing therapeutic hypothermia.

Therapeutic hypothermia is an established standard of care in the treatment of hypoxic-ischemic encephalopathy. Application of therapeutic hypothermia in the clinical setting may reveal a wider spectrum of adverse events than previously reported. We report 5 cases of transient respiratory stridor in 51 infants, occurring at different time points in the cooling process, which appeared to be unrelated to the intubation procedure. Therapeutic hypothermia was associated with transient stridor in this case series. Formal laryngoscopy is required to determine the underlying pathologic etiology.

Electrographic seizures are associated with brain injury in newborns undergoing therapeutic hypothermia.

OBJECTIVE: Seizures are common among newborns with hypoxic-ischaemic encephalopathy (HIE) but the relationship between seizure burden and severity of brain injury among neonates receiving therapeutic hypothermia (TH) for HIE is unclear. We tested the hypothesis that seizure burden is associated with cerebral tissue injury independent of amplitude-integrated EEG (aEEG) background activity. STUDY DESIGN: Term neonates undergoing 72 h of TH at four centres were selected for study if they had continuous aEEG and MRI. The aEEG with corresponding 2-channel raw EEG (aEEG/EEG), was classified by severity of background and seizure burden; MR images were classified by the severity of tissue injury. RESULTS: Of 85 neonates, 52% had seizures on aEEG/EEG. Overall, 35% had high seizure burden, 49% had abnormal aEEG background in the first 24 h and 36% had severe injury on MRI. Seizures were most common on the first day, with significant recurrence during and after rewarming. Factors associated with severe injury on MRI were high seizure burden, poor aEEG background, 10 min Apgar and the need for more than one anticonvulsant. In multivariate logistic regression, high seizure burden was independently associated with greater injury on MRI (OR 5.00, 95% CI 1.47 to 17.05 p=0.01). Neither aEEG background, nor 10 min Apgar score were significant. CONCLUSIONS: Electrographic seizure burden is associated with severity of brain injury on MRI in newborns with HIE undergoing TH, independent of degree of abnormality on aEEG background. Seizures are common during cooling, particularly on day 1, with a significant rebound on day 4.

Racial disparities in HIV prevalence and risk behaviors among injection drug users and members of their risk networks.

In the United States, racial differences in the prevalence and incidence of HIV infection and AIDS diagnoses are dramatic. These differences are large, have been recognized for nearly 20 years, and are as yet not well investigated. These disparities show no signs of diminishing and, in fact, are widening, particularly among drug users and women. Most observers of the racial disparities in prevalence and incidence of HIV infections and AIDS diagnoses in the United States have concluded that these disparities exist because prevention messages, supplies, and/or interventions do not effectively reach those at greatest risk of infection. In essence, such interpretations suggest that Blacks and Latinos continue to practice more risk behaviors than Whites. There are much data to suggest that this is, in fact, not true. Evidence from 232 'index' injection drug users and 465 of their drug and sexual network members participating in HIV Prevention Trials Network 037 is presented. These data describe lower use and/or access to drug treatment and needle exchange programs by Black injectors. In addition, data indicate the coexistence of increased prevalence of HIV in the networks of uninfected Black drug users and fewer associated risk behaviors in the networks of Black and Latino indices compared with networks of White indices. Understanding racial disparities in HIV is a critical challenge; yet, risk behaviors alone do not explain observed disparities in infection rates.

Unexpected collapse in apparently healthy newborns--a prospective national study of a missing cohort of neonatal deaths and near-death events.

BACKGROUND: Sudden and unexpected postnatal collapse (SUPC) of a healthy newborn infant is a rare event, which carries a high risk of mortality and significant neurodisability in survivors. An underlying condition can be found in 60% of cases who undergo detailed postmortem but in the remainder there are important associations with prone position, breast feeding and primiparous status. The authors undertook a prospective study to ascertain the population incidence of SUPC in the UK. METHODS: Cases were referred through the British Paediatric Surveillance Unit reporting scheme over a 13-month period. Infants were at ≥37 weeks of gestation, had an Apgar score of ≥8 at 5 min, collapsed within 12 h in hospital requiring positive pressure ventilation and either died or received ongoing intensive care. Data were collected on maternal and infant characteristics, clinical investigations and 1-year outcome. FINDINGS: 45 cases were reported, an incidence of 0.05/1000 live births of whom 12 infants died. In 15/45 infants, an underlying disease/abnormality was determined. In 30/45 cases (0.035/1000 live births), no such cause was found, but in 24, the clinical/pathological diagnosis was airway obstruction during breast feeding or in prone position. Mothers were commonly primiparous and unattended by clinical staff before collapse was recognised. Approach to investigation was highly disparate and frequently very limited. Of the 30 infants with no underlying disease/abnormality, 22 (73%) developed a postasphyxial encephalopathy and 10 had a poor outcome (33%)--5 died and 5 had neurological sequelae at 1 year. INTERPRETATION: SUPC is rare in any one centre and there is no standard approach to investigation. In those cases where collapse is not due to an underlying abnormality, breast feeding and prone position are important associations. Guidelines for safe postnatal care of infants should include appropriate vigilance of infants particularly where mothers are primiparous or where ability to assess the baby may be impaired.