Children’s Health: Do Antibiotics Now Mean Asthma Later?

Asthma affects 1 in 8 school-aged children in industrialized countries, making it the most common chronic illness in this group. Now a meta-analysis of child asthma studies led by pharmaceutical scientist Fawziah Marra of the University of British Columbia shows that children diagnosed with asthma were twice as likely as nonasthmatics to have received antibiotics before age 1. The more courses of antibiotics a child received in the first year of life, the higher the risk for asthma. 
 
The meta-analysis, reported in the March 2006 issue of Chest, examined the link between antibiotic exposure in babies and subsequent development of asthma, as well as the dose–response relationship. Marra’s team analyzed four prospective studies and four retrospective studies conducted between 1999 and 2004. Each study involved between 263 and 21,120 children, including cases who had been diagnosed with asthma between the ages of 1 and 18 years. The number of antibiotic courses taken ranged from one to seven, and averaged three. 
 
Pooling the data from all eight studies revealed a twofold risk of developing asthma with at least one course of antibiotics. Each additional course raised asthma risk 1.16 times. Information about the antibiotics prescribed could not be obtained from the studies. 
 
The findings support the “hygiene hypothesis,” which proposes that an immune system that doesn’t get enough practice killing germs (due to either an excessively clean environment or overuse of antibiotics) will become overly sensitized and overreact to normally harmless environmental agents such as pollen and dust. 
 
Marra and her colleagues recently launched a community education campaign in British Columbia called “Do Bugs Need Drugs?” The program uses media ads, classroom visits, and educational materials to teach health professionals and the general public about the overuse of antibiotics. The campaign emphasizes the difference between bacterial and viral infections, useful preventive measures such as hand washing, and the need to use antibiotics wisely. “In children, antibiotics are commonly used to treat ear infections, upper respiratory tract infections, and bronchitis,” says Marra, even though many such infections are viral and don’t respond to antibiotics. Some parents may refuse to leave a doctor’s office without a prescription. 
 
The information gained from the meta-analysis is valuable for physicians who are striving to cut back on prescribing antibiotics, says W. Michael Alberts, president of the American College of Chest Physicians: “It can help to convince parents of young children to hold off on giving antibiotics unless absolutely necessary.”

Identification of the peanut-agglutinin binding pancreatic cancer serum marker in pancreatic tissue extracts C.K. Ching & J.M. Rhodes University Department of Medicine and Walton Hospital, Liverpool, UK.
Pancreatic disease can be notoriously difficult to diagnose so there has been considerable interest recently in the development of tests for serum glycoprotein markers of pancreatic cancer.These have usually been carried out with the aid of monoclonal antibodies produced against tumour or cell line extracts.Potential serum markers for pancreatic cancer have included carcinoembryonic antigen (CEA) (Gold & Freed- man, 1965; Zamcheck & Martin, 1981), pancreatic oncofetal antigen (POA) (Banwo et al., 1974; Nishida et al., 1985), pancreatic carcinoma associated antigen (PCAA) (Schultz &  Yunis, 1979; Shimano et al., 1981), DU-PAN 2 (Metzgar et  al., 1984; Sawabu et al., 1986) and CA19-9 (Koprowski et al.,  1979; Magnani et al., 1983; Haglund et al., 1986).As most of the marker antibodies so far characterised have been found to recognise carbohydrate rather than protein epitopes (Feizi, 1985), a previous study was carried out to determine whether further tumour marker glycoproteins could be more efficiently identified using a combination of SDS-polyacrylamide gel electrophoresis and blotting with a panel of lectins chosen for their ability to identify different carbohy- drate epitopes.This approach proved successful demonstrat- ing the presence of a high molecular weight glycoprotein in approximately one-third (12/34) of the pancreatic cancer sera but in none of the 96 controls (Ching & Rhodes, 1988).Further characterisation showed this serum marker to be a mucin (Ching & Rhodes, 1987a).This has subsequently been developed into an enzyme-linked peanut lectin assay (PNA- ELLA) (Ching & Rhodes, 1989) for total peanut lectin bind- ing glycoproteins in serum.This assay has proved equivalent in efficacy to CA19-9 serum radioimmunoassay and the two tests together have a combined sensitivity of 85% for pan- creatic cancer (Ching & Rhodes, 1989).
Although proving useful as a serum test for pancreatic cancer, the epitope for CA19-9 is known to be present in normal pancreatic tissue (Atkinson et al., 1982) and juice (Kalthoff et al., 1986), bile (Albert et al., 1987) and colon (Afdhal et al., 1987) in a way analogous to CEA (Go et al., 1975;Huitric et al., 1976;Ichihara et al., 1988).This study was performed to determine whether the peanut agglutinin binding glycoprotein could also be detected in normal or diseased pancreatic tissue.
Pancreatic tissue glycoprotein extraction was performed according to Rao and Shinozuka (1984) with minor modification.Approximately I g wet weight pancreatic tissue was used per specimen.Samples were cut into small pieces and then ultrasonicated (Ultrasonicator KS 100, Kerry Ultra- sonics, UK) for 1 min in 10 ml Tris HCI (20 mM, pH 7.4)/ EDTA (1 mM) buffer containing 200Lg ml-' soybean trypsin inhibitor.This was followed by homogenisation in a Polytron homogeniser (PCU, Kriens-Luzern, Switzerland) and then centrifugation at 13,000g (Sorvall RC5, DuPont instruments, USA) for 20 min.Supernatants were discarded because preliminary analysis of concentrated supernatants from two normal pancreatic tissues did not reveal any PNA binding glycoproteins identifiable on lectin blotting from the gel.The pellets were washed x 5 and then each sample re- homogenised separately in I ml of the same buffer for 30 s.One ml of the homogenised tissue was mixed with 9 ml of chloroform/methanol (2: 1) mixture and stirred vigorously for 30 min.The aqueous phase was separated from the lipid phase and the solid residue by centrifugation at 300 g (Centaur 2, Fison instrumentation services, UK) for 20 min.The aqueous phase was then concentrated by gentle evaporation under nitrogen to approximately 1/4 of its original volume and glycoprotein precipitation was carried out using nine equivalent volumes of the aqueous phase of absolute ethanol.The precipitate was obtained by centrifugation at 200 g for 10min.
Glycoprotein precipitates were reconstructed in 400 l of de-ionised, distilled water.An aliquot was used for Lowry protein estimation (Lowry et al., 1951).SDS-PAGE (using approximately 100 iLg protein per sample), and then high intensity transfer of proteins and glycoproteins on to nitro- cellulose papers and finally identification of PNA binding glycoproteins on the blots were performed as described before (Ching & Rhodes, 1988).The high molecular weight PNA binding glycoprotein identified in the tissue extracts was then further characterised using other lectins, UEA I (25 jgml-'), LFA (12.5 ig ml-') and GS 2 (25 JLgml-').
The mean yield of water soluble protein obtained from one extraction step ranged between 2-4.5 mg g-' pancreatic tissue.A high molecular weight (approximately 3.5 million Da) PNA binding glycoprotein (lane 3, Figure 1) having identical electrophoretic mobility to the serum marker, both before and after purification, was identified in tissue extracts from 3/3 pancreatic cancers, 1/4 chronic pancreatitis and 2/5 nor- mals.The sole ampullary carcinoma extract studied did not contain the high molecular weight glycoprotein at 3.5 x 106 Da but it showed a strong PNA binding region around 1 x 106 Da, indicating the possibility of another tumour related PNA + glycoprotein in this epithelial car- cinoma.A lower molecular weight (50,000 Da approximately) peanut agglutinin binding glycoprotein was also present.This was co-purified with the 3.5 million Da glycoprotein and was still present after the 3.5 million Da glycoprotein had been cut out of the gel, eluted and rerun.Characterisation of the water soluble pancreatic tissue PNA binding 3.5 million Da FER2-Figure 1 Result of peroxidase-PNA lectin blotting after electro- phoresis on a 2-16% SDS-polyacrylamide gel showing the presence of the high molecular weight glycoprotein (arrowed) in pancreatic cancer (lane 3) and normal pancreatic (lane 5) tissue extracts having the same electrophoretic mobility as the serum marker.Lane 1, purified serum marker from pancreatic cancer; lane 2, original pancreatic cancer serum of sample loaded in lane I; lane 4, ampullary carcinoma tissue extract.Molecular weight markers: Thy, thyroglobulin 330,000 Da; Ferl, ferritin 1 220,000 Da; Alb, albumin 67,000 Da; Cat, catalase 60,000 Da; Lac, lactate dehydrogenase 36,000 Da Fer2 ferritin 2 18,500 Da.
glycoprotein by the use of other lectins showed that it bound LFA but not UEA I and GS 2 lectins (Table I) indicating the expression of the epitopes gal 1-3 gal NAc (blood group T antigen), and sialic acid but not L-fucose (blood group H antigen) or GIc NAc (blood group Tk antigen).Other PNA binding glycoproteins present on the blots are probably nor- mal pancreatic epithelial structure components as we have previously shown in a lectin histochemical study that PNA binding glycoproteins other than the secreted mucus can be identified (Ching et al., 1988).This study has demonstrated that a peanut lectin (PNA) binding glycoprotein previously found in pancreatic cancer serum is also present in the pancreatic tissue itself not only in pancreatic cancer but also in benign pancreatic disease and in the normal pancreas.Both serum and tissue PNA binding glycoproteins had identical electrophoretic mobility.The lec- tin binding characteristics of the tissue glycoprotein extracted from benign and malignant pancreas indicate that it pos- sesses gal I1-3 gal NAc (PNA binding) and sialic acid (LFA binding) side chains.These epitopes have been demonstrated on the serum glycoprotein (Table I) which variably bears additional epitopes namely L-fuCose (H antigen, UEA I bind- ing) and glc NAc (Tk antigen, GS2 binding) (Ching &  Rhodes, 1987b).
compared with gastrointestinal tumours such as colonic and gastric tumours as shown by the higher rate of positive serum tests in pancreatic cancer using both enzyme-linked PNA assay and CA19-9 radioimmunoassay, even though the CA19-9 antibody was raised against a colorectal cancer cell line.In a previous study, we have shown that the PNA binding pancreatic cancer-related serum mucus glycoprotein sometimes but not always expresses the CA19-9 epitope (Ching & Rhodes, 1988).The binding sites for PNA (gal 1-3 gal NAc) and CA19-9 (sialylated N-fucopentaose II oligosaccharide) cannot occur on the same oligosaccharide side chains so we envisage the tumour-related mucin as a complex glycoprotein that may variably express the sialylated Lewis antigen (CA19-9 epitope) on some side chains, the PNA epitope (T antigen) on others and UEA I (H antigen) and GS2 (Tk antigen) binding sites on yet other side chains.Simultaneous demonstration of an additional carbohydrate epitope (CA-242) on the tumour marker glycoprotein CA5O has also been reported recently (Nilsson et al., 1988).
The sialylated Lewisa antigen has been found in normal colon (Afdhal et al., 1987), bile (Albert et al., 1987) and pancreatic juice (Kalthoff et al., 1986) so seems to be a normal tissue and mucin glycoprotein that is abnormally expressed in the serum in cancer rather than an oncofetal antigen.The status of the PNA binding site (T antigen) is more uncertain.It behaves more as an oncofetal antigen in colon (Boland et al., 1982; Cooper, 1984; Rhodes et al.,  1986), breast (Howard et al., 1981), stomach (Kuhlmann et  al., 1983), ovary (Soderstrom, 1988) and lymphoid (Ree & Hsu, 1983) tissue.It can be predicted from the known struc- ture of mucin that the T antigen can only be present as the base pair of the oligosaccharide side chain (Hounsell & Feizi,  1982) which is usually concealed by further glycosylation or sialylation.It seems likely that its expression at least reflects a relatively immature mucin side chain.In a previous study using lectin histochemistry, PNA binding has however been found variably in normal pancreatic cytoplasm (Ching et al., 1988) and in normal large bile ducts (Rhodes et al., 1988) and the study presented here confirms that it can be variably expressed in normal pancreas.
The presence of mucin in serum is perhaps surprising, but the CA19-9 epitope bearing mucin has also been found in pancreatic cancer (Haglund et al., 1986) and in patients with cystic fibrosis (Roberts et al., 1986).In pancreatic cancer, this might reflect either early invasion of this tumour into blood vessels or early ductal obstruction with reflux.It is clear from our study that this mucin contains at least four different oligosaccharide side chain structures and probably many more so development of a panel of monoclonal antibodies against different epitopes on this mucin may lead to the development of a more sensitive and specific test for pancreatic cancer.C.K.C. was an Amelie Waring research fellow of the British Digestive Foundation.

Table I
Lectin binding characteristics of the high molecular weight pancreatic cancer-related serum and water soluble tissue glycoproteins