Patent Application: US-89428607-A

Abstract:
the present invention relates to methods for determining predisposition to acute life threatening episodes and / or sudden infant death syndrome and , in particular , to methods of assessing potential susceptibility to development of alte and / or sids by determining a subject &# 39 ; s total iga and / or iga1 .

Description:
a preferred embodiment of the invention will now be described , by way of example only . total iga , igg and igm levels in saliva of infants with alte whole mixed saliva was collected by gentle suction from the buccal cavity of the mouth [ 15 ]. this technique is successful in children ( aged from 1 day ) and adults [ 1 , 16 ]. a standardised questionnaire was used to collect the relevant sids related demographics . the classification into the “ near - miss ” sids group ( alte ) was made by the attending paediatrician on the basis of clinical investigations . salivary immunoglobulins were measured by elisa and albumin by rate nephelometry ( beckman . array ) [ 16 ]. the differences in mucosal immune parameters was determined between the alte infants and two control groups of subjects ( mild urti and well infants ) using analysis of variance ( anova ) or the appropriate non - parametric statistics . 37 subjects aged 1 - 10 months were recruited ( 20 males , 17 female ) in 3 categories : acute life threatening episodes ( alte ) at john hunter hospital ( n = 5 ) mild respiratory tract illness ( mild ) from general practitioners ( n = 11 ) a well control group ( well ) from immunisation clinics ( n = 21 ). there were more males ( n = 4 ) than females ( n = 1 ) in the alte group . there were no significant differences between the groups for age , birth history , family demographics , ethnic background or family history of sids . there were a higher percentage of children exposed to passive tobacco smoke ( 60 %, n = 3 ) in the alte group compared to the mild ( 36 %, n = 4 ) and well ( 10 %, n = 2 ) control groups ( p = 0 . 03 ). the alte group had a higher percentage of families in the average - below average socioeconomic category ( 100 %) compared to the other control groups ( p & lt ; 0 . 01 ). there were no differences between the groups for feeding history , immunisation status , sleeping position . in 4 of the 5 alte subjects an upper respiratory tract illness ( urti ) was suspected as the cause of the alte ( table 1 ). two samples of saliva were collected from each subject . the first sample was collected from the alte group within 24 hours of admission to hospital and from the mild respiratory illness group within 48 hours of presentation of their general practitioners . the well group were recruited from immunisation clinics and saliva collected at ages to approximate the ages of presentation of the alte and mild groups . the second sample was collected 14 days later from each subject . the figures in appendix c have the age related 5 th - 95 th percentile reference ranges indicated for each salivary immunoglobulin over the first year of life . the salivary iga , igg and igm concentration in the alte group were all significantly higher than the mild ( tables 2a and 2b ) and well ( tables 3a and 3b ) groups for both sample 1 and 2 ( fig1 and 2 ). there were no significant differences between the mild and well groups for either sample 1 or sample 2 ( tables 2c and 3c ). there were two subjects in the mild group who had grossly elevated salivary immunoglobulin concentrations in the 14 day collections . ( see appendix c ). ro9 had an elevated igm that is most likely accounted for by immunisation with triple antigen and haemophilus influenzae b 14 days prior to the saliva collection . table 2a first sample analysis of immunoglobulins - alte vs mild alte mild n median range n medial range p - value iga 5 115 . 55 ( 27 - 411 ) 11 9 . 93 ( 0 - 37 ) & lt ; 0 . 01 igg 5 9 . 21 ( 0 - 16 ) 11 0 . 00 ( 0 - 3 ) 0 . 02 igm 5 4 . 61 ( 3 - 24 ) 11 2 . 18 ( 0 - 16 ) 0 . 04 table 3c second sample analysis of immunoglobulins - alte vs well mild well n median range n medial range p - value iga 11 8 . 88 ( 1 - 255 ) 20 10 . 53 ( 0 - 58 ) 0 . 71 igg 11 0 . 00 ( 0 - 4 ) 20 0 . 00 ( 0 - 6 ) 0 . 75 igm 11 2 . 31 ( 0 - 27 ) 20 1 . 66 ( 0 - 14 ) 0 . 56 the grossly elevated salivary iga concentration in 4 of 5 alte subjects at presentation was not observed in the mild or well control groups . salivary iga can therefore act as a marker for alte ( and sids ) in subjects presenting with an otherwise mild respiratory illness . this was an unexpected result since the prior art [ 1 ] suggested igm would be the most useful parameter in prediction of alte / sids susceptibility . the elevated salivary iga and igm concentrations in 4 of 5 alte support the concept of an infection or inflammatory cause in alte ( and sids ). rsv positive bronchiolitis was evident in 3 of 5 alte subjects . total iga and iga1 subclass in saliva of infants with alte saliva samples were collected from infants on the day of admission to hospital for an unexplained acute life - threatening episode ( alte ). the infants were included in this study if all congenital or obstructive causes of apnoea had been excluded . this group of subjects have been classified as the “ near - miss sids ” infants . saliva was collected from age matched control subjects in two categories . normal healthy infants were recruited from the child immunisation clinics and classified as well infants . the second group was recruited from general practitioners , who referred infants with a mild upper respiratory infection and these infants were classified as the mild infection control group . saliva was collected on the day of referral with the mild infection . saliva samples were assayed by an enzyme linked immunosorbant assay ( elisa ) to detect total iga and iga1 subclass antibodies . the assay uses a who / iuis approved monoclonal antibody for iga1 subclass as the capture antibody in conjunction with a polyclonal antibody - enzyme labelled detection system . the results indicate that the concentrations of iga1 subclass in the saliva from infants suffering an alte were significantly higher than the concentrations for the infants in the control groups of normal healthy infants and those suffering a mild upper respiratory infection ( p = 0 . 009 ) ( table 4 and fig7 a and 7b ). the concentrations of iga1 in saliva from the normal healthy infants were not significantly different from those with mild respiratory illnesses . five samples were assayed from each of the three study groups : alte babies , babies with mild infection , and well babies . the level of iga1 was generally much higher in the samples from the alte babies compared to the levels in the other two groups ( p = 0 . 009 ). levels in the mild infection and well baby groups were similar . the non - parametric kruskal - wallis test was used to compare the distributions of iga1 values for the three groups . the probability of the three sample groups having equal iga1 distributions is p = 0 . 009 . due to small sample sizes , the estimated 95 % confidence intervals about the group medians are equivalent to the range ( i . e . min , max ) of the data iga1 concentrations are significantly elevated in infants suffering an unexplained alte ( 4 out of 5 children ). three out of the same 5 children with alte were found to have elevated total iga levels . therefore , although it is clear that both iga and iga1 are useful parameters in the prediction of alte , iga1 levels may be the more useful parameter . since alte are classified as “ near - miss ” sids ( when no other medical condition is identified ), it follows that both iga and iga1 are also useful parameters in the prediction of sids . although the invention has been described with reference to specific examples , it will be appreciated by those skilled in the art that the invention may be embodied in many other forms . 1 . gleeson m , clancy r l , cripps a w ( 1993 ) mucosal immune response in a case of sudden infant death syndrome . paed res vol 33 : no 6 554 - 556 . 2 . thrane p s , rognum t o , brandtzaeg p ( 1990 ) increased immune response in upper respiratory and digestive tracts in sids . lancet 1 : 229 - 230 . 3 . forsyth k d , weeks s c , koh l , skinner j , bradley j ( 1989 ) lung immunoglobulins in the sudden infant death syndrome . british medical journal 298 : 23 - 26 . 4 . stolenberg l , saugstad o d , rognum t o ( 1992 ) sudden infant death syndrome victims show local immunoglobulin m response in tracheal wall and immunoglobulin . a response in duodenal mucosa . paed res 31 : 372 - 375 . 5 . guntheroth w g ( 1989 ) interleukin - 1 as intermediary causing prolonged sleep apnea and sids during respiratory infections . med hypotheses 28 : 121 - 123 . 6 . gleeson m , dobson a j , firman d w , cripps a w , clancy r l , wlodarczyk j h , hensley m j ( 1991 ) the variability of immunoglobulins and albumin in salivary secretions of children . scand j . immunol . 33 : 533 - 541 . 7 . wilkinson m , jones c ( 1997 ) australian sids statistics . australia sids conference . abstract 301 . 8 . blackwell c c , weir d m , busuttil a ( 1997 ) infectious agents and sids : analysis of risk factors and preventive measures . sids and infant mortality . 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