Chemistry: natural resins or derivatives; peptides or proteins; – Proteins – i.e. – more than 100 amino acid residues – Blood proteins or globulins – e.g. – proteoglycans – platelet...
Reexamination Certificate
1997-10-23
2001-01-09
Huff, Sheela (Department: 1642)
Chemistry: natural resins or derivatives; peptides or proteins;
Proteins, i.e., more than 100 amino acid residues
Blood proteins or globulins, e.g., proteoglycans, platelet...
C530S388250, C530S389300, C435S007910, C435S007920, C435S007950, C435S806000, C435S810000
Reexamination Certificate
active
06172198
ABSTRACT:
TECHNICAL FIELD
The present invention relates to: purified pregnancy-associated plasma protein-A (PAPP-A); PAPP-A variants; polynucleotides encoding PAPP-A; isolation and purification of PAPP-A; monoclonal antibodies raised against PAPP-A; use of these monoclonal antibodies and PAPP-A for diagnostic purposes, including a kit for the assaying of PAPP-A levels in a sample; use of PAPP-A measurement, in conjunction with another marker of trophoblastic activity (such as chorionic gonadotrophin or its subunits), to discriminate between feto-placental abnormalities, such as Trisomy 21 (Down Syndrome), and oncological status, such as Gestational Trophoblastic Diseases (GTD); use of PAPP-A monoclonal antibodies to isolate fetal trophoblast cells for prenatal fetal cytogenetic diagnosis; use of PAPP-A, as a target antigen for active immunological contraception, and PAPP-A antibodies as a passive contraceptive vaccine; use of PAPP-A as a medicament and a medicament comprising an effective amount of PAPP-A.
BACKGROUND ART
Placental proteins are those proteins expressed during pregnancy by the human placenta. The ability to detect the presence and concentrations of these proteins has the potential to provide a reliable diagnostic marker of fertilisation, implantation and pregnancy prognosis.
A number of placental proteins have now been isolated and at least partially characterised. These include—human chorionic gonadotropin (hCG), pregnancy-specific &bgr;
1
—glycoprotein (SP1), placental protein 5 (PP5), early pregnancy factor (EPF), and pregnancy-associated plasma protein-A (PAPP-A)
1.
These proteins are detectable, in maternal blood, at various stages during pregnancy. For example, EPF activity is detectable within 24 hours after conception. HCG is measurable just after implantation, at about 9 to 11 days post-ovulation, SP1 is detectable from 18 to 23 days post-ovulation. In singleton pregnancies, PAPP-A can be detected approximately 28-32 days post-ovulation
2
.
Placental proteins are also detectable for varying periods during pregnancy. For example, EPF is detectable at least for the first half of pregnancy, whereafter activity declines until it is totally absent during the third trimester in some women. HCG levels rise rapidly to peak at about 8 to 12 weeks gestation. The levels of SP1 rise exponentially with peak concentrations being reached at term pregnancy. Like SP1, PAPP-A concentrations also rise exponentially in the first trimester of pregnancy to peak at term
2
.
Whilst it has been suggested to measure the presence of placental proteins for early detection of pregnancy (for example, see European Application 316919), there is a growing body of documented evidence that at least some placental proteins, particularly PAPP-A, may be used to predict pregnancy viability, including early pregnancy failure, extra-uterine gestations, aneuploid and/or abnormal pregnancies, such as Down's Syndrome
3
and Cornelia de Lange Syndrome
4
.
PAPP-A, first described almost two decades ago
1
, is a large zinc containing glycoprotein, rich in carbohydrate, with many physicochemical similarities to a 2-macroglobulin
5
. It has been detected in maternal circulation
5
, pre-ovulatory ovarian follicular fluid
6
, in seminal plasma
7
and blood of patients with trophoblastic disease
8
.
PAPP-A is a homotetramer, with each monomeric subunit having a molecular weight of approximately 200 kDa. The subunits are linked by disulphide bonds to form dimers of approximately 400 kDa. Native PAPP-A consists of two dimers linked by Van der Waals (ionic) forces. Native PAPP-A has a molecular weight of approximately 820 kDa, regardless of whether it is derived from follicular fluid, seminal plasma, oncological or normal placental tissue
7
. The mature protein has a 2-&bgr;1 electrophoretic mobility, with an isoelectric point of approximately 4.2-4.5
9
. It is a non-competitive and potent inhibitor of human granulocyte elastase
10
.
It has been suggested that the biological function of PAPP-A is to act as a local protective barrier against host (maternal) phagocytic-proteolytic defences to either inseminated sperm or the developing feto-placental unit
11
. This may be due to PAPP-A forming a protective sheet around the chorionic villus at the utero-placental interface
12
. Disruption of this protective layer may explain the correlation between depressed PAPP-A levels and pregnancy failure. PAPP-A may also play a role in zinc homeostasis
5
.
Schindler and Bischof
13
suggested that the protein was ubiquitous and, therefore, of little practical use in pregnancy viability diagnosis.
14,15
However, it was subsequently shown that these results were due to impure PAPP-A isolates, due to the difficulties in isolating PAPP-A free of a 2-macroglobulin, and polyspecific antisera
16
.
Sinosich et al.
3
first suggested that a depressed or undetectable PAPP-A level in maternal blood was diagnostic of pregnancy failure. Later, Sinosich et al.
17
showed that, of five successful in vitro fertilisation volunteers, three patients with normal pregnancy outcome had circulating PAPP-A levels within the 80% confidence limits of the normal range. By contrast, circulating PAPP-A levels in the patient who spontaneously aborted at seventeen weeks were below the tenth percentile throughout the entire gestation. In the fifth patient, who had a ruptured ectopic pregnancy, PAPP-A could not be detected at any stage during the pregnancy. These findings were complimented by Westergaard et al. (1983)
18
, who reported that, in a sample group of 51 patients, who conceived spontaneously, with vaginal bleeding in the first half of pregnancy, concentrations of PAPP-A were consistently lower in pregnancies which failed. Similarly, Sinosich et al. (1985)
19
showed that, in a group of 21 women who conceived by in vitro fertilisation, PAPP-A levels were consistently depressed, for many weeks, in those women whose pregnancies failed. The same group showed that, of forty seven serum samples obtained from patients with a tubal pregnancy, only two were positive for PAPP-A, indicating that severely depressed or undetectable serum PAPP-A levels were an aid in the diagnosis of extra-uterine pregnancy.
20
In 1990, Brambati et al.
21
reported that first trimester maternal serum concentrations of PAPP-A were low in pregnancies associated with Down's syndrome. Later, Wald et al. (1992)
3
confirmed that PAPP-A concentration was significantly lower in women with Down's syndrome pregnancies compared to PAPP-A levels in a control group of normal pregnancies.
It has also been reported that PAPP-A was detected in the circulation of patients with hydatiform mole
2
, suggesting a potential role for PAPP-A quantification in diagnosis and management of certain tumours.
These findings demonstrate the potential diagnostic value of measuring PAPP-A levels for monitoring feto-placental status. Moreover, in view of the increasing use of in vitro fertilisation techniques, and the relatively high proportion of early pregnancy failures associated with these techniques, the measurement of PAPP-A levels to monitor pregnancy viability and thereby minimise patient trauma is clinically advantageous.
Lin. et al. (1974)
22
described the use of an electroimmunoassay to measure PAPP-A levels in advanced pregnancy. This assay was insensitive and limited to latter stages of pregnancy. Sinosich et al. (1982)
2
and (1984)
6
described the first sensitive radioimmunoassay (RIA) which detected PAPP-A in serum obtained from first trimester pregnancies. This assay used radioactively labelled purified PAPP-A together with rabbit anti-human PAPP-A antiserum. The sensitivity of this RIA (2.9 &mgr;g/L) enabled PAPP-A detection in maternal blood after the first six weeks of pregnancy. The assay made it possible to detect PAPP-A in other fluids (amniotic fluid, seminal plasma, follicular fluid, gestational trophoblastic disease, culture media), previously beyond the limits of detection. This assay also made it possible to study the kinetics and physiology of maternal PAPP-A levels i
Howson and Howson
Huff Sheela
Northern Sydney Area Health Service
LandOfFree
PAPP-A, its immunodetection and uses does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with PAPP-A, its immunodetection and uses, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and PAPP-A, its immunodetection and uses will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2475778