NON HUMAN TRANSGENIC ANIMAL AS A MODEL OF NEURODEGENERATIVE DISEASES AND FOR THE EARLY DIAGNOSIS THEREOF $ # * The present invention relates to a non human transgenic animal as a model for neurodegenerative diseases and for their early diagnosis Introduction The study of NGF (Nerve Growth Factor) action can be conducted by means of animal models in which the action of NGF is blocked by neutralizing anti-NGF antibodies (Angeletti and Levi-Montalcini, 1971; Gorin and Johnson, 1979, 1980; Molnar et al., 1998) or by knockout of the gene that synthesizes NGF (Crowley et al5 1994; Chen et al., 1997). The approach of producing a transgenic mouse that expresses recombinant antibodies neutralizing NGF (Ruberti et al., 2000, PCT application WOO 1/10203) has highlighted two results. In the first place, the inactivation of NGF by means of neutralizing recombinant antibodies has allowed to provide a model for studying the effects of NGF neutralization on adult organisms: the gene knockout approach did not allow to do so, because ngf ";" mice die shortly after birth, without any chance for any neurodegenerative diseases connected to aging to develop (Crowley et al., 1994). The second result consists of actually producing an animal model for one of the most common neurodegenerative diseases among the elderly, i.e. Alzheimer's disease (Capsoni et al., 2000a; Capsoni et al., 2000b; Capsoni et al., 2002a, b, c; Pesavento et al., 2002). The fact that Alzheimer's disease was reproduced in mice can be linked to 2 factors: (i) the neutralization of NGF (ii) the introduction of an antibody that neutralizes an endogenous protein in mice's organism. Different experimental evidences suggest that NGF can play an important role in Alzheimer's disease. This pathology is characterized by progressive dementia which affects the elderly with an incidence exceeding 30% in patients over 80 years of age. The incidence of the disease, linked to the progressive increase in life expectancy, is destined to double over the next 30-50 years. Since there is no therapy, the disease has extremely high social costs. The etiology of Alzheimer's disease is unknown and its immediate causes may be many and reside not only in the encephalon but also in non nervous tissues of the body's peripheral regions, since cells of the immune, hematopoietic and circulatory systems appear to be altered in patients affected by Alzheimer's disease (Gasparini et al., 1998). Li particular, there is a hypothesis that one of the factors causing neurodegeneration could be auto-antibodies which trigger an auto-immune or auto- toxic reaction (McGeer and McGeer, 2001). Since cholinergic neurons of the basal forebrain express NGF receptors, it has been hypothesized that deficits in the retrograde transport and alterations in the signal transduction of the NGF/receptor system may be one of the possible causes of Alzheimer's disease. To date, there is no early diagnosis or therapy for the disease due to the lack, up to a short time ago, of experimental cellular or animal models that reproduce the disease in a complete fashion. Transgenic mice that produce the mutated forms of the amyloid precursor protein, APP, the hyperphosphorylated form of tau or the mutated forms of presenilin 1 or 2 (Gotz, 2001; Janus et al., 2001) do not reproduce all characteristics of Alzheimer's disease. The attempt to obtain a complete model by crossing transgenic mice that express different mutated proteins linked to Alzheimer's disease, while allowing to obtain mice with larger neurodegenerative lesions than in parental mice, failed because they express the mutated proteins independently from an overall pathological process, and in any case they do not exhibit cholinergic deficits nor significant cell death (Borchelt et al., 1997; Oddo et al., 2003). The most complete model of the disease was obtained through the expression of NFG neutralizing recombinant antibodies (alfaDl l, Cattaneo et al., 1988). These mice are characterized by the presence of behavioral deficits (Capsoni et al., 2000b) and synaptic plasticity deficits (Pesavento et al., 2002), events linked to loss of cholinergic neurons, neuron loss in the cortex, tau hyperphosphorylation with formation of intracellular tangles, deposit of /3-amyloid plaques (Capsoni et al., 2000a; Capsoni et al., 2000b; Capsoni et al., 2002a; b; c). These mice's Alzheimer's phenotype demonstrates that an Alzheimer' s-type neurodegeneration is induced by blocking NGF activity. This could have relevance for the situation in humans. ADI l anti-NFG mice, which express the functional form of the oDll monoclonal antibody, were produced by crossing mice that express the heavy chain of the transgenic antibody (VH-ADI l mice) with mice that express the light chain of the antibody (VK-ADIl mice). "Exogenous chains" means the VH and VK transgenic antibody chains of the oDl l recombinant antibody, whereas "endogenous chains" means the antibody chains of the antibodies produced by the mouse's lymphocytes. In spite of the advantages obtained with this technique, having to continuously re- cross the mice of the two lines VH-ADl 1 and VK-ADl 1 requires having to maintain 3 lines of animals, instead of a single one. Another disadvantage is the poor reproductive ability of anti-NGF ADIl mice. Indeed, crossing different transgenic mice with each other is a useful experimental procedure, because it enables to obtain information on the combined activities of the transgenes of the parental lines, thereby generating new experimental models. In the case of anti-NGF ADI l mice, this possibility of crossing with other transgenic mice is made difficult, if not impossible, since anti-NFG ADl 1 mice have poor reproductive ability. Description of the Invention The authors of the invention have surprisingly found that VK-ADIl mice, which express a single transgenic chain VK, in the absence of the corresponding transgenic chain VH, exhibit a complex neurodegenerative picture, similar to that of anti-NGF ADI l mice. This occurs because the exogenous light chain of the recombinant antibody is assembled with an endogenous heavy chain of mouse IgG, to yield a functional NGF neutralizing antibody. It is noteworthy that VH-ADIl mice have no phenotype linked to a neurodegenerative picture. Finally, the authors have shown that VK-ADl 1 mice reproduce effectively. According to the invention, an improvement is obtained in the procedure for obtaining a transgenic mouse, which is a complete and unique model for Alzheimer's disease, and for assessing the implications of an alteration at the level of the immune system in the emergence of the disease. Indeed, the heavy chain of an endogenous antibody cannot assemble with the light chain of an antibody, except in lymphocytes (Abbas et al., 2000). Therefore, the cerebral alterations observed in the mouse described in this invention can only be due to antibodies produced first in the blood and hence can only be secondary to alterations of the hematoencephalic barrier which allows the passage of the transgenic antibodies and/or of eventual cells of the immune system from the periphery to the central nervous system. Therefore, VK- ADIl mice allow to analyze the peripheral alterations (and in particular antibodies produced by peripheral lymphocytes), able to determine the onset in the central nervous system of a neurodegeneration similar to Alzheimer's disease. Thus this result suggests a method for the early diagnosis of the disease, based on the determination in biological samples of Alzheimer's patients of antibodies directed against NGF or proteins required for its mechanism of action. These characteristics are absent in other animal models for Alzheimer's disease and consequently the mice described in the present invention represent a unique model to study the importance of these components in the etiology of the disease and to develop early diagnostic methods. Detailed description of the invention Therefore, the object of the invention is a non human transgenic animal able to express ubiquitarily an anti-NGF neutralizing antibody in which the antibody is composed by an endogenous VH chain and by an exogenous VK chain. Preferably, the exogenous VK chain is that of the anti-NGF ADIl antibody, having essentially the amino acid sequence of SEQ ID No. 1, as follows: aDll VK human Ck DIQMTQSPASLSASLGETVTIECRASEDIYNALAWYQQKPGKSPQLLIYNTDTLHTG VPSRFSGSSGTQYSLKINSLQSEDVASYFCQHYFHYPRTFGGGTKLELKRTVAAPSV FIFPPSDEQLKSGTASWCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDST YSLS STLTLSKADYEKHKVYACEVTHQGLS S PVTKS FNRGEC . In a preferred embodiment, the non human transgenic animal belongs to the murine genus, preferably to the Mus musculus species. The object of the invention is the use of the non human transgenic animal as an animal model for identifying compounds with therapeutic activity for pathologies, in particular neurodegenerative pathologies. Further object of the invention is the use of the non human transgenic animal for crossing with a second non human transgenic animal for at least one other function involved in pathologies, also neurodegenerative, and obtaining a line of non human transgenic animals with at least two transgenes, in which said transgenes codify for functions involved in pathologies, also neurodegenerative. Preferably, the second non human transgenic animal is homozygote "knockout" for the gene of the NGF receptor, p75NTR or parts thereof. The scope of the invention further includes a method for the early prognosis and/or diagnosis of neurodegenerative diseases comprising the drawing of a peripheral biological fluid from a patient and the detection in said fluid of antibodies anti-NGF, or anti-TrkA or against proteins linked to NGF activity. Preferably, the peripheral biological fluid is blood, serum or urine. Preferably, the neurodegenerative disease is Alzheimer's Disease. The present invention describes a non human transgenic animal that expresses an antibody neutralizing the Nerve Growth Factor (NGF). The antibody used is constituted by the endogenous heavy chain of IgG and by the light chain of the αDl 1 recombinant antibody. The αDll antibody specifically binds NGF at the epitope responsible for its binding with its high affinity receptor, TrkA. Consequently, the anti-NGF antibody blocks the binding of NGF to its receptor and neutralizes its activity. Transgenic mice that express this anti-NGF antibody (VK-ADIl mice) develop antibody levels ranging between 50 and 500 ng/ml in adult age, and develop a complex pathological picture whose characteristics are summarized as: 1) dilation of the cerebral ventricles; 2) atrophy of the cerebral cortex associated to atrophy of the hippocampus; 3) loss of neurons and apoptosis; 4) deposition of β-amyloid plaques in the hippocampus and cerebral cortex; 5) neurofibrillary tangles; 6) tau hyperphosphorylation at the cerebral level; 7) aggregation of the tau protein at the cerebral level; 8) cognitive deficit characterized by "working memory" deficits and deficit in terms of spatial orientation; 9) cholinergic deficit in the basal forebrain and Meynert's nucleus; 10) alternations of sympathetic innervations of the cerebral arteries; 11) alterations of the permeability of the hematoencephalic barrier; 12) decrease in the volume and number of neurons in the upper cervical ganglia. Many of the characteristics described in this transgenic model are wholly similar to those present in Alzheimer's disease. The VK ADIl model therefore is suitable for use as an instrument for etiologic research and for the experimentation of new potential therapeutic agents and diagnostic means. A further aspect of this invention relates to the use of VK-ADIl mice to produce new mice deriving from the crossing of these mice with other transgenic mice. Description of the figures Figure 1. Transcriptional unit used for the production of the VK-ADIl transgenic mouse. CK constant human region, VL variable regions of the light chain of the oDl 1 monoclonal antibody; pCMV promoter of the human Cytomegalovirus. Figure 2. PCR analysis of VK transgenic mice. Figure 3. (A) Levels of recombinant antibody in 60 day old adult mice, measured in serum by incubation with an antibody anti human light chain and anti heavy chain of mouse IgG. The antibody anti mouse light chain does not show the presence of cross- reactivity. (B) Levels of transgenic antibody in the serum and in the cerebral tissue, quantified by comparison with a standard curve. The dotted line indicates the limit of detection of the assay (0.1 ng/ml and 0.1 ng/mg, respectively). Figure 4. The images show the representation of: (A) an NGF neutralizing antibody constituted by an exogenous VH chain and a transgenic VK chain; (B) an antibody constituted by a heavy endogenous chain and a transgenic VK chain. Figure 5: Expression of the VK light chain of the transgenic antibody in the cerebral cortex of the VK-ADI l mouse. (B) Absence of the expression of the VK light chain of the recombinant antibody in WT mice. Figure 6. Body weight of the VK-ADI l mouse and of the control mouse at two months of age. Figure 7. Reduced area of the median sagittal section of the upper cervical ganglion in the VK-ADIl mouse (A) with respect to the one observed in the control mouse (B). Figure 8. (A) Sympathetic innervations of the basilar artery of VK-ADIl mouse is decreased with respect to what is observed (B) in the control mouse. Figure 9. The chart shows the increase in Evans Blue concentration in the cerebral tissue due to the breaking of the hematoencephalic barrier. Figure 10. Atrophy of the cerebral cortex and of the hippocampus in VK-ADIl mice. The measurements were obtained from coronal sections of the mouse encephalon at the level of the parietal cortex and of the antero-dorsal part of the hippocampus. Figure 11. Progressive decrease in the total number of cholinergic neurons in the basal forebrain of VK-ADl 1 mice with respect to control mice of the same age. Figure 12. Decrease in the number of cholinergic neurons in the basal forebrain is particularly marked in the medial septum (MS). Figure 13. (A) Tau hyperphosphorylation in the hippocampus of 6 month old VK- ADl 1 mice. (B) Tau hyperphosphorylation in the cerebral cortex of 6 month old VK- ADI l mice. (C) Presence of tangle-like formations in 15 month old VK-ADI l mice. (D) Absence of staining with the mAb AT8 antibody in control mice of the same age. Figure 14. Presence of protofibrils of phosphorylated tau, marked with the antibody AT8 and comprised in the tangles, in the VK-AD 11 mouse. Figure 15. (A) Enlargement of β-amyloid plaques marked with the monoclonal antibody 4G8 in 15 month old VK-ADI l mice. (B) Absence of plaques in control mice of the same age. Figure 16. (A) Spatial orientation test conducted in VK-ADIl mice and in control mice at 8 months of age. Figure 17. Object discrimination test in VK-ADIl mice and in the control mice conducted at 6 months of age. Figure 18. The treatment with NGF administered intranasally improves (A) the cholinergic deficit, (B) decreases the number of cells containing β-amyloid and (C) the number of cells that express phosphorylated tau. Figure 19. The table shows the better reproductive ability of VK-ADI l mice with respect to ADIl mice. Figure 20. Validity of the use of VK-ADIl mice with respect to ADI l mice to obtain transgenic mice. Figure 21. Outline of the method for diagnosing Alzheimer's disease, based on the presence of anti-NGF antibodies or antibodies directed against NGF-correlated proteins. Figure 22. Presence of anti-NGF and anti-TrkA antibodies in the serum of patients affected by Alzheimer's disease. Example 1: Production and characterization of the VK-ADIl transgenic mouse Production of API VK mice The VK-ADI l mice were obtained from the injection into the pronucleus of fertile eggs of C57BL/6 x SJLF2 hybrid mice of the plasmide pcDNA-neo/VKαDl IHuCK containing the transcriptional unit of the gene of the light chain of the oDll transgenic antibody (Figure 1) conducted according to standard methods (AlIe et al, 1987). Crossing heterozygote mice allowed to obtain two lines of homozygous mice (line A and line B) that express the VK-ADl 1 chain in different quantities. The mice are fertile and the lines were brought to homozygosity. Molecular analysis of the mice was performed by PCR on genomic DNA extracted from tail biopsies (Fig. 2A). Characterization of the transgenic antibody The presence of a chimeric antibody obtained from the assembly of an endogenous heavy chain of IgG with the light chain of the oDll recombinant antibody was verified by ELISA of the sera and of the extracts of VK-ADl 1 transgenic mice. The plate for ELISA was incubated with NGF (5 μl/ml) and the transgenic antibody was made to bind to NGF. The recognition of the antibody is possible both with a specific biotinylated for the murine heavy chain of IgG and with a specific antibody for the human light chain of IgG. Both antibodies recognize the transgenic antibody linked to NGF (Figure 3A). The level of anti-NGF chimeric antibody measured in the serum and in the cerebral tissue of the A and B mice lines exceed 100 ng/ml and 100 ng/mg. In the adult mouse, antibody levels are greater by three orders of magnitude than the antibody level detected in mice aged between 1 and 30 days (0.1 ng/ml in serum and 0.1 ng/mg in cerebral tissue) (Figure 3B). Therefore, the conclusion is that NGF is recognized both by the antibody composed by the two transgenic chains VH and VK (Figure 4A), and by the hybrid antibody constituted by the endogenous heavy chain and by the transgenic VK chain (Figure 4B). Phenotypic characterization of the VK-ADIl mouse The tissues of the VK-ADI l mice were fixed by intracardiac perfusion of 4% paraformaldehyde in PBS, cryoprotected in 30% saccharose, and then sectioned. The sections were preincubated in 10% bovine fetal serum and then processed with immunohistochemical technique to detect the presence of the light chain of the recombinant antibody in the cerebral cortex of the VK-ADl 1 mice (Figure 5). Example 2 Phenotypic knock-out of the NGF in the VK-ADl 1 transgenic mouse Phenotypic characterization of the VK-ADI l mouse was conducted by macroscopic analysis and immunohistochemistry techniques. The experiments were conducted in groups of ten (n = 10) with animals having antibody levels of 50-400 ng/ml. Normal, non transgenic mice of the same strain were used as controls. At macroscopic level, VK-ADI l mice do not exhibit relevant abnormalities during the first 4-6 weeks of life. However, a slowdown in growth is observed which is translated into a 20% decrease in body weight with respect to the control mouse (Figure 6). At the histological level, the following differences were observed with respect to normal mice: (1) reduced area of the upper cervical ganglion; (2) increased permeability of the hematoencephalic barrier; (3) reduced sympathetic innervation of the cerebral arteries; (4) reduced cholin-acetyltransferase synthesis; (5) atrophy of the cerebral cortex and of the hippocampus (6) hyperphosphorylation of the tau protein and presence of intracellular tangles of tau protein; (7) presence of β-amyloid plaques; (8) behavioral deficits. (1) Reduced area of the upper cervical ganglion. At the level of the peripheral nervous system, the upper cervical ganglia are smaller than in the control, with a 25% reduction in the surface of the mean section. The number of cells is also reduced by 50% (Figure 7). (2) Reduced sympathetic innervation of the cerebral arteries. The sympathetic innervation of the cerebral arteries is strongly reduced in VK-ADl 1 mice with respect to control mice, as demonstrated by the reduced expression of the tyrosine hydroxylase marker protein (Figure 8), measured by means of the anti- tyrosine hydroxylase antibody (Chemicon). (3) Increased permeability of the hematoencephalic barrier An increase in the permeability of the hematoencephalic barrier is observed after injection of the Evans Blue coloring substance, a, marker whose presence is measured by spectrophotometry after intravenous injection into the mice. An increase in the quantity of colorant indicates an increase in the permeability of the hematoencephalic barrier to proteins (among them the antibodies) that normally do not pass through it (Figure 9). (4) Atrophy of the cortex and of the hippocampus in VK-ADl 1 mice The analysis of the morphological aspect of the brain of VK-ADIl mice was conducted at 15 months of age and it revealed the presence of a marked atrophy of the cerebral cortex and of the hippocampus (Figure 10). (5) Reduction in cholin-acetyltransferase synthesis in the basal forebrain. The hystological aspect of the basal forebrain of the VK-ADIl mice revealed the presence of a progressive reduction in neurons that express the cholin- acetyltransferase enzyme (Figure 11, Figure 12), measured by means of the anti- cholin-acetyltransferase antiserum (Chemicon). (6) Hyperphosphorylation of the tau protein and presence of intracellular accumulation An increase in the expression of the phosphorylated tau protein determined using an antibody (mAb AT8, Innogenetics) directed against the Ser 202 and Ser 205 phosphorylated epitopes of tau (Greenberg and Davies, 1990) is observed. In particular, the protein is expressed in the soma of the neurons of the hippocampus (Figure 13 A) and of the cortex (Figure 13B5C), with a perinuclear distribution that is typical of tangles (Figure 13C). Moreover, the presence of numerous dystrophic neurites is shown (Figure 13C). Neither structures are present in control mice of the same age (Figure 13D). Additional experiments, which use the immunohistochemistry technique applied to electronic microscopy, have revealed the presence of protofibrils of tau protein similar to those that constitute filaments that form tangles in Alzheimer's patients (Figure 14). (7) Deposition of extracellular β amyloid The presence of extracellular aggregates of β-amyloid protein (Aβ) was revealed using the antibody against the Aβ 17-24 peptide (mAb 4G8, Signet), the Aβl-40 peptide (Sigma) and the Aβl-42 peptide (Biosource). The experiments were conducted using immunohistochemistry techniques. The results have revealed that, at 15 months of age, β-amyloid plaques are present in the cortex and in the hippocampus of VK-ADl 1 mice (Figure 15). These plaques occupy a significant part of the surface of the hippocampus with 13% of the surface with respect to a value of 0.1 % in control mice of the same age. (8) Behavioral deficit Behavioral analysis was performed on mice of between 2 and 8 months of age (n = 6 per experimental group). 2 tests were performed: (i) spatial orientation; (ii) object discrimination. (i) Spatial orientation (test of the radial labyrinth with 8 arms) a. learning phase: this consists of filling the same 4 arms with food for 14 days and allowing the mice to familiarize themselves with the labyrinth and learn the position of the food in the different arms of the labyrinth. The test is repeated twice a day and terminated when the mice have found all the food or when 25 entrances in the arms of the labyrinth were found. At 4 months of age, VK-ADI l mice make more mistakes during the initial learning phase (two-way RMANOVA test, p < 0.05), but the final level of learning does not differ from that of the control mice. At 8 months of age, the test differs significantly also in the final part of the learning curve (Figure 16). b. retention phase: this consists in suspending the test for 31 days and then in resuming it. Control mice retain the notions acquired during the learning phase, while VK-ADIl mice, both at 4 and at 8 months of age, are not able to remember what they learned previously. The learning curves between control mice and VK-ADl 1 mice were compared by means of two-way ANOVA test (Figure 16). c. phase of transferring the notions learned to a new situation: in this case, different arms from those used during the learning phase are filled with food. At both ages, VK-ADIl mice exhibit a behavioral deficit with respect to controls of the same age, which lasts even 5 days after the begining of the learning phase (p < 0.01, two way RMANOVA test) (Figure 16). (ii) Object discrimination test. The test consists in allowing mice to explore two white cubes, contained in a labyrinth, for 10 min. When the mice are removed from the labyrinth, and one of the cubes is coated with white and black checkered paper. After 1 hour from the end of the first trial, the mice were placed back into the labyrinth to explore the two cubes for 10 additional minutes. The VK-ADIl mice show a reduction in short term memory, not being able to distinguish differently colored cubes (Figures 17). In conclusion, VK-ADI l transgenic mice that express the anti-NGF neutralizing antibody recapitulate at the level of the Central Nervous System and of the peripheral innervation many of the typical alterations of neurodegenerative diseases, and in particular of Alzheimer's disease. Example 3. Reversal of the cholinergic phenotype, of tau hyperphosphorylation and of β-amyloid accumulation by NGF administration All experiments were conducted in mice starting from 4 months of age, when neurodegeneration is not so readily apparent. NGF was administered by intranasal injection (Frey et al, 1997) conducted every 2 days. NGF was administered as a 10 μM solution in phosphate buffer pH 7.4, injecting 3 μl per nostril every 2 min and alternating nostrils. The VK-ADI l control mice and non transgenic mice were treated only with phosphate buffer. For each administration, the infusion lasted 30 min. This non invasive method for administering NGF allows to avoid the use of the intraventricular injections to apply NGF directly to the cerebral tissue. To verify the administration of NGF, the mice were sacrificed 2 months from the begining of the treatment. The brain was removed and fixed in paraformaldehyde to conduct histological analyses. It was possible to observe that, in all injected animals, a similar phenotype to that of the non transgenic control mice was re-established, both with regard to the cholinergic deficit (Figure 18A), and the deposition of β-amyloid (Figure 18B) and of hyperphosphorylated tau (Figure 18C). Example 4 Reproductive ability of the VK-ADl 1 mice To evaluate the possibility that VK-ADl 1 mice, unlike ADl 1 mice, are able to yield as progeny new lines of mice which express not only an anti-NGF antibody, but which are transgenic also for other genes of interest for Alzheimer's disease or of other pathologies, it was decided to analyze the reproductive ability of both mice lines. Figure 19 shows how VK-ADIl mice, with respect to anti-NGF ADI l mice (derived from the crossing between VH-ADIl and VK-ADIl) are surprisingly able to reproduce far more easily and allow to have a homozygous line of VK-ADI l animals. This greater reproductive ability of VK-ADIl mice is important for 2 reasons (1). It is easy to obtain a line of mice with Alzheimer phenotype without having to re-cross the same mice with VH-ADI l mice (2). These VK-ADIl mice can be used for additional crossings with other knock-out mice, thereby obtaining new transgenic mice lines. In order to further validate the use of the VK-ADl 1 mice to produce new lines of transgenic mice, VH-ADI l mice and VK-ADIl mice were crossed with homozygous mice knockout for the p75NTR NGF receptor gene (mice p75NTR-/-; Lee et al., 1992). This receptor is involved in Alzheimer's disease since its reduced expression was observed in the basal forebrain of patients affected by Alzheimer's disease (Mufson et al., 2002) and since, in many cellular lines, it is an apoptosis mediator (Gentry et al., 2004). It was therefore of interest to obtain transgenic mice in which the neurodegenerative effect induced by the anti-NGF antibodies were studied in the genetic context of a knock-out mice for the p75NTR receptor. To obtain the mice that express an anti-NGF antibody and that are simultaneously homozygous knockouts for p75NTR, two different approaches were followed in parallel: (1) in the first case, mice ρ75NTR"A (Jackson Laboratories) were crossed respectively with VH-ADIl and VK-ADIl mice to obtain, respectively, the VH- ADl l-ρ75NTR~/" line and the VK-ADl 1- p75NTR"A- line. These new lines were then crossed between themselves, in order to obtain ADI l anti-NGF/p75NTR"Λ mice. This crossing failed to yield positive results, because it was impossible to obtain mice that express both chains of the anti-NGF antibody and that are simultaneously knockouts for p75NTR (Figure 20), because of the poor reproductive ability of the anti-NGF ADI l mice. (2) In the second approach, the crossing between VK-ADI l and p75NTR"A easily allows to obtain VK-AD l l/p75NTR7" mice (Figure 20) that allow to study the consequences of the knocking out of the receptor p75ko on the Alzheimer's phenotype shown by the VK-ADI l mice. This demonstrates that the VK-ADl 1 mice can easily be crossed with any other transgenic or knock-out mouse, thereby generating new experimental models. Example 5 Method for Diagnosing Alzheimer's Disease. The diagnosis method consists of a system based on the detection of antibodies directed against NGF protein or its TrKA receptor. The method is outlined in Figure 21. To perform this analysis, human recombinant NGF (Alomone labs, 5μg/ml) or the immunoadhesm TrkA-IgG (prepared in accordance with Pesavento et al., 2000, 5 μg/ml) were incubated in a 96 well ELISA plate (Nunc Maxisorp). 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