Serological study of CoronaVac vaccine and booster doses in Chile: immunogenicity and persistence of anti-SARS-CoV-2 spike antibodies

BACKGROUND

Chile was severely affected by COVID19 outbreaks but was also one of the first countries to start a nationwide program to vaccinate against the disease. Furthermore, Chile became one of the fastest countries to inoculate a high percentage of the target population and implemented homologous and heterologous booster schemes in late 2021 to prevent potential immunological waning. The aim of this study is to compare the immunogenicity and time course of the humoral response elicited by the CoronaVac vaccine in combination with homologous versus heterologous boosters.

METHODS

We compared the immunogenicity of two doses of CoronaVac and BNT162b2 vaccines and one homologous or heterologous booster through an ELISA assay directed against the ancestral spike protein of SARS-CoV-2. Sera were collected from individuals during the vaccination schedule and throughout the implementation of homologous and heterologous booster programs in Chile.

RESULTS

Our findings demonstrate that a two-dose vaccination scheme with CoronaVac induces lower levels of anti-SARS-CoV-2 spike antibodies than BNT162b2 in a broad age range (median age 42 years; interquartile range (IQR) 27-61). Furthermore, antibody production declines with time in individuals vaccinated with CoronaVac and less noticeably, with BNT162b2. Analysis of booster schemes revealed that individuals vaccinated with two doses of CoronaVac generate immunological memory against the SARS-CoV-2 ancestral strain, which can be re-activated with homologous or heterologous (BNT162b2 and ChAdOx1) boosters. Nevertheless, the magnitude of the antibody response with the heterologous booster regime was considerably higher (induction fold BNT162b2: 11.2x; ChAdoX1; 12.4x; CoronaVac: 6.0x) than the responses induced by the homologous scheme. Both homologous and heterologous boosters induced persistent humoral responses (median 122 days, IQR (108-133)), although heterologous boosters remained superior in activating a humoral response after 100 days.

CONCLUSIONS

Two doses of CoronaVac induces antibody titers against the SARS-CoV-2 ancestral strain which are lower in magnitude than those induced by the BNT162b2 vaccine. However, the response induced by CoronaVac can be greatly potentiated with a heterologous booster scheme with BNT162b2 or ChAdOx1 vaccines. Furthermore, the heterologous and homologous booster regimes induce a durable antibody response which does not show signs of decay 3 months after the booster dose.

Differential infectivity of two Trypanosoma cruzi strains in placental cells and tissue

Congenital Chagas disease, caused by Trypanosoma cruzi (T. cruzi), has become epidemiologically relevant. The probability of congenital transmission depends on the maternal and developing fetal/newborn immune responses, placental factors and importantly, the virulence of the parasite. It has been proposed, that different genotypes of T. cruzi and their associated pathogenicity, virulence and tissue tropism may play an important role in congenital infection. Since there is no laboratory or animal model that recapitulates the complexities of vertical transmission in humans, here we studied parasite infectivity in human placental explants (HPE) as well as in the human trophoblast-derived cell line BeWo of the Y(DTU II) and the VD (TcVI) T. cruzi strains; the latter was isolated from a human case of congenital infection. Our results show that the VD strain is more infective and pathogenic than the Y strain, as demonstrated by qPCR and cell counting as well as by histopathological analysis. The present study constitutes the first approach to study the relationship between parasite two parasite strains from different genotypes and the infection efficiency in human placenta.

The overexpression of TcAP1 endonuclease confers resistance to infective Trypanosoma cruzi trypomastigotes against oxidative DNA damage

Trypanosoma cruzi, the causative agent of Chagas' disease survives to DNA damage generated by ROS/RNS inside to their different hosts. In recent eukaryotes, oxidative DNA damage is repaired mainly by the Base Excision Repair (BER) pathway, being essential the apurinic/apyrimidinic endonuclease activity. Using a pTREX-gfp vector, the nucleotide sequence that encodes T. cruzi AP endonuclease TcAP1 (orthologue of human APE1) and a putative TcAP1 dominant negative (TcAP1DN), were transfectedand expressed in T. cruzi epimastigotes. TcAP1-GFP and TcAP1DN-GFP were expressed in those modified epimastigotes and found in the parasite nucleus. The endonucleases were purified under native conditions and the AP endonuclease activity was evaluated. While TcAP1 presents the expected AP endonuclease activity TcAP1DN does not. Moreover, TcAP1DN partially inhibits in vitro TcAP1 enzymatic activity. Transfected epimastigotes expressing TcAP1-GFP and TcAP1DN-GFP were differentiated to infective trypomastigotes. The infective parasites maintained both proteins (TcAP1-GFP and TcAP1DN-GFP) in the nucleus. The overexpression of TcAP1-GFP in epimastigotes and trypomastigotes increases the viability of both parasite forms when exposed to oxidative stress while the expression of TcAP1DN-GFP did not show any in vivo inhibitory effect, suggesting that endogenous TcAP1 constitutive expression overcomes the TcAP1DN inhibitory activity. Our results show that TcAP1 is important for trypomastigote survival under oxidative conditions similar to those found in infected mammalian cells, then increasing its permanence in the infected cells and the possibility of development of Chagas disease.

Characterization of Trypanosoma cruzi MutY DNA glycosylase ortholog and its role in oxidative stress response

Trypanosoma cruzi is a protozoan parasite and the causative agent of Chagas disease. Like most living organisms, it is susceptible to oxidative stress, and must adapt to distinct environments. Hence, DNA repair is essential for its survival and the persistence of infection. Therefore, we studied whether T. cruzi has a homolog counterpart of the MutY enzyme (TcMYH), important in the DNA Base Excision Repair (BER) mechanism. Analysis of T. cruzi genome database showed that this parasite has a putative MutY DNA glycosylase sequence. We performed heterologous complementation assays using this genomic sequence. TcMYH complemented the Escherichia coli MutY- strain, reducing the mutation rate to a level similar to wild type. In in vitro assays, TcMYH was able to remove an adenine that was opposite to 8-oxoguanine. We have also constructed a T. cruzi lineage that overexpresses MYH. Although in standard conditions this lineage has similar growth to control cells, the overexpressor is more sensitive to hydrogen peroxide and glucose oxidase than the control, probably due to accumulation of AP sites in its DNA. Localization experiments with GFP-fused TcMYH showed this enzyme is present in both nucleus and mitochondrion. QPCR and MtOX results reinforce the presence and function of TcMYH in these two organelles. Our data suggest T. cruzi has a functional MYH DNA glycosylase, which participates in nuclear and mitochondrial DNA Base Excision Repair.

Expression and the Peculiar Enzymatic Behavior of the Trypanosoma cruzi NTH1 DNA Glycosylase

Trypanosoma cruzi, the etiological agent of Chagas’ disease, presents three cellular forms (trypomastigotes, epimastigotes and amastigotes), all of which are submitted to oxidative species in its hosts. However, T. cruzi is able to resist oxidative stress suggesting a high efficiency of its DNA repair machinery.The Base Excision Repair (BER) pathway is one of the main DNA repair mechanisms in other eukaryotes and in T. cruzi as well. DNA glycosylases are enzymes involved in the recognition of oxidative DNA damage and in the removal of oxidized bases, constituting the first step of the BER pathway. Here, we describe the presence and activity of TcNTH1, a nuclear T. cruzi DNA glycosylase. Surprisingly, purified recombinant TcNTH1 does not remove the thymine glycol base, but catalyzes the cleavage of a probe showing an AP site. The same activity was found in epimastigote and trypomastigote homogenates suggesting that the BER pathway is not involved in thymine glycol DNA repair. TcNTH1 DNA-binding properties assayed in silico are in agreement with the absence of a thymine glycol removing function of that parasite enzyme. Over expression of TcNTH1 decrease parasite viability when transfected epimastigotes are submitted to a sustained production of H₂O₂.Therefore, TcNTH1 is the only known NTH1 orthologous unable to eliminate thymine glycol derivatives but that recognizes and cuts an AP site, most probably by a beta-elimination mechanism. We cannot discard that TcNTH1 presents DNA glycosylase activity on other DNA base lesions. Accordingly, a different DNA repair mechanism should be expected leading to eliminate thymine glycol from oxidized parasite DNA. Furthermore, TcNTH1 may play a role in the AP site recognition and processing.

DNA repair BER pathway inhibition increases cell death caused by oxidative DNA damage in Trypanosoma cruzi

Trypanosoma cruzi, a parasitic protozoan, is the etiological agent of Chagas disease, an endemic and neglected pathology in Latin America. It presents a life cycle that involves a hematophagous insect and man as well as domestic and wild mammals. The parasitic infection is not eliminated by the immune system of mammals; thus, the vertebrate host serves as a parasite reservoir. Additionally, chronic processes leading to dysfunction of the cardiac and digestive systems are observed. To establish a chronic infection some parasites should resist the oxidative damage to its DNA exerted by oxygen and nitrogen free radicals (ROS/RNS) generated in host cells. Till date there are no reports directly showing oxidative DNA damage and repair in T. cruzi. We establish that ROS/RNS generate nuclear and kinetoplastid DNA damage in T. cruzi that may be partially repaired by the parasite. Furthermore, we determined that both oxidative agents diminish T. cruzi cell viability. This effect is significantly augmented in parasites subsequently incubated with methoxyamine, a DNA base excision repair (BER) pathway inhibitor, strongly suggesting that the maintenance of T. cruzi viability is a consequence of DNA repair mechanisms.

TOR modulates GCN4-dependent expression of genes turned on by nitrogen limitation

In Saccharomyces cerevisiae, the rapamycin-sensitive TOR signaling pathway plays an essential role in up-regulating translation initiation and cell cycle progression in response to nutrient availability. One of the mechanisms by which TOR regulates cell proliferation is by excluding the GLN3 transcriptional activator from the nucleus and, in consequence, preventing its transcriptional activation therein. We examined the possibility that the TOR cascade could also control the transcriptional activity of Gcn4p, which is known to respond to amino acid availability. The results presented in this paper indicate that GCN4 plays a role in the rapamycin-sensitive signaling pathway, regulating the expression of genes involved in the utilization of poor nitrogen sources, a previously unrecognized role for Gcn4p, and that the TOR pathway controls GCN4 activity by regulating the translation of GCN4 mRNA. This constitutes an additional TOR-dependent mechanism which modulates the action of transcriptional activators.

Composition and antimicrobial activity of the essential oil of Peumus boldus leaves

The composition and the antimicrobial activity of the essential oil from the leaves of Peumus boldus is investigated. Analyses of the oil obtained by hydrodistillation were carried out by GC and GC-MS using columns of two different stationary phases. Fractionation of the essential oil by column chromatography on silica gel was performed to improve identification of some constituents. More than 90% of the total oil (46 components) was identified, major constituents being monoterpenes (90.5%), among which limonene (17.0%), p-cymene (13.6%), 1.8-cineole (11.8%), and beta-phellandrene (8.4%) reached the highest percentages. Determination of the minimal bactericidal or fungicidal concentration against several microorganisms showed interesting activities towards Streptococcus pyogenes, Micrococcus sp., and Candida sp.

Regulation of expression of GLT1, the gene encoding glutamate synthase in Saccharomyces cerevisiae

Saccharomyces cerevisiae glutamate synthase (GOGAT) is an oligomeric enzyme composed of three 199-kDa identical subunits encoded by GLT1. In this work, we analyzed GLT1 transcriptional regulation. GLT1-lacZ fusions were prepared and GLT1 expression was determined in a GDH1 wild-type strain and in a gdh1 mutant derivative grown in the presence of various nitrogen sources. Null mutants impaired in GCN4, GLN3, GAT1/NIL1, or UGA43/DAL80 were transformed with a GLT1-lacZ fusion to determine whether the above-mentioned transcriptional factors had a role in GLT1 expression. A collection of increasingly larger 5' deletion derivatives of the GLT1 promoter was constructed to identify DNA sequences that could be involved in GLT1 transcriptional regulation. The effect of the lack of GCN4, GLN3, or GAT1/NIL1 was also tested in the pertinent 5' deletion derivatives. Our results indicate that (i) GLT1 expression is negatively modulated by glutamate-mediated repression and positively regulated by Gln3p- and Gcn4p-dependent transcriptional activation; (ii) two cis-acting elements, a CGGN15CCG palindrome and an imperfect poly(dA-dT), are present and could play a role in GLT1 transcriptional activation; and (iii) GLT1 expression is moderately regulated by GCN4 under amino acid deprivation. Our results suggest that in a wild-type strain grown on ammonium, GOGAT constitutes an ancillary pathway for glutamate biosynthesis.

GDH3 encodes a glutamate dehydrogenase isozyme, a previously unrecognized route for glutamate biosynthesis in Saccharomyces cerevisiae

It has been considered that the yeast Saccharomyces cerevisiae, like many other microorganisms, synthesizes glutamate through the action of NADP+-glutamate dehydrogenase (NADP+-GDH), encoded by GDH1, or through the combined action of glutamine synthetase and glutamate synthase (GOGAT), encoded by GLN1 and GLT1, respectively. A double mutant of S. cerevisiae lacking NADP+-GDH and GOGAT activities was constructed. This strain was able to grow on ammonium as the sole nitrogen source and thus to synthesize glutamate through an alternative pathway. A computer search for similarities between the GDH1 nucleotide sequence and the complete yeast genome was carried out. In addition to identifying its cognate sequence at chromosome XIV, the search found that GDH1 showed high identity with a previously recognized open reading frame (GDH3) of chromosome I. Triple mutants impaired in GDH1, GLT1, and GDH3 were obtained. These were strict glutamate auxotrophs. Our results indicate that GDH3 plays a significant physiological role, providing glutamate when GDH1 and GLT1 are impaired. This is the first example of a microorganism possessing three pathways for glutamate biosynthesis.

Sequence of the GLT1 gene from Saccharomyces cerevisiae reveals the domain structure of yeast glutamate synthase

Glutamate synthase (GOGAT) and glutamine synthetase play a crucial role in ammonium assimilation and glutamate biosynthesis in the yeast Saccharomyces cerevisiae. The GOGAT enzyme has been purified and the GOGAT structural gene (GLT1) has been cloned, showing that this enzyme is a homotrimeric protein with a monomeric size of 199 kDa. We report the GLT1 nucleotide sequence and the amino acid sequence of its deduced protein product. Our results show that there is a high conservation with the corresponding genes of Escherichia coli, Medicago sativa (alfalfa) and Zea mais (maize). Binding domains for glutamine, cofactors (FMN and NADH) and the cysteine clusters (which comprise the iron-sulfur centres) were tentatively identified on the basis of sequence comparison with GOGAT sequences from E. coli, alfalfa and maize.

A NADP-glutamate dehydrogenase mutant of the petit-negative yeast Kluyveromyces lactis uses the glutamine synthetase-glutamate synthase pathway for glutamate biosynthesis

The activities of the enzymes involved in ammonium assimilation and glutamate biosynthesis were determined in wild-type and NADP-glutamate dehydrogenase (GDH) null mutant strains of Kluyveromyces lactis. The specific NADP-GDH activity from K. lactis was fivefold lower than that found in Saccharomyces cerevisiae. The glutamine synthetase (GS) and glutamate synthase (GOGAT) activities were similar to those reported in S. cerevisiae. The NADP-GDH null mutant was obtained by transforming the uraA strain MD2/1 with a linearized integrative yeast vector harbouring a 390 bp fragment of the NADP-GDH structural gene. This mutant grew as well as the parent strain on ammonium, but showed GS and GOGAT activities higher that those found in the wild-type strain, implying that the GS-GOGAT pathway could play a leading role in glutamate biosynthesis in K. lactis. Southern blotting analysis of K. lactis chromosomes separated by contour-clamped homogeneous electric field electrophoresis, indicated that the NADP-GDH structural gene is localized on chromosome VI.

Saccharomyces cerevisiae has a single glutamate synthase gene coding for a plant-like high-molecular-weight polypeptide

Purification of the glutamate synthase (GOGAT) enzyme from Saccharomyces cerevisiae showed that it is an oligomeric enzyme composed of three identical 199-kDa subunits. The GOGAT structural gene was isolated by screening a yeast genomic library with a yeast PCR probe. This probe was obtained by amplification with degenerate oligonucleotides designed from conserved regions of known GOGAT genes. The derived amino-terminal sequence of the GOGAT gene was confirmed by direct amino-terminal sequence analysis of the purified protein of 199 kDa. Northern (RNA) analysis allowed the identification of an mRNA of about 7 or 8 kb. An internal fragment of the GOGAT gene was used to obtain null GOGAT mutants completely devoid of GOGAT activity. The results show that S. cerevisiae has a single NADH-GOGAT enzyme, consisting of three 199-kDa monomers, that differs from the one found in prokaryotic microorganisms but is similar to those found in other eukaryotic organisms such as alfalfa.

Synthetic antigens as immunogens: Part II: Antibodies to synthetic T antigen

Antibody to the carbohydrate moiety of T antigen was developed. The synthetic antigen (Gal beta 1----3 GalNAc alpha 1----OC6H4N = N-BSA) was prepared by coupling the diazonium salt of the disaccharide derivative Gal beta 1----3 GalNAc alpha 1----OC6H4NH2 (o) with bovine serum albumin. Specificity of the antibody produced was examined with structurally related synthetic saccharides using the enzyme immunoassay technique. The presence of a glycosyl group at 0-6 of either the Gal or the GalNAc residue of the disaccharide Gal beta 1----3 GalNAc did not prevent binding of the antisera to the saccharide moiety. However, the antisera did not bind either the trisaccharide moiety NeuAc2----3 Gal beta 1----3 GalNAc alpha 1----OC6H4NO2 (o) or GlcNAc beta 1----3 Gal beta 1----3 GalNAc alpha OBn. These observations indicate that antibody approach to the antigen is to the 0-3 side of the terminal galactose in the disaccharide Gal beta 1----3 GalNAc. We have also observed that the antibody prefers Gal beta 1----3 GalNAc alpha 1----to Gal beta 1----3 GalNAc beta 1----disaccharide derivatives in its binding capacity. The antibody was found to bind natural T antigen present on neuraminidase-treated red blood cells and, by immunohistochemical analysis, it was found to bind to naturally occurring T antigen on breast tumor cells.

Synthetic antigens as immunogens: Part I. The combining site specificities of antibodies formed in rabbits to synthetic disaccharide alpha-L-Fuc-(1----3)-D-Gal

Antibody to chemically synthesized Fuc alpha 1----3 Gal-1----OC6H4N = N bovine serum albumin was developed. Specificity analysis using related synthetic saccharides was performed. The antisera were shown to be specific for both sugars in the disaccharide, to the 1----3 positional linkage and to the alpha anomeric configuration. Immunohistochemical staining was performed on benign disease and adenocarcinoma tissue of the colon. 5/8 of the benign colon polyp tissue and 4/6 of the colonic adenocarcinoma tissue showed strong granular cytoplasmic staining of the epithelia cells lining the ducts. None of the six normal colon tissues tested showed any reactivity. Immunohistochemical staining was also performed on tissue from benign disease and from carcinoma of the mammary gland. 2/5 of the tissue from benign disease of the breast and 3/6 of the tissue from breast carcinoma showed strong granular cytoplasmic staining of the ductal epithelial cells.

Immunohistochemical demonstration of prostate-specific antigen in metastases with the use of monoclonal antibody F5

With the use of a murine monoclonal antibody (F5), a panel of metastatic tumors was evaluated for the expression of prostate-specific antigen (PA) under immunoperoxidase staining procedures. Specimens studied included 25 of prostatic origin and 73 originating from nonprostatic primary sites. Regardless of the site of dissemination or the malignancy grade, all metastases from the prostate were antibody-reactive. In contrast, nonprostatic metastases were negative in each case, including those originating from other genitourinary neoplasms. Thus, PA expression as detected with monoclonal antibody F5 is a stable characteristic of disseminated prostatic tumors.

Reactivity of monoclonal antibody F36/22 with human ovarian adenocarcinomas

Monoclonal antibody F36/22 recognizes high-molecular-weight glycoprotein components associated with neoplastic development of the ovary. Indirect immunoperoxidase staining techniques were performed on a panel of nonmalignant ovarian tissues, primary ovarian tumors, exfoliated ascitic tumor cells, and metastatic lesions. Normal ovarian tissue components (n = 20) failed to exhibit detectable levels of antigen, whereas benign ovarian tissues show a low incidence of immunostaining (three of 26) restricted to some ductal elements. One hundred % (19 of 19) of the immunopositive primary malignant tumors were histologically classified as adenocarcinomas. Each of the predominant adenocarcinoma histotypes consistently showed expression of the antigen with 30 to 100% of the tumor cells scored as immunopositive. Ascitic tumor cells obtained from all of the ovarian adenocarcinoma patients examined (47 of 47) displayed immunopositive reactions, whereas normal mesothelial cells in these specimens exhibited undetectable staining. In addition, ovarian adenocarcinoma metastases (12 of 12) exhibited very intense immunoreaction products. No detectable antigen was expressed by nonadenocarcinoma ovarian tumor cells.

Hybridoma antibody to breast cancer immune complexes

Hybridoma clones were established by fusing spleen cells from mice immunized with purified breast cancer-related immune complexes to drug-resistant nonproducing myelomas. Hybridoma cultures were evaluated for antibody production using immunofluorescence, radioimmunoassay and immunoperoxidase techniques. One antibody demonstrated strong reactivity against breast tumor cells (BT-20) in culture and also was found to bind ductal epithelial cells within sections of human mammary tissue. Antigen was detected within the soluble fraction of breast tumors with molecular weight greater than 500 K. The possible relationship between antigen detected in breast tumor cells and in immune-complexed form is discussed.

Expression of prostatic acid phosphatase in human prostate cancer

By a specific immunochemical measurement, the activity of prostatic acid phosphatase (PAP) in prostate cancer was found to be about 25%, on average, based on micrograms DNA or per cell, of that in normal prostate or benign prostatic hypertrophy (BPH). The reduction of PAP in prostate cancer was further revealed by a decrease in PAP protein. The 125I-labeled anti-PAP IgG specifically bound to nascent peptides on PAP-synthesizing polysomes showed no qualitative differences among cancerous prostate, normal prostate and BPH. However, the quantitative binding of 125I-labeled anti-PAP IgG to polysomes of cancerous prostate was half that of normal prostate of BPH. These data suggest that a significant amount of PAP and its synthesizing polysomes was reduced in prostate cancer as a result of PAP gene suppression.

Prostate antigen: a marker for human prostate epithelial cells

Specificity of a previously reported prostate antigen (PA) was assessed by several immunologic procedures. This antigen, restricted in distribution to the prostate gland, was detected within ductal epithelial cells. Continuous established cell lines LNCaP and PC-3 of malignant prostate origin retained the expression of PA. Tumor cells released the antigen in vitro into the culture fluid and also in vivo into the circulation of nude mice preinoculated with LNCaP cells. Prostate cells in culture also specifically accreted immunoglobulin fragments of PA antiserum.

Quantitation of prostate-specific antigen in serum by a sensitive enzyme immunoassay

A sensitive sandwich-type enzyme immunoassay has been developed for quantitation of a human prostate-specific antigen (PA). With this method, PA at a concentration as low as 0.10 ng/ml can be detected. The assay was reproducible as within and between assays yielded a coefficient of variation of 5.7% and 4.6%, respectively. Only human prostate tissues (n = 31) were shown to contain PA. No PA was detected in other human normal or tumor tissues (n = 13). PA was not detectable in sera from normal females (n = 17) or female cancer patients (n = 25). A mean +/- S.D. of 0.47 +/- 0.661 ng/ml (ranging from less than 0.10 to 2.6) ws obtained from a group of 51 normal males. Sera from male patients with nonprostatic cancer contained a similar range of PA as that of normal males. Patients with prostate cancer (371 of 442) and benign prostatic hypertrophy (13 of 19) were shown to have elevated levels of circulating PA. Although no quantitative difference in PA levels was found between the benign prostatic hypertrophy group and Stage A of prostatic cancer, patients with Stages C and D prostatic cancer exhibited significantly elevated levels of PA qualitatively and quantitatively. These results therefore indicate that PA is a histiotypic product of the prostate and may be of use as an adjunctive tool in diagnostic procedures of prostate cancer.

Isoenzymes of human prostate acid phosphatase

The isoenzymes of human prostatic acid phosphatase have been studied by an isoelectric focusing technique. Purified acid phosphatase from malignant prostates contained eight isoenzymes with pI 4.4--5.3. The sera from patients with prostate cancer were shown to have similar acid phosphatase isoenzyme patterns at pI 4.0--5.5; as the serum enzyme activities increased, the pI of isoenzymes shifted to more acidic pH. These isoenzyme patterns of sera from patients with prostate cancer were different from those of patients with Gaucher's disease or from acid phosphatase of human erythrocytes, both of which exhibited only one enzyme band around pI 5.0 and 6.0, respectively. Treatment of serum sample of prostate cancer with neuraminidase did not result in a single enzyme band but alter the pI of isoenzymes, which shifted to a higher pH region. The significance of acid phosphatase activities and its isoenzyme patterns in prostate cancer merits further investigation.

Enzyme markers in human prostatic carcinoma

In an effort to develop a sensitive and specific method for detecting human prostatic cancer at early stages, we have studied the isoenzyme patterns of acid phosphatase in patients' sera as well as in benign hypertrophic and cancerous prostatic tissues using isoelectric focusing techniques. At least eight acid phosphatase isoenzymes at pI 4.1-5.5 could be observed. The sera with highly elevated acid phosphatase activity generally contained more isoenzymes with pI values of 4.5-5.0. The purified acid phosphatase isolated from benign hypertrophic and malignant prostatic tissues showed no qualitative difference in isoenzyme patterns although quantitative variations were observed. Malignant tissue contained more isoenzymes with pI values of 4.5-4.8. Patients' sera were found to contain isoenzymes of prostate origin. We have also investigated serum ribonuclease (RNase) activity in patients with prostatic cancer. The serum RNase activity of patients was significantly elevated. No significant correlation was observed between serum acid phosphatase and RNase activity. In some instances, where acid phosphatase activity was in the normal range, RNase activity was elevated. These data suggest that simultaneous measurements of RNase and acid phosphatase activities may be of value in the diagnosis of prostatic cancer. The purified RNase has been isolated from human prostatic tissue and its immunologic properties are being studied.