Efficient eukaryotic expression of fluorescent scFv fusion proteins directed against CD antigens for FACS applications

Two sets of expression vectors were constructed that permitted the efficient expression of single-chain Fv fragments (scFvs) fused N-terminally to an enhanced mutant of the green fluorescent protein GFP+ or the red fluorescent protein DsRed in insect and mammalian cells. The vectors allowed rapid cloning of scFv fragments and secretion of the fusion proteins in a native conformation. Fluorescent scFv fusion proteins directed against a series of cluster of differentiation (CD) antigens were efficiently secreted by transiently transfected mammalian cells and insect cells infected with baculoviral expression constructs. Yields of the secreted proteins varied from 100 microg/l to 3 mg/l. The purified proteins were functionally active in flow cytometry, immunofluorescent microscopy, and competition binding experiments performed to delineate the epitopes recognized by different monoclonal antibodies against the same polypeptide. The use of two different scFv fragments fused with red and green fluorescent proteins and reacting with T- and B-cell lineage markers (CD7 and CD19), respectively, allowed a simplified quantitation of both subsets in two-color flow cytometry experiments with mixed populations of T- and B-lymphoid cells. Due to the lack of Fc domains in the scFv proteins, the fluorescent fusion proteins showed more than 20-fold reduced background fluorescence compared with whole antibodies of the same specificity in experiments with effector cells expressing the high affinity FcgammaRI receptor CD64. Thus, for a number of analytical applications, fluorescent scFv fusion proteins offer advantages over the use of complete primary antibodies and chemically labeled fluorescent secondary antibodies.     

Human leukocyte antigen class II alleles influence levels of antibodies to the Plasmodium falciparum asexual-stage apical membrane antigen 1 but not to merozoite surface antigen 2 and merozoite surface protein 1

The apical membrane antigen 1 (AMA1), merozoite surface antigen 2 (MSA2), and merozoite surface protein 1 (MSP1) are asexual-stage proteins currently being evaluated for inclusion in a vaccine for Plasmodium falciparum. Accordingly, it is important to understand factors that control antibody responses to these antigens. Antibody levels in plasma from residents of Etoa, Cameroon, between the ages of 5 and 70 years, were determined using recombinant AMA1, MSA2, and the N-terminal region of MSP1 (MSP1-190L). In addition, antibody responses to four variants of the C-terminal region of MSP1 (MSP1(19)) were assessed. Results showed that all individuals produced antibodies to AMA1, MSA2, and MSP1-190L; however, a proportion of individuals never produced antibodies to the MSP1(19) variants, although the percentage of nonresponders decreased with age. The influence of age and human leukocyte antigen (HLA)-DRB1/DQB1 alleles on antibody levels was evaluated using two-way analysis of variance. Age was correlated with levels of antibodies to AMA1 and MSP1(19) but not with levels of antibodies to MSA2 and MSP1-190L. No association was found between a single HLA allele and levels of antibodies to MSA2, MSP1-190L, or any of the MSP1(19) variants. However, individuals positive for DRB1*1201 had higher levels of antibodies to the variant of recombinant AMA1 tested than did individuals of all other HLA types. Since the effect was seen across all age groups, HLA influenced the level but not the rate of antibody acquisition. This association for AMA1, combined with the previously reported association between HLA class II alleles and levels of antibodies to rhoptry-associated protein 1 (RAP1) and RAP2, indicates that HLA influences the levels of antibodies to three of the five vaccine candidate antigens that we have evaluated.     

Vaccination of monkeys with recombinant Plasmodium falciparum apical membrane antigen 1 confers protection against blood-stage malaria

A major challenge facing malaria vaccine development programs is identifying efficacious combinations of antigens. To date, merozoite surface protein 1 (MSP1) is regarded as the leading asexual vaccine candidate. Apical membrane antigen 1 (AMA1) has been identified as another leading candidate for an asexual malaria vaccine, but without any direct in vivo evidence that a recombinant form of Plasmodium falciparum AMA1 would have efficacy. We evaluated the efficacy of a form of P. falciparum AMA1, produced in Pichia pastoris, by vaccinating Aotus vociferans monkeys and then challenging them with P. falciparum parasites. Significant protection from this otherwise lethal challenge with P. falciparum was observed. Five of six animals had delayed patency; two of these remained subpatent for the course of the infection, and two controlled parasite growth at <0.75% of red blood cells parasitized. The protection induced by AMA1 was superior to that obtained with a form of MSP1 used in the same trial. The protection induced by a combination vaccine of AMA1 and MSP1 was not superior to the protection obtained with AMA1 alone, although the immunity generated appeared to operate against both vaccine components.     

Efficacy of vaccines containing rhoptry-associated proteins RAP1 and RAP2 of Plasmodium falciparum in Saimiri boliviensis monkeys

A vaccine trial was conducted with rhoptry-associated proteins 1 and 2 (RAP1 and RAP2) of Plasmodium falciparum in Saimiri boliviensis monkeys to compare the ability of parasite-derived (PfRAP1 and 2) and recombinant proteins (rRAP1 and 2) to induce protective immune responses and to find adjuvants suitable for use in humans. Eight groups of 6 monkeys each were immunized with parasite-derived or recombinant RAP1 and 2 with Freund's complete adjuvant (FCA) followed by Freund's incomplete adjuvant (FIA), Montanide ISA720 adjuvant, or CRL1005 adjuvant. Recombinant RAP1 and RAP2 were also administered separately, with Montanide ISA720. After 3 immunizations, monkeys were challenged by iv inoculation of 50,000 parasites of the Uganda Palo Alto strain of P. falciparum. Of the animals vaccinated using FCA/FIA, 1 of 6 control monkeys, 3 of 6 immunized with PfRAP1 and 2, and 2 of 6 with rRAP1 and 2 did not require drug treatment. Of the monkeys vaccinated with Montanide ISA720 adjuvant, 0 of the 6 control monkeys, 2 of 6 immunized with RAP1 and 2, 1 of 6 immunized with rRAP1, and 4 of 6 immunized with RAP2 did not require drug treatment. Two of 6 monkeys immunized with PfRAP1 and 2 with CRL1005 did not require treatment. All groups receiving RAP1, RAP2, or both had a significant decrease in initial parasite multiplication rates and there was a significant negative correlation between anti-RAP2 antibody and multiplication rates. Animals were rechallenged with the homologous parasite 126 days after the first challenge. Of the monkeys that did not require drug treatment after the first challenge, none developed detectable parasitemia following rechallenge.     

疟疾病人血样中特异性乳酸脱氢酶检测的研究

应用直接电泳法和多克隆抗体搏捉法检测恶性疟和间日疟疾病人血样各４０份，正常对照血样２０份中恶性疟原虫特异性乳酸脱氢酶（ＬＤＨ－ｐ）。结果表明，两种方法检测恶性疟病人血样的阳性率分别为９０％和９５％；而间日疟和正常人血样中皆未检出ＬＤＨ－ｐ的活性。结果还表明，蛋白酶抑制剂可有效地保护ＬＤＨ－ｐ，而反复冻融则可使ＬＤＨ－ｐ受到破坏，检出率降低。应用直接电泳法和多克隆抗体捕捉法，在蛋白酶抑制剂存在的条件     

隐孢子虫对小鼠树突状细胞功能的影响

目的探索隐孢子虫对小鼠树突状细胞功能的影响。方法采用磁珠分离小鼠的树突状细胞，将树突状细胞与活体隐孢子虫一起培养，用流式细胞仪观察树突状细胞表面标记的变化，并进一步观察树突状细胞产生各种细胞因子的情况。结果活体隐孢子虫能直接感染小鼠树突状细胞，并使其细胞表面高表达CD40、CD80、CD86，同时产生大量的IL-6、IL-12及TNF-α等细胞因子。结论树突状细胞参与了隐孢子虫宿主免疫过程，并在宿主对虫体的免疫反应中起重要作用。     

Phase II study of mifepristone (RU486) in refractory ovarian cancer

OBJECTIVE: A phase II study of Mifepristone (RU486) was conducted in patients with ovarian cancer whose tumors were resistant to cisplatin and paclitaxel, alone or in combination. Patients and METHODS: Forty-four patients were accrued into this study. All had ovarian cancer that had become resistant to cisplatin and paclitaxel. Patients received Mifepristone 200 mg orally on a daily basis. Patients were followed by tumor size or CA-125 levels when there was no measurable disease. A dose reduction of Mifepristone was to occur in the event of grade 3/4 hematologic, GI, or liver toxicity, creatinine >2.5%, and grade 4 peripheral neuropathy. RESULTS: Thirty-four patients were evaluable for response. Nine (26.5%) of these patients had a response to Mifepristone. Three(9%) patients had a complete response, and six (17.5%), a partial response. The response of one patient in each group was measured by CA-125 levels while the remainder had measurable disease. The response lasted 1 to 4 months in all but one patient. One patient continues to respond after more than 3 years. The major toxic effect was a rash and this was the major reason patients were removed from the study. CONCLUSION: Mifepristone has activity against ovarian cancer resistant to cisplatin and paclitaxel. The drug is well tolerated. Further studies need to be performed when this drug becomes more widely available in the United States.     

Ribosomal DNA sequence markers differentiate two species of the Anopheles maculatus (Diptera: Culicidae) complex in the Philippines

The Anopheles maculatus Theobald complex includes important vectors of malaria. Based on chromosomal and morphological evidence, two species in this complex occur in the Philippines. Because separation of these species, An. dispar Rattanarithikul & Harbach and An. greeni Rattanarithikul & Harbach, is problematic due to the difficulty or unreliability of the identification methods currently available, we sought a molecular technique for identifying these two species. We sequenced two regions of nuclear ribosomal DNA; the second internal transcribed spacer (ITS2) and the third domain (D3) of the 28S gene, from An. maculatus sensu lato (s.l.) collected throughout the Philippines. Two sequence groups were identified that corresponded morphologically to An. dispar and An. greeni. Four percent of the 318-320 bp ITS2 and 2.5% of the 367 bp D3 differed between the two species. No evidence of intraspecific variation in sequences was found. From the sequence data, we developed a more reliable and easier method for identifying An. dispar and An. greeni, based on a HaeII restriction fragment-length polymorphism in a polymerase chain reaction amplified fragment of ITS2. This method will facilitate future vector studies, which will be necessary, as previous data collected on An. maculatus s.l. in the Philippines is unreliable given the multispecies nature of this taxon.