Selective activation of IFNγ-ipilimumab enhances the therapeutic effect and safety of ipilimumab

INTRODUCTION

Immune checkpoint inhibitor therapy is a highly promising strategy for clinical treatment of cancer. Among these inhibitors, ipilimumab stands out for its ability to induce cytotoxic T cell proliferation and activation by binding to CTLA-4. However, ipilimumab also gives rise to systemic immune-related adverse effects and tumor immune evasion, limiting its effectiveness.

OBJECTIVES

We developed IFNγ-ipilimumab and confirmed that the addition of INF-γ does not alter the fundamental properties of ipilimumab.

RESULTS

IFNγ-ipilimumab can be activated by matrix metalloproteinases, thereby promoting the IFNγ signaling pathway and enhancing the cytotoxicity of T cells. In vivo studies demonstrated that IFNγ-ipilimumab enhances the therapeutic effect of ipilimumab against colorectal cancer by increasing CD8+ and CD4+ lymphocyte infiltration into the tumor area and inducing MHC-I expression in tumor cells. Mice treated with IFNγ-ipilimumab showed higher survival rates and body weight, as well as lower CD4+ and CD8+ lymphocyte activation rates in the blood and reduced organ damage.

CONCLUSION

IFNγ-ipilimumab improved the effectiveness of ipilimumab while reducing its side effects. It is likely that future immunotherapies would rely on such antibodies to activate local cancer cells or immune cells, thereby increasing the therapeutic effectiveness of cancer treatments and ensuring their safety.

A lesion-selective albumin-CTLA4Ig as a safe and effective treatment for collagen-induced arthritis

BACKGROUND

CTLA4Ig is a dimeric fusion protein of the extracellular domain of cytotoxic T-lymphocyte protein 4 (CTLA4) and an Fc (Ig) fragment of human IgG₁ that is approved for treating rheumatoid arthritis. However, CTLA4Ig may induce adverse effects. Developing a lesion-selective variant of CTLA4Ig may improve safety while maintaining the efficacy of the treatment.

METHODS

We linked albumin to the N-terminus of CTLA4Ig (termed Alb-CTLA4Ig) via a substrate sequence of matrix metalloproteinase (MMP). The binding activities and the biological activities of Alb-CTLA4Ig before and after MMP digestion were analyzed by a cell-based ELISA and an in vitro Jurkat T cell activation assay. The efficacy and safety of Alb-CTLA4Ig in treating joint inflammation were tested in mouse collagen-induced arthritis.

RESULTS

Alb-CTLA4Ig is stable and inactive under physiological conditions but can be fully activated by MMPs. The binding activity of nondigested Alb-CTLA4Ig was at least 10,000-fold weaker than that of MMP-digested Alb-CTLA4Ig. Nondigested Alb-CTLA4Ig was unable to inhibit Jurkat T cell activation, whereas MMP-digested Alb-CTLA4Ig was as potent as conventional CTLA4Ig in inhibiting the T cells. Alb-CTLA4Ig was converted to CTLA4Ig in the inflamed joints to treat mouse collagen-induced arthritis, showing similar efficacy to that of conventional CTLA4Ig. In contrast to conventional CTLA4Ig, Alb-CTLA4Ig did not inhibit the antimicrobial responses in the spleens of the treated mice.

CONCLUSIONS

Our study indicates that Alb-CTLA4Ig can be activated by MMPs to suppress tissue inflammation in situ. Thus, Alb-CTLA4Ig is a safe and effective treatment for collagen-induced arthritis in mice.

Structural insights into Nirmatrelvir (PF-07321332)-3C-like SARS-CoV-2 protease complexation: a ligand Gaussian accelerated molecular dynamics study

Coronavirus 3C-like protease (3CLpro) is found in SARS-CoV-2 virus, which causes COVID-19. 3CLpro controls virus replication and is a major target for target-based antiviral discovery. As reported by Pfizer, Nirmatrelvir (PF-07321332) is a competitive protein inhibitor and a clinical candidate for orally delivered medication. However, the binding mechanisms between Nirmatrelvir and 3CLpro complex structures remain unknown. This study incorporated ligand Gaussian accelerated molecular dynamics, the one-dimensional and two-dimensional potential of mean force, normal molecular dynamics, and Kramers' rate theory to determine the binding and dissociation rate constants (k_off and k_on) associated with the binding of the 3CLpro protein to the Nirmatrelvir inhibitor. The proposed approach addresses the challenges in designing small-molecule antiviral drugs.

A universal in silico V(D)J recombination strategy for developing humanized monoclonal antibodies

BACKGROUND

Humanization of mouse monoclonal antibodies (mAbs) is crucial for reducing their immunogenicity in humans. However, humanized mAbs often lose their binding affinities. Therefore, an in silico humanization method that can prevent the loss of the binding affinity of mAbs is needed.

METHODS

We developed an in silico V(D)J recombination platform in which we used V(D)J human germline gene sequences to design five humanized candidates of anti-tumor necrosis factor (TNF)-α mAbs (C1-C5) by using different human germline templates. The candidates were subjected to molecular dynamics simulation. In addition, the structural similarities of their complementarity-determining regions (CDRs) to those of original mouse mAbs were estimated to derive the weighted interatomic root mean squared deviation (wRMSDi) value. Subsequently, the correlation of the derived wRMSDi value with the half maximal effective concentration (EC50) and the binding affinity (KD) of the humanized anti-TNF-α candidates was examined. To confirm whether our in silico estimation method can be used for other humanized mAbs, we tested our method using the anti-epidermal growth factor receptor (EGFR) a4.6.1, anti-glypican-3 (GPC3) YP9.1 and anti-α4β1 integrin HP1/2L mAbs.

RESULTS

The R2 value for the correlation between the wRMSDi and log(EC50) of the recombinant Remicade and those of the humanized anti-TNF-α candidates was 0.901, and the R2 value for the correlation between wRMSDi and log(KD) was 0.9921. The results indicated that our in silico V(D)J recombination platform could predict the binding affinity of humanized candidates and successfully identify the high-affinity humanized anti-TNF-α antibody (Ab) C1 with a binding affinity similar to that of the parental chimeric mAb (5.13 × 10-10). For the anti-EGFR a4.6.1, anti-GPC3 YP9.1, and anti-α4β1 integrin HP1/2L mAbs, the wRMSDi and log(EC50) exhibited strong correlations (R2 = 0.9908, 0.9999, and 0.8907, respectively).

CONCLUSIONS

Our in silico V(D)J recombination platform can facilitate the development of humanized mAbs with low immunogenicity and high binding affinities. This platform can directly transform numerous mAbs with therapeutic potential to humanized or even human therapeutic Abs for clinical use.

Selective activation of pro-anti-IL-1β antibody enhances specificity for autoinflammatory disorder therapy

Canakinumab is a fully human monoclonal antibody that specifically neutralizes human interleukin (IL)-1β and has been approved by the US Food and Drug Administration for treating different types of autoinflammatory disorders such as cryopyrin-associated periodic syndrome, tumor necrosis factor receptor-associated periodic syndrome and systemic juvenile idiopathic arthritis. However, long-term systemic neutralization of IL-1β by Canakinumab may cause severe adverse events such as serious upper respiratory tract infections and inflammation, thereby decreasing the quality of life of patients. Here, we used an IgG1 hinge as an Ab lock to cover the IL-1β-binding site of Canakinumab by linking with matrix metalloprotease 9 (MMP-9) substrate to generate pro-Canakinumab that can be specifically activated in the inflamed regions in autoinflammatory diseases to enhance the selectivity and safety of treatment. The Ab lock significantly inhibited the IL-1β-binding by 68-fold compared with Canakinumab, and MMP-9 completely restored the IL-1β neutralizing ability of pro-Canakinumab within 60 min and blocked IL-1β-downstream signaling and IL-1β-regulated genes (i.e., IL-6). It is expected that MMP-9 cleavable and efficient Ab lock will be able to significantly enhance the selective reaction of Canakinumab at the disease site and reduce the on-target toxicities of Canakinumab during systemic circulation, thereby showing potential for development to improve the safety and quality of life of patients with autoinflammatory disorders in the future.

Correction: Development of a structure-based computational simulation to optimize the blocking efficacy of pro-antibodies

Correction for ‘Development of a structure-based computational simulation to optimize the blocking efficacy of pro-antibodies’ by Bo-Cheng Huang et al., Chem. Sci., 2021, DOI: 10.1039/D1SC01748A.

Development of a structure-based computational simulation to optimize the blocking efficacy of pro-antibodies

The on-target toxicity of monoclonal antibodies (Abs) is mainly due to the fact that Abs cannot distinguish target antigens (Ags) expressed in disease regions from those in normal tissues during systemic administration. In order to overcome this issue, we “copied” an autologous Ab hinge as an “Ab lock” and “pasted” it on the binding site of the Ab by connecting a protease substrate and linker in between to generate a pro-Ab, which can be specifically activated in the disease region to enhance Ab selectivity and reduce side effects. Previously, we reported that 70% of pro-Abs can achieve more than 100-fold blocking ability compared to the parental Abs. However, 30% of pro-Abs do not have such efficient blocking ability. This is because the same Ab lock linker cannot be applied to every Ab due to the differences in the complementarity-determining region (CDR) loops. Here we designed a method which uses structure-based computational simulation (MSCS) to optimize the blocking ability of the Ab lock for all Ab drugs. MSCS can precisely adjust the amino acid composition of the linker between the Ab lock and Ab drug with the assistance of molecular simulation. We selected αPD-1, αIL-1β, αCTLA-4 and αTNFα Ab as models and attached the Ab lock with various linkers (L1 to L7) to form pro-Abs by MSCS, respectively. The resulting cover rates of the Ab lock with various linkers compared to the Ab drug were in the range 28.33–42.33%. The recombinant pro-Abs were generated by MSCS prediction in order to verify the application of molecular simulation for pro-Ab development. The binding kinetics effective concentrations (EC-50) for αPD-1 (200-250-fold), αIL-1β (152-186-fold), αCTLA-4 (68-150-fold) and αTNFα Ab (20-123-fold) were presented as the blocking ability of pro-Ab compared to the Ab drug. Further, there was a positive correlation between cover rate and blocking ability of all pro-Ab candidates. The results suggested that MSCS was able to predict the Ab lock linker most suitable for application to αPD-1, αIL-1β, αCTLA-4 and αTNFα Ab to form pro-Abs efficiently. The success of MSCS in optimizing the pro-Ab can aid the development of next-generation pro-Ab drugs to significantly improve Ab-based therapies and thus patients' quality of life.

The pro-Ab blocks the Ag binding site using an Ab lock. We designed a method which uses structure-based computational simulation (MSCS) to predict the cover rate of Ab locks with various linkers and select the suitable linker for each Ab.

Enhancement of tumor tropism of mPEGylated nanoparticles by anti-mPEG bispecific antibody for ovarian cancer therapy

Ovarian cancer is highly metastatic, with a high frequency of relapse, and is the most fatal gynecologic malignancy in women worldwide. It is important to elevate the drug susceptibility and cytotoxicity of ovarian cancer cells, thereby eliminating resident cancer cells for more effective therapeutic efficacy. Here, we developed a bispecific antibody (BsAb; mPEG × HER2) that can easily provide HER2⁺ tumor tropism to mPEGylated liposomal doxorubicin (PLD) and further increase the drug accumulation in cancer cells via receptor-mediated endocytosis, and improve the cytotoxicity and therapeutic efficacy of HER2⁺ ovarian tumors. The mPEG × HER2 can simultaneously bind to mPEG molecules on the surface of PLD and HER2 antigen on the surface of ovarian cancer cells. Simply mixing the mPEG × HER2 with PLD was able to confer HER2 specificity of PLD to HER2⁺ ovarian cancer cells and efficiently trigger endocytosis and enhance cytotoxicity by 5.4-fold as compared to non-targeted PLD. mPEG × HER2-modified PLD was able to significantly increase the targeting and accumulation of HER2⁺ ovarian tumor by 220% as compared with non-targeted PLD. It could also significantly improve the anti-tumor activity of PLD (P < 0.05) with minimal obvious toxicity in a tumor-bearing mouse model. We believe that the mPEG × HER2 can significantly improve the therapeutic efficacy, potentially reduce the relapse freqency and thereby achieve good prognosis in ovarian cancer patients.

Double attack strategy for leukemia using a pre-targeting bispecific antibody (CD20 Ab-mPEG scFv) and actively attracting PEGylated liposomal doxorubicin to enhance anti-tumor activity

BACKGROUND

Tumor-targeted nanoparticles hold great promise as new tools for therapy of liquid cancers. Furthermore, the therapeutic efficacy of nanoparticles can be improved by enhancing the cancer cellular internalization.

METHODS

In this study, we developed a humanized bispecific antibody (BsAbs: CD20 Ab-mPEG scFv) which retains the clinical anti-CD20 whole antibody (Ofatumumab) and is fused with an anti-mPEG single chain antibody (scFv) that can target the systemic liquid tumor cells. This combination achieves the therapeutic function and simultaneously "grabs" Lipo-Dox® (PEGylated liposomal doxorubicin, PLD) to enhance the cellular internalization and anticancer activity of PLD.

RESULTS

We successfully constructed the CD20 Ab-mPEG scFv and proved that CD20 Ab-mPEG scFv can target CD20-expressing Raji cells and simultaneously grab PEGylated liposomal DiD increasing the internalization ability up to 60% in 24 h. We further showed that the combination of CD20 Ab-mPEG scFv and PLD successfully led to a ninefold increase in tumor cytotoxicity (LC₅₀: 0.38 nM) compared to the CD20 Ab-DNS scFv and PLD (lC₅₀: 3.45 nM) in vitro. Importantly, a combination of CD20 Ab-mPEG scFv and PLD had greater anti-liquid tumor efficacy (P = 0.0005) in Raji-bearing mice than CD20 Ab-DNS scFv and PLD.

CONCLUSION

Our results indicate that this "double-attack" strategy using CD20 Ab-mPEG scFv and PLD can retain the tumor targeting (first attack) and confer PLD tumor-selectivity (second attack) to enhance PLD internalization and improve therapeutic efficacy in liquid tumors.

[Analysis of drug - resistant gene polymorphisms in Plasmodium falciparum imported from Equatorial Guinea to Shandong Province in 2015 and 2016]

OBJECTIVE

To investigate the drug-resistant gene polymorphisms in Plasmodium falciparum imported from Equatorial Guinea to Shandong Province.

METHODS

From 2015 to 2016, blood samples were collected from imported P. falciparum malaria patients returning from Equatorial Guinea to Shandong Province, and genome DNA of the malaria parasite was extracted. The drug-resistant Pfcrt, Pfmdr1, Pfdhfr, Pfdhps, and K13 genes of P. falciparum were amplified using a PCR assay, followed by DNA sequencing, and the sequences were aligned.

RESULTS

The target fragments of all 5 drug-resistant genes of P. falciparum were successfully amplified and sequenced. There were 72.8%, 18.6%, and 8.6% of P. falciparum parasites carrying the wild-, mutant-, and mixed-type Pfcrt gene, respectively, and all mutant haplotypes were CVIET (the underline indicates the mutation site). There were 20.0%, 61.4% and 18.6% of P. falciparum parasites carrying the wild-, mutant-, and mixed-type Pfmdr1 gene, respectively, and the mutant haplotypes mainly included YF and NF (the underlines indicate the mutation sites). There were 1.4%, 98.6%, and 0 of P. falciparum parasites carrying the wild-, mutant-, and mixed-type Pfdhfr gene, respectively, and AIRNI was the predominant mutant haplotype (the underline indicates the mutation site). There were 1.4%, 94.3%, and 4.3% of P. falciparum parasites carrying the wild-, mutant-, and mixed-type Pfdhps gene, respectively, and SGKAA was the predominant mutant haplotype (the underline indicates the mutation site). The complete drug-resistant IRNGE genotype consisted of 8.6% of the Pfdhfr and Pfdhps genes, and the K13 gene A578S mutation occurred in 1.4% of the parasite samples.

CONCLUSIONS

There are mutations in the Pfcrt, Pfmdr1, Pfdhfr, Pfdhps, and K13 genes of P. falciparum imported from Equatorial Guinea to Shandong Province, with a low frequency in the Pfcrt gene mutation and a high frequency in the Pfmdr1, Pfdhfr, and Pfdhps gene mutations, and the K13 gene A578S mutation is detected in the parasite samples.

Specific activation of pro-Infliximab enhances selectivity and safety of rheumatoid arthritis therapy

During rheumatoid arthritis (RA) treatment, long-term injection of antitumor necrosis factor α antibodies (anti-TNFα Abs) may induce on-target toxicities, including severe infections (tuberculosis [TB] or septic arthritis) and malignancy. Here, we used an immunoglobulin G1 (IgG1) hinge as an Ab lock to cover the TNFα-binding site of Infliximab by linking it with matrix metalloproteinase (MMP) -2/9 substrate to generate pro-Infliximab that can be specifically activated in the RA region to enhance the selectivity and safety of treatment. The Ab lock significantly inhibits the TNFα binding and reduces the anti-idiotypic (anti-Id) Ab binding to pro-Infliximab by 395-fold, 108-fold compared with Infliximab, respectively, and MMP-2/9 can completely restore the TNFα neutralizing ability of pro-Infliximab to block TNFα downstream signaling. Pro-Infliximab was only selectively activated in the disease site (mouse paws) and presented similar pharmacokinetics (PKs) and bio-distribution to Infliximab. Furthermore, pro-Infliximab not only provided equivalent therapeutic efficacy to Infliximab but also maintained mouse immunity against Listeria infection in the RA mouse model, leading to a significantly higher survival rate (71%) than that of the Infliximab treatment group (0%). The high-selectivity pro-Infliximab maintains host immunity and keeps the original therapeutic efficiency, providing a novel strategy for RA therapy.

During treatment of rheumatoid arthritis, systemic administration of anti-TNFα antibodies may induce on-target toxicities, limiting their application. The incorporation of IgG1 hinge as an antibody lock generates a pro-Infliximab whose activation is specific to the disease region, enabling safer RA therapy.

Value of Diffusion-Weighted Imaging in Grading Tumours Localized in the Fourth Ventricle Region by Visual and Quantitative Assessments

This study investigated visual and quantitative assessment of diffusion-weighted imaging (DWI) for grading tumours localized in the fourth ventricle region. Patients were diagnosed histopathologically and classified into two groups: those with high-grade (World Health Organization [WHO] grades III and IV) and those with low-grade tumours (benign, WHO grades I and II). DWI signal intensity was described using a five-point scale. Minimum apparent diffusion coefficient (ADC) values were obtained from areas with the lowest signal. The mean signal intensity was significantly higher in high-grade than in low-grade tumours. The mean minimum ADC value was significantly lower in high-grade than low-grade tumours. Marked hyperintensity had sensitivity, specificity, positive predictive value and negative predictive value of 89.7%, 100%, 100% and 94.2%, respectively, when used as a diagnostic tool for high-grade tumours compared with 96.6%, 97.9%, 96.6% and 97.9%, respectively, when using a minimum ADC of 0.9 × 10−3 mm2/s as a diagnostic marker. It was concluded that DWI is helpful in predicting the grades of tumours in the fourth ventricle region.

A unique magnetic resonance imaging feature of glioblastoma multiforme: the 'pseudopalisade' sign

This study was designed to investigate the unique magnetic resonance imaging (MRI) appearance of histopathologically-proven glioblastoma multiforme (GBM) with pseudopalisade necrosis and to assess its value for grading gliomas and providing a differential diagnosis. The study included 169 patients with intracranial masses who underwent surgery and had a proven histopathological diagnosis: 50 with GBM, 77 with gliomas (46 grade II and 31 grade III) and 42 with other intracranial masses (20 metastases, 14 lymphomas and eight abscesses). All patients underwent preoperative brain MRI including post-contrast T(1)-weighted imaging. The presence of the 'pseudopalisade' sign on post-contrast T(1)-weighted images was compared among the different types of brain mass. The frequency of the 'pseudopalisade' sign in GBMs (94.00%) was significantly higher than that seen in grade II and III gliomas (11.69%) and other intracranial masses (7.14%). The 'pseudopalisade' sign on post-contrast T(1)-weighted images was useful for grading gliomas and for differentiating GBM from other brain masses.

Dominant effector genetics in mammalian cells

We have expressed libraries of peptides in mammalian cells to select for trans-dominant effects on intracellular signaling systems. As an example-and to reveal pharmacologically relevant points in pathways that lead to Taxol resistance-we selected for peptide motifs that confer resistance to Taxol-induced cell death. Of several peptides selected, one, termed RGP8.5, was linked to upregulation of expression of the gene ABCB1 (also known as MDR1, for multiple drug resistance) in HeLa cells. Our data indicate that trans-dominant effector peptides can point to potential mechanisms by which signaling systems operate. Such tools may be useful in functional genomic analysis of signaling pathways in mammalian disease processes.

Rab37 is a novel mast cell specific GTPase localized to secretory granules

GTPases regulate a myriad of cellular functions including signal transduction, cytoskeletal organization and membrane trafficking. Rab GTPases act to coordinate the membrane dynamics of cells by organizing and regulating the activity of effector proteins important in vesicle trafficking. Rab37 is a novel Rab GTPase specifically expressed in the MC-9 mast cell line and bone marrow mast cells. Rab37 is 74% identical to Rab26 and 47% identical to Rab8, a GTPase important in Golgi to plasma membrane vesicle trafficking in mammalian cells. When green fluorescent protein tagged Rab37 is expressed in bone marrow mast cells, the secretory granules are labeled. These data suggest that Rab37 may play an important role in mast cell degranulation making this protein a potentially important target for therapeutic intervention in the treatment of allergy.

TNIK, a novel member of the germinal center kinase family that activates the c-Jun N-terminal kinase pathway and regulates the cytoskeleton

Germinal center kinases (GCKs) compose a subgroup of the Ste20 family of kinases. Here we describe the cloning and characterization of a novel GCK family kinase, Traf2- and Nck-interacting kinase (TNIK) that interacts with both Traf2 and Nck. TNIK encodes a polypeptide of 1360 amino acids with eight spliced isoforms. It has 90% amino acid identity to the Nck-interacting kinase in both the N-terminal kinase domain and the C-terminal germinal center kinase homology region. The homology drops to 53% in the intermediate region. TNIK specifically activates the c-Jun N-terminal kinase pathway when transfected into Phoenix-A cells (derivatives of 293 cells), similar to many GCKs. However, in contrast to other GCKs, this activation is mediated solely by the GCK homology region of TNIK. In addition, in Phoenix-A, NIH-3T3, and Hela cells, overexpression of wild type TNIK, but not the kinase mutant form of TNIK, results in the disruption of F-actin structure and the inhibition of cell spreading. Furthermore, TNIK can phosphorylate Gelsolin in vitro. This is the first time that a GCK family kinase is shown to be potentially involved in the regulation of cytoskeleton.

Identification of RIP3, a RIP-like kinase that activates apoptosis and NFkappaB

The tumor necrosis factor receptor 1 (TNFR1) and the Fas receptor recruit complexes formed by the interactions between RIP kinase, TRADD, FADD and RAIDD - adaptor proteins that contain death domains - which in turn recruit other proteins to initiate signaling [1][2][3][4][5]. To identify proteins associated with the TNF signaling pathway, we performed a yeast two-hybrid interaction screen using RIP as bait. We isolated a kinase, RIP3, which shares homology with the kinase domain of RIP and RIP2 (also known as Rick or CARDIAK). RIP3 could be co-immunoprecipitated with RIP, TRAF2 and TNFR1 in mammalian cells. The carboxy-terminal domain of RIP3, like that of RIP, could activate the transcription factor NFkappaB and induce apoptosis when expressed in mammalian cells. Interestingly, this region shares no significant sequence homology to the death domain of RIP, the caspase-recruiting domain (CARD) of RIP2 [6][7][8] or any other apoptosis-inducing domain. As with RIP and RIP2, the kinase domain of RIP3 was not required for either NFkappaB activation or apoptosis induction. Overexpression of a dominant-negative mutant of RIP3 strongly inhibited the caspase activation but not the NFkappaB activation induced by TNFalpha. Therefore, RIP3 appears to function as an intermediary in TNFalpha-induced apoptosis.

Use of PCR/DNA probes to identify circumsporozoite genotype of Plasmodium vivax in China

The paper reports the result of identifying cirumsporozoite (CS) genotype of Plasmodium vivax by using PCR/DNA probe labeled with biotin. The sensitivity of this method to detect patient blood samples was 0.2 parasite/microl and also with high specific to P. vivax. CS genes from 52 blood samples collected from patients with P. vivax in Hainan and Yunnan Provinces were amplified by PCR and 49 were positive by gel-e electrophoresis analysis, positive rate was 94%. Then the amplified CS genes further were probed with special oligoprobes (PV210 and PV247) that hybridized with the predominant CS repeat region and the variant CS repeat region. The results showed 46 (88.5%) PV210 positive and 6 (11.5%) PV247 positive; 2 hybridized with both probes. The variant genotype was present only in samples from Yunnan Province. The above results showed that the PCR/DNA probe labeled with biotin was highly sensitive and specific to P. vivax and found a CS variant genotype of P. vivax in Yunnan Province of China.

Detection of programmed cell death using fluorescence energy transfer

Fluorescence energy transfer (FRET) can be generated when green fluorescent protein (GFP) and blue fluorescent protein (BFP) are covalently linked together by a short peptide. Cleavage of this linkage by protease completely eliminates FRET effect. Caspase-3 (CPP32) is an important cellular protease activated during programmed cell death. An 18 amino acid peptide containing CPP32 recognition sequence, DEVD, was used to link GFP and BFP together. CPP32 activation can be monitored by FRET assay during the apoptosis process.

Identification of an alternative form of human lactoferrin mRNA that is expressed differentially in normal tissues and tumor-derived cell lines

Lactoferrin (LF), traditionally known as an iron-binding protein present in high concentrations in milk and various secretions, has emerged as a multifunctional protein involved in many aspects of the host defense against infection. Recently, LF has been shown to inhibit the growth of solid tumors and reduce experimental metastasis in mice, suggesting that LF also may play a role in the defense against tumorigenesis. Here we provide the sequence of the cDNA and promoter region, the chromosome assignment, and tissue expression pattern of a novel form of LF mRNA (delta LF). The sequence of delta LF mRNA is nearly identical to that of LF mRNA; however, at the 5' end, we find a novel sequence that replaces the N-terminal signal peptide sequence of LF mRNA. We map the delta LF mRNA to human chromosome 3 and find that both delta LF and LF sequences colocalize to the same cloned 90- to 150-kb genomic DNA fragment. We further show that the delta LF mRNA is the product of alternative splicing of the LF gene and likely is specified by use of an alternative promoter. Although we find delta LF mRNA at various levels in 20 of 20 adult and fetal human tissues, we do not find delta LF mRNA in any of 14 diverse tumor-derived cell lines.

Selection of hybrids by affinity capture (SHAC): a method for the generation of cDNAs enriched in sequences from a specific chromosome region

We have established a method for preparing cDNA sublibraries enriched in sequences from specific chromosome regions, called selection of hybrids by affinity capture (SHAC). This procedure can be described in two stages. In the first stage, a particular chromosome region, in this study mouse chromosome 11, was microdissected, followed by PCR amplification with a universal degenerate primer. This material is referred to as the "target" DNA. In the second stage, a mouse liver cDNA library with unique linker-adapter ends, referred to as the "source" cDNA, was hybridized to the biotin-labeled target DNA prepared during the first stage. The resulting DNA duplexes were captured by streptavidin-coated magnetic beads. The cDNAs were released from their biotin-labeled target homologs by alkaline denaturation and recovered by PCR amplification. These cDNAs were referred to as the SHACcDNAs. Specificity of the SHACcDNA to chromosome 11 was verified by FISH analysis. To examine representation of the SHACcDNA, we confirmed the presence of seven genes or single-copy DNA segments known to be localized on mouse chromosome 11, using a dot blot assay. In addition, a second round of SHAC was performed to achieve even higher specificity for the resulting chromosome 11 SHACcDNA. The SHAC technology should facilitate construction of cytogenetically defined cDNA libraries and should assist in the fields of gene discovery and genome mapping.

Cloning of a DNA probe and its application in the detection of Plasmodium falciparum. A preliminary report

The clones containing parasite DNA fragments were screened from a genomic DNA library of Plasmodium falciparum FCC1/HN isolate. A DNA probe derived from clone pBF4 consisting of 3 kilobase pairs hybridizes specifically with P. falciparum DNA but not with human DNA, P. cynomolgi DNA or P. berghei DNA. The nick translated radiolabelled probe can detect 10 pg purified P. falciparum DNA and a 0.001% parasitemia after 24 hours of film exposure. The probe reacts with all microscopically diagnosed P. falciparum samples and 3 of 41 P. vivax samples as well but not with any of 10 human DNA samples.

Multiple loop purification method for selective cultivation of Pentatrichomonas hominis

It is always troublesome having protozoan cultures contaminated with other organisms in the laboratory. The method described here produces high efficiencies of purification for fast moving flagellate protozoa. A human strain Pentatrichomonas hominis was employed in the study to examine the effects of multiple loop tubes on the purification of flagellates. Trichomonads were harvested from a trypticase yeast extract iron-serum-33 (TYI-S-33) medium, adjusted to 2 X 10(5) organisms/ml, and mixed with an equal volume of 2 X 10(6) organisms/ml of bacteria. The isolation was performed at 37 degrees C in TYI-S-33 medium containing a suitable amount of antibiotics (1000 U/ml of penicillin, 1000 micrograms/ml of streptomycin, and 4 micrograms/ml of fungizone). Four days later, 10(6) organisms/ml of protozoa, free of bacteria, were observed at the other end of the single loop and the double loop tubes. About the same amount of flagellates could be found at the other end of the triple loop tube six days after incubation. The traditional U-shaped tubes were used as controls and 10(5) cells/ml of flagellates were recovered in the presence of bacteria two days after incubation. An axenic culture of P. hominis was successfully isolated from the feces of a Formosan rock-monkey, Macaca cyclopsis, by this method. Purified trichomonads were recovered from a double loop purification tube five days after incubation.