Shirley Longacre

Institut Pasteur, Lutetia Parisorum, Île-de-France, France

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Publications (36)116.36 Total impact

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    ABSTRACT: Plasmodium falciparum merozoite surface protein 5 (PfMSP5) is an attractive blood stage vaccine candidate because it is both exposed to the immune system and well conserved. To evaluate its interest, we investigated the association of anti-PfMSP5 IgG levels, in the context of responses to two other conserved Ags PfMSP1p19 and R23, with protection from clinical episodes of malaria in cross-sectional prospective studies in two different transmission settings.
    PLoS ONE 07/2014; 9(7):e101737. · 3.53 Impact Factor
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    ABSTRACT: Extensive polymorphism in the genes encoding for surface antigens of Plasmodium falciparum and Plasmodium vivax has been a serious impediment for malaria vaccine development. One such antigen is the merozoite surface protein-1 (MSP-1). The MSP-1 precursor after proteolytic cleavage generates a C-terminal fragment of 42 kDa (MSP-1(42)), which subsequently produces 33 kDa (MSP-1(33)) and 19 kDa (MSP-1(19)) fragments. Since MSP-1(42) is currently being considered as a candidate for vaccine development against blood stage malaria it is important to catalogue the existing diversity in this antigen in natural P. vivax infections. Here we investigated the level of genetic diversity in the PvMSP-1(42) gene fragment in 95 single clone P. vivax infections in Sri Lanka. We observed that the PvMSP-1(19) fragment was highly conserved among these samples, whereas the PvMSP-1(33) fragment exhibited extensive diversity with 39 polymorphic amino acid positions (corresponding to 27 haplotypes, 19 of which were unique to Sri Lanka). Of these 27 PvMSP-1(42) haplotypes, 24 belonged to hypervariable region (HVR) T1-T7 types, while 3 haplotypes were generated by interallelic recombination between T1/T3 (HVRT8-T9) and T2/T3 (HVRT10). In addition, we analysed 107 PvMSP-1(42) sequences (corresponding to 62 haplotypes, H28 to H89) deposited in the NCBI GenBank database from other regions of the world. Seventy-four of these correspond to 9 of the 10 HVR types (HVR-T7 was unique to Sri Lanka). Two novel HVR types, T11 and T12, with a double recombination between HVR-T1/T3 and HVRT6/T2, were derived from South America and Thailand, respectively. T cell epitope polymorphism arising due to non-synonymous substitutions in PvMSP-1(33) may result in differential binding of the polymorphic peptides to class II MHC alleles, inducing different host immune responses. In conclusion, under low transmission and unstable malaria conditions prevalent in Sri Lanka, extensive allelic polymorphism was evident at PvMSP-1(33) due to recombination, mutation, and balancing selection. In contrast, PvMSP-1(19) is highly conserved(,) greatly enhancing its suitability as a malaria vaccine candidate.
    Infection, genetics and evolution: journal of molecular epidemiology and evolutionary genetics in infectious diseases 10/2010; 11(1):145-56. · 3.22 Impact Factor
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    ABSTRACT: Effective vaccines to combat malaria are urgently needed, but have proved elusive in the absence of validated correlates of natural immunity. Repeated blood stage infections induce antibodies considered to be the main arbiters of protection from pathology, but their essential functions have remained speculative. This study evaluated antibody dependent respiratory burst (ADRB) activity in polymorphonuclear neutrophils (PMN) induced by Plasmodium falciparum merozoites and antibodies in the sera of two different African endemic populations, and investigated its association with naturally acquired clinical protection. Respiratory bursts by freshly isolated PMN were quantified by chemiluminescence readout in the presence of isoluminol, which preferentially detects extra-cellular reactive oxygen species (ROS). Using a standardized, high throughput protocol, 230 sera were analyzed from individuals of all age groups living in meso- (Ndiop) or holo-endemic (Dielmo) Senegalese villages, and enrolled in a cross-sectional prospective study with intensive follow-up. Statistical significance was determined using non-parametric tests and Poisson regression models. The most important finding was that PMN ADRB activity was correlated with acquired clinical protection from malaria in both high and low transmission areas (P = 0.006 and 0.036 respectively). Strikingly, individuals in Dielmo with dichotomized high ADRB indexes were seventeen fold less susceptible to malaria attacks (P = 0.006). Complementary results showed that ADRB activity was (i) dependent on intact merozoites and IgG opsonins, but not parasitized erythrocytes, or complement, (ii) correlated with merozoite specific cytophilic IgG1 and IgG3 antibody titers (P<0.001 for both), and (iii) stronger in antisera from a holo-endemic compared to a meso-endemic site (P = 0.002), and reduced in asymptomatic carriers (P<0.001). This work presents the first clearly demonstrated functional antibody immune correlate of clinical protection from Plasmodium falciparum malaria, and begs the question regarding the importance of ADRB by PMN for immune protection against malaria in vivo.
    PLoS ONE 03/2010; 5(3):e9871. · 3.53 Impact Factor
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    ABSTRACT: Natural antibody (IgG + IgM) responses to putative vaccine candidate, Plasmodium vivax Merozoite Surface Protein-4, in acute vivax malaria patients in endemic and non-endemic areas of Sri Lanka, were assayed by indirect ELISA using PvMSP-4 baculovirus derived recombinant protein. The study populations were from two vivax malaria endemic areas, Anuradhapura and Kataragama and from a non-endemic area, Colombo. PvMSP4 appeared to be immunogenic in all test populations with a prevalence of 80%, 62% and 62% from Colombo, Anuradhapura and Kataragama, respectively. A significantly higher prevalence and antibody magnitude was recorded for non-endemic Colombo, but with no significant differences between individuals previously not exposed to malaria and those with prior exposure. A positive trend in responders from Kataragama was evident between the antibody prevalence and previous exposure. We previously reported the antibody response to PvMSP-1 (p19 and p42) using the same battery of sera, and when comparisons were drawn, more than 80% from each test area responded to at least one of the three antigens tested. Importantly, 7%, 11% and 4% of individuals from Colombo, Anuradhapura, and Kataragama, respectively, preferentially recognized PvMSP-4. Responders to MSP-1p42 and p19 in paired combination showed higher prevalence compared with combinations of MSP-1 with MSP-4.
    Ceylon Journal of Science (Biological Sciences) 06/2009; 37(1).
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    ABSTRACT: A number of laboratories around the world are producing Plasmodium falciparum erythrocyte-stage vaccine candidates in the pursuit of a vaccine against clinical malaria disease. These candidates are often based on the same parasite protein. Rigorous clinical development and testing of multiple candidates is limited by available resources, which underscores the need to conduct comparative studies of the different vaccine candidates. The purpose of this study was to compare five different candidate proteins all based on P. falciparum merozoite surface protein-1 (MSP1). After investigators submitted their candidates, basic protein profiles were evaluated in a blinded fashion by an independent laboratory, and groups of rabbits were immunized with the proteins. Sera obtained from the rabbits were compared for antibody titers by ELISA and for functional activity by an in vitro parasite growth inhibition assay (GIA) activity, again in a blinded fashion. In selected cases the fine specificity of the antibodies was assessed. Significant differences in immunogenicity as well as the functional activity of antibodies induced by the various vaccine candidates were noted. Data from this study can assist in making decisions for further clinical development of MSP1-based candidates, and this process sets a precedent for future comparisons of malaria vaccine candidates.
    Vaccine 12/2008; 27(10):1651-60. · 3.49 Impact Factor
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    ABSTRACT: Immunogenicity testing of Plasmodium falciparum antigens being considered as malaria vaccine candidates was undertaken in rabbits. The antigens compared were recombinant baculovirus MSP-1(19) and five Pichia pastoris candidates, including two versions of MSP-1(19), AMA-1 (domains I and II), AMA-1+MSP-1(19), and fused AMA-1/MSP-1(19)). Animals were immunized with equimolar amounts of each antigen, formulated in Montanide ISA720. The specificities and titers of antibodies were compared using immunofluorescence assays and enzyme-linked immunosorbent assay (ELISA). The antiparasite activity of immunoglobulin G (IgG) in in vitro cultures was determined by growth inhibition assay, flow cytometry, lactate dehydrogenase assay, and microscopy. Baculovirus MSP-1(19) immunizations produced the highest parasite-specific antibody titers in immunofluorescence assays. In ELISAs, baculovirus-produced MSP-1(19) induced more antibodies than any other single MSP-1(19) immunogen and three times more MSP-1(19) specific antibodies than the AMA-1/MSP-1(19) fusion. Antibodies induced by baculovirus MSP-1(19) gave the highest levels of growth inhibition in HB3 and 3D7 parasite cultures, followed by AMA-1+MSP-1(19) and the AMA-1/MSP-1(19) fusion. With the FCR3 isolate (homologous to the AMA-1 construct), antibodies to the three AMA-1-containing candidates gave the highest levels of growth inhibition at high IgG concentrations, but antibodies to baculovirus MSP-1(19) inhibited as well or better at lower IgG concentrations. The two P. pastoris-produced MSP-1(19)-induced IgGs conferred the lowest growth inhibition. Comparative analysis of immunogenicity of vaccine antigens can be used to prioritize candidates before moving to expensive GMP production and clinical testing. The assays used have given discriminating readouts but it is not known whether any of them accurately reflect clinical protection.
    Clinical and vaccine Immunology: CVI 07/2008; 15(9):1345-55. · 2.37 Impact Factor
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    ABSTRACT: The Plasmodium MSP-1 is a promising malaria vaccine candidate. However, the highly polymorphic nature of the MSP-1 gene (msp1) presents a potential obstacle for effective vaccine development. To investigate the evolutionary history of msp1 polymorphism in P. vivax, we construct phylogenetic trees of msp1 from P. vivax and related monkey malaria parasite species. All P. vivax msp1 alleles cluster in the P. vivax lineage and are not distributed among other species. Similarly, all P. cynomolgi msp1 alleles cluster in the P. cynomolgi lineage. This suggests that, in contrast to presumed ancient origin of P. falciparum msp1 polymorphism, the origin of P. vivax msp1 polymorphism is relatively recent. We observed positive selection in the P. vivax lineage but not in P. cynomolgi. Also, positive selection acts on different regions of msp1 in P. vivax and P. falciparum. This study shows that the evolutionary history of msp1 differs greatly among parasite lineages.
    Molecular and Biochemical Parasitology 12/2007; 156(1):74-9. · 2.24 Impact Factor
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    ABSTRACT: We report here, for the first time, a comparison of naturally acquired antibody responses to the 42 and 19 kDa C-terminal processing products of Plasmodium vivax Merozoite Surface Protein-1 assayed by ELISA using p42 and p19 baculovirus-derived recombinant proteins, respectively. Test populations comprised patients with microscopy confirmed acute P. vivax infections from two regions endemic for vivax malaria where low transmission and unstable malaria conditions prevail, and a non-endemic urban area, in Sri Lanka. The antibody prevalence to the two proteins, both at the individual and population levels, tend to respond more to p42 than to p19 in all test areas, where >14% of individuals preferentially recognized p42, compared with <2% for p19. In patients with no previous exposure to malaria, 21% preferentially recognized p42, whereas none exclusively recognized p19. A significantly lower prevalence of anti-p19 IgM, but not anti-p42 IgM, was observed among residents from endemic areas compared with their non-endemic counterparts. Individuals from both endemic areas produced significantly less anti-p19 IgM compared with anti-p42 IgM. IgG1 was the predominant IgG isotype for both antigens in all individuals. With increasing exposure to malaria in both endemic areas, anti-p19 antibody responses were dominated by the functionally important IgG1 and IgG3 isotypes, with a concurrent reduction in IgM that was lacking in the non-endemic residents. This antibody switch was also reflected for PvAMA-1 as we previously reported with the identical battery of sera. In contrast, the antibody switch for p42 was restricted to endemic residents with more extensive exposure. These results suggest that an IgM-dominated antibody response against the p42 polymorphic region in endemic residents may interfere with the development of an IgG-dominated "protective" isotype shift to p19, that may complicate vaccine development.
    International Journal for Parasitology 02/2007; 37(2):199-208. · 3.40 Impact Factor
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    ABSTRACT: Recombinant homologues of the Plasmodium merozoite surface protein 1 C-terminus are leading blood stage malaria vaccine candidates. MSP1 is anchored to the merozoite plasma membrane in vivo by a glycosyl-phosphatidyl-inositol (GPI) moiety, implicated in malaria pathology. Two types of recombinant Plasmodium falciparum MSP1p19 (PfMSP1p19) expressed in baculovirus/insect cells are described here: (1) a soluble, secreted form (PfMSP1p19S) and (2) detergent soluble cellular form(s) (PfMSP1p19+A), released from the infected cell surface by treatment with GPI specific phosphatidyl-inositol phospholipase C (PI-PLC). Soluble and cellular PfMSP1p19 were purified and characterized using SDS-PAGE, mass spectrometry (MS), N-terminal amino acid sequencing, gel filtration and glycan analyses. Quantitative inositol dosage suggested that surface GPI processed entities constituted only 14% of the purified cellular PfMSP1p19+A, with GPI unprocessed forms likely recovered in the endoplasmic reticulum. Nevertheless, this preparation has dramatic immuno-stimulatory activity to be described elsewhere. The interest of these results for both malaria specific and generic vaccine development are discussed.
    Vaccine 09/2006; 24(33-34):5997-6008. · 3.49 Impact Factor
  • Molecular and Biochemical Parasitology 12/2005; 144(1):100-3. · 2.24 Impact Factor
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    ABSTRACT: Antibodies to polymorphic block 2 of the Plasmodium falciparum merozoite surface protein 1 (MSP-1) present a paradoxical association with acquired protection against clinical malaria, while showing restricted and fixed specificity, reminiscent of antigenic sin. We report here that these antibodies present a highly imbalanced, peptide-specific light chain distribution. This was not observed with several other parasite-derived peptides or antigens. These data point to a skewed immune response to MSP-1 block 2 that is constrained both in specificity and chain usage. This is the first report of a biased response to polymorphic epitopes of a surface antigen in malaria parasites.
    Immunology and Cell Biology 09/2005; 83(4):392-5. · 4.21 Impact Factor
  • Molecular and Biochemical Parasitology 08/2005; 142(1):110-5. · 2.24 Impact Factor
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    ABSTRACT: Glycosylphosphatidylinositol (GPI) membrane anchors of Plasmodium falciparum surface proteins are thought to be important factors contributing to malaria pathogenesis, and anti-GPI antibodies have been suggested to provide protection by neutralizing the toxic activity of GPIs. In this study, IgG responses against P. falciparum GPIs and a baculovirus recombinant MSP1p19 antigen were evaluated in two distinct groups of 70 patients each, who were hospitalized with malaria. Anti-GPI IgGs were significantly lower in patients hospitalized with confirmed cerebral malaria compared to those with mild malaria (P < 0.01) but did not discriminate for fatal outcome. In contrast, a specific marker of the anti-parasite immunity, as monitored by the anti-MSP1p19 IgG response, was similar in both cerebral and mild malaria individuals, although it was significantly lower in a subgroup with fatal outcomes. These results are consistent with a potential anti-toxin role for anti-GPI antibodies associated with protection against cerebral malaria.
    Microbes and Infection 04/2005; 7(4):682-7. · 2.73 Impact Factor
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    ABSTRACT: Antibodies to Plasmodium falciparum C-terminal merozoite surface protein 1 (PfMSP-1p19) have been correlated with protection against malaria, but this association may apply to many merozoite antigens. To address this question, we conducted a prospective serological study of 205 individuals in an active 5-month clinical survey in a Senegalese village where malaria is mesoendemic. Before the 2000 rainy season, antibody responses specific for recombinant baculovirus PfMSP-1p19 or merozoite extracts were compared with 2 in vitro functional antibody activities (inhibition of parasite grown and erythrocyte invasion) and with the number of clinical episodes during 5 months of follow-up. Antibody levels to PfMSP-1p19 and merozoite extract correlated, respectively, with erythrocyte invasion and parasite growth inhibition. Although antibody levels to both antigen preparations were associated with age, functional parameters were not. High levels of anti-PfMSP-1p19 immunoglobulin G were associated with reduced malaria in an age-adjusted multivariate analysis. These results support baculovirus PfMSP-1p19-based vaccine development.
    The Journal of Infectious Diseases 02/2005; 191(2):264-71. · 5.78 Impact Factor
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    ABSTRACT: Recombinant protein DBP, expressed in a bacculoviral vector, representing the native Plasmodium vivax Duffy Binding Protein (DBP) was used in an indirect ELISA to assay the total anti-DBP antibody (IgM + IgG) responses in Sri Lankan patients with acute vivax malaria. The test populations were selected from two malaria endemic areas, Anuradhapura (n=64) and Kataragama (n=93), and from an area non-endemic for malaria, Colombo (n=91). The prevalences of anti-DBP antibodies were 53%, 38% and 44% from Anuradhapura, Kataragama and Colombo, respectively. A significant difference (Chi-square test, p<0.05) was found between the proportions of responders and non-responders to DBP in Kataragama. Responding proportions of individuals previously exposed (PE) and previously not exposed (PNE) differed significantly only in Colombo (Chi-square test, p<0.05). Significant differences (Mann-Whitney U test, p<0.05) were evident between anti-DBP antibody magnitudes; (i) in Anuradhapura and Kataragama and (ii) of PNE individuals from Colombo and the total responders (both PNE + PE) from Anuradhapura. A significant difference (Mann-Whitney U test, p<0.01) in the end point titers (EPT) between PNE and PE individuals was limited to Colombo. Associations between host factors (age, parasitaemia, number of past infections, the duration between present and penultimate infections and the days of symptoms) and total antibody responses (antibody magnitudes and EPT) were examined (Spearman Correlation coefficient, p<0.05). The significant associations found were between (i) parasitaemia and then total antibody responses of residents in Anuradhapura, (ii) between the parasitaemia group <0.01% and the total antibody response of residents in Kataragama (a negative correlation), (iii) number of past infections in Colombo and (iv) the duration between the present and penultimate infections in Colombo and in Anuradhapura with EPT and the antibody magnitudes, respectively.
    Joint Annual Sessions o University of Colombo Faculty of Science and Medicine, University of Colombo; 06/2004
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    ABSTRACT: Recombinant protein DBP, expressed in a bacculoviral vector, representing the native Plasmodium vivax Duffy Binding Protein (DBP) was used in an indirect ELISA to assay the total anti-DBP antibody (IgM + IgG) responses in Sri Lankan patients with acute vivax malaria. The test populations were selected from two malaria endemic areas, Anuradhapura (n=64) and Kataragama (n=93), and from an area non-endemic for malaria, Colombo (n=91). The prevalences of anti-DBP antibodies were 53%, 38% and 44% from Anuradhapura, Kataragama and Colombo, respectively. A significant difference (Chi-square test, p<0.05) was found between the proportions of responders and non-responders to DBP in Kataragama. Responding proportions of individuals previously exposed (PE) and previously not exposed (PNE) differed significantly only in Colombo (Chi-square test, p<0.05). Significant differences (Mann-Whitney U test, p<0.05) were evident between anti-DBP antibody magnitudes; (i) in Anuradhapura and Kataragama and (ii) of PNE individuals from Colombo and the total responders (both PNE + PE) from Anuradhapura. A significant difference (Mann-Whitney U test, p<0.01) in the end point titers (EPT) between PNE and PE individuals was limited to Colombo. Associations between host factors (age, parasitaemia, number of past infections, the duration between present and penultimate infections and the days of symptoms) and total antibody responses (antibody magnitudes and EPT) were examined (Spearman Correlation coefficient, p<0.05). The significant associations found were between (i) parasitaemia and then total antibody responses of residents in Anuradhapura, (ii) between the parasitaemia group <0.01% and the total antibody response of residents in Kataragama (a negative correlation), (iii) number of past infections in Colombo and (iv) the duration between the present and penultimate infections in Colombo and in Anuradhapura with EPT and the antibody magnitudes, respectively.
    Joint Annual Sessions of University of Colombo faculties of Science and Medicine, University of Colombo; 06/2004
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    ABSTRACT: Recombinant protein DBP, expressed in a bacculoviral vector, representing the native Plasmodium vivax Duffy Binding Protein (DBP) was used in an indirect ELISA to assay the total anti-DBP antibody (IgM + IgG) responses in Sri Lankan patients with acute vivax malaria. The test populations were selected from two malaria endemic areas, Anuradhapura (n=64) and Kataragama (n=93), and from an area non-endemic for malaria, Colombo (n=91). The prevalences of anti-DBP antibodies were 53%, 38% and 44% from Anuradhapura, Kataragama and Colombo, respectively. A significant difference (Chi-square test, p<0.05) was found between the proportions of responders and non-responders to DBP in Kataragama. Responding proportions of individuals previously exposed (PE) and previously not exposed (PNE) differed significantly only in Colombo (Chi-square test, p<0.05). Significant differences (Mann-Whitney U test, p<0.05) were evident between anti-DBP antibody magnitudes; (i) in Anuradhapura and Kataragama and (ii) of PNE individuals from Colombo and the total responders (both PNE + PE) from Anuradhapura. A significant difference (Mann-Whitney U test, p<0.01) in the end point titers (EPT) between PNE and PE individuals was limited to Colombo. Associations between host factors (age, parasitaemia, number of past infections, the duration between present and penultimate infections and the days of symptoms) and total antibody responses (antibody magnitudes and EPT) were examined (Spearman Correlation coefficient, p<0.05). The significant associations found were between (i) parasitaemia and then total antibody responses of residents in Anuradhapura, (ii) between the parasitaemia group <0.01% and the total antibody response of residents in Kataragama (a negative correlation), (iii) number of past infections in Colombo and (iv) the duration between the present and penultimate infections in Colombo and in Anuradhapura with EPT and the antibody magnitudes, respectively.
    Joint Annual sessions of University of Colombo, Faculties of Science and Medicine, University of Colombo, Sri Lanka; 06/2004
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    ABSTRACT: Merozoite surface protein 1 (MSP1) is the major protein component on the surface of the merozoite, the erythrocyte-invasive form of the malaria parasite Plasmodium. Present in all species of Plasmodium, it undergoes two distinct proteolytic maturation steps during the course of merozoite development that are essential for invasion of the erythrocyte. Antibodies specific for the C-terminal maturation product, MSP1-19, can inhibit erythrocyte invasion and parasite growth. This polypeptide is therefore considered to be one of the more promising malaria vaccine candidates. We describe here the crystal structure of recombinant MSP1-19 from P.falciparum (PfMSP1-19), the most virulent species of the parasite in humans, as a complex with the Fab fragment of the monoclonal antibody G17.12. This antibody recognises a discontinuous epitope comprising 13 residues on the first epidermal growth factor (EGF)-like domain of PfMSP1-19. Although G17.12 was raised against the recombinant antigen expressed in an insect cell/baculovirus system, it binds uniformly to the surface of merozoites from the late schizont stage, showing that the cognate epitope is exposed on the naturally occurring MSP1 polypeptide complex. Although the epitope includes residues that have been mapped to regions recognised by invasion-inhibiting antibodies studied by other workers, G17.12 does not inhibit erythrocyte invasion or MSP1 processing.
    Journal of Molecular Biology 06/2003; 328(5):1091-103. · 3.96 Impact Factor
  • Acta Crystallographica Section A Foundations of Crystallography 08/2002; 58. · 2.07 Impact Factor