Protective efficacy of a global HIV-1 mosaic vaccine against heterologous SHIV challenges in rhesus monkeys.

The global diversity of HIV-1 represents a critical challenge facing HIV-1 vaccine development. HIV-1 mosaic antigens are bioinformatically optimized immunogens designed for improved coverage of HIV-1 diversity. However, the protective efficacy of such global HIV-1 vaccine antigens has not previously been evaluated. Here, we demonstrate the capacity of bivalent HIV-1 mosaic antigens to protect rhesus monkeys against acquisition of infection following heterologous challenges with the difficult-to-neutralize simian-human immunodeficiency virus SHIV-SF162P3. Adenovirus/poxvirus and adenovirus/adenovirus vector-based vaccines expressing HIV-1 mosaic Env, Gag, and Pol afforded a significant reduction in the per-exposure acquisition risk following repetitive, intrarectal SHIV-SF162P3 challenges. Protection against acquisition of infection correlated with vaccine-elicited binding, neutralizing, and functional nonneutralizing antibodies, suggesting that the coordinated activity of multiple antibody functions may contribute to protection against difficult-to-neutralize viruses. These data demonstrate the protective efficacy of HIV-1 mosaic antigens and suggest a potential strategy for the development of a global HIV-1 vaccine. PAPERCLIP:

Evaluation of a mosaic HIV-1 vaccine in a multicentre, randomised, double-blind, placebo-controlled, phase 1/2a clinical trial (APPROACH) and in rhesus monkeys (NHP 13-19).

BACKGROUND: More than 1·8 million new cases of HIV-1 infection were diagnosed worldwide in 2016. No licensed prophylactic HIV-1 vaccine exists. A major limitation to date has been the lack of direct comparability between clinical trials and preclinical studies. We aimed to evaluate mosaic adenovirus serotype 26 (Ad26)-based HIV-1 vaccine candidates in parallel studies in humans and rhesus monkeys to define the optimal vaccine regimen to advance into clinical efficacy trials. METHODS: We conducted a multicentre, randomised, double-blind, placebo-controlled phase 1/2a trial (APPROACH). Participants were recruited from 12 clinics in east Africa, South Africa, Thailand, and the USA. We included healthy, HIV-1-uninfected participants (aged 18-50 years) who were considered at low risk for HIV-1 infection. We randomly assigned participants to one of eight study groups, stratified by region. Participants and investigators were blinded to the treatment allocation throughout the study. We primed participants at weeks 0 and 12 with Ad26.Mos.HIV (5 × 1010 viral particles per 0·5 mL) expressing mosaic HIV-1 envelope (Env)/Gag/Pol antigens and gave boosters at weeks 24 and 48 with Ad26.Mos.HIV or modified vaccinia Ankara (MVA; 108 plaque-forming units per 0·5 mL) vectors with or without high-dose (250 µg) or low-dose (50 µg) aluminium adjuvanted clade C Env gp140 protein. Those in the control group received 0·9% saline. All study interventions were administered intramuscularly. Primary endpoints were safety and tolerability of the vaccine regimens and Env-specific binding antibody responses at week 28. Safety and immunogenicity were also assessed at week 52. All participants who received at least one vaccine dose or placebo were included in the safety analysis; immunogenicity was analysed using the per-protocol population. We also did a parallel study in rhesus monkeys (NHP 13-19) to assess the immunogenicity and protective efficacy of these vaccine regimens against a series of six repetitive, heterologous, intrarectal challenges with a rhesus peripheral blood mononuclear cell-derived challenge stock of simian-human immunodeficiency virus (SHIV-SF162P3). The APPROACH trial is registered with ClinicalTrials.gov, number NCT02315703. FINDINGS: Between Feb 24, 2015, and Oct 16, 2015, we randomly assigned 393 participants to receive at least one dose of study vaccine or placebo in the APPROACH trial. All vaccine regimens demonstrated favourable safety and tolerability. The most commonly reported solicited local adverse event was mild-to-moderate pain at the injection site (varying from 69% to 88% between the different active groups vs 49% in the placebo group). Five (1%) of 393 participants reported at least one grade 3 adverse event considered related to the vaccines: abdominal pain and diarrhoea (in the same participant), increased aspartate aminotransferase, postural dizziness, back pain, and malaise. The mosaic Ad26/Ad26 plus high-dose gp140 boost vaccine was the most immunogenic in humans; it elicited Env-specific binding antibody responses (100%) and antibody-dependent cellular phagocytosis responses (80%) at week 52, and T-cell responses at week 50 (83%). We also randomly assigned 72 rhesus monkeys to receive one of five different vaccine regimens or placebo in the NHP 13-19 study. Ad26/Ad26 plus gp140 boost induced similar magnitude, durability, and phenotype of immune responses in rhesus monkeys as compared with humans and afforded 67% protection against acquisition of SHIV-SF162P3 infection (two-sided Fisher's exact test p=0·007). Env-specific ELISA and enzyme-linked immunospot assay responses were the principal immune correlates of protection against SHIV challenge in monkeys. INTERPRETATION: The mosaic Ad26/Ad26 plus gp140 HIV-1 vaccine induced comparable and robust immune responses in humans and rhesus monkeys, and it provided significant protection against repetitive heterologous SHIV challenges in rhesus monkeys. This vaccine concept is currently being evaluated in a phase 2b clinical efficacy study in sub-Saharan Africa (NCT03060629). FUNDING: Janssen Vaccines & Prevention BV, National Institutes of Health, Ragon Institute of MGH, MIT and Harvard, Henry M Jackson Foundation for the Advancement of Military Medicine, US Department of Defense, and International AIDS Vaccine Initiative.

Assessment of the Safety and Immunogenicity of 2 Novel Vaccine Platforms for HIV-1 Prevention: A Randomized Trial.

BACKGROUND: A prophylactic HIV-1 vaccine is a global health priority. OBJECTIVE: To assess a novel vaccine platform as a prophylactic HIV-1 regimen. DESIGN: Randomized, double-blind, placebo-controlled trial. Both participants and study personnel were blinded to treatment allocation. (ClinicalTrials.gov: NCT01215149). SETTING: United States, East Africa, and South Africa. PATIENTS: Healthy adults without HIV infection. INTERVENTION: 2 HIV-1 vaccines (adenovirus serotype 26 with an HIV-1 envelope A insert [Ad26.EnvA] and adenovirus serotype 35 with an HIV-1 envelope A insert [Ad35.Env], both administered at a dose of 5 × 1010 viral particles) in homologous and heterologous combinations. MEASUREMENTS: Safety and immunogenicity and the effect of baseline vector immunity. RESULTS: 217 participants received at least 1 vaccination, and 210 (>96%) completed follow-up. No vaccine-associated serious adverse events occurred. All regimens were generally well-tolerated. All regimens elicited humoral and cellular immune responses in nearly all participants. Preexisting Ad26- or Ad35-neutralizing antibody titers had no effect on vaccine safety and little effect on immunogenicity. In both homologous and heterologous regimens, the second vaccination significantly increased EnvA antibody titers (approximately 20-fold from the median enzyme-linked immunosorbent assay titers of 30-300 to 3000). The heterologous regimen of Ad26-Ad35 elicited significantly higher EnvA antibody titers than Ad35-Ad26. T-cell responses were modest and lower in East Africa than in South Africa and the United States. LIMITATIONS: Because the 2 envelope inserts were not identical, the boosting responses were complex to interpret. Durability of the immune responses elicited beyond 1 year is unknown. CONCLUSION: Both vaccines elicited significant immune responses in all populations. Baseline vector immunity did not significantly affect responses. Second vaccinations in all regimens significantly boosted EnvA antibody titers, although vaccine order in the heterologous regimen had a modest effect on the immune response. PRIMARY FUNDING SOURCE: International AIDS Vaccine Initiative, National Institutes of Health, Ragon Institute, Crucell Holland.

Induction of HIV-1-specific mucosal immune responses following intramuscular recombinant adenovirus serotype 26 HIV-1 vaccination of humans.

BACKGROUND: Defining mucosal immune responses and inflammation to candidate human immunodeficiency virus type 1 (HIV-1) vaccines represents a current research priority for the HIV-1 vaccine field. In particular, it is unclear whether intramuscular immunization can elicit immune responses at mucosal surfaces in humans. METHODS: In this double-blind, randomized, placebo-controlled clinical trial, we evaluated systemic and mucosal immune responses to a candidate adenovirus serotype 26 (Ad26) vectored HIV-1 envelop (Env) vaccine in baseline Ad26-seronegative and Ad26-seropositive healthy volunteers. Systematic mucosal sampling with rectal Weck-Cel sponges and rectal biopsies were performed. RESULTS: Intramuscular immunization elicited both systemic and mucosal Env-specific humoral and cellular immune responses in the majority of subjects. Individuals with preexisting Ad26-specific neutralizing antibodies had vaccine-elicited immune responses comparable to those of subjects who were Ad26 seronegative. We also observed no increase in activated total or vector-specific mucosal CD4+ T lymphocytes following vaccination by either histopathology or flow cytometry. CONCLUSIONS: These data demonstrate that a single intramuscular administration of this Ad26-vectored HIV-1 Env vaccine elicited both systemic and mucosal immune responses in humans. Induction of antigen-specific humoral and cellular mucosal immunity was not accompanied by a detectable increase in mucosal inflammation. CLINICAL TRIALS REGISTRATION: NCT01103687.

First-in-human evaluation of a hexon chimeric adenovirus vector expressing HIV-1 Env (IPCAVD 002).

BACKGROUND: We report the first-in-human safety and immunogenicity assessment of a prototype hexon chimeric adenovirus (Ad) serotype 5 (Ad5) vector containing the hexon hypervariable regions of Ad serotype 48 (Ad48) and expressing human immunodeficiency virus (HIV) type 1 EnvA. METHODS: Forty-eight Ad5 and Ad48 seronegative, HIV-uninfected subjects were enrolled in a randomized, double-blind, placebo-controlled, dose escalation phase 1 study. Four groups of 12 subjects received 10(9) to 10(11) viral particles (vp) of the Ad5HVR48.EnvA.01 vaccine (n = 10 per group) or placebo (n = 2 per group) at week 0 or weeks 0, 4, and 24. Safety and immunogenicity were assessed. RESULTS: Self-limited reactogenicity was observed after the initial immunization in the highest (10(11) vp) dose group. Responses in vaccinees included Ad48 neutralizing antibody (nAb) titers higher than Ad5 nAb titers, EnvA-specific enzyme-linked immunosorbent assay titers, and EnvA-specific enzyme-linked immunospot assay responses, and these responses generally persisted at week 52. At week 28 in the 10(9), 10(10), and 10(11) vp 3-dose groups, geometric mean EnvA enzyme-linked immunosorbent assay titers were 5721, 10 929, and 3420, respectively, and Ad48 nAb titers were a median of 1.7-fold higher than for Ad5. CONCLUSIONS: Ad5HVR48.ENVA.01 was safe, well tolerated, and immunogenic at all doses tested. Vector-elicited nAb responses were greater for Ad48 than Ad5, confirming that Ad-specific nAbs in humans are primarily, but not exclusively, directed against the hexon hypervariable regions. Clinical Trials Registration. NCT00695877.

Characterization of humoral and cellular immune responses elicited by a recombinant adenovirus serotype 26 HIV-1 Env vaccine in healthy adults (IPCAVD 001).

BACKGROUND: Adenovirus serotype 26 (Ad26) has been developed as a novel candidate vaccine vector for human immunodeficiency virus type 1 (HIV-1) and other pathogens. The primary safety and immunogenicity data from the Integrated Preclinical/Clinical AIDS Vaccine Development Program (IPCAVD) 001 trial, the first-in-human evaluation of a prototype Ad26 vector-based vaccine expressing clade A HIV-1 Env (Ad26.ENVA.01), are reported concurrently with this article. Here, we characterize in greater detail the humoral and cellular immune responses elicited by Ad26.ENVA.01 in humans. METHODS: Samples from the IPCAVD 001 trial were used for humoral and cellular immunogenicity assays. RESULTS: We observed a dose-dependent expansion of the magnitude, breadth, and epitopic diversity of Env-specific binding antibody responses elicited by this vaccine. Antibody-dependent cell-mediated phagocytosis, virus inhibition, and degranulation functional activity were also observed. Env-specific cellular immune responses induced by the vaccine included multiple CD8(+) and CD4(+) T-lymphocyte memory subpopulations and cytokine secretion phenotypes, although cellular immune breadth was limited. Baseline vector-specific T-lymphocyte responses were common but did not impair Env-specific immune responses in this study. CONCLUSION: Ad26.ENVA.01 elicited a broad diversity of humoral and cellular immune responses in humans. These data support the further clinical development of Ad26 as a candidate vaccine vector. CLINICAL TRIALS REGISTRATION: NCT00618605.

First-in-human evaluation of the safety and immunogenicity of a recombinant adenovirus serotype 26 HIV-1 Env vaccine (IPCAVD 001).

BACKGROUND: We report the first-in-human safety and immunogenicity assessment of a prototype Ad26 vector-based human immunodeficiency virus (HIV) vaccine in humans. METHODS: Sixty Ad26-seronegative, healthy, HIV-uninfected subjects were enrolled in a randomized, double-blinded, placebo-controlled, dose-escalation phase 1 study. Five groups of 12 subjects received 10(9)-10(11) vp of the Ad26-EnvA vaccine (N = 10/group) or placebo (N = 2/group) at weeks 0 and 24 or weeks 0, 4, and 24. Safety and immunogenicity were assessed. RESULTS: Self-limited reactogenicity was observed after the initial immunization at the highest (10(11) vp) dose. No product-related SAEs were observed. All subjects who received the Ad26-EnvA vaccine developed Ad26 NAb titers, EnvA-specific enzyme-linked immunosorbent assays (ELISA) titers, and EnvA-specific enzyme-linked immunospot assays (ELISPOT) responses. These responses persisted at week 52. At week 28 in the 10(9), 10(10), 10(11) vp 3-dose and the 10(10) and 5 × 10(10) vp 2-dose groups, geometric mean EnvA ELISA titers were 6113, 12 470, 8545, 3470, and 9655 and mean EnvA ELISPOT responses were 397, 178, 736, 196, and 1311 SFC/10(6) peripheral blood mononuclear cells, respectively. CONCLUSION: This Ad26 vectored vaccine was generally safe and immunogenic at all doses tested. Reactogenicity was minimal with doses of 5 × 10(10) vp or less. Ad26 is a promising new vaccine vector for HIV-1. CLINICAL TRIALS REGISTRATION: NCT00618605.

A prophylactic multivalent vaccine against different filovirus species is immunogenic and provides protection from lethal infections with Ebolavirus and Marburgvirus species in non-human primates.

The search for a universal filovirus vaccine that provides protection against multiple filovirus species has been prompted by sporadic but highly lethal outbreaks of Ebolavirus and Marburgvirus infections. A good prophylactic vaccine should be able to provide protection to all known filovirus species and as an upside potentially protect from newly emerging virus strains. We investigated the immunogenicity and protection elicited by multivalent vaccines expressing glycoproteins (GP) from Ebola virus (EBOV), Sudan virus (SUDV), Taï Forest virus (TAFV) and Marburg virus (MARV). Immune responses against filovirus GP have been associated with protection from disease. The GP antigens were expressed by adenovirus serotypes 26 and 35 (Ad26 and Ad35) and modified Vaccinia virus Ankara (MVA) vectors, all selected for their strong immunogenicity and good safety profile. Using fully lethal NHP intramuscular challenge models, we assessed different vaccination regimens for immunogenicity and protection from filovirus disease. Heterologous multivalent Ad26-Ad35 prime-boost vaccination regimens could give full protection against MARV (range 75%-100% protection) and EBOV (range 50% to 100%) challenge, and partial protection (75%) against SUDV challenge. Heterologous multivalent Ad26-MVA prime-boost immunization gave full protection against EBOV challenge in a small cohort study. The use of such multivalent vaccines did not show overt immune interference in comparison with monovalent vaccines. Multivalent vaccines induced GP-specific antibody responses and cellular IFNγ responses to each GP expressed by the vaccine, and cross-reactivity to TAFV GP was detected in a trivalent vaccine expressing GP from EBOV, SUDV and MARV. In the EBOV challenge studies, higher humoral EBOV GP-specific immune responses (p = 0.0004) were associated with survival from EBOV challenge and less so for cellular immune responses (p = 0.0320). These results demonstrate that it is feasible to generate a multivalent filovirus vaccine that can protect against lethal infection by multiple members of the filovirus family.

Correction: A prophylactic multivalent vaccine against different filovirus species is immunogenic and provides protection from lethal infections with Ebolavirus and Marburgvirus species in non-human primates.

[This corrects the article DOI: 10.1371/journal.pone.0192312.].

Ganciclovir-mediated elimination of HSV-Tk+ T cells and cure of graft-vs-host disease in an allogeneic bone marrow transplantation model in the rat.

OBJECTIVE: Suicide gene therapy for leukemia aims to benefit from T cells in the BM graft, by reducing the probability of leukemia relapse (GVL), while severe complications of graft-vs-host disease (GVHD) may be avoided. In an allogeneic rat BMT model we defined the conditions to induce a lethal GVHD with HSV-Tk gene-transduced T cells. We studied the feasibility to rescue the animals by conditional elimination of the T cells with ganciclovir (GCV) treatment. METHODS: Allogeneic T cells transduced with a retroviral vector encoding the HSV-Tk suicide gene were added in varying numbers to a BM graft. Expression of HSV-Tk strongly increases the cytolytic effect of GCV, thereby allowing elimination of overreactive T cells at will. Various experimental conditions were tested in the rat model. RESULTS: A relation between the number of HSV-Tk(+) T cells added to the BM graft and GVHD development was found. GCV treatment resulted in selective HSV-Tk(+) T-cell elimination in blood and tissues but not in abrogation of GVHD due to persistence of HSV-Tk(-) T cells. T cells in unmanipulated rat BM normally have a low risk to induce GVH but when they are administered in combination with high numbers of HSV-Tk(+) T cells there is an apparent increase in their GVH-inducing potential. When HSV-Tk(+) T cells are added to T cell-depleted BM a consequently developing GVH can be controlled by GCV treatment with 60-70% of the animals surviving. CONCLUSIONS: We show that T cell-mediated suicide gene therapy within the context of allo-BMT can be applied with success. The apparent limitation in the number of transduced as well as nontransduced T cells that can be safely added to the BM graft should be taken into consideration when designing human suicide gene therapy protocols.

Protective efficacy of adenovirus/protein vaccines against SIV challenges in rhesus monkeys.

Preclinical studies of viral vector-based HIV-1 vaccine candidates have previously shown partial protection against neutralization-resistant virus challenges in rhesus monkeys. In this study, we evaluated the protective efficacy of adenovirus serotype 26 (Ad26) vector priming followed by purified envelope (Env) glycoprotein boosting. Rhesus monkeys primed with Ad26 vectors expressing SIVsmE543 Env, Gag, and Pol and boosted with AS01B-adjuvanted SIVmac32H Env gp140 demonstrated complete protection in 50% of vaccinated animals against a series of repeated, heterologous, intrarectal SIVmac251 challenges that infected all controls. Protective efficacy correlated with the functionality of Env-specific antibody responses. Comparable protection was also observed with a similar Ad/Env vaccine against repeated, heterologous, intrarectal SHIV-SF162P3 challenges. These data demonstrate robust protection by Ad/Env vaccines against acquisition of neutralization-resistant virus challenges in rhesus monkeys.

Reduced graft-versus-host disease-inducing capacity of T cells after activation, culturing, and magnetic cell sorting selection in an allogeneic bone marrow transplantation model in rats.

Graft-versus-host disease (GvHD), a major complication of allogeneic bone marrow transplantation, has been ascribed to mature T cells in the graft. Because T cells play an important role in engraftment of the bone marrow and decrease the probability of relapse of leukemia, a treatment strategy was developed to preserve the benefits of T cells in the graft and to control the severe complications of GvHD. This can be accomplished by the genetic modification of donor T cells with a suicide gene that allows their selective in vivo elimination and subsequently the abrogation of GvHD. For clinical benefit the alloreactivity of herpes simplex virus thymidine kinase (HSV-TK) gene-transduced T cells should be retained. Therefore, we investigated the influence of gene transduction and the selection procedure on T cells. We demonstrated that activation and culturing of T cells reduce their capacity to induce lethal GvHD in an allogeneic rat bone marrow transplantation model. Furthermore, positive immunomagnetic selection of gene-transduced T cells resulted in loss of the GvHD-inducing capacity of HSV-TK(+) T cells directly after MACS (magnetic cell sorting) selection; this loss could be recovered by a 1-day expansion of the selected T cells. No effect on alloreactivity was observed to be caused by the gene transduction procedure. Our study resulted in the development of an optimized culture and gene transduction protocol with preservation of T cell alloreactivity. Treatment of transplanted rats with ganciclovir resulted in a rapid reduction in the number of HSV-TK(+) T cells in the peripheral blood and in increased survival of the animals.

Monitoring of developing graft-versus-host disease mediated by herpes simplex virus thymidine kinase gene-transduced T cells.

Introduction of the HSV-Tk suicide gene into allogeneic T cells offers the possibility to control developing host-reactive cells within the context of allogeneic bone marrow transplantation (BMT). Sensitive quantitative detection methods are a prerequisite to monitor genetically modified T cells in peripheral blood and tissues to study their involvement in graft-versus-host disease (GVHD)-induced lesions as well as their disappearance or persistence after ganciclovir (GCV)-induced suicide. We monitored the alloreactivity of HSV-Tk-transduced T cells after BMT by studying their in vivo distribution and quantity in peripheral blood and in tissues in a WAG/Rij into Brown Norway fully mismatched rat allogeneic BMT model. Genetically modified T cells were quantified in blood and tissues by fluorescence-activated cell sorting, immunohistochemical analysis, and real-time quantitative polymerase chain reaction (PCR) analysis. A significant increase in the number of allogeneic HSV-Tk(+) T cells was found in particular in spleen and lymph nodes and large numbers were found in tongue, skin, and intestines. In blood, an increase in HSV-Tk(+) T cells closely preceded clinical symptoms of GVHD. Real-time quantitative PCR proved to be a fast and accurate tool by which to quantify transduced T cells both in blood and tissues. This enables the study of the in vivo alloreactivity of retrovirus-transduced cells and the response of HSV-Tk-expressing T cells to GCV-induced suicide therapy. Furthermore, we showed the potential use to study specific cause-effect relationships in a broad range of animal and clinical studies involving genetically engineered cells.

Ad35 and ad26 vaccine vectors induce potent and cross-reactive antibody and T-cell responses to multiple filovirus species.

Filoviruses cause sporadic but highly lethal outbreaks of hemorrhagic fever in Africa in the human population. Currently, no drug or vaccine is available for treatment or prevention. A previous study with a vaccine candidate based on the low seroprevalent adenoviruses 26 and 35 (Ad26 and Ad35) was shown to provide protection against homologous Ebola Zaire challenge in non human primates (NHP) if applied in a prime-boost regimen. Here we have aimed to expand this principle to construct and evaluate Ad26 and Ad35 vectors for development of a vaccine to provide universal filovirus protection against all highly lethal strains that have caused major outbreaks in the past. We have therefore performed a phylogenetic analysis of filovirus glycoproteins to select the glycoproteins from two Ebola species (Ebola Zaire and Ebola Sudan/Gulu,), two Marburg strains (Marburg Angola and Marburg Ravn) and added the more distant non-lethal Ebola Ivory Coast species for broadest coverage. Ad26 and Ad35 vectors expressing these five filovirus glycoproteins were evaluated to induce a potent cellular and humoral immune response in mice. All adenoviral vectors induced a humoral immune response after single vaccination in a dose dependent manner that was cross-reactive within the Ebola and Marburg lineages. In addition, both strain-specific as well as cross-reactive T cell responses could be detected. A heterologous Ad26-Ad35 prime-boost regime enhanced mainly the humoral and to a lower extend the cellular immune response against the transgene. Combination of the five selected filovirus glycoproteins in one multivalent vaccine potentially elicits protective immunity in man against all major filovirus strains that have caused lethal outbreaks in the last 20 years.

Onset of transcription in Patella vulgata coincides with cell cycle elongation and expression of tubulin genes.

In this study we show that the onset of embryonic transcription in the marine snail Patella vulgata coincides with the start of the sixth cleavage, when the cell-cycle elongates and divisions become asynchronous. Changes in mRNA content before and after onset of transcription were initially demonstrated by in vitro translation of isolated mRNA from different stages. Before the sixth cleavage, three major mRNAs encoding proteins of 36, 50 and 52 kDa were present. These proteins probably correspond to cyclin A and B and ribonucleotide reductase. After this stage, three major proteins with molecular weights of 36.5, 52.5 and 53 kDa were found after in vitro translation. Via hybrid selected translation and differential screening cDNAs corresponding to the 52.5 and 53 kDa proteins were cloned. The encoded proteins resemble tubulins from other animals to a high extent (between 96.5 and 93.1% identity for α-tubulin and 97.9 and 75.9% for ß-tubulin). The 36.5 kDa protein is the previously described actin. Both tubulins were expressed at or shortly after the first asynchronous division after the fifth cleavage.