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Today, the use of natural products and nanostructures has increased. Given the reports on beneficial effects of various organotellurane compounds on types of visceral leishmaniasis, we decided to investigate the effect of TeO2 NPs on Leishmania major (L. major). Tellurium can cause cell apoptosis in cancer cells without activating the caspase-pathway. TeO2 NPs at first synthesized and the structure was checked by XRD, SEM and EDS tests. The cytotoxic effect of TeO2 NPs against L. major promastigotes, amastigotes and macrophages was assessed by MTT test or counting. The possible apoptosis of L. major by TeO2 NPs was evaluated by flow cytometry test. For in vivo assay, the lesions of infected BALB/c mice with L. major promastigotes were treated with TeO2 NPs, then the lesion size and survival rate were evaluated. The synthesis of TeO2 with tetragonal structure was confirmed by XRD. The combination of nanorods and nanoflakes and the presence of Te were proven by SEM and EDS, respectively. According the effects of nanoparticle on promastigotes and amastigotes, the IC50 values of TeO2 after 72 h of incubation were 15.13 and 52.22 µg/ml, respectively. TeO2 NPs induced apoptosis in about 41% of promastigotes. The ulcer greatly healed and survival rate was higher in treated mice compared to those in control group. Based on the data, favorable anti-leishmanial properties were observed by using TeO2 NPs. TeO2 NPs have cytotoxic impacts on L. major promastigotes and amastigotes in vitro and in vivo and may be regarded as a therapy option.

Background: The extract of myrtle plant contains polyphenolic compounds that show antibacterial, antiviral, and anti-parasitic properties. We aimed to investigate the therapeutic effect of aqueous and ethanolic myrtle extract against leishmaniasis caused by L. major in vivo and in vitro conditions. Methods: This study was carried out in Tarbiat Modares University, Tehran, Iran in 2018. Aqueous and ethanolic extract of myrtle plant at 6.25 to 400 mg/ml concentrations were tested on Leishmania major promastigotes, non-infected macrophages, and macrophages infected with amastigotes in vitro using counting, MTT and flow cytometry techniques. Then, BALB/c mice were treated with ethanolic, aqueous and a mixture of both extracts of myrtle plant. The treatment was carried out for four weeks. Then, the effectiveness of the herbal medicine was assessed by measuring wounds diameters, mice weights and their mortality rate on weekly basis. Results: The IC50 values of aqueous and ethanolic extracts for promastigotes were 7.86 and 11.66 μg/mL respectively. The IC50 values of the aqueous and ethanolic extracts for amastigotes were 12.5 and 47.2 μg/mL respectively. Flow cytometry indicates 62.88% and 60.16% apoptosis induced by ethanolic and aqueous extract of myrtle plant respectively. The lowest parasitic load was seen in the group treated with ethanolic extract. Conclusion: The lesion sizes for treated groups with extracts were similar to those treated with glucantime. Oral administration instead of injection is another advantage of myrtle plant over glucantime, which makes the herb easy and more practical.

Attractive Toxic Bait (ATB) is a low risk practical method to cockroach control. This study aimed to evaluate efficacy of a newly modified eight-chamber-olfactometer for attractiveness experiments. Different stages of German cockroaches were exposed to carbohydrate-rich and protein-rich foods and their attractions were tested both at ambient conditions and in the modified olfactometer. In the latter method, cockroaches were released into the main chamber of olfactometer and their attraction to food compounds placed in test chambers were recorded as the number of captured cockroaches in test chambers. The direct attractiveness test was performed in plastic pans. Repellency of fipronil insecticide was performed with prepared bait powder using olfactometer. Data were subjected to analysis of variance with Tukey’s Test,P ≤ 0.05. Different notes should be considered when using introduced olfactometer like precision when opening the test chambers valves, the fan speed, placement of cardboard shelter in both test and main chambers, and initial starvation of cockroaches. Roasted peanut, banana and biscuits powder were the most attractive foods for cockroaches. The females significantly preferred roasted peanut and the males significantly preferred banana and roasted peanut. These results were similar to the results of direct attracted cockroaches. The cockroaches have repellency to fipronil but attractiveness of bait with 0.01% concentration was significantly higher than cockroach diet. Generally, three factors should be considered in formulation of ATB like un-repellency of the a.i, attractiveness of bait compositions, and palatability of bait texture. The olfactometer introduced in this study could be used by researchers to study cockroach behaviors.

Background: The adverse effects and increased resistance of drugs necessities the discovery of novel combination therapy. Objectives: This study aimed to examine the effects of Artemisinin plus glucantime or shark cartilage extract on the Iranian strain of Leishmania major (MRHO/IR/75/ER) in vitro and in vivo. Methods: In in vitro experiments, the effects of drugs and their combination in different concentrations (3.12 - 400 µg/mL) on the promastigotes, amastigotes, and un-infected macrophage cells were evaluated. In in vivo experiments, infected BALB/c mice were used as a cutaneous leishmaniasis model to evaluate the effects of the drugs and their combinations with different routes of administrations (namely Artemisinin: oral, ointment, and intraperitoneal; glucantime: intraperitoneal, intramuscular, intralesional, and subcutaneous; shark cartilage extract: oral) on parasite burden, lesion size, and immune system modulation. Results: The results revealed that Artemisinin and glucantime in combination with shark cartilage extract had greater effects on promastigotes than either Artemisinin or glucantime (P < 0.05), and that the combinations also had high cytotoxic effects on promastigotes and uninfected macrophages (P = 0.001). These combinations had more inhibitory effects on amastigotes and infected macrophages than promastigotes. The lesion sizes and parasite burden in the spleen decreased against the combinations of the drugs in different administrations. It was also noticed that the best combination administration route of Artemisinin and glucantime, as strong inducers of INF-γ and Th1 immune response, were ointment and intramuscular, respectively (P < 0.05). Conclusions: The findings indicate that Artemisinin- glucantime or Artemisinin- Shark cartilage combinations are effective inhibitors of L. major. However, further clinical trials are recommended to evaluate the effects of these combinations in human subjects.

Toxoplasma gondii is one of the most common meat-born zoonoses that infect all warm-blooded animals and humans. Sheep (Ovis aries) is one of the main reservoirs of T. gondii worldwide, and the infections induce various sequels, such as abortion and stillbirth. The present study aimed to identify the effects of humidity on the prevalence of T. gondii in sheep in high- and low-humidity regions. Heart samples from 200 slaughtered sheep (140 samples from a high-humidity region and 60 samples from a low-humidity region) were collected from Hormozgan Province (south of Iran). The samples were tested by nested PCR targeting the RE gene. Genotyping was performed by the PCR-RFLP method using the SAG3 and GRA6 genes. Some isolates were sequenced and recorded in the GenBank. T. gondii DNA was detected in 10.71 percent of the samples from the highly humid region, whereas no positive samples were detected in the low-humidity region. Genotyping revealed that all isolates belonged to the T. gondii type III genotype. Our study indicated that humidity is an important factor for the prevalence of T. gondii in sheep. Additionally, our study also showed the dominance of type III strain of T. gondii in sheep in the south of Iran.

In the present study, we evaluated induced immune responses following DNA vaccine containing cocktail or fusion of LeIF, LACK and TSA genes or each gene alone. Mice were injected with 100 µg of each plasmid containing the gene of insert, plasmid DNA alone as the first control group or phosphate buffer saline as the second control group. Then, cellular and humoral responses, lesion size were measured for all groups. All vaccinated mice induced Th1 immune responses against Leishmania characterized by higher IFN-γ and IgG2a levels compared with control groups (p

There is no effective vaccine for the prevention and elimination of leishmaniasis. For this reason, we assessed the protective effects of DNA vaccines containing LeIF, TSA genes alone, or LeIF-TSA fusion against cutaneous leishmaniasis pEGFP-N1 plasmid (empty vector) and phosphate buffer saline (PBS) were used as control groups. Therefore, cellular and humoral immune responses were evaluated before and after the challenge with Leishmania major. Lesion diameter was also measured 3-12 weeks after challenge. All immunized mice with plasmid DNA encoding Leishmania antigens induced the partial immunity characterized by increased IFN-γ and IgG2a levels compared with control groups (p < 0.001). Furthermore, the immunized mice showed significant reduction in mean lesion sizes compared with mice in empty vector and PBS groups (p < 0.05). The reduction in lesion diameter was 29.3%, 34.1%, and 46.2% less in groups vaccinated with LeIF, TSA, and LeIF-TSA, respectively, than in PBS group at 12th week post infection. IFN/IL-4 and IgG2a/IgG1 ratios indicated that group receiving LeIF-TSA fusion had the highest IFN-γ and IgG2a levels. In this study, DNA immunization promoted Th1 immune response characterized by higher IFN-γ and IgG2a levels and also reduction in lesion size. These results showed that a bivalent vaccine containing two distinct antigens may induce more potent immune responses against leishmaniasis.

Objective To evaluate the efficacy of some medicinal plants and systemic glucantime in a comparative manner against the causative agent of cutaneous leishmaniasis both in vitro and in BALB/c mice. Methods For in vivo testing, inbred mice were challenged with Leishmania major parasites and the resultant ulcers were treated with extract based-ointments applied topically two times per day for a period of 20 days. A group of 56 mice were randomly divided into 7 subgroups. The control group received the ointment void of extracts, whereas the reference group received glucantime only. The efficacy of treatments was evaluated by measuring ulcer diameter, parasite burden and NO production. Results Our results indicated that plant extract based-ointments were effective in reducing ulcer size and parasite burden in spleens, but their effects did not differ significantly from that of glucantime. The plant extracts tested in this study were able to increase NO production that helped parasite suppression. Conclusions Our findings indicate that the tested plant extracts are effective against Leishmania major both during in vitro and in vivo experiments, but further researches are required to recommend a potential plant extract as an alternative drug.

Objective: To evaluate immunoglobulin G (IgG) avidity as a useful and reliable technique in diagnosing toxoplasmosis in pregnant women referring to therapeutic centers of Alborz Province (Iran) in 2014, against two other tests, IgG and immunoglobulin G (IgM) antiToxoplasma. Methods: Serum samples (468 in total) were obtained from different therapeutic centers in Karaj City. ELISA method was used to test the anti-Toxoplasma avidity of IgG, IgM and IgG. The data were analyzed by descriptive statistical methods and Chi-square test (P < 0.05) using SPSS 17.0. Results: Anti-Toxoplasma tests of IgM and IgG were positive in 9 and 86 samples respectively. Also, a borderline IgM was detected in 2 suspected samples. In addition, among all positive and suspected samples, 79 cases indicated high titers of IgG avidity, 7 cases were of low titers and 1 case was of a borderline titer. The prevalence of anti-Toxoplasma antibodies was 20%. The sera which showed high avidity index was obtained from patients at chronic phase of infection (92%) while those which showed low avidity levels were from patients at acute toxoplasmosis (77.7%). Conclusions: This study clearly showed that acute and chronic phases of toxoplasmosis could be differentiated with the aid of IgG avidity test. This test may also assist in recognizing old and newly acquired infections.

Background: The first line treatment against cutaneous leishmaniasis is meglumine antimoniate. This drug is expensive and has serious side effects, including development of drug resistance. Objectives: In this research, because of paucity of information, the apoptotic and leishmanicidal effects of ketotifen and cromolyn sodium, as cell membrane stabilizer drugs, were investigated on standard strain of Leishmania major. Methods: In this experimental study, L. major parasites were first cultured in RPM1 1640 media, supplemented with 10% fetal bovine serum (FBS) and antibiotics at 24 ± 1oC. Drug concentrations of 5, 10, 15, and 20 µg/mL were then added to L. major culture at 24-, 48- and 72-hour intervals. The 3 - (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide (MTT) tetrazolium assays were performed to determine parasite viability and drug toxicity. Leishmania major promastigotes were augmented to the in vitro cultured macrophages (J774 cells) and then incubated for 72 hours. Half maximal inhibitory concentration (IC50) were ascertained by counting the parasites. The inhibitory effect of the drugs were compared with that of glucantime. Flow cytometry was performed in the next step, to evaluate apoptosis. Each test was repeated three times. Results: IC50 values of ketotifen and cromolyn sodium after 72 hours were calculated to be 2.04 and 17.67 µg/mL for promastigotes and 0.12 and 14.79 µg/mL for amastigotes, respectively. The results of MTT assays showed 20% and 35% promastigote viability after 72 hours of exposure to ketotifen and cromolyn sodium at 20 µg/mL concentration. Apoptosis in ketotifen and cromolyn sodium was quantified to be 11.52% and 9.96% in promastigotes and 99.5% and 98.6% in amastigote-infected macrophages, respectively. The results indicated that the drugs induce early and late apoptosis in parasites. All treatments produced results, which differed significantly from the control groups (P < 0.05). Conclusions: Drugs used in this study, especially Ketotifen, showed lower toxicity yet similar anti-leishmanial effects on both forms, as cromolyn sodium did. It could be suggested that further investigations about the in vivo effects of these drugs, as candidates for cutaneous leishmaniasis treatment, are required.

Objective To identify the etiological agent, host and vector of anthroponotic cutaneous leishmaniasis in Kerman City, Southeastern Iran, using nested PCR and restriction fragment length polymorphism-PCR techniques. Methods Conducting this cross-sectional study in Kerman City from March to November 2014, we collected and morphologically identified 1 075 sandflies. The phlebotomine sand flies were then molecularly examined for harboring Leishmania parasites and blood meal preference using nested PCR and restriction fragment length polymorphism-PCR techniques respectively. Results Phlebotomus sergenti (P. sergenti) and Phlebotomus papatasi were found to comprise 94.3% and 5.7% of catches respectively. Nested PCR assay, applied for kDNA minicircles amplification, detected Leishmania tropica in P. sergenti at the rate of 3.6%. Also, restriction fragment length polymorphism-PCR assay on mtDNA fragments demonstrated that 41.8% of P. sergenti population preferred to feed on human blood rather than other animals. Conclusions This is the first study to provide molecular bases for incriminating P. sergenti as the main vector of Leishmania tropica, the causative agent of anthroponotic cutaneous leishmaniasis, in Kerman City. This study emphasized the high predominance, strong anthropophilic behavior and peridomicile adaptation of P. sergenti population in the focus.

This study aimed to provide a systematic review regarding anti- Giardia effect of different Iranian plant extracts used in vivo and in vitro on cysts and trophozoites. Many reports indicated that most of plant extracts used as anti- Giardia were obtained from Liliaceae, Apiaceae, Asteraceae, and Myrtaceae. These extracts included different fractions such as aqueous, alcoholic and chloroform extracts as well as Soxhlet extraction of juice or essence. The findings of this review showed that hydroalcoholic extract of asafoetida, Chenopodium botrys , and chloroformic extract of feverfew ( Tanacetum parthenium ) have the maximum effect (100% efficacy) on in vitro application against Giardia . However, the highest in vivo effect of 100% therapeutic significance was recorded for the extract of Allium sativum at 80 mg/mL concentration. Given the plant species richness of Iran in terms of herbal medicines with fewer side effects, it can be a good alternative to chemical drugs used to treat giardiasis.

Artemisia aucheri Bioss contains flavonoid, coumarin and santonin with antioxidant, antimicrobial and antileishmanial effects. The current study was aimed to comparatively evaluate the effects of spring and autumn extracts of A. aucheri Bioss on Leishmania major both in-vitro and in-vivo conditions.HPLC analysis was used to evaluate the percentages of compounds in spring and autumn extracts of A. aucheri. For in-vitro assay, the effect of different concentrations of spring and autumn extracts of A. aucheri was tested on L. major promastigotes and amastigotes. MTT and flow cytometry methods were used to evaluate the cytotoxicity and probable apoptosis of A. aucheri extracts on L. major promastigotes. On the other hand, for in-vivo assay, the extracts were used as ointments to treat lesions developed on BALB/c mice after 28 days post inoculation of L. major. The diameter of lesions and the survival rates of infected BALB/c mice were measured weekly for a period of two months.The HPLC analysis showed the substance Quercitrin was present in the spring A. aucheri extract but not in the autumn extract. The mean numbers of amastigotes in each treated macrophage with the spring and autumn A. aucheri extracts were 1.2 and 1.8 respectively, which showed statistically significant differences (P 0.05). Flow cytometry revealed that the spring and autumn A. aucheri extracts caused about 32% and 3.78% apoptosis respectively. The inhibitory concentration (IC50) of spring and autumn A. aucheri extracts to amastigotes were determined to be 90 μg/mL and 183 μg/mL respectiovely. In-vivo, the diameter of lesions treated with the spring A. aucheri extract was significantly less (P 0.05) compared to those treated with the autumn extract (2.6 and 7.8 mm respectively). Also, mice treated with spring A. aucheri extract had higher survival rates compared to control group.Given the above results, it can be concluded that spring A. aucheri extract has a greater fatality effect on L. major promastigotes in-vitro compared to the autum extract. In addition, the spring extract has stronger therapeutic effect on lesions caused by L. major in BALB/c mice than the autum extract.

Background: The severe acute respiratory syndrome (SARS) is a life threatening viral infection caused by a positive, single stranded RNA virus from the enveloped coronaviruse family. Associated with fever, cough, and respiratory complications, the illness causes more than 15% mortality worldwide. So far, there is no remedy for the illness except supportive treatments. However, the main viral proteinase has recently been regarded as a suitable target for drug design against SARS infection due to its vital role in polyproteins processing necessary for coronavirus reproduction. Objectives: The present in silico study was designed to evaluate the effects of anti HIV-1 proteases inhibitors, approved for clinical applications by US FDA, on SARS proteinase inhibition. Methods: In the present study, docking and molecular dynamic experiments were applied to examine the effect of inhibitors on coronavirus proteinase under physiological conditions of similar pH, temperature, and pressure in aqueous solution. Hex software version 5.1 and GROMACS 4.5.5 were used for docking analysis throughout this work. Results: The calculated parameters such as RMSD, RMSF, MSD, dipole moment, diffusion coefficient, binding energy, and binding site similarity indicated effective binding of inhibitors to SARS proteinase resulting in their structural changes, which coincide with proteinase inhibition. Conclusions: The inhibitory potency of HIV 1 protease inhibitors to cronovirus proteinase was as follows: LPV > RTV > APV > TPV > SQV. Lopinavir and Saquinavir were the most and the least powerful inhibitors of cronovirus proteinase, respectively.

Leishmaniasis is a growing health challenge in many parts of Iran, including Kerman Province. Investigating vector ecology and parasite-harboring capacity is prerequisite to the disease control measures. This study included six provincial sites namely Bam (Bm), Dehbakri (Di), Jiroft (Jt), Mohammad-Abad (Md), Rostam-Abad (Rd) and Darb-e-Behesht (Dt) where sand flies were trapped. The specimens were then identified before being exposed to DNA extraction. PCR-RFLP was used to detect leishmanial infection rates and feeding preference of vectors. Diversity indices indicated that the highest effective numbers of species was in plain sites, whereas, the highest expected numbers of species was in mountainous sites. P. papatasi and P. sergenti showed similar feeding preferences to both human and animal bloods. P. papatasi from indoor catches was found infected with Leishmania major at a 2% rate. The ITS1 gene sequences of isolated parasites were >99% similar to related GenBank haplotypes. Bam and Rostam-Abad remain active foci of both types of cutaneous leishmaniasis (CL). Md and Di are prone to visceral leishmaniasis (VL). Jt is not at risk of anthroponotic cutaneous leishmaniasis (ACL) due to absence of P. sergenti. Sand flies are absent in Dt, probably because of high elevation and cold climate. In conclusion, patterns of climate and ecosystem changes and vector-host-reservoirs interactions must be carefully scrutinized if leishmaniasis is to be controlled in the stricken sites.

As an enzyme acting at the junction of gluconeogenic pathway, phosphoenolpyruvate carboxykinase (PEPCK) controls substrate flow from Krebs cycle toward glucose production. Therefore, it would be advantageous to design effective inhibitors to inactivate PEPCK in diabetes mellitus and other abnormalities caused by insulin resistance. Such inhibitors may compensate the metabolic consequences of ex-activity of PEPCK at these conditions. Understanding the mechanism by which inhibitors exert their effect on enzyme activity is of great interest for designing stronger inhibitors. In the present work, molecular dynamic simulations were used to study enzyme-inhibitor interactions. Our results indicate that inhibitors of PEPCK with their short chains interact with enzyme active site through non-covalent interactions of electrostatic and hydrogen bond nature. The data also show that inhibitors neither reach a stable state in their binding site nor make static complex with the enzyme active site. Instead, they interact with functional groups of active site residues in a dynamic fashion. In this way, oxalate and sulfoacetate carrying two negative groups of higher charge density and optimum spacing from each other, show more dynamic behavior (lower stability in their binding site) and more inhibitory effects than other inhibitors used (phosphonoformate, phosphoglycolate and 3-phosphonopropionate).

Hemoglobin is a tetrameric protein with two alpha and two beta subunits binds oxygen in a cooperative manner. In dominant tetrameric form of fish hemoglobin carry more than 90 percent of oxygen from gill to tissues at 20° C. The tetrameric form of fish hemoglobin is changed to monomeric form at low oxygen pressure in order to increase its oxygen affinity. This is one of adaptive mechanisms used by different kinds of fish. The major aim of this paper is to study the molecular basis of shirbot hemoglobin adaptation mechanism to various environmental conditions. Using different methods such as ion exchange chromatography, UV-Vis, fluorescence and circular dichroism spectroscopy, we extracted the main tetrameric fraction of shirbot hemoglobin and studied the structural characteristics of shirbot and human hemoglobins in a comparative way. Our results showed that tetrameric form of shirbot hemoglobin has less stable and loosely folded structure in contrast to human hemoglobin. Our data also indicate, in case of exposure to life-threatening environmental factors such as low oxygen level, acidic pH, oxidizing chemicals and other water pollutants especially detergents (surfactants) triggering tetramer to monomer dissociation in shirbot hemoglobin is more prominently than in human hemoglobin. The resulting monomer of hemoglobin has more oxygen affinity and could take up oxygen more strongly even at low pressure. We hypothesize that this mechanism helps shirbot to adapt and to survive at such harsh environment. The mechanism that is may be adapted by other fish species.

Ribonuclease-A is a small enzyme contains an active site with positive charges for its substrate. His(12) and His(119) of its active site play critical role in enzyme catalysis. Salts show a bell-shaped profile on enzyme activity with an optimum salt concentration of about 0.1 M for optimum activity. The mechanism of decreased activity of the enzyme at low salt concentrations is not clear. In this work, we made a new effort to study the molecular events causing inactivation of RNase-A at low concentrations of NaCl. Our molecular dynamic result confirms that decrease in salt concentrations below an optimal level leads to an enzyme structure with lower dynamism and flexibility than that needed for optimum activity.

Protein Z is a plasma protein functioning as a carrier for ZPI. Protein Z also accelerates inhibitory effect of ZPI on factor Xa by 1000-fold. Inhibition of coagulation cascade via FXa by ZPI and other serpins is very important safety factor for normal homeostasis protecting human life against unwanted thrombosis. In the present work using native structure of PZ, ZPI, FXa and in a dynamic simulation, using NAMD software, the ternary complex was studied in an up to 10 nanoseconds protocol. Rely on trajectory analyses, we postulated that PZ binds ZPI by using its SP-like domain and through noncovalent forces. PZ then transfers ZPI through-out the blood, and by using its GLA domain and a bivalent cation of calcium, PZ binds to phospholipid bilayers (e.g., platelet) where the FXa is preallocated. In case of PZ-ZPI binding to plasma membrane, a series of complementary interactions take place between FXa, and PZ-ZPI complex including interactions between RCL loop of ZPI and catalytic site of FXa and some take place between long arm of PZ (composed of GLA, EGF1, and EGF2 domains) and GLA domain of FXa. In our claim these complementary interactions lead PZ to bind correctly to prelocated FXa.

In the present study, the effects of administrating 4 mM and 300 mg kg(-1) b.wt. of quinolinic acid were studied, in vitro and in vivo, respectively, to evaluate its inhibitory activity on phosphoenolpyruvate carboxykinase in diabetic rats. The results of in vitro studies have clearly indicated the inhibitory effect of quinolinic acid on enzyme activity. The hill plot showed the binding stoichiometry of quinolinic acid per enzyme to be 4:1. The in vivo studies showed that intra peritoneal injection of 300 mg kg(-1) b.wt. initiates reduction of blood glucose level in 1 h after injection, restoring the blood glucose to its normal level at 2 h post injection and keeping it constant for at least further 4 h. Based on present results we concluded that quinolinic acid and hence its precursor tryptophan having induced obvious hypoglycemic effects in normal and diabetic rats at high enough concentrations, they are worthy of further study and research for their hyperglycemic effect in other diabetic animal models.

Background Among viral enzymes, the human HIV-1 protease comprises the most interesting target for drug discovery. There are increasing efforts focused on designing more effective inhibitors for HIV-1 protease in order to prevent viral replication in AIDS patients. The frequent and continuous mutation of HIV-1 protease gene creates a formidable obstacle for enzyme inhibition which could not be overcome by the traditional single drug therapy. Nowadays, in vitro and in silico studies of protease inhibition constitute an advanced field in biological researches. In this article, we tried to simulate protease-substrate complexes in different states; a native state and states with whiskers deleted from one and two subunits. Molecular dynamic simulations were carried out in a cubic box filled with explicit water at 37°C and in 1atomsphere of pressure. Results Our results showed that whisker truncation of protease subunits causes the dimer structure to decrease in compactness, disrupts substrate-binding site interactions and changes in flap status simultaneously. Conclusions Based on our findings we claim that whisker truncation even when applied to a single subunit, threats dimer association which probably leads to enzyme inactivation. We may postulate that inserting a gene to express truncated protease inside infected cells can interfere with protease dimerization. The resulted proteases would presumably have a combination of native and truncated subunits in their structures which exert no enzyme activities as evidenced by the present work. Our finding may create a new field of research in HIV gene therapy for protease inhibition, circumventing problems of drug resistance.