LALLT (Loxosceles Allergen-Like Toxin) from the venom of Loxosceles intermedia: Recombinant expression in insect cells and characterization as a molecule with allergenic properties

Probiotics and the reduction of SARS-CoV-2 infection through regulation of host cell calcium dynamics

Calcium is a secondary messenger that interacts with several cellular proteins, regulates various physiological processes, and plays a role in diseases such as viral infections. Next-generation probiotics and live biotherapeutic products are linked to the regulation of intracellular calcium levels. Some viruses can manipulate calcium channels, pumps, and membrane receptors to alter calcium influx and promote virion production and release. In this study, we examined the use of bacteria for the prevention and treatment of viral diseases, such as coronavirus of 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Vaccination programs have helped reduce disease severity; however, there is still a lack of well-recognized drug regimens for the clinical management of COVID-19. SARS-CoV-2 interacts with the host cell calcium (Ca2+), manipulates proteins, and disrupts Ca2+ homeostasis. This article explores how viruses exploit, create, or exacerbate calcium imbalances, and the potential role of probiotics in mitigating viral infections by modulating calcium signaling. Pharmacological strategies have been developed to prevent viral replication and block the calcium channels that serve as viral receptors. Alternatively, probiotics may interact with cellular calcium influx, such as Lactobacillus spp. The interaction between Akkermansia muciniphila and cellular calcium homeostasis is evident. A scientific basis for using probiotics to manipulate calcium channel activity needs to be established for the treatment and prevention of viral diseases while maintaining calcium homeostasis. In this review article, we discuss how intracellular calcium signaling can affect viral replication and explore the potential therapeutic benefits of probiotics.

The Health Status of Horses Used for at Least Six Complete Cycles of Loxoscelic Antivenom Production

Antivenom production against Loxosceles venom relies on horses being immunized and bled for plasma harvest. One horse can partake in several cycles of antivenom production, which will require years of constant venom and adjuvant inoculation and bleeding. The actual impact on the health of horses that participate in several antivenom-producing cycles is unknown. Therefore, this study aimed to evaluate the general health status of horses that underwent at least six cycles of loxoscelic antivenom production. Seven crossbred horses that had partaken in six to eight complete antivenom-producing cycles were used and established as the immunized group (IG). Under the same handling and general management, eleven horses were established as the control group (CG). The horses were evaluated regarding their general clinical status and had their blood sampled, and an ECG recorded. The IG presented lower RBC and PCV, despite keeping values within inferior limits for the species. Renal function was not impaired, and liver-related enzymes were higher than those in the CG, probably due to liver exertion from immunoglobulin synthesis. ECG showed some abnormalities in the IG, such as atrioventricular block and a wandering atrial pacemaker, corroborated by an increase in CK-MB. The cardiovascular abnormalities were mainly found in the horses that participated in several antivenom-producing cycles. The overall results indicate that these horses had some impairment of their general health status. Once available, some alternative, less toxic antigens should replace the venom for immunization of horses used for antivenom production.

Analysis of NGS data from Peruvian Loxosceles laeta spider venom gland reveals toxin diversity

Accidents involving spiders from the genus Loxosceles cause medical emergencies in several countries of South America. The species Loxosceles laeta is ubiquitously present in Peru and is responsible for severe accidents in this country. To further characterize L. laeta venom components and to unveil possible variations in the Peruvian population, we provide an overview of the toxins-related transcripts present in the venom gland of Peruvian L. laeta. A dataset from a cDNA library previously sequenced by MiSeq sequencer (Illumina) was re-analyzed and the obtained data was compared with available sequences from Loxosceles toxins. Phospholipase-D represent the majority (69,28 %) of the transcripts related to venom toxins, followed by metalloproteases (20,72 %), sicaritoxins (6,03 %), serine-proteases (2,28 %), hyaluronidases (1,80 %) and Translationally Controlled Tumor Protein (TCTP) (0,56 %). New sequences of phospholipases D,sicaritoxins, hyaluronidase, TCTP and serine proteinases were described. Differences between the here-described toxin sequences and others, previously identified in venom glands from other spiders, were visualized upon sequence alignments. In addition, an in vitro hyaluronidase activity assay was also performed to complement comparisons between Peruvian and Brazilian L. laeta venom enzymatic activities, revealing a superior activity in the venom from Brazilian specimens. These new data provide a molecular basis that can help to explain the difference in toxicity among L. laeta venoms from different countries in South America.

Protective Effectiveness of an Immunization Protocol Against the Toxic Effects of Loxosceles intermedia Venom in Rabbits

Loxosceles spp. (brown spiders) bites are responsible for the development of a syndrome consisting mainly of dermonecrotic lesions, and also systemic effects. Rabbits are one of the main experimental models used for better understanding the systemic and local effects of Loxosceles venom. The aim of this study is to evaluate the toxic and protective effects of rabbits immunized with Loxosceles spp. venom. Male New Zealand rabbits were allocated as a control group (CG; n = 5) that received adjuvant (Montanide) and phosphate-buffer saline (PBS), or as venom group (VG; n = 5) that received 21 μg of Loxosceles venom using Montanide as adjuvant. After five immunization cycles, a trial with 7 μg of Loxosceles intermedia (L. intermedia) venom was performed, and dermonecrotic lesions were measured. The rabbits were then euthanized, and their organs were collected for histopathology analysis. Rabbits that had undergone Loxosceles venom immunization protocol showed minor clinical disturbances during the experimental period. The used immunization protocol protected the rabbits against the toxic effect of the Loxosceles venom because they showed minor clinical disturbances during the experimental period.

Clinical Effects of the Immunization Protocol Using Loxosceles Venom in Naïve Horses

Bites of brown spiders (Loxosceles spp.) are responsible for dermonecrotic lesions and potentially systemic envenoming that can lead to death. The only effective therapy is the use of the antivenom, usually produced in horses. However, little is known about the consequences of the systematic use of the Loxosceles venom and adjuvants and of the bleedings on antivenom-producing horses. Thus, the aim of this study was to evaluate the clinical changes in horses in their first immunization protocol for Loxosceles antivenom production. Eleven healthy horses, never immunized, were evaluated in three different periods: T0 (before immunization); T1 (after their first venom immunization); and T2 (after their first bleeding). Horses were clinically evaluated, sampled for blood, and underwent electrocardiographic (ECG) recordings. Several suppurated subcutaneous abscesses occurred due to the use of Freund’s adjuvants and thrombophlebitis due to systematic venipunctures for the bleeding procedures. ECG showed arrhythmias in few horses in T2, such as an increase in T and R waves. In summary, the immunization protocol impacted on horses’ health, especially after bleeding for antivenom procurement.

Strategies for Heterologous Expression, Synthesis, and Purification of Animal Venom Toxins

Animal venoms are complex mixtures containing peptides and proteins known as toxins, which are responsible for the deleterious effect of envenomations. Across the animal Kingdom, toxin diversity is enormous, and the ability to understand the biochemical mechanisms governing toxicity is not only relevant for the development of better envenomation therapies, but also for exploiting toxin bioactivities for therapeutic or biotechnological purposes. Most of toxinology research has relied on obtaining the toxins from crude venoms; however, some toxins are difficult to obtain because the venomous animal is endangered, does not thrive in captivity, produces only a small amount of venom, is difficult to milk, or only produces low amounts of the toxin of interest. Heterologous expression of toxins enables the production of sufficient amounts to unlock the biotechnological potential of these bioactive proteins. Moreover, heterologous expression ensures homogeneity, avoids cross-contamination with other venom components, and circumvents the use of crude venom. Heterologous expression is also not only restricted to natural toxins, but allows for the design of toxins with special properties or can take advantage of the increasing amount of transcriptomics and genomics data, enabling the expression of dormant toxin genes. The main challenge when producing toxins is obtaining properly folded proteins with a correct disulfide pattern that ensures the activity of the toxin of interest. This review presents the strategies that can be used to express toxins in bacteria, yeast, insect cells, or mammalian cells, as well as synthetic approaches that do not involve cells, such as cell-free biosynthesis and peptide synthesis. This is accompanied by an overview of the main advantages and drawbacks of these different systems for producing toxins, as well as a discussion of the biosafety considerations that need to be made when working with highly bioactive proteins.

Brown spider venom toxins: what are the functions of astacins, serine proteases, hyaluronidases, allergens, TCTP, serpins and knottins?

Accidents caused by the bites of brown spiders (Loxosceles) generate a clinical condition that often includes a threatening necrotic skin lesion near the bite site along with a remarkable inflammatory response. Systemic disorders such as hemolysis, thrombocytopenia, and acute renal failure may occur, but are much less frequent than the local damage. It is already known that phospholipases D, highly expressed toxins in Loxosceles venom, can induce most of these injuries. However, this spider venom has a great range of toxins that probably act synergistically to enhance toxicity. The other protein classes remain poorly explored due to the difficulty in obtaining sufficient amounts of them for a thorough investigation. They include astacins (metalloproteases), serine proteases, knottins, translationally controlled tumor proteins (TCTP), hyaluronidases, allergens and serpins. It has already been shown that some of them, according to their characteristics, may participate to some extent in the development of loxoscelism. In addition, all of these toxins present potential application in several areas. The present review article summarizes information regarding some functional aspects of the protein classes listed above, discusses the directions that could be taken to materialize a comprehensive investigation on each of these toxins as well as highlights the importance of exploring the full venom repertoire.

Prospective Use of Brown Spider Venom Toxins as Therapeutic and Biotechnological Inputs

Brown spider (genus Loxosceles) venoms are mainly composed of protein toxins used for predation and defense. Bites of these spiders most commonly produce a local dermonecrotic lesion with gravitational spread, edema and hemorrhage, which together are defined as cutaneous loxoscelism. Systemic loxoscelism, such as hematological abnormalities and renal injury, are less frequent but more lethal. Some Loxosceles venom toxins have already been isolated and extensively studied, such as phospholipases D (PLDs), which have been recombinantly expressed and were proven to reproduce toxic activities associated to the whole venom. PLDs have a notable potential to be engineered and converted in non-toxic antigens to produce a new generation of antivenoms or vaccines. PLDs also can serve as tools to discover inhibitors to be used as therapeutic agents. Other Loxosceles toxins have been identified and functionally characterized, such as hyaluronidases, allergen factor, serpin, TCTP and knottins (ICK peptides). All these toxins were produced as recombinant molecules and are biologically active molecules that can be used as tools for the potential development of chemical candidates to tackle many medical and biological threats, acting, for instance, as antitumoral, insecticides, analgesic, antigens for allergy tests and biochemical reagents for cell studies. In addition, these recombinant toxins may be useful to develop a rational therapy for loxoscelism. This review summarizes the main candidates for the development of drugs and biotechnological inputs that have been described in Brown spider venoms.

Description of a serpin toxin in Loxosceles (Brown spider) venoms: Cloning, expression in baculovirus-infected insect cells and functional characterization

Several classes of toxins are present in the venom of Brown spiders (Loxosceles genus), some of them are highly expressed and others are less expressed. In this work, we aimed to clone the sequence of a little expressed novel toxin from Loxosceles venom identified as a serine protease inhibitor (serpin), as well as to express and characterize its biochemical and biological properties. It was named LSPILT, derived from Loxoscelesserine protease inhibitor-like toxin. Multiple alignment analysis revealed high identity between LSPILT and other serpin molecules from spiders and crab. LSPILT was produced in baculovirus-infected insect cells, resulting in a 46-kDa protein fused to a His-tag. Immunological assays showed epitopes in LSPILT that resemble native venom toxins of Loxosceles spiders. The inhibitory activity of LSPILT on trypsin was found both by reverse zymography and fluorescent gelatin-degradation assay. Additionally, LSPILT inhibited the complement-dependent lysis of Trypanosoma cruzi epimastigotes, reduced thrombin-dependent clotting and suppressed B16-F10 melanoma cells migration. Results described herein prove the existence of conserved serpin-like toxins in Loxosceles venoms. The availability of a recombinant serpin enabled the determination of its biological and biochemical properties and indicates potential applications in future studies regarding the pathophysiology of the envenoming or for biotechnological purposes.