SEQUENCE SLIDER: integration of structural and genetic data to characterize isoforms from natural sources.

Proteins isolated from natural sources can be composed of a mixture of isoforms with similar physicochemical properties that coexist in the final steps of purification. Yet, even where unverified, the assumed sequence is enforced throughout the structural studies. Herein, we propose a novel perspective to address the usually neglected sequence heterogeneity of natural products by integrating biophysical, genetic and structural data in our program SEQUENCE SLIDER. The aim is to assess the evidence supporting chemical composition in structure determination. Locally, we interrogate the experimental map to establish which side chains are supported by the structural data, and the genetic information relating sequence conservation is integrated into this statistic. Hence, we build a constrained peptide database, containing most probable sequences to interpret mass spectrometry data (MS). In parallel, we perform MS de novo sequencing with genomic-based algorithms to detect point mutations. We calibrated SLIDER with Gallus gallus lysozyme, whose sequence is unequivocally established and numerous natural isoforms are reported. We used SLIDER to characterize a metalloproteinase and a phospholipase A2-like protein from the venom of Bothrops moojeni and a crotoxin from Crotalus durissus collilineatus. This integrated approach offers a more realistic structural descriptor to characterize macromolecules isolated from natural sources.

Structural evidence for a fatty acid-independent myotoxic mechanism for a phospholipase A2-like toxin.

The myotoxic mechanism for PLA2-like toxins has been proposed recently to be initiated by an allosteric change induced by a fatty acid binding to the protein, leading to the alignment of the membrane docking site (MDoS) and membrane disrupting site (MDiS). Previous structural studies performed by us demonstrated that MjTX-II, a PLA2-like toxin isolated from Bothrops moojeni, presents a different mode of ligand-interaction caused by natural amino acid substitutions and an insertion. Herein, we present four crystal structures of MjTX-II, in its apo state and complexed with fatty acids of different lengths. Analyses of these structures revealed slightly different oligomeric conformations but with both MDoSs in an arrangement that resembles an active-state PLA2-like structure. To explore the structural transitions between apo protein and fatty-acid complexes, we performed Normal Mode Molecular Dynamics simulations, revealing that oligomeric conformations of MjTX-II/fatty acid complexes may be reached in solution by the apo structure. Similar simulations with typical PLA2-like structures demonstrated that this transition is not possible without the presence of fatty acids. Thus, we hypothesize that MjTX-II does not require fatty acids to be active, although these ligands may eventually help in its stabilization by the formation of hydrogen bonds. Therefore, these results complement previous findings for MjTX-II and help us understand its particular ligand-binding properties and, more importantly, its particular mechanism of action, with a possible impact on the design of structure-based inhibitors for PLA2-like toxins in general.

Functional and structural studies of a Phospholipase A2-like protein complexed to zinc ions: Insights on its myotoxicity and inhibition mechanism.

BACKGROUND: One of the main challenges in snakebite envenomation treatment is the development of stable, versatile and efficient anti-venom therapies. Local myotoxicity in accidents involving snakes from the Bothrops genus is still a consequence of serum therapy inefficient neutralization that may lead to permanent sequelae in their victims. One of the classes of toxins that participate in muscle necrosis is the PLA2-like proteins. The aim of this work was to investigate the role of zinc ions in the inhibition of PLA2-like proteins and to advance the current knowledge of their action mechanism. METHODS: Myographic and electrophysiological techniques were used to evaluate the inhibitory effect of zinc ions, isothermal titration calorimetry assays were used to measure the affinity between zinc ions and the toxin and X-ray crystallography was used to reveal details of this interaction. RESULTS: We demonstrated that zinc ions can effectively inhibit the toxin by the interaction with two different sites, which are related to two different mechanism of inhibition: preventing membrane disruption and impairing the toxin state transition. Furthermore, structural study presented here included an additional step in the current myotoxic mechanism improving the comprehension of the allosteric transition that PLA2-like proteins undergo to exert their function. CONCLUSIONS: Our findings show that zinc ions are inhibitors of PLA2-like proteins and suggest two different mechanisms of inhibition for these ions. GENERAL SIGNIFICANCE: Zinc is a new candidate that can assist in anti-venom treatments and can promote the design of new and even more accurate structure-based inhibitors for PLA2-like proteins.

A structure-based proposal for a comprehensive myotoxic mechanism of phospholipase A2-like proteins from viperid snake venoms.

Envenomation via snakebites is an important public health problem in many tropical and subtropical countries that, in addition to mortality, can result in permanent sequelae as a consequence of local tissue damage, which represents a major challenge to antivenom therapy. Venom phospholipases A2 (PLA2s) and PLA2-like proteins play a leading role in the complex pathogenesis of skeletal muscle necrosis, nevertheless their precise mechanism of action is only partially understood. Recently, detailed structural information has been obtained for more than twenty different members of the PLA2-like myotoxin subfamily. In this review, we integrate the available structural, biochemical and functional data on these toxins and present a comprehensive hypothesis for their myotoxic mechanism. This process involves an allosteric transition and the participation of two independent interaction sites for docking and disruption of the target membrane, respectively, leading to a five-step mechanism of action. Furthermore, recent functional and structural studies of these toxins complexed with ligands reveal diverse neutralization mechanisms that can be classified into at least three different groups. Therefore, the data summarized here for the PLA2-like myotoxins could provide a useful molecular basis for the search for novel neutralizing strategies to improve the treatment of envenomation by viperid snakes.

ARCIMBOLDO_LITE: single-workstation implementation and use.

ARCIMBOLDO solves the phase problem at resolutions of around 2 Šor better through massive combination of small fragments and density modification. For complex structures, this imposes a need for a powerful grid where calculations can be distributed, but for structures with up to 200 amino acids in the asymmetric unit a single workstation may suffice. The use and performance of the single-workstation implementation, ARCIMBOLDO_LITE, on a pool of test structures with 40-120 amino acids and resolutions between 0.54 and 2.2 Šis described. Inbuilt polyalanine helices and iron cofactors are used as search fragments. ARCIMBOLDO_BORGES can also run on a single workstation to solve structures in this test set using precomputed libraries of local folds. The results of this study have been incorporated into an automated, resolution- and hardware-dependent parameterization. ARCIMBOLDO has been thoroughly rewritten and three binaries are now available: ARCIMBOLDO_LITE, ARCIMBOLDO_SHREDDER and ARCIMBOLDO_BORGES. The programs and libraries can be downloaded from http://chango.ibmb.csic.es/ARCIMBOLDO_LITE.

Structural bases for a complete myotoxic mechanism: crystal structures of two non-catalytic phospholipases A2-like from Bothrops brazili venom.

Bothrops brazili is a snake found in the forests of the Amazonian region whose commercial therapeutic anti-bothropic serum has low efficacy for local myotoxic effects, resulting in an important public health problem in this area. Catalytically inactive phospholipases A2-like (Lys49-PLA2s) are among the main components from Bothrops genus venoms and are capable of causing drastic myonecrosis. Several studies have shown that the C-terminal region of these toxins, which includes a variable combination of positively charged and hydrophobic residues, is responsible for their activity. In this work we describe the crystal structures of two Lys49-PLA2s (BbTX-II and MTX-II) from B. brazili venom and a comprehensive structural comparison with several Lys49-PLA2s. Based on these results, two independent sites of interaction were identified between protein and membrane which leads to the proposition of a new myotoxic mechanism for bothropic Lys49-PLA2s composed of five different steps. This proposition is able to fully explain the action of these toxins and may be useful to develop efficient inhibitors to complement the conventional antivenom administration.

Structural studies with crotoxin B from Crotalus durissus collilineatus venom suggest a heterodimeric assembly formed by two new isoforms.

In accidents involving Crotalus snakes, the crotoxin complex (CTX) plays lethal action due to its neurotoxic activity. On the other hand, CTX have potential biotechnological application due to its anti-tumoral, anti-inflammatory, antimicrobial, analgesic and immunomodulatory properties. CTX is a heterodimer composed of Crotoxin A (CA or crotapotin), the acidic nontoxic and non-enzymatic component and; Crotoxin B (CB), a basic, toxic and catalytic PLA2. Currently, there are two classes of CTX isoforms, whose differences in their biological activities have been attributed to features presented in CB isoforms. Here, we present the crystal structure of CB isolated from the Crotalus durissus collilineatus venom. It amino acid sequence was assigned using the SEQUENCE SLIDER software, which revealed that the crystal structure is a heterodimer composed of two new CB isoforms (colCB-A and colCB-B). Bioinformatic and biophysical analyses showed that the toxin forms a tetrameric assembly in solution similar to CB from Crotalus durissus terrificus venom, despite some differences observed at the dimeric interface. By the previously proposed classification, the colCB-B presents features of the class I isoforms while colCB-A cannot be classified into classes I and II based on its amino acid sequence. Due to similar features observed for other CB isoforms found in the NCBI database and the results obtained for colCB-A, we suggest that there are more than two classes of CTX and CB isoforms in crotalic venoms.

In silico evaluation of pharmacokinetics properties of withanolides and simulation of their biological activities against Alzheimer's disease.

The withanolides are naturally occurring steroidal lactones found mainly in plants of the Solanaceae family. The subtribe Withaninae includes species like Withania sominifera, which are a source of many bioactive withanolides. In this work, we selected and evaluate the ADMET-related properties of 91 withanolides found in species of the subtribe Withaninae computationally, to predict the relationship between their structures and their pharmacokinetic profiles. We also evaluated the interaction of these withanolides with known targets of Alzheimer's disease (AD) through molecular docking and molecular dynamics. Withanolides presented favorable pharmacokinetic properties, like high gastrointestinal absorption, lipophilicity (logP ≤ 5), good distribution and excretion parameters, and a favorable toxicity profile. The specie Withania aristata stood out as an interesting source of the promising withanolides classified as 5-ene with 16-ene or 17-ene. These withanolides presented a favourable pharmacokinetic profile and were also highlighted as the best candidates for inhibition of AD-related targets. Our results also suggest that withanolides are likely to act as cholinesterase inhibitors by interacting with the catalytic pocket in an energy favorable and stable way.Communicated by Ramaswamy H. Sarma.

Interactions of the male contraceptive target EPPIN with semenogelin-1 and small organic ligands.

Novel male contraceptives will promote gender equality in sharing contraceptive responsibility. The sperm-associated protein epididymal protease inhibitor (EPPIN) is a promising target for non-hormonal male contraception. EPPIN interacts with the semen coagulum protein semenogelin-1 (SEMG1) on the sperm surface, leading to transient inhibition of sperm motility after ejaculation. Small organic molecules targeting EPPIN's SEMG1-binding are under development as male contraceptives. Here, we combined computational approaches to uncover key aspects underlying EPPIN binding to SEMG1 and small organic ligands. We generated a human EPPIN model showing a typical arrangement of the WFDC (Whey-acid four disulfide core)-type and Kunitz-type domains, connected by a hinge region. Determining the EPPIN model's intrinsic motion by molecular dynamics simulations and normal mode analysis revealed a conformation, presenting a binding pocket that accommodates SEMG1Glu229-Gln247, EP055, and EP012. EPPIN's residues Phe63 and Lys68 (WFDC domain), Asp71 (hinge region), and Asn113, Asn114, and Asn115 (Kunitz domain) were identified as hot spots for SEMG1, EP055, and EP012 binding. Moreover, hydrophobic and hydrophilic residues in the WFDC and Kunitz domains allow plasma membrane anchoring, orienting the EPPIN binding pocket to the solvent. Targeting EPPIN's essential residues for its biomolecular interactions may improve the rational design of EPPIN ligands as spermiostatic compounds.

Structural and functional studies of a snake venom phospholipase A2-like protein complexed to an inhibitor from Tabernaemontana catharinensis.

Snake envenomation is an ongoing global health problem and tropical neglected disease that afflicts millions of people each year. The only specific treatment, antivenom, has several limitations that affects its proper distribution to the victims and its efficacy against local effects, such as myonecrosis. The main responsible for this consequence are the phospholipases A2 (PLA2) and PLA2-like proteins, such as BthTX-I from Bothrops jararacussu. Folk medicine resorts to plants such as Tabernaemontana catharinensis to palliate these and other snakebite effects. Here, we evaluated the effect of its root bark extract and one of its isolated compounds, 12-methoxy-4-methyl-voachalotine (MMV), against the in vitro paralysis and muscle damage induced by BthTX-I. Secondary and quaternary structures of BthTX-I were not modified by the interaction with MMV. Instead, this compound interacted in an unprecedented way with the region inside the toxin hydrophobic channel and promoted a structural change in Val31, loop 58-71 and Membrane Disruption Site. Thus, we hypothesize that MMV inhibits PLA2-like proteins by preventing entrance of fatty acid into the hydrophobic channel. These data may explain the traditional use of T. catharinensis extract and confirm MMV as a promising candidate to complement antivenom or a structural guide to develop more effective inhibitors.

Fragment-Based Ab Initio Phasing of Peptidic Nanocrystals by MicroED.

Electron diffraction (MicroED/3DED) can render the three-dimensional atomic structures of molecules from previously unamenable samples. The approach has been particularly transformative for peptidic structures, where MicroED has revealed novel structures of naturally occurring peptides, synthetic protein fragments, and peptide-based natural products. Despite its transformative potential, MicroED is beholden to the crystallographic phase problem, which challenges its de novo determination of structures. ARCIMBOLDO, an automated, fragment-based approach to structure determination, eliminates the need for atomic resolution, instead enforcing stereochemical constraints through libraries of small model fragments, and discerning congruent motifs in solution space to ensure validation. This approach expands the reach of MicroED to presently inaccessible peptide structures including fragments of human amyloids, and yeast and mammalian prions. For electron diffraction, fragment-based phasing portends a more general phasing solution with limited model bias for a wider set of chemical structures.

The CCP4 suite: integrative software for macromolecular crystallography.

The Collaborative Computational Project No. 4 (CCP4) is a UK-led international collective with a mission to develop, test, distribute and promote software for macromolecular crystallography. The CCP4 suite is a multiplatform collection of programs brought together by familiar execution routines, a set of common libraries and graphical interfaces. The CCP4 suite has experienced several considerable changes since its last reference article, involving new infrastructure, original programs and graphical interfaces. This article, which is intended as a general literature citation for the use of the CCP4 software suite in structure determination, will guide the reader through such transformations, offering a general overview of the new features and outlining future developments. As such, it aims to highlight the individual programs that comprise the suite and to provide the latest references to them for perusal by crystallographers around the world.

Structural, functional, and bioinformatics studies reveal a new snake venom homologue phospholipase A2 class.

Phospholipases A2 (PLA2s) are enzymes responsible for membrane disruption through Ca(2+) -dependent hydrolysis of phospholipids. Lys49-PLA2s are well-characterized homologue PLA2s that do not show catalytic activity but can exert a pronounced local myotoxic effect. These homologue PLA2s were first believed to present residual catalytic activity but experiments with a recombinant toxin show they are incapable of catalysis. Herein, we present a new homologue Asp49-PLA2 (BthTX-II) that is also able to exert muscle damage. This toxin was isolated in 1992 and characterized as presenting very low catalytic activity. Interestingly, this myotoxic homologue Asp49-PLA2 conserves all the residues responsible for Ca(2+) coordination and of the catalytic network, features thought to be fundamental for PLA2 enzymatic activity. Previous crystallographic studies of apo BthTX-II suggested this toxin could be catalytically inactive since a distortion in the calcium binding loop was observed. In this article, we show BthTX-II is not catalytic based on an in vitro cell viability assay and time-lapse experiments on C2C12 myotube cell cultures, X-ray crystallography and phylogenetic studies. Cell culture experiments show that BthTX-II is devoid of catalytic activity, as already observed for Lys49-PLA2s. Crystallographic studies of the complex BthTX-II/Ca(2+) show that the distortion of the calcium binding loop is still present and impairs ion coordination even though Ca(2+) are found interacting with other regions of the protein. Phylogenetic studies demonstrate that BthTX-II is more phylogenetically related to Lys49-PLA2s than to other Asp49-PLA2s, thus allowing Crotalinae subfamily PLA2s to be classified into two main branches: a catalytic and a myotoxic one.

The synthetic varespladib molecule is a multi-functional inhibitor for PLA2 and PLA2-like ophidic toxins.

BACKGROUND: The treatment for snakebites is early administration of antivenom, which can be highly effective in inhibiting the systemic effects of snake venoms, but is less effective in the treatment of extra-circulatory and local effects. To complement standard-of-care treatments such as antibody-based antivenoms, natural and synthetic small molecules have been proposed for the inhibition of key venom components such as phospholipase A2 (PLA2) and PLA2-like toxins. Varespladib (compound LY315920) is a synthetic molecule developed and clinically tested aiming to block inflammatory cascades of several diseases associated with high PLA2s. Recent studies have demonstrated this molecule is able to potently inhibit snake venom catalytic PLA2 and PLA2-like toxins. METHODS: In vivo and in vitro techniques were used to evaluate the inhibitory effect of varespladib against MjTX-I. X-ray crystallography was used to reveal details of the interaction between these molecules. A new methodology that combines crystallography, mass spectroscopy and phylogenetic data was used to review its primary sequence. RESULTS: Varespladib was able to inhibit the myotoxic and cytotoxic effects of MjTX-I. Structural analysis revealed a particular inhibitory mechanism of MjTX-I when compared to other PLA2-like myotoxin, presenting an oligomeric-independent function. CONCLUSION: Results suggest the effectiveness of varespladib for the inhibition of MjTX-I, in similarity with other PLA2 and PLA2-like toxins. GENERAL SIGNIFICANCE: Varespladib appears to be a promissory molecule in the treatment of local effects led by PLA2 and PLA2-like toxins (oligomeric dependent and independent), indicating that this is a multifunctional or broadly specific inhibitor for different toxins within this superfamily.

BthTX-II from Bothrops jararacussu venom has variants with different oligomeric assemblies: An example of snake venom phospholipases A2 versatility.

Phospholipases A2 (PLA2s) are found in almost every venomous snake family. In snakebites, some PLA2s can quickly cause local myonecrosis, which may lead to permanent sequelae if antivenom is administered belatedly. They hydrolyse phospholipids in membranes through a catalytic calcium ions-dependent mechanism. BthTX-II is a basic PLA2 and the second major component in the venom of Bothrops jararacussu. Herein, using the software SEQUENCE SLIDER, which integrates crystallographic, mass spectrometry and genetic data, we characterized the primary, tertiary and quaternary structure of two BthTX-II variants (called a and b), which diverge in 7 residues. Crystallographic structure BthTX-IIa is in a Tense-state with its distorted calcium binding loop buried in the dimer interface, contrarily, the novel BthTX-IIb structure is a monomer in a Relax-state with a fatty acid in the hydrophobic channel. Structural data in solution reveals that both variants are monomeric in neutral physiological conditions and mostly dimeric in an acidic environment, being catalytic active in both situations. Therefore, we propose two myotoxic mechanisms for BthTX-II, a catalytic one associated with the monomeric assembly, whereas the other has a calcium independent activity related to its C-terminal region, adopting a dimeric conformation similar to PLA2-like proteins.

ALEPH: a network-oriented approach for the generation of fragment-based libraries and for structure interpretation.

The analysis of large structural databases reveals general features and relationships among proteins, providing useful insight. A different approach is required to characterize ubiquitous secondary-structure elements, where flexibility is essential in order to capture small local differences. The ALEPH software is optimized for the analysis and the extraction of small protein folds by relying on their geometry rather than on their sequence. The annotation of the structural variability of a given fold provides valuable information for fragment-based molecular-replacement methods, in which testing alternative model hypotheses can succeed in solving difficult structures when no homology models are available or are successful. ARCIMBOLDO_BORGES combines the use of composite secondary-structure elements as a search model with density modification and tracing to reveal the rest of the structure when both steps are successful. This phasing method relies on general fold libraries describing variations around a given pattern of ß-sheets and helices extracted using ALEPH. The program introduces characteristic vectors defined from the main-chain atoms as a way to describe the geometrical properties of the structure. ALEPH encodes structural properties in a graph network, the exploration of which allows secondary-structure annotation, decomposition of a structure into small compact folds, generation of libraries of models representing a variation of a given fold and finally superposition of these folds onto a target structure. These functions are available through a graphical interface designed to interactively show the results of structure manipulation, annotation, fold decomposition, clustering and library generation. ALEPH can produce pictures of the graphs, structures and folds for publication purposes.

Biochemical, pharmacological and structural characterization of BmooMP-I, a new P-I metalloproteinase from Bothrops moojeni venom.

Snakebite envenoming is still a worrying health problem in countries under development, being recognized as a neglected disease by the World Health Organization. In Latin America, snakes from the genus Bothrops are widely spread and in Brazil, the Bothrops moojeni is a medically important species. The pharmacological effects of bothropic snake venoms include pain, blisters, bleeding, necrosis and even amputation of the affected limb. Snake venom metalloproteinases are enzymes abundantly present in venom from Bothrops snakes. These enzymes can cause hemorrhagic effects and lead to myonecrosis due to ischemia. Here, we present BmooMP-I, a new P-I class of metalloproteinase (this class only has the catalytic domain in the mature form) isolated from B. moojeni venom. This protein is able to express fibrinogenolytic and gelatinase activities, which play important roles in the prey's immobilization and digestion, and also induces weak hemorrhagic effect. The primary sequence assignment was done by a novel method, SEQUENCE SLIDER, which combines crystallographic, bioinformatics and mass spectrometry data. The high-resolution crystal structure reveals the monomeric assembly and the conserved metal binding site H141ExxH145xxG148xxH151 with the natural substitution Gly148Asp that does not interfere in the zinc coordination. The presence of a structural calcium ion on the surface of the protein, which can play an important role in the stabilization of hemorrhagic toxins, was observed in the BmooMP-I structure. Due to the relevant local and systemic effects of snake venom metalloproteinases, studies involving these proteins help to better understand the pathological effects of snakebite envenoming.

Fragment-based determination of a proteinase K structure from MicroED data using ARCIMBOLDO_SHREDDER.

Structure determination of novel biological macromolecules by X-ray crystallography can be facilitated by the use of small structural fragments, some of only a few residues in length, as effective search models for molecular replacement to overcome the phase problem. Independence from the need for a complete pre-existing model with sequence similarity to the crystallized molecule is the primary appeal of ARCIMBOLDO, a suite of programs which employs this ab initio algorithm for phase determination. Here, the use of ARCIMBOLDO is investigated to overcome the phase problem with the electron cryomicroscopy (cryoEM) method known as microcrystal electron diffraction (MicroED). The results support the use of the ARCIMBOLDO_SHREDDER pipeline to provide phasing solutions for a structure of proteinase K from 1.6 Šresolution data using model fragments derived from the structures of proteins sharing a sequence identity of as low as 20%. ARCIMBOLDO_SHREDDER identified the most accurate polyalanine fragments from a set of distantly related sequence homologues. Alternatively, such templates were extracted in spherical volumes and given internal degrees of freedom to refine towards the target structure. Both modes relied on the rotation function in Phaser to identify or refine fragment models and its translation function to place them. Model completion from the placed fragments proceeded through phase combination of partial solutions and/or density modification and main-chain autotracing using SHELXE. The combined set of fragments was sufficient to arrive at a solution that resembled that determined by conventional molecular replacement using the known target structure as a search model. This approach obviates the need for a single, complete and highly accurate search model when phasing MicroED data, and permits the evaluation of large fragment libraries for this purpose.

Structural basis of phospholipase A2-like myotoxin inhibition by chicoric acid, a novel potent inhibitor of ophidian toxins.

BACKGROUND: Specific compounds found in vegetal species have been demonstrated to be efficient inhibitors of snake toxins, such as phospholipase A2-like (PLA2-like) proteins. These particular proteins, present in several species of vipers (Viperidae), induce a severe local myotoxic effect in prey and human victims, and this effect is often not efficiently neutralized by the regular serum therapy. PLA2-like proteins have been functionally and structurally studied since the early 1990s; however, a comprehensive molecular mechanism was proposed only recently. METHODS: Myographic and histological techniques were used to evaluate the inhibitory effect of chicoric acid (CA) against BthTX-I myotoxin. Isothermal titration calorimetry assays were used to measure the affinity between the inhibitor and the toxin. X-ray crystallography was used to reveal details of this interaction. RESULTS: CA prevented the blockade of indirectly evoked muscle contraction and inhibited muscle damage induced by BthTX-I. The inhibitor binds to the toxin with the highest affinity measured for a natural compound in calorimetric assays. The crystal structure and molecular dynamics simulations demonstrated that CA binds at the entrance of the hydrophobic channel of the toxin and binds to one of the clusters that participates in membrane disruption. CONCLUSIONS: CA prevents the myotoxic activity of the toxin, preventing its activation by simultaneous binding with two critical regions. GENERAL SIGNIFICANCE: CA is a potential myotoxic inhibitor to other PLA2-like proteins and a possible candidate to complement serum therapy.

Fetal protection against continual exposure to bovine viral diarrhea virus following administration of a vaccine containing an inactivated bovine viral diarrhea virus fraction to cattle.

OBJECTIVE: To evaluate the efficacy of a commercially available killed bovine viral diarrhea virus (BVDV) vaccine to protect against fetal infection in pregnant cattle continually exposed to cattle persistently infected with the BVDV. ANIMALS: 60 crossbred beef heifers and 4 cows persistently infected with BVDV. PROCEDURES: Beef heifers were allocated to 2 groups. One group was vaccinated twice (21-day interval between the initial and booster vaccinations) with a commercially available vaccine against BVDV, and the other group served as nonvaccinated control cattle. Estrus was induced, and the heifers were bred. Pregnancy was confirmed by transrectal palpation. Four cows persistently infected with BVDV were housed with 30 pregnant heifers (15 each from the vaccinated and nonvaccinated groups) from day 52 to 150 of gestation. Fetuses were then harvested by cesarean section and tested for evidence of BVDV infection. RESULTS: 1 control heifer aborted after introduction of the persistently infected cows. Bovine viral diarrhea virus was isolated from 14 of 14 fetuses obtained via cesarean section from control heifers but from only 4 of 15 fetuses obtained via cesarean section from vaccinated heifers; these proportions differed significantly. CONCLUSIONS AND CLINICAL RELEVANCE: A commercially available multivalent vaccine containing an inactivated BVDV fraction significantly reduced the risk of fetal infection with BVDV in heifers continually exposed to cattle persistently infected with BVDV. However, not all vaccinated cattle were protected, which emphasizes the need for biosecurity measures and elimination of cattle persistently infected with BVDV in addition to vaccination within a herd.