Immunoglobulins of camel (Camelus dromedarius) colostrum

The mycoplasma surface proteins MIB and MIP promote the dissociation of the antibody-antigen interaction

Mycoplasma immunoglobulin binding (MIB) and mycoplasma immunoglobulin protease (MIP) are surface proteins found in the majority of mycoplasma species, acting sequentially to capture antibodies and cleave off their V_H domains. Cryo-electron microscopy structures show how MIB and MIP bind to a Fab fragment in a "hug of death" mechanism. As a result, the orientation of the V_L and V_H domains is twisted out of alignment, disrupting the antigen binding site. We also show that MIB-MIP has the ability to promote the dissociation of the antibody-antigen complex. This system is functional in cells and protects mycoplasmas from antibody-mediated agglutination. These results highlight the key role of the MIB-MIP system in immunity evasion by mycoplasmas through an unprecedented mechanism, and open exciting perspectives to use these proteins as potential tools in the antibody field.

Recent Advances in Camel Immunology

Camels are domesticated animals that are highly adapted to the extreme desert ecosystem with relatively higher resistance to a wide range of pathogens compared to many other species from the same geographical region. Recently, there has been increased interest in the field of camel immunology. As the progress in the analysis of camel immunoglobulins has previously been covered in many recent reviews, this review intends to summarize published findings related to camel cellular immunology with a focus on the phenotype and functionality of camel leukocyte subpopulations. The review also describes the impact of different physiological (age and pregnancy) and pathological (e.g. infection) conditions on camel immune cells. Despite the progress achieved in the field of camel immunology, there are gaps in our complete understanding of the camel immune system. Questions remain regarding innate recognition mechanisms, the functional characterization of antigen-presenting cells, and the characterization of camel NK and cytotoxic T cells.

Investigation of total immunoglobulin G concentration, heavy chain antibody levels, and neutrophil to lymphocyte ratio in female camels and their newborn calves

Camels belong to a group of animals, where the structure of placenta does not allow intrauterine transfer of maternal immunoglobulins to the fetus and maternal immunity is exclusively transferred by colostrum to the newborn calf. There are few studies on the passive transfer of maternal immunity in the dromedary camel. This study determined total immunoglobulin G concentration, heavy chain antibody (HCAbs) levels, and neutrophils to lymphocytes ratio (NLR) in female camels and their newborn calves. For this, samples were collected from nine she-camels (blood and colostrum) and their calves (blood). IgG concentration and HCAb level were determined in mother serum and colostrum as well as in calf serum using ELISA. The NLR was calculated after the estimation of relative fractions of neutrophils and lymphocytes in collected blood samples using a blood cell analyzer. Both IgG and HCAbs were higher concentrated in camel colostrum than in mother serum. At parturition and before the first colostrum intake, calf serum did not contain any measurable concentration of IgG and only low levels of HCAbs. After colostrum consumption, a rise in IgG and HCAb levels was observed in calf serum. For total IgG, a minimum was reached on day 30 postnatum. While a significant increase in IgG concentration was seen on day 60 postnatum, no significant rise was measured in HCAbs at that age. Only post-colostrum IgG levels in calf serum correlated positively with IgG levels in mother colostrum. Directly after birth, newborn calves showed significantly higher NLR than their mothers. This indicates a pro-inflammatory nature of the calf immune response. The decrease of the NLR on day 60 postnatum may argue for the maturation of the calf immune response at this age.

Camel whey protein protects lymphocytes from apoptosis via the PI3K–AKT, NF-κB, ATF-3, and HSP-70 signaling pathways in heat-stressed male mice

Heat stress (HS) is an environmental factor that depresses the immune systems that mediate dysfunctional immune cells. Camel whey protein (CWP) can scavenge free radicals and enhance immunity. This study investigated the impact of dietary supplementation with CWP on immune dysfunction induced by exposure to HS. Male mice (n = 45) were distributed among 3 groups: control group; HS group; and HS mice that were orally administered CWP (HS + CWP group). The HS group exhibited elevated levels of reactive oxygen species (ROS) and pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, tumor necrosis factor-α) as well as a significant reduction in the IL-2 and IL-4 levels. Exposure to HS resulted in impaired phosphorylation of AKT and IκB-α (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha); increased expression of activating transcription factor 3 (ATF-3) and 70 kDa heat shock proteins (HSP70); and aberrant distribution of CD3+ T cells and CD20+ B cells in the thymus and spleen. Interestingly, HS mice treated with CWP presented significantly restored levels of reactive oxygen species and pro-inflammatory cytokines near the levels observed in the control mice. Furthermore, supplementation of HS mice with CWP enhanced the phosphorylation of AKT and IκB-α; attenuated the expression of ATF-3, HSP70, and HSP90; and improved T and B cell distributions in the thymus and spleen. Our findings reveal a potential immunomodulatory effect of CWP in attenuating immune dysfunction induced by exposure to thermal stress.

Simple Protocol for immunoglobulin G Purification from Camel “Camelus dromedarius” Serum

The present study aimed to describe and standardize a simple and efficient protocol for purification of camel IgG from serum, which can be applied for Camilidae antibody production in research laboratories, the preindustrial stage. Camel serum IgG was separated with caprylic acid and ammonium sulfate, then the effect of four variables studied: caprylic acid concentration, pH, stirring time, and stirring intensity. Camel IgG prepared by standardized caprylic acid fractionation method for camel serum was compared with commercial anti-sera products. Camel IgG purification from undiluted sera using caprylic acid at concentration of 8% v/v gave the best results. Purification at different pH values using caprylic acid at 8% v/v revealed that pH 5.5 was optimal. Investigating purification at different stirring time intervals using 8% v/v caprylic acid at pH 5.5 demonstrated that stirring for 90 min gave the optimum results. Finally, studying purification at different stirring intensities using 8% v/v caprylic acid at pH 5.5 for 90 min, the best stirring intensity was at 450 rpm. Overall, the results suggest that caprylic acid purification of camel serum IgG is more effective and safe than ammonium sulfate method in simplicity, purity, and lower non-IgG proteins in the final preparation with lower protein aggregates.

Preparation of goat and rabbit anti-camel immunoglobulin G whole molecule labeled with horseradish peroxidase

Aim:

As the labeled anti-camel immunoglobulins (Igs) with enzymes for enzyme-linked immunosorbent assay (ELISA) are unavailable in the Egyptian market, the present investigation was directed for developing local labeled anti-camel IgG with horseradish peroxidase (HRP) to save hard curacy.

Materials and Methods:

For purification of camel IgG whole molecule, camel sera was preliminary precipitated with 50% saturated ammonium sulfate and dialyzed against 15 mM phosphate-buffered saline pH 7.2 then concentrated. This preparation was further purified by protein A sepharose affinity column chromatography. The purity of the eluted camel IgG was tested by sodium dodecyl sulfate polyacrylamide gel electrophoresi. Anti-camel IgG was prepared by immunization of goats and rabbits separately, with purified camel IgG. The anti-camel IgG was purified by protein A sepharose affinity column chromatography. Whole molecule anti-camel IgG was conjugated with HRP using glutraldehyde based assay. Sensitivity and specificity of prepared conjugated secondary antibodies were detected using positive and negative camel serum samples reacted with different antigens in ELISA, respectively. The potency of prepared conjugated antibodies was evaluated compared with protein A HRP. The stability of the conjugate at −20°C during 1 year was assessed by ELISA.

Results:

The electrophoretic profile of camel IgG showed four bands of molecular weight 63, 52, 40 and 33 kDa. The recorded sensitivity and specificity of the product are 100%. Its potency is also 100% compared to 58-75% of commercial protein A HRP. The conjugates are stable for 1 year at −20°C as proved by ELISA.

Conclusion:

Collectively, this study introduces goat and rabbit anti-camel IgG whole molecules with simple, inexpensive method, with 100% sensitivity, 100% specificity and stability up to 1 year at −20°C. The important facet of the current study is saving hard curacy. Future investigations are necessary for preparation of IgG subclasses.

Passive transfer of maternal immunity in the dromedary (Camelus dromedarius), involvement of heavy chain antibodies

In many mammalian species, newborns are agammaglobulinemic; thus, colostrum and milk are the main sources of early protective antibodies. These antibodies are produced in the mother's serum and transferred to mammalian glands a few days before parturition. Here, we have studied the transfer of immunity from a she-camel immunized with human serum albumin (HSA) to her calf via colostrum and milk. Our results show that HSA-specific antibodies are produced in the mother's serum and are subsequently transferred to her colostrum. These specific antibodies are then transferred by suckling to the calf. The calf serum did not contain HSA-reactive antibodies at parturition and before the first feed, after suckling, a rise in reactivity was observed peaking at 24 h postpartum. The involvement of heavy chain antibodies (HCAbs) in the process of immunity transfer was also examined, and it was found that they were also transferred from the colostrum to the calf serum like conventional antibodies.

Antibody repertoire development in camelids

The humoral immune response of the Camelidae is unique as these animals are the only known mammals that seem to possess functional homodimeric heavy-chain antibodies besides the classical heteromeric antibodies composed of heavy (H) and light (L) chains. By definition, the heavy-chain antibodies lack the L-chain, and it was noticed that their H-chain is devoid of the typical first constant domain (CH1) and contains a dedicated variable domain, referred to as VHH. The VHH exon is assembled from separate V-D-J gene segments. The recombined VHH region is subjected to somatic hypermutations; however, the timing and actual mechanism of the class switch from mu to the dedicated gamma-isotype remains elusive. Interestingly, antigen-specific VHHs are easily retrieved after panning of a phage-displayed rearranged V-gene pool cloned from an immunised camelid. These single-domain antigen binding entities possess a number of biophysical properties that offer particular advantages in various medical and biotechnological applications.

Cloning and characterization of the dromedary (Camelus dromedarius) neonatal Fc receptor (drFcRn)

The full length cDNA of the dromedary neonatal Fc receptor (drFcRn) alpha chain was isolated and found that it is similar to the neonatal Fc receptor (FcRn) of other species with a high overall similarity to ruminant FcRn alpha chains. The drFcRn/Fc contact residues are highly conserved and predicted to bind both conventional (IgG1) and heavy chain (IgG2a, IgG3) antibodies. Using immunohistochemistry, we detected its expression in the hepatocytes and in epithelial cells of portal bile ductuli and also in the mammary gland acini and ducti. Remarkably, Ser313, that was identified to be crucial for apical to basolateral transcytosis, is substituted in the drFcRn alpha chain. The full length of the dog and orangutan FcRn alpha chains was also identified from databases. Analyzing the phylogenetic relatedness of this gene we found that dromedary clustered together with artiodactyls, dog is located between artiodactyls and primates, where the orangutan was branched, reflecting the accepted evolutionary relationships.