Nowadays, many research lines are directed to study some components derived from natural sources, which might simply improve our life by protecting us and improving our health. Historically, camel’s milk has been used for medical purposes and treatment of some diseases. Many useful properties are assigned to camel’s milk that has been traditionally used for the treatment of tuberculosis, gastroenteritis and allergy, and is also drunk as a tonic. The beneficial properties of camel’s milk, among them its antimicrobial activity, can be attributed to substances such as proteins, lipids, carbohydrates and vitamins. Among milk proteins, lactoferrin, IgGs, α-lactalbumin, casein, lactoperoxidase, lysozyme, and some peptides are the main components that have been suggested to possess those activities [19–22].
In this work, we studied the antiviral activity of camel IgGs, α-lactalbumin, lactoferrin, and casein in comparison with three human commercial intravenous immunoglobulins G, against hepatitis C virus by determining its infectivity in Huh 7.5 and PBMCs cell lines. The results showed that camel IgGs and lactoferrin prevented HCV from entry into PBMCs and Huh7.5 cells when assessed by two in vitro assays. The second was an assay based on the direct interaction of proteins with the virus particles, and the first one evaluated the protection of the cells by the proteins. We observed that camel α-lactalbumin, casein and human IVIGs at concentrations of 0.5 and 1.0 mg/ml failed to inhibit HCV molecules from entry into PBMCs and Huh7.5 cells, as shown by both types of assays. However, the results obtained by electrophoretic analysis showed no band corresponding to HCV when the activity of camel casein was evaluated on Huh7.5 cells, though that was caused by a reduced viability of the cells because camel casein induced apoptosis. The viability of Huh7.5 cells was greatly reduced and consequently, the HCV amplified 174 bp band could not be detected, which confirm the previous report . The apoptosis caused by camel casein is in accordance with the results published in the study of Håkansson et al.  in which it was reported that human casein (α-lactalbumin bound to casein was implicated in its apoptotic activity) and bovine α-lactalbumin unfolded and forming a complex with oleic acid called “human α-lactalbumin made lethal to tumor cells” (HAMLET), induced differential and significant apoptosis in several cancer lines [25, 26].
We also described in a previous study  that camel casein at the concentrations used in the present work, initiated apoptosis in HepG2 cells, reducing their viability and consequently, the detection of HCV RNA. No antiviral activity against different virus has been either shown by intact bovine casein , however, these authors reported that bovine casein when was chemically modified could acquire antiviral activities .
The results of anti-HCV activity of cLf were in agreement with a previous study [28, 29] which used cLf to inhibit HCV (genotype 4) entry into human PBMCs and with another study  which showed that cLf inhibited HCV entry into HepG2 cells. This antiviral activity of cLf against HCV also agree with previous studies in other cell lines that reported that human and bovine lactoferrin inhibited HCV (genotype1) entry into the non-neoplasic human hepatocyte cell line PH5CH8  at a concentration limit of 2 mg/ml. Our results showed that cLf at concentrations of 0.5, 1.0 and 1.25 mg/ml inhibited HCV replication inside infected cells after the first dose of treatment (four days) and at concentrations of 0.25 and 0.5 mg/ml after the second dose of treatment (another four days).
The inhibitory activity of purified camel polyclonal IgGs against HCV found in the present work is in agreement with results reported of Martin et al.  who described the inhibitory activity of recombinant camel VH domain antibody biopanned against HCV NS3 protease and partially ascribed by a recent study . Camel’s IgG are not limited to one major subclass IgG1, but includes three main subclasses (IgG1, IgG2 and IgG3) . IgG2 and IgG3 subclasses are devoid of light chains and have heavy chains of 45 and 42 kDa, respectively . It has been suggested that the functional domain (the N-terminal variable region of the heavy chain antibodies referred as VH that is the minimal intact antigen-binding fragment that can be generated) of the heavy-chain antibodies interfere with several biological processes and might make good candidates for human therapy . IgG2 and IgG3 act as true competitive inhibitors by penetrating into active sites of some enzymes [32, 33]. They might have inhibitory activity on human immunodeficiency viruses type 1 (HIV-1) reverse transcriptase, protease, and integrase enzymes that are crucial to the HIV-1 life cycle .
The potential activity of IVIG preparations was used in the treatment and prophylaxis of infectious diseases and toxin, and they were also used as specific antibodies against causative bacterial LPS , but at least from the information we have available there is no previous study using human IVIGs in the neutralization of hepatitis C virus in vitro. We found that cLf acts as a strong anti-HCV agent and camel IgG acts as an intermediate agent, while camel casein, α-lactalbumin and IVIGs failed to inhibit HCV. Camel casein was not able to prevent or neutralize HCV from cell-entry at both levels, by direct or indirect interactions. Passive immunization with antibodies for the prevention and treatment of diseases become part of medical therapy, intravenous immunoglobulin being most important plasma natural product available for therapeutic use [36–38]. One gram of intravenous immunoglobulin G (IVIG) contains 4 × 1018 molecules with more than 107 antibody specificity. This fact leads to a tremendous increase in IVIG availability and its subsequent use in the clinical setting.
Several evidences demonstrate that neutralizing antibodies are present in patients with chronic hepatitis C, and the epitopes located within the E2 protein are important for HCV neutralization. Thus the experimental preparation made from anti-HCV-positive plasma (HCIGIV) prevented HCV infection when mixed with a virus inoculum ex vivo before infusion into chimpanzees. Unfortunately, the in vivo efficacy of HCIGIV in both chimpanzees and humans has been disappointing . However, the human blood and/or plasma fractions industry exclude any blood or plasma fraction containing HCV antibodies . This might explain the historical evidence that normal immunoglobulins manufactured before the screening of blood or plasma donor for HCV infection protected against hepatitis C [35, 38].