الفهرس 
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Abstract
HBV infection is a serious global health problem despite the advent of effective vaccines. The ability to develop and preserve an efficient HBV-specific adaptive immune cell network is thought to represent the most important discriminatory factor between HBV control or chronicity where the successful control of HBV infection requires an integrated activation of both the cellular and humoral arms of the adaptive immune response and that the failure of one of them clearly affects the expansion and protective efficacy of the others.
Vitamin D is a group of fat-soluble steroid hormone that can modulate the innate and adaptive immune responses and its deficiency causes an increased susceptibility to Hepatitis B viral infection. Serum concentration of vitamin D has recently been proposed as a novel predictor of response to antiviral treatment in chronic hepatitis infection.
The present study aimed to elucidate the effect of Vitamin D supplementation and UVB lamb exposure on short and long term performance of hepatitis B vaccine by assessment of HBs Abs isotypes (IgM, IgG& IgA) and their avidity.
The study was conducted on a total of 20 New Zealand rabbits that were randomly divided into 4 groups. The first 3 groups were intramuscularly immunized with commercially available recombinant HBsAg where rabbits in the first group were left as un-manipulated rabbits while the rest were either exposed to UVB or supplemented with commercially available vitamin D (10 rabbits; 5 each). At week zero as well as 1 week following each booster dose, rabbits were bled in order to obtain peripheral blood for parallel assessment of both vitamin D and different isotypes (IgM, IgG and IgA) of anti-HBsAg. HBsAb isotypes IgG, IgM and IgA were monitored in rabbit sera by an indirect home enzyme linked immunosorbent assay (ELISA). At various intervals after HBsAg immunization, sera belonging to various rabbit groups were assayed for both antibody isotype levels as well as the antibody avidity testing; in order to evaluate the strength of binding between the immunizing HBsAg and its corresponding HBsAb.
The present study revealed that there was a statistical significant difference in the mean of vitamin D serum concentrations between the studied groups, where mean vitamin D concentrations was higher in UVB exposed groups compared to vitamin D supplemented group during the short and long time intervals.
Our results showed that there was a statistical significant difference in the mean of IgG and IgA anti-HBsAg serum concentrations between the studied groups, where means of IgG and IgA anti-HBsAg serum concentrations were significantly higher in un-manipulated rabbits compared to vitamin D supplemented and UVB exposed rabbits, whereas IgM anti-HBsAg results did not show any significant variations.
The results revealed that IgG anti-HBsAg and vitamin D serum concentrations were positively correlated in un-manipulated group at week 3 and 7, while in UVB exposed group, they were negatively correlated at week 3. Regarding IgM anti-HBsAg results, they were negatively correlated at week 3 in UVB exposed rabbit, however no correlation was
observed between vitamin D and IgA anti-HBsAg. Referring to avidity results, IgG avidity and vitamin D were positively correlated in vitamin D supplemented group at week 3
On the other hand, IgM avidity % were negatively correlated with vitamin Din un-manipulated group and UVB exposed rabbits at weeks 4 and 5, respectively.
It was concluded that sufficient circulating serum vitamin D levels achieve premium immune response following HBV vaccine schedule through its immune regulation mechanism.