Phylogeography of Bellamya (Mollusca: Gastropoda: Viviparidae) snails on different continents: contrasting patterns of diversification in China and East Africa.

BACKGROUND: Species diversity is determined by both local environmental conditions that control differentiation and extinction and the outcome of large-scale processes that affect migration. The latter primarily comprises climatic change and dynamic landscape alteration. In the past few million years, both Southeast Asia and Eastern Africa experienced drastic climatic and geological oscillations: in Southeast Asia, especially in China, the Tibetan Plateau significantly rose up, and the flow of the Yangtze River was reversed. In East Africa, lakes and rivers experienced frequent range expansions and regressions due to the African mega-droughts. To test how such climatic and geological histories of both regions relate to their respective regional species and genetic diversity, a large scale comparative phylogeographic study is essential. Bellamya, a species rich freshwater snail genus that is widely distributed across China and East Africa, represents a suitable model system to address this question. We sequenced mitochondrial and nuclear DNA for members of the genus from China and used published sequences from Africa and some other locations in Asia to investigate their phylogeny and distribution of genetic diversity. RESULTS: Our phylogenetic analysis revealed two monophyletic groups, one in China and one in East Africa. Within the Chinese group, Bellamya species show little genetic differentiation. In contrast, we observe fairly deep divergence among the East African lakes with almost every lake possessing its unique clade. Our results show that strong divergence does not necessarily depend on intrinsic characteristics of a species, but rather is related to the landscape dynamics of a region. CONCLUSION: Our phylogenetic results suggest that the Bellamya in China and East Africa are independent phylogenetic clades with different evolutionary trajectories. The different climate and geological histories likely contributed to the diverging evolutionary patterns. Repeated range expansions and regressions of lakes likely contributed to the great divergence of Bellamya in East Africa, while reversal of the river courses and intermingling of different lineages had an opposite effect on Bellamya diversification in China.

The Immunological Functions of Muramyl Dipeptide Compound Adjuvant on Humoral, Cellular-mediated and Mucosal Immune Responses to PEDV Inactivated Vaccine in Mice.

BACKGROUND: The muramyl dipeptide compound adjuvant, CVC1303, was one new resigned adjuvant to PEDV inactivated vaccine. Exploring the effects of CVC1303 on the immune induction to PEDV vaccine was of vital importance to the clinical application. OBJECTIVES: Here we explored the functions of CVC1303 on the humoral, cellular and mucosal immune response to PEDV vaccine in mice immunization. METHODS: Mice were twice subcutaneously injected with PEDV vaccine including high, medium and low dosages CVC1303, respectively. On 30th day after the second immunization, sera samples were collected from the immunized mice to measure PEDV-specific IgG and IgG subclasses levels, and lymphocytes were isolated to detect T cell subtype and intracellular IL-4 and IL-6 cytokine productions, and the expressions of co-stimulatory molecule on dendritic cells in the immunized mice. Small intestinal and lung washings were collected on 30th and 47th day after the second immunization to measure PEDV-specific IgA levels, and SP immunohistochemical method staining was employed to analyze the deviations of IgA+ positive cells in the small intestinal of the immunized mice. RESULTS: Our investigation proved the strong regulatory roles of CVC1303 on PEDV-specific IgG and IgG1 antibody and cytokines productions, and the significant increased CD3+CD4+T cells subpopulation and expressions of co-stimulatory molecules on dendritic cells in the immunized mice. Moreover, our findings verified the significantly enhanced PEDV-specific IgA antibody titers in small intestinal and lung in the mice immunized with PEDV vaccine and CVC1303. CONCLUSION: Compound adjuvant CVC1303 could effectively improve the PEDV-specific immune responses and mucosal immune, which provided an experimental basis for the further clinical application of new adjuvant CVC1303 and the development of improvement on the mucosal immune response.