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Angiostrongylus cantonensis is of increasing public health importance as the main zoonotic pathogen causing eosinophilic meningitis or meningoencephalitis, which has been documented all over the world. However, there are very limited studies about its phylogeography and spread pattern. In the present study, the phylogeography of A. cantonensis in southern China (including Taiwan) and partial areas of Southeast Asia were studied based on the sequences of complete mitochondrial cytochrome b (Cytb) gene. A total of 520 individuals of A. cantonensis obtained from 13 localities were sequenced for the analyses and grouped into 42 defined haplotypes. The phylogenetic tree (NJ tree and BI tree) revealed a characteristic distribution pattern of the four main lineages, with detectable geographic structure. Genetic differentiation among populations was significant, but demographic expansion could not be detected by either neutrality tests or mismatch distribution analysis, which implied a low gene flow among the local populations in different regions where the samples were collected. Two unique lineages of the A. cantonensis population in Taiwan were detected, which suggests its multiple origin in the island. Populations in Hekou (China) and Laos showed the highest genetic diversities, which were supported by both genetic diversity indices and AMOVA. These results together infer that the area around Thailand or Hekou in Yunnan province, China are the most likely origins of Angiostrongylus cantonensis.

In order to evaluate immunogenicity and protective efficacy of LytA from Streptococcus pneumoniae, we subcloned the full-length lytA-encoded autolysin (LytA) from 5 major pathogenic serotype isolates in China and obtained purified rLytA. Bioinformatics analysis showed that sequences of LytA were highly conserved in all strains we used in this work, and western blot analysis demonstrated that rLytAs from heterogeneous serotypes were cross-recognized by serum of mice infected with 23F strain SH137. Mice were intranasally immunized with purified rLytA, and serum anti-rLytA IgG, IgA and secretory IgA were elicited. More importantly, rLytA intranasal-immunized mice showed a significantly higher survival rate and lower bacterial carriage in response to infection by Streptococcus pneumoniae. The fact that mice immunized with rLytA from strain SH137 also had a higher survival rate after intraperitoneal injection of other four serotype strains of living S. pneumoniae suggested that it possessed cross-protection effect. Our study revealed that intranasal immunization with rLytA may protect mice against mucosal and systemic pneumococcal infection; hence, it was an attractive vaccine candidate.