FIG 2.

Quantification of salivary gland infection by Plasmodium sporozoites reveals invasion tendencies. (A) Examples of SGs with different numbers of invaded SPZs used for binning indicated as follows: no SPZs—Zero: 0 SPZ (panels i and ii); low numbers of SPZs—Lo: 1–10 SPZ (panels iii and iv); medium numbers of SPZs—Me: 11–100 SPZ (panels v and vi); high numbers of SPZs—Hi: 101–1000 SPZ (panels vii and viii); and very high numbers of SPZs—Vh: >1000 SPZ (panels ix and x). (B) Distribution of SPZ numbers in different lobes from infected SGs. (C) Localization of SPZs in the different lobes at different infection levels. At lower infection levels, most of the SPZs were associated with the basement membrane. At higher infection levels, most of the SPZs were found in secretory cavities. (D) Frequency of basal saliva accumulation by lobe in infected glands. (E) Frequency of basement membrane disruptions in different lobes from infected glands. (F) Frequency of lateral cytoplasmic disruptions in the different lobes at different infection levels. (G) Following a second, noninfective blood meal (BM) 23 days after P. berghei infection, SPZs were observed in similar SG locations: in secretory cell cytoplasms, in secretory cavities, and in the lumen (panels ii and iii, arrows). No increase in salivary duct occupancy was observed with greater SPZ numbers or with a second blood meal (panels G [iv] and C). Signal contrast was uniformly increased in panel G (iv) to highlight the salivary duct (SD). (H) In parallel, the infected mosquitoes in a second cage were given a second blood meal, and then female SGs were dissected and directly mounted on slides. Results showed individual (arrowheads) and bundled (arrows) sporozoites in similar numbers (quantified in panel I) and locations (secretory cell cytoplasm, secretory cavities, and lumen) and similar SG structural abnormality frequencies (quantified in panel J).