A vaccine formulated with Chlamydia exosomes elicits protection against a respiratory challenge

Researchers at the University of California, Irvine set out to determine if exosomes, isolated from Chlamydia muridarum infected HeLa cells (C. muridarum-exosomes), induce protective immune responses in mice following vaccination using CpG plus Montanide as adjuvants. Exosomes, collected from uninfected HeLa cells and PBS, formulated with the same adjuvants, were used as negative controls. Mass spectrometry analyses identified 113 C. muridarum proteins in the C. muridarum-exosome preparation including the major outer membrane protein and the polymorphic membrane proteins. Vaccination with C. muridarum-exosomes elicited robust humoral and cell-mediated immune responses to C. muridarum elementary bodies. Following vaccination, mice were challenged intranasally with C. muridarum. Compared to the negative controls, mice immunized with C. muridarum-exosomes were significantly protected as measured by changes in body weight, lungs’ weight, and number of inclusion forming units recovered from lungs. This is the first report, of a vaccine formulated with Chlamydia exosomes, shown to elicit protection against a challenge.

Local immunological responses in vaccinated mice at 10 days after challenge

Fig. 6

a IFN-γ levels in the lungs at 10 days after challenge. The mean is shown as a horizontal line. Each symbol represents an animal. Symbol “*” represents P value less than 0.05 by the one-way ANOVA with Holm-Sidak multiple comparisons test. b IL-6 levels in the lungs at 10 days after challenge. The mean is shown as a horizontal line. Each symbol represents an animal. Symbol “*” represents P value < 0.05 by the one-way ANOVA with Holm-Sidak multiple comparisons test. c TNF-α levels in the lungs at 10 days after challenge. The mean is shown as a horizontal line. Each symbol represents an animal. Symbol “*” represents P value < 0.05 by the one-way ANOVA with Holm-Sidak multiple comparisons test. d C. muridarum-specific IgA levels in the lungs at 10 days after challenge. The mean is shown as a horizontal line. Each symbol represents an animal. Symbol “*” represents P value < 0.05 by the one-way ANOVA with Holm-Sidak multiple comparisons test.

Pal S, Mirzakhanyan Y, Gershon P, Tifrea DF, de la Maza LM. (2020) Induction of protection in mice against a respiratory challenge by a vaccine formulated with exosomes isolated from Chlamydia muridarum infected cells. NPJ Vaccines 5:87. [article]

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