Thread by @KuenzliMarco

How does route of #mRNA #vaccination impact localization and abundance of CD8 & CD4 memory T cells? shorturl.at/foBMY

@TwiterlessBuck
@Masopust_Vezys

Thanks to all co-authors and sponsors including @Tibabiotech @niaidcivics @snsf_ch @CFI_UMN @rafiahmed_lab

🧵👇🏼

Take home:
✅intramuscular (IM) vaccination induces few lung TRM
✅intranasal (IN) vaccination makes more lung TRM
✅TFH memory is confined to vaccine-draining LN
✅IM prime+boost + IN boost establishes robust circulating and lung resident memory T cells

We also show:
✅mRNA can be administered intranasally
✅residence of vaccine-elicited T cells using a migration assay (independent of surface markers)
✅CD8 T cells in the upper respiratory tract
✅CD8 T cell longevity in lung and upper respiratory tract compartments

The current COVID pandemic has led to mass-adoption of mRNA vaccines. Studies have shown that antibodies can lose their ability to bind virus particles that have accumulated mutations over the parental strain, yet vaccinated people are still protected from severe outcome. How?

Cross-reactive T cells might play a role in protection. The lung is the primary site of SARS-CoV2 infection. While mRNA vaccine-elicited memory T cells have been well characterized in blood, less is known about T cells in the lung due to sampling difficulties in humans.

In respiratory infections, memory T cells resident in the lung (lung TRM) can play a protective role in both mice and humans. Whether mRNA vaccination elicits bona fide TRM in the lung and regional LNs is clinically relevant. Most but not all TRM express CD69, some express CD103.

Mimicking the human vaccination regimen, we assessed whether lung TRM are induced upon IM vaccination, and whether the side of booster administration matters.

IM vaccination induces a few IV- Tet+ CD69+ CD8 & CD4 T cells in the lung independent of booster side! However, IM vaccine-induced CD8 memory T-cells depicted below do not express CD103.

However, we found that same-side boosting resulted in slightly higher NP-specific antibody titers.

Surprisingly, IM vaccine-elicited immunity to flu nucleoprotein is protective against lethal flu challenge. However, we do not envision a T cell only vaccine, but advocate for including T cell epitopes in currently available vaccines that contain neutralizing antibody epitopes.

CD4 memory T cell subsets in secondary lymphoid organs are spatially segregated, while FR4hi TFH memory is found in vaccine draining LNs only, Ly6C+ Th1 are preferentially found in the spleen.

We next wondered how different routes of vaccine delivery impact abundance, phenotype, and localization of vaccine-induced CD8 & CD4 memory T-cells.

Intranasal vaccination induced more IV- Tet+ CD69+ CD8&CD4 memory T cells in the lung. CD8s in addition express CD103 upon IN but not IM vaccination in the lung, and are also present in BAL, nasal tissue, and trachea.

CD4 memory T cells in the lung have predominantly a Th1 like phenotype, TFH-like memory cells (aka TRH) are absent in the lung upon both IM and IN route. However, IN immunization reproducibly generated a FR4 int population of CD4 memory T cells.

Using parabiosis, a migration assay, we show that most CD69+ T cells are bona fide lung TRM, but a surprisingly large fraction of CD69- T cells are resident as well, highlighting that migration assays independent of surface markers are important to not underestimate TRM.

Last, IM prime boosted CD8 & CD4 memory T cells in the lung can be further expanded with an additional intranasal booster, yielding CD103+ CD8 TRM while maintaining a robust circulating memory T cell compartment

Open ?s:
❓How are lung TRM induced upon IM vaccination? Is antigen present in the lung? Or promiscuous seeding?
❓Lung is a difficult organ to achieve long-lasting immunity. Although promising, is IN really better than IM in the long run? Needs to be tested in humans.