Prevention of Rift valley fever maternal and fetal infection using a single monoclonal antibody

We have a new study out today in @NatureComms that is a collaborative effort between Cindy McMillen in my lab and Nate Chapman in Jim Crowe’s lab at Vanderbilt.

The Crowe Lab published a study in 2021 that isolated human monoclonal antibodies from humans that were either vaccinated or naturally infected with Rift Valley fever virus. One of the most potent neutralizers was RVFV-268 (IC50<1 ng/ml).

We tested the ability of RVFV-268 to protect pregnant rats from RVFV infection and in utero transmission. Cindy developed rat placenta slice cultures and showed that RVFV-268 can prevent infection of placental tissue ex vivo.

She then injected RVFV-268 into rats and showed that it rapidly crossed the placenta and can be found in the fetal tissues within 6 hours.

When pregnant rats were given RVFV-268 2 hours BEFORE RVFV infection, or +6 and +24 hours AFTER infection, both dams and fetuses were protected, with only a small amount of breakthrough viral RNA in the +24h group.

Thus, delivery of mAb RVFV-268 as late as 24 h after inoculation with RVFV can remarkably reduce both maternal and fetal infection.

Our conclusions:

• RVFV-268 rapidly reaches placental and fetal tissue after injection

• It prevents maternal and fetal infection in a dose-dependent manner.

• It also prevents vertical transmission when given up to 24 h after RVFV challenge.

This single highly potent neutralizing mAb RVFV-268 is potentially useful for either prophylaxis and/or therapy during pregnancy based on our rat model.

Liver Lrp1 KO paper

We are excited to share the latest Lrp1 paper out of our lab in collaboration with the Amarasinghe and Leung labs at WashU in St. Louis. This is a huge collaborative effort with Safder Ganaie, Takeshi Egawa, and it is the final piece of work from the PhD thesis of Maddy Schwarz.

The low-density lipoprotein receptor Lrp1 mediates efficient cellular infection by the emerging prototype bunyavirus Rift Valley Fever virus. A major unanswered question from our previous work is the biologic relevance of this interaction in vivo.

Unfortunately, we can’t make an Lrp1 KO mouse because they are not viable. So Safder Ganaie and Takeshi Egawa worked with Mike White and Xiaoxia Cui at the WUSM Transgenic, Knockout and Micro-Injection Core. They generated mice with floxed Lrp1 alleles (Lrp1f/f) and crossed them to mice expressing Cre recombinase under the albumin promotor (Alb-Cre).

Voila! These mice are knockout (KO) for Lrp1 only in cells that express albumin (hepatocytes). These are liver-specific Lrp1 KO mice. But what is the significance of the liver in RVFV infection?

 
 

RVFV is a promiscuous virus that can infect a wide range of cell types. Mice are SUPER susceptible to lethal disease and die within 3-5 days after infection with low doses of RVFV. Virus is found in many tissues, but the liver generally contains the most virus and contributes to early hepatic disease and death.

So it made sense to examine the role of Lrp1 in the liver and determine its biological significance.

We infected liver Lrp1 KO mice with RVFV by footpad injection. We compared virus spread and lethality to a control group of mice that had intact liver Lrp1. We found that the liver Lrp1 KO mice remarkably survived past the 3-5 day window of lethal hepatic disease! However, the mice eventually succumbed to neurological disease due to extensive viral replication in the brain where Lrp1 remained intact.

 
 

Equally remarkably, the livers of Lrp1 KO mice contained basically no infectious virus. Control mice had titers of 10,000 – 100,000 pfu. Without Lrp1 in hepatocytes, RVFV was unable to replicate in the liver!

 
 

Interestingly though, dissemination and replication in other tissues (spleen, lung, heart) was unaffected by lack of Lrp1 in the liver. It has been assumed that high levels of RVFV replication in the liver seeds replication in other tissues, but our data suggest that this is not the case.

Our main conclusions are:

1)     Lrp1 is required for lethal hepatic RVF disease in mice.

2)     Other LDLR family members are unable to compensate for lack of Lrp1.

3)     Lack of Lrp1 in hepatocytes does not affect dissemination to other organs and tissues.

This was a really fun study to do and a collaborative project across Amarasinghe, Leung, and Hartman labs. Huge shoutout to @GanaieSafder for initiating this work and for continued efforts on this project with us!

Coming soon

We have two publications that will be coming out soon. The last of Maddy’s work from her thesis will be published on July 14th! And the latest paper from Cindy is officially accepted with publication date TBD but likely in the next 4-6 weeks. More info and links to come!

ASV Wrap-Up

Zach, Kaleigh, and Rachael had a great time at ASV2023. See photos here.

I am going to try to update this blog more often. I’m not on twitter as much as I used to be...so look for more updates here!

ASV2023 - where can you find us?

We will be at ASV2023 at UGA in Athens, GA:

 

The crew is on their way!

 

SUNDAY 1:30 PM–1:45 PM W18-1 R. Rush, S. Ganaie, C. McMillen, D. A. Price, M. M. Schwarz, X. Cui, D. W. Leung, G. Amarasinghe, A. Hartman. Rift Valley fever virus displays high permissivity for trophoblast cells lines and requires Lrp1 for efficient infection

TUESDAY W59-7 3:30 PM–3:45 PM K. A. Connors, N. S. Chapman, C. McMillen, Z. D. Frey, R. M. Hoehl, J. McGaughey, M. Midgett, C. Williams, D. S. Reed, J. Crowe, A. Hartman. Therapeutic delivery of potent neutralizing human monoclonal antibodies improves survival after aerosol exposure to rift valley fever virus

TUESDAY P39-9 Z. D. Frey, K. A. Connors, S. Ganaie, D. A. Price, M. M. Schwarz, X. Cui, Z. P. Wills, D. W. Leung, G. Amarasinghe, A. Hartman. Characterizing Jamestown Canyon virus infection of primary neurons and dependence on Lrp1

Accepted & in press

The last paper from Maddy’s graduate work has been accepted at Science Advances. Publication date forthcoming ~2 weeks or so.

Sneak peek title: Lrp1 is essential for lethal Rift Valley fever hepatic disease in mice

Congrats Bayley!

Bayley is an MPH student in IDM. She wrote her essay on research she did with our group on genetic polymorphisms in LRP1. Congrats Bayley on a successful presentation of your essay yesterday! Bayley will graduate at the end of this month.

Welcome to Austin!

I am very excited to bring on new students and their diverse perspectives on our work. Austin Hertel is the second PhD student from PMI that just joined us. Austin rotated in the fall and worked with Cindy on placenta related projects. He also did not seem to be scared away!

I notice a trend though. Rachael likes to take our rotation students into the RBL!

Austin will be working with Cindy on everything pregnancy and placenta.

Austin tell us:

“I am originally from Rochester, NY and attended Gannon University in Erie, PA. While at Gannon, I completed a bachelor’s degree in biology & public health and competed as a 5-year starter on the men’s wrestling team. Now in Pittsburgh, I live in Highland Park with my little black cat, Wednesday. Outside of the lab I like to keep as active as possible. During the winter, I am still involved in the sport of wrestling by volunteering at a local high school. In the summers, I enjoy mountain biking, hiking, and playing really bad golf! Besides physical activity I love to play music. I’ve played the guitar since high school and still occasionally enjoy a jam-session with friends. Fun fact, I also used to play the French horn and is still my favorite instrument.”