Viruses and Heparan Sulfate: A Survival Trade-Off

Viruses change quickly to survive in new environments. Sometimes, they pick up positively charged proteins on their surface to stick to negatively charged heparan sulfate (HS) when grown in lab dishes. We studied a virus called enterovirus A71 (EV-A71) and found that a variant, MP4-97R/167G, doesn't need acid to release its genetic material. Instead, it does this in a neutral or slightly acidic environment. Our experiments showed that this isn't because of HS, but because the virus's outer shell isn't as strong. We saw this with another strain too. So, viruses that stick to HS have weaker shells and can enter cells without needing acid. This helps them grow in labs but might hurt them in the body, especially in the stomach before they reach the intestines. Our study reveals that these viruses aren't just trapped in tissues with HS, but their weak shells also make them less fit in harsh body environments. It's a balancing act between sticking to HS, shell strength, and how well the virus survives.