Field of Science

HIV finds a cellular door knob - the SIGLEC1 story

Viruses are classed as 'obligate intracellular parasites' and so they have to get inside a host cell, whether they are bacterial, archaeal or eukaryotic. In the case of mammalian viruses, which I have the most experience in, this is a key aspect of how viruses infect, cause disease and transmit themselves from one host to another in a population. In fact it is probably the most important event in the virus life cycle (here's a great link describing the replication cycle of HIV).

Example: Viruses like influenza that really only get inside lung cells will be respiratory transmitted and may cause lung diseases while viruses like HIV that get inside your immune cells and find themselves rushing around your blood stream will only spread via contact with bodily fluids. This is the same for every other human virus in existence.

However one major obstacle to getting inside your cells is the cell membrane, which is impermeable to particles the size of viruses. The virus must coax or force its way into the cell cytoplasm where it can begin its replication cycle and make new virus particles.

This is what a virus has to contend with: the plasma membrane. But what molecule on the surface will it interact with?