I wonder if its physically possible that he is immune. It may actually be possible...
From some herpes site...
"Finally, the question of immunity and HSV types is complicated by an additional issue. Some studies suggest that the ganglia themselves may acquire some immunity to HSV after they are exposed to one viral type.
In the laboratory, infection of ganglia with more than one virus is difficult, suggesting that it may be more difficult to acquire a second HSV type in a location where you already have HSV. A prior genital infection with HSV-1, for example, may give more protection against genital HSV-2 than a prior oral infection with HSV-1."