One of the more interesting hetero sero-discordant studies is the Padian 10 year study. Trying to isolate for hetero sexual transmission, they actually strictly eliminated all drug users by using actual drug tests - something that others have not done to my knowledge.

Yes, I don't know any other studies that used direct drug tests. There is this Madrid study of heterosexual transmission that used indirect testing of "markers related to drug addiction (e.g., hepatitis C serology)" to check for drug use in addition to questionnaires, and its recorded transmission rate is quite high: 26%, out of 38 couples. However, it looks like a retrospective study.

We found only marginal significance for enrollment in the study prior to 1990 (OR = 1.9), not using condoms (OR = 1.7), and >300 unprotected penile-vaginal or penile-anal contacts (the median number of contacts) (OR = 1.6) [snip]

So large amounts of unprotected sex did not appear to be a very significant risk factor. The highest risk factor was just anal sex as a practice, not the number of contacts.

Although quantity of sex doesn't seem to have made much difference, the unadjusted odds ratio associated with not using condoms bordered on statistical significance with a confidence interval of 0.95 to 3.01. After adjusting for the number of sexual contacts, that odds ratio went up to 2.1, becoming significant and equal to the adjusted odds ratio associated with anal sex. I notice too that after adjustment, STI history — a risk factor elsewhere associated with HIV transmission — was the risk factor with the highest odds ratio.

But what was really interesting in this group of some 600ish hetero non-drug users was that during the length of the study, there was not a single seroconversion, even though condom use in these couples was imperfect:

It would be more interesting if the relevant sample did contain 600 heterosexual non-drug users followed for the length of the study. However, the "no seroconversions" result comes from the study's prospective part, which involved only "175 HIV-discordant couples over time, for a total of approximately 282 couple-years of follow-up [...] attrition was severe". That's a mean follow-up time of only 19 months per couple. Most couples probably got less follow-up time than that, because severe attrition would tend to negatively skew the follow-up time distribution, depressing the median.

That's not all. The investigators didn't just counsel the couples on safe sex, but also set up a 24-hour telephone support line, a newsletter and regular meet-ups. These measures were very effective in changing the couples' behaviour: by the final follow-up, 15% of the 175 couples abstained from sex and 74% used condoms. So, at final follow-up, only 11% of the couples — nineteen in absolute terms — were at substantial risk of HIV transmission. The study's statistical power to detect the small (in absolute terms) risk of heterosexual HIV transmission wouldn't have been that great, especially given "the lack of incident STDs during the course of the study" (page 355).

There is zero evidence that non-drug using heterosexuals acquire the disease sexually, and studies such as this are evidence favoring a vertically transmitted virus.

You're exaggerating. Even ignoring all other work on HIV's epidemiology, there's evidence of heterosexual HIV transmission in this very study! Its prospective aspect is just half of the research; there's also the cross-sectional sample, which includes 230 couples recruited after the researchers began screening subjects for drug use in 1990. HIV transmission occurred in this subgroup, and after adjusting for estimated number of sex acts across the entire cross-sectional sample, there was no association between being enrolled before 1990 and HIV transmission (adjusted odds ratio = 1.0, 95% confidence interval = 0.98-1.0), so the transmissions in the cross-sectional group can't just be attributed to the pre-1990 (i.e. unscreened) subgroup. (And again, recall the higher odds ratio for failing to use condoms and having a history of STIs. That sounds like more evidence of sexual transmission to me!)

Why does it only spread laterally into gay men and drug users, even though this is extraordinarily unlikely if it truly is horizontally transmitted?

But...it doesn't only spread laterally into gay men and drug users?

I haven't analyzed genital herpes and know very little about it, and regardless it is irrelevant. If the data says that HIV can not be sexually transmitted, and another disease has the same epidemologial data and is also called an STD, that somehow doesn't magically change the data.

That's true!

It just makes both classifications wrong.

Or your definition of an STI too restrictive.

There is no 'luck' and it all depends on the ratios. If only 1% of HIV+ people refuse treatment, but even just 10% of all "long-term non progressors" refuse treatment, then clearly treatment itself is part of the problem.

I think you have some implicit assumptions there to unpack.

It is strange and interesting that you think the cofactors only could work in favor of your privileged hypothesis. There is also the placebo effect to consider, and in a drug trial that is not double blind (as the AZT trials could not be) those who found out they were getting placebo believed they were going to die, and that encouraged wreckless behavior, not the other way around.

Do you have references for this?

Also, all the reports on LTNPs I have read are unanimous on lifestyle change being a distinguishing factor- reduction in drug use and bathouse type partying, general increase in healthier behavior.

Well, I expect that helps. (Which is not to say that switching to a healthy lifestyle halts the progression into AIDS.) I can't imagine doing poppers and having casual sex is a good thing for anyone with HIV. (Come to think of it, isn't it possible for someone who already has HIV to reinfect themselves with other substrains and make their infection worse?)

However, they still die at accelerated rates, and some eventually get AIDS.

Makes sense.

I think I'll hold off on commenting on the last couple of paragraphs about AZT since (1) I really don't know much about AZT, and (2) this discussion is becoming quite extensive and too much of a time sink for my liking.