TWiV 278: Flushing HIV down the zinc

On episode #278 of the science show This Week in Virology, Vincent, Dickson, Alan, and Kathy discuss disruption of the ccr5 gene in lymphocytes of patients infected with HIV-1.

You can find TWiV #278 at www.microbe.tv/twiv.

TWIV 266: A pathogenic vicious cycle

On episode #266 of the science show This Week in Virology, Vincent, Alan, and Kathy discuss finding viruses in outer space, varying results obtained from personal genetic testing, and depletion of CD4 cells during HIV infection by pyroptosis.

You can find TWiV #266 at www.microbe.tv/twiv.

TWiV 260: Badgers go viral

On episode #260 of the science show This Week in Virology, Vincent visits the University of Wisconsin, Madison and speaks with Tom, Tony, and David about their work on virus discovery at the AIDS Vaccine Research Laboratory.

You can find TWiV #260 at www.microbe.tv/twiv.

TWiV 244: Back in the CVVR

Episode #244 of the science show This Week in Virology was recorded before an audience at the Beth Israel Deaconess Medical Center, where Vincent and Alan spoke with Dan and Jeff about AIDS vaccines.

You can find TWiV #244 at www.microbe.tv/twiv.

TWiV 237: Paleovirology with Michael Emerman

Episode #237 of the science show This Week in Virology was recorded at the Fred Hutchinson Cancer Research Center in Seattle, WA, where Vincent and Rich met up with Michael to talk about his work on the molecular and evolutionary basis of HIV replication and pathogenesis.

You can find TWiV #237 at www.microbe.tv/twiv.

Hilary Koprowski, 96

Racaniello, Koprowski, KessinVirologist Hilary Koprowski died on 11 April 2013 at the age of 96. His main accomplishments are nicely summarized in the New York Times, but for a more comprehensive overview of his life, I highly recommend his biography Listen to the Music by Roger Vaughan. I did not have many opportunities to interact with Dr. Koprowski, but I did follow his work on poliovirus vaccines and I have a few reminiscences.

In the 1930s Max Theiler had found that propagating yellow fever virus in an unnatural host – the chick embryo – dramatically reduced its capacity to cause disease in humans. Theiler’s work (which garnered him a Nobel Prize) lead to the production of the infectious, attenuated yellow fever vaccine which helped to vastly reduce the global incidence of yellow fever. Koprowski was inspired by Theiler’s work and decided to take a similar approach to developing a poliovirus vaccine – his first efforts involved passage of a type 2 strain of poliovirus in mice and then in cotton rats. After passage in  rodents, the virus did not cause paralysis in monkeys. Koprowski tested the candidate vaccine strain in humans, and ultimately produced two other attenuated poliovirus strains. By the 1960s these attenuated poliovirus vaccine candidates had been tested in millions of humans. However, they were never licensed for use in the US. While Koprowski was carrying out his work, Albert Sabin was also developed attenuated vaccine strains of poliovirus. Both Sabin’s and Koprowski’s strains were tested side by side in a monkey neurovirulence test carried out by Joseph Melnick at Baylor University. Sabin’s virus strains were slightly more attenuated, and in 1961-62 those were selected for licensing in the US. Sabin’s oral poliovirus vaccines (OPV) have been the mainstay of the World Health Organization in its polio eradication campaign.

Koprowski’s polio vaccines were tested by human clinical trials, notably in the former Belgian Congo in 1957-58. It was subsequently suggested that this clinical trial initiated the AIDS pandemic. The idea, first proposed by Tom Curtis (19 March 1992 “The Origin of AIDS: A startling new theory attempts to answer the question, ‘Was it an act of God or an act of man?” Rolling Stone pp. 54–9, 61, 106, 108) and subsequently by Edward Hooper in ‘The River‘, was that Koprowski had propagated the vaccine strains in kidney cell cultures produced from locally captured chimpanzees. If these animals were infected with the precursor of HIV-1, simian immunodeficiency virus (SIV), then the virus might have entered the human population during the polio vaccine trials. This hypothesis was subsequently shown to be incorrect as phylogenetic analysis showed that the main group of HIV-1 viruses, the M group, clearly crossed from chimpanzees to humans in the early 1900s.

A committee was established to investigate the virological aspects of the HIV-polio vaccine controversy, and towards the end of its work I was asked to join. When it was discovered that samples of Koprowski’s polio vaccines were frozen at the Wistar Institute in Philadelphia, it was decided to determine whether these vaccines had been propagated in rhesus monkey or chimpanzee cells.

I was given the job of dividing and coding the samples. I met a representative of the Wistar Institute in the parking lot of a restaurant just off the New Jersey Turnpike, halfway between New York and Philadelphia. He handed me a white styrofoam box, packed with ice, that contained  vials of the Koprowski vaccine. To the uninformed observer, it might have looked like a drug exchange.

CHAT vialsI took the vials back to the lab (see photo), thawed them, separated them into aliquots, and gave each a code. I then returned them to the Wistar in the same way, after a second trip on the New Jersey Turnpike. The samples were sent to three different laboratories where experiments were done to determine the mitochondrial DNA type of the cells in which the viruses had been propagated (although the samples were free of cells, some mitochondrial DNA would still be present from virus induced cell lysis). The results, which have been published (reference one, two), clearly showed that the vaccines had not been grown in chimpanzee cells. I was pleased to have played a small role in this story.

Koprowski autograph

Although I had spoken with Dr. Koprowski several times on the telephone, I did not meet him until 2005 when he presented a talk on the history of rabies in the History of Science series at Columbia University Medical Center. I was his host for that visit, during which I was photographed with Dr. Koprowski and Dr. Rich Kessin, another Columbia professor. We invited Dr. Koprowski to dinner after the seminar but he declined, but he did want to have a drink together. After being warned by his driver not to keep him too late, we walked to a local bar and Dr. Koprowski ordered a Boodles gin martini. The bartender noted that he didn’t receive many calls for that brand. Dr. Koprowski said it was his favorite gin. We talked for a while and then returned Dr. Koprowski to his car for the trip back to Philadelphia. During his visit I had Dr. Koprowski autograph my copy of Listen to the Music (photo). He wrote: “To my friend Vince, with warmest regards, Hilary, 4/14/05.” It was the first and last time I saw him.

I would like to relate one last story which has nothing to do with me, but is irresistible. It takes place in the opening pages of Listen to the Music. Koprowski and his technician Thomas Norton are about to drink an early version of his attenuated polio vaccine. The virus has been passaged in rats and appears to be attenuated in monkeys. On a January day in 1948 Koprowski and Norton are in a laboratory at Lederle Laboratories in Pearl River, NY., where they are blending the brains and spinal cords of rats that had been infected with the vaccine strain virus. They both drink a milliliter of the cold, greasy, mix which flows thickly over their tongues and is difficult to swallow.

Here is the best part:

When he can speak, Norton asks, “Have another?”

“Better not,” Koprowski says. “I’m driving.”

TWiV 225: Transcripts from the inbox

On episode #225 of the science show This Week in Virology, Vincent, Rich, and Kathy read listener comments and questions on viral oncotherapy, science communication, a functional HIV cure in an infant, and much more.

You can find TWiV #225 at www.microbe.tv/twiv.

Antimicrobial peptides induced by herpesvirus enhance HIV-1 infection

Langerhans cellsThe risk of being infected with human immunodeficiency virus type 1 (HIV-1) is substantially enhanced in individuals with other sexually transmitted diseases. For example, infection with herpes simplex virus type 2 (HSV-2) increases the risk ratio of acquiring HIV from 2 to 4. Explanations for this increased risk include direct inoculation of HIV-1 into the blood through genital ulcers, and the induction of inflammatory cells by HSV-2 which act as sites of replication for HIV-1. The results of infections carried out in cell culture suggest a biological mechanism for the enhancement of HIV-1 infection by HSV-2.

Langerhans cells (LC) are believed to one of the first cells in which HIV-1 replicates after sexual exposure. LCs are dendritic cells which patrol the mucosal epithelium, taking up and processing antigens and presenting them to T cells in the lymph nodes. These cells express the HIV-1 receptors CD4 and CCR5, but not CXCR4, and can therefore be infected with CCR5-tropic* but not CXCR4-tropic HIV-1. Individuals who do not express CCR5 are resistant to HIV infection. For these and other reasons CCR5-tropic HIV-1 viruses are believed to be ones that transmit infection from one individual to another.

In human skin explant cultures, which contain LCs, co-infection with HSV-2 substantially increased the number of HIV-1 cells. This observation could not be explained by co-infection of individual cells because very few of these were observed in the cultures. When applied to fresh cells, the supernatant of cultures infected with HSV-2 also stimulated the number of HIV-1 infected LCs. These observations suggested that HSV-2 infection stimulates the production of one or more substances from infected cells which in turn improve HIV-1 infection.

Human epithelial and epidermal cells are known to produce antimicrobial peptides such as defensins and cathelicidin. These are short, evolutionarily conserved peptides that inhibit the growth of bacteria, viruses, and fungi. HSV-2 infected keratinocytes were found to produce a number of antimicrobial peptides, but the most important one is called LL-37. This peptide enhanced the expression of HIV-1 receptors CD4 and CCR5 on LCs, leading to increased susceptibility of the cells to HIV-1. Removing LL-37 from the supernatant of HSV-2 infected cells reduces the ability of the medium to stimulate susceptibility to HIV-1.

These findings provide a plausible mechanism by which HIV-1 infection is enhanced by HSV-2. When HSV-2 infects the genital mucosa, the epithelial cells produce LL-37. This antimicrobial peptide enhances the production of CD4 and CCR5 on LCs, allowing more efficient infection by HIV-1. This mechanism is supported by the observation that elevated levels of LL-37 correlate with HIV-1 infection in sex workers.

I wonder why antimicrobial peptides up-regulate CD4 and CCR5. In addition to their antimicrobial properties, the cathelicidins possess chemotactic, immunostimulatory, and immunomodulatory effects, and the upregulation of CD4 and CCR5 are likely part of these activities.

These are exciting findings, and if they are further correlated in humans, they might lead to novel ways of interfering with HIV-1 infection, such as by antagonizing LL-37.

*CCR5 and CXCR4-tropic refer to HIV-1 virions that bind to chemokine receptors CCR5 or CXCR4, respectively, in addition to CD4, to initiate infection.

TWiV 219: Fauci pharmacy

Fauci PharmacyOn episode #219 of the science show This Week in Virology, Vincent and Rich meet up with Anthony S. Fauci, MD, Director of the National Institute of Allergy and Infectious Diseases.

You can find TWiV #219 at www.microbe.tv/twiv.

The AIDS pandemic

Origin of HIV

Any questions?