So tell me, this physician of whom you were just speaking, Is he a money maker, an earner of fees, or a healer of the sick? Plato, The Republic

Molecular Biology of the Cell Alberts et al This allows T cells to recognize HIV infected cells, for example, and even internal proteins like reverse transcriptase can serve as antigens This formidable array of defense mechanisms Allows HIV to avoid being suppressed by our immune system Antigenic escape Inaccessible epitopes Downregulating MHC Destruction of CD4+ T cells Integration and latency

Molecular Biology of the Cell Alberts et al This allows T cells to recognize HIV infected cells, for example, and even internal proteins like reverse transcriptase can serve as antigens This formidable array of defense mechanisms Allows HIV to avoid being suppressed by our immune system Antigenic escape Inaccessible epitopes Downregulating MHC Destruction of CD4+ T cells Integration and latency How can we help the body fight back?

Molecular Biology of the Cell Alberts et al This allows T cells to recognize HIV infected cells, for example, and even internal proteins like reverse transcriptase can serve as antigens This formidable array of defense mechanisms Allows HIV to avoid being suppressed by our immune system Antigenic escape Inaccessible epitopes Downregulating MHC Destruction of CD4+ T cells Integration and latency How about an AIDS vaccine?

Let’s go back in time to see how this strategy works

The time: 500 B.C. The place: Greece

Even 2,500 Years Ago, People Knew Immunity Worked. Greek physicians noticed that people who survived smallpox never got it again. The insight: Becoming infected by certain diseases gives immunity.

Fast forward 2300 years pathmicro.med.sc.edu/ppt-vir/vaccine.ppt I had a brilliant idea

pathmicro.med.sc.edu/ppt-vir/vaccine.ppt He always takes all the credit!

Vaccination Charles Jenner 1796 : Cowpox/Swinepox 1800’s Compulsory childhood vaccination

Smallpox 1% v. 25% mortality Life-long immunity UK: 1700’s China 1950 Pakistan/Afghanistan/Ethiopia 1970 pathmicro.med.sc.edu/ppt-vir/vaccine.ppt Variolation was a huge advance

Smallpox pathmicro.med.sc.edu/ppt-vir/vaccine.ppt Smallpox presented many advantages that made this possible

Smallpox No animal reservoir Lifelong immunity Subclinical cases rare Infectivity does not precede overt symptoms One Variola serotype pathmicro.med.sc.edu/ppt-vir/vaccine.ppt Smallpox presented many advantages that made this possible

Smallpox As a result, after a world-wide effort Smallpox was eliminated as a human disease in 1978 pathmicro.med.sc.edu/ppt-vir/vaccine.ppt

Reported cases per population Inactivated (Salk) vaccine Oral vaccine Cases per 100,000 population United States Other vaccines have followed, making once feared diseases a thing of the past

How does vaccination work? A live or inactivated substance (e.g., protein, polysaccharide) derived from a pathogen (e.g bacteria or virus) capable of producing an immune response Expose the patient to an Antigen

A live or inactivated substance (e.g., protein, polysaccharide) derived from a pathogen (e.g bacteria or virus)capable of producing an immune response Expose the patient to an Antigen If the patient is subsequently exposed to virus carrying this Antigen they will mount a faster immune response How does vaccination work?

Molecular Biology of the Cell Alberts et al Patient exposed to pathogen Carrying antigens A and B It works like this

Or in more detail….

Vaccines can be divided into two types Live attenuated Inactivated

Inactivated Vaccines fall into different categories viruses bacteria Individual proteins from pathogen Pathogen specific complex sugars Whole Fractional

Live Attenuated Vaccines have several advantages Attenuated (weakened) form of the "wild" virus or bacterium Can replicate themselves so the immune response is more similar to natural infection Usually effective with one dose

Live Attenuated Vaccines also have several disadvantages Severe reactions possible especially in immune compromised patients Worry about recreating a wild-type pathogen that can cause disease Fragile – must be stored carefully MMWR, CDC

A number of the vaccines you received were live Attenuated Vaccines Viral measles, mumps, rubella, vaccinia, varicella/zoster, yellow fever, rotavirus, intranasal influenza, oral polio BacterialBCG (TB), oral typhoid

Inactivated Vaccines are the other option No chance of recreating live pathogen Less interference from circulating antibody than live vaccines Pluses

Inactivated Vaccines are the other option Cannot replicate and thus generally not as effective as live vaccines Usually require 3-5 doses Immune response mostly antibody based Minuses

Inactivated Vaccines are also a common approach today Viral polio, hepatitis A, rabies, influenza* Bacterialpertussis*, typhoid* cholera*, plague* Whole-cell vaccines *not used in the United States

Other Inactivated Vaccines now contain purified proteins rather than whole bacteria/viruses Proteinshepatitis B, influenza, acellular pertussis, human papillomavirus, anthrax, Lyme Toxinsdiphtheria, tetanus

Polio Vaccine illustrates the pluses and minuses of live vaccines pathmicro.med.sc.edu/ppt-vir/vaccine.ppt

Sabin Polio Vaccine Attenuated by passage in foreign host (monkey kidney cells) Selection to grow in new host makes virus less suited to original host

Sabin Polio Vaccine Attenuated by passage in foreign host (monkey kidney cells) Selection to grow in new host makes virus less suited to original host Grows in epithelial cells Does not grow in nerves No paralysis Local gut immunity (IgA)

Salk Polio Vaccine Formaldehyde-fixed No reversion

US: Sabin attenuated vaccine ~ 10 cases vaccine-associated polio per year = 1 in 4,000,000 vaccine infections Polio Vaccine illustrates the pluses and minuses of live vaccines pathmicro.med.sc.edu/ppt-vir/vaccine.ppt

US: Sabin attenuated vaccine ~ 10 cases vaccine-associated polio per year = 1 in 4,000,000 vaccine infections Scandinavia: Salk dead vaccine No gut immunity Cannot wipe out wt virus Polio Vaccine illustrates the pluses and minuses of live vaccines pathmicro.med.sc.edu/ppt-vir/vaccine.ppt

Reciprocal virus antibody titer Serum IgG Serum IgM Nasal and duodenal IgA Nasal IgA Serum IgA Duodenal IgA Days Vaccination Killed (Salk) Vaccine Live (Sabin) Vaccine Live virus generates a more complete immune response

Modern molecular biology has offered new approaches to make vaccines

1.Clone gene from virus or bacteria and express this protein antigen in yeast, bacteria or mammalian cells in culture

Modern molecular biology has offered new approaches to make vaccines 2. Clone gene from virus or bacteria Into genome of another virus (adenovirus, canary pox, vaccinia) And use this live virus as vaccine

Cloned protein antigens have pluses and minuses Pluses Easily manufactured and often relatively stable Cannot “revert” to recreate pathogen Minuses Poorly immunogenic Post-translational modifications Poor CTL response

Viral vectors have pluses and minuses Pluses Infects human cells but some do not replicate Better presentation of antigen Generate T cell response Minuses Can cause bad reactions Can be problems with pre-exisiting immunity to virus Often can only accommodate one or two antigens

Given that introduction, should we search for a vaccine against HIV and how would we do so?

An effective vaccine could have a MAJOR Impact on the future prognosis iavi.org

This allows T cells to recognize HIV infected cells, for example, and even internal proteins like reverse transcriptase can serve as antigens An effective vaccine must get around the strategies HIV uses to evade the immune system

This allows T cells to recognize HIV infected cells, for example, and even internal proteins like reverse transcriptase can serve as antigens The vaccine must be able to target conserved and essential parts of the viruses machinery Antigenic escape Inaccessible epitopes + existence of many viral strains

Molecular Biology of the Cell Alberts et al This allows T cells to recognize HIV infected cells, for example, and even internal proteins like reverse transcriptase can serve as antigens The vaccine must act early in the process Before the virus becomes firmly established And destroys the immune system Destruction of CD4+ T cells Integration and latency

There are many possible HIV Vaccine Approaches Protein subunit Synthetic peptide Naked DNA Inactivated Virus Live-attenuated Virus Live-vectored Vaccine Ramil Sapinoro, University of Rochester Medical Center

To begin we need to ask some key questions What should vaccine elicit?

To begin we need to ask some key questions What should vaccine elicit? Neutralizing antibodies to kill free virus

To begin we need to ask some key questions What should vaccine elicit? Neutralizing antibodies to kill free virus T cell response to kill infected cells OR

To begin we need to ask some key questions What should vaccine elicit? Neutralizing antibodies to kill free virus T cell response to kill infected cells OR OR BOTH?

The biology of HIV provides some clues

Remember the long term progressors Infected with a Nef mutant virus?

This would generate both an antibody and a T cell response Could this be used to generate a vaccine?

This prompted an experiment that demonstrated the feasibility of a vaccine

December 1992: Live attenuated SIV vaccine Lacking the gene Nef protected all monkeys for 2 years against massive dose of virus All controls died cell mediated immunity was key

This prompted an experiment that demonstrated the feasibility of a vaccine December 1992: Live attenuated SIV vaccine Lacking the gene Nef protected all monkeys for 2 years against massive dose of virus All controls died cell mediated immunity was key I don’t know about you but I was pretty happy about that!

However, this approach is still viewed as too risky to try on human subjects December 1992: Live attenuated SIV vaccine Lacking the gene Nef protected all monkeys for 2 years against massive dose of virus All controls died cell mediated immunity was key

The next efforts attempted to use recombinant viral proteins as antigens in an effort to generate neutralizing antibodies

VaxGen made two different forms of gp120 from different HIV strains and began human trials after chimp testing

Human vaccine trials are large and very expensive

The trial was a failure, with only minor effects seen that were viewed as statistically insignificant NY Times

The next approach involved using viral vectors to try to also boost the T cell response

Many different viral vectors are being investigated but this trial used the human cold virus called adenovirus

They actually used three adenoviruses carrying three different viral proteins Gag Pol Nef

Early results suggested the immune system was being stimulated

The hotly awaited results were released at the 2007 AIDS Meeting

You be the judge—what happened?

This stunning failure led to a re-thinking of the approach

The field has decided in part to go back to the basics: how does HIV work and how can we assess vaccine success? Questions: For a vaccine what are the measures of protection? Can we overcome polymorphism? What are the key antigens? Attenuated or killed or neither? Is Mucosal immunity critical? Should it Prevent infection or prevent disease? What are the best Animal models How does HIV kill cells anyway?

However trials continue, but with more focus on the details of how they affect immunity