AIDSWEEKLY Plus, October 21, 1996
Daniel J. DeNoon, Senior Editor

Several workers have documented sudden dramatic increases in HIV levels following vaccination.

But three new studies show that not all vaccines stimulate HIV replication, and that the phenomenon is transient.

All three studies were presented at the American Society for Microbiology's 36th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), held September 15-18, 1996, in New Orleans, Louisiana.

N.P. Markowitz and colleagues of the Henry Ford Hospital, Detroit, Michigan, measured plasma HIV RNA at short intervals in 11 HIV(+) patients receiving influenza vaccination.

Prior to vaccination, the patients' median HIV RNA level was 36,000 copies/ml.

On days 2-6 after vaccination, their median HIV RNA level was 77,000 copies/ml (P=0.04); on days 7-13 it was 27,500 copies/ml (P=0.14); on days 14-30 it was 31,000 copies/ml (P=0.67; on days 61-90 it was 21,500 copies/ml (P=0.80); and on days 91-120 it was 33,500 copies/ml (P=0.62).

"Moreover, changes among individual patients were generally small," Markowitz et al. wrote in their presentation abstract. "Only two patients showed a rise of HIV RNA by more than 3-fold, and in both, the maximum value was found on a 2-6 day specimen."

There was no association between viral load increase after vaccination and CD4 count, pre-vaccination anti-influenza antibody titer, or post-vaccination anti-influenza antibody titer.

Incidentally, the researchers found that only half the patients had any antibody response to the influenza vaccine.

"Therefore, if influenza vaccination can activate HIV it may be inconsistent, of small magnitude, or occur transiently - perhaps during the first week after vaccination," Markowitz et al. concluded.

In a different study Frank P. Kroon of University Hospital, Leiden, Netherlands, and colleagues showed that adults immunized with three different bacterial vaccines did not have a significant increase in HIV viral load.

Kroon et al. enrolled 15 adults with HIV infection in their study. Five had CD4 counts of less than 100 cells/(micro)L, four had CD4 counts of 100-300 cells/(micro)L, and six had CD4 counts of more than 300 cells/(micro)L.

On day 0 the study participants received the experimental Merck pneumococcal conjugate; on day 60 they received the Pasteur Merieux polysaccharide vaccine against Salmonella typhi, and on day 180 they received the currently available MSD polysaccharide pneumococcal vaccine.

"There was no significant increase in either HIV-1 RNA or HIV-1 DNA after any of the three immunizations," Kroon reported. "On the basis of these data there are no arguments to withhold vaccination of HIV infected individuals when protection for certain infections is desirable.

"However, the published data on HIV-1 replication after vaccination are not equivocal, and concern remains. Since there is an enormous daily HIV-1 replication a temporary increase of HIV load due to stimulation by certain vaccinations might be insignificant and be outweighed by the benefits of these vaccinations."

In a third study, E.N. Janoff of the University of Minnesota, Minneapolis, and colleagues explored the impact of vaccination on viral burden in nine subjects with recent HIV infection.

All of the study participants were enrolled an average of 5.1 months after infection and had a mean CD4 count of 602 cells/(micro)L. Ten seronegative subjects served as controls.

All subjects received the Haemophilus influenzae type b (Hib)-diphtheria toxoid and pneumococcal polysaccharide vaccines. All had strong antibody responses to immunization.

"Despite these vigorous responses to both polysaccharides and proteins, markers of CD4(+) T-cell activation did not change over time," Janoff et al. wrote in their presentation abstract.

Mean viral load at baseline was 4.3 +/- 0.3 log[10] virions/mL at baseline and 4.5 +/-0.3 log[10] after vaccination.

"We conclude that recent HIV-1 seroconverters show vigorous humoral responses to vaccine antigens without evidence of appreciable T-cell activation and viral replication," Janoff et al. wrote. "Thus, use of these vaccines can be recommended early in HIV-1 infection."

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